Several labs are working on different ways to turn waste carbon dioxide into engine fuel. 

However, they share a problem.

The usual two-step process transforms the gas into a solid by combining it with another element, such as carbon to form calcium carbonate. After that, the material has to be heated to separate out the carbon dioxide and convert it to carbon monoxide as burnable fuel.

Usually, less than 20 percent of captured carbon makes it all the way through the process to become useful as a fuel or feedstock. In addition to needing a lot of energy, many of the conversion methods result in materials that are caustic, highly flammable, or otherwise hard to handle.

Now researchers from MIT and Harvard University have collaborated to create a process that eliminates the need for heat and shows better than a 90-percent conversion efficiency.

The group devised a process that converts CO₂ into formate, a compound of carbon, hydrogen, oxygen, and sodium. The solid compound can be used in a fuel cell to produce electricity.

Instead of heating, the method first converts the carbon dioxide gas into liquid metal bicarbonate, which is then converted in an electrolyzer to a concentrated powder. Electrolyzers use energy but much less than existing conversion techniques.

The resulting wet material is dried in the sun or in industrial kilns to become the dry powder that, mixed with water, brings fuel cells to life.

The powder can be stored for years, perhaps even decades, without losing its power as fuel.

The lab experiments proving the method at a small scale should find no trouble scaling up to use in homes and, later, in industrial and grid-scale storage, according to the team.

TRENDPOST: An industry has grown up around converting waste—from flue gas to chicken feathers—into useful products.

However, most of those new processes lack the infrastructure to collect the waste and move it to a processor in an economically practical way. 

One solution is to collocate operations that produce waste that is useful as a feedstock for another: build a protein-processing plant near a chicken farm so the feathers can be moved less expensively; put plants to process plastics or carbon gas into fuel in industrial parks, for example.

In “The Rust Belt Goes Green” (1 May 2014), we described one such industrial ecosystem: The Plant, a Chicago food processing site in which waste from an indoor aquaponic vegetable farm becomes raw material for a kombucha brewery. Some of the waste is dumped into an anaerobic digester that turns organic materials into methane, which fuel the building’s turbine generator.

The generator makes electricity to power the vegetable farm’s grow-lights. The generator also creates carbon dioxide, which nourishes the farm’s vegetables. Finally, spent sludge from the methane digester fertilizes the vegetables.

As resources become more scarce, this kind of industrial ecosystem will garner more attention and entrepreneurs will build more of them.