Advancing circular bioeconomy: trends, clusters, and roadmaps in biofuel production and waste valorisation

774 Agronomy Research 22(2), 774–793, 2024 https://doi.org/10.15159/AR.24.067 Advancing circular bioeconomy: trends, clusters, and roadmaps in biofuel production and waste valorisation Y. Chernysh1,2, V. Chubur1 and H. Roubik1,* 1Czech University of Life Sciences Prague, Faculty of Tropical AgriSciences, Department of Sustainable Technologies, Kamýcká 129, CZ16500 Prague, Czech Republic 2Sumy State University, Faculty of Technical Systems and Energy Efficient Technologies, Department of Ecology and Environmental Protection Technologies, 116, Kharkivska Str., UA40007 Sumy, Ukraine *Correspondence: [email protected] Received: January 31st, 2024; Accepted: May 24th, 2024; Published: July 16th, 2024 Abstract. Today, one of the important tasks of bioeconomy development is waste management based on the principles of environmental management and bioenergy production. In the context of this issue, this review focusses on the analysis of current trends in biofuel production that involve sustainable feedstocks and the valorisation of waste into useful bioproducts in agriculture. The scientometric method included the use of Scopus and Web of Science databases to compare the coverage of the research topic with keyword chain optimization. In addition, bioinformational databases was used to support the involvement of secondary raw materials in the bioprocessing cycle. The implementation of the research objectives resulted in the identification of bioeconomy clusters that emphasize the importance of developing specific regional circular bioeconomy strategies while avoiding ‘one-size-fits-all’ solutions for individual sectoral technologies. An example of bioeconomy development in the world is bioenergy. The structure of bioenergy has been analysed. A roadmap for biotechnology modernisation was proposed using the example of anaerobic waste conversion process as part of the implementation of a circular bioeconomy. The stages of the roadmap for the modernisation of bioenergy technologies were analysed within the framework of the sectoral implementation of the circular bioeconomy. The efficiency indicators for the implementation of bioeconomy in agricultural production have been determined. In addition, an important direction unifying anaerobic technologies with the agricultural sector is the enrichment of digestates with macro and microelements, which is possible due to mineral additives, for example, phosphogypsum. This direction was also considered from the point of view of environmental safety. Key words: bioeconomy, renewable energy, agricultural production, waste recycling. INTRODUCTION When discussing economic development with a focus on biotechnology, emphasis is placed on circular bioeconomy as a thermodynamic approach to the instability of the economic process based on the concept of entropy. McDougal (2022) presents a model of bioenergetic evolution at the planetary level that implies that, in theory, significant 775 public investment in terrestrial solar generation may be required to realise a planetary energy transition and prevent ecological collapse. This demonstrates the importance of energy for economic evolution at the planetary level. Leff (2021) demonstrates a nongentropic productivity that the authors claim mobilises the ecological organisation of life on the planet based on an alternative production paradigm. This ecotechnological paradigm increases the biosphere's production of natural use values by converting solar energy into biomass generated by photosynthesis and symbiogenesis, with a technological system designed to increase this potential, utilising and limiting entropic decay, rooting sustainable livelihoods in the cultural imagination. Additionally, cross-sector collaboration and regional incentives for waste management need to be implemented. The high costs associated with retrofitting biogas facilities, collecting and preprocessing raw materials, as well as developing downstream production processes for customers, could potentially impede the rapid integration of the concept of biowaste supply chain and its products into the market (Siegfried et al., 2023). The development of bioeconomy based on sectoral integration of bioproducts of different target orientation is of strategic importance for the leading economies of the world (China, USA, Germany, Sweden, etc.). At the same time, bioenergy is increasingly being demanded as a branch of applied development and participation as a stable raw material base for various types of waste (Hu et al., 2023, Moustakas et al., 2023). Figure 1. Biomethane production projects in the world (based on Statistical information sourced from IEA Bioenergy). According to the data compiled, the diagram shown in Fig. 1 illustrates the countries that are leading in the implementation of biomethane technologies. France, with 477 projects, leads the chart, with biomethane used primarily by public authorities and companies, which currently represent the majority of biomethane consumers, primarily using it as a transportation fuel (European Biogas Association, 2017). 