Search

Wastewater treatment plants (WWTPs) are large electricity and natural gas consumers with untapped potential to recover carbon-neutral biogas and provide energy services for the grid. Techno-economic analysis of emerging energy recovery and management technologies is critical to understanding their commercial viability, but quantifying their energy cost savings potential is stymied by a lack of well curated, nationally representative electricity and natural gas tariff data. We present a dataset of electricity tariffs for the 100 largest WWTPs in the Clean Watershed Needs Survey (CWNS) and natural gas tariffs for the 54 of 100 WWTPs with on-site cogeneration. We manually collected tariffs from each utility's website and implemented data checks to ensure their validity. The dataset includes facility metadata, electricity tariffs, and natural gas tariffs (where cogeneration is present). Tariffs are current as of November 2021. We provide code for technical validation along with a sample simulation. [ABSTRACT FROM AUTHOR]

Harvesting a winter rye energy cover crop (Secale cereale L.) could help sustain growing food and energy demand, provide new revenue streams, and enhance ecosystem services without inducing land-use change. A two-year field experiment with three planting methods and three N fertilization rates (0, 60, and 120 kg N ha−1) that produced >5.0 Mg ha−1 yr−1 of biomass was evaluated for (1) fresh and anaerobically digested rye forage quality; (2) revenue potential from renewable bioenergy, carbon markets, and digestate feed protein; and (3) potential greenhouse gas (GHG) offsets. We showed that rye can be harvested as forage for animals or anaerobically digested to produce renewable natural gas (RNG), with the residue after digestion (digestate) still available as a feed protein concentrate. Anaerobically digesting rye improved forage quality indicators. Digestion significantly decreased acid- and neutral-detergent fiber (ADF and NDF) by 5.2% and 17.8%, respectively, while significantly increasing crude protein (CP) (33.6%), total digestible nutrients (TDN) (2.0%), relative feed value (RFV) (23.6%), net energy for lactation (8.3%), maintenance (7.5%), and gain (20.0%). Using market prices for RNG, high protein feed, and GHG mitigation, potential on-farm revenue ranged from USD 307 Mg−1 and USD 502 Mg−1 dry matter with an average of USD 402 Mg−1. However, there are substantial costs associated with RNG and the revenue potential does not represent the profitability of this system. Evaluation of the integrated system showed GHG emissions associated with rye fertilization were more than offset by the benefits of increasing yield in the 60 kg N ha−1 treatment. The overall carbon footprint of the integrated system was strongly carbon negative, confirming the potential of this strategy to sustainably intensify land use in the Midwestern United States. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid renewable power plant with a storage system is designed. The benefits of sizing and energy management are assessed for a commercial building under eight different climatic conditions in the United States. In the considered system, photovoltaic panels are coupled to a unitized regenerative solid oxide fuel cell. The use of biogas to feed unitized regenerative solid oxide fuel cell is investigated, employing a detailed electrochemical model of electrolyzer and fuel cell modes. A battery pack is included in the plant as a secondary storage system, together with a diesel engine operating in backup mode. Four scenarios where biogas amount is varied together with the initial state of charge of the battery were evaluated. Results demonstrate that the power plant can operate with 100 % renewable procurement if the digester produces from 6000 to 9500 stdm3/y and the battery is completely charged at the beginning of the year. By reducing the biogas availability or starting with a low state of charge, the use of the diesel generator is inevitable. The study confirms that the proposed hybrid renewable power plant is technically feasible and can be considered a reliable and clean energy source in other areas and buildings. • Fully renewable power plant optimization/sizing for commercial buildings. • Influence of U.S. climate zones on power plant operations. • Definition of a control strategy for fossil fuel usage minimization. [ABSTRACT FROM AUTHOR]

This study provides a holistic Life Cycle Assessment (LCA) for evaluating the decarbonization potential of using Anaerobic Digestion (AD) in food waste treatment. The LCA is based on the development of a new flexible tool that allows the integration of the LCA at the process level with geospatial data and therefore includes a wide range of factors such as multiple feedstocks, technologies for end-use applications, and facility locations. This tool estimates a potential for reducing 21.8 MMtons CO 2eq /y (345 g CO2eq /kg waste) and generating 161 TBTU/y of renewable natural gas for the whole United States by managing food waste based on waste-hierarchy. This study also identifies those states with a more efficient AD implementation potential regarding CO 2eq avoidance. It highlights the importance of including region-specific conditions since feedstock diversion depends on the state and is the main contributor to the decarbonization potential, up to 60 % of the avoided emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

