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Background: New regulations and market conditions in Germany affect the profitability of biomethane upgrading as a repowering option for existing biogas plants following on-site CHP utilization. These conditions present trade-off challenges between higher sustainability requirements, maintaining production capacity and new revenue opportunities. Optimization methods, such as linear programming (LP), are essential for determining the ideal substrate mixture and profitable solutions amidst multiple market conditions, plant-specific process constraints, and substrate properties. Methods: We updated a substrate mixture optimization model within an assessment framework for the repowering of existing biogas plants (BGPs), which focuses on the operator's perspective. By integrating multiple German biomethane markets for various BGPs, we assessed changes in the substrate mixture, GHG emissions, contribution margins, and constraint parameters to derive conclusions for operators and future framework design. Results: Integrating market revenues and constraints can increase contribution margins by 12–55%. Additional gains can be achieved by considering multiple markets simultaneously but limited to a few BGPs. The plant-specific LP solution space and used benchmark market are decisive. The former limits the potential of high substrate-specific contribution margins, which has a significantly higher impact than the relation between plant-specific characteristics and process constraints. The advanced fuel market is currently the lead market for biomethane, incentivizing GHG-emission extensive substrates, decreasing gas production and GHG emissions but increasing levelized cost of energy (LCOE) and partially CO2 abatement costs. Conclusions: The key to improve profitability and to supply an increasing biomethane demand while fulfilling new requirements is a large LP solution space. Increasing market options, substrate availability, and digestion system capacity achieve this on the operator's side. Policy makers could reduce normative requirements such as the maize cap or double counting of advanced fuels and favor high but uniform GHG requirements. Operators can prepare robustly for the future substrate mixture by adding digester volume and pre-treatment tech, ensuring long-term and diverse substrate availability, and contracts with flexible components. Although current market conditions can improve specific GHG emissions, they do not necessarily increase manure usage when other options, such as straw, are viable. Other regulatory support systems will be required to do so. [ABSTRACT FROM AUTHOR]

Accurately characterizing the substrate used in anaerobic digestion is crucial for predicting the biogas plant's performance. This issue makes particularly challenging the application of modeling in codigestion plants. In this work, a novel methodology called substrate prediction module (SPM) has been developed and tested, using virtual codigestion data. The SPM aims to estimate the inlet properties of the substrate based on the reverse application of the anaerobic digestion model n1 (ADM1). The results show that, while the SPM can estimate some properties of the substrate based on certain output parameters, there are limitations in accurately determining all required variables. HIGHLIGHTS Extensive substrate characterization is challenging, especially for codigestion.; A reverse modeling approach is proposed to estimate unknown substrate properties.; The substrate prediction module processes measured AD data based on the ADM1.; Two data processing strategies are assessed: 7-day moving block and daily data.; The SPM could estimate some substrate properties but there are limitations.;

Abstract Background New regulations and market conditions in Germany affect the profitability of biomethane upgrading as a repowering option for existing biogas plants following on-site CHP utilization. These conditions present trade-off challenges between higher sustainability requirements, maintaining production capacity and new revenue opportunities. Optimization methods, such as linear programming (LP), are essential for determining the ideal substrate mixture and profitable solutions amidst multiple market conditions, plant-specific process constraints, and substrate properties. Methods We updated a substrate mixture optimization model within an assessment framework for the repowering of existing biogas plants (BGPs), which focuses on the operator’s perspective. By integrating multiple German biomethane markets for various BGPs, we assessed changes in the substrate mixture, GHG emissions, contribution margins, and constraint parameters to derive conclusions for operators and future framework design. Results Integrating market revenues and constraints can increase contribution margins by 12–55%. Additional gains can be achieved by considering multiple markets simultaneously but limited to a few BGPs. The plant-specific LP solution space and used benchmark market are decisive. The former limits the potential of high substrate-specific contribution margins, which has a significantly higher impact than the relation between plant-specific characteristics and process constraints. The advanced fuel market is currently the lead market for biomethane, incentivizing GHG-emission extensive substrates, decreasing gas production and GHG emissions but increasing levelized cost of energy (LCOE) and partially CO2 abatement costs. Conclusions The key to improve profitability and to supply an increasing biomethane demand while fulfilling new requirements is a large LP solution space. Increasing market options, substrate availability, and digestion system capacity achieve this on the operator’s side. Policy makers could reduce normative requirements such as the maize cap or double counting of advanced fuels and favor high but uniform GHG requirements. Operators can prepare robustly for the future substrate mixture by adding digester volume and pre-treatment tech, ensuring long-term and diverse substrate availability, and contracts with flexible components. Although current market conditions can improve specific GHG emissions, they do not necessarily increase manure usage when other options, such as straw, are viable. Other regulatory support systems will be required to do so.

Annually, a huge amount of waste from plant biomass and animal manure is produced from agriculture and animal farming. Many studies provide information on the biomethane potential of agricultural and livestock wastes, but only a few studies have investigated the application of the substrates in combination. The objective of the study is to enhance the fermentation process in the digester for biogas production, obtained from animal and plant waste substrates. In four batch processes for three months, the temperatures and the residence time of the substrates in the fermenter were analyzed. Simultaneously, electricity and thermal energy were produced via cogeneration units, which were exported to the public grid and city heating network. The plant substrate is a silage mixture of corn and wheat waste. The animal substrate is a mixture of beef and pig manure. Animal and vegetable waste raw materials are collected and transported to the site, located in the region of southeastern Bulgaria. The total annual consumption of animal and plant waste is 17,971 t/year. The enhancement of the process leads to the production of 1,506,000 Nm3 CH4/a of methane, the generation of which requires 299.63 MWh/a of electricity and 649.09 MWh/a thermal energy. [ABSTRACT FROM AUTHOR]

Due to the decarbonization of the energy system, natural gas will only play a minor role as an energy source after 2045. To decarbonize the gas supply in the future, there are two options for green gases: hydrogen or biomethane. The injection of green gases into the existing gas infrastructure leads to changes in the gas composition, requiring a consideration of the framework conditions for distribution. Adjustments to the grid for transport may be required. Consequently, this paper presents the main characteristics of hydrogen and biomethane and examines the suitability of the gas infrastructure for their transportation. A case study for the development of gas infrastructure in Germany is presented. The focus is on the further development of biogas, concentrating on the question of which biogas should optimally be upgraded in the future to enable its be distribution in the long term. [Display omitted] • Dedication of gas infrastructure to hydrogen in competition with the distribution of biomethane. • Examination of the suitability of the infrastructure for the distribution of green gases. • Gas grid development pathways in Germany. • Role of biogas in future gas supply. [ABSTRACT FROM AUTHOR]

The issue of recycling waste from the main production is experiencing growing relevance and importance in the context of sustainable development and environmental protection. In today’s world, where environmental issues and conservation of natural resources are becoming extremely important, manufacturers and consumers are faced with the need to find new innovative approaches to waste management and reducing the negative impact of industrial processes on the environment. Therefore, the use of biogas plants is one of the promising solutions in this direction. These plants play an important role in reducing greenhouse gas emissions, using agricultural waste, improving the production cycle, and contributing to more sustainable and environmentally friendly production processes. This article reveals the importance of biogas plants as an innovative solution for addressing the issues of organic waste recycling along with creating more sustainable production. The article discusses the topical issue of assessing the efficiency of biogas plants, based on both domestic and foreign experience. The analysis of the efficiency of biogas plants is carried out on the basis of a comparison of domestic and international experience. Thus, the authors determine that in order to ensure a comprehensive assessment of the efficiency of biogas plants, it is necessary to thoroughly analyze technical parameters, technological solutions, economic aspects, and environmental indicators. The proposed multi-criteria approach will allow to obtain an exhaustive and objective assessment of the functioning of biogas plants, taking into account most of the key aspects of their efficiency. This will make it possible to determine the optimal areas for improving these plants in order to achieve the highest possible level of productivity and consistency of their operation. Further on, this approach will contribute to making sound managerial decisions and thus achieving a common goal in the modern energy paradigm. The authors propose to assess the efficiency of biogas plants by building a model based on fuzzy logic methods. This approach allows to take into account the ambiguity and uncertainty of incoming information, which gives the possibility to agree on different criteria and parameters, taking into account their unpredictability and dependence on many factors. The results of this model help in choosing the optimal biogas plant that meets the conditions and requirements of today.

Due to the ever-increasing demand and high energy prices (and lack of access), the search for alternative and local energy sources is essential for developing countries; therefore, this study reveals the economic feasibility of using organic waste for biogas production on the Syrian coast. The data was collected through a questionnaire survey among farmers and field visits to the biogas units in Tartus and Latakia provinces from June 2020 to February 2021. The results showed that the total annual return of the biogas unit that depends on plant residues is higher than the total annual return of the biogas unit that depends on animal waste. The study found that every dollar invested in the biogas production unit from animal waste achieves a net return of 0.89 USD without discount factors. In the biogas production unit using crop residues, it was 2.08 USD. The payback period of the small-scale biogas unit is 2.9 years in the animal waste unit and 1.9 years in the plant residues unit. When costs increase disproportion by 20% and revenue slumps by 20% less than expected, every dollar invested in small-scale biogas plants using animal wastes achieves 0.26 USD as a net return without discount factors. On the other hand, every dollar invested in small-scale biogas plants using plant residues earns 1.06 USD as a net return without discount factors. With discount factors, each dollar invested in a small-scale biogas plant using animal wastes achieves 0.012 USD as a net return. Each dollar invested in small-scale biogas plants using crop residues earns 0.13 USD as a net profit. The study found that biogas units that use crop residues are more profitable and should be considered in programs supporting renewable energy, especially with the government's interest in renewable energies and the widespread availability of crop residues in the Syrian environment. [ABSTRACT FROM AUTHOR]

Annually, a huge amount of waste from plant biomass and animal manure is produced from agriculture and animal farming. Many studies provide information on the biomethane potential of agricultural and livestock wastes, but only a few studies have investigated the application of the substrates in combination. The objective of the study is to enhance the fermentation process in the digester for biogas production, obtained from animal and plant waste substrates. In four batch processes for three months, the temperatures and the residence time of the substrates in the fermenter were analyzed. Simultaneously, electricity and thermal energy were produced via cogeneration units, which were exported to the public grid and city heating network. The plant substrate is a silage mixture of corn and wheat waste. The animal substrate is a mixture of beef and pig manure. Animal and vegetable waste raw materials are collected and transported to the site, located in the region of southeastern Bulgaria. The total annual consumption of animal and plant waste is 17,971 t/year. The enhancement of the process leads to the production of 1,506,000 Nm3 CH4/a of methane, the generation of which requires 299.63 MWh/a of electricity and 649.09 MWh/a thermal energy.

Biodegradable waste from households, companies, and gastronomy is not utilized in large Polish agglomerations for the production of biogas. Determining the biogas production potential in a selected agglomeration will enable the implementation of circular economy goals and sustainable development objectives. Once appropriate odor neutrality standards are met, biogas plants could be constructed around large cities, supplying both energy and heating systems to nearby housing estates or production facilities. This article aims to assess the potential of biodegradable municipal waste collected in a large city for the production of energy in specialized municipal biogas plants. The following analytical study focuses on Krakow and its surrounding municipalities. Because of its geographical location, Krakow is exposed to smog, and every action limiting the usage of carbon-based materials for heating will have a positive impact on the air quality. A biogas plant powered by municipal waste would present a viable opportunity to limit urban smog. It is also crucial that a biogas plant can store energy as it is equipped with methane tanks. Both renewable and other energy sources are still awaiting functional technical solutions that would allow for optimal energy storage. [ABSTRACT FROM AUTHOR]

A biogas plant is fed with agricultural substrates at an average organic loading rate of 6 kgVS per m3 fermenter volume per day and substrates with relatively high nitrogen content. This situation results in a below‐average methane yield, so the aim is to increase the substrate efficiency. An analysis of the actual condition of the plant was performed and compared with reference values. A dynamic simulation model of the biogas plant was created and adjusted with data over an operating year. The model adjustment provided a good approximation of the simulation results to the key operating variables and thus allows the evaluation of different operating variations. The effect of various measures was analyzed by simulation and it showed a potential increase in substrate efficiency of up to 15 %. [ABSTRACT FROM AUTHOR]

Simple Summary: The extensive use of animal wastes as fertilizers, often in an uncontrolled manner, may cause the spread of zoonotic diseases as they provide a nutrient-rich environment for pathogens. This study aims to determine the impact of the methane fermentation process carried out in two agricultural biogas plants, which differed in the type of substrates used (pig slurry from a maternal farm versus pig slurry from a fattening farm), on the efficiency of sanitization of biomass. The obtained results lead to the conclusion that the effectiveness of biomass sanitization is significantly higher when pig slurry from a fattening farm is used as a substrate, which offers a clear recommendation for the location of biogas plants in their vicinity. Large-scale pig farming is associated with the production of large amounts of animal excrement, which, after processing into the form of, e.g., slurry, are managed on agricultural land as natural fertilizers. The utilization of pig manure on agricultural land in an excessive and uncontrolled manner may pose a threat to zoonoses due to the significant amounts of potentially pathogenic microorganisms within its content. This study aims to determine the impact of the methane fermentation process carried out in two agricultural biogas plants on the efficiency of sanitization of pig slurry, input biomass, and digestate. The biogas plants differed in terms of the substrate used; one used pig slurry from a maternal (breeding) farm (BP-M), and the other utilized pig slurry from a fattening farm (BP-F). The physicochemical analyses showed that the slurry, input biomass, and digestate from the BP-F were characterized by a significantly higher contents of organic dry matter, ash, and ammonium nitrogen than the slurry, input biomass, and digestate from the BP-M. The parameters of the methane fermentation process, including temperature and pH, reached higher values in the BP-F compared to the BP-M. The microbiological analyses led to the conclusion that the efficiency of sanitization of input biomass, including pig slurry, was significantly higher in the BP-F compared to the BP-M. Due to the above findings, locating biogas plants near pig fattening farms should be recommended. [ABSTRACT FROM AUTHOR]

