Agro2Circular Energy and Water Recommendations

D1.7 – Energy and Water Recommendations November 2023 Authors: Victor Fabregat (REG); Clara Navarro (REG); Juana María Pagán Carpe (REG); David Campos Peñalver (REG); Janneke Dickhout (CEW); Jordi Moreno (CEW); Ref. Ares(2023)8029246 - 24/11/2023 2 A2C – Deliverable D1.7 v2.0 Technical references Project Acronym Agro2Circular Project Title TERRITORIAL CIRCULAR SYSTEMIC SOLUTION FOR THE UPCYCLING OF RESIDUES FROM THE AGRIFOOD SECTOR Project Coordinator Fuensanta Monzó CETEC [email protected] Project Duration October 2021 – September 2024 (36 months) Deliverable No. D1.7 Dissemination level* PU Work Package WP 1 – A2C Specifications, Residues Management and Data Integration System Task T1.3 – A2C water and energy efficiency assurance Lead beneficiary 11 (REG) Contributing beneficiary/ies 10 (WETS), 12 (CEW) Due date of deliverable 31th December 2021 Actual submission date 31th December 2021 * PU = Public PP = Restricted to other programme participants (including the Commission Services) RE = Restricted to a group specified by the consortium (including the Commission Services) CO = Confidential, only for members of the consortium (including the Commission Services) 3 A2C – Deliverable D1.7 v2.0 Document history V Date Comments v0.1 21/12/2021 First draft of document v0.2 22/12/2021 Revised version based on the comments CETEC v1.0 28/12/2021 First final version, approved by the project coordinator, (will be) submitted to EC. v1.1 23/11/2023 Revised version based on the REPA1 comments from the Project Officer v2.0 24/11/2023 Reviewed final version, approved by the project coordinator, (will be) submitted to EC. 4 A2C – Deliverable D1.7 v2.0 Document Distribution Log Version Date Distributed to v0.1 21/12/2021 CETEC and CTNC for peer review V1.1 23/11/2023 Coordinator Verification and approval Name Date Verification Final Draft by WP leader Jaime Ortíz (CETEC) 24/11/23 Approval Final Deliverable by coordinator Fuensanta Monzó (CETEC) 24/11/23 Disclaimer and acknowledgement This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement. No 101036838 Disclaimer This document reflects only the views of the author(s) the European Research Executive Agency (REA) is not responsible for any use that may be made of the information it contains. Whilst efforts have been made to ensure the accuracy and completeness of this document, the A2C consortium shall not be liable for any errors or omissions, however caused. 5 A2C – Deliverable D1.7 v2.0 Table of contents Technical references ........................................................................ 2 Table of contents .............................................................................. 5 List of Tables .................................................................................................................. 6 List of Figures ................................................................................................................ 6 List of abbreviations .......................................................................... 8 Glossary ............................................................................................ 9 Executive summary ........................................................................ 12 1 Introduction ................................................................................ 14 1.1 Objectives and scope of the deliverable ......................................................... 16 1.2 Link with other activities ................................................................................... 16 1.3 Methodology ...................................................................................................... 19 2 Energy recommendations .......................................................... 21 2.1 Energy optimisation .......................................................................................... 22 2.2 Energy Efficiency (EE) ...................................................................................... 23 2.2.1 Introduction to Energy Efficiency .................................................................. 23 2.2.2 Energy efficiency in the agricultural sector ................................................... 28 2.2.3 Processes involved in the A2C project ......................................................... 31 2.2.4 General recommendations ........................................................................... 33 2.3 Renewable energies .......................................................................................... 48 2.3.1 Energy generation from renewable sources ................................................. 48 2.3.2 Renewable energies in the agricultural sector .............................................. 55 2.3.3 A2C processes implementation .................................................................... 57 3 Water recommendations ............................................................ 65 6 A2C – Deliverable D1.7 v2.0 3.1 Water issues related to agriculture .................................................................. 65 3.2 Water in the circular economy ......................................................................... 66 3.3 Description of Agro2Circular processes ......................................................... 68 3.3.1 Process descriptions: Agrifood wastes treatment ......................................... 69 3.3.2 Process descriptions: Multilayer plastic waste treatment ............................. 69 3.4 Recommendations ............................................................................................ 70 3.4.1 Methodology ................................................................................................. 70 3.4.2 Available treatment technologies .................................................................. 72 3.4.3 Preliminary recommendations ...................................................................... 81 4 Conclusions ............................................................................... 83 5 References ................................................................................ 85 List of Tables Table 1. Typical excess air to achieve the highest efficiency. Source: [28]........................ 37 Table 2. Renewable Energy Indicators 2020. Source: [15] ................................................ 50 Table 3. Pros and cons of renewable sources. .................................................................. 64 List of Figures Figure 1. Deliverable’s structure ........................................................................................ 14 Figure 2. Average annual precipitations in Spanish provinces’ capitals. Source: [13] ....... 15 Figure 3. Use of EE recommendations in A2C project. ...................................................... 18 Figure 4. Use of water recommendations in A2C project. .................................................. 19 Figure 5. Global GHG emissions by sector. Source: [16]................................................... 21 Figure 6. Guide for optimization of energy consumption. ................................................... 23 Figure 7. Transformation of energy to its final use. ............................................................ 25 Figure 8. Transformation and use of energy in an industrial plant. .................................... 27 7 A2C – Deliverable D1.7 v2.0 Figure 9. Final energy consumption by sector in the European Union. Data of 2019. Source: [19] .............................................................................................................................. 28 Figure 10. Energy consumption in agri-food systems, by region, 2000-2018. Source: [20] .................................................................................................................................... 29 Figure 11. Agriculture development. Source: [23] .............................................................. 30 Figure 12. Relationship between excess air and increased efficiency. Source: [28] .......... 36 Figure 13. IE classification by the IEC 60034-30-1, 2014. ................................................. 46 Figure 14. Photovoltaic installation costs as a function of time. Source: [52] ..................... 58 Figure 15. Wind onshore installation costs as a function of time. Source: [52] .................. 59 Figure 16. Wind offshore installation costs as a function of time. Source: [52] .................. 59 Figure 17. Biomass installation costs as a function of time. Source: [52] .......................... 60 Figure 18. Solar thermal installation costs as a function of time. Source: [52] ................... 61 Figure 19. A schematic representation of flocculation and sedimentation. Source: [65] .... 73 Figure 20. A schematic representation of the process of coagulation. Source: [66] .......... 74 Figure 21. A schematic representation of the flows in a hydrocyclone. Source: [72] ......... 75 Figure 22. An overview of particles rejected by different classes of membranes. Source: [67] .................................................................................................................................... 76 Figure 23. An overview of rejected substances by different membrane classes. Source: [68] .................................................................................................................................... 77 Figure 24. A schematic overview of an electrodialysis stack, showing the movement of ions over the membranes and the half-reactions at the electrodes. Source: [69] ............... 78 Figure 25. Schematic representation of membrane distillation. Source: [70] .................... 79 8 A2C – Deliverable D1.7 v2.0 List of abbreviations A2C: Agro2Circular CM: Condition Monitoring CTNC: Centro Tecnológico Nacional de la Conserva EAE: Enzymatic hydrolysis Assisted Extraction EC: European Commission EE: Energy Efficiency GHG: Greenhouse Gas LCA: Life Cycle Assessment MAE: Microwaves Assisted Extraction PV: Photovoltaic PVS: Photovoltaic System RES: Renewable Energy Systems TRL: Technology Readiness Level WWTP: Wastewater Treatment Plants 9 A2C – Deliverable D1.7 v2.0 Glossary Even though some of the terms included in this glossary can be general and considered of common knowledge by technicians or experts in the energy field, they may be unknown or vague to the general public. As this is a public deliverable, it is considered that offering a set of terms that help understand the information explained throughout the deliverable can be of general interest. Energy Energy means all forms of energy products, combustible fuels, heat, renewable energy, electricity, or any other form of energy [1]. Work Defined as the change in the state of motion of a body due to the action of a force. In the case of mechanical work, it corresponds to the action of a force that generates a change in position, the work being the resultant of the product of the force and the distance travelled [2]. Power It corresponds to the flow of energy per unit of time, the amount of work that can be done per unit of time. It can also be understood as a rate of consumption, release or generation of energy [2]. Energy Efficiency Energy Efficiency means using less energy to perform the same task through behaviour change or energy-saving technologies. Many benefits are associated with energy efficiency, including a reduction in greenhouse gas (GHG) emissions, reduced demand for imported energy, and lower energy costs [3]. Energy efficiency is measured as the amount of energy output for a given energy input and listed as a percentage between 0% and 100%, for example the amount of mechanical energy that an electric motor produces for a given input of electrical energy [4]. 