776 Germany, with 254 biomethane projects, is second, with biomethane primarily used for electricity production in combined heat and power (CHP) plants, and its use as fuel is indirectly supported and developing (European Biogas Association, 2020). The United Kingdom, which has 106 biomethane projects, involves most of these projects being connected to gas distribution networks (Green Gas Certification, 2024). Sweden, the Netherlands, Denmark, and Finland are among the countries with well-developed biomethane technologies, with biomethane projects in these countries accounting for about a quarter of their biogas plants. Governments around the world are supporting this trend, furthering the development of the biomethane sector. Despite the fact that biomethane is currently not regulated at the European level, some countries, such as Germany, have introduced legislation that regulates the introduction of biomethane mesh. At the initial stage, when the first biomethane plants were built in Germany, there was no such legislation in the country. The first innovative plants were established by agreement between the main stakeholders, such as the biogas plant operator, the natural gas network operator, and the authorities (Thrän et al., 2023). It should be emphasised that in Ukraine, only a small number of companies (up to 2% of the total) have the opportunity to implement biomethane (BM) projects with a capacity of 100 m3 h-1 of biogas or more, using only waste from their own production. To a greater extent, these are large-scale poultry farms, sugar, and distilleries. The possibility of implementing large-scale projects (2,000 m3 h-1 of biogas or more) using the raw materials of a single enterprise is limited to single examples. On the basis of this, promising BM production projects may be those that combine the fermentation of waste from several enterprises and/or plant material. A large-scale increase in biomethane production requires the use of part of agricultural land to grow plant material (Geletukha et al., 2022). Biological waste is a source of environmental pollution and a significant repository of valuable resources because of the large amount of organic and biodegradable components it contains that can be reused. Recycling biological waste into resources through bioprocessing can help reduce carbon emissions and the growing environmental problems associated with solid waste (Mishra et al., 2023). Continuous innovation and research into large-scale fermentation processes are needed to make this technology more economically feasible and competitive, while providing global markets with an ever growing and more diverse range of high value biobased products (Verardi et al., 2023). Therefore, this study focusses on reviewing trends in the development of biofuel potential as a branch of the bioeconomy with a focus on the recycling of wastes. The following objectives of the study were achieved: – Bioeconomy strategy for the growth of industrial sectors – Biowaste as a sustainable feedstock for energy production within the framework of bioeconomy promotion – Evaluation of a mineral additive phosphogypsum for use in bioproduction. 777 MATERIALS AND METHODS Life cycle assessments are an important tool for comparing a new biorefinery concept Analytical tools of scientometric databases in the analysis of trends in the development of bioenergy technologies of anaerobic fermentation To optimise analytical research, the Scopus and WoS database platforms have a set of various online tools that can be used to analyse publication activity in the field of anaerobic fermentation for bioproducts. To identify emerging research trends, various combinations of keywords were used, including energy bioeconomy; waste bioprocessing bioeconomy; biofuel waste bioeconomy; anaerobic digestion bioeconomy; biodiesel bioeconomy; biogas bioeconomy; Life Cycle Assessment Bioeconomy; Bioinformation databases. Using the analytical tools of the Scopus and WoS databases, it is possible to work with charts based on bibliographic data according to categories: – number of published works by years (Fig. 3a); – distribution of publications by publications indexed by the database; – number of thematic publications among authors and organizations; – quantitative distribution of published documents by territorial principle (Fig. 3, b); – comparison of institutions that provide funding for research (Fig. 3, c); – distribution of documents by type and field of knowledge to which the text belongs. The total number of publications in databases amounted to 2,456 papers. The field of bioenergy, as a major component of the development of the bioeconomy, began to actively gain momentum in publications starting from 2015. At that time, the importance of opportunities offered by a sustainable bioeconomy became important. Since 2019, with landfill disposal. Specifying the environmental impacts of anaerobic digestion plants on individual substrate types, the impacted stations are shown in Fig. 2. Canva, as a user-friendly graphic design software that offers a wide array of features to create visually engaging content, allowed us to create informative maps, incorporating key data, and trends related to the bioenergy sector. The software was used to develop visually appealing maps that effectively communicate the data collected during the bibliometric analysis of relevant bioenergy data. Figure 2. Life cycle assessment steps for organic waste utilisation through anaerobic digestion to biogas production (based on Ugwu et al., 2022). 