Digesters may be:
- Built, operated and used by a single farm with the effluent utilized on that farm.
- Located on a farm but also receive materials from other farms or waste sources with effluent used on the receiving farm or also trucked back to other contributors.
- Owned by the farm and operated by the farm or by a digester management and operation service.
- Owned and operated by an off-farm company but located on the farm.
- A centralized (community) digester may be located so it can receive manure and other organic materials from several farms or other sources with the effluent further treated for non-agricultural use or trucked to and spread on crop land.
Centralized (Community) Digester:
This type of system would benefit farmers that cannot individually construct and operate an anaerobic digester manure handling system on their own due to the capital expense or just don’t have the number of animals required to operate a digester successfully or cost effectively. Farms located close to each other could share the cost of the centrally located digester system. The centralized digester operated by an individual or private company would carry out the operation and maintenance of the digester and its mechanical systems. The centralized digester would have the same advantages as on-farm digesters of odor reduction, pathogen and weed seed destruction, biogas production and a stable effluent ready to fertilize fields and crops.
Depending on the location and distance from the farms using the digester the feed stock and effluent could be piped or transported by trucks. The effluent could be land applied immediately or stored for future use. The biogas can be used to warm the digester and/or produce electricity to sell to the local power company. Separated and digested solids after composting can be used by all the participating farms as bedding for their animals and the excess sold as fertilizer and soil amendments. There are many options to consider for the design and operation of the centralized digester. An important consideration will be effluent utilization and or disposal, it may be land applied or further processed to produce bedding or soil amendment material. Composting and electric power production can also be a part of the system. A centralized digester operated with specific end products in mind can create jobs for the local community. The farmers get a manure management system and stable, practically odorless nutrient rich effluent for field and crop application. The community benefits from the odor reduction, value added by-products and jobs a centralized digester can create.