Hemp (Cannabis sativa L.) is a multi‐use crop that has been investigated for its potential use in phytoremediation of heavy metals, radionuclides, and organic contaminants, and as a feedstock for bioenergy production. A review of research literature indicates that hemp is a suitable crop for phytoremediation, and a competitive option for bioenergy. Coupling phytoremediation and bioenergy production from a single hemp crop is a potential solution to overcoming the economic constraints of phytoremediation projects. The current challenge is ensuring that the extracted contaminants are not introduced into the consumer marketplace. After several decades of limited research on hemp in the United States, the purpose of this review is to identify the knowledge available for hemp applications in phytoremediation or in production of bioenergy, and if and how those two purposes have been combined. The literature shows that hemp growth has been demonstrated successfully at the field scale for phytoremediation and in several bioenergy conversion technologies. Little is known about the fate of contaminants during hemp growth or during post‐harvest processing, especially the relationships between hemp genetics, metabolomics, and contaminant partitioning. Complicating the understanding is the expectation that contaminant fate will be dependent on the contaminant type, the concentration in the material, and the processing methods. Before hemp from phytoremediation applications can be used for bioenergy, the fractionation of heavy metals, radionuclides, and/or organic compounds during transesterification, anaerobic digestion, fermentation, and/or combustion of hemp must be evaluated. [ABSTRACT FROM AUTHOR]

Using food waste (FW) as a co-substrate in anaerobic digestion (AD) results in increased energy production, decreases in greenhouse gas emissions, and recycles the FW nutrients back to the land for producing crops. This research investigated food waste AD systems in the United States (US) and Germany (DE) that co-digested FW with dairy manure at the lab and full-scale. In DE, the post-consumer FW had 32–49% more CH 4 potential (477–499 mL CH4 /g VS) than maize and grass silage (368 and 331 mL CH4 /g VS) and solid and liquid manure (243 and 91 mL CH4 /g VS). Methane production in the full-scale DE system with 66% FW (by volume) was 882 m3 CH4 /d, which was 37% higher than the laboratory results due to the 86-day retention and 42 °C AD conditions in the field. The pre-consumer FW in the US had a similar CH 4 potential (264–553 mL CH4 /g VS), but due to the lack of heating in the full-scale system, 62% less CH 4 was produced than the lab-based potential. While DE requires pasteurization of FW for AD and bans FW bans to landfills, the US does not have specific requirements for FW treatment in AD or federal FW landfill policies, with a few forthcoming FW bans in some municipalities and states. As FW diversion and utilization in AD systems is expected to grow, it is important to understand the effect of FW in biogas production and nutrient content, comparisons between lab and field-scale results, and the effect of policy on FW utilization. [ABSTRACT FROM AUTHOR]

• Siloxanes increase the maintenance costs exponentially with increasing gas flow rates at biogas-to-energy facilities. • Economics of siloxane removal by carbon adsorption vs increased maintenance were compared. • Carbon adsorption for siloxane removal is economical at facilities with biogas flows over 1700 m3/h. • Facilities with flows less than 1300 m3/h, carbon adsorption may not be economical. • Siloxane removal would increase the engine performance and reduce maintenance needs at all facilities. Siloxanes present in small concentrations in biogas interfere with the operation of biogas-to-energy facilities. During biogas combustion, siloxanes form white deposits on engine components (engine heads, spark plugs, valves) in crystals or amorphous forms depending on the temperature. The purpose of this study was to evaluate the economic feasibility of biogas-to-energy systems for managing the operational challenges due to siloxanes in biogas. The facility maintenance cost data were compiled by a survey of biogas-to-energy facilities in the United States. Economic analyses were performed to compare the operational costs due to increased maintenance for removing the white deposits forming on the engine components and the installation of a pretreatment system (carbon adsorption) to remove siloxanes prior to combustion. Numerical analyses showed that for the facilities with operating capacities less than 1300 m3/h (750 scfm), the costs for installation and operation of the carbon adsorption system exceeded the maintenance costs for removal of deposits from the engine components. The maintenance costs correlated well with the reported maintenance needs which were between 120 and 800 man hours per year. On the basis of siloxane removal costs alone, it is not economically feasible to install a carbon adsorption system for siloxane removal prior to combustion for small facilities processing less than 1300 m3/h (750 scfm) of biogas. However, using a process for siloxane removal prior to gas engines (e.g., carbon adsorption) would be improve the overall performance of the gas engines and reduce maintenance need at all facilities. [ABSTRACT FROM AUTHOR]