In a developing country such as Pakistan, adopting biogas technology is a complicated process. The government has taken several steps to address energy issues by increasing biogas facilities. This research seeks to identify the major barriers to the deployment of biogas plants. Respondents were selected using the snowball sampling method. As a result, 79 adopters of biogas plants participated. Utilizing a structured questionnaire, primary data were collected. Hypotheses were evaluated using partial least squares structural equation modeling (PLS-SEM). Study results demonstrate that all influencing factors are favorably associated with implementing biogas technology, minimizing energy crises, and achieving cost-cutting objectives. In addition, the findings show that properly reducing economic and governmental barriers, encourage farmers to use biogas plants productively and substantially. To build biogas facilities, the government should adopt an economic strategy, owner training, day-to-day operations, and professional technical assistance. [ABSTRACT FROM AUTHOR]

Poland has a large potential for biogas production from agricultural sources and food waste. This potential is still poorly used. There are many reasons for this state of affairs. We can indicate both the policy of the state towards renewable energy sources (RES) with a small amount of energy from biogas contracted at auctions, investment risk, and especially low return on investment in the absence of investment support. An important reason is also the limited state budget. The purpose of this work was to determine the endogenous factors that determine ROE, the direction of the impact of these factors, as well as the strategy of biogas plants in shaping the ROE level. The DuPont model was used in the analysis of ROE changes. We used the deviation method to determine the impact of the various factors on ROE. Against the background of the energy sector in Poland, the value of ROE in the examined biogas plants should be considered satisfactory, and in 2020 it was, on average, 13.9%. The decrease from 17.2% in 2019 occurred despite the increase in energy prices and the increase in the net profit margin (NPM). It resulted from the reduction of ROE's financial leverage through external capital. A high level of debt characterized the examined biogas plants, and the pursuit of risk reduction and debt reduction negatively impacts on ROE. This may indicate the need for state investment support at the plant construction stage or low-interest investment loans to develop biogas plants. In addition, using only price guarantees under the feed-in tariffs, with dynamic changes in costs, may bring the industry a relatively high investment risk compared to other RES, where the operational costs during the lifetime are low, as it is in PV or wind systems. [ABSTRACT FROM AUTHOR]

The economic management of lignocellulosic biomass from semi-natural grasslands is now a challenge across Europe. The abandonment of mowing these grasslands leads to the gradual degradation of these ecosystems. This study investigates how chemical and biological factors affect the suitability of biomass from abandoned grasslands for biogas production. We sampled 30 mown and 30 abandoned grassland sites in the Sudetes Mountains (Poland and Czechia). The cover contribution of short herbs was found to be significantly higher in mown grasslands (p < 0.001), while that of tall herbs was more prevalent in abandoned grasslands (p < 0.01). The specific biogas yield (SBY, NL kg−1 volatile solids) is negatively affected by an increased percentage of herbs in the biomass of mown and abandoned grasslands. This is due to the inhibitory effect of herbs on biodegradation, the increase in lignin content and the decrease in cellulose. This study highlights the importance of individual plant species in assessing grassland biomass for area biogas yield (ABY, m3 ha−1) and provides new insights into a field that has not yet been extensively investigated. In mown grasslands, ABY was most positively correlated with grass species (Arrhenatherum elatius , Trisetum flavescens and Festuca pratensis). In abandoned grasslands, the ABY was most correlated with herbaceous species (Galium aparine , Urtica dioica and Chaerophyllum aromaticum) and grasses (A. elatius and Elymus repens). Mown grasslands had significantly higher species richness (p < 0.001) compared to abandoned grasslands, but the number of species sampled did not correlate with SBY and ABY. This study contributes to the development of a sustainable bio-economy by highlighting the need for efficient use of grassland biomass. This approach helps protect semi-natural ecosystems and facilitates sustainable management of renewable resources. • Certain grassland plant species significantly impact area biogas yield. • Species richness has no negative effect on specific and area biogas yield. • Grassland management maintains an appropriate ratio of herbs to grasses. • Biogas production from hay can help restore abandoned grassland. [ABSTRACT FROM AUTHOR]

[Display omitted] • Analyzed 75 biogas plant accidents (occurrences) globally from 1990 to 2023. • Identified occurrences' common causes and results and suggested preventive measures. • Correlation screened factors related to occurrences, their likelihood, and severity. • Causes are component fail > maintenance > NaTech > equipment > operation > No PPE. • Explosions are the most common accident type, forming 69.3% of all occurrences. Biogas plants numbers are increasing worldwide, but their safety record is rarely investigated. This paper analyzes 75 occurrences of various types of accidents in biogas plants worldwide between 1990 and 2023. The study comprehensively reviewed accident reports and research literature with input from plant operators and safety experts. We aim to identify the common causes and consequences of accidents (occurrences) and suggest preventive measures to improve safety. The occurrences' primary causes were component failure > maintenance error > natural and technological disasters (NaTech) > equipment failure > operational error > no personal protective equipment (PPE). The most common occurrences were gas explosions 69.3%, toxic gas releases (biohazard) 21.3%, asphyxia (biohazard) 4%, malfunctioning (electric and mechanical hazard) 2.7%, and fires 2.7%. The accident consequences ranged from minor injuries (76) to fatalities (51) and extensive property damage. Lack of PPE and gas pipelines (mechanical and biohazards) correlated positively and significantly (R2 = 0.70), while operational errors and asphyxia (biohazard) scenarios correlated positively and moderately (R2 = 0.55). The plant design, operating procedures, and maintenance practices strongly influence the occurrences' likelihood and severity. This study provides valuable insights for stakeholders, researchers, and policymakers interested in promoting biogas' safe and sustainable development. Future studies should investigate the relationship between plant size and accident frequency and assess the effectiveness of safety management and risk assessment methodologies in mitigating such occurrences. [ABSTRACT FROM AUTHOR]

Abstract The aim of this research paper is a complex assessment of the efficiency of power plants in Russia, the basis of their techno-economic processes and indicators and the development of recommendations for their practical use and improvement. Capital expenses for SWH plants with a drain-down system are 1,4-1,6 times lower than traditional SWHs with circulation systems, and their payback period does not exceed 5-5,7 years. Biogas that is obtained from specialized plants of medium and high-power costs $15,000-60,000 per cubic meter. But the price of biogas produced in low energy power plants is about $80,000-270,000, which is cheaper than natural gas. So, the use of biogas is economically justified at the moment.

