Current Status and Trends of the Biogas Industry in the United States

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Current Status and Trends of the Biogas Industry in the United States 1 Overview: The development of biogas technologies in the United States is generally slower compared to that in Europe and China. In the 1970s, rising oil prices led to the construction of some biogas facilities. Between 1970 and 1990, approximately 140 biogas plants were built, primarily for energy purposes. However, due to issues such as inadequate facilities, non-standard design, improper installation, and poor management, most of these early biogas digesters have been scrapped or taken out of use. Over the past five years, with global warming and shortages of fossil fuels, biogas technology has received increasing attention, and related research as well as demonstration project development have gradually resumed. According to the U.S. Environmental Protection Agency (EPA), there were approximately 111 biogas plants in operation in 2007; these were mainly biogas power generation facilities located on livestock and poultry farms, producing a total of 215 million kWh of energy per year. The energy produced by biogas projects in 2007 was 3 times that of 2003. 2 Main drivers of the development of biogas technology 2.1 Environmental and energy benefits are the key drivers behind the development of biogas technology in the United States. According to a survey conducted by the U.S. Environmental Protection Agency (EPA) on man-made methane emissions in the country, greenhouse gas emissions such as carbon dioxide from the energy and industrial sectors showed a downward trend from 1990 to 2005, while emissions of greenhouse gases like methane resulting from manure management in livestock farms increased by 34%. This is because farming and planting in U.S. farms are generally developed in coordination; previously, livestock manure was mostly stored in open ponds before being used as fertilizer in the fields, and this storage process generated large amounts of greenhouse gases such as methane and carbon dioxide. Biogas projects can bring about various environmental benefits, such as minimizing greenhouse gas emissions, controlling the release of odors, and preventing water pollution caused by the leakage of feces ； It simultaneously produces usable biogas (50-70% methane) as an energy source, as well as nutrient-rich fertilizer for scientific research, thereby improving sanitary conditions. Due to the benefits of these biogas projects and the increasingly stringent environmental regulations, **, farmers, and renewable energy companies are more motivated to build biogas projects. 2.2 Incentive Policies In recent years, to promote the development of biogas projects using livestock and poultry manure and to achieve energy savings and emission reductions, the U.S. Department of Agriculture (USDA), the U.S. Environmental Protection Agency (EPA), and the U.S. Department of Energy (DOE) have jointly launched the AgSTAR program. This program establishes a service and management platform for the development of biogas projects, providing information on policies, laws, technologies, equipment, and market aspects related to such projects. The U.S. federal ** and state governments have also established programs and provided financial support to encourage the development of biogas projects. Therefore, most biogas projects receive support from the U.S. federal government. For example, Section 9006 on renewable energy and energy efficiency in the Fiscal Year 2002 Agriculture Act, which provides for different incentive policies at the federal and state levels, mandates support for biogas projects; since 2003, the U.S. Department of Agriculture has allocated a total of $31 million to anaerobic digestion systems. The Minnesota Department of Agriculture’s \"Methane-Producing Digesters Loan Program\" provides interest-free loans to farmers who build biogas power generation facilities. 3 Three typical anaerobic digestion processes in the United States
3.1 Membrane-covered anaerobic ponds involve covering existing livestock manure storage ponds with a membrane to collect biogas. The organic load is low, generally ranging from 0.05 to 0.2 Kg COD/m³·day. The hydraulic retention time ranges from 60 to 360 days, depending on the management of the facility. Fermentation at medium temperature of 35–40.5°C, with an organic load of 1–10 KgCOD/M3·d. Hydraulic retention time is 5–20 days; the TS concentration in the treated fecal sludge is 3–10%. Currently, Germany’s new technology for integrated gas production and storage in anaerobic tanks is being used on farms in agricultural states such as Wisconsin in the United States. Due to its low cost and reliable performance, it has gradually become the standard type of tank. 3.3 Plug-flow anaerobic digester: a narrow and long underground reinforced concrete structure that facilitates temperature increase; generally, a single membrane is used on the top to collect biogas. Fermentation is carried out at a moderate temperature of 35–40.5°C, with an organic load of 1–6 KgCOD/M3.d. Hydraulic retention time is 18-20 days, with a TS concentration of 5-13% in the treated wastewater. It is commonly used for manure from cattle farms, but is not suitable for manure containing sand. 800-cow farm feces plug-flow anaerobic digester. Due to its low construction cost and ease of management, this process has become the mainstream anaerobic technique in the United States; plug-flow, completely mixed, and membrane-covered anaerobic digesters account for 58%, 27%, and 19% of all biogas projects respectively. There are also individual farms that use ASBR and UASB processes to treat pig manure wastewater. 