Kansas ethanol plant poised to start up anaerobic digester soon

If all goes as planned, a 50 MMgy ethanol plant in Oakley, Kan., will someday produce advanced biofuel from sorghum. To qualify as advanced biofuel, the company will power the plant with methane from its anaerobic digester system as well as utilizing other advanced technologies.

There are several things that must fall into place before that happens, however. First, Western Plains Energy LLC needs to complete startup of its digesters—which it is poised to do soon. In fact, the company had planned to begin operations the day after Christmas but that was delayed due to weather conditions. “We are currently doing further thermal protection and will start up next week,” CEO Steve McNinch told Ethanol Producer Magazine on Dec. 27. “We want to make sure if we have to stop after we start that the plant is safe from freezing.”

At full digester capacity, which the company expects to reach in March, the digesters will produce enough methane to completely refire the plant’s thermal oxidizer and boiler. In other words, the facility won’t need to use any natural gas and could someday even generate its own electricity with additional equipment. “The main focus right now is just getting the plant’s boilers off of natural gas and on methane but it’s certainly something we’re looking at moving forward,” he said.

The U.S. EPA published a final rule for a grain sorghum fuel pathway in the Federal Register on Dec. 17. As expected, dry mill ethanol plants using natural gas and sorghum meet the lifecycle greenhouse gas emission reduction threshold of 20 percent, compared to petroleum fuel, qualifying it as a renewable fuel. However, ethanol plants using specified forms of biogas energy for process energy and all but 1.5 kwh electrical power per gallon of ethanol qualify as an advanced fuel with more than 50 percent reduction, compared to petroleum.

Although Western Plains Energy will have an operating digester, to qualify as an advanced biofuel producer the final rule also calls for combined heat and power (CHP,) which the company does not utilize, McNinch said. However, the company does have other advanced technologies in place and petitioned the EPA for a separate pathway a little more than a year ago. With the final rule now published in the federal register the EPA can rule on Western Plains Energy pathway. “I believe they will rule favorably but it’s not final until they sign it,” he said.

In the past, Western Plains Energy has used a mixture of corn and sorghum—commonly known as milo—however, the plan is to switch over to 100 percent milo when the digesters reach full gas capacity. “We’ve been 100 percent milo more often than we’ve ever been 100 percent corn,” he said. “Milo has kind of been our niche all around. When you live in a desert you have to use what grows well and grain sorghum certainly grows well here. It’s much more drought tolerant.”

Western Plains Energy received a $15.6 million grant from the Kansas Department of Commerce, which it used to help build the digester system, installed by Himark biogas. Although the project was estimated to cost between $35 and $40 million, the final tally is somewhere upwards of $40 million. Still, McNinch said he doesn’t expect future digester projects to be that expensive. “There was a lot of engineering being done as we were building,” he said.

The digester will primarily be fed with manure from a local feedlot. Other ingredients include thin stillage from the ethanol plant and food waste. Although there is interest in powering ethanol plants with biogas, full-scale adoption of the technology has been slow.