Could US oil imports be replaced with a single set of facilities producing biofuels from CO2, salt water and low-cost natural gas? Subsidy free, cropland free, mandate free?
If you happen to be awakening from a four-year nap, or returning from a tour of the outer solar system, you may not have been made aware that US natural gas prices have plummeted, and are expected to remain at half the cost of petroleum, or less, for years to come.
Now, it is common knowledge that cheap natural gas can be used to generate cheap power, or that low-cost compressed natural gas that can power some specially outfitted trucks. 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.
Huh? What happened to biomass? What happened to renewable sugars?
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.”
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’s another class of microorganisms that avoids the use of solar energy and have gained currency as a technology platform – and these are the heterotrophic algae, utilized most famously by Solazyme, but also in the BP-DSM partnership and by Phycal. Like the yeast-based microorganisms developed by Amyris, and the e.coli-based magic bugs developed by LS9, these critters use sugars (renewable or conventional) as a feedstock – even though freed from using photosynthesis directly, they still use it indirectly to produce the underlying sugars they ferment.
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. Accordingly, because they avoid any use of that archaic if foundational system for converting energy to molecules, they are liberated from the inefficiencies or limits imposed by evolution.
ARPA-E’s Electrofuels program is seeking to take advantage of those properties to create processes that are up to 10 times more energy efficient than current biofuel production methods. Back in 2010, they funded 13 projects that will attempt to bring a feasible technology forward to achieve those productivity levels.
Alternatives to Electrofuels at ARPA-E
Now – this isn’t the only program over at ARPA-E that has taken on the photosynthesis problem. There’s the more recent class of technologies funded in the PETRO project.
Technologies for low-cost production of advanced biofuels are limited by the small amount of available energy captured by photosynthesis and the inefficient processes used to convert plant matter to fuel. PETRO aims to create plants that capture more energy from sunlight and convert that energy directly into fuels. ARPA-E seeks to fund technologies that optimize the biochemical processes of energy capture and conversion to develop robust, farm-ready crops that deliver more energy per acre with less processing prior to the pump.
If successful, PETRO will create biofuels for half their current cost, finally making them cost-competitive with fuels from oil. Up to $30 million will be made available for this program area.
Massive scale using natural gas – is there potential?
How powerful a platform? Well, we’ve heard some claims over the years of productivities as high as 100,000 gallons per acre – and they have always failed to realize their promise because of the physical limitations imposed by photosynthesis. But here are a class of magic bugs that could really generate yields in the 20,000+ gallons per acre range, evenproduced via flat panels on a desert floor.
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.
But think of all that natural gas piling up at the Henry Hub in Oklahoma, and you have some idea of the scale and potential of this class of fuels.
With how small a footprint could US energy independence be achieved – to use the example of one country? 80,000 acres – say, the size of a single large ranch? Possible.
An example: The UCLA electrofuels program
UCLA is utilizing renewable electricity to power direct liquid fuel production in genetically engineered Ralstonia eutropha bacteria. UCLA is using renewable electricity to convert carbon dioxide into formic acid, a liquid soluble compound that delivers both carbon and energy to the bacteria. The bacteria are genetically engineered to convert the formic acid into liquid fuel—in this case alcohols such as butanol.
Current limitations of electrofuels technology
Well, right now they are all of them in the lab. But more importantly, at truly massive scale there is going to be a requirement for drop-in fuels, as opposed to alcohols that don’t readily blend at high levels and meet EPA and vehicle specs.
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.
Scale-up of electrofuels technologies
This past February, ARPA-E issued a Request For Information (RFI) focused on accelerating the development of transformative market-ready non-photosynthetic biofuel technologies. Having supported technologies on the lab-scale, ARPA-E is now seeking input from industry, academia, and other interested stakeholders on the steps and challenges necessary to scale-up and apply these and related technologies in a commercial-scale facility. Here was the funding opportunity announcement.
By. Jim Lane
Source: Biofuels Digest