Abstract Danish farmers are increasingly adopting sand bedding within their dairy farms, which is creating challenges for biogas plants, as sand-laden manure hampers biogas production. This creates a potential problem where large amounts of animal manure will not be utilized for biogas production, and, correspondingly, will not contribute to the production of either renewable energy or valuable digestate (fertilizer). Moreover, the pressure on an imported (external) and highly exploited resource - here, sand - is increasingly calling for more sustainable and self-sustained farm systems, as far as cow bedding materials are concerned. The methodological approach in this paper is first to investigate state-of-the-art sand-separation technologies in Denmark and the USA, particularly in relation to their environmental and energy performance, then, second, to analyze how other types of bedding materials can be utilized by drawing on on-site (internal) farm resources, namely residual straw and the fiber fraction of manure. The results of the analysis suggest that, in particular, manure fibers are beneficial for animal welfare and biogas production, resulting in a more circular economic system. The paper concludes by presenting a new farm-biogas system that sustains such circularity. To support this development, we further suggest investigating in new ventilation technology to limit the amount of ammonia that is produced in dairy stables as a result of using manure fibers as bedding material. Highlights • Sand bedding in dairy cow stables is a challenge for efficient biogas production. • Sand laden manure is currently treated using immature and inefficient technologies. • Combine animal welfare and bedding material that favor biogas production important. • Manure fiber bedding is a 'circular' and internal farm resource as opposed to sand. • Hygenized manure fibers can provide animal welfare, high milk and biogas yields. [ABSTRACT FROM AUTHOR]

The aim of the research was to determine the exchange rate of carbon dioxide between the atmosphere and the maize field fertilized with the digestate from an agricultural biogas plant. The studies considered both the amount of net carbon dioxide emission which is the difference between the amount of this gas absorbed by vegetation and its amount emitted from the whole ecosystem of the field as well as the emission resulting only from the changes occurring in the soil. The CO2 emission from the entire field was measured by the eddy covariance method with a set of LI-7500A analyzer (LI-COR Biosciences, USA) for measuring the CO2/H2O concentration in air and 3-axis WindMaster ultrasonic anemometer (GILL, UK). The data from the analyzers were recorded at 10 Hz, while the CO2 streams were calculated using the EddyPro 5 software. The soil emission was determined with the chamber method using the automated ACE measurement system (ADC BioScientific, UK). Until the maize reached maturity, the study was carried out once a week, at 10.00 - 14.00. During each measurement day, the basic meteorological parameters were measured as well. The obtained results showed a clear relationship between the plants development phase and the size of the net CO2 exchange. The negative values of carbon dioxide streams, indicating the absorption of this gas from the atmosphere, were observed already in the case of plants with a height of approx. 25 cm, while the maximum values were reached after the release of panicles by maize. The carbon dioxide emission from soils, measured at the same time, was maintained throughout the entire research period at a similar low level, undergoing only slight fluctuations associated with variable soil moisture. The study showed that the maize field, almost throughout all growing season, can be treated as a sink of atmospheric carbon dioxide, reducing its emission from agriculture. [ABSTRACT FROM AUTHOR]

Anaerobic Digestion (AD) is a promising technology to treat slaughterhouse waste (SHW) for the bioenergy production, nutrient recovery, and pathogen reduction. Three scenarios of estimating the biomethane potential from SHW of the US and the individual States have been conducted in this study. The US meat producers discharged 18.4 million metric ton (MT) SHW in 2016, which can potentially generate 22.7 × 10 9  kWh of biomethane. In Texas State, up to 2.3 × 10 9  kWh year −1 of energy can be potentially produced from AD of SHW and up to 106.3% of natural gas currently used in the Nebraska State for electricity generation can potentially be replaced with biomethane produced from the AD of its SHW. The technical challenges using SHW as the feedstock of AD process in the US have been summarized, including nitrogen and sulfur inhibition, foaming, sterilization, digestate disposal, supply chain etc. In addition, case studies were conducted by proposing an AD plant treating SHW from a typical slaughterhouse in a U.S. State that mostly processes the broiler, swine, and bovine. In our case studies, a net energy of 17,009–85,278 kWh d −1 is estimated to be generated from such AD plant. Therefore, producing biomethane from SHW can significantly promote bioenergy production in the US, thus enhancing the quick reach of bioenergy development targets set at the Federal and State levels, while overcoming the technical and management barriers of using SHW. [ABSTRACT FROM AUTHOR]

