The next breakthrough in renewable energy might be poop.
New scientific techniques pioneered at Brigham Young University point to the potential of converting animal and human waste into energy that can be used to replace natural gas from fossil fuels.
Turning excrement into energy isn’t a new idea. Civilizations have used anaerobic digestion for centuries. However, the methods BYU scientists Jaron Hansen and Zach Aanderud have studied for more than a decade represent a significant step forward in making waste a viable energy producer on a larger scale.
The key to their work is a special cocktail of bacteria that thrive in extreme conditions — no oxygen, temperatures north of 170 degrees — and are pros at breaking down waste into smaller molecules. So bacteria that might have spent life digesting a log in a Russian hot spring can now be put to work eating up manure in a giant tank at a dairy farm.
“We are harnessing the power of the small things that you can't see in the world … to really help us solve a couple of big problems,” Aanderud, a professor of microbial ecology, said.
The two daunting challenges he said this breakthrough could help tackle: transitioning away from fossil fuels and disposing of the massive amounts of waste humans and animals produce.
One dairy cow can produce 100 pounds of manure each day, and large dairies can hold more than 10,000 cows at a time. And this process, Hansen said, could turn that waste from an environmental threat to a powerful potential energy source.
“We're talking about generating enough gas to power small communities,” said Hansen, who chairs BYU’s chemistry department. “We're talking hundreds of kilowatts worth of power.”
Historically, he said, anaerobic digestion at a dairy farm may only be able to turn 40% of the cows’ waste into energy. Pretreating with this bacteria bumped that efficiency level to 80% and reduced the amount of leftover waste that had to be sent to farms or landfills.
It’s faster, too. Instead of taking a month to extract energy from waste, it may now take less than a week.
“These bacteria just work,” Hansen said. “As long as you feed them poop, they make methane gas.”
The process captures the methane produced by the digestion, burns it to produce energy and emits carbon dioxide. If the waste sits in a landfill or a farm’s poop lagoon, more of that methane — a gas that’s 25 times more potent than carbon dioxide for trapping heat — would likely end up in the atmosphere, further accelerating climate change.
The process also uses existing infrastructure — natural gas lines into homes that feed furnaces, water heaters and stoves — to replace a widely used fossil fuel with something more renewable that doesn’t require drilling. Even though it may not be a zero-emission solution like solar or wind, he said, it can be a good option to supplement those energy sources at night or on a still day.
As long as Americans are flushing their toilets and buying cheese and ice cream, the energy source will keep replenishing.
“It's renewable but not necessarily green,” Aanderud said. “At the same time, it is dealing with a huge problem of waste that we have in our society.”
Hansen and Aanderude’s work has already found its way into real-world applications on dairy farms in Wisconsin and Indiana.
Larry Buckle, with Trinity Renewables in California, engineered the Wisconsin pilot project using this new bacteria process. He said it reduced digestion time from 20 days to three days while increasing energy production by 50%. And the smaller amount of solid waste that’s left over has been pasteurized by the high temperatures the bacteria work in, so it’s easier to find a place to dispose of it.
He’s now building a larger version of the pilot facility at the same farm that will process 150,000 gallons of manure a day. He doesn't expect it to be the last such project his team engineers.
“There's a lot of dairy manure. You don't have to pay for it,” Buckle said. “Most importantly, they're pretty well self-contained … so that makes things immensely easier.”
While the fecal abundance at a livestock operation may make farms obvious places to start, this digestive process can produce energy from other types of waste, too. The food people throw away. Grass clippings from lawns. And of course, human poop.
Dave Parry, senior fellow at the international engineering company Jacobs, has worked on numerous projects to test this process at municipal wastewater plants from Oregon to Michigan.
With the advancements from BYU’s research, he said, the thousands of plants already set up for traditional anaerobic digestion can unleash this bacteria, save money on disposing waste and produce energy at efficiency rates that were previously unheard of.
“It's definitely a game-changer,” Parry said. “It'll change the municipal anaerobic digestion industry throughout the whole world.”
In the water treatment setting, he said, the process can reduce the amount of leftover waste by one-fourth and increase energy production by one-third. That could be enough to take wastewater plants off the grid and run them entirely on their own poo power.
That’s a big deal for everyone because water treatment facilities are often a municipal government’s biggest energy consumer. The Environmental Protection Agency reported the energy powering these plants adds more than 45 million tons of greenhouse gasses to the atmosphere each year.
And people are beginning to take notice, Parry said. He’s now working with water plants from Denmark to Australia to the Central Valley Water Reclamation Facility in South Salt Lake on future designs.
It’ll take a couple of years before any of them are operating at full capacity. But when the world realizes how much energy is trapped in its crap, watch out.
“When it gets to full scale and someone says, ‘Wow, look at Central Valley, look at Denmark,’” Parry said. “It's going to explode.”