The present study evaluated the potential of a self‐resilient rural bio‐energy model using a case study from a village in Uttar Pradesh, India. A total biogas potential of 400 329 m3/year was estimated from area using agricultural residues and livestock wastes, thus capable of establishing biogas plants in a centralized (20 to 100 m3) or decentralized (2 to 20 m3) manner. For the three scenarios were considered in this study, i.e., (I) combined electricity and thermal energy generation, (II) for direct cooking, and (III) according to energy requirements, a maximum electricity generation and thermal energy potential were estimated to up to 800 658 and 1 200 988 kWh. A maximum amount of 162 646 kg.year–1 of firewood, 443 190 kg.year–1 of dung cake, 70 996 kg.year–1 of charcoal and 13 713 kg of liquified petroleum gas could be replaced using produced raw biogas, which is even higher if the biogas is upgraded. In the third scenario, a maximum surplus amount of 169 894 m3.year–1 of raw biogas and 221 969 m3.year–1 of upgraded biogas are available if all the available wastes are co‐digested. Vast cost opportunities and greenhouse gas emission reduction could result from replacing conventional cooking fuel and chemical fertilizers with organic fertilizer, contributing to the local circular economy. Eventually, the study proposes and discusses a self‐resilient bio‐energy model comprising energy demand fulfillment, sustainability, and a circular economy for rural India. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Accurately characterizing the substrate used in anaerobic digestion is crucial for predicting the biogas plant's performance. This issue makes particularly challenging the application of modeling in codigestion plants. In this work, a novel methodology called substrate prediction module (SPM) has been developed and tested, using virtual codigestion data. The SPM aims to estimate the inlet properties of the substrate based on the reverse application of the anaerobic digestion model n1 (ADM1). The results show that, while the SPM can estimate some properties of the substrate based on certain output parameters, there are limitations in accurately determining all required variables., Competing Interests: The authors declare there is no conflict., (© 2024 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY-NC-ND 4.0), which permits copying and redistribution for non-commercial purposes with no derivatives, provided the original work is properly cited (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Biodegradable waste from households, companies, and gastronomy is not utilized in large Polish agglomerations for the production of biogas. Determining the biogas production potential in a selected agglomeration will enable the implementation of circular economy goals and sustainable development objectives. Once appropriate odor neutrality standards are met, biogas plants could be constructed around large cities, supplying both energy and heating systems to nearby housing estates or production facilities. This article aims to assess the potential of biodegradable municipal waste collected in a large city for the production of energy in specialized municipal biogas plants. The following analytical study focuses on Krakow and its surrounding municipalities. Because of its geographical location, Krakow is exposed to smog, and every action limiting the usage of carbon-based materials for heating will have a positive impact on the air quality. A biogas plant powered by municipal waste would present a viable opportunity to limit urban smog. It is also crucial that a biogas plant can store energy as it is equipped with methane tanks. Both renewable and other energy sources are still awaiting functional technical solutions that would allow for optimal energy storage.

Changes in the approach to using waste as resources will be a necessity in the coming years. It is due to the transformation of the linear economy into a circular model and many regulations concerning waste management in the European Union countries. The article deals with the important issues of segregation and management of biodegradable waste, which are still unused energy potential. The aim of the study was to investigate the amount of this fraction of waste generated by sample households as well as the problems and barriers related to their storage and collection. The article takes into account the economic, environmental and social conditions that constitute the basis of sustainable development and are very significant for the idea of the circular economy. The minimizing and proper management of the fraction of municipal and biodegradable waste could achieve a greater economic benefits with simultaneous benefits for the environment, protecting its components and human health. [ABSTRACT FROM AUTHOR]

Large-scale pig farming is associated with the production of large amounts of animal excrement, which, after processing into the form of, e.g., slurry, are managed on agricultural land as natural fertilizers. The utilization of pig manure on agricultural land in an excessive and uncontrolled manner may pose a threat to zoonoses due to the significant amounts of potentially pathogenic microorganisms within its content. This study aims to determine the impact of the methane fermentation process carried out in two agricultural biogas plants on the efficiency of sanitization of pig slurry, input biomass, and digestate. The biogas plants differed in terms of the substrate used; one used pig slurry from a maternal (breeding) farm (BP-M), and the other utilized pig slurry from a fattening farm (BP-F). The physicochemical analyses showed that the slurry, input biomass, and digestate from the BP-F were characterized by a significantly higher contents of organic dry matter, ash, and ammonium nitrogen than the slurry, input biomass, and digestate from the BP-M. The parameters of the methane fermentation process, including temperature and pH, reached higher values in the BP-F compared to the BP-M. The microbiological analyses led to the conclusion that the efficiency of sanitization of input biomass, including pig slurry, was significantly higher in the BP-F compared to the BP-M. Due to the above findings, locating biogas plants near pig fattening farms should be recommended.

The energy efficiency of existing biogas plants (BGP) can be improved using solar energy. At present, more than half of the thermal energy generated by solar collectors in solar biogas plants remains unclaimed for directly covering the technological needs of biogas plants. A schematic diagram of a bioreactor plant with two bioreactors has been developed, which allows, regardless of the seasonal and daily irregularities in the supply of solar energy, to maximize the full potential of the thermal energy generated by solar collectors to ensure all the energy consumption of the technological scheme of fermentation of the feedstock. One bioreactor is fully operational all year round and the second during a period when the amount of thermal energy generated by solar collectors exceeds the total level of thermal energy required to compensate for all energy costs for biogas production in the first bioreactor. The connection (or disconnection) of the second bioreactor is carried out by a thermocontroller with servo drives installed on the pipelines for the circulation of the coolant, the supply of a daily dose of the raw material substrate to the bioreactor, and the discharge hatch into the liquid fertilizer tank. The round-the-clock maintenance of the optimal thermal mode of biomass fermentation in each bioreactor during periods of absence of solar energy is ensured by supplying the thermal energy of the discharge of a phase-transition heat accumulator installed in a reservoir with a liquid around each bioreactor. Using the example of raw materials—cattle manure (cattle) with a thermophilic mode of fermentation—the method of calculating the optimal values of the parameters of each bioreactor of a bioreactor, the area of solar collectors, and the amount of heat storage material is considered. Implementation of the proposed biogas plant makes it possible to reduce the area of solar collectors by more than two times and by 25% the total cost of the main biogas units. [ABSTRACT FROM AUTHOR]

Wind and solar power are already the major pillars of renewable power generation in Germany and will become even more dominant in the future. At the same time, dispatchable power plants phasing out. The expected increase of fluctuations in the residual load could be partial balanced by flexible bioenergy. However, there is currently no assessment approach for quantifying the systemic GHG impacts for flexible bioenergy generation. Based on the merit order concept, we develop an empirical approach to systemically assess the GHG emissions impact for electricity generated by flexible bioenergy plants. We estimate price response functions using the historical data of market prices and feed-in time series for the different forms of dispatchable non-renewbale dispatchable generation (NRDG). By calculating the expected NRDG based on these functions, and using specific emission factors, we are able to estimate the net impact for a switch from invariable to flexible bioenergy generation. The calculated net impact ranges from −20 to −36 g CO 2eq per kWh, which is equivalent to a benefit of −10% to −18% respectively for an average carbon footprint of 200 g CO 2eq per kWh. The calculation tools are written in Python and freely accessible on ZENODO and GitLab. [Display omitted] [ABSTRACT FROM AUTHOR]

Biogas energy has been introduced into Central and Eastern European countries (CEECs) through various incentives after their accession to the European Union in 2004. This paper contributes to an understanding of the determinants, challenges and perspectives of agricultural biogas plants in three CEECs (Poland, Slovakia, Czech Republic). Using a combination of quantitative (surveys) and qualitative (semi-structured interviews) methods, it particularly addresses varieties in public support for biogas sectors, how the relationships between biogas plants as new energy entities and their locations in rural peripheries are constructed, and how the operation of biogas plants influences local rural development. We found that as a result of various agriculture and agricultural policies in Poland, Slovakia and the Czech Republic in the second half of the 20th century, the preconditions for the incorporation of agricultural biogas plants into agriculture and rural space generally differ significantly. While in the Czech Republic and Slovakia agricultural biogas plants were usually established within large-scale agricultural farms, in Poland these are rather located off-farm. The most profound challenge for today’s biogas plants in all the CEECs studied lies in the transition from direct public incentives to a more self-sufficient business-oriented model focused on cooperation, participation and the involvement of local stakeholders in decision-making, as well as the energy utilization of locally generated agricultural waste and biowaste from households. By accommodation of these principles, agricultural biogas plants in CEECs might become a more useful and sustainable element of the rural energy transition.

