HRS energy-efficient multieffect digestate concentration system
The EPA also indicated that as the AD sector grows, it may provide additional benefits and help deliver cross-agency strategies on food waste and agricultural efficiency, for example.
Anaerobic digestion from wastewater potential
According to the Water Environment Federation (WEF), Hawaii, Washington and California have the highest percentages of WRRFs that process solids through anaerobic digestion, while New Mexico, Illinois, California and Hawaii have the highest percentages of wastewater flow being treated by AD. The most common use of produced biogas is for digester heating (some 48 percent of WRRF anaerobic digestion facilities use gas in this way), and then building heating, power generation or driving process machinery (8 percent), with just 1 percent used for pipeline injection.1
The National Renewable Energy Laboratory (NREL) suggests the wastewater sector could produce as much as 2.3 million metric tons of biomethane a year.4 Other estimates suggest the U.S.’s aging water infrastructure will require an investment of about $600 billion over the next 20 years if it continues to reliably transport and treat wastewater.5 Many older wastewater AD facilities are now in a position to upgrade and take advantage of the latest technology. All of this means is, there is a huge potential to increase energy production from America’s wastewater sector.
When the potential codigestion of food waste is considered, the economics of green gas production become even greater. Research at California State University suggests that mixing 25 percent food waste with 75 percent municipal wastewater sludge can increase biogas production by as much as 60 percent compared to digesting sewage alone. With only a fraction of sites currently codigesting other wastes, the potential for the sector to capitalize is significant.