Sugar Plus CO2 Equals More Ethanol

A microorganism found capable of mixotrophic fermentation converts carbon from both sugar and gas into ethanol.
By Susanne Retka Schill | June 10, 2016

Talking with Bryan Tracy about the underlying science for White Dog Lab Inc.’s technology is an immersion into the molecular level of carbon accounting while simultaneously taking a 30,000-foot view of the challenge of replacing petroleum with renewables. 

As co-founder and CEO, Tracy leads the White Dog Labs team that has developed fermentation technologies trademarked MixoFerm and MixoFermPlus. Tracy describes it as the fermentation technology of the future based on a clostridia microorganism that consumes both C5 and C6 sugars and the subsequent CO2 produced to make ethanol or, if genetically modified, other chemicals.

Clostridia fermentations are not new, having achieved  commercial scale a century ago to produce acetone, butanol and ethanol. In World War I, the British ability to manufacture gunpowder was hampered by German control of calcium acetate mines, the primary source of acetone for cordite gunpowder. A major breakthrough came with Chaim Weizmann’s isolation of a clostridia strain for ABE fermentation (acetone, butanol, ethanol). The process was scaled up quickly, taking over a distillery north of London to supply the British army. Limited fermentation yields, however, ultimately meant  the process didn’t compete well with cheaper petroleum sources for those chemicals in  succeeding decades.

The biggest challenge in competing with petrochemicals is the limitation in mass yield, Tracy explains. Traditional ethanol fermentations require 2 tons of sugar to make 1 ton of ethanol, a 50 percent yield. This is because sugar has a lot of oxygen, and to dispose of the unneeded oxygen, CO2 gas is generated and released. Thus for every molecule of ethanol produced, one molecule of CO2 is produced and released. The quest for cellulosic ethanol has focused on modifying yeasts or finding organisms to convert C5 sugars as well as C6, but the same mass yield limitation still holds.

A second approach taken by companies like LanzaTech, Coskata and IneosBio utilizes clostridia species to consume syngas to produce ethanol or other chemicals. “Carbon monoxide and hydrogen have a tremendous amount of electrons on a per carbon basis that makes them very good feedstocks to convert to ethanol at very high carbon efficiency,” Tracy says. That, of course, requires a lot of energy to turn biomass into syngas and, once again, the fossil feedstock would win out  because shale gas methane currently is the most inexpensive feedstock.

The core discovery made by Tracy’s team at White Dog Lab is a clostridia capable of doing both—a mixotroph. Clostridia are natural soil organisms, Tracy explains, “responsible for fixing CO2 into organic compounds, particularly acetic acid, which other organisms feed off. This is one of the most primordial approaches of fixing CO2 from the atmosphere and putting it into organic material for other organisms.” The MixoFerm process and the MixoFermPlus process, in which extra energy is added in the form of hydrogen gas, can increase the mass yield of a sugar fermentation by about 50 percent, so instead of 2 tons of sugar making 1 ton of ethanol, more than 1.5 tons of ethanol can be produced.

Adding Energy
Tracy dives deeper into molecular chemistry to explain the importance of adding energy, while once again relating that to the big picture. “We’re trying through a biological, sugar feedstock approach to replace petrochemicals and fuels from petroleum, natural gas and coal. These are carbon compounds that are highly reduced—there’s very little oxygen in oil, and lots of hydrogen for every carbon. In the past 100 years, our entire petrochemical industry has developed with these reduced chemicals.” 

“Now we want to replace petroleum with sugar,” he says. To get the sort of base chemicals the petrochemical industry has spent a century developing—ethylene, propylene, butene, butadiene, isoproponal, acetone—the first step is to reduce the oxygen, which requires energy. “The bioeconomy may never come to massive scale fruition for petrochemical replacement unless you’re able to marry up an approach where you get energy into a sugar fermentation. That is the missing link,” Tracy says. Biochemical production economics are hampered by poor mass yields with a few exceptions, such as three acids—lactic, citric and succinic. “Those three are at commercial scale or developing the commercial markets today because they are highly oxidized chemicals—they have just as much or more oxygen in them per carbon as sugar has, so the mass yields are very high—often 100 percent. But those cannot replace the majority of petrochemicals and they can’t be used as a fuel.”

“We want to make a bioeconomy in a world in which the input is not compatible with the output, unless you add energy into the system,” Tracy says. Some microorganisms acquire energy through photosynthesis, which is the mechanism algae developers are tapping into, while some microorganisms fix gas using chemical energy. By adding chemical energy—hydrogen molecules with their freely available electrons—the organism can convert even more of the carbon in the MixoFerm-Plus process, boosting mass yields of ethanol to over 70 percent.