778 there has been a threefold increase in the number of publications on this subject, peaking in 2022 with the registration of 514 scientific papers per year (Fig. 3, a). Research and development in this area are actively continuing to make progress. a) Figure 3. Bibliometric data processing: a) Number of articles published by year; b) Distribution of published papers by territorial scope; c) Comparison of institutions that provide research funding. In terms of the geographical distribution of publication activity (Fig. 3, b), most of the research in this area is conducted by scientists from Indian, German scientific academies, demonstrating more than 300 published studies each. At the same time, China and the United States exhibit comparable levels of activity, each accounting for more than 200 publications. This indicates their significant contribution to the progress and development of the bioenergy sector. However, most of the research funding comes from funds from the European Union (Fig. 3, c). In addition, leading positions are held by specialists from Italy, Spain, the UK, and other EU countries (Fig. 3, b). It is worth noting that the types of documents are dominated by articles related to such fields of knowledge as environmental sciences and energy, as well as engineering, including chemical engineering, which means that most of the publications are aimed at improving the environmental situation by comprehensively solving several problems at once - utilisation of organic waste and obtaining alternative sources of fuel from biomass. b) c) 779 Use of bioinformatic electronic databases: KEGG database, BacDive and EAWAG-BBD Bioinformatics databases have a narrow specialisation for microbiologists. The main aspects that were taken into account when using them in this work include the ability to analyse the metabolic pathways of microorganisms associated with the utilisation of the mineral components of phosphogypsum. One of the most known and extensive databases for gene networks, metabolic and signalling pathways is KEGG PATHWAY. A special option of the database interface allows you to customise the diagram for a specific type of organism, and the number of species depends on how universal the biological process is displayed in the diagram. The KEGG REST API allows you to perform and run queries on the information available in the KEGG database (Kanehisa et al., 2017). KEGG REACTION serves as the database for chemical reactions found in metabolic maps and distinctive enzymatic reactions, each with its unique identification number in the database (Shulipa et al., 2020). Using the EAWAG-BBD bioinformation electronic database. Methane, a biogenic gas, is biologically produced from carbon dioxide through methanogenesis, involving 2-electron reductions. Methanogens worldwide generate 1,015 grammes of methane annually, according to the EAWAG-BBD. The interconnectedness of methanogenesis and methanotrophy plays a crucial role in the Earth's C1 metabolic cycle, facilitating the transformation and cycling of C1 compounds. According to Shulipa et al. (2020), this process involves the breakdown and assimilation of C1 fragments by various microorganisms, contributing to the dynamics of the global C1 cycle. The study of these reactions elucidates the principles of biocatalysis, which are essential for understanding the processes of chemical production and biodegradation of environmental contaminants. This includes detailed insights into the metabolic pathways, the chemicals involved at each stage, the microorganisms responsible for these transformations, as well as the relevant enzymes and genetic information (About the EAWAG Biocatalysis, 2014). The BacDive bioinformation database offers a comprehensive repository of information on bacteria and archaea, supporting research into biodiversity among these organisms. This resource is particularly valuable for identifying species that play roles in the anaerobic digestion process, facilitating the search for data on their optimal cultivation conditions in technological applications. The BacDive platform also allows for the exploration of nutrient media, including those with varying compositions of trace elements (BacDive Dashboard, 2022). Additionally, it provides access to taxonomic directories and tools to determine the locations of inoculum selection and analyse their adaptive capacity to changing environmental conditions. RESULTS AND DISCUSSION Bioeconomy strategy for the growth of industrial sectors Biotechnology as a tool for achieving economic realisation has its own sectoral division for application in various economic spheres. 