Pretty Soon, Your Car Might Run On Poop

We might run out of oil, but we’ll never run out of poop.

Pretty Soon, Your Car Might Run On Poop
Source Photo: mcdomx/Getty Images

The world has a poop problem. In the U.S., the challenge is biggest on farms: livestock produces more than a billion tons of solid waste a year, or roughly 87,000 pounds of shit a second. That’s more than 130 times greater than the amount of human waste that goes into sewers. Farm waste—especially on large industrial feedlots—often ends up polluting nearby drinking water and contributes to a significant chunk of greenhouse gas emissions.


Researchers at the University of California are working on turning piles of poo into something useful—fuel that can run in ordinary cars instead of gas, and fertilizer that can replace the energy-intensive fertilizers that are usually used on farms.

“If you take a lot of cow manure, there’s not an efficient way to handle it quickly for farmers, and the result of that is that a lot of it sits around and aerobically composts,” says UCLA grad and Fulbright scholar David Wernick, who spent his time as a PhD student tweaking a process that can convert waste. As manure sits in giant piles on feedlots, it emits methane and nitrous oxide, both significantly more potent as greenhouse gases than carbon dioxide.

In the lab, the researchers genetically engineered a type of bacteria that can break down the protein in manure (or in human waste, or other waste, such as leftover yeast used in making wine or beer). Then the bacteria converts it into fuel and recycled fertilizer.

Unlike older types of biofuel—like ethanol, which is usually made from corn—the new fuel works in existing cars. “They burn like regular gasoline,” Wernick says. “You can actually drop them straight into the car that you have now, and it’ll burn just fine. With ethanol, that’s not the case, it’ll damage your system in your car.”

Biofuels like ethanol have other problems, such as the fact that it takes energy to grow crops and land that could otherwise be used to grow food. Manure and sewage already exist, in huge quantities, without requiring any extra steps for production.

When the poop-based fuel is burned in a car or truck, it creates carbon dioxide—but because that carbon dioxide originally existed in the form of plants fed to livestock, it’s part of a closed carbon cycle. Fossil fuels, on the other hand, dug up from underground, add new carbon to the atmosphere.

Stephen Rees via Shutterstock

Others are also working on turning poop into fuel, such as Bristol, England, which now runs a bus route on methane made from sewage sludge. But the new process the University of California is developing has some advantages—it consolidates manufacturing into fewer steps and automatically creates fertilizer in the process.

Normally, turning waste into methane creates a byproduct called dihydrogen, which can only be turned into fertilizer by using a large amount of energy. It’s the same process that’s used to manufacture ordinary fertilizer.

“It’s done through this gigantic process called the Haber-Bosch process,” says Wernick. “It’s been around for 100 years, and basically it makes all of the fertilizer that grows the food we eat. The world’s population would be something like half of what it is now if we didn’t have the Haber-Bosch process, just because there wouldn’t be enough food. But it consumes a ton of energy to run. It uses something like 2% of the world’s energy every year to run this process.”

The new poop-conversion system that the researchers are working on creates ammonia instead, which can be directly used as a fertilizer.

The next step will be making the whole process efficient enough to compete with gas. Right now, it’s too expensive. “The purpose is to solve the waste problem rather than providing a major energy source,” says James Liao, a biochemistry professor at UCLA who leads the lab where Wernick worked. “In some areas of the world, animal waste can provide some energy, if no alternatives are available. But with current oil prices, it is too costly for conversion to biofuels.”

“Essentially the yields we get out of our current strains are just not quite high enough,” says Wernick. “We don’t get quite enough fuel out of manure at the moment. There’s a lot more work that needs to be done to adjust the strains genetically as well as playing with the process to make this work.”


Eventually, however, it’s conceivable that your car could be running on poop instead of oil.

About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley.