Work led by an Ohio waste-to-energy company to make plastic from biodigester byproducts is among seven projects recently selected for federal grants to develop new ways to use the captured carbon dioxide.

The grants aim to advance the federal government’s goal of net zero greenhouse gas emissions by 2050 to combat ongoing climate change.

Quasar Energy Group, headquartered south of Cleveland in Independence, designs and builds anaerobic digesters, in which bacteria break down manure, food waste or other organic matter. Methane is the main gas produced by the systems and can be used, among other things, to power generators or heat buildings.

But anaerobic digesters also produce carbon dioxide, another greenhouse gas with fewer commercial uses. Today, customers include fertilizer manufacturers, oil and gas companies, and food and beverage manufacturers. But these markets are tiny compared to the amount of CO₂ that scientists say will need to be eliminated from industrial emissions, or even removed from the atmosphere, to address climate change.

There is a limit to the amount of carbon dioxide that can be stored in the ground, and community opposition to pipelines poses another obstacle to the Midwest’s carbon capture plans. Using carbon from products – such as cement or plastics – can be a useful alternative, especially if it replaces other fossil fuels.

On October 9, the U.S. Department of Energy’s Office of Fossil Energy and Carbon Management announced funding for seven projects aimed at commercializing new approaches to incorporating carbon dioxide into products. The selections target hard-to-decarbonize sectors, said Ian Rowe, division director for carbon dioxide conversion in DOE’s Office of Fossil Energy and Carbon Management.

“There won’t be a carbon-free solution to meet these needs in the future, but we should make them from more sustainable forms of carbon,” Rowe said. “And carbon dioxide represents a raw material that you can use.”

How the process works

Ohio is already a leader in plastic production that relies heavily on the fossil fuel industry. Hundreds of companies across the state play a role in manufacturing or the supply chain. And intermediate processing provides immediate supply of natural gas raw materials from the Utica Shale Play.

The Quasar Energy team designed its plastic manufacturing process to work well with biodigesters. Basically, the project will use lipids from algae as a raw material for a type of polyurethane. Liquid effluent from the biodigester could contribute to the growth of algae and provide them with nutrients, such as nitrogen and phosphorus.

Carbon dioxide from the biomanager’s gas would be another ingredient in the process. The project team estimates that the process could reduce carbon dioxide emissions by at least 25%, compared to current plastic manufacturing technology.

The process already works on a lab scale, said Tao Dong, a chemical engineer at the National Renewable Energy Laboratory in Colorado, who also works on the project. Other team members named in the group’s grant application to DOE include Caixia “Ellen” Wan of the University of Missouri, Xumeng Ge of Quasar, and Ashton Zeller, research director at Algix.

Costs are an important factor for the Quasar team’s project or any other product aimed at replacing those made from fossil fuel sources. These costs include expenses related to “cleaning” the gas from the biodigester to separate methane from carbon dioxide. But part of this expense can also be attributed to the separated methane, which has its own energy value, either for on-site use or for sale for use elsewhere.

In other words, using the gas to make plastic and to produce energy contributes to the economics of both uses, rather than simply flaring the gas into the atmosphere.

“Our process can be cost-effective,” said Yebo Li, director of innovation and science at Quasar.

Plastic made from this process also has the advantage of being an isocyanate-free polyurethane, said Mel Kurtz, president of Quasar. Links to the Occupational Safety and Health Administration isocyanates to various health problems, and some are potentially carcinogenic. So a polyurethane plastic that doesn’t contain it should reduce risks for factory workers who would then use the material to make products, such as shoes or other items.

“If (farms) can add another revenue stream, that can improve the profitability” of biodigesters on farms, said Andy Olsen, a senior policy advocate at the Environmental Law & Policy Center, whose work focuses on energy issues related to agriculture and is not part of the project team.

It’s also important to ensure staff are properly trained to properly operate and maintain equipment, Olsen added, noting potential problems with gas leaks. Others wonder if the emissions offsets from certain biodigesters have been exaggerated.

Next steps

The Quasar project team still faces obstacles. Work under this grant will focus on identifying and managing risks so that the technology can be scaled up.

One of the challenges will be maintaining the algae pools over time to provide the lipids needed for the process. Another solution will be to optimize the process of transforming into small chemical elements called monomers, then assembling them into polymers, which constitute plastic. It will also be important to maintain the reduction in greenhouse gas emissions over time.

Other Midwest grant recipients include LanzaTechan Illinois sustainable fuels company, and Washington University in St. Louis, which will develop a low-carbon process to convert carbon dioxide into high-quality carbon nanotubes. These will be tested for use as anodes for lithium-ion batteries.

The big question is whether these and other carbon management projects can scale up quickly enough for the U.S. to reach net zero emissions by 2050, DOE’s Rowe said.

The source of energy for the production process will also make a big difference, Rowe said. Algae can make its own food using carbon dioxide and sunlight. But it takes energy to maintain ponds throughout the year. The equipment used to treat algae and then transform the lipids and carbon dioxide from the biodigesters into polyurethane also requires energy.

“Carbon management strategies go hand in hand with increased deployment of clean, cheap electricity. So a lot of them won’t work without the others,” Rowe said. On the other hand, “if that energy doesn’t come from clean sources, you’ve just produced something that’s worse for the environment than if you’d dug it up and just used fossil carbon.”

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