Making Chemicals from CO2

Ever since carbon dioxide (CO2) was labelled a greenhouse gas and an air "pollutant", much pressure has been put on finding ways to reduce CO2 emissions into the atmosphere. And while the bulk of the emphasis has been on energy alternatives to fossil fuels, a startup called Liquid Light is taking a different approach - using CO2 to make chemicals.

Liquid Light announced recently that it has built a prototype that can make ethylene glycol from carbon dioxide. The company estimates that the production of one ton of the end product would require $125 worth of carbon dioxide, in substitution of $600 worth of oil, natural gas, or other traditional feedstocks. Ideally, the production process would utilize CO2 separated from emissions from industrial sources.

To make ethylene glycol (a widely used industrial chemical used in polyester and plastics), catalysts and electricity are used to initiate the necessary chemical reactions. In the first step, CO2 is converted into a two-carbon oxalate molecule via a catalyst-covered electrode.

Other methods for using carbon dioxide as a feedstock have been successful, but only in rare areas with low energy costs. Carbon Recycling International is the prime example. It's plant takes the waste CO2 and cheap energy from a neighboring geothermal plant and makes methanol, a liquid fuel. While this process provides both effective greenhouse gas reduction and energy recovery, it would not be economically viable or sustainable almost anywhere else.

Liquid Light's prototype cell - Technology Review

However, Liquid Light says their catalyst overcomes much of the economical hurdle. Specifically, the catalyst is low-cost, stable over time, and more effective than previous catalysts used, meaning less electricity is required to fuel the reaction. It also creates less byproducts (such as methane and carbon monoxide) from the reaction, meaning less separation is required. All of this translates into a lower overall cost.

The prospect of utilizing waste carbon dioxide sounds intriguing and very "green", but it can be prone to false assumptions. We must remember that the laws of thermodynamics will ever keep us from gaining a net positive energy benefit from reversing combustion (i.e. making CO2 back into a fuel). In addition, without renewable energy as a power source, even Liquid Light's process will not be carbon neutral, when looking at the emissions from the entire process (from producing the catalyst to generating the electricity). However, there is a place for CO2 as a chemical feedstock if we can economically substitute it for fossil fuels or other (more valuable) substances. Certainly finding beneficial uses for waste products is a good thing, and Liquid Light's technology is another example of a promising attempt to do that.

Sources:

Technoloy Review - A Cheaper Route to Making Chemicals From CO2

The Energy Collective - Making Petrochemicals From CO2