16 A2C – Deliverable D1.7 v2.0 1.1 Objectives and scope of the deliverable The A2C project aims to upgrade the value chain in the agriculture sector by revaluing plastic and organic wastes such as plastic barriers, multilayer food packaging and organic residues (fruits and vegetables as grapes, citrus, broccoli, etc.). Although this revaluation process will allow the circularity in the agriculture sector reducing the waste generated with the positive impact on the environment, some energy and water consuming equipment have to be used with their corresponding carbon and water footprint. In order to mitigate this issue, T1.3 aims to assess the energy and water consumption of the new processes in order to identify and select the best practices and technologies that will allow the best energy and water efficiency performance. A description of the best energy practices and technologies on the agricultural sector is not the goal of this deliverable, but rather the application of these on the processes proposed during A2C project, aiming to reduce the impact of this sector on the environment. However, a superficial approach on these matters applied to the agricultural sector will be offered. Therefore, the purpose of this deliverable is the realisation of a set of recommendations to be used by A2C partners. These recommendations will focus on energy efficiency (use of renewable energy technologies and energy key parameters optimization) and sustainable water & wastewater management (preliminary water demand, water quality criteria and wastewater characteristics) for the A2C processes and technologies to ensure that these transformations become sustainable processes with the lowest environmental impact. To this end, it is essential that all processes reuse as much water as possible, use as low energy as possible and that the energy they use comes from renewable sources. 1.2 Link with other activities WP1 aims to achieve the definition of the specifications and strategies for the preparation of the new products and recycled materials of A2C project, as well as the definition of the residues management and Data Integration System. The specific objectives of WP1 are (i) to define the specifications of the new products along the value chain, (ii) to establish 17 A2C – Deliverable D1.7 v2.0 strategies for compliance assessment with standards and prepare the recycled materials food contact approval, (iii) to define recommendations on water and energy for the new technologies and processes, (iv) to perform a management plan for the different residues, (v) to characterise the residues, and (vi) to develop the A2C Data Integration System-DIS. The present deliverable is clearly aligned with objective (iii), being the first report to set up the concept of efficiency in energy and water management in the form of recommendations. The outputs of Deliverable 1.7 will be the starting point for the implementation of water and energy efficient management in the A2C project: In energy efficiency: Deliverable 1.7 will be one of the inputs for deliverable 1.8 (D1.8. – Energy Management Plan (Draft), M12) and deliverable 1.9 (D1.9 – Energy Management Plan (Final), M24) also corresponding to task 3 of WP1. The scope of both deliverables is the analysis of the energy requirements of the A2C technologies and processes including time of use, life cycle and load, aiming to optimise the key parameters to reach the maximum energy savings. Moreover, the combined outputs of D1.7, D1.8 and D1.9, will serve as the basis for the energy performance in A2C demonstrators which will be carried out in Task 6.2 (T6.2 – A2C demonstrators, WP6 – Demonstration of the A2C technological solution) by means of studying energy consumption analysis, electrical parameters, loads and renewable energies integration in order to recommend the most efficient industrial solutions, which will be reported in deliverable 6.3. (D6.3 – A2C Demonstrators of the technologies and prototypes of the valorised products at relevant scale and industrial relevant environment to demonstrate A2C solution at TRL6-7, including energy performance (M33)). 18 A2C – Deliverable D1.7 v2.0 Figure 3. Use of EE recommendations in A2C project. In sustainable water & wastewater management: Regarding the water management recommendations, deliverable 1.7 will be an input for WP3, WP5 and WP6. In task 3.1 (Plastic waste pretreatments and preliminary decontamination), the information and data collected in this deliverable will be used to design a water treatment system. In tasks 3.3 (Physical recycling of complex multilayers containing aluminium), 3.4 (Enzymatic recycling of multilayer structures based on PE/PET) and 3.5 (Mechanical recycling of simple multilayer structures and products from physical recycling) the water management recommendations can be included in designing and upscaling the processes on a pilot scale. In task 5.1 (Upcycling of products (TPA, EG, alkanes) obtained from the enzymatic degradation), the recommendations will be used as a basis for the recovery of water and salt from the production of PHBV and carotenoids. The information from deliverable 1.7, through the results acquired from WP3 and WP5, will be integrated in the A2C demonstrators’ site of WP6. 19 A2C – Deliverable D1.7 v2.0 Figure 4. Use of water recommendations in A2C project. 1.3 Methodology The methodology of the deliverable includes the following main activities: ● A description of renewable energy sources and energy efficiency strategies that can be applied in agriculture to reduce the activity’s impact on the environment. ● Identification of the characteristics of A2C processes and technologies within the scope of water and energy. ● A comprehensive literature review of generic energy efficiency strategies at industrial level, taking into account the specific A2C processes and technologies. ● The identification and description of the most suitable renewable energy sources to promote the energy efficiency of the A2C project processes and technologies. ● Description of promising water treatment technologies, focused on delivering clean water and recovering resources Deliverable D1.7 has been developed at the beginning of the A2C project with the purpose of being used as a research document for the energy and water efficiency works that will be 20 A2C – Deliverable D1.7 v2.0 done during the project. The tasks and deliverables that will be fed with the information of D1.7 have been indicated in Figure 3 and Figure 4. Furthermore, it is worth mentioning that collection of some energy and water consumption data from the demonstrators, which will complement this deliverable, will be done in common with Task 7.3 Environmental assessment, LCA and A2C circularity monitoring, which will be documented in D7.6 Environmental assessment, LCA and A2C circularity monitoring (Draft) and D7.7 Environmental assessment, LCA and A2C circularity monitoring, as T1.3 and T7.3 have some inputs in common. Thus, the works for T1.3 and T7.3 need to be aligned. 21 A2C – Deliverable D1.7 v2.0 2 Energy recommendations Renewable energy and energy efficiency have long been known to provide multiple benefits to society, such as lowering energy costs, improving air quality and public health, and boosting jobs and economic growth. Increasingly, renewables and efficiency are viewed as crucial to reduce carbon emissions. Energy production and use account for more than two-thirds of global Greenhouse Gas emissions (GHG emissions). Together, renewables sources and energy efficiency have made significant contributions to limiting the rise in CO2 emissions [15]. Figure 5. Global GHG emissions by sector. Source: [16] Together, renewables and energy efficiency have made significant contributions to limiting the rise in CO2 emissions. 22 A2C – Deliverable D1.7 v2.0 2.1 Energy optimisation Achieving optimal energy efficiency in a process is a multifaceted endeavour that involves strategic considerations at various stages. The process begins with meticulous design optimization aimed at eliminating superfluous steps and ensuring a streamlined workflow. By scrutinizing the entire process, process designers can identify and eliminate unnecessary stages, thereby reducing energy consumption from the outset. A significant aspect of energy optimization lies in reducing overall energy demand. This can be accomplished through the enhancement of energy efficiency in the equipment employed throughout the process. Upgrading technologies, fine-tuning operational parameters, and adopting state-of-the-art, energy-efficient machinery contribute to a substantial reduction in energy requirements. This not only results in cost savings but also aligns with sustainability goals by lessening the overall environmental impact. Another integral strategy involves the reutilization of energy. Rather than considering energy losses as inevitable, forward-thinking designs harness these losses to power other stages or processes within the system. This approach, known as energy reuse or cogeneration, maximizes the utility of energy within the processes. By capturing and repurposing energy that would otherwise be wasted, this method significantly improves overall efficiency and resource utilization. Furthermore, once completed all of the previous strategies, the incorporation of renewable energies, such as solar, wind, or hydropower, helps with the reduction of reliance on fossil fuels and also mitigates the environmental impacts of the processes. The following schema summarizes the steps to be follow to optimize the energy consumption of processes: 23 A2C – Deliverable D1.7 v2.0 Figure 6. Guide for optimization of energy consumption. 2.2 Energy Efficiency (EE) 2.2.1 Introduction to Energy Efficiency The integration of thermodynamic principles, sustainability considerations and a deep understanding of energy concepts is essential when designing new processes. A commitment to energy efficiency not only aligns with environmental responsibility but also ensures economic viability and social well-being. As we chart the course for future innovations, a holistic and principled approach will be the catalyst for sustainable progress. 2.2.1.1 Energy principles In the realm of engineering and process design, adherence to the laws of thermodynamics is the cornerstone of achieving optimal efficiency and performance. These fundamental principles govern energy transfer and conversion, providing invaluable insights into the behaviour of systems. By understanding and applying the laws of thermodynamics, engineers can navigate the complexities of energy transformation, ensuring that processes are not only effective but also sustainable. Energy is defined as the capacity to execute external actions, to generate changes or to initiate a movement. In physics it is the ability to do "work". The concept of energy is closely linked to the concept of motion (or change). Energy can manifest itself in different forms and do different kinds of work. Among other distinctions we have: chemical energy, thermal energy, mechanical energy, internal energy, electromagnetic energy, electrical energy and nuclear energy [2]. 24 A2C – Deliverable D1.7 v2.0 Energy must obey the two laws of thermodynamics: ● The first law of thermodynamics Energy cannot be created or destroyed (which is called the conservation of energy); however, it can be transformed from one type into another. In fact, every useful process transforms energy from one form to another. There are many different forms or types of energy. ● The second law of thermodynamics The Second Law of Thermodynamics sets out the specific idea that heat cannot be converted entirely to mechanical energy, as previously mentioned [17]. 