Farm operations in the USA and Europe have seen a radical change in the last decades: small sized farms are disappearing, and farm size and total livestock on larger farms are increasing. The resulting spatial density of animals causes several environmental impacts. Anaerobic digestion is one promising technical solution to alleviate most of these impacts while simultaneously providing a regional energy source. This analysis assesses the economic viability of using dairy-cow manure for either (i) the on-farm production and use of biogas to generate electricity and heat or (ii) the upgrading biogas to biomethane, a natural-gas substitute. A non-linear optimization model was developed to optimize plant capacity for anaerobic digestion and maximize the net present value for each option by farm size. In this study, we used Idaho‘s dairy farms as a case study. The analysis implies that at least 3000 cows per farm are required for an economically viable anaerobic-digestion plant operation. For farms with up to 3600 animals, the highest net present value was achieved for the on-farm use of biogas. Farms larger than that achieved their best economic results via the production of biomethane. In total about 45% of Idaho’s dairy manure could be utilized by economically feasible biogas and biomethane plants. A higher manure utilization rate could be achieved through joint, cooperative anaerobic digestion plants and manure transportation. The results can be transferred to other regions and countries, respectively, to reduce the negative impact of intensive livestock farming. [ABSTRACT FROM AUTHOR]

Landfill gas (LFG) management is one of the most important tasks for landfill operation and closure because of its impact in potential global warming. The aim of this work is to present a case history evaluating an LFG capture and treatment system for the present landfill facility in Córdoba, Argentina. The results may be relevant for many developing countries around the world where landfill gas is not being properly managed. The LFG generation is evaluated by modeling gas production applying the zero-order model, Landfill Gas Emissions Model (LandGEM; U.S. Environmental Protection Agency [EPA]), Scholl Canyon model, and triangular model. Variability in waste properties, weather, and landfill management conditions are analyzed in order to evaluate the feasibility of implementing different treatment systems. The results show the advantages of capturing and treating LFG in order to reduce the emissions of gases responsible for global warming and to determine the revenue rate needed for the project’s financial requirements. This particular project reduces by half the emission of equivalent tons of carbon dioxide (CO2) compared with the situation where there is no gas treatment. In addition, the study highlights the need for a change in the electricity prices if it is to be economically feasible to implement the project in the current Argentinean electrical market. Implications: Methane has 21 times more greenhouse gas potential than carbon dioxide. Because of that, it is of great importance to adequately manage biogas emissions from landfills. In addition, it is environmentally convenient to use this product as an alternative energy source, since it prevents methane emissions while preventing fossil fuel consumption, minimizing carbon dioxide emissions. Performed analysis indicated that biogas capturing and energy generation implies 3 times less equivalent carbon dioxide emissions; however, a change in the Argentinean electrical market fees are required to guarantee the financial feasibility of the project. [ABSTRACT FROM AUTHOR]

Recently the United States Environmental Protection Agency qualified biogas from landfills and anaerobic digesters as a cellulosic transportation biofuel under the expanded Renewable Fuel Standard (RFS2). Biogas is a renewable fuel that can generate Renewable Identification Number credits for the producer. The wastewater industry may not be able to keep pace with this opportunity. Less than 10% of WWTPs in the US have currently produced biogas for beneficial use. Supporting growth of the biogas industry requires implementation of new practices and policies. In this review, the barriers, gaps, and challenges in deploying biogas production technology are identified. Issues are classified as economic, technical, social or regulatory issues. Some of the critical challenges to the economics of digester operations are the slow rate of biogas generation, the low energy content of the biogas, and the costs to upgrade the biogas. Currently there is little biogas utilization at US WWTPs. Most biogas is flared while some is used for onsite process heat and power production. Case studies of co-digestion of biosolids with organic wastes at field-scale show the use of co-digestion could overcome significant economic challenges including higher methane yield, more efficient digester volume utilization and reduced biosolids production. These findings could provide guidance in retrofitting existing facilities or in designing new biogas production and utilization systems. The RFS2 ruling increases market certainty, hence reduces risk. The evaluation of applications of co-digestion at WWTP scales ranging from 1 million gallons per day (MGD) to 375 MGD determined its potential feasibility for different types of digester operation, organic waste and loading rate as well as effectiveness of providing energy self-sufficiency at the WWTPs. This work could improve economics of anaerobic digestion at WWTPs, enabling viable and sustainable biogas industry and offsetting costs for wastewater management. [ABSTRACT FROM AUTHOR]

The article presents information on the growth in the biogas markets of the U.S. It explores anaerobic digestion (AD) electricity potential in the country. A map of the U.S. is included in the article that shows the locations where companies are developing biogas electricity projects in the country.

