Editor’s note: This story was updated to correct the name of WatchMyWaste.com.au.
Each year Boulder County amasses about 61,000 tons of organic waste.
According to WatchMyWaste.com.au’s food waste greenhouse gas calculator, waste releases roughly 220,000 kilograms of methane and 105 million kilograms of carbon dioxide.
While a lot of that gas is collected at landfills and combusted to generate electricity, the EPA estimates landfills are still the third-largest source of human-related methane emissions in the United States, accounting for approximately 14% of all human-related methane emissions in 2017. Landfills also account for 1.5% of all carbon emissions in the U.S.
A study conducted by the Institute for Local Self-Reliance, Eco-Cycle and Global Alliance for Incinerator Alternatives, reported significantly decreasing waste disposed in landfills and incinerators will reduce greenhouse gas emissions the equivalent to closing 21% of U.S. coal-fired power plants.
The EPA also states that all landfills eventually leak toxic leachate into the ground that can potentially taint the groundwater.
To help address this problem, the U.S. Department of Energy recently announced $73 million in grants to develop a system for eliminating organic waste. Of that, $5.1 million went to Ken Reardon, a professor at Colorado State University’s Department of Chemical and Biological Engineering, and a team of researchers studying anaerobic digestion.
A series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen, once anaerobic digestion is completed nothing is left behind except for carbon dioxide, methane and some bacteria.
While this process has been understood for decades, it hasn’t been widely adopted in the U.S. as a way to dispose of waste due to the high costs of building a facility large enough to handle the millions of tons of organic waste produced in the U.S. each year, and a lack of some sort of profitable by-product that could off-set those costs.
However, using newly designed bioreactors that inject electrons from solar or wind plants into the anaerobic digestion process, Reardon and his team, including assistant professors of chemical engineering Joshua Chan and Susan DeLong, associate professor of mechanical engineering Jason Quinn, and collaborators at the National Renewable Energy Laboratory, South Dakota School of Mines and Technology, and University of California, Irvine, believe they can convert the leftover methane and carbon dioxide into biofuels.
The process would also capture 100% of the carbon dioxide and methane released and eliminate all of the organic waste.
The first by-product created is isobutanol. An alcohol like ethanol, isobutanol can be blended with gasoline as a fuel, but because it’s a larger molecule is produces more energy per gallon than ethanol. It can also be converted into jet fuel.
The other product is hexanoic acid, which can be converted into other fuel molecules that can be blended with diesel fuel to make it more powerful.
“It’s a double benefit for greenhouse gas emissions,” Reardon said. “For one thing you’re getting rid of something that emits a lot of greenhouse gases if you just leave it be and take no action. At the same time, we’re making a biofuel that is replacing petroleum and again reducing greenhouse gas emissions.”
Though Reardon and his team are confident they can produce these biofuels, the big question as part of Reardon’s five-year study is whether or not they can produce enough biofuels to take this project to scale.
“We don’t know because no one has ever done this,” he said, “but I believe this could be scalable to deal with an entire municipality’s waste stream. There are some anaerobic digestion plants in Europe that are all about that, so we know it can be done in the old way, so I don’t see any reason why we couldn’t also do it using this more advanced process.”
