Infrastructures for Organic Waste Management

Livestock waste (manure) generated at U.S. animal feeding operations is estimated to be 300 million tons per year. This is twice the amount of waste produced by the entire U.S. human population.  Most of this waste is disposed of in lagoons or stored outdoors to decompose, leading to numerous environmental issues that include greenhouse gas (GHG) emissions (methane and nitrous oxide), eutrophication of watersheds resulting from phosphorus runoff, and human exposure to pathogenic bacteria. The production of biogas from waste through anaerobic digestion provides a promising avenue to mitigate these issues. The EPA's AgSTAR program reports that about 8,000 U.S. farms could support biogas systems, providing about 1,670 MW of electricity (enough to power one million homes) and reducing methane emissions by 1.8 million metric tons (in carbon dioxide equivalent this corresponds to taking 6.5 million cars off the road). The development of biogas infrastructures, however, has been historically difficult. According to the American Biogas Council, there are only 247 digester farm installations in the U.S. Limited adoption is the result of high technology costs, competing prices of natural gas obtained from non-renewable sources, and limited government policies and incentives. 

To address these challenges we are: i) Developing comprehensive optimization models and solution algorithms to identify new efficient pathways for waste-to-biogas systems. This will be achieved by capturing system-wide interactions between waste processing, nutrient management, and natural gas, electricity, and transportation infrastructures.  ii) Developing decision-making frameworks that factor in the interests of multiple stakeholders on conflicting objectives (investment, emissions, land/water conservation) and that use new consensus metrics to identify Pareto efficient compromise solutions. Stakeholders include urban and rural communities, environmental groups, farmers, technology providers, and local/regional governments.  iii) Performing real case studies using data from the State of Wisconsin to demonstrate the potential of new waste-to-biogas pathways under different government policies and incentives. We are collaborating with Dr. Ruiz-Mercado of the U.S. EPA to identify suitable policies that can accelerate adoption of waste management technologies. 

Dairy-Water-Energy Nexus