A more sustainable fuel: Chris Todd Hittinger experiments to produce fuel from yeast

This article, by Monica Ridlon, is part of a series highlighting members of the Office of Sustainability’s Experts Database. In a collaboration with instructor Madeline Fisher’s course, LSC 561: Writing Science for the Public, students interviewed campus sustainability experts and produced short feature stories. 

Chris Todd Hittinger profile photoIn a society dependent on fossil fuels, how do we keep these non-renewable resources in the ground? Scientists at the University of Wisconsin–Madison are working on the answer.  

Chris Todd Hittinger, an expert in yeast genetics at the University of Wisconsin–Madison, is working with yeast, utilizing it to make fuel to replace what we get from fossil fuels. Today’s process of extracting and processing fossil fuels is both expensive and systematically harmful for people and the environment. 

“We need to be able to [produce fuels] in a way that doesn’t produce greenhouse gases and doesn’t deplete the fossil fuel reserves,” Hittinger said. 

Contrary to the current methods of producing fuel, using yeast would be nearly carbon neutral. This is because the yeast would eat plants to make the fuel products. The process of yeast creating the fuel could be done virtually anywhere while avoiding the release of toxic impurities. Therefore, these yeasts would be creating a sustainable source of fuel.

Global economies and societies rely on fossil fuels to meet their energy infrastructure needs, but fossil fuels are not renewable. So when they run out, we have no way to regenerate them. And even if we could find endless fossil fuels, issues for environmental and human health would still remain. 

“[Fossil fuel products] need to be replaced, and the economics need to work out so [alternative energy sources] can compete with an industry that externalizes their costs to all of us,” said Hittinger.

In short, our process of energy production is costly and unsustainable. 

We can use fossil fuel products such as gasoline, diesel, and jet fuel as energy sources mainly because they are packed with molecules called hydrocarbons that can be broken down. In that process of breaking down, the molecules release large amounts of energy that we can use to power our lives. It’s easy to break down hydrocarbons to release energy, but it’s much harder to build up hydrocarbons to contain more energy. It took millennia for ancient sources of fossil fuel reserves to become usable energy sources, and we aren’t getting more anytime soon.

On a shorter timescale, plants regularly build up energy-rich carbon-containing molecules through their metabolism, but microbes like yeasts don’t naturally convert all the carbon to fuels and bioproducts. That is, unless someone uses science to kick their metabolism into overdrive.

Hittinger is working with yeast to do just that, hijacking their metabolism to make energy-rich hydrocarbons that society can one day use as an energy source. The yeast would create isobutanol, which can be used directly as fuel or catalytically upgraded to hydrocarbons, such as sustainable aviation fuel. And since the fuels from yeast would be the same as fossil fuel products, they could be distributed and used by consumers without any changes to current infrastructure. 

Using yeast to meet our liquid energy needs may seem easy enough, but it is no simple task. The yeast would need to have a particular metabolic pathway to produce excess isobutanol from plants while withstanding industrial conditions such as high temperatures. A major challenge, Hittinger said, comes in getting the yeast to efficiently break down plants to produce the fuel. Hittinger’s research group focuses on identifying yeast candidates and genetically editing them to express the desired characteristics for large-scale fuel production.

If this route for energy production could be utilized to meet society’s greater energy needs, it could be a real game changer. Using these yeasts, liquid fuel production wouldn’t be constrained to oil fields and wouldn’t require the same heavy machinery or refining methods.

Hittinger believes combining the efforts of researchers and industries can make yeast a sustainable method for fuel production. If this challenging task proves to be successful, yeast could one day fuel our cars, boats, and airplanes. Producing fuel from yeast would also allow us to avoid the damages of today’s fossil fuel production. 

“Every bit of reduction and prevention we can do,” Hittinger explained, “is mitigation that we don’t have to do.”