Abstract: Anaerobic digestion (AD) is an economically viable manure treatment option for large dairies (>500 cows) in the U.S. However, roughly 90% of U.S. dairies have less than 200 cows, making this technology economically inaccessible to the vast majority of U.S. dairies. While there have been case studies of individual small dairies with anaerobic digesters, there are no comparative studies using cost data from these systems. The objectives of this study were to (1) determine the economic viability of small-scale U.S. digesters using cost data from nine existing 100 to 250-cow dairies and seven theoretical systems and (2) reevaluate the minimum size dairy farm needed for economically feasible AD in the U.S. Cash flow analysis results showed that total capital costs, capital costs per cow, and net costs per cow generally decreased with increasing herd size in existing systems. Among existing revenue streams, use of digested solids for bedding generated the highest revenue ($100cow−1 year−1), followed by biogas use for heating and/or electrical generation ($47 to $70cow−1 year−1) and CO2 credits ($7cow−1 year−1). No system had a positive cash flow under the assumed conditions (8% discount rate, 20-year term). However, six of the 16 systems had positive cash flows when 50% cost sharing was included in the analysis. Our results suggest that, with cost sharing, economically viable AD systems are possible on 250-cow dairies. Additional revenue streams, such as tipping fees for food waste, may reduce the minimum size to 100-cow dairies. [Copyright &y& Elsevier]

Abstract: The fuel economy and mass emission of an automotive spark ignition vehicle fuelled with the methane enriched biogas (93% CH4) and base CNG (89.14%) were evaluated using chassis dynamometer under modified Indian driving cycle (MIDC). The transient emissions were also measured with respect to time. The emissions such as CO, HC and NO x are marginally higher with the enriched biogas than base CNG. But, the experimental results indicate that the vehicle’s emission with the enriched biogas fuel meets to the BS IV Emission Norms. There is no significant change in fuel economy of the vehicle fuelled with the enriched biogas (24.11km/kg) as compared to base CNG (24.38km/kg). The experimental data indicates transient emission characteristics (CO, HC and NO x ) of the vehicle with respect to time for both fuels are very higher with urban cycle (low speed) than extra urban cycle (high speed) and the findings could be useful to find out scopes of further improvement in transient emission and performance of the engine. As the methane enriched biogas gives similar performance like fossil CNG, the enriched biogas could be used as an auto fuel for spark ignition vehicles. [Copyright &y& Elsevier]

Abstract: The technical and economic feasibility of anaerobic digestion to produce biogas at a small wool-scouring facility in the United States was examined. The facility will process 90,800kg (200,000 pounds) of greasy wool per year at maximum capacity. Biochemical methane potential experiments showed that anaerobic biodegradation of organic constituents in wool-scouring effluent (WSE) ranged from 17 to 75% on a chemical oxygen demand (COD) basis and produced 0.10–0.39L methane per gram of WSE COD added. Microbial inhibition was observed when initial WSE concentrations exceeded 1000mg COD/L. A laboratory-scale continuous reactor operated at organic loading rates of 100–200mg COD/L/day produced biogas with an average methane content of 75% and provided 72–78% removal of total WSECOD. Life cycle costing predicted that the best alternative for energy recovery at a small wool-scouring facility was to offset natural gas used to heat water for wool-scouring with biogas. Economic feasibility should increase with increasing COD removal, increasing natural gas price, and increasing cost to discharge to the municipal wastewater treatment works. The key anaerobic treatment design challenge will be to maximize WSE organic loading rates while minimizing microbial inhibition. [Copyright &y& Elsevier]

