Feasibility study of composting manure

Pepin County, Wisconsin is home to many dairy farms which commonly use animal manure as fertilizer for fields. High concentrations of the nutrients nitrogen, phosphorus, and potassium make the manure an effective fertilizer. However, this can result in runoff containing high levels of these nutrients which can lead to damage of ecosystems, health risks, and bad odor. Aerobically composting the manure is a possible solution and is considered in this report through the lens of environmental, economic and social impacts. The environmental impacts are analyzed by pairing a material flow analysis with a life cycle assessment to quantify the amount of nutrients that end up in runoff and emissions and how much are taken up by the crops. The economic impacts are measured by estimating the capital costs and maintenance costs which are used to calculate the payback period and the net present value. Social impacts are analyzed by looking at pathogen reduction in the soil, the amount of nutrients that leach into the ground from the fields, and the amount of greenhouse gases released which correlates to odor. This analysis found that there was a reduction of nutrients after the composting process which led to lower levels of these nutrients runoff and as emissions. There are financial costs to build the composting structure, but the maintenance costs are reduced with the composting process, which leads to a short payback period for a structure that will last decades. As well, the implementation of the composting process would decrease crop yield, potentially reducing revenue or usable crops for the farm. This analysis determines that the improvements of implementing an aerobic composting system on farms in Pepin County outweigh the associated negatives and that they should be put in place on farms throughout the county.

UniverCity Year Contact Info
Gavin Luter
Managing Director
gavin@cows.org
608-261-1141

University Faculty Contact
Andrea Hicks
hicks5@wisc.edu