2.2.1.2 Social, economic and environmental sustainability The importance of social, economic, and environmental sustainability cannot be overstated in today's interconnected world. As we strive for progress, it is imperative to consider the broader impact of our actions. Adhering to sustainability principles ensures that advancements do not come at the expense of social well-being, economic stability, or environmental health. It is a holistic approach that recognises the interdependence of these factors, acknowledging that true progress must be inclusive and enduring. Energy, as a resource, must contribute to the three pillars of sustainability: ● Social sustainability: Energy provides social wellbeing because it offers us services of great value: comfort, mobility, etc. For this reason, access to energy must be guaranteed for the entire population in conditions of quality, safety and competitiveness. ● Economic sustainability: Energy is present in all economic activity, is a determining factor in business competitiveness and must in itself generate economic activity (companies in the energy sector). ● Environmental sustainability: Energy generation and consumption processes must be environmentally friendly in order to ensure its conservation [18]. 25 A2C – Deliverable D1.7 v2.0 2.2.1.3 Primary energy vs. Final energy When designing a new process, a clear grasp of concepts such as primary and final energy is paramount. Primary energy represents the raw, unconverted forms of energy, while final energy is the refined and usable output. Efficient processes minimise the gap between primary and final energy, maximising the utility of resources. This not only optimises energy usage but also contributes to economic efficiency by reducing waste. Furthermore, understanding thermal energy and specific consumption is crucial for designing processes that harness energy effectively. Thermal energy, a key player in many industrial processes, requires meticulous management to prevent losses and inefficiencies. Specific consumption metrics provide a quantitative measure of efficiency, allowing engineers to fine-tune processes for optimal performance. Energy comes in different forms and can be transformed into different types of energy for better use. ● Primary energies: chemical energy (coal, oil, natural gas), nuclear energy (uranium), solar energy (solar thermal, photovoltaic, wind) and gravitational energy (hydro, tidal). ● Final energies (energy vectors): electrical energy, gasoline, diesel, propane, natural gas. Figure 7. Transformation of energy to its final use. 32 A2C – Deliverable D1.7 v2.0 ● Optical sorting of the multilayers by a synergistic combination of technologies. ● Physical separation of the Aluminium from the multilayers based on SAPE patented delamination technology. ● Enzymatic depolymerisation of the PE/PET multilayers by a synergic strategy of customisation of enzymes and plastic wastes pre-treatments. ● Plastics decontamination for the reintroduction of the recycled plastics into the agrifood value chain (packaging and agricultural films) by 3 step process of washing, micro/nanoplastics separation and vacuum extrusion. ● Aluminium purification and treatment for reuse. Aluminium from the physical separation will be chemically modified. ● The simple multilayers and the plastic mono-materials obtained from the physical recycling will be formulated for their application in food packaging and agricultural films. iv) Upcycling of the recycled plastics coming from agriculture and post-industrial packaging to obtain high added value materials. ● Upcycling of enzymatic degradation products (alkanes, TPA, EG) by biotransformation to obtain high added value building blocks for cosmetics. ● PHBV bioplastics and carotenoids production by cell factory: The by-products of the previous cell factories in combination with organic waste from the agrifood industry will be used as nutrients. ● Development of plastic compounds for food packaging and agriculture: - Development of recyclable high barrier PE plastic compounds as an alternative to current non-recyclable multilayers. - Development of PHBV bioplastics compounds. The neat PHBV range obtained will be formulated and compounded for their application in flexible food packaging and agricultural films development. 33 A2C – Deliverable D1.7 v2.0 2.2.4 General recommendations As mentioned before, the objective of the energy efficiency is about minimising energy consumption achieving the same desired aim. The actions that contribute to highly energyefficient processes are detailed below: 2.2.4.1 Energy demand reduction These actions are focused on the design or redesign of systems and processes, both physical and operational. The aim of this section is to put on record the importance of decisions in planning and operating production systems in energy efficiency. Planning a production system starts with the definition of production processes and the selection of available technologies. Defining each process step imposes technological limitations on succeeding steps. In order to design energy efficient systems, besides each single process step, the consumption of the whole process chain has to be taken into account. In addition, exploiting energy regeneration and recovery cycles requires a detailed understanding of the consumption behaviour of the involved processes. After selecting processes and technologies, appropriate equipment and the layout of the planned system are determined in an iterative process of defining, evaluating and selecting alternative designs. Here, energy efficiency objectives such as minimising total consumption or energy recovery have to be integrated into the evaluation and decision processes. Scheduling assigns products and processes to available production equipment and influences the energy consumption behaviour of the whole system. By integrating energy efficiency criteria into scheduling, a reduction of energy costs is to be expected. Such criteria and metrics are for instance peak demand shifting, adapting the production programme to external conditions such as energy prices or renewable energy availability and automatically turning equipment off when stand-by time thresholds are reached and scheduling constraints are fulfilled. A prerequisite for the integration of energy efficiency criteria in planning activities is a detailed prediction of the energy consumption. This prediction has to be carried out on a machine level, i.e., the energy consumption of each machine and product 34 A2C – Deliverable D1.7 v2.0 has to be calculated. Moreover, approaches such as load levelling and peak shaving require high time domain resolution of energy consumption; the different operating states of the machines have to be taken into account. In such ways, system-wide consumption and cost estimations as well as comparison of alternative equipment during system design, can be based on analytical models. Aggregating the predicted consumptions for different levels of a factory’s organisational structure allows for a centralised energy management [24]. 2.2.4.2 Maintenance and control A maintenance plan, apart from benefiting operational continuity, service standards and productivity, has a decisive impact on the energy consumption. Controlling the energy consumption of different equipment and systems should also be part of routine maintenance tasks. As irrespective of the area of business and supplied product, each process has technical resources (machines, equipment) that require maintenance in operation. By maintaining we wish them to perform the tasks ordered by the user efficiently, i.e. with the optimum use of resources (materials, energy, etc.) [25]. Many basic tasks of minor complexity and low implementation cost can have a great impact on energy efficiency, generating large reductions in energy consumption, such as: ● Cleaning routines: evaporative condensers, filters of thermal conditioning systems, steam generators, exchangers, etc. ● Inspection and repair routines for fluid leaks: compressed air, water, compressed gases, steam, etc. ● Routines for inspection and repair of insulation. ● Inspection and repair routines for steam traps. ● Water treatment for steam generators, evaporative condensers and cooling towers. 35 A2C – Deliverable D1.7 v2.0 Within a maintenance plan, monitoring tasks of different conditions and/or operating parameters of the machines and installations must be foreseen in order to be able to detect when there is a deviation. In these terms, the concept of Condition Monitoring (CM) arises to facilitate predictive maintenance works. CM is a process consisting of monitoring parameters of condition in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of the initial stage of a failure. In this sense, CM can be used to monitor the performance of equipment by measuring and tracking certain physical parameters in order to anticipate failure: ● Monitoring the dynamic conditions of the machinery: vibrations. ● Temperature Monitoring. ● Infrared Thermography Inspection. ● Measurement of equipment performance: - Pressure - Flow rate - Power output - Power consumption - Fuel consumption The major benefit is to achieve an early warning in order to schedule a corrective intervention in order to minimise the consequences, i.e., overconsumption of energy. Many failures with wear related failure modes will also cause an increase in energy consumption during the initial stages. By implementing condition monitoring techniques to detect failures in their early stage, you will also contribute to the care of energy efficiency. The effectiveness and quality of the corrective action is essential to avoid including elements that cause additional failures after the repair, thus further decreasing reliability and energy efficiency [26]. 36 A2C – Deliverable D1.7 v2.0 2.2.4.3 Incorporation of efficient technologies One of the basic measures that achieves significant energy savings in any process is, in one hand, the incorporation of efficient technologies that meet production needs while reducing energy consumption and make it possible to take advantage of existing and free energy resources and/or wasted energy resources and, in the other hand, the automation of the systems to modulate capacity and minimise uptime. 2.2.4.3.1 Thermal installations: boilers, ovens, dryers, etc. 2.2.4.3.1.1 Control of combustion The control of combustion is a basic measure in any heat generator using fossil fuel. The control of the combustion that is produced inside the burners aims to release as much energy as possible from the fuel, causing complete combustion with adequate excess air, and therefore minimising the amount of energy lost in the combustion fumes. One of the most decisive factors for good combustion is the excess air. It is calculated theoretically and then increased by a factor that marks the good practice of this equipment and depends on the type of fuel. This excess must be controlled, because as it increases, and once complete combustion has been achieved, its increase will only lead to increasing energy losses through the gases expelled [27]. Figure 12. Relationship between excess air and increased efficiency. Source: [28] 37 A2C – Deliverable D1.7 v2.0 To implement this measure, the burner and the primary and secondary air fans must be adjusted in order to obtain the lowest possible loss of unburned fuel. Once these parameters have been calculated, combustion control must be carried out by analysing the combustion gases at certain intervals in order to achieve the desired gas concentration. To carry out the analysis of this combustion, fixed or mobile gas analysers are installed, depending on whether it is measured continuously or with a certain frequency (which will depend on the power of the equipment), at the combustion fume outlet. Once the percentage of oxygen content in the fumes has been obtained, the amount of air and fuel entering the combustion is regulated. In addition, a carbon monoxide (CO) analyser can also be installed, as the presence of CO is an indication of incomplete combustion The implementation of a controller is usually the most optimal solution to continuously regulate and control the fuel and air input to the combustion. This equipment receives the signal from the analyser and, depending on the difference between this signal and the reference signal calculated based on the boiler load, acts on the air regulation. The excess air to achieve the highest energy efficiency in typical fuels are [27]: FUEL MINIMUM % MAXIMUM % Natural gas 5 10 Fuel oil 5 20 Coal 15 60 Table 1. Typical excess air to achieve the highest efficiency. Source: [28] 2.2.4.3.1.2 Steam boiler blowdown minimisation Steam generation boiler blowdowns are carried out with the aim of eliminating the solids or salts that are generated when the water evaporates, which were previously dissolved in it. These solids accumulate and make it necessary to use more energy to heat the water, as they are deposited on the walls, which reduces the contact between the surfaces and therefore the heat transfer. In addition to the higher energy consumption, if the solids are not purged, they will end up encrusted on the surfaces and corrode the equipment. 38 A2C – Deliverable D1.7 v2.0 By blowdown, the water contained in the boiler is discharged and replaced with feed water so the blowdown should be kept to the minimum necessary, as any excess, in addition to increasing water consumption, represents an energy and economic loss as the feed water must be heated, treated and pumped. Excess boiler blowdown, in addition to increasing energy consumption, can lead to drainage. The optimum amount of blowdown is determined by several factors such as boiler type, operating pressure, water treatment and feed water quality. To achieve the lowest losses due to blowdown, the blowdown flow rate should be reduced to the optimum amount. 2.2.4.3.1.3 Waste heat recovery from flue gas Boiler economiser: Feedwater preheating An economiser is a finned tube heat exchanger, which recovers part of the sensible heat from the combustion products emitted by a boiler and transfers it to the feed water, thus increasing thermal efficiency [29]. Boiler heat recovery system: Preheating of combustion air. In this case, the combustion air is heated with the combustion gases before it enters the generation equipment, thus reducing fuel consumption. By means of the recuperator, the performance of the equipment will be significantly improved. Most furnaces produce fumes at high temperatures (250 – 1.000 ºC) and there is a great potential for energy recovery and reuse in the process, reducing fuel consumption for the same power to be transferred. A boiler water economiser is more economical than an air preheater for small boilers, i.e., low pressure boilers and with a steam production of less than 20.000 kg/h. The air preheater will compete with the water economiser for larger capacity and output units [27]. 39 A2C – Deliverable D1.7 v2.0 2.2.4.3.1.4 Minimising wall losses It is interesting to know that the boiler loses heat through radiation and convection, even when the burner is not in operation, simply because the boiler, valves and piping, house steam at every moment and therefore they transfer heat to their surroundings [30]. To minimise wall losses, the walls are covered with highly insulating materials such as mineral wool. In spite of this, due to the large temperature differences between the inside of the boiler and the outside environment, losses due to this problem can be as high as 3% in some cases. In addition to including a good insulation, it is necessary to maintain it in good condition over the years, as a deteriorated or damp insulation does not function as an insulator, but quite the opposite. 2.2.4.3.2 Steam generation and transmission facilities 2.2.4.3.2.1 Condensate and steam lines insulation As mentioned in the previous section, there is a large temperature difference between the steam generated and the outside ambient temperature, so there will be energy losses in the form of heat. During the distribution of the steam from the boiler to the consumption and return points, there is a large surface area of pipes that are at different temperatures with respect to the ambient temperature, so that if they are not insulated, enormous heat losses will be generated, which will be manifested by the need for greater fuel expenditure for steam generation and heating of the return steam. In addition, condensate may be produced in the lines and not enough steam may reach the consumption points. It is therefore desirable, and in some cases mandatory, to implement this insulation, including boiler surfaces, pipes, tanks and fittings. In this way, heat losses can be reduced by up to 90%. 40 A2C – Deliverable D1.7 v2.0 In order to calculate the insulation thickness of a surface, it must be taken into account that the greater the thickness, the lower the losses that may occur, so that the amount of condensate decreases, and that the greater the insulation, the higher the investment cost required. In addition, the temperature difference between the steam and the outside, the velocities of both currents, the material, thickness, diameter and length of the pipe, its location and the ambient conditions must be taken into account. 2.2.4.3.2.2 Leakage reduction Reducing steam leakage is one of the biggest potential energy and cost savings in industrial plants. Steam leaks are often caused by poor maintenance of seals, fittings and areas that wear out over the years. These leaks are usually located in pipe joints, valves and traps. Leaks due to pipe failures are easily detectable and should be eliminated quickly, especially due to the risk they pose to operators. On the other hand, trap malfunctions are difficult to detect, especially in closed condensing systems where the trap discharge point is not easily accessible. The main causes of steam leakage at flanged and threaded pipe/valve connections are: (1) stress from expansion and contraction of pipes due to the heat of the steam, (2) threaded components that have loosened due to that stress, and (3) deterioration of gaskets [31]. A facility maintenance programme aimed at finding and repairing leaks is essential for efficient operation of steam systems. The amount of leaking steam in both mains and traps must be estimated. Checking the operation of traps can be done by [27]: ● Visual inspection. ● Sight glass inspection. ● Thermal analysis. ● Acoustic monitoring. Cold production systems 41 A2C – Deliverable D1.7 v2.0 2.2.4.3.2.3 Reduction of condensation temperature In refrigeration circuits, when the condensing temperature in the condensers is high, the compressor work must be equally high to reach the required refrigerant pressure. This relationship between compression and condensing equipment must be considered in the efficient operation of the refrigeration system. Depending on the refrigerant used, the variation in condensing temperature will impact on the energy consumption of the compressor, so adjustments to the condensing unit, aimed at a reduction of its condensing temperature, will save electrical energy in the compressor units. The coefficient of performance improves with a lower condensing temperature. The aim of this recommendation is to reduce the work of the compressor by reducing the condensing pressure at which the refrigeration cycle operates. This results in lower energy consumption of the compressor. Other benefits can also be obtained, such as lower discharge temperature and increased compressor life due to less extreme conditions. There are several courses of action to reduce the condensing temperature: ● Change of condenser type: There are different types of condensers for the same purpose, each of which will give a different condensing temperature. ● Variable pressure control: Normally, fixed condensing pressure controls adjusted to the most unfavourable conditions of the year are used. The measure is to remove the fixed control and allow the condensation to fluctuate with the ambient conditions. ● Evaporative pre-cooling of the condenser cooling air: This reduces the inlet temperature of the refrigerant. 2.2.4.3.2.4 Evaporating temperature increase The cooling capacity of a compressor, and therefore of a refrigeration circuit, basically depends on two temperatures: the evaporating temperature and the condensing temperature. When the condensing temperature drops, the cooling capacity increases. When the evaporating temperature rises, so does the cooling capacity [32]. 48 A2C – Deliverable D1.7 v2.0 The energy management is based on the continuous improvement cycle, also called the Deming wheel: Plan-Do-Check-Act and aims to [36]: ● Develop a policy for a more efficient use of energy. ● Set targets to meet the policy. ● Use data to better understand and make decisions about energy use and consumption. ● Measure results. ● Review the effectiveness of the policy. ● Continuously improve energy management. 2.3 Renewable energies Once the processes have been optimised to the maximum, the energy used might come from renewable sources in order to achieve environmentally sustainable transformations. Even though the adoption of renewable energies is always beneficial from the environmental point of view, it is important to reduce consumption first through energy efficiency measures and then using renewable energy sources to supply the required energy so efforts required to implement these RES are minimised. By doing so, power plant’s dimensions can be reduced and so the installation’s cost (in case of building a power plant) or the energy bill (in case of energy purchase). 2.3.1 Energy generation from renewable sources In this section, different renewable sources used to obtain energy are presented. These are: i) Photovoltaic ii) Wind iii) Biomass iv) Hydraulic energy v) Solar thermal vi) Biogas vii) Combined solutions 49 A2C – Deliverable D1.7 v2.0 viii) Hydrogen Despite the impacts of the COVID-19 pandemic, renewable energy set a record in new power capacity in 2020 and was the only source of electricity generation to register a net increase in total capacity. Investment in renewable power capacity rose, although slightly, for the third consecutive year, and corporations continued to break records for sourcing renewable electricity. Installed renewable power capacity grew by more than 256 gigawatts (GW) during the pandemic, the largest ever increase. China again led the world in renewable capacity added, accounting for nearly half of all installations in 2020 and leading the global markets for concentrating solar thermal power (CSP), hydropower, solar PV and wind power. Overall, 2020 was an important milestone for climate change policy, many countries' greenhouse gas targets for the year expired. Countries set new targets, and many committed to carbon neutrality. Here are some facts about market and industry trends: ● Modern bioenergy provided 5.1% of total global final energy demand in 2019, accounting for around half of all renewable energy in final energy consumption. ● Geothermal electricity generation totalled around 97 TWh in 2020, while direct use of geothermal heat reached about 128 TWh. ● The global hydropower market grew in 2020, but China was responsible for more than half of capacity additions. ● Ocean power represented the smallest portion of the renewable energy market, yet new targets for ocean power capacity were set during the year. ● Solar PV had another record-breaking year, adding as much as an estimated 139 GW, for an estimated total of 760 GW. ● Despite declining costs, concentrating solar thermal power capacity grew in only one country during 2020. 50 A2C – Deliverable D1.7 v2.0 ● An estimated 25.2 gigawatts-thermal (GWth) of new solar thermal capacity was added in 2020, increasing the global total 5% to around 501 GWth. ● The wind power market achieved a record-breaking 93 GW of new installations, bringing total capacity onshore and offshore to nearly 743 GW. Therefore, the installed capacity in 2020 vs 2019 was as follows: 2019 2020 INVESTMENT New investment (annual) in renewable power and fuels billion USD 298.4 303.5 POWER Renewable power capacity (including hydropower) GW 2,581.0 2,838.0 Renewable power capacity (not including hydropower) GW 1,430.0 1,668.0 Hydropower capacity GW 1,150.0 1,170.0 Solar PV capacity GW 621.0 760.0 Wind power capacity GW 650.0 743.0 Bio-power capacity GW 137.0 145.0 Geothermal power capacity GW 14.0 14.0 Concentrating solar thermal power (CSP) capacity GW 6.1 6.2 Ocean power capacity GW 0.5 0.5 HEAT Modern bio-heat demand (estimated) EJ 13.7 13.9 Solar hot water demand (estimated) EJ 1.5 1.5 Geothermal direct-use heat demand (estimated) PJ 421.0 462.0 Table 2. Renewable Energy Indicators 2020. Source: [15] Additionally, during the last years, there has been a growing interest in wind power, followed by solar energy. New developments, like improved battery technology and offshore solar farms, are expected to speed up renewable growth through 2020. Other renewables, however, are beginning to lag behind like hydroelectric. Its growth has stagnated over the past few years due to increasing criticisms of the environmental impact of hydropower. Many experts also fear climate change may render some river flows too weak or inconsistent to provide significant or reliable power [37]. 51 A2C – Deliverable D1.7 v2.0 2.3.1.1 Photovoltaic energy A Photovoltaic System (PVS) transforms the sunlight into electricity. These systems greatly vary in size, which can be from small rooftop or portable systems to massive utility-scale generation plants, producing up to megawatts. Nowadays, most of the conventional PVSs are connected to the network, whereas the isolated or independent systems only represent a small market portion. In some regions, solar photovoltaic energy is the main renewable energy resource. The PVS have continuously been improved and they are a mature eco-friendly technology, which presents high yields. Whether the facility has been well-designed and wellmaintained, the facility will correctly work having a long operational life. Besides, its costs are continuously decreasing since technology is being enhanced. On the other hand, it is interesting to underline that a PVS has a fast assembly and minimum maintenance requirements, although it has to be periodically revised to ensure its correct performance and, also, the part of panels exposed to the sun has to be cleaned. It is worth mentioning that even on a cloudy day, the PVS generates electricity, although the yield is lower. 2.3.1.2 Wind energy The wind power consists of using the airflow, which passes through wind turbines to provide mechanical energy to turn the electrical generators. Wind farms have many individual wind turbines, which are normally connected to the electrical energy transmission grid. The onshore wind energy is an economic, competitive and, generally, a cheaper energy source compared to carbon and gas plants. On the other hand, there is another kind of wind generation: the offshore wind. In comparison with the onshore wind, this has an advantage over the other one: it has the presence of steadier and stronger wind. Moreover, the visual impact of offshore wind turbines is lower. Nevertheless, construction and maintenance costs are much higher. Small onshore wind farms can either provide electricity to the grids or isolated-grid places. In 2017, the total global installed cumulative small wind capacity was estimated at more than 1.0 GW, being China, Italy, U.S. and U.K. the market leaders in terms of installed units [37]. 52 A2C – Deliverable D1.7 v2.0 In order to implement small wind turbines, the building location and the surrounding characteristics take great importance since the investment feasibility will increase as a function of wind intensity. This intensity depends on [38] [39]: i) The height, since the wind speed increases with this. ii) The location since it is windier in plains and sea vicinity zones. Therefore, the conditions to set up this kind of turbine will be better in isolated constructions, close to the sea, tall zones and without surrounding obstacles which can hamper the wind. 2.3.1.3 Biomass Bioenergy is renewable energy which comes from biological resources. Biomass is any organic material which accumulates solar light as chemical energy. Several materials such as wood and its residues, straw and other crop wastes, manure, sugarcane and many other by-products from a wide variety of agriculture processes could be used as a biofuel. Hence, biomass is the fuel, and the bioenergy is the energy accumulated into the biomass. Depending on the water content of the biomass, the chemical energy contained in it could be used in different ways. The most extended valorisation process of dry biomass is the direct combustion (exothermic reaction). Besides, there are ways to obtain energy products from dry biomass, these are by gasification or pyrolysis processes. These technologies seek the thermal degradation of organic matter in the absence of oxygen. Instead, other vector gases can be used, such as hydrogen or steam. With these processes, different products could be obtained, among them, syngas, a very appreciated gas used in a lot of applications, like hydrogen extraction for clean energy production. 2.3.1.4 Biogas On the other hand, for biomass with high moisture content, it is possible to obtain energy products, like biomethane, through anaerobic digestion. Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The main products of this process are biogas and a liquid digestate. 53 A2C – Deliverable D1.7 v2.0 Biogas is an ideal renewable energy source. Anaerobic digestion of industrial, agricultural, and livestock wastes and sewage sludge mainly produce it. Biogas is mainly composed of CH4 (around 60%) and CO2 (around 40%). Because of its methane content, biogas has an important calorific value. The main way of using biogas is through biogas boilers for the recovery of thermal energy. It is usually used to meet the heat needs of the facility in which it is generated. However, the combustion of the biogas can be carried out in a CHP (Combined Heat and Power or cogeneration) engine, in which thermal but also electric energy is generated. This could be employed to satisfy plants' energy demands or it could be injected to the grid. In addition, biogas could be upgraded to biomethane, through several technologies, to be recovered as biofuel for vehicles or injected into the natural gas network. 2.3.1.5 Hydraulic energy Hydropower is the energy derived from potential energy. This kind of renewable energy has been used from ancient times by different sorts of water mills for both irrigation and the operation of several mechanical devices. The hydroelectric plants can be categorised in two types: big plants, those providing more than 10 MW; and small plants (< 10 MW). The small independent hydroelectric plants provide around 115 MW around the world [39]. There is another kind of hydraulic energy, which is linked to the water movements in oceans and seas and presents a huge potential of kinetic energy: tidal power stations. Tidal energy is renewable energy generated by sea waves, tides, salinity, and the temperature differences in the ocean, which can be harnessed to produce electricity. 2.3.1.6 Solar thermal energy Solar thermal energy is the technology which takes advantage of solar energy to generate thermal or electrical energy. Its collectors are classified depending on the temperature as high, medium and low. Low-temperature collectors are not generally glazed, being used to warm both swimming pools and ventilation air. Medium-temperature collectors are similar to low-temperatures ones, but they are used to warm water and air in residences and stores. 54 A2C – Deliverable D1.7 v2.0 Finally, the high-temperature collectors concentrate solar light employing mirrors or lens, achieving temperatures up to 700ºC [39]. These are used in industries and to produce electricity. This kind of energy generation presents a high yield thanks to the wide number of sun hours the whole year in southern Europe. However, there are periods of times where the solar radiation is low and there is no energy production. For this reason, this sort of energy generation normally has a support system [40]. If this system is based on renewable sources, for instance, a biomass boiler, it would be able to generate hot water for sanitary use and heating under the most efficient way, almost without emissions and reducing the primary energy consumption [41]. Whether the installation has been well-designed and wellmaintained, it will correctly work, having a long service life. Besides all of this, its feasibility is guaranteed due to the installation costs being not too high. 2.3.1.7 Combined solutions Today, it is possible to combine several technologies to generate electricity, even mixing conventional techniques, which use fossil sources, and renewable ones. These combinations can be integrated into micro-grids or smart networks. Usually, photovoltaic or wind systems are combined with power generators, especially if there is no network connection. This is because they are cheaper and cheaper since, for instance, the watts per hour price from renewable systems is currently lower compared to that one coming from power generators [42]. The addition of power generators is due to fluctuations of natural resources or unexpected consumptions. However, it is remarkable that a hybrid solution based on renewable sources is virtually independent of fossil fuels problems like its variable costs due to, for instance, political decisions. On the other hand, integrated batteries in wind turbines can enable shortterm energy storage, reducing costs, and increasing the reliability and yield [43]. 55 A2C – Deliverable D1.7 v2.0 2.3.1.8 Hydrogen Hydrogen is one of the very few options for storing electricity over days, weeks or months. Today hydrogen is mainly used in the refining and chemical sectors and it is produced from fossil fuels, accounting for 6% of global natural gas use and 2% of coal consumption and being responsible for 830 MtCO2 of annual CO2 emissions. At the moment, hydrogen is an object of great interest in the energy sector, a large number of projects exist in which “green hydrogen” (hydrogen produced through electrolysis, using water and renewable energies) is produced. Scale-up will be critical to bring down the costs of technologies for producing and using clean hydrogen, such as electrolysers, fuel cells and hydrogen production with CCUS [44]. 