Food waste is the most difficult waste fraction of household waste to manage because it is wet and putrescible. It becomes odorous and it attracts flies and scavengers. When it sticks to other wastes, it reduces the yield of dry recyclables. Home composting has the benefit of proximity but many are unwilling or unable to practise it. Source segregation and storage for kerbside collection and treatment works for many households but not for all, participation is especially low among households in flatted properties. The in-sink food waste disposer (FWD) is used extensively in Australia, New Zealand and the USA but it has been relatively underutilised in Europe. Using data from the published literature, the global warming potentials for landfill, incineration and centralised composting were calculated to be respectively +743, +13 and −14 kgCOe/t food waste; anaerobic digestion was approximately −170 kgCOe/t food waste irrespective of whether the food waste is delivered by truck or by FWD and the public sewer. Surahammar in Sweden has provided a unique opportunity to assess the impacts of FWD at community scale and compare them with results from laboratory studies and field trials. Over 14 years, FWD installation went from zero to 50% of households voluntarily; 4-weekly influent monitoring data from the wastewater treatment works of the town show that biogas increased by 46% but flow (water use) and chemical and biological load did not change significantly. [ABSTRACT FROM AUTHOR]

Lignocellulosic feedstocks have high energy content and have been co-digested with sewage or manure biosolids in Europe for many years. However, it is unclear whether the current U.S. anaerobic digesters are capable of co-digesting lignocellulosic feedstocks without experiencing operational problems. We evaluated co-digestion of switchgrass with sewage biosolids under laboratory conditions similar to common U.S. digesters. Results indicated that finely-ground or ensiled switchgrass could be readily co-digested with sewage biosolids under typical U.S. digester conditions. Concentration up to 4% solids (representing up to 47% of VS added) achieved good specific methane yields and up to 74% energy conversion efficiency while maintaining acceptable VS removal. No evidence of solids accumulation, mixing problems, or floating debris was noted. However, fine-grinding switchgrass is energy intensive and likely to be cost-prohibitive. Moreover, ensiling produced a wide array of particle sizes and the effects of ensiling could not be fully separated from effects due to smaller particle size. Coarsely ground switchgrass, however, did not digest well. It had a low specific methane yield and quickly led to digester operational problems, even at the 2% solids level. Further research is needed to identify pretreatment methods that are more practical than fine-grinding. Ensiling appears promising, and should be studied under full-scale ensiling and digestion conditions to assure that observed effects were not due to smaller particle sizes achieved under laboratory conditions. Other, low-cost pretreatment methods also deserve study as a means of allowing lignocellulosic feedstocks to be co-digested in current U.S. anaerobic digesters. [ABSTRACT FROM PUBLISHER]

Sugar production from sugarbeet (Beta vulgaris) generates a co-product stream called raffinate, desugarized molasses, or concentrated separated by-product (CSB). About 0.25 metric tonnes of raffinate is generated for every metric tonne of sugar produced. In this paper, the potential of biogasifying the raffinate to produce methane fuel is investigated. Several aliquots of CSB raffinate (0.1 - 0.2 kg), obtained from the American Crystal Sugar Company, MN, were biogasified in batch mode in a bench-scale anaerobic downflow stationary fixed film reactor (DSFFR) at a thermophilic temperature of 55 °C. It was found that about 0.118 m³ of methane at STP was produced per kg raffinate. This volume of methane was recovered in the biogas within a 2 day period indicating very good degradability. For every kg of raffinate fed into the anaerobic digester about 94 g COD of organic matter will be discharged with the digester effluent along with 27 g of microbial biomass (or sludge). Every metric tonne of raffinate can generate 4,300 MJ (3.7 MMBtu/US ton) of thermal energy from the combustion of the methane or about 300 kWhe of electricity can be generated (assuming 25% efficiency of converting thermal energy to electricity). [ABSTRACT FROM AUTHOR]

The article focuses on the significance of biogas as an alternative viable energy source utilized by some industries in the U.S. It discusses the three methods in producing biogas such as gasification, anaerobic digestion and tapping into nearby landfills. It cites biogas incentives and the challenges of investing into such energy source which carries three risks such as natural gas price and regulatory and operational risks. Moreover, energy budget management is also discussed.

An induced bed reactor (IBR) was developed at Utah State University (USU) to apply high-rate anaerobic digestion techniques to high-suspended-solids content substrates (6% to 12% total solids) such as food waste and dairy manures. This technology has been successfully implemented at multiple full-scale installations in the U.S. and Canada as a waste treatment and energy production technology. A 58 L bench-scale reactor was operated at 55°C with three organic loading rates and three corresponding hydraulic retention times using a dextrose/yeast extract substrate at 30.6 g L-1 COD. Influent and effluent streams were monitored for solids composition, gas quality and quantity, and chemical oxygen demand (COD). Residence time distribution (RTD) was determined using step input tracer studies with rhodamine WT and lithium tracers. The IBR was successfully operated at thermophilic temperatures for 180 days, demonstrating a COD removal rate of 64% and a robust thermophilic culture. Under the conditions studied, the IBR exhibits complete mix behavior with no mechanical energy input. Development of a granulated sludge bed comprising a settled sludge volume of 120 mL L-1 was evident. Further work should be done to determine conditions required for improved solids retention and thus improved performance. [ABSTRACT FROM AUTHOR]