The agricultural and food sector accounts for substantial volumes of organic waste (such as livestock excreta, meat offals) considered as onerous on the environment. The above decomposes formulating methane, carbon dioxide and hydrogen sulphide in anaerobic conditions. Methane produced in digester chambers of a biomass plant (called biogas) may be applied for the production of electricity and heat, powering of vehicles as well as injections into gas networks. Biogas is one of the renewable sources of energy. In the light of the EU's sustainable development and climate neutrality policies, increasing the share of renewable sources in overall energy consumption is a priority for the Member States. For this reason, the article examines one of the renewable energy sectors in Poland, which is agricultural biogas production. The main attention was focused on agricultural biogas plants. Most often used substrates for biogas production, the dependence of biogas plant location on the population living in particular regions (voivodships) and the development of agriculture in their territories were analysed. The main purpose of the article was to indicate the reasons for the failure of the agricultural biogas plant construction program in Poland. Literature and document analysis were performed, interviews with waste producers as well as owners of agricultural biogas plants were carried out, and SWOT analysis was prepared.

For the existing biogas plants (BGP) in Germany, the period of the public support scheme begins to end in 2021. From a technical point of view, essential components have an operational life span of more than 20 years and allow for an extended operation. However, a profitable extension would require suitable follow-up concepts and depends on the underlying plant-specific setup, the regional conditions, as well as the regulatory and economic framework. Based on an expert evaluation, four promising follow-up concepts were identified in a multistage process consisting of expert interviews, workshops, and an online survey. These follow-up concepts are “Basic flexibilization,” “Substrate change,” “Seasonal flexibilization,” and “Biomethane upgrading.” They were assessed with a plant-specific biogas repowering model for a heterogeneous data set of 2,508 BGPs and were compared in three scenario frameworks to derive robust development paths. To capture the heterogeneity of the existing BGPs in Germany, the model was developed further regarding regional parameters such as power output, substrate mix, and emission factors. Across all the scenarios, “Seasonal flexibilization” proves to be the most promising follow-up concept for more than 50% of the BGPs. This is followed by “Substrate change,” which is particularly suitable for larger BGPs with high shares of energy crops and no heat utilization. Biomethane upgrading is usually the second choice compared to participation in extended public support schemes for electricity production. However, it is the only concept that is profitable under current market conditions due to the high CO2-quota prices in the German fuel sector. The development pathways also show a significant potential to increase the net GHG reduction, which on BPG average can be nearly doubled. Our approach shows that the interplay of the heterogeneous BGP structure, the applied economic decision variable, and the nonuniform framework conditions in different energy markets is of crucial importance when assessing similar biogas markets, identifying robust follow-up pathways, or designing framework policies.

Poland has a large potential for biogas production from agricultural sources and food waste. This potential is still poorly used. There are many reasons for this state of affairs. We can indicate both the policy of the state towards renewable energy sources (RES) with a small amount of energy from biogas contracted at auctions, investment risk, and especially low return on investment in the absence of investment support. An important reason is also the limited state budget. The purpose of this work was to determine the endogenous factors that determine ROE, the direction of the impact of these factors, as well as the strategy of biogas plants in shaping the ROE level. The DuPont model was used in the analysis of ROE changes. We used the deviation method to determine the impact of the various factors on ROE. Against the background of the energy sector in Poland, the value of ROE in the examined biogas plants should be considered satisfactory, and in 2020 it was, on average, 13.9%. The decrease from 17.2% in 2019 occurred despite the increase in energy prices and the increase in the net profit margin (NPM). It resulted from the reduction of ROE’s financial leverage through external capital. A high level of debt characterized the examined biogas plants, and the pursuit of risk reduction and debt reduction negatively impacts on ROE. This may indicate the need for state investment support at the plant construction stage or low-interest investment loans to develop biogas plants. In addition, using only price guarantees under the feed-in tariffs, with dynamic changes in costs, may bring the industry a relatively high investment risk compared to other RES, where the operational costs during the lifetime are low, as it is in PV or wind systems.

This study aimed to evaluate the potential for electricity generating of biogas from anaerobic digestion of sewage and sewage sludge in Wastewater Treatment Plants (WWTPs) in the state of Minas Gerais, Brazil. Four different methodologies for determining the volume of biogas produced were considered. Estimates of biogas production used actual data of the volume of treated sewage and population reached by this WWTP with sewage as presented in a report by the local authority. The results indicate some discrepancies between the methodologies employed, but in general, they all suggest a potential of electric power generation at the same order of magnitude. The most divergent results were those in which the methodologies were applied to municipalities with a population of over 250,000 inhabitants. [ABSTRACT FROM AUTHOR]

It has been shown that the power demand-oriented operation of biogas plants contributes to the challenges of future energy systems with high shares of fluctuating renewable energies. This flexibilisation is usually short-term and can improve profitability. Long-term seasonal flexibilisation could further overcome present low heat utilisation rates due to the low heat demand of district heating in summer and constant biogas production across the year. To assess the benefits of seasonal flexibilisation for different biogas plants, we apply an existing model approach for analysing biogas repowering and optimising the combined heat and power (CHP) despatch. Plant-specific constraints and historical spot market data are used to determine power revenues, heat utilisation rates, greenhouse gas emissions and the profitability of the biogas plants. For different setups of CHP units and heat demand levels, the seasonal operation mode is compared with the non-seasonal reference mode. The economic benefit of seasonal flexibilisation is on average 10 €/MWhel when comparing the same rated power output and varies with plant size and CHP-setup. Increases in the heat utilisation rate are the main driver. Benefits increase with additional installed CHP capacities and rising heat prices. As gas production changes over the year, higher CHP capacities increase flexibility in winter and align the power market revenues of seasonal and non-seasonal operation. Very high heat prices even offset economies of scale. However, seasonal flexibilisation does not allow economic operation in Germany under current market conditions. The dependence on other sources of revenues and extended support schemes therefore remains.

The increasing demand for electrical energy and environmental concerns associated with conventional means of its generation drive the interest in alternative fuels. Biohydrogen, widely considered as fuel of the future, is one of such alternatives. To date, research results suggest that biological routes are the most promising for hydrogen production, especially dark (hydrogen) fermentation. Hydrogen fermentation can be performed with agricultural and food processing wastes as substrates. In this paper the most important factors influencing dark fermentation are reviewed and analyzed. These are: pH, partial pressure, temperature, and retention time. The biohydrogen generation efficiency is also presented with respect to different substrates. It should be also pointed out that many factors are still unknown; thus, the process requires conducting further research.