2.3.2 Renewable energies in the agricultural sector Almost all of previously mentioned renewable energies can be applied in agriculture: There are some projects in which special PV panels that allow solar radiation required by plants to pass through or even floating PV installations on agricultural water reservoirs, reducing water evaporation while producing energy. These approaches, in which energy generation and agriculture coexist are of great importance, as one of the main social issues that exist today when a new solar farm is projected is precisely the opposition from part of the society that claims that agriculture is being displaced by solar energy installations. Besides, it would even be possible to generate more energy than it is consumed by the farmer, who would be able to sell it and receive an additional income from agriculture. The production of hot water using solar thermal systems to rise the temperature in greenhouses is also used in some cases [45]. This thermal use of solar energy is especially relevant due to the high cost for which heating greenhouses in winter accounts for (around 70% of the total production cost) [46], being possible to use this thermal energy in solar dryers. Eolic energy can be of great interest when the required distances and wind speeds can be reached, but this is not always possible. The minimum speed for small wind turbines to start 56 A2C – Deliverable D1.7 v2.0 rotating is around 2 m/s, at 3.5 m/s turbines start generating electricity, while the speed for max power generation is between 10 and 15 m/s. Spacing between turbines because of the length of blades and the effect on the wind must be kept: a usual rule-of-thumb is spacing turbines around 7 rotor diameters away from each other. In this case, the application would be entirely related to energy use. Biomass is a kind of energy that fits perfectly with agriculture, since due to its activity an important amount of wood and other organic residues is produced. These residues can be valorized in thermal applications or even used to generate biogas in bio-reactors. Some applications include the production of biogas, biomethane or biohydrogen. However, in the A2C project, the organic waste will be used for the production of bioplastics and valuable extracts instead. Hydraulic energy is not always available, since it requires an available water source from which energy can be obtained. In agriculture, using microturbines would be possible to recover energy from the tubes when using gravity-fed systems [47], but the energy produced would be negligible. In most cases it would not be wise to implement these devices in pumped-systems, as energy is transformed from pressure energy to kinetic energy and then electrical energy, losing part of it in the process. As a result, generated energy would be lower than the one consumed in pumps. This system would only be an option in those cases in which a higher pressure is required for some initial points of the water grid, remaining higher pressure than required in later points, thus installing these microturbines. Finally, hydrogen can be produced by using an electrolyser and then used to generate heat or electricity, but this would only make sense if storing energy is required, since energy is needed to produce hydrogen, and there are efficiency losses both during the production of hydrogen and during its transformation in heat electricity. Heat can be produced burning hydrogen, while electricity can be produced using a fuel cell, which is an electrochemical device in which hydrogen reacts with oxygen to produce water and electricity. In some cases, usable heat can be produced too by these devices. Hydrogen is an interesting option for energy storage when long-time solutions are required since, unlike batteries, no energy loss through time is experienced in hydrogen systems. Besides, once a hydrogen storage 57 A2C – Deliverable D1.7 v2.0 solution is implemented, little extra area is required to significantly increase storage capacity. However, the required investment associated with hydrogen technology is still high due to its low maturity and when compressed hydrogen storing solutions are adopted, a relevant part of energy is consumed in compressors. 2.3.3 A2C processes implementation In this section different green technologies for in-situ renewable energy generation, and the viability of its implementation are presented. Some of these technologies like wind and solar energy can be applied without emitting pollutants or exhausting gas into the atmosphere since they are environmentally friendly and pollution-free energy sources. 2.3.3.1 Solar photovoltaic power Solar photovoltaic power generation, which has the remarkable advantages of cleanness, high efficiency, safety, and renderability, has become one of the environmentally friendly alternative energy sources [48]. On the other hand, this energy generation has also social-economic advantages like easy installation, little maintenance requirements, a long-life service, high resistance to extreme climatology conditions, it is independent of fossil fuels producer countries, it can be implemented in those non-interconnected zones (NIZ), and the production can be increased in a modulate way and sold to the grid. Solar energy can be used to pump water or treat wastewaters. This energy can also be directly utilised to any processes. In general, it could be employed in any electricconsumption treatment system. Despite all these advantages, the intermittence of this power source is an important drawback to deal with. The most direct solution is to accumulate the energy generated in the hours of the day with the most radiation in batteries, for later consumption at night. Nevertheless, this increases the investment costs. An alternative could be, for instance, taking advantage of the “net balance” option, which involves pouring into the grid at production hours, and consuming it when self-produced energy is not available. New legislation has been developed and it 64 A2C – Deliverable D1.7 v2.0 medium-sized processing plants to normally not be able to implement this technology. BIOGAS Biogas is a simple and low-cost technology that encourages a circular economy. Gas generated through biodigestion is non-polluting. It would only be feasible if there is a company with organic waste nearby such as WWTPs, food industries etc. HYDROGEN It is a very good alternative as a more sustainable use of batteries, as it does not generate any waste and generates adaptability to energy production through renewable energies. The current price of their production limits their implementation. Table 3. Pros and cons of renewable sources. To sum up, different renewable energies are available to be chosen from. Depending on the specific location and requirements of the project, some options may be more appropriate than others. For instance, PV solar energy can be of great help in southern Europe, where there is generally higher solar radiation, but not so much in northern Europe; biogas can be a good choice as long as its price is low or there are available wastes to produce it. In any case, the implementation of energy efficiency measures and RES help reduce the carbon footprint of any process, be it agricultural or industrial. In agriculture, the use of solar or wind energy to provide electricity to pumps or illumination, the valorization of wood waste to produce biogas, the use of alternative fuel vehicles or the use of solar thermal power to heat greenhouses could reduce its impact on the environment by lowering greenhouse gas emissions. In the A2C project, all these recommendations will be taken into consideration to lower GHG emissions as much as possible. A LCA will be performed in future deliverables, analysing the project’s impact on the environment, not only due to energy and water consumption, but also considering subproducts, by-products and final products. 65 A2C – Deliverable D1.7 v2.0 3 Water recommendations 3.1 Water issues related to agriculture Water is an essential resource in agriculture, both for growing crops and for processing the produce into products. The sector however puts pressure on both water availability and water quality. In Spain, agriculture represents 65% of all water extractions, of which less than 30% is accounted for by ground water. In addition, diffuse pollution from agriculture causes nitrate, pharmaceuticals and pesticides to end up in 34% of surface water bodies and 56% of groundwater bodies [55]. For the region of Murcia specifically, water has been the subject of many debates and disputes. Murcia, a region known for its agriculture, receives water from the Tagus River via a system of pipelines and aqueducts to the Segura River basin. Despite the extra water imported to the region, only 4% of the original runoff of the Segura River reaches its mouth. This increases the risk of desertification, and groundwater levels are falling [56]. Restrictions on the amount of transferred water forces farmers to look for alternative water sources, which are often more expensive, and therefore not feasible. Desalinated water is five times as expensive as water from the aqueduct, and concerns surrounding the mineral content of the water and its effect on crops have been raised. In addition, desalinating water requires about 3kWh per cubic meter, increasing energy consumption and carbon footprint of the water. Alternatively, the agricultural sector is looking into reuse of water. The European Commission (EC) approved Regulation 2020/741, which describes the minimal requirements for water reuse in agriculture. This regulation is in effect since June 2023, and opens the road to the use of treated wastewater for irrigation [57]. The implementation for this way of reuse however requires extensive infrastructure, which comes at high investment costs. . In addition, water treatment comes at higher cost and energy consumption compared to using freshwater, which slows its implementation for irrigation use. Hristov et al. investigated the potential of reusing treated wastewater for irrigation in a European context [58]. The average potential reduction of freshwater use was 14%, where Belgium has the 66 A2C – Deliverable D1.7 v2.0 highest potential at 35% and Czech Republic the lowest, around 1%. This simulation however is only the potential reuse, the actual situation is far from the calculated potential. Finding a solution or alternative source for irrigation water is out of scope of the A2C project. However, the project deals with treatment of water streams in the processing and packaging of agricultural products. Reducing the intake of water for such processes, either by smart process design or reuse of water streams, also reduces the pressure on water sources in an area already affected by water scarcity. 3.2 Water in the circular economy Water is one of the most essential resources on earth, as it is essential to survival of all life. For humans, water is very important in many sectors, such as industry, agriculture, heating, cooling and other sectors. Although the amount of water on our planet stays the same and is considered renewable because it circulates through the water cycle, in recent years shortage of fresh water is an emerging problem [59]. Therefore, water has to be treated as a valuable resource, and plays a large role in the circular economy [60]. The circularity of water has been incorporated in several of the Sustainable Development Goals (SDGs), as presented by the United Nations in 2015 [61]. Goals such as moving towards sustainable agriculture, availability of clean water, preserving aquatic environments worldwide and the sustainability of production processes and tourism all require a different approach to how we use and dispose our water. Goals such as moving towards sustainable agriculture, availability of clean water, preserving aquatic environments worldwide and the sustainability of production processes and tourism all require a different approach to how we use and dispose of our water. Within Europe, water management over the past 30 years has moved towards sustainable use of water, which is apparent from adopting EU legislation such as the Drinking Water Directive [62], the Urban Waste Water Treatment Directive [63] and the Water Framework Directive [64]. These legal acts ensure the drive to improve the status of water within the EU. 67 A2C – Deliverable D1.7 v2.0 To ensure the availability of fresh water for this generation but also for the future, it has to be incorporated in a circular model. Circularity does not only include the reuse of the water, but also reusing the substances in the water, to ensure a near zero discharge of materials into the environment. The A2C project embodies this view by aiming to integrate all the waste streams from the Murcia region into a circular model. Not only the waste streams from agriculture are changed into resources for new and sustainable materials (bioplastics, components for cosmetics etc.), but the water streams in the accompanying processes are also considered. When considering the circularity of water in particular, it is worth mentioning that the water has to be treated to be suitable for the purpose it is required for. In addition, the availability of water within the Region that will be used again, contributes to the self-sufficiency of the region. When designing a suitable system for water reuse, both the fit-for-purpose treatment and the self-sufficiency have to be taken into account. Smol, Adam and Preisner state that in waste management, some methods that prevent the loss of water are already implemented, and can be classified according to the following list [65]: ● 2Rs: reduction and reuse, ● 3Rs: reduction, reuse and recycling, ● 4Rs: reduction, reuse, recycling and recovery. Reduce encompasses all processes that prevent the generation of wastewater, including reducing the use of water. Reducing the intake of fresh water reduces the pressure on fresh water availability, and also reduces the amount of pollution that might be spilled into the environment. Reuse can further release the pressure on fresh water supplies. Any water that can be reused in for instance production processes prevents the use of potable water for nonpotable purposes. Within the A2C project, it is viable to consider the exchange of water streams between processes, if the proper treatment steps allow this reuse. 68 A2C – Deliverable D1.7 v2.0 Recycling is the reclamation of potable water from wastewater. It has to be noted however that this strategy often comes with high costs, and should only be considered if the wastewater cannot be reused in other processes. Recycling of water requires advanced technologies such as membrane filtration, which is able to remove most pollutants. Recovery is the strategy that is most related to the A2C project. By treating the pollutants in the water not as a problem but as resources for instance fertilizers, biopolymers and cosmetics, value is added to the wastewater. Smol et al. included two more additional aspects to the circular model presented above, which are: Reclamation, which focuses specifically on the removal of pollutants in the water. In the past years, micropollutants such as medicines, crop protection agents and microplastics reduce the quality of surface water. In the A2C project, considering those possible threats to the water streams involved will have to be taken into account. Rethink is, according to Smol et al, the most important aspect to move towards a circular model. Implementing a circular model effectively requires a change in mentality from ‘take, make, waste’ towards ‘reduce, reuse, recycle, recover’. This will require the cooperation of many partners, and a new way of thinking for society. A2C is an example of rethinking, not only for water, but for agricultural waste as a whole. 3.3 Description of Agro2Circular processes The main waste streams identified in the Agro2Circular project are fruit and vegetable waste, and agricultural plastics such as greenhouse and ground covering films, and post-industrial multilayer plastics. In a circular model, these streams will be treated to recover valuable compounds, and what waste is left will be recycled in other processes. In the following sections, an overview is given of the proposed routes and processes in the Agro2Circular project. The largest water streams which are suitable for reuse will be identified, and possible treatment technologies will be proposed. 69 A2C – Deliverable D1.7 v2.0 3.3.1 Process descriptions: Agrifood wastes treatment The agrifood waste treatment will be done primarily by CNTC. The processes involved are: ● Agrifood waste classification and conditioning. ● Green solvent+ultrasounds assisted extraction of high value substances from agrifood waste. ● Green solvent+enzymatic hydrolysis assisted extraction (EAE)+microwaves assisted extraction (MAE) of high value substances from agrifood waste. ● Purification and conservation of the high value substances. ● Stabilisation and conservation of the high value substances. In these processes, no large waste streams suitable for treatment and reuse have been identified. Therefore, for the rest of the report, these processes will be left out of the discussion. 3.3.2 Process descriptions: Multilayer plastic waste treatment The recycling of packaging materials will be performed by a chain of Agro2Circular partners. These can be summarised as: ● Preliminary decontamination of the multilayer films (Green World Compounding). ● Optical sorting (Iris technology). ● Separation of aluminium from the complex multilayer films (Saperatec). ● Enzymatic recycling of PE and PET (Epoch Biodesign). ● Aluminium recycling (Universität für Bodenkultur). ● Production of building blocks from TPA, EG and alkenes resulting from the enzymatic recycling (University of Milano-Bicocca). ● Production of PHBV and carotenoids (Centro Tecnológico del Calzado y del Plástico, Universidad de Alicante). 70 A2C – Deliverable D1.7 v2.0 In this chain, multiple wastewater suitable for treatment have been identified. The preliminary decontamination of multilayer plastics, as performed by Green World Compounding, consumes large amounts of water. At this moment, the washing water of agricultural films is treated (although minimally) and recycled into the washing line, tap water has to be taken in regularly to compensate for water losses. The waste water from postindustrial multilayer plastics will have different characteristics from the agricultural films because the pollutants are different, so it will also require a new treatment approach. Another consideration in treating this waste stream before either reuse or eventual release into the sewer is the formation of microplastics during the grinding and washing. Microplastics are a pollutant of emerging concern, as they can be found in the air, water and soil, and even in human blood [66]. Their effects on the environment and our health is not fully understood, and therefore release into the environment should be limited as much as possible. The second waste stream that has been identified for treatment is the salty supernatant from the PHBV and carotenoid production. These compounds are produced by halophilic organisms in a highly saline broth, and after fermentation a large waste stream containing salts, organic residues and possibly other compounds is left. Treatment of this waste stream serves a double purpose: recovering the salts for reuse in PHBV production, and separating off the organic compounds which interfere with the growth of PHBV producing bacteria. The third water stream identified is the broth after enzymatic recycling. This steam might not be as large in volume as the previously described waste streams, but the high value compounds produced justify a treatment process. In this waste stream, the monomers terephtalic acid (TPA) and ethylene glycol (EG) will have to be separated from the broth containing the enzymes and plastics. The enzymes and plastics can be reintroduced in the process, and the monomers can be used in other applications. 3.4 Recommendations 3.4.1 Methodology In order to give recommendations for the three relevant water streams mentioned in section 8.2.2 it is essential to understand the process in which the water was used and which pollutants can be expected. Furthermore, it is important to understand what the purity of the 71 A2C – Deliverable D1.7 v2.0 separated stream should be for its intended reuse. This is not only relevant for the water, but also for the recovered salts and monomers. The global strategy for determining the most suitable water treatment technology for each of the three defined streams can be summarized as: ● Collecting detailed information on the process in which the waste water stream is produced. At least the following information is required: o A description of the process (for instance, plastic washing and shredding) and the water streams involved in the process o Quality and quantity of the water that is taken into the process (tap water, reused water with certain requirements etc) o Quality and quantity of the effluent of the process, including analytical results of the components in the water o An overview of the water treatment systems already in place, and the efficiencies of those treatments. After the information is collected, analyzed and summarized, a strategy for treatment of the waste water stream can be formulated. To find the most suitable technology, multiple boundary conditions have to be taken into account: ● The prioritized recovered stream: this can be the either the water, or the compounds in the water (such as salts or monomers) ● The required quality of the recovered stream (water, salts or monomers) for its intended use ● Identification of additional opportunities for resource recovery, if any ● Production of additional waste streams, such as regeneration liquids, ● Possible risks of accumulation of harmful substances in either the recovered stream or the waste stream (such as microplastics, heavy metals etc) ● Any additional boundary conditions dictated by the specific process or waste water stream. 72 A2C – Deliverable D1.7 v2.0 Based on this information and boundary conditions, possible treatment technologies can be identified. The performance of the technology however has to be tested in practice, which will be done in WP3, WP5 and WP6. 3.4.2 Available treatment technologies The most suitable technology to treat a water stream depends on many factors, such as which pollutants are present, to what standard that water has to be polished for reuse and if a recovery stream is desirable. In this chapter, a first overview is presented of water treatment technologies that can be of value in recovering water and resources in the Agro2Circular processes. The list included in this deliverable contains well-established technologies, but also state-of-the-art technologies It must be noted that regular microbial water treatment (the common treatment technology used in for instance Wastewater Treatment Plants - WWTP) was not included in this list. This was done because the organic components in the wastewater will be used for the production of bioplastics or other resources instead of being removed by conventional treatment. In the following sections, a short overview and description of each technology will be given. The suitability for different pollutants and limitations will be described. 