Impact of single versus multiple policy options on the economic feasibility of biogas energy production: Swine and dairy operations in Nova Scotia

The economic feasibility of on-farm biogas energy production was investigated for swine and dairy operations under Nova Scotia, Canada farming conditions, using net present value (NPV), internal rate of return (IRR), and payback period (PP) economic decision criteria. In addition, the effects of selected environmental and “green” energy policy schemes on co-generation of on-farm biogas energy production and other co-benefits from anaerobic digestion of livestock manure were investigated. Cost-efficiencies arising from economies of scale for on-farm anaerobic biogas production were found for swine farms, and less so for dairy production systems. Without incentive schemes, on-farm biogas energy production was not economically feasible across the farm size ranges studied, except for 600- and 800-sow operations. Among single policy schemes investigated, green energy credit policy schemes generated the highest financial returns, compared to cost-share and low-interest loan schemes. Combinations of multiple policies that included cost-share and green energy credit incentive schemes generated the most improvement in financial feasibility of on-farm biogas energy production, for both swine and dairy operations.     

An economic and functional tool for assessing the financial feasibility of farm-based anaerobic digesters

Anaerobic digester (AD) technology is a form of renewable energy with significant upside potential and little public resistance. However, previous studies have generally found ADs to be a poor investment for private firms without public assistance. The mixed results on the financial feasibility of ADs could be due to the site of the analysis since results vary with size, geographic location or the type of AD system, which are not standardized but rather customized to the individual situation. Given the public and private interest in AD technology and the need to assess the feasibility by site, a decision-making tool that can be adapted for each location and system would aid assessing the investment. This paper presents a freely available workbook to determine the financial feasibility of a farm-based AD and to demonstrate its use. The decision-making tool identifies the technical and financial parameters affecting the returns to an AD and the sensitivity of the assumption to changes in the value of those parameters. An application of the workbook for the Ontario livestock sector demonstrates its usefulness. Investment in an AD is financially feasible only for the largest dairy farms in Ontario under current electricity prices, which are approximately six times greater than the wholesale price. Shifting to a duel fuel continuous system would improve returns, as would the availability of additional substrate material in the form of solid grease and vegetative waste. Reductions in capital cost and improvements in the efficiency of the technology are probable given the relatively infant status of the biogas sector but these future enhancements would likely only alter the investment decisions for large commercial dairy farms.     

Assessing the potential for the uptake of on-farm anaerobic digestion for energy production in England

We report on an assessment of the potential for energy production from on-farm anaerobic digestion (AD) in England based on findings from a survey of farmers where it was found that around 40% of 381 respondents might install AD on their farms. These ‘possible adopters’ tended to have large farms and might together utilise some 6560 ha of land for feedstock production along with the wastes from some 12,000 beef and dairy cattle and 9000 pigs. When raised to the national level, such a level of AD activity would produce around 3.5 GWh of electricity. This approximates to just 0.001% of national electricity generation. Further, there are considerable perceived barriers to the widespread adoption of AD on farms in England; these include the high capital costs of installing AD and doubts about the economic returns being high enough.     

Upgrading biogas produced at dairy farms into renewable natural gas by methanation

Renewable natural gas can be produced from raw biogas, a product of the anaerobic decomposition of organic material, by upgrading its CO₂ content (25‐50%) via thermocatalytic hydrogenation (CO₂ methanation). The H₂ needed for this reaction can be generated by water electrolysis powered by carbon emission‐free energy sources such as renewable or nuclear power, or using surplus electricity. Herein, after briefly outlining some aspects of biogas production at dairy farms and highlighting recent developments in the design of methanation systems, a case study on the renewable natural gas generation is presented. The performance of a system for renewable natural gas generation from a 2000‐head dairy farm livestock manure is evaluated and assessed for its economic potential. The project is predicted to generate revenue through the sale of energy and carbon credits with the payback period of 5 years, with a subsidized energy price.     

Analysis of small-scale biogas utilization systems on Ontario cattle farms

The production of biogas through the anaerobic digestion of cattle manure and its subsequent use in the generation of electricity on larger farms in Ontario is currently economically attractive. This is a result of the Ontario Feed-In Tariff (FIT) program, which provides incentivized rates for the production of electricity from biogas. Although larger farms can take advantage of the higher rates for electricity, there are substantially more smaller farms for which individually designed and engineered biogas systems would be prohibitively expensive. By employing the concept of modular biogas plants, this analysis evaluates the economics of small-scale biogas utilization systems. Dairy farms with at least 33 animals and beef farms with at least 78 animals can operate economically attractive biogas systems. This analysis shows that approximately 9000 additional Ontario cattle farms would be able to take advantage of the FIT program, which would add 120 MW_e of renewable energy capacity to the Ontario electrical grid.     

