How to Turn Carbon Dioxide Pollution Into Useful Products
Amid new US government subsidies for carbon-capture technologies, a study looks at ways to recycle planet-warming emissions.
Capturing the carbon emissions produced by fossil fuels could play a major role in heading off the worst of climate change — but like the proverbial dog that caught the car, what happens then?
Scientists have been paying more attention to that question as carbon-capture technology tries to find a foothold. Turning the planet-warming byproduct of fossil-fuel combustion into something useful could help improve the economics of that process, Phil De Luna, a materials scientist at the University of Toronto, told Seeker.
Researchers like De Luna are trying to convert largely inert CO2 to hydrocarbon fuels like methane or ethane to store energy — or to industrial chemicals like alcohols and ethylene, a major component of plastics.
“You can think of it as artificial photosynthesis,” De Luna said. “Similar to how a plant takes CO2, water, and sunlight and makes sugar for itself, we’re working on taking CO2, renewable energy, and water and turning that into fuels and feedstocks we can use.”
De Luna and his Toronto colleagues are part of a team competing for the $20 million NRG Cosia Carbon XPrize, which is boosting research into making usable products out of carbon dioxide. Their new study, published March 30 in the research journal Joule, concludes that current technology could convert CO2 to small, energy-dense hydrocarbons using electricity from renewable sources and chemical catalysts in an “economically compelling” fashion.
Most carbon capture systems in operation today either pump that captured gas deep underground, trapping it in rock formations; or into oil wells, using it to boost the well’s output. But using electricity and a catalyst like zinc to separate an oxygen atom from carbon dioxide leaves carbon monoxide, which has a variety of industrial uses.
With current technology, the product with the most potential is ethylene, which can be produced using a copper catalyst that reacts with water.
“It has a huge market and it has a huge value,” DeLuna said. And being able to produce ethylene from CO2 could be a boost to plastic recycling, since carbon released by burning old plastic could be captured and used to produce new plastic, “reusing the carbon atoms you used the first time.”
But other processes used would need to be more cost-effective than current fossil-fuel methods to be economically competitive, De Luna said: “You need to find gaps that are most vulnerable to innovation. That’s the only way that you can drive the scale-up necessary to get to these higher carbon products in the future.”
The Global CCS Institute says 17 large-scale projects are up and running worldwide, 12 of them in the United States and Canada. Those major projects and numerous smaller ones are currently sequestering about 40 million tons of carbon a year — a sizeable amount, but still a fraction of a percent of the world’s output of greenhouse gases.
Jeff Erikson, the institute’s general manager for the Americas, told Seeker the industry “absolutely” sees an opportunity for recycling that CO2 into more useful products.
“What this also is doing is attracting a new audience to the idea of capturing carbon and reusing it,” he said. “For recycling, it attracts venture capitalists and entrepreneurs and NGOs in way that sticking CO2 into the subsurface does not.”
He said several small companies are looking for ways to use captured CO2, and China — which has become the world’s largest emitter as a result of its rapid industrialization — has a strong interest in finding a way to recycle captured carbon. Asian countries are still building coal-fired power plants to meet demand, providing opportunities there — but Western countries have largely stopped building coal plants, leaving a bigger potential market in carbon-intensive industries like steel and concrete manufacturing, Erikson added.
But for recycling to succeed, those projects would have to result in a permanent net reduction of carbon dioxide in the environment.
“Putting carbonation into a soda can and you release it into the environment again doesn’t count as permanent,” he said.
Two coal-burning power plants, one in Texas and another in Canada, are running the technology today, but a third project in Mississippi was a costly failure. And while the Department of Energy says the technology is needed to help meet US goals for reducing emissions, a 2016 report from the agency found “continued improvements in cost and performance” were needed before it could go into wide use.
Congress took a step toward boosting the industry in the recently-passed bill that funds the US government through the remainder of 2018. A provision in that 2,200-page bill gradually jacks up the tax credits companies can claim for captured carbon, from $20 a ton for stored CO2 to $50 and from $10 to $35 for gas used in oil production.
Erikson said that measure is expected to spur new interest in the technology. “It’s still not easy to pull together at CCS project, but this changes the economics on a lot of that,” he said.
That comes on top of nearly $8 billion the US government has spent on carbon capture research since 2009[MS2] . If the technology can succeed, it would greatly reduce the carbon footprint of coal and natural gas-fired power plants, which generate about two-thirds of US electricity.
“These days, with the severity of the situation and how things are looking, this is a technology that kind of brings hope to what we can do and strategies we have to sort of level out that energy playing field and really position us for a sustainable future,” De Luna said.