Good Digestion: It’s Been a Bumpy Road to Full-Scale Adoption of Anaerobic Digestion Technologies at Ethanol Plants

by Holly Jessen (Ethanol Producer Magazine) Despite the promise of methane from anaerobic digestion technology, low natural gas rates and other factors have kept ethanol producers from jumping in with both feet.

...On top of the digester, Western Plains Energy utilizes sorghum, or milo, as a feedstock in addition to corn. In October, the plant received $899,861 for production of ethanol from a renewable biomass, other than corn, through the USDA's Bioenergy Program for Advanced Biofuels program. By putting ethanol production from sorghum and power generation from an anaerobic digester together, the ethanol plant is hoping it will merit an advanced biofuel designation. “The digester gives us a chance to dramatically reduce our carbon footprint and hopefully qualify as an advanced biofuel for our ethanol at the end of the pathway analysis by the EPA,” (CEO Steve) McNinch says.

...The main feedstock for the digester is manure from Pioneer Feeders, a 40,000-head feedlot about six miles from the ethanol plant. All the manure produced at the feedlot will be delivered to the ethanol plant by 25 trucks daily, McNinch says. The ethanol plant has an agreement with the feedlot to return all the organic fertilizer produced at the end of the digester process to the feedlot for the first year, followed by decreasing amounts after that. Eventually, the ethanol plant will market and sell the fertilizer itself.

The fertilizer produced during the digestion process is weed, seed and pathogen free.

...California ethanol plant, Calgren Renewable Fuels LLC, struggled to get local approval for an anaerobic digester after objections by the ethanol plant’s neighbors about odor, impact to air and water quality and possible contamination by pathogens—things digesters actually improve or prevent. The project was put on hold in June, though by November it was tentatively moving forward again pending approval by the county planning commission. In response to those concerns, changes were made to the proposed project, including no trucking of manure, says Daryl Maas, project manager. Instead, it will all be delivered via a pipeline from a nearby dairy. In addition, a pasteurization step has been added at the back end of the digester. The 58 MMgy plant was awarded a $4.68 million matching grant from the California Energy Commission to build the $10 million project. (READ MORE)

...Convincing ethanol plants to move forward with anaerobic digestion is a slow and heartbreaking process, according to David Rein, a process engineer with Rein & Associates of Moorhead, Minn. Rein spoke on the topic at a conference put on by the Energy & Environmental Research Center in July at the University of North Dakota. The company has been conducting bench and pilot studies of biogas production from thin stillage since 2006 and completed feasibility studies that resulted in three separate grant awards to ethanol plants, which ranged from $1.6 million to $3.2 million. All three grants were through the USDA Repowering Assistance Program, which offers biorefineries funding to use renewable biomass as a replacement fuel source for process heat or power. The funding, which would have provided for only a fraction of the full project cost, was ultimately turned down by all three ethanol plants, Rein said at the EERC conference. READ MORE