Overview analysis of bioenergy from livestock manure management in Taiwan

The emissions of greenhouse gases (GHGs) from the livestock manure are becoming significant energy and environmental issues in Taiwan. However, the waste management (i.e., anaerobic digestion) can produce the biogas associated with its composition mostly consisting of methane (CH₄), which is now considered as a renewable energy with emphasis on electricity generation and other energy uses. The objective of this paper was to present an overview analysis of biogas-to-bioenergy in Taiwan, which included five elements: current status of biogas sources and their energy utilizations, potential of biogas (methane) generation from livestock manure management, governmental regulations and policies for promoting biogas, benefits of GHGs (i.e., methane) emission reduction, and research and development status of utilizing livestock manure for biofuel production. In the study, using the livestock population data surveyed by the Council of Agriculture (Taiwan) and the emission factors recommended by the Intergovernmental Panel on Climate Change (IPCC), the potential of methane generation from livestock manure management in Taiwan during the period of 1995–2007 has been estimated to range from 36 to 56 Gg year⁻¹, indicating that the biogas (methane) from swine and dairy cattle is abundant. Based on the characteristics of swine manure, the maximum potential of methane generation could reach to around 400 Gg year⁻¹. With a practical basis of the total swine population (around 4300 thousand heads) from the farm scale of over 1000 heads, a preliminary analysis showed the following benefits: methane reduction of 21.5 Gg year⁻¹, electricity generation of 7.2 × 10⁷ kW-h year⁻¹, equivalent electricity charge saving of 7.2 × 10⁶ US$ year⁻¹, and equivalent carbon dioxide mitigation of 500 Gg year⁻¹.     

Life Cycle Energy Assessment of biohydrogen production via biogas steam reforming: Case study of biogas plant on a farm in Serbia

The aim of this paper is to demonstrate and to quantify energy flows in a life cycle of biogas to biohydrogen production, starting from feedstock materials via anaerobic digestion, biogas upgrading, biohydrogen production, to the end of biogas system (application of digestate as fertilizer in agriculture). The performance of the biogas plant of Mirotin dairy farm in Serbia has been assessed. According to Life Cycle Energy Assessment approach, results obtained in this study have shown that biohydrogen production via biogas steam reforming has negative energy balance (with ?16,837 GJ). It has also been demonstrated that this process is energy unsustainable in an environmental context. In future analysis it would be necessary to consider the other aspects of sustainability, e.g. the economical and social factors in order to estimate the overall sustainability of the biogas utilization pathways, especially having in mind that the technology of converting biogas to hydrogen is still in the development phase.     

Economics of anaerobic digestion in organic agriculture: Between system constraints and policy regulations

During its pioneer-stage in Germany, the generation of power and heat from anaerobic digestion (AD) was predominantly developed on organic farms. However, biogas production in organic agriculture (OR) never expanded to the same extent as in conventional farming (CV). Besides various other aspects, this appears to be mainly due to economic reasons related to system-specific production requirements. Therefore, this article analyses the framework conditions of organic biogas generation and assesses its monetary implications on production economics. The structural and economic comparison of organic and conventional generation of power from biogas displays systematic constraints for AD in OR and identifies advantages of conventional biogas plants, particularly concerning lower capital and biomass input costs. Moreover, frequently changing policy regulations, further aggravating the economic situation for biogas production in both farming systems, are reflected. Our study shows that the recent developments of political frameworks will inhibit biogas investments for nearly all types of biogas plants in Germany. Finally, an alternative evaluation approach for organic AD systems, considering monetary benefits from agronomic effects of an integrated biogas generation in organic agriculture is discussed.     

