by Jim Lane (Biofuels Digest)  …Fewer people know that natural gas is a platform for producing ethanol – either through fermentation or catalytic conversion (typically via methanol) – and drop-in fuels using the methanol-to-gasoline method pioneered years ago by ExxonMobil are another route.

One of the more intriguing uses of natural gas is to use it to generate electric power, and then convert that electricity directly into biofuels.

…Yep, there’s a whole class of processing technologies that can use electricity, water and CO2 to make hydrocarbons and other molecules that can be burned for fuels – or alternatively used in green chemistry to make flavors, fragrances, fibers, solvents, lacquers, thinners, paints, cleaners and a host of other everyday products.

And in doing so, this class of technologies bypasses perhaps the most perplexing barrier to higher yields and cost competitiveness.

Which is to say, photosynthesis itself.

As ARPA-E explains, “Most biofuels are produced from plant material that is created through photosynthesis, a process that converts solar energy into stored chemical energy in plants. However, photosynthesis is an inefficient process, and the energy stored in plant material requires significant processing to produce biofuels.”

About electrofuels

The alternative? Electrofuels. These use microoganisms — typically bacteria — to directly utilize energy from electricity and do not need solar energy to grow or produce biofuels.

…Now, there are magic bugs that synthesize sugars or fuel molecules directly from CO2 and water; Joule Unlimited and Proterro are among those using them. But they utilize solar energy as an energy source – while fully separated from the biomass cycle, they are dependent on photosynthesis.

But electrofuels bypass not only biomass, but photosynthesis altogether.

…They can produce fuels 24/7 – and you can even produce them in three-dimensions to achieve even more efficiencies of acreage. You can stack them towards the sky, or towards the center of the earth, and the per-acre yields can go as high as the costs of stacking permit.

Why of renewed interest now? The availability of low-cost natural gas in the United States is going to radically change the economics of these fuels, should natgas be utilized as an underlying feedstock.

Also, because these fuels are independent of sunlight, wind or biomass requirements, they can be produced at any site that has any meaningful access to water and CO2 (and natural gas fields usually contain CO2, themselves) – and are not limited in scale by the feasibility of aggregating biomass.

Are electrofuels really biofuels at all?

Are they biofuels at all? Well, we think so – because we take the view that any fuels produced using a biological process, via a magic bug, are biofuels. But for those who apply the “must be made from biomass intermediates,” the fuels would not pass that test. Neither would, for example, Joule Unlimited Fuels, or those made by Coskata from natural gas or LanzaTech from blast furnace off-gases.

Not that there is any reason why solar, wind, geothermal biomass could not be used as power sources, to add green attributes or to create feasibility where natgas is less available or affordable. In fact, an electrofuels system can be thought of as a more efficient way to store energy from renewable power generation – given the energy density of liquid fuel compared to current renewable storage systems such as batteries.

…Right now, most electrofuels magic bugs have been engineered to produce higher alcohols – generally isobutanol, although Harvard’s Wyss Institute is investigating octanol. Others are looking at bio-oils that will need further upgrading to drop-in fuels.

A lonely alternative – aimed at drop-in fuels? Ginkgo BioWorks has a project to produce isooctane – now, that’s in the gasoline range (and has a terrific 100 octane rating – in fact, its the baseline gasoline component for “octane ratings” that measure anti-knock properties).

One other limitation? Water. At scale, the systems will likely need to be based on seawater, or at least brackish non-potable water, or even water recovered from fossil wellhead areas. No point in solving the biomass problem to get right back into a freshwater sustainability problem.   READ MORE and MORE and MORE (ARPA-E) and MORE (ARPA-E)