Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
Biological Systems Engineering
Non Technical Summary
Waste management is becoming increasingly important for economic and environmental sustainability in industrial, agricultural, and municipal sectors. Anaerobic digestion is a proven waste-to-energy technology currently being implemented to produce renewable energy and stabilize waste to limit environmental impacts. Use of AD systems within the United States is increasing rapidly. In order to maintain economic viability, systems are being optimized for increased gas production and use of end products. The change in management, design, and operation results in unpredictable environmental impacts. The proposed research uses a systems approach to analyze economic and environmental impacts due to changes in AD operation. A framework will be developed to perform an LCA to determine impacts of GHG emissions, land use, nutrient losses, biogas production, and food production for changes in AD operations including substrate, digestate, and energy use. A parallel economic analysis will also be evaluated for comparison to the LCA for environmental impacts. Simultaneous assessment will highlight areas with high potential impact for AD operation and research. The analysis will provide direct data for application to operational systems to realize environmental and economic benefits, while increasing knowledge for design of future systems.
Animal Health Component
80%
Research Effort Categories
Basic
20%
Applied
80%
Developmental
(N/A)
Goals / Objectives
1.Design framework for analysis of AD system components and their environmental and economic impacts. 2.Simultaneously analyze AD systems to quantify overall economic and environmental impacts for alternative substrates, digestate end products, and biogas use. 3.Identify gaps in data and analysis procedures to strengthen framework and outline future data collection needs. Development of a framework for systems analysis will provide the necessary tools to quantify environmental and economic impacts for assessment. Simultaneous systems analysis for economic and environmental impacts will identify areas which pose potential for reductions in economic cost without negatively impacting environmental benefits. Typical systems today are evaluated for economic feasibility, but the alterations to these systems can produce unpredictable environmental consequences. Data can be used to weigh these options appropriately before making management, operational, and design changes. Further breakdown of this data for substrates, digestate end use, and biogas use has direct application to those currently operating AD systems to reduce emissions, reduce land use impacts and nutrient losses, and increase biogas production. Completion of this study can influence actual environmental and economic impacts through dissemination to digester operators, particularly with the addition to the curriculum of the anaerobic digestion operator training program and other information tools. With detailed inspection of data pertaining to GHG emissions, nutrient use, net energy, land use, crop production, waste production, etc., research needs will be highlighted. Leveraging further funding requires data to assess the research needs and areas of AD with the greatest potential for increased impact, whether that is more detailed emissions data, greater understanding of biogas markets, or the numerous other potential concerns. Currently, general surveys of existing operations are used to assess the next steps for research, but impact analysis will focus research in areas where results will be most effective in an attempt to make gains in the gap between AD application and proven science.
Project Methods
Environmental impacts of climate change, land use, and energy intensity will be assessed using life cycle analysis (LCA) models that will be developed using GaBi software, a leading LCA management program. Through this methodology it will be possible to identify the potential environmental and economic trade-offs that exist along the lifecycle of the studied AD systems. The basic framework, databases, and libraries developed by the Green Cheese Project at UW-Madison (Passos-Fonseca et al. 2010) will be adapted to determine net energy production, emissions, nutrient balances (including phosphorus and nitrogen), and land use requirements for the AD system scenarios. The processes involved will include (1) substrate production including all requirements from crop production (when applicable) to digester, (2) AD operation, (3) digestate production and use, and (4) biogas production and use. Analysis will evaluate outputs for a defined digester volume (to avoid complications with digester construction impacts) and user defined systems including substrate type, digestate use, and biogas use. This user defined information will then be used to calculate the outputs using embedded programming. Substrate selection will determine the volume of biomass needed, the agricultural production system(s) required to produce that biomass or substrate and their embedded energy requirements, the environmental impacts of agricultural production, and the biogas production from that particular substrate. Digestate use will have environmental impacts associated with transport and application or end use of waste. Biogas use will be used to calculate the environmental impacts associated with different end use schemes (natural gas or electricity). The resulting data will be aggregated for each scenario to determine the overall output impacts for each process for comparison. A cost-benefit analysis will be used for the same system scenarios outlined in the environmental LCA. Costs will be identified with each of the processes including agricultural production of each substrate (i.e. cost of required land, cropping), digestate end use (transport, digestate markets), and energy use (capital and operational costs, market price). The economic benefits of a digester are defined by several factors include electricity avoided, electricity sold, bedding savings, and separated solids sales. Potential benefits generated from carbon credits and government support policies such as feed-in-tariff will also be incorporated to assess the profitability of the system under alternative assumptions. Evaluation of each set of data, economic and environmental, for AD system scenario will allow for assessment of trends and correlations in data sets.