Digestate from biogas plants, formed by dewatering anaerobically stabilized sludge, is characteristic of high concentrations of phosphates and ammonia nitrogen suitable for further use. Phosphorus is an element widely used to produce fertilizers, and because of its continually shortening natural supplies, recycling of phosphorus is gaining on significance. Both phosphorus and nitrogen are important elements and their presence affect the quality of water resources. Both elements can contribute to eutrophication. At the same time, both phosphorus and ammonia nitrogen, are important elements for agricultural production, and therefore greater demands are being made on the effort to connect sewage treatment processes and the process of recycling of these nutrients. A suitable product of phosphorus and ammonia nitrogen are phosphates in the form of a structurally-poorly soluble precipitate of magnesium ammonium phosphate (struvite). This form of slowly decomposing fertilizer is distinguished by its fertilizing abilities. Compared to direct use of digestate as a fertilizer, struvite is more stable and can gradually release ammonia nitrogen for a long time without unnecessary losses. In the reported experiments, the precipitation efficiency of the recycling of ammonia nitrogen and phosphorus from the digestate liqour (liquid discharge from digestate) was, at a stoichiometric ratio of Mg2+: NH4+: PO43− (3.2: 1: 0.8) and a stirring time of 15 minutes, 87 % for ammonia nitrogen ions.

• Biogas industry is an important part of Polish bioeconomy. • Anaerobic digestion of sewage sludges enables new added-value bioproducts to be obtained. • Eco-innovative fertilizers developed and produced from valorized sludges. • Optimized bio-treatment of eutrophic digester liquors is necessary and advantageous. • Elaborated novel biotechnologies ensure closing the organic waste management cycles. Bio-based solutions are expected to ensure technological circularity in priority areas such as agriculture, biotechnology, ecology, green industry or energy. Although Poland, unlike the other EU member states, has not yet adopted a precise political strategy to promote bioeconomy, it has taken several actions to enable smart, sustainable and inclusive growth. This goal can be achieved by developing selected bioeconomy-related areas such as the biogas industry together with novel technologies implemented to optimize treatment of municipal sewage and management of organic solid waste. Here, the relatively strong status of the Polish biogas sector is presented. The widely used practice of sewage sludge biomethanation has led to construction of numerous complex installations combining biological wastewater treatment plants with anaerobic digesters. Based on physico-chemical processing of biostabilized sludges, a novel method for efficient granulated soil fertilizer production is elaborated, in line with the concept of circular economy and the notion of "waste-to-product". It is also shown that anaerobic fermentation of sewage sludges can be optimized by co-digestion with properly selected co-substrates to increase bioprocess yield and improve the resultant digestate fertilizer quality. The problem of post-fermentation eutrophic sludge liquors, environmentally hazardous waste effluents requiring proper treatment prior to discharge or field application, is addressed. Attempts to optimize biological treatment of digestate liquors with complex microbial consortia are presented. The Polish innovations described show that the "zero waste" path in circular bioeconomy may bring advantageous results in terms of transformation of waste materials into commercial, added-value products together with recovery of water resources. [ABSTRACT FROM AUTHOR]

Renewable energy can be used from several natural sources, which are capable of wind, sun, water, geothermal springs, or biomass. Energy from these sources is clean, safe and inexhaustible. The use of alternative sources is becoming part of all realistic scenarios and promotes sustainable development and energy security in Europe as well. Renewable energy sources form a relatively significant part of primary energy sources in many countries. Thanks to the undeniable advantages of their use, they form another higher share of combined energy production in Slovakia. In addition, the correct location of renewable energy sources can be a key element in the development of individual regions, which can contribute to achieving better social and economic cohesion in the country. Given these obvious environmental and economic benefits, efficient use of renewable energy sources is receiving increasing attention and support from responsible officials and the general public around the world, including Slovakia. The main goal of this paper was to evaluate the use of renewable resources in Slovakia with a focus on biogas plants. We also evaluate the position of Slovakia within the EU in this area and find out what is the current situation of biogas plants in Slovakia. [ABSTRACT FROM AUTHOR]

The large amount of organic waste resulted from the large urban agglomerations is an important source of landfill gas and consequently represents an important factor in the climate changing pollution effect. Although there are consistent efforts to reduce the volume of organic waste or to process it in a way which generate less landfill gas, there it is more work to be done in order to solve this problem. This article presents the work conducted to convert a biogas plant originally designed to use corn silage into a biogas plant which uses agri-food waste. Another important aspect presented in this article is the research on improving the qualitative parameters of biogas and the technical modifications conducted on the initial design to achieve a double quantity of biogas. [ABSTRACT FROM AUTHOR]

A growing population, technological progress and economic development result in a constant increase in energy demand. Energy is mostly obtained from fossil energy resources such as coal, natural gas, and crude oil. Burning them leads to air pollution with greenhouse gases (CO2, CH4, NH3 and N2O) and dust (PM2.5 and PM10). They are recognized as the cause of global warming and air pollution. Wind, water, solar and biomass energy are used to eliminate harmful emissions. The latter may come from special plant crops or from biodegradable waste from farming, animal husbandry, the agrifood industry and households. These wastes are transformed into biogas in biogas plants, the basic ingredient of which is methane. Most often, biogas is burned in a cogeneration process, providing electricity and heat. After purification of admixtures, it can be injected into the high-methane gas network or converted into hydrogen in the steam reforming process. In this way, environmentally harmful waste becomes a raw material for energy production, which is an example of a circular economy. The article discusses the functioning of biogas plants in selected EU countries. The current biogas production in Poland was assessed and compared with the production potential of dairy farms. The aim of this article was to show that the production of biogas reduces the emission of greenhouse gases into the atmosphere and the electricity produced from it is not burdened with the cost of purchasing CO2 emission allowances applicable in the EU.

Biogas energy has been introduced into Central and Eastern European countries (CEECs) through various incentives after their accession to the European Union in 2004. This paper contributes to an understanding of the determinants, challenges and perspectives of agricultural biogas plants in three CEECs (Poland, Slovakia, Czech Republic). Using a combination of quantitative (surveys) and qualitative (semi-structured interviews) methods, it particularly addresses varieties in public support for biogas sectors, how the relationships between biogas plants as new energy entities and their locations in rural peripheries are constructed, and how the operation of biogas plants influences local rural development. We found that as a result of various agriculture and agricultural policies in Poland, Slovakia and the Czech Republic in the second half of the 20th century, the preconditions for the incorporation of agricultural biogas plants into agriculture and rural space generally differ significantly. While in the Czech Republic and Slovakia agricultural biogas plants were usually established within large-scale agricultural farms, in Poland these are rather located off-farm. The most profound challenge for today's biogas plants in all the CEECs studied lies in the transition from direct public incentives to a more self-sufficient business-oriented model focused on cooperation, participation and the involvement of local stakeholders in decision-making, as well as the energy utilization of locally generated agricultural waste and biowaste from households. By accommodation of these principles, agricultural biogas plants in CEECs might become a more useful and sustainable element of the rural energy transition. [ABSTRACT FROM AUTHOR]