780 According to the international classification, biotechnologies have been established to be distinguished by colour: green (agricultural and environmental biotechnology, including the production of biofuels and biofertilizers); red (biopharmaceuticals, biodiagnostics); white (industrial biotechnology); blue (marine biotechnology, aquaculture); gold (bioinformatics, nanobiotechnology); brown (biotechnology for deserts and arid areas); grey (bioprocesses and fermentation); black (bioterrorism, biological weapons) (Barcelos et al., 2018). The diversity observed in bioeconomic cluster settings highlights the importance of developing specific regional circular bioeconomy strategies, taking into account local the greatest potential for utilisation and emission reductions (OECD et al., 2009). It is gradually expanding its sphere of influence on the economies of different countries. Its influence is projected to increase globally starting in 2030 (Fig. 4). The global dynamics of biotechnology sector development is shown in Fig. 5. Figure 5. Comparative diagram of the distribution of business R&D expenditures and GDP share by type of biotechnology. strengths and weaknesses, while avoiding ‘oneshot’ solutions for individual industry technologies. In addition, research into product and technology design, together with end-of-life strategies for bioproducts, are important elements of the systems. To optimise the potential, clear time-bound milestones are needed that not only promote the development of the bioeconomy as a whole, but also focus on enabling technologies and cascade pathways that promise Figure 4. The bioeconomy will be the next wave of economy. 781 The circular economy aims to change the classical linear model of production by focussing on products and services that minimise waste and other types of pollution. The interdependence between the bioeconomy, green economy, and circular economy is shown in Fig. 6. Figure 6. Diagram of dependencies between different economic concepts. One example of the development of the bioeconomy in the world is bioenergy. Its structure is shown in Fig. 7. Experts estimate that proven oil reserves last for 40–50 years; gas reserves for 80 years; and coal reserves for about 400 years (Statistical Review of World Energy, 2021). Furthermore, the trend of rising gas prices over the past 10 years has increased rapidly, which is an economic prerequisite for the active development of bioenergy. Figure 7. Structure of bioenergy. 782 Efficiency of sustainable development of the bioeconomy: – environmental efficiency: minimizing the impact of production processes on the environment; promoting the conservation and restoration of biodiversity in agricultural landscapes; promoting the conservation and restoration of soil fertility; protecting water resources from pollution. – economic efficiency: gradual increase in the natural productivity of agrocenoses and soils; reduction of production costs due to the refusal to use expensive chemicals and reduction of energy intensity of production; increase in product competitiveness; – social efficiency: creation of additional jobs in rural areas; creation of new prospects for small and medium-sized farms. The basis of domestic agricultural development's environmental policy should be rooted in ensuring its environmental safety through the adoption of green production practices. The greening of agricultural production should be understood as a process that involves combining and cooperating a set of innovative technologies in the sectors aimed at economic growth of the industry and environmental protection as interdependent and complementary elements of strategic agricultural development, which will guarantee high quality food to the population. The sustainable development of agriculture based on the green economy is possible through the use of alternative technologies that are environmentally friendly and ensure increased productivity in harmony with the ecosystem (Gollier et al., 2019). The effectiveness of the implementation of the green economy in agricultural production is confirmed by the following performance indicators: – reduction of soil structure and compaction through agrotechnical measures; – scientifically based application of agricultural land reclamation; – reduction of nutrient losses in the soil; – reducing chemical load through the use of environmentally friendly fertilisers; – use of scientifically based crop rotations; – introduction of environmentally friendly biologically based crop production technologies; – introducing environmental certification and environmental labelling. Biowaste as a sustainable feedstock for energy production within the framework of bioeconomy promotion In general, the application of life cycle assessment to waste management systems has great potential, especially to support the decisions of planners and companies involved in waste collection, transportation, and disposal. The principles of bioeconomy encourage the sustainable use of recycled nutrients and the transformation of conventional systems into sustainable ones to minimise environmental impacts. Thus in Fritzen Cidón et al. (2023) is presented how bioeconomy principles are applied for socio-ecological benefits to Brazilian organic farmers (in the region of Vale do Rio do Sinos, Rio Grande do Sul). The bioeconomic principles applied by Brazilian organic farmers have had a positive socio-ecological impact. Nevertheless, there is still a need for more assistance in the bioeconomy approach, adoption of cleaner technologies and independence of external suppliers without organic guarantees. 