6920 Salashan Pkwy. A-102, PO Box 2708
Ferndale, WA 98248
Ph: 360.366.9900 - Fax: 360.366.5800
Unprocessed cow manure, a renewable resource, is collected in a receiving pit. During the first stage of DVO, Inc.'s anaerobic digester, the raw manure from the dairy is mixed and heated to a temperature of 100 F. In the second stage of the anaerobic digester vessel, the methanogenic bacteria convert the volatile fatty acids produced in the first stage into biogas, which consists primarily of methane (CH4, same as natural gas) and CO2.
The methane biogas is collected and utilized for fuel in the combined heat and power genset. This genset is a commercially available, natural gas-fueled reciprocating engine modified to burn biogas. Electricity produced is sold to the local utility and utilized on the farm as a substitute for currently purchased power. Excess hot water from the system will also be used to heat various dairy locations. No seasonal variations are expected in the system.
The digested manure is pumped from the effluent pit at the end of the anaerobic digester vessel to a manure solids separator. The mechanical manure seperator separates the effluent digested waste stream into solid and liquid fractions. The solids are dewatered to approximately a 25% to 30% solid material. The separated solids, having the same odor and pathogen reduction characteristics as the liquid stream, are utilized by the dairy for bedding replacement (an expense reduction). Utilization of the separated solids for bedding typically comprises 50-60% of the generated separated solids from a typical dairy. The residual 40-50% of non-utilized separated solids is sold (system generated income) to other dairies for bedding purposes, or sold to after-markets, such as nurseries and composters, for soil amendment material.
The liquid from the manure seperator, now with the majority of the large solids removed, flows into the dairy's storage lagoon. A large advantage of the effluent from the anaerobic digester treatment process is that the viscosity of the effluent is such, as opposed to the raw manure influent, that the liquid effluent can be pumped through an irrigation nozzle for field spreading. Another benefit is the reduction of phosphorous, nutrient, and pathogen loading when spreading.