Prospective application of farm cattle manure for bioenergy production in Portugal

Biogas is a promising renewable fuel, which can be produced from a variety of organic raw materials and used for various energetic purposes, such as heat, combined heat and power or as a vehicle fuel. Biogas systems implementation are, therefore, subjected to several support measures but also to several constraints, related with policy measures on energy, waste treatment and agriculture. In this work, different policies and policy instruments, as well as other factors, which influence a potential expansion of Portuguese biogas systems are identified and evaluated. The result of this analysis shows that the use of the cattle manure for biogas production is still far from its potential. The main reason is the reduced dimension of the Portuguese farms, which makes biogas production unfeasible. Various options are suggested to increase or improve biogas production such as co-digestion, centralized plants and modular plants. Horizontal digesters are the most suitable for the typical Portuguese plant size and have the advantage of being also suitable for co-digestion due to the very good mixing conditions. Mesophilic anaerobic digestion due to a more robustness, stability and lower energy consumption should be the choice. The recent increase in the feed-in tariffs for the electricity production based on anaerobic digestion biogas is seen as a political push to this sector.     

Thermal analysis and optimization of an anaerobic treatment system of whey

The whey produced during cheese and cream cheese making process is one of the most important environmental problems dairy industries are facing, due to its high organic load. Anaerobic treatment seems to be a promising solution for this problem, since it not only reduces greatly the organic load but it also produces biogas, which can be then burnt. It is the scope of this study to perform an exergetic and economic analysis of an anaerobic treatment system of whey accompanied by the production of steam resulting from the burning of biogas. The system analyzed extends from the storage of whey, up to the disposal of the treated effluent from the anaerobic reactor, and the exit of the steam to be used in the plant. The exergy analysis is performed treating the system as a steam production plant, while the economic analysis, which is performed using the Net Present Value (NPV) method, is performed treating the system as a natural gas production plant. The exergy efficiency and NPV calculations are followed by a sensitivity analysis and an optimization with respect to some of the parameters used. Moreover, the exergy efficiency and NPV are calculated for three scenarios. The results indicate that the anaerobic treatment of high strength waste such as whey is a sustainable investment, at least for a substantial volume of whey.     

Economic and environmental assessment on the energetic valorization of organic material for a municipality in Quebec, Canada

Waste-to-energy provides a solution to two problems: waste management and energy generation. An integrated anaerobic waste valorization process is an interesting option, but because of investments cost and low energy value in the province of Quebec, it is hard for a municipality to commit to that solution. This paper investigated the economic possibilities to manage organic material, organic fraction of municipal solid waste, and municipal wastewater sludge by anaerobic digestion for a 150,000 inhabitant municipality, with consideration to energy generation and greenhouse gas emission reduction. Using the biogas to co-generation solution brings a payback time on investment (PBT) of 3.7 years with electricity price at 0.10 $Cdn/kW h. The addition of manure from surrounding farms increases the biogas production by 37%, but increases the PBT to 6.8 years unless the leftover digestate can be used for agronomic valorization; then it becomes economically advantageous. The natural gas purchasing cost is too low to promote the enrichment of biogas into renewable natural gas. However, this scenario has the lowest energetic payback time (3.3 years) and reduces the most greenhouse gas emissions (4261 tCO₂eq/a).     

A comprehensive review on pretreatment of microalgae for biogas production

Use of microalgal biomass for renewable energy production has gained considerable attention in the world due to increasing global energy demand and negative environmental impacts of nonrenewable fossil fuels. Anaerobic digestion is one of the renewable technologies that microalgal biomass is converted into biogas by anaerobic archea. One of the main drawbacks of using microalgal biomass for biogas production is that certain types of microalgae has rigid cell wall characteristics, which limits accessibility of anaerobic archea to microalgal intracellular organic matter during hydrolysis phase. This limitation lowers efficiency of biogas production from microalgal biomass. However, introducing pretreatment methods prior to anaerobic digestion provides disruption of rigid microalgal cell wall and improve biogas yields from microalgal biomass. The objective of this paper was to review current knowledge related to pretreatment methods applied prior to anaerobic digestion of microalgal biomass. Efficiency and applicability of pretreatment methods mainly depend on type of microalgae, cell wall characteristics, and cost and energy requirements during pretreatment process. In this review, various type of pretreatment methods applied to microalgal biomass was discussed in detail with background knowledge and literature studies in their potential on maximization of biogas yields and their cost effectiveness, which is important for large‐scale applications. In the view of current knowledge, it was concluded that each pretreatment method has a relative contribution to improvement in biogas production depending on the type of microalgae. However, energy and cost requirements are the main limitations for pretreatment. So, further studies should focus on reduction of cost and energy demand by introducing combined methods, novel chemicals, and on‐site or immobilized enzymes in pretreatment to increase feasibility of pretreatment prior to anaerobic digestion in industrial scale.     

