One of the tricky things about tech investing in general and clean tech in particular is the ever-present risk of something new turning your current hot stock into yesterday’s news. For bio-fuel fans, here’s an example from this week’s New Scientist Magazine:
CO2 in the air could be green fuel feedstock
Carbon dioxide could soon be ready for a PR makeover. With a bit of clever chemistry, the gas could become a feedstock for alternative fuels or find a role in cooling freezers rather than warming the atmosphere.
Carbon capture and storage schemes propose to snatch CO2 from industrial chimneys and bury it in ocean basins or geological formations. But having gone to the trouble of capturing the gas, squirrelling it away underground is a wasted opportunity, says Dermot O’Hare at the University of Oxford. He thinks converting CO2 into methanol for use as fuel is a smarter move.
But that’s easier said than done. “One of the difficulties chemists have is doing anything with CO2,” O’Hare says. The trouble is that the molecule is so stable, it’s hard to find chemicals reactive enough to target CO2 but specific enough to ignore other components of the atmosphere such as carbon monoxide and oxygen.
Now O’Hare and Andrew Ashley, also at Oxford, have demonstrated how to do it at the relatively low temperature of 160 °C and at standard pressure. All it takes is a bit of frustration.
A very reactive situation
The technique is based on molecules called Lewis bases, which carry a lone pair of electrons and can bond with so-called Lewis acids to form a molecule called an adduct. In 2008 Doug Stephan at the University of Toronto, Canada, modified Lewis bases and Lewis acids to make them too big to get close enough to form the adduct. “The molecules can’t react – they’re frustrated,” says O’Hare. “And that creates a very reactive situation.”The frustrated Lewis pair are so reactive that when hydrogen gas is added to the mix, the molecules tear apart the hydrogen molecules and bond with the hydrogen ions. The reaction eases the frustration but still leaves two highly reactive molecules. O’Hare and Ashley reasoned that they would be reactive enough to bond with CO2.
They have now achieved this goal. Their frustrated pair consisted of the Lewis base tetramethylpiperidine or TMP and the Lewis acid tris(pentafluorophenyl)borane. When they added hydrogen gas, the acid and hydrogen ion formed a boron-hydrogen bond which can then be used to shatter a stable CO2 molecule, which further reacts with hydrogen to form methanol and water.
Complex alternative
Another proposed system could provide a way to use CO2 without the need for hydrogen. Raja Angamuthu and Elisabeth Bouwman at Leiden University in the Netherlands and their team have just shown how a copper-based chemical called a copper complex can help turn CO2 into something new.The team’s yellow-coloured copper complex turns greenish-blue as it snatches CO2 molecules from air at room temperature and normal pressure. Angamuthu and Bouwman used CO2 labelled with a heavy carbon isotope to confirm that the copper complex reacts with CO2 rather than oxygen in the air, which demonstrates the process is “quite selective for CO2″, says Bouwman.
The team then added a lithium salt to the copper complex solution, causing insoluble lithium oxalate to precipitate. Using electrolysis they can reduce the copper to recreate the copper complex to react with more CO2.
O’Hare finds Angamuthu and Bouwman’s work interesting. “What caught my eye is the reactivity to CO2 in the presence of oxygen,” he says, which means the reaction could work in the Earth’s atmosphere. But while recycling the copper is “neat”, he says the end product – an insoluble salt – is not as useful as making a liquid fuel like methanol.
But the lithium oxalate is far from useless, says Bouwmann. “It can be reduced to ethylene glycol, used, for example, as coolant in freezers,” she says. The oxalate can also be oxidised into oxalic acid for use in household cleaning products.
Some thoughts:
• Sequestering or otherwise scrubbing CO2 out of power plant smoke