The clostridia produce ethanol natively, Tracy says, which would be an advantage if a first-generation corn ethanol plant were to consider converting from yeast fermentation. Using a nongenetically modified organism would be helpful in getting a generally regarded as safe (GRAS)  designation, which would be necessary for the distillers grains coproduct to be legally sold as feed. “There is nothing harmful about these clostridium,” Tracy says. “You would have to do the trials admittedly, but the protein content and amino acid content compared to yeast is actually very good.” Getting recognized as GRAS is a lengthy process, however, and not likely to be done unless there is some momentum behind it. On the positive side, being able to turn the CO2 into ethanol would greatly improve ethanol’s greenhouse gas impacts. 

Other synergies exist with second-generation ethanol. “With 2G ethanol, we can improve operating expenses and capital costs,” Tracy says. In conversations with ethanol producers, he says current estimates put conventional dry-grind capital cost for a new corn plant at $3 per gallon of capacity and second-generation capital costs at about $10 per gallon. “Not to criticize it, it’s a more complicated process and a new technology,” Tracy says. “The learning curve is going to be climbed.” He acknowledges White Dog Labs will have a similar learning curve, but current estimates for capital costs for its technology are about $6 or $7 per gallon. One advantage to the new process would be providing an alternative use for the lignin coproduct. Rather than burning the lignin for steam or electrical generation—both relatively low-cost in the U.S.—syngas from lignin could be used in the MixoFermPlus process and produce more ethanol, a higher-value product. 

Commercialization Plans
Given current market dynamics and economics, White Dog Labs is focusing on acetone as the first chemical to commercialize, explains investor and executive chairman Sass Somekh. His son, Talli Somekh, is co-founder of White Dog Labs and an executive board member. The pair have financed the project privately since forming White Dog Labs to purchase Elcriton, a spin-out from the University of Delaware led by Tracy that focused on genetic engineering and organism development. The elder Somekh, who has been named to the Silicon Valley Engineering Hall of Fame, recently retired from a 30-year executive career in the semiconductor equipment industry. He describes his son as being a serial entrepreneur with a social conscience who has successfully launched a software company aimed at helping nonprofit organizations. “Nine years ago, the two of us said we need to do our part to help the world reduce its dependence on fossil fuels,” Somekh continues. “I started a company to make a new TV technology—organic light emitting diodes for flexible screens. My son started a computing security company.” With both companies established and operating on their own, the focus has been turned to White Dog Labs.    

Being family-financed, White Dog Labs has operated in stealth mode, Sass Somekh says. “We think of ourselves as industrial technology 2.0, where we’re a very efficient, frugal company. We’re very resourceful, trying to get the same accomplishment but without raising a lot of money that maybe five or 10 years ago, before the global recession, was available for these new startups.” 

White Dog Labs has designed, built and is operating an integrated demonstration facility in Delaware that includes an 18,000 liter fermenter and a 6,000 liter-per-hour liquid-to-liquid extraction (LLE) column and distillation tower. When initially working with biobutanol, the company developed a novel, economical LLE extraction process for separating butanol from the fermentation broth. Ethanol and acetone can be extracted with conventional distillation technology. Given current market conditions, White Dog Labs is focused on acetone and isopropanol (IPA) production, with demonstrated improvements in fermentation yields of about 50 percent using the MixoFerm process compared to a traditional sugar-only fermentation.

Readying to launch publicly, the team of researchers has had peer-reviewed papers published on its work, and is looking forward to a paper to be published in a prominent journal this summer.  In May, White Dog Labs was named among a group of six projects to receive up to $10 million in funding through the DOE Bioenergy Technology Office “to develop renewable and cost-competitive biofuels from nonfood biomass feedstocks by reducing the technical risk associated with potentially breakthrough approaches and technologies for investors.”

Plans are to build a 15,000 ton per year plant (5 MMgy) to produce acetone and IPA for the high end pharma and personal care markets that require no petroleum contamination. The feedstock would be over-the-fence dextrose purchased from an existing corn wet mill. Target startup is for 2018. A longer-term plan is to start production in 2020 at a 75,000 ton per year (25 MMgy) acetone-IPA plant. The company has completed the initial design of the $150 million facility and applied for a U.S. DOE loan. It has passed Part 1 of the application process and been invited to submit the final Part 2. Sites in Minnesota and South Dakota are under consideration and a letter of intent for acetone offtake is in place with a major chemical company interested in reducing its carbon footprint. A preliminary life-cycle analysis of the corn-based acetone field-to-customer greenhouse gas emissions indicates a 154 percent reduction when compared to petroleum-based acetone. 

Somekh is excited to go public with White Dog Lab’s project development. “This is the next step to bring fermentation to a much higher level of efficiency,” he says. For ethanol, improvements have become incremental, but the company’s technology could boost yields from 50 percent ethanol out of a ton of sugar, he says, to more than 70 percent. “This would be a quantum jump.”

Author: Susanne Retka Schill
Managing Editor, Ethanol Producer Magazine