Utilization of food waste (FW) and food processing waste streams in waste-to-energy technologies has increased over the years in United States (US). This review paper compiled information from published literature and open data sources to obtain a holistic view of the current state of FW availability and its management using anaerobic digestion (AD). The review examined the usage of FW as a feedstock for AD by considering the feedstock composition and availability of FW in the US as well as challenges and opportunities with implementing FW in mono- and co-digestion. Also presented are global trends in FW digestion and the current status of FW co-digestion in the US. FW in the US was characterized with regard to volume and composition to show a need for waste management and an opportunity for valuable resource recovery. Challenges and opportunities of processing via AcoD were presented to review best practices for successful operations. Environmental standards, economic incentives, and governmental policies in the US and around the world regarding waste management and utilization were discussed to identify barriers and sources of opportunity for large-scale implementation of AcoD. A range of facilities throughout the US was examined for information regarding digestion type, feedstock(s), biogas production and utilization, and energy self-sufficiency to better understand the current status of FW digestion. Several US facilities were outlined as case studies that co-digest FW and produce and utilize biogas for various applications. Future strategies, perspectives, and roadmaps were discussed to elucidate the shaping of future FW management practices. • Recognizes a need for sustainable management of food loss and waste in the US. • Identifies anaerobic co-digestion as a valuable waste-to-energy technology. • Characterizes food waste as a co-digestion feedstock in the United States. • Discusses barriers and opportunities to implementing co-digestion in the US. • Presents examples of co-digestion increasing biogas yield and generating revenue. [ABSTRACT FROM AUTHOR]

The article shows the role of biogas as one of the energy sources in the United States of America and several European Union countries. The advantages of biogas recovery and increased financial support from state and federal programs have led to a substantial increase in the number of systems in the United States. Great Britain and Germany are the leading European countries in terms of crude biogas production and utilization. Sweden has problems with the inefficient utilization of manure instruments. There is no activity regarding of waste treatment in Spain. A chart of estimated energy production from biogas in the year 2020 is presented.

Most estimates of carbonaceous gas emissions from manure treatment lagoons are based on biogas production from anaerobic digesters, gases collected over covered lagoons, or the CH4 production potential of animal waste. More data from direct measurements are necessary for evaluating mitigation strategies. Researchers at Oklahoma State University have successfully operated a pilot-scale bioreactor consisting of four 270 L columns that recreate environmental conditions found in anaerobic lagoons as indicated by color, temperature, pH, and electrical conductivity (EC). The columns were loaded at a surface organic loading rate similar to lagoons treating manure from commercial swine farms in the state of Oklahoma (935 kg VS/ha-day). The simulated mid-to-late summer CH4 emission rate was determined to range between 200 and 300 kg/ha-day, and the CO2 emission rate ranged between 380 and 580 kg/ha-day. Approximately 65% of the total carbon applied to the surface of the lagoon simulator was recovered as CH4 and CO2 gases; however, lagoon methane production was greater than expected using chemical oxygen demand (COD) as a predictive standard. The daily patterns of gaseous emissions and volatile organic acid concentrations in the liquid suggest that CH4 production takes place across the entire depth of the reactor. Easily digestible organic matter is converted in the upper layers; more slowly digested material settles and is converted at the sludge layer. Data on day versus night emissions show that biogas had a higher proportion of CO2 during the day than during the night. [ABSTRACT FROM AUTHOR]