4. Main obstacles to the development of biogas projects in the United States Currently, the development of biogas projects in the U.S. faces several economic, technological, policy, and social obstacles. 4.1 Economically: The cost of generating electricity from fossil fuels is very low (on average $0.09/kWh), while the return on investment for biogas power generation ($0.05–$0.11/kWh) is low; the required investment is substantial, and there are insufficient fiscal incentives. There are also issues related to the contract period with power companies. 4.2 Technically: The issue of maintaining sanitary standards in the reuse of sludge as bedding in cattle sheds and for composting; there are significant technical risks (such as farmers lacking the capability to operate and maintain complex biogas systems, reductions in phosphorus levels in the fermented liquid applied to the fields, and difficulties in increasing gas production). 4.3 In terms of institutions: Due to the scattered and independent nature of U.S. ranches, it is difficult to develop centralized biogas projects with high efficiency; the implementation of carbon and green credit trading systems remains inadequate. 5. Advances in new biogas technologies 5.1 New models for the development and utilization of biogas. The membrane-covered anaerobic lagoon used to treat wastewater from 8,600 pigs has a short retention time. The TS concentration of the manure treated is 0.5-3.0%. It is commonly used in the treatment of pig manure wastewater. Scientific Research: New approaches to the utilization of biogas from organic waste in the United States. undefinedemsp;5.2 Renewable natural gas technology: The price of natural gas in the U.S. is still 3-5 times higher than the cost of producing biogas. Therefore, purifying and upgrading biogas with a methane content of 50%-70% into natural gas with a methane content of 94-98% has become a commercially viable prospect. Currently, the largest renewable natural gas project in North America is the Huckabay Ridge project in Texas. There, biogas is purified and compressed into high-purity methane, which is then injected into natural gas pipelines. The project became operational in October 2008. The facility processes manure from 10,000 cows. With a total investment of $12 million, it is expected to generate 200,000 tons of offsettable carbon credits per year. 5.3 High-concentration anaerobic dry fermentation technology: A pilot-scale plant for the anaerobic dry fermentation of 8 tons per day of organic waste such as food waste, developed by Professor Zhang Ruihong from the University of California, Davis, was put into operation in October 2007. The high-temperature anaerobic staged fermentation system for high-concentration various organic materials has the advantages of high gas production and less residue after fermentation. Currently, anaerobic engineering on a productive scale is under development. 5.4 Biogas fuel cell power generation technology: In 2005, Professor Philip Goodrich from the University of Minnesota successfully developed a 5KW hydrogen fuel cell generator using biogas generated by dairy farms at Haubenschild. This generator has the advantages of low noise and no pollution, but it has the disadvantages of high power generation costs and a large size. 6 Some suggestions: In summary, taking into account the actual situation of the development of biogas projects in China, to promote the sound and rapid growth of China’s biogas industry, the author believes there are several areas where efforts can be made. First, improve incentives for renewable energy; in light of the environmental benefits and energy-saving effects of biogas projects, increase financial subsidies and interest-subsidized loans to provide greater support. At the same time, research should be conducted to establish policies for market trading of carbon credit emissions reductions in domestic biogas projects. Second, it is necessary to strengthen the research and development of new technologies and equipment for biogas projects, in order to achieve industrialization, scaling up, and standardization, as well as the modular assembly of main fermentation tanks, thereby improving quality and reducing project costs. Third, research should be conducted on multi-feedstock high-concentration combined fermentation techniques to ensure an adequate supply of raw materials for gas production and to increase the gas output of the facilities. It promotes the development of biogas projects in a more centralized and larger-scale direction, thereby improving the economic viability of these projects and their energy efficiency. Fourth is to improve the capacity for the commercialization of biogas. Remove barriers to grid connection for biogas power generation and implement electricity price subsidies. Research and development are being carried out on the technologies for purifying and compressing biogas to produce high-purity methane, which can then be injected into natural gas pipelines or used as fuel for vehicles, thereby advancing the use of biogas to higher levels and improving energy efficiency. Fifth, it is necessary to improve and plan the layout of breeding and planting industries in a rational manner, achieve a balance between breeding and planting, ensure the comprehensive utilization of biogas slurry and residue, reduce transportation costs, and improve efficiency.