Barham Farms - Complete Mix
| Location | Zebulon, North Carolina |
| Project Type | Farm Scale |
| Animal Type | Swine (farrow-to-wean) |
| Baseline System | Storage Lagoon |
| Digester Type | Complete Mix |
| Co-Digestion | Food waste |
| System Designer | Slurrystore tank installation by Julie Barham |
| Biogas Use | Boiler/Furnace Fuel |
Photo: North Carolina State University
When the owner of Barham Farms became interested in reducing odors and improving water quality in 1995, he contacted the AgSTAR program. AgSTAR provided design and technical support for the installation of a covered in-ground digester and methane recovery and utilization system.
Manure from the pull plug pit is first treated in an in-ground ambient temperature anaerobic digester, from which biogas is extracted. When the project began in 1997, a 120 kW engine generated electricity for on-farm use as well as for sale to the local utility. Waste heat from the unit was used to produce hot water to heat pig mats under the farrowed pigs, displacing the use of heat lamps. However, the inability to secure a mutually beneficial contract between the farm and the utility has forced the shutdown of the generator element of the project in 2003.
Effluent from the digester flows to a second-stage storage lagoon. A trickling nitrification biofilter treats a portion of the stored effluent that is used to recharge the pits. While some of the treated wastewater is applied to coastal Bermuda grass, the majority is piped to two 28,000 ft2 greenhouses. An automated irrigation system applies about 12 m3 per day of the nutrient-rich wastewater to the tomato plants, which produce about 1,500 pounds of marketable fruit each day.
Barham Farm's digester includes the following benefits:
- Odor is virtually non-existent, reducing impact on large subdivisions less than a mile away
- Manure treatment and nutrient application complies with manure management regulations, saving additional investment
- Stored wastewater provides nutrients for the greenhouse operation, which produces a value-added product and reduces the application of digester effluent to the spray fields
Project Update:In 2012, Barham Farms installed a new complete mix digester to handle additional feedstocks. Gas from both the covered lagoon and complete mix digester is used as boiler fuel to provide heat for the digester and greenhouses.