Abstract The number of agricultural biogas plants has been increasing in the past decades in some European countries. Digestates obtained after anaerobic digestion (AD) of manure are usually spread on agricultural land; however, their hygiene status regarding pathogens posing public health and/or animal health challenges has been poorly characterized up to now in France. In this study, three replicates of manure and digestate were collected from five farm biogas plants receiving animal manure in order to assess the occurrence and concentrations of sporulating (Clostridium botulinum, Clostridioides difficile, Clostridium perfringens) and nonsporulating (Listeria monocytogenes, thermotolerant Campylobacter spp., Salmonella, Escherichia coli, enterococci) bacteria. Concentrations of E. coli, enterococci, and C. perfringens in digestates ranged from 102 to 104, 104 to 105, and 7 × 102 MPN/g and from 1.3 to 3 × 102 MPN/g, respectively. Thermotolerant Campylobacter, detected in all the manures, was only found in two digestates at a concentration of cells ranging from

In a two-year vegetation field experiment, the fertilizing effects of by-products from the agricultural biogas plant—a solid phase of digestate (SPD) and a liquid phase of digestate (LPD)—were studied and compared with mineral fertilization (NPK) on the biomass yield, content and nutrient uptake by Cannabis sativa L. plants. Furthermore, the agrochemical properties of the soil were evaluated at the end of the experiment. In all variants of the experiment, a uniform nitrogen dose of 150 kg/ha was applied. The dose of other nutrients corresponded to the fertilizer used. The biggest fertilizing effect, and therefore the greatest hemp biomass yield and nutrient uptake, was demonstrated when combining SPD and LPD fertilization in one treatment. However, the differences were statically insignificant (p ≤ 0.05). The applied amount appeared to be sufficient for the nutrition of hemp plants and was comparable to mineral fertilization. The distribution of nutrients between leaves and stems varied depending on the nutrient monitored. Analyses after the end of the experiment did not show different contents of accessible nutrients in the soil on the studied variants. The content of accessible risk elements in the soil was not affected by the application of the SPD and the LPD. The experiment showed that cannabis plants are able to achieve equivalent biomass yields (8.68 t/ha) using the combination of LPD and SPD by-products from a biogas plan compared to commercial mineral fertilizer (7.43 t/ha). Therefore, we can recommend a split application of LPD and SPD as a suitable alternative to mineral fertilization. Due to prolonged nutrient release from SPD, we can expect a smaller negative environmental impact than current fertilization practices.

A 1200‐m3 full‐scale biogas plant treating highly polluted wastewater (WW) from the cleaning of tank cars transporting food and fodder is working stably and efficiently despite the WW is constantly varying in strength and composition, is easily acidifying, and low in alkalinity. Na2CO3 has to be added to maintain the digester alkalinity and the digester pH at defined values due to softened water used for car tank cleaning. Monitoring volatile organic acid concentration and controlling the alkalinity in the digester are essential for maintaining the digestion process stability. Biogas production is adapted to the demand by a modulated feeding regime. The drastic modulation of feeding is possible due to the moderate organic loading of the plant along with the high average hydraulic retention time. [ABSTRACT FROM AUTHOR]

Acquiring data from biogas plants can be done by accessing the data stored in the programmable logic controller (PLC) of the biogas plant, which is responsible for issuing control commands to the hardware of the plant. Eight plants of three different manufacturers, with a total of 1370 data points, were analyzed to find similarities which could lead to a reliable but manufacturer‐independent readout of sensor and control values. The expectation was plants of the same vendor being very similar but analysis showed that only minor similarities exist between plants of the same manufacturer. Even less similarities are found when it comes to plants from different manufacturers. [ABSTRACT FROM AUTHOR]

The two‐year monitoring (732 days) of operational methane emissions from pressure relief valves of the gasholders from an agriculture biogas plant is presented. The monitoring aimed at the identification of major factors influencing the emissions and the effect of mitigation measures deduced from the results. The determined emission factors from the valves of both gastight covered digesters are 1.8 and 0.6 % CH4 loss for the first and second year of investigation, respectively. The emission rates strongly depend on seasonal factors like (fast) changes in ambient air temperature as well as the capacity utilization of the combined heat and power and the operation of the gasholders. The implemented mitigation measures significantly reduced the measured methane emissions in the second year of the investigation. [ABSTRACT FROM AUTHOR]

Abstract Flexible power provision from biogas can significantly contribute to energy systems with high shares of renewables. However, the characteristics and demands for this flexibility are not clearly defined or measured. In this paper eight indicators are defined to shape "flexibility" and perform a downstream investigation of eight research projects focusing on flexible energy provision of biogas plants. The indicators are structured in three dimensions (1) velocity (ramps) by which the system can be modulated, (2) power range (bandwidth) and (3) duration for specific load conditions. Based on these indicators bottlenecks for the flexibility potential were identified. One crucial result shows that short-term flexibility of biogas plants is mainly driven by properties of the combined heat and power unit (velocity and bandwidth). The long-term flexibility depends mainly on gas storage, mode of operation and ability for modulation of the target gas production. Highlights • Development of eight indicators to measure flexibility performance of biogas plants. • Application of flexibility indicators to nine research projects. • Sensitivity analysis for flexibility indicators based on a simulated biogas plant. • Interpreting and explaining interactions of flexibility factors and the developed indicators. • Identifying bottlenecks and trade-off for flexibilization of biogas plants. [ABSTRACT FROM AUTHOR]

VIVAM AGROTECH is in the field of solid waste processing such as Composting, Vermicomposting, Mechanical Compost and Biogas since last Ten years and in city Solid Waste Management for last Five years. All these technologies developed by VIVAM AGROTECH are most suitable for city waste management and sustainable development of the city. VIVAM AGROTECH is into the business of converting waste to energy. They have plants to treat Solid wastes like Municipal Solid Waste, kitchen, canteen, poultry, cow dung, food processing and agricultural wastes. They specialize in Municipal solid waste treatment plants for power generation. They have Biogas plants from 4 Kg to 400 tons waste per day. Vivam is now expanding its business in abroad. [ABSTRACT FROM AUTHOR]

Abstract Biomass is a potential energy source for the diversification of the Brazilian energy matrix. In this context, the biogas produced from the anaerobic digestion of residues is a relevant renewable resource that plays a significant role in the mitigation of environmental problems and the local generation of electric energy. This review presents the scenario of the biogas production and electricity distributed generation within the Brazilian context. Firstly, it presents an overview of the electric energy generation from biogas and the Brazilian plants that compose this electric matrix. Secondly, the main technologies to produce biogas and the possibilities of its use, followed by the comparison of technologies for distributed generation of electric energy from biogas in the Brazilian market. To illustrate the application of biogas technology, this paper presents a case study of a biogas plant operation and its connectivity to the grid, the Colombari Farm. The information presented here aims to enhance and to foment the recovering of biomass residues to produce biogas via anaerobic digestion and its utilization to generate electricity. Although the case study considers a specific plant in Brazil, the information and results presented can be applied to others areas of the country or regions of the world, so contributing to promote the expansion of biogas plants to generate electricity. Finally, a future perspectives section describes the practical implications of the biogas production and electricity generation in rural and urban areas and its contribution to the implementation of Brazilian environmental and social policies. This review also is useful to support the research development of biogas for electricity production. Graphical abstract fx1 Highlights • Biogas applied Distributed Generation in the Brazilian Market. • Different types of biodigesters and its biogas production. • Technologies for biogas production and electric power generation. • Study of the first biogas generation plant: Colombari Farm at Parana, Brazil. [ABSTRACT FROM AUTHOR]

