Deep dive in Coskata’s bacteria-based ethanol

Secretive biofuel startup Coskata has opened up about the bacteria-to-ethanol technology at work in a new demonstration plant in Madison, Pa.

Bill Roe, CEO of Warrenville, Ill.-based Coskata, took the Cleantech Group on an exclusive behind-the-scenes tour of the new plant that turns wood chips into ethanol using a continuous, three-step process that takes mere minutes from start to finish.

See the plant »

The demonstration facility was completed for a little less than $25 million and produces 100 gallons of ethanol from one ton of dry feedstock, which is helping reach its goal of production for less than $1 per gallon, Roe said.

Read about Coskata's business plans »

So far, the facility has only used one feedstock, wood chips, but Coskata plans to test agricultural waste, energy crops, and construction waste during the coming weeks.

“The corn ethanol pioneers did excellent work in jump-starting the industry, but they were limited by the fact that they relied on a single feedstock,” Roe said. “Having a wide variety of feedstocks is the key.”

See the wood chips being fed into the gasifier »

Coskata’s first step, plasma gasification, employs technology from Alter NRG's (TSX:NRG) wholly owned subsidiary Westinghouse Plasma, to produce syngas from any carbon-based feedstock. That syngas can be used to produce power, steam, or ethanol. The first plant using Westinghouse Plasma’s technology was opened in 1999 by Hitachi Metals in Yoshi, Japan, to turn municipal solid waste into power.

See the plasma gasification »

The resulting syngas is cleaned using a cyclone separator and a wet scrubber. The syngas is also cooled from 2,500 degrees Fahrenheit to about 100 degrees using heat exchangers and other technology, said Hector Cruz, vice president of engineering for Westinghouse Plasma.

See Cruz in the control room » 

The cleaned and cooled syngas is then fed into Coskata’s proprietary conversion process. The syngas flows through a series of bioreactors, in which bacteria ingest carbon and hydrogen, and excrete liquid that is distilled to ethanol.

See the bioreactors and distillers »

Coskata’s two separation tanks use distillation and dehydration to isolate the ethanol, but the company plans to install a third reactor in November that tests membrane separation technology. Roe called membrane separation the “holy grail” because it could cut energy consumption by 40 percent to 50 percent.

Key to the process is clostridium, a prehistoric, anaerobic bacteria typically found in deep freshwater ponds. The subspecies is homoacetogens, which only produces ethanol. The homoacetogens can make ethanol two ways: from carbon monoxide and H₂O, or from hydrogen and CO₂.

See the bacteria »

Coskata licensed the original cultures from the Oklahoma Biofuels Consortium. Coskata developed bioreactors for the process and maximizes the output of its bacteria through microbiological work and strain management.

“We’ve made them into super athletes,” Roe said.

A cubic centimeter of liquid solution would hold billions of the cells, Roe said. The bacteria have a lifespan of a matter of days, and Coskata purges the population to make sure the population doesn’t evolve.

Roe said Coskata could engineer the metabolic pathway of its proprietary bacteria in order to produce butanol or specialty chemicals, a smaller but highly lucrative market, but the company is laser focused on ethanol.

“We suppress that because we don’t want other things; we want only one thing: Ethanol,” he said. “That doesn’t mean we don’t have other tricks up our sleeves.”

Coskata’s process is a cross between enzymatic hydrolysis to decompose feedstock into sugars and ferment to create alcohol, and thermochemical, in which gasification is followed by reaction with a man-made catalyst to create ethanol.

“These are all based on good science, sound science, but there’s inherent flaws with both of those and we’ve tried to take the best of both,” Roe said.

Roe said the process is net energy positive, but he declined to specify how much excess energy is produced. The process is low temperature and low pressure, which reduces operating costs, he said.

Roe said Westinghouse’s process also harnesses excess heat energy liberated during the gasification process.

Alter NRG’s Chief Marketing and Sales Officer Richard Fish said the plasma gasification technology is very efficient, retaining 80 percent of the energy in the feedstock in the process.

The 8,000-degree Fahrenheit plasma torch uses 2 percent to 5 percent of the system’s energy input.

Coskata says Argonne National Laboratory vetted its process in late 2007 and early 2008, concluding it offered a 96 percent reduction in greenhouse gases compared to traditional petroleum fuel. By comparison, sugarcane ethanol offers a 78 percent reduction, Roe said.

Coskata claims the process also uses less water than other fuels. It has designed a facility with annual production of 55 million gallons, and Roe says the plans call for it to use 1.3 gallons of water per gallon of fuel, while U.S.-sourced gasoline requires 3.4 to 6.6 gallons of water, and Saudi-sourced gasoline requires 2.8 to 5.8 gallons.

“We think that’s going to be very, very important in the future,” Roe said.

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