Designing optimal supply chains for anaerobic bio-digestion/energy generation complexes with distributed small farm feedstock sourcing

Anaerobic bio-digestion/energy generation (ABD/EG) complexes that use animal waste have become increasingly important as renewable energy sources and logistics considerations are essential as animal biomass is of costly transportation due to its high weight per unit of energy generated. To ensure overall economic viability it is necessary to take into account the supply chain network when designing such a complex for at least two main reasons. First, these complexes provide power from energy sources which otherwise would go to waste and a well-designed supply chain network will significantly lower long-term operating costs. Second, because they provide an outlet for farm manure (their feedstock), these complexes allow farmers to expand production capacity whenever environmentally sound animal waste disposal is an active constraint to operations. This paper presents a methodology to design a supply chain which maximizes contribution and minimizes gas loss in the commonly found configuration in which feedstock providers are numerous small farms without on-site bio-digestion units, i.e., a configuration in which in-natura biomass is transported from those small farms to supply a nearby ABD/EG complex serving the region. The paper details three layers of analysis for designing optimal animal waste supply for anaerobic bio-digestion, including model formulation and mathematical solution for each stage. The broadest layer in the methodology is the identification of the optimal ABD/EG complex positioning given farm locations and consequent biomass transportation costs. The middle layer is the specification of the optimal logistics and transportation system, including the prioritization of supplying farms. The operational layer includes scheduling optimal biomass collection from each farm to minimize biogas loss.     

A perspective on the potential role of renewable gas in a smart energy island system

This paper examines the potential role for Power to Gas (P2G) as applied to an island energy system with high levels of renewable electricity penetration. P2G systems require both a supply of green electricity and a source of CO₂. Cheap electricity is essential for a financially sustainable P2G system. Using a PLEXOS model it was determined that deploying 50 MW_e of P2G capacity on the 2030 Irish electrical grid may reduce absolute levels of curtailed wind by 5% compared to the base case. CO₂ capture is expensive. The cheapest method of sourcing CO₂ for a P2G system is to employ a methanation process whereby biogas from anaerobic digestion is mixed with hydrogen from surplus electricity. Anaerobic digestion in Ireland has a potential to produce biomethane to a level of 10.2% of energy in transport (19.2 PJ/a). The potential CO₂ resource from anaerobic digestion could allow for a further 8.9% of energy in transport (16.6 PJ/a) from P2G production. An optimal model is proposed including for co-location of a biogas system with a P2G system. The model includes for demand-driven biogas concepts allowing electrical grid balancing and the supply of gaseous transportation fuel. Biofuel obligation certificates allows for a financially viable industry.     

Simulation of a solar‐biogas hybrid energy system for heating,fuel supply,and power generation

Biogas production from organic wastes has been widely utilized for several decades, but maintaining right temperature for anaerobic bacteria is a challenge. In order to overcome the inhibition of the bacteria growth and biogas production due to the low temperature, a solar‐biogas hybrid energy system for heating, fuel supply, and power generation has been proposed for converting domestic garbage into biogas in a rural area of China. In this system, the solar energy has been included as one of the heating sources during an anaerobic digestion process. A mathematical model has been developed to evaluate the influence of system operating characteristics. Based on the simulation results, the biogas production rate, thermal efficiency, temperature of the digester, energy distributions in the system, optimal operating parameters, economic efficiency, and thermodynamic characteristics of the system were analyzed. The impact of solar irradiation on the efficiency of the system was also studied. According to the results, in cloudy days, the reactor volume and solar collector area greatly influenced the steady energy supply. In winter, the produced biogas is mostly utilized by the aided boiler to maintain the proper organic mixture temperature in the bioreactor. Heat loss from bioreactor dramatically increases the organic mixture volume. Per simulation, the longest return on the investment of this type of the biogas system is about 5.54 years, and the shortest return on the investment is less than 4 years if the battery is removed and the electric grid can be used. Therefore, in this study, the feasibility of a hybrid energy system for converting domestic garbage into energy has been validated. Copyright © 2017 John Wiley & Sons, Ltd.     

