The following is an excerpt from the above pdf, which outlines why more Utility companies should consider installing Anaerobic Digestion Wastewater Treatment Facilities at sewage works:
Existing Infrastructure – Many wastewater treatment facilities in the Pacific Southwest (US Region 9) and across the country, use anaerobic digesters to reduce the volume of the biosolids (sewage sludge) before they are taken off site. The anaerobic digesters produce biogas which is either flared or used onsite as an energy source. Therefore, the energy capturing infrastructure is already in place at many facilities.
Existing Expertise – Wastewater treatment facilities already have the on-site expertise and years of experience dealing with anaerobic digesters; vessels that are difficult to operate without thorough knowledge.
Located in Urban Areas – Wastewater treatment facilities are often located in dense, urban areas, where compost facilities are not. It makes logical sense for a highly populated area to ship organic waste to a nearby anaerobic digester where the energy content is recovered and the volume reduced. The residual can then be trucked to compost facilities, which are typically located farther from urban areas. via USEPA.
However, there are many things to remember before immediately discounting this technology based on cost.
Payback period: Although the initial costs may be large, the digestion of food waste can be quite lucrative and the payback period can be less than three years depending on the existing
infrastructure at the wastewater plant.
When a facility accepts food waste at a plant, they can charge the waste hauler a tipping fee for accepting the material. In addition, there is a significant amount of money that will be saved in energy avoidance due to methane production.
The excess energy can be sold back to the grid for profit. This article is provided via USEPA.
The full article is here.