Published on April 16th, 2014 | by Tina Casey0
Electrochemical Ethanol: No Plants Were Harmed In The Making Of This Fuel
The biofuel industry has been hot on the trail of second-generation concoctions that eschew corn in favor of non-food biomass, but a third wave of innovation is already brewing on the horizon. That would be the conversion of waste gases to liquid fuel while leaving plants entirely out of the equation, and Stanford University is the latest to hop on this promising bandwagon.
The advantages are obvious in terms of carbon capture: in addition to doing an end-run around competition for land and water resources, and eliminating energy consumption related to biomass cultivation, harvesting, and processing, the waste gas approach captures and recycles carbon that would otherwise enter the atmosphere.
Waste Gas To Ethanol With a Copper Twist
We’ve already been following the New Zealand company LanzaTech, which uses a biological process based on microbial fermentation to produce ethanol and other chemicals from industrial waste gas, but the Stanford gas-to-ethanol approach is a whole different ball of wax.
Rather than going the microbial route, the Stanford team came up with an electrochemical pathway to covert carbon monoxide to liquid ethanol.
As described by study co-author Matthew Kanan, the process is based on a new copper catalyst.
The difference between the new catalyst and a conventional copper catalyst is structural. In a conventional copper electrode, nanoparticles “just sit on top of each other.” The new electrode is made from copper oxide, which forms a continuous network of nanocrystals as it is processed into metallic copper.
The gas-to-ethanol conversion takes place in an electrochemical cell, which typically would be used to reduce water to hydrogen. The challenge for the team was to find a cathode that would skip that step in favor of reducing CO to ethanol.
That’s where the new copper catalyst came in. Copper is one of the the few materials known to reduce CO, but conventional copper catalysts are too inefficient.
When the team tried the new copper catalyst, the difference was significant. Kanan runs it down for you (break added):
The oxide-derived copper produced ethanol and acetate with 57 percent faradaic efficiency. That means 57 percent of the electric current went into producing these two compounds from carbon monoxide.
We’re excited because this represents a more than 10-fold increase in efficiency over conventional copper catalysts.
Converting Gas To Fuel With Renewable Energy
The catch is that the process requires energy input.
That’s the same catch that trips up hydrogen production, but as with hydrogen, there is good potential for powering the process with renewable energy.
Since the Stanford process can be conducted at room temperature, energy input is relatively minimal, which advances the prospects for scaling up a process based on solar energy or other renewable sources.
The Race Is On For Gas To Fuel, And Plastics
Kanan also envisions a fourth wave of fuel innovation, which would be to convert atmospheric CO2 to CO in a closed-loop process that continuously recycles carbon (for more Stanford carbon-neutral climate solutions check out a summary in our sister site PlanetSave).
Just like the name says, NewCO2Fuels has come up with a process that converts CO2 to CO and oxygen, which are then processed into fuels.
At the time of our visit, the company had just finished Stage 1 testing, and this March it has moved on to the initial phases of Stage 2. So far the results are promising with a fourfold efficiency increase over Stage 1.
The NewLight process has already caught the eye of Virgin Mobile, which according to a report in USA Today has teamed with the company to make cell phone cases.
Virgin has its eye on LanzaTech, too, in the form of a Virgin Atlantic partnership for making jet fuel from waste gas.
To ice the cake, LanzaTech recently won a $4 million ARPA-E grant to modify its process into transportable bioreactors that could be used at remote industrial sites.
Doubling Down On Fossil Gas
With all this activity going on over carbon capture and recycling, eventually some of the big conventional energy companies could start dipping a toe into this sector, but that doesn’t seem likely.
Exxon, for one, has been gobbling down shale gas assets hand over fist, likely with an eye toward expanding its fossil gas-to-plastics business.
The company just plunked down big bucks for a major expansion of its Baytown, Texas chemical facility to convert fossil gas to polyethylene.
Does Exxon know something we don’t?
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