Compost: Enhancing the Value of Manure

Findings

In this study, we have examined best-available information on the array of environmental impacts and benefits of manure compost and, more importantly, the interrelationship between those impacts. We found that dairy manure composting has the potential to reduce water quality impacts, improve soils, and reduce greenhouse gas emissions from dairies with comparatively minimal impacts to local air quality.

Dairy manure compost’s portability gives it the potential to disperse nutrient concentrations further distances than manure. While further research is needed to better quantify these impacts, California need not wait to take proactive steps to promote dairy compost when its benefits are clear. Specifically, production of compost for export of manure off dairies appears to be a clear win.

Several key barriers have hindered the production and sale of manure compost and need to be addressed so the practice can be widely adopted. The inconsistency, complexity, and lack of clarity of regulations has been one of the primary barriers to compost production. In some cases, permitting requirements are simply unclear. In other cases, the regulations are based on limited and/or incomplete data and could prohibit better environmental outcomes. In order to establish effective regulatory and incentive programs, there is a critical need to conduct California-based research on the magnitude of the impacts of manure compost relative to current manure management practices.

The current regulatory approach also does not appropriately consider the net impacts from composting dairy manure across water quality, air quality, and greenhouse gases. This siloed approach to managing pollutants on dairies results in lost opportunities to address the most pressing environmental impacts of manure and could actually lead to negative environmental outcomes at a regional scale.

Fortunately, achieving the environmental benefits of manure compost is within reach, as the market for manure compost seems ripe for growth. Demand for compost is robust and expected to increase, particularly in rural agricultural regions of the state where supply of municipal compost can be scarce. Manure compost can help fill this supply-demand gap, but agricultural producers need their customers to support them using manure compost. There is also significant opportunity to increase the supply of manure compost. Dairies are increasingly interested in composting their manure, and producing manure compost seems economically viable for many dairies. However, they need regulations and permitting requirements that are supportive of manure compost production. Table 1 below summarizes our key report findings.

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Conclusion and Recommendations

Based on our research, compost appears to be an economically viable option that enables dairies to reduce their most significant environmental risks. However, we have identified some barriers that are impeding the production and sale of compost. We believe that targeted, short-term efforts by state and local government agencies to address these barriers can enable the market to emerge and grow on its own. We recommend the following specific actions that can be taken by government and associated entities to improve the science, regulatory regime, and market for manure composting while supporting state policies to improve soils and reduce greenhouse gasses. Doing so will help catalyze the market for manure compost, resulting in multiple environmental, social, and economic benefits, many of which will be realized in the San Joaquin Valley.