CO2 Conversion: Turning Waste Into Value

The world needs more energy. As the population continues to grow and the quality of life improves in developing economies, energy will be necessary to power this growth. Unfortunately, the cheapest and most economical forms of energy also happen to be the dirtiest. Fossil fuel-based power sources like coal, while relatively cheap to produce electricity, provide a high cost in CO₂ emissions and consequently add towards escalating climate change.

Renewable energy technologies such as solar and wind have the potential to usher the world into a post-emission era. Unfortunately, the sun does not shine at night, and sometimes the winds are calm. The biggest challenge with renewable energy is long-term seasonal storage. Batteries offer a reasonable solution for short-term small-scale storage for phones and even cars. But society’s needs reach farther than that, such as heating homes in the winter time or fueling airliners across the ocean.

The conversion of carbon dioxide into fuels and feedstocks using renewable energy offers a solution to long-term renewable energy storage. Photosynthesis takes water, CO₂, and sunlight and converts those inputs into sugar to fuel plants. CO₂ conversion via electrocatalysis seeks to take water, CO₂, and renewable electricity (solar, wind, hydro) and convert CO₂ into fuels that humans can use.

In, What Should We Make with CO₂ and How Can We Make It?, a paper recently published in Joule, researchers from the University of Toronto and the National Renewable Energy Laboratory (NREL) analyzed the current state of CO₂ conversion technologies and which products would make the most economically viable targets for the future.

Using electricity and a specially-tailored catalyst, the material responsible for converting CO₂, one can make a variety of products – ethylene for plastics, methane for home heating, carbon monoxide for synthetic gas, or ethanol for drinking alcohol, to name a few.

The analysis found that short-chain molecules were more economically viable. In other words, shorter, more simple molecules provided the most bang for the buck when the value of the molecule was normalized by the energy input to make it. In fact, assuming optimistic figures of 60% energy conversion efficiency and cheap renewable electricity at 2 cents/kWh, many CO₂ conversion products are cost-competitive with traditional fossil-fuel production. This suggests that the renewable conversion of CO₂ into fuels and feedstocks may displace the production of many common petrochemicals and fuels. This has the potential to completely disrupt the oil and gas industry, which has remained relatively technologically stagnant for decades.

So how close are we to this technology hitting the market? The researchers from the University of Toronto are betting soon enough. They spent the last year competing in the Carbon XPrize, scaling up their discoveries from the lab bench, at milligrams per hour production, to a pilot plant scale, at kilograms per day. The Carbon XPrize is a $20M international competition funded by COSIA and NRG to capture and convert the most CO₂ into a value-added product.

Team CERT, led by Prof. Ted Sargent, was recently announced in April as a finalist, one of only 10 globally. They are now working to build their CO₂ conversion machine onto a natural-gas burning power plant in Alberta and will need to demonstrate 150 days of operation by end of 2019 with conversion rates of tons per day, an order of magnitude increase from today.

These findings are described in the article entitled What Should We Make with CO₂ and How Can We Make It?, recently published in the journal Joule. This work was conducted by Oleksandr Bushuyev, Phil De Luna, Cao Thang Dinh, Shana Kelley, and Ted Sargent from the University of Toronto in Toronto, ON, Canada and Ling Tao, Genevieve Saur, Jao van de Lagemaat from the National Renewable Energy Laboratory in Golden, CO, USA.