3.4.2.1 Flotation/sedimentation Flotation and sedimentation can be done in one treatment step. When water with particles is left over time, heavy particles (such as soil) will slowly sink to the bottom of the tank, whereas light particles (such as oil and grease) will float to the top of the tank (Figure 10). In WWTPs the scum layer on top is scraped off the surface and disposed of. The sludge layer on the bottom is transported out of the tank via belts or a collection hopper system, depending on how the flotation/sedimentation tank was designed. 73 A2C – Deliverable D1.7 v2.0 The removal efficiency of flotation and sedimentation depends on several factors, such as the density difference between the particles and the water, and particle size and shape. Flotation can be enhanced by introducing air bubbles in a dissolved air flotation system (DAF). Light particles adhere to the bubble surface, and are transported upwards to the scum layer. Sedimentation can be enhanced by using inclined plate settlers. In these sedimentation basins, plates are placed under an angle, aiding the settling of heavier particles in a shorter time. Figure 19. A schematic representation of flocculation and sedimentation. Source: [67] 3.4.2.2 Coagulation and flocculation Small particles, and particles with a density very similar to water, will not be removed by flotation or sedimentation. This often happens with clay particles, microplastics, very small oil droplets and fine organic material. They often have a surface charge, which causes the particles to repel each other, creating a stable suspension. Therefore, a coagulant can be added to the water, which overcomes the surface charge of the particles and destabilised the suspension. The coagulant is often added in a quick mixing process, after which the flocculation step starts. Flocculation is done by gently stirring the solution, and allows the destabilised particles to clump together in larger particles that can settle (Figure 20). 80 A2C – Deliverable D1.7 v2.0 The water in the hot feed stream evaporates into the pores of the membrane, passes through to the permeate side and condenses on the cool surface or liquid stream. The feed stream becomes concentrated, and pure water is recovered. Membrane distillation can be performed using different configurations, for instance using vacuum or a gas stream on the permeate side of the membrane. Membrane distillation is often used for desalination of seawater or brackish water. 3.4.2.7 Adsorption Adsorption is often done by passing the feed flow over a bed of adsorbing material, such as sand, granulated activated carbon (GAC), or ion exchange resins. Pollutants in the feed stream adsorb to the filter material, resulting in clean water. The adsorbing material is chosen based on the pollutants that have to be removed. Sand filters are very efficient in removing particles and microorganisms. Sand filters can be operated as quick sand filters, where the water is pushed through under pressure. Slow or gravity fed sand filters allow the water to trickle down. Slow sand filters are usually colonised by microorganisms in the top layer, which are able to remove organic pollutants in the water. The permeate flow however is much lower compared to rapid sand filters. GAC is a porous form of carbon with a very large surface area per volume. It is capable of removing most organics, heavy metals and some ions from the water stream. It is also commonly used to improve the odour and taste of drinking water in countries where the tap water is chlorinated. Ion exchange resins are commonly used to remove unwanted ions from the water by replacing them with another ion. A common example is the softening of water, where the magnesium and calcium ions are replaced with sodium. Heavy metals can also be removed from water using ion exchange resins. Although adsorption can be applied to remove a great spectrum of pollutants, the adsorption material will become saturated over time and lose its adsorptive properties. At that point, the material has to be cleaned, replaced or regenerated. The backwashing of a sand filter 81 A2C – Deliverable D1.7 v2.0 therefore creates a waste stream with pollutants, GAC has to be regenerated by either chemical or thermal processes, creating a waste stream or consuming a lot of energy. Ion exchange resins have to be regenerated by flushing the column with brine, which also produces a waste stream. 3.4.3 Preliminary recommendations Based on the technologies described in the previous section, the boundary conditions as imposed by the processes and the results from tests on lab scale, preliminary recommendations for water treatment were established. In the following sections, the preliminary recommendations are discussed per Agro2Circular process. The processes recommended here will be tested on pilot scale in WP6 – Demonstrators. 3.4.3.1 Plastic washing water Based on data received from Green World Compounding and additional analysis performed at CEW, the pollutants present in the water were determined. The washing water from postindustrial multilayer plastics is mainly contaminated with fruit leftovers, which results in high organic contamination. The magnitude of contamination depends on the contents of the packaging but also on the time the plastic has been stored, because bacteria present on the plastics consume the organic compounds. The washing water contains microplastics, and possibly also nanoplastics. The goal is to reuse the water for plastic washing, and therefore solid particles have to be removed. For treatment of this water, two possible technologies were selected: ultrafiltration and electrocoagulation. Both were tested in the lab on particle removal. Ultrafiltration was able to remove 99% of all solid particles, whereas electrocoagulation was able to remove 80% of the solid particles. Microplastics removal was confirmed in ultrafiltration. In electrocoagulation, particles were still present in the effluent, but the nature of the particles could not be determined. Detailed results can be found in deliverable D3.2. In WP6, ultrafiltration will be tested on pilot scale, in a feed and bleed configuration. This means the water in the washing line will be treated to conserve water quality, and a small stream of concentrate will be bled from the system. This stream should be concentrated in organics and might be used for PHBV production. 82 A2C – Deliverable D1.7 v2.0 3.4.3.2 Enzyme recovery and monomer separation The enzymatic PET degradation is performed in a broth, and after the hydrolysis a mixture of buffers, enzyme, crystalline PET and monomers is left. The monomers should be isolated to be used in other processes, whereas the enzyme (if it is still active) can de recycled into the degradation process, together with the broth and leftover plastics. The molecular weight of the monomers is about 70 Da for EG and 200 Da for TPA, whereas the enzyme has a molecular weight of 15 kDa. This difference in molecular weight makes size based separation possible, so ultrafiltration with a molecular weight cutoff of 10 kDa was selected. A small PES membrane cell was used to filter the broth on lab scale, and about 90% of the monomers could be recovered. This waste stream is relatively small and will not be tested on pilot scale, but might be demonstrated in WP6 on a tabletop scale setup. 3.4.3.3 Salt recovery from PHBV fermentation broth After PHBV production, the biomass is removed from the broth with ultrafiltration. The resulting permeate contains salts, dissolved organic compounds and possibly other nutrients. The goal of the water treatment is to recover the salts for reuse in the fermentation process, without also adding compounds that could hinder the bacterial growth. It has been observed that recycling part of the spent broth to a fresh fermentation batch influences the PHBV production negatively, which might be caused by EPS-like substances in the liquid. To separate the salts from the organic compounds, electrodialysis is an appropriate technology. The fermentation broth will be desalinated, producing a concentrate with high salt concentration, and a product stream with the organic compounds. The product stream can be discarded or used in a different process, and the concentrate with salts can be reused in the PHBV production process. This treatment technology is currently tested in WP5, and will be demonstrated on tabletop scale in WP6. 83 A2C – Deliverable D1.7 v2.0 4 Conclusions Deliverable 1.7 establishes a set of recommendations on energy efficiency (use of renewable energy technologies and optimisation of key energy parameters) and sustainable water & wastewater management (preliminary water demand, water quality criteria and wastewater characteristics) for the A2C processes and technologies. These processes are still at a medium TRL level and are therefore not implemented on a large scale. Because of this, the A2C processes are still in the design phase which is the right time to consider all the measures that can be taken to optimise them and make them as energy efficient as possible, which will also have an impact on improving their economic viability. With regard to energy efficiency, a series of generic recommendations have been described throughout the deliverable, focusing on the reduction of process demand, the need for maintenance and controls once the processes are implemented on a larger scale, the incorporation of the most efficient equipment and the importance of energy monitoring. Due to the fact that the specific equipment involved in each process was not yet available, generic recommendations have been made for heating, cooling and compressed air equipment, as well as electric motors. Later, once the necessary information has been obtained, specific measures related to energy efficiency will be suggested for each process. Once the energy efficiency recommendations have been made, as energy use is inevitably necessary in all processes, a number of renewable energy alternatives have been proposed to make the processes sustainable. The renewable energies described are solar, wind, biomass, biogas, hydroelectric, solar thermal, combination of several and hydrogen, although it is considered that for the processes of the A2C project the most suitable renewable energy sources are those described in Table 3 (solar, wind, biomass, biogas and hydrogen). 84 A2C – Deliverable D1.7 v2.0 The two largest water streams in Agro2Circular are produced by the washing of postindustrial multilayer plastic packaging, and by the PHBV production in saline conditions. In addition, the small water stream produced by enzymatic degradation of PET has been selected for treatment, due to the high value compounds that can be recovered. For each of the three processes, membrane-based solutions have been proposed and, in some cases, already tested. For the plastic washing wastewater, ultrafiltration was selected to remove the solids from the water. This also makes sure microplastics are removed, so they are prevented from ending up in the environment. For the enzymatic degradation broth, ultrafiltration with a specific molecular weight cutoff of 10kDa was used, so the monomers could be separated from the enzymes and leftover plastics. This ensured monomer recovery of about 90%. For the recovery of salt from the supernatant of PHBV recovery, electrodialysis is the most suitable technology. Electrodialysis selectively removes salt from the water stream, whereas the organic compounds that could influence PHBV production stay behind. The salts can be reintroduced in the fermentation broth, and the organic waste stream can be either discarded or reused in a different process. 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