789 Additionally, during sulfidogenesis, a biological reduction of phosphates occurs, which has been confirmed by previous studies (Plyatsuk & Chernish, 2014): 𝐹𝑒3(𝑃𝑂4)2+3𝑆𝑂42−+6𝐶𝑜𝑟𝑔 →3𝐹𝑒𝑆↓+2𝑃𝑂43−+6𝐶𝑂2, (2) where Соrg is organic substrate. Table 2. Characteristics of sulphur-reducing microorganisms Species Temperature range Note Link Desulfovibrio mesophilic Desulfobaculum senezii CVL (species Desulfovibrio senezii) is an anaerobe, mesophilic bacterium that was isolated from solar saltern https://bacdive.dsmz.de/strain /4136 Desulfonema mesophili Desulfonema ishimotonii DSM 9680 is an anaerobe, mesophilic bacterium that was isolated from marine mud https://bacdive.dsmz.de/strain /3991 Desulfomicrobium mesophilic Desulfomicrobium aestuarii ADR26 is an anaerobe, mesophilic bacterium that was isolated from sediments https://bacdive.dsmz.de/strain /4061 Desulforhabdus mesophilic Desulforhabdus amnigena ASRB1 is an anaerobe, mesophilic bacterium that was isolated from sludge, UASB reactor https://bacdive.dsmz.de/strain /16675 Desulfomonile mesophilic Desulfomonile tiedjei DCB-1 is an anaerobe, mesophilic bacterium that was isolated from sewage sludge https://bacdive.dsmz.de/strain /16666 Desulfarculus mesophilic Desulfarculus baarsii Konstanz is an anaerobe, mesophilic bacterium that was isolated from ditch mud https://bacdive.dsmz.de/strain /17627 Desulforegula mesophilic Desulforegula conservatrix Mb1Pa is an anaerobe, mesophilic bacterium that was isolated from sediment from a shallow freshwater eutrophic lake https://bacdive.dsmz.de/strain /3992 In this process, phosphate and hydrophosphate anions bind to Ca2+ cations to form various modifications of calcium phosphates, which precipitate due to their low water solubility. Additionally, part of the phosphate ions is displaced from the biotechnology system when it passes into the liquid phase. This also corresponds to the results obtained by other authors (Matsuura et al., 2021, Diao et al., 2023). During the precipitation of hydrogen sulphide and HM ions in the form of sulphur, the microbial community works stably (Diao et al., 2023; Qin et al., 2024; Melgaço et al., 2020). In the process of such treatment, a number of biochemical transformations of the components of the waste mixture occur, which is consistent with other research findings (Matsuura et al., 2021; Almuslamawy et al., 2023; Bounaga et al., 2023): – biological reduction of phosphates, with a significant portion of the released phosphate ions chemically bonding with calcium and partially passing into the liquid phase; – calcium carbonate is formed due to the release of carbon dioxide in the system; 790 – during the breakdown of protein compounds, ammonia is released and combined with sulfate ions, forming ammonium sulfate; – complex compounds with HM (HM salts with organic compounds) are destroyed in the course of microbiological processes, HM ions pass into the liquid phase, where they interact with biogenic hydrogen sulphide to form stable metal sulphide compounds. The prospect of industrial implementation in the field of integrated processing of persistent raw materials (biowaste and phosphogypsum) is one of the directions of the realisation of the sectoral bioeconomy. In our further research, we will develop a methodology of synergy of these wastes (as sustainable feedstock) on the basis of biochemical processes of their joint processing with the possibility of implementation in bioenergy and agriculture. CONCLUSIONS The analysis focusses into global advancements in bioeconomy development, particularly within the bioenergy sector. A breakdown of the bioenergy structure is provided, along with a proposed roadmap for the modernisation of biotechnology, exemplified by the anaerobic digestion process, aimed at promoting the principles of circular bioeconomy. Additionally, the integration of anaerobic digestion into broader bioprocessing systems is explored, highlighting its role in biofuel, biochemical and fertiliser production within the circular bioeconomy framework. The stages of this modernisation roadmap are examined within the implementation of sectoral circular bioeconomy, focussing on efficiency indicators relevant to the integration of bioeconomy practices into agricultural production. Furthermore, attention is drawn to a vital synergy between anaerobic technologies and the agricultural sector: the enrichment of digestates with essential macroand microelements facilitated by mineral additives. Utilisation of the compositions of the components of phosphogypsum by various microorganisms is assessed through bioinformation databases, underscoring the importance of environmental sustainability in this context. In further studies, the application of phosphogypsum in bioprocesses will be deepened by biotesting. 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