The Inland Empire Utilities Agency of California retained Tetra Tech to find a solution to management issues for organic solid waste within the 250-square-mile region. The service area is populated by approximately 600,000 people and has one of the densest concentrations of dairy animals in the United States (about 360,000 animals in the area). Approximately 1.2 millon tons per year of organic solid wastes are generated in the area, with 85 percent consisting of manure from dairy cows. In addition to the waste management and disposal issues, the manure was adding a significant amount of salts and nitrates to the groundwater aquifer and was impairing the Santa Ana River Watershed.

Tetra Tech assembled a team of professional engineers, water quality experts, urban planners, environmentalists, and dairy industry specialists to identify solutions, technologies, and innovative marketing of byproducts. The study is one of the largest organics management studies and design projects in the United States that deals largely with animal waste. Project activities included:

• Located suitable sites for treating and processing up to one million tons of organic solids per year
• Identified innovative and effective processes for solids stabilization, considering solids conveyance methods (truck and rail transport), collection and stabilization processes for solids, and production of marketable products
• Designed an enhanced anaerobic digestion system to produce methane from the waste stocks and generate electricity and compost residuals for sale as a fertilizer and soil conditioner
• Prepared a business plan focusing on markets for the organic byproducts, such as compost, heat, electrical power, carbon dioxide, and a variety of soil amendments and nutrients

Two leading-edge dairy digester pilot projects were implemented as a result of the comprehensive organics management plan. The two projects serve the nutrient management needs created by more than 30,000 head of cattle while generating renewable energy, reducing greenhouse gas (GHG) emissions, and creating useful compost products. The organics management plan has generated more than $30 million in federal, state, and private investment and grants to support program implementation. The project also included extensive interaction with the regulatory agencies, community outreach, and coordination with multiple stakeholders in the surrounding three-county area.

Highlights:

• Addressed groundwater contamination and odor issues from dairy farm operations
• Produced electricity and compost as new products and revenue sources from a underused waste stream
• Reduced carbon dioxide (CO₂) and methane emissions