Estimate of the electric energy generating potential for different sources of biogas in Brazil

The increasing interest in the recuperation of the biogas coming from organic residues, associated with its energetic use is a subject that has been widely discussed. Biogas was merely seen as a sub-product obtained from anaerobic decomposition (without oxygen) of organic residue. In the paper is carried out an evaluation of the quantities of organic residues coming out from the sugar and alcohol industry (vinasse), urban solid and liquid wastes (garbage and sewage) and livestock residues (bovine and swine manure) in Brazil. Finally the electricity generation potential of biogas out of the evaluated sources of organic residues in Brazil is estimated. The results of this study indicate that the potential regarding the production of biogas out of the aforementioned organic residues of electricity production using could meet an energy demand of about 1.05 to 1.13 %. Constraints for biogas energy utilization are identified and discussed.     

生物质能利用技术的经济性分析

对国内生物质能利用技术的现状进行了简要介绍和分类，以经济评价为基础，对生物质直接燃烧、户用沼气池、生物质气化发电、大中型养殖场沼气工程和垃圾发电等生物质能技术进行了综合分析，提出了根据地方实际，发展不同生物质能技术的建议。     

Techno‐economic assessment for energy generation using bagasse: case study

Bagasse is selected as the biomass source that is studied because of its annual significant rate production in Iran and potential for energy generation. Bagasse has been as an energy source for the production of energy required to run the sugar factory. The energy needed by factories was supplied by burning bagasse directly inside furnaces, which had an exceptionally low output. To this end, today, a secondary use for this waste product is in combined heat and power plants where its use as a fuel source provides both heat and power. In addition, low efficiency of traditional methods was caused to increase the use of modern methods such as anaerobic digestion, gasification and pyrolysis for the production of bio‐fuels. In this paper, the energy conversion technologies are compared and ranked for the first time in Iran. Therefore, the most fundamental innovation of this research is the choice of the best energy conversion technology for the fuel production with a higher efficiency. To assess the feasibility application and economic benefit of biogas CHP plant, a design for a typical biogas unit is programmed. The results show the acceptable payback period; therefore, economically and technically, biogas CHP plant appears to be an attractive proposition in Iran. Copyright © 2012 John Wiley & Sons, Ltd.     

Methane yield of oat husks

The biogas yield of solid manure from dairy cattle depends on its quality and the proportion of excreta and organic litter material contained within. The biogas yield of both faeces and straw is available in literature. Straw is a common litter material of mixed farms. However, straw is scarcely available on dairy farms. Oat husks are appropriate to replace or supplement straw for use as litter material. In this study, the actual methane yield and the total methane potential of oat husks were determined. Based on an optimized test with ground oat husks, the total methane potential resulted from regression and extrapolation of the experimental data. The total methane potential was determined with 242 L_N CH₄ kg⁻¹ VS added. Additionally, the actual methane yield over retention time at a digestion temperature of 37 °C was determined, using untreated oat husks. For 42 days of retention, the methane yield was 202 L_N CH₄ kg⁻¹ VS added at 52% CH₄ content. Results indicate that the methane yield of oat husks reaches the same level as that of straw. The total methane potential is not higher, but digestion of oat husks may proceed faster. Verification of the laboratory results on-farm revealed that the contribution of oat husks to overall methane production of a prototype biogas plant for solid manure might reach up to 80%.     

Effect of thermal, chemical and thermo-chemical pre-treatments to enhance methane production

The rise in oil price triggered the exploration and enhancement of various renewable energy sources. Producing biogas from organic waste is not only providing a clean sustainable indigenous fuel to the number of on-farm digesters in Europe, but also reducing the ecological and environmental deterioration. The lignocellulosic substrates are not completely biodegraded in anaerobic digesters operating at commercial scale due to their complex physical and chemical structure, which result in meager energy recovery in terms of methane yield. The focus of this study is to investigate the effect of pre-treatments: thermal, thermo-chemical and chemical pre-treatments on the biogas and methane potential of dewatered pig manure. A laboratory scale batch digester is used for these pre-treatments at different temperature range (25 °C-150 °C). Results showed that thermo-chemical pretreatment has high effect on biogas and methane potential in the temperature range (25–100 °C). Maximum enhancement is observed at 70 °C with increase of 78% biogas and 60% methane production. Thermal pretreatment also showed enhancement in the temperature range (50–10 °C), with maximum enhancement at 100 °C having 28% biogas and 25% methane increase.