Food waste (FW) accounts for the largest category of municipal solid wastes in the United States and the proper disposal of FW is a unique challenge with urgent environmental concerns. Solid-state anaerobic digestion (SSAD) is a viable option to treat FW but still hindered by poor mass transfer and severe inhibition caused by the accumulation of acidic intermediates. To improve the treatment capacity and process stability using high-solid FW as the sole feedstock via AD, a bench-scale two-stage system comprising of a first-stage solid-state digester (Stage 1; 2 L) and a second-stage liquid digester (Stage 2; 1.4 L) was established and carried out in a semi-batch mode for 99 days. When one-stage SSAD started to encounter acid accumulation and methanogenesis inhibition at a FW loading of 300 g (15% of working volume), the two-stage system secured robust and stable biogas production when the FW loading continued rising to 400 g (20% of working volume), and an increase of 2.4 kJ/gVS (equivalent to 18.2% in one-stage system) in energy yield was achieved. Stage 1 served as a hydrolysis/acidogenesis reactor with a total acids level of 28.5 g/L and a pH of 5.65. A large portion of lactic acid in total acids indicated shifts of metabolic pathways. The transfer of acid-rich leachate from Stage 1 to Stage 2 ensured a high methane yield of 393.0 mL/gVS (90.2% of the biological methane potential), while the liquid effluent recirculation provided buffering to Stage 1. Further increase of FW loading triggered a system instability. The enhanced buffering capacity and increased free ammonia molecules, synergistically induced certain inhibitory effects on FW acidogenesis in Stage 1. To conclude, the two-stage system outpaced the one-stage SSAD with higher FW loading and energy yield. Image 1 • First-stage solid-state digester and second-stage liquid digester were connected. • Stage 1 served hydrolysis and acidogenesis while Stage 2 served methanogenesis. • Shift of acetic and butyric pathways to lactic pathway was shown in Stage 1. • Food waste loading to two-stage increased by 33.3% as compared to one-stage. • Two-stage outweighed one-stage in specific methane yield by 18.2%. [ABSTRACT FROM AUTHOR]

• A systems-level study aimed at decarbonizing agriculture in the United States. • A synergistic system to convert biogas to dietary protein and ammonia fertilizer. • 30% of dietary protein intake and 127% of ammonia usage could be displaced. The decarbonization of agriculture faces many challenges and has received a level of attention insufficient to abate the worst effects of climate change and ensure a sustainable bioeconomy. Agricultural emissions are caused both by fossil-intensive fertilizer use and land-use change, which in turn are driven in part by increasing demand for dietary protein. To address this challenge, we present a synergistic system in which organic waste-derived biogas (a mixture of methane and carbon dioxide) is converted to dietary protein and ammonia fertilizer. This system produces low-carbon fertilizer inputs alongside high-quality protein, addressing the primary drivers of agricultural emissions. If the proposed system were implemented across the United States utilizing readily available organic waste from municipal wastewater, landfills, animal manure, and commercial operations, we estimate 30% of dietary protein intake and 127% of ammonia usage could be displaced while reducing land use, water consumption, and greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

The U.S. catfish industry is a major industry that has been declining over the years due to imports competition and growing operational costs. Catfish processing wastewater management and high energy requirement put a large financial burden on catfish processing facilities. Recovered protein-based solids have provided some value-added co-products, however, more co-products are needed to offset processing costs. Anaerobic digestion is a proven waste treatment method that produces methane, which is an energetic co-product that can be used within the processing facilities. This study was conducted to evaluate the potential of anaerobic digestion as an alternative to the currently used aerobic biotreatment of catfish processing wastewater. Initial assessments indicated the recalcitrance of the full-strength wastewater to anaerobic digestion, yielding only ~4 m3 per ton (U.S.) of input chemical oxygen demand (CODinput). Thus, several strategies were evaluated to improve the methane yield from the wastewater. These strategies include nutrient (nitrogen and sulfur) amendment, along with ozone, HCl, and NaOH pretreatment. The results showed that nutrient amendment was the most suitable strategy for improving the digestibility of the catfish processing wastewater. A methane yield of 121–236 m3/ton (U.S.) CODinput was obtained, with a purity of 67–80 vol.%. These results are similar to yields and purities of biogas from other feedstock, such as food waste, wastewater solids, and fish canning wastewater. This indicates that anaerobic digestion could be a viable alternative for simultaneous treatment and energetic co-product generation from catfish processing wastewater. [ABSTRACT FROM AUTHOR]

Environmental engineers at Pennsylvania State University have developed a process to produce and collect hydrogen and methane gases from wastewater generated at food processing plants. Using wastewater from a potato chip manufacturer, a confectioner, and an apple processor, the researchers demonstrated that every year these processing plants could produce hydrogen gas worth at least $80,000; this gas can be used as fuel or industrial feedstock. In addition, they estimate that each of the plants could produce enough methane to generate more than 10 billion Btus of energy per year. According to researcher Steven Van Ginkel, extracting hydrogen and methane from wastewater saves the processing plants from having to aerate the water--a process that accounts for 20 to 80 percent of their wastewater treatment expenses.