Ventura County, CA, USA -- Ventura County, Calif., produces approximately 8,000 tons of biosolids per month. Prior to this project, 90 percent was trucked out of the county for disposal, primarily to Kern County, a 300-mile round-trip. Growing opposition to land application of imported biosolids in Kern County inspired Ventura Regional Sanitation District (VRSD), in cooperation with Ventura County cities, to create a local biosolids management solution.

Drying biosolids to approximately 75 percent solids, beyond the 15 to 20 percent solids typical at wastewater treatment plants, was recognized as the best way to create a workable, pathogen-free biosolid that could be used as cover at the Toland Road Landfill in Santa Paula, with potential future use as fertilizer or fuel. A biosolids drying system was developed to meet the long-term disposal needs of Ventura County in an economical, environmentally responsible manner.

The growing quantity of landfill gas (LFG) at Toland Road Landfill was seen as a way to reduce costs for natural gas and electricity: primary dryer operating costs. LFG would fuel process heaters, which in turn would heat oil to indirectly dry the biosolids. The LFG would also be used as a fuel to generate electricity which would provide the dryers' electrical needs.

The biosolids drying and electrical generation technology would ideally be modular, allowing easy up- or downsizing, depending on the number of cities interested in contracting with VRSD and considering the increasing LFG output for electrical generation. The modular approach allows use of standard equipment models, instead of custom design/fabrication and the accompanying cost/operational problems.

A system of condensing, treating and using the reclaimed water extracted from the dryers' exhaust steam had to be developed. (This process typically occurs at wastewater treatment plants where high flow water spray is used to condense steam, with the resulting wastewater routed into the treatment plant's headworks; not possible at a landfill.) Microturbines were chosen as a modular, low-emission, simple-operation (no contract operator needed) approach to generating power.

A Self Generation Incentive Program (SGIP) grant from the local electric utility (Southern California Edison) helped finance the project. The SGIP is provided to promote self-generation of electricity. This project creates over 750 kW of load, which is completely offset with dedicated on-site microturbine power generation, which equates to nearly a $1 million grant.

At full capacity, VRSD's Biosolids Drying and Renewable Power Generation Facility will:

Dry 320 tons of biosolids daily

Produce AB 939 recyclable material with multiple uses including alternative daily cover for the landfill, fertilizer or fuel

Generate 3.25 MW of renewable/green power (1.5 MW for onsite demand and 2.25 MW for export)

Reduce truck traffic up to 1 million miles a year by disposing of biosolids locally (compared to previous longer haul to Kern County) and decrease related greenhouse gas emissions by up to 1,800 tons annually

Reduce the demand on existing conventional power generation facilities, thereby offsetting up to 15,000 tons of fossil-fuel-based carbon dioxide annually

Provide Ventura County with a local biosolids management solution

Serve as an innovative LFG-fueled regional biosolids drying system that can be replicated in other communities.

This regional biosolids drying solution is among the first of its kind in the nation. A compact, modular system, it can easily be replicated in other communities.

renewableenergyworld.com