As the U.S. leader in anaerobic digestion, GHD's patented two-stage mixed plug-flow digesters process more farm waste than any other — with unparalled performance. Our systems greatly reduce the odor on farms, are cost- effective, operate automatically and require low maintenance.
GHD, Inc. has been a leader in environmental engineering for over 17 years, providing reliable, proven solutions for farmers. Unique to our industry, every GHD digester installed is still in operation today.
The patented two-stage digester converts manure and other organic wastes into three valuable byproducts: a biogas, which can be burned in a genset to create electricity or scrubbed to make natural gas; a biosolid, used as a high-quality bedding for cows or as a soil amendment; and a liquid stream that is non-odorous and can be applied as a fertilizer to growing crops.
GHD's anaerobic digester can handle various animal waste streams, including waste from dairy, swine, and poultry operations. Other types of organic wastes can be digested in GHD's digester, such as fats, oils, sugars, starches, etc.
The system can be implemented at agri-businesses with organic wastes such as meat packing plants, dairy plants, and vegetable processors as well as municipal sewage treatment plants and other waste treatment facilities.
Our digesters are designed to be operated by the farmer, are simple to maintain and, above all, are optimized for on-farm reliability. Advantages of a GHD digester include:
- Efficient electricity generation
- Quality bedding without composting
- Excess heat for farm use
- Odor reduction
- Increased fertilizer value
- Pathogen reduction
- Weed seed reduction
- Low maintenance
- Proven technology
- Low operation costs
- Fly & vector control
GHD's Services Include:
- Engineering & Design
- Utility contact
- Equipment specifications
- Complete system oversight
- System start-up
- System maintenance
The methane biogas is collected from the first two stages of the AD vessel and utilized for fuel in the combined heat and power (CHP) gensets. These gensets are commercially available, natural gas-fueled reciprocating engines modified to burn biogas. The electricity produced by these gensets can be used to offset on-farm power consumption; excess power can be sold directly to the utility as a source of green power.
The waste heat, in the form of hot water, is collected from both the engine jacket liquid cooling system and from the engine exhaust (air) system. Approximately 30 to 60% of this waste heat is utilized in the AD system. The remaining waste heat can be used by the farm as a replacement for hot water production (reducing the need for natural gas or propane purchases) and for in-floor heating of the farm and holding areas, as required.
The digester effluent is pumped from the effluent pit at the end of the AD vessel to a manure solids separator. The mechanical manure separator separates the influent digested waste stream into solid and liquid fractions. The solids are dewatered to approximately a 35% solid material. The separated solids, having the same odor and pathogen reduction characteristics as the liquid stream, may be utilized by the farm for bedding replacement (an expense reduction). Use of the separated solids for bedding typically comprises about 40 to 60% of the generated separated solids from a typical farm. The residual 40 to 60% of non-utilized separated solids may be sold (system-generated income) to other farms for bedding purposes or sold to after-markets, such as nurseries and composters, for soil amendment material.
The liquid from the manure separator, now with the majority of the large solids removed, gravity flows into the farm’s storage lagoon. A large advantage of the effluent from the AD 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.