Large-scale Biogas Production Research Articles

A matheuristic applied to clustering rural properties and allocating plants for biogas generation

Establishing partnerships among agro-industrial properties and selecting ideal locations for biogas plants are crucial challenges in large-scale biogas production and can influence both operational efficiency and waste management. In this context, this research proposes a new matheuristic that addresses the problems of defining a group of properties and an optimal number of groups and identifies the best allocation to the biogas plant. The group properties were defined by hierarchical and K-means cluster algorithms. The best location for the biogas plant was determined by the proposed multiobjective mathematical model. The best cluster number was decided by two strategies: (1) one that selected the closest non-dominated solutions to the ideal solution (M1) and (2) one that favored the most environmentally friendly solution (M2). The matheuristic was tested using three real databases, which yielded strategic clusters with an average daily biogas production of 544.93 m³/day (M1 and M2) for DataBase 1, 1635,156.00 m³/day (M1) and 403,497.50 m³/day (M2) for DataBase 2, and 318,662.50 m³/day (M1) and 20,479.58 m³/day (M2) for DataBase 3. This research provides an opportunity to add value to agro-industrial properties by achieving energy security and developing new business networks.

THE ROLE OF BACTERIAL AND ARCHAEA IN DETERMINING THE METABOLIC PATHWAY OF BIOGAS FERMENTATION AT LOW TEMPERATURES

The challenge in achieving large-scale biogas production still lies in the biogas fermentation process at low temperatures. Our goal was to delve into the metabolic pathway behind the formation of biogas at these lower temperatures, focusing on the dominant bacterial and archaeal communities. Employing a batch system with activated sludge inoculum at 10°C, we fermented cow manure at 12°C for 150 days. Through genetic sequencing and taxonomic analysis using OTUs from the 16S rDNA gene, we investigated bacterial and archaeal species. Correlation analysis between their abundance was conducted using Pearson correlation and t-tests via IBM SPSS Statistics. Our findings revealed a biogas production of around 0.74 L/day, with CH4 levels surpassing 0.45 L/g VS. Peak efficiency occurred between day 60 and 110, reaching its apex on day 90. Clostridium cellulovorans dominated, ranging from 13.9% to 27%, followed by Terrisporobacter petrolarius, around 16.2% to 23%. Specifically, the formation of biogas (CH4) predominantly occurred through the H2 pathway, led by significant hydrogenotrophic Archaea OTUs like Methanocorpusculum sinense (ranging from 4.95% to 37.10%) and Methanobrevibacter millerae (with relative abundances between 2.00% and 11.20%)

Invisible, intangible, irrelevant, yet inevitable? Qualitative insights into consumer perceptions of heating tariffs and drop-in renewable gases in the German domestic heating market

One of the key challenges of increasing renewable energy use is consumer demand. In the residential heating sector, where long-lived fossil-fuel systems are slow to be replaced, consumer demand for drop-in renewable gases like biomethane or Synthetic Natural Gas could play an important role in short-term decarbonization. As this sector is a major emitter of CO2 in Europe, robust green demand could be key to fulfilling the targets set in the Paris Agreement. Yet existing research focuses on the supply side and technical aspects of renewable gases, leaving the demand side and consumer preferences for these gases largely neglected. To close this gap, we conducted a qualitative study based on two empirical strands: 22 interviews with heating consumers, and a set of interviews and focus groups with 27 industry experts. The study was situated in Germany, one of the world's largest biogas producers.Our results show that choosing a heating tariff is a low-involvement decision, but one made by a complex calculus where the environmental benefits of renewable gases count positively, but large-scale biogas production and perceived energy crop monocultures count negatively. SNG is still largely unknown and regarded neutrally. Industry experts evaluate voluntary markets for renewable gases as small, cost-driven and made up of consumers accustomed to low-cost products. Our insights on consumers who have the decision-making power over their heating tariffs can help policy makers support voluntary renewable energy markets and provide energy practitioners with approaches to increasing consumer engagement with their products.

Unravelling the anaerobic digestion ‘black box’: Biotechnological approaches for process optimization

Increasing global demand for green energy has necessitated more research interest in anaerobic digestion. Due to the dual benefits of anaerobic digestion, in organic waste management and energy generation, it is rated among the best renewable energy generation options. An important challenge that limits acceptability and adoption of this technology is the quality and quantity of anaerobic digestion products, especially biogas and digestate. A practical solution to this challenge is process optimization. However, process optimization is not easily achieved due to the complexity of the microbiome driving the anaerobic digestion process, which has contributed to anaerobic digesters being considered ‘black boxes’. Unravelling the ‘black box’ would aid in fine-tuning operational conditions, process parameters, intra- and inter-phase interactions as well as rate limiting factors during each phase of the production cycle, thereby optimizing the anaerobic digestion process. To achieve this level of technological advancement, cooperation between experts that understand both the microbial processes and technological design of digesters is important. When factors are optimized, implementation of the optimized conditions through automation may prevent process errors and failures, thereby enhancing quality and quantity of anaerobic digestion products. In addition, process optimization should also reflect economic viability vis-à-vis small-scale and large-scale biogas production systems. This review provides a detailed overview of individual factors that could affect the performance of the anaerobic digestion process with critical interpretations and suggestions. This work could be employed as a good base to build integrative models or ecological indices that interrelate these factors.

Biodegradability and kinetic studies on biomethane production from okra (Abelmoschus esculentus) waste

Emerging from the energy crisis of 2008 in South Africa, climate change concerns and the global desire to reduce high ozone-depleting emissions, renewable energy sources like biogas are gaining wide acceptance in most localities for heating and electricity. The paucity of feedstock varieties is a major challenge plaguing the sustainability of this sector. Biomethane potential, biodegradability and degradation kinetics of organic substrates are essential for assessing the suitability of feedstocks for methane generation and the overall performance of the anaerobic digestion process in biogas plants. Waste from the vegetable okra (Abelmoschus esculentus) is a novel substrate; its biodegradability and degradation dynamics in biomethane production are largely unstudied, and were therefore the aims of this research. The substrate was digested for 25 days at the mesophilic condition and the biomethane potential data were recorded. Measured data of methane yield and the elemental composition of the substrate were used to fit five models (modified Gompertz, Stannard, transference function, logistic and first-order models) to predict degradation parameters and determine biodegradability of the substrate, respectively. Low lag phase (0.143 d), positive kinetic constant (0.2994/d) and the model fitness indicator (<10) showed that transference and first-order kinetic models predicted the methane yield better than did other growth functions. The experimental methane yield was 270.98 mL/gVS, theoretical methane yields were 444.48 mL/gVS and 342.06 mL/gVS and model simulation ranged from 267.5 mL/gVS to 270.89 mL/gVS. With a prediction difference of 0.03–1.28%, all growth functions acceptably predicted the kinetics of A. esculentus waste. The findings of this study offer information on this novel substrate important for its use in large-scale biogas production.
 Significance:
 
 Growing interest in biogas technology as an alternative energy source for both South African rural dwellers and industries, has mounted enormous pressure on known feedstocks, and instigated the search for novel substrates.
 Our study shows that okra waste is a viable feedstock for biogas production.
 The suitability of the first-order kinetic model over other models in predicting okra waste degradation was highlighted.

Differences in microbial key players in anaerobic degradation between biogas and sewage treatment plants

Biogas production in biogas plants (BPs) and sewage treatment plants (STPs) of industrial and municipal waste, respectively, is principally based on the same metabolic processes. Process parameters, bacterial and archaeal community composition of 16 BPs and 10 STPs with large-scale biogas production were analyzed by 16S rRNA gene amplicon sequencing to assess a common core microbiome. Both community compositions differed between plant types, and those of BPs were significantly affected by substrate, whereas STP community compositions were governed by pH. Operational taxonomic unit (OTU) richness and diversity were significantly higher in STPs compared to BPs. Microbial network analysis of the overall bacterial and archaeal community composition identified 39 generalistic OTUs for BPs and only 11 for STPs, respectively. Our findings indicate that BPs were less complex with various common key players in all plants whereas STPs were composed by a more plant-specific microbial network. Assignment of each generalistic OTU to one or more steps of anaerobic degradation corresponded to well-known syntrophic interactions as well as to potential but unknown interactions.

Life cycle assessment of large-scale and household biogas plants in northwest China

Abstract In northwest China, large-scale (modern) and household biogas production (conventional) plants are the two main methods of biogas fermentation, a promising means of livestock waste disposal and effective agricultural recycling. Differences in the operating mechanisms of the two systems result in differences in their environmental performance. In this study, detailed life cycle assessments of large-scale and household biogas production were conducted to compare their environmental performance in terms of energy use and environmental impact potential per function unit (2136 tonne/yr of manure flowing into the biogas plant). Data were collected over a two-year period (2014–2016). The results showed that the total biogas output from the large-scale digester was 1.88 times that of the household digester. Net energy output did not differ much between the two systems, due to the high energy consumption of the large-scale plant during production. The energy-use efficiency of the large-scale plant was 1.29 times that of the household plant due to the use of co-products. Higher carbon dioxide and volatile organic compound emissions from the burning of biogas in the large-scale plant caused a higher potential for global warming and photochemical oxidation. However, higher ammonia and sulfur dioxide emissions occurred in the household plant, resulting in a higher potential for eutrophication, acidification and human toxicity. In conclusion, the waste of extra biogas for heat in large-scale biogas production, and undeveloped management, emissions through poor air-tightness and lack of technical biogas purification in household biogas production are the main hotspots to improve the environmental performance.

Comparative Analysis of Single-stage and Two-stage Fermentation Systems under Various Process Conditions

A comparative study of single-stage fermentation (wet or dry) and two-stage (wet-dry and dry-wet) fermentation systems was carried out under medium temperature conditions. The effect of the length of the first wet or dry fermentation stage (5-, 10-, 15-, 20-, and 25-d) in the two-stage anaerobic fermentation was investigated. The results showed that the gas production of wet fermentation and two-stage wet-dry fermentation was better than that of the dry fermentation and two-stage dry-wet fermentation. The cumulative gas production increased gradually with increased stage conversion times for the two-stage wet-dry fermentation. The gas production for the 20-d experimental group of the two-stage wet-dry fermentation system was the best. The cumulative biogas production in the anaerobic fermentation of straw correlated significantly with the changes in the degradation rates of volatile solids, cellulose, and hemicellulose (P < 0.01). The kinetic fitting analysis showed that the Reaction Curve (RC) model was more suitable for data modeling of the single-stage wet fermentation and two-stage wet-dry fermentation with straw than the Modified Gompertz (GM) and Modified Logistic (LM) models. The results of this study provided a theoretical basis for choosing a fermentation process for large-scale biogas production with straw.

Towards a sustainable socio-technical system of biogas for transport: the case of the city of Linköping in Sweden

In this article, the development of biogas for transport in the municipality of Linköping, Sweden, is studied in order to contribute to a better understanding of the conditions for socio-technical transitions towards sustainability. Linköping municipality, 1976 [kommunfullmäktige] Motion om utredning angående eldrivna fordon. Dnr 1976.278. Using concepts from multi-level perspectives and socio-technical perspectives on system builders, the study focuses on three time periods: During the first time period (1976–1994), a niche for biogas developed amongst dedicated actors in small networks representing energy and public transport within the municipality. That is, biogas was entirely connected to the vision of a ‘green’ public transport. Second, between the years of 1994 and 2001, the biogas producing company acted as a system builder and initiated a large-scale biogas production through close cooperation in networks with other actors. As a result, biogas reached a phase of technological maturity and also gained some support from national investment programs. Finally, from 2001 the expansion of biogas became clearer as the biogas production spread into a regional arena but also reached for new customers, like personal cars. Unforeseen spin-offs like the formation of new private companies and development of research were important results of the transition. Thereby, the transition is a move towards a new socio-technical regime. A conclusion from the study is that the development of biogas was highly influenced by national support and pressure, but was mainly driven by local actors – system builders – that could steer the processes and had endurance as well as capability to mobilize resources in order to fulfill their purposes.

Spatial competition for biogas production using insights from retail location models

Biogas production is an important contemporary topic within agriculture as well as bioenergy production, both from an industrial and an academic point of view. The Danish biogas sector, which has been around for many years, is still struggling to establish itself as an economically viable energy production sector. Through a two-step approach by combining a location-allocation model with a production constrained spatial interaction model, this paper addresses the dual problem of determining optimal location and production capacity. What-if scenarios, in combination with the strategic economic analysis framework developed in this paper, facilitate the analysis and discussion of how national policies can be fulfilled.The capacity expansion of the Danish biogas sector should be centred on large-scale biogas production since large biogas plants are found to have 16% lower transportation costs than small biogas plants. Consequently, this minimizes the single most important production cost factor, transportation.The developed framework can be used and further developed in an analysis of how the spatial availability of, and competition for, different types of biomass can supplement each other in the development towards a bio-based economy.