Biofuels beyond Corn: The Pathway from CO2, Water and Electricity to Liquid Fuels

by Jim Lane (Biofuels Digest) ... There’s been the cellulosic wave, then waste — and alongside there has been steady progress in what are known as the electrofuels. These are fuels made directly from CO2, water and either sunlight or electricity. Generally if a microorganism is involved, there’s sunlight in the picture (not always); inorganic catalysts (generally, metal-based, and expensive) have used electricity to power the conversion.

One, the conversion mechanism. We reported on the slow productivity rates with some of the most promising microorganisms, here. There are the struggles to build an investor-affordable reactor for micro-organisms, which has caused delays for Joule.

With the inorganic catalysts, it’s been selectivity. As Jaramillo (Thomas Jaramillo, an associate professor of chemical engineering at Stanford and of photon science at the SLAC National Accelerator Laboratory) notes, “Copper is one of the few catalysts that can produce ethanol at room temperature,” he said. “You just feed it electricity, water and carbon dioxide, and it makes ethanol. The problem is that it also makes 15 other compounds simultaneously, including lower-value products like methane and carbon monoxide. Separating those products would be an expensive process and require a lot of energy.”

So it’s good news this past week when Stanford University scientists reported on a promising technology to make renewable ethanol from water, carbon dioxide and electricity delivered through a copper catalyst.

We reported last October that researchers from Oak Ridge National Laboratory have come up with a highly-efficient process to make liquid fuels directly from carbon dioxide and water, with a yield of 63 percent. Typically, this type of electrochemical reaction results in a mix of several different products in small amounts. And let’s add this: the process relies on low-cost materials, and operates at room temperature in water — so there’s a distinct hope that the process will scale cost-effectively.

Something nearer-term? Think biogas from dairy operations. We suggested in “Bossie the Climate Warrior” earlier this month that methane emissions can be flared to convert methane to CO2, and herein combined with on-site water to make ethanol. That’s a second value stream for a dairy farmer who, at best, right now is generally looking at burning methane to produce power or compressing it for CNG vehicles. Here’s a higher value use.

It’s not quite the same as CO2, but carbon monoxide is found in abundance, and aggregated, at steel mills , and we reported earlier this year that Stanford scientists found a new, highly efficient way to produce liquid ethanol from carbon monoxide gas.

So, here’s one limitation and concern. It’s not a perpetual energy machine. The process consumes energy in the form of electric power, so why not just use the electricity to power electric vehicles?

The simplest way to see the battle is that electric vehicles have a very efficient motor and a lousy energy storage system. Liquid fuels have much less efficiency in the motor, but very dense energy storage. The longer you wish to travel or the bigger the load you need to haul, the more you like combustion.

That’s why people get very tempted by fuel cells. These power an electric motor, but use on-board hydrogen instead of electric batteries to carry the power.

Nirvana would of course be a fuel cell-like system that converted liquids instead of compressed hydrogen gas into electrons to power a motor. That would be so much lighter than an electric battery and so much faster to refuel — that we’d all put the EV vs biofuels battle behind us, and use both.