NACWA and the California Association of Sanitation Agencies (CASA) are collecting information from utilities to support changes to the Renewable Fuel Standard (RFS) program’s classification of fuel produced through co-digestion of biosolids and food waste. This data collection effort, follows a July 27 meeting the groups had with EPA,

The RFS program offers incentives to produce renewable transportation fuels, but its current classification of biofuels creates a disincentive for utilities to consider co-digestion of biosolids and food waste. NACWA and CASA asked EPA to consider alternative methods for classifying biofuel feedstocks to better incentivize the beneficial management of food waste through co-digestion. 

Biosolids-derived fuel is classified as a cellulosic biofuel, which carries a D3 Renewable Identification Number (RIN) in the RFS program. However, if food waste is added to anaerobic digesters to increase the production of biogas, all fuel produced will receive the D5 RIN for advanced biofuel unless the portion of biogas from food waste can be determined. Since D3 RINs currently have a higher value than D5 RINs, utilities’ profits would be reduced by receiving food waste at their digesters.  

NACWA and CASA are proposing that EPA establish a baseline biogas production from sewage sludge. The associations have proposed a baseline value of 15 standard cubic feet of biogas per pound of volatile solids destroyed, with all additional biogas produced by co-digestion assumed to be from food and other organic waste introduced to the digesters. 

NACWA members that have data about biogas produced – with or without co-digestion – are asked to contact Cynthia Finley, NACWA’s Director of Regulatory Affairs, for more information about the data needed to support this effort.