The introduction of biogas plants is a promising way to recycle organic wastes with renewable energy production and reducing greenhouse gas. Application of anaerobic digestate as a fertilizer reduces the consumption of chemical fertilizers. In this study, the survival of pathogenic bacteria and plant growth promoting bacteria (PGPB) in two full‐scale biogas plants operated at mesophilic condition were investigated. Feedstock and anaerobic digestate samples were collected from biogas plants and bacteria load in samples were detected using standard dilution plate method. Pathogenic bacteria were reduced to not detected level through mesophilic digestion tank except for Campylobacter. However, it could be reduced by 98.7% through a sterilization tank. Bacillus was detected at 8.00 and 7.81 log10 CFU/g dry matter in anaerobic digestates, and it was also resistant to sterilization tank. Bacillus spp. is considered to be the safe bacteria that hold remarkable abilities for promoting plant growth. The results showed that treatment at biogas plants is effective to reduce pathogenic bacteria in dairy manure, and sterilization could further reduce the sanitary risks of pathogenic bacteria relating to anaerobic digestate application. Anaerobic digestates could also be utilized as bio‐fertilizer as the high load of plant growth promoting bacteria. [ABSTRACT FROM AUTHOR]

The increasing demand for electrical energy and environmental concerns associated with conventional means of its generation drive the interest in alternative fuels. Biohydrogen, widely considered as fuel of the future, is one of such alternatives. To date, research results suggest that biological routes are the most promising for hydrogen production, especially dark (hydrogen) fermentation. Hydrogen fermentation can be performed with agricultural and food processing wastes as substrates. In this paper the most important factors influencing dark fermentation are reviewed and analyzed. These are: pH, partial pressure, temperature, and retention time. The biohydrogen generation efficiency is also presented with respect to different substrates. It should be also pointed out that many factors are still unknown; thus, the process requires conducting further research. [ABSTRACT FROM AUTHOR]

Up to the latest versions of the German renewable energy act (EEG), there had been a constant growth of new biogas plants (BGPs). After reaching a stagnation in the last years, today the focus has shifted to improving the existing BGPs. Assuming that most plants have not reached the technical end of life, the question arises on how an operation can be realized beyond the initial EEG support period of 20 years. In addition, new legal and economic conditions require the implementation of adjustments, that is, "repowering measures." Based on a method review, a plant‐specific model approach is presented to assess repowering measures for a wide range of BGPs differing in capacity, substrate mixture and agricultural structures. The techno‐economic model includes different performance indicators like levelized cost of electricity (LCOE) and temporal aspects like technical progress. Using a data set for BGPs in the state of Baden‐Wuerttemberg (Germany), results are illustrated for the different model modules and three repowering scenarios of an extended operation period of ten years. The scenarios regard different options to meet the requirements of the current EEG, namely the flexibilization and restrictions on energy crops, in comparison with a reference case. While in repowering scenarios, the number of plants decreases between 54% and 69% and the overall power capacity changes between −48% and 13% until 2035. The results further show a reduction potential in the specific area demand and GHG emission up to 12% and 24%, respectively. Technical progress, additional revenues and capacity premiums are shown to be an important factor for efficient substrate utilization, low LCOE and thereby the enabling of an extended operation period. The scenario results indicate that the agricultural areas for energy crop cultivation and the amount of manure used in BGPs will be reduced considerably, inducing new chances and challenges in the future. Due to constantly changing framework conditions, existing biogas plants in Germany are required to conduct repowering measures to continue the operation. Using a plant‐specific model approach, the impact of these repowering measures has been assessed for a wide range of plants in the state of Baden‐Württemberg. Different scenarios show that repowering can improve efficiency and reduce specific GHG emissions. Yet, under current framework conditions, the number of biogas plants is strongly decreasing. Changes in the public support system are needed if more plants should be enabled to continue their operation. [ABSTRACT FROM AUTHOR]

For flexible power generation of biogas plants and effective heat utilization, efficient heat storage technologies will play a decisive role. For this purpose, a process is being developed in the ThermoFlex project, based on controlled operation of a secondary digester in thermophilic temperature ranges after a mesophilic main digester. This allows effective, flexible heat storage in the secondary digester for digester heating and external heat utilization at an acceptable temperature level without additional storage. The process biology of the secondary digester tolerates controlled temperature variations. An overview of the application potential and design of the ThermoFlex process is given. Batch and semicontinuous fermentation tests at various temperatures are described. Flexibilization strategies for biogas plants are the key to their success in the energy transition to renewable sources. In the ThermoFlex process, controlled operation of a thermophilic secondary digester following a mesophilic main digester allows effective, flexible heat storage in the secondary digester for digester heating and external heat utilization without disturbing its process biology. [ABSTRACT FROM AUTHOR]

Three treatments were used in a two-year (2014-2015) vegetation pot experiment with kohlrabi of the cv. Moravia: (1) untreated control; (2) digestate; (3) digestate + phosphorus (P). The nitrogen (N) rate was the same in treatments 2-3. There were significant differences between years in all parameters. The weight of single kohlrabi bulbs in the unfertilised control was significantly lower in both years (33.1-46.9%) than in the digestate treatment (100%). Digestate supplemented with P (treatment 3) increased the bulb yield significantly by 11.0-14.3% compared with pure digestate (treatment 2). In both years the content of bulb nitrates (mg NO3-/kg FM (fresh matter)) was significantly the lowest in the unfertilised control (135 and 163, respectively). After digestate applications the nitrates content (mg NO3-/kg FM) increased significantly in both years, i.e. to 315-327 (2014) and to 486-509 (2015) compared to unfertilised control. In two years the content of ascorbic acid (mg/kg FM) did not differ among the three treatments (274-288 in 2014 and 311-329 in 2015). Digestates can be recommended for kohlrabi fertilisation prior to planting.

One of the greatest challenges facing the societies now and in the future is the reduction of green house gas emissions and thus preventing the climate change. It is therefore important to replace fossil fuels with renewable sources, such as biogas. Biogas can be produced from various organic waste streams or as a byproduct from industrial processes. Beside energy production, the degradation of organic waste through anaerobic digestion offers other advantages, such as the prevention of odor release and the decrease of pathogens. Moreover, the nutrient rich digested residues can be utilized as fertilizer for recycling the nutrients back to the fields. However, the amount of organic materials currently available for biogas production is limited and new substrates as well as new effective technologies are therefore needed to facilitate the growth of the biogas industry all over the world. Hence, major developments have been made during the last decades regarding the utilization of lignocellulosic biomass, the development of high rate systems, and the application of membrane technologies within the anaerobic digestion process in order to overcome the shortcomings encountered. The degradation of organic material requires a synchronized action of different groups of microorganisms with different metabolic capacities. Recent developments in molecular biology techniques have provided the research community with a valuable tool for improved understanding of this complex microbiological system, which in turn could help optimize and control the process in an effective way in the future.