Co-Composting Green Waste with Dairy Manure

Sustainable Conservation, in partnership with U.S. EPA, Merced County Public Works, and the California Integrated Waste Management Board (now known as the California Department of Resources Recycling and Recovery or CalRecycle) combined resources to develop an innovative manure management project in Merced County demonstrating the benefits of co-composting dairy manure with municipal green waste. Sustainable Conservation has produced a report (see below) that shows co-compost to be of high quality and demonstrates that dairy operators and municipalities can achieve economic and environmental benefits through cooperation.

Report: Achieving Economic and Environmental Benefit Through Agricultural and Municipal Cooperation in Co-Composting Green Waste with Animal Manure

Project Background

The project’s objective was to expand and further demonstrate that manure from a combined animal feeding operation (CAFO) could be successfully co-composted with municipal green waste. Utilizing the existing municipal composting infrastructure in Merced County and manure from a local dairy, this project would provide a replicable strategy to manage manure and green waste for municipalities and CAFOs in California and elsewhere.

The project also intended to demonstrate the benefits of co-composting. Dairy operators, who are faced with the need to export more of their nutrients, will be able to cost effectively export and recycle their waste. This will help reduce nitrate contamination of groundwater that has been found beneath many dairies in the Merced area and will allow dairy operators to comply with CNMP and other regulatory requirements. Simultaneously, municipalities may be able to produce a more valuable compost product leading to increased marketing opportunities. If the municipality can sell co-compost for a higher price than standard green waste compost, the financial viability of the model will be enhanced.

The research consisted of the following tasks:

  • Identify project participants. Sustainable Conservation, working with the Western United Dairymen and California Dairy Campaign, identified dairy producers who were willing to participate in the project. The target hauling distance limits were also determined.
  • Establish partnership. Set formal partnerships with local dairy producers, manure haulers, and Merced County government. Also formalize the involvement of the dairy membership organizations.
  • Initiate contracts and other agreements. To proceed to the implementation phase, it was preferable to have signed agreements up front to avoid possible misunderstandings or confusion between the various parties.
  • Develop a budget. Detailed cost and revenue projections were developed for each project phase encompassing:
    • Transportation—costs of collection and hauling manure and the incremental cost for each additional mile traveled.
    • Processing—marginal operational costs for adding dairy manure and the system capacity without significant new capital investment.
    • Reuse/marketing—marketing and market delivery costs.
    • Reuse benefits—economic and/or crop quality benefits for applying compost on the target market’s fields.
  • Compare projected to actual costs. Assess unit cost of transport, processing, and market delivery as well as new revenue sources and amounts; compare with other management alternatives.
  • Quality control. Perform compost quality sampling and field measurement, where feasible, of compost benefits on target market crops.
  • Documentation. Measure results using key measures including the number of dairymen participating, the volume of manure composted, the revenue increase from material sold, the amount of green waste diverted from landfill disposal, and the number of municipalities looking to replicate the model. Performance measures would include tons of waste diverted from disposal, amount of recycling capacity increased, and amount of increased recycled material utilized.
  • Report. Final reportPDF download summarizing results and lessons learned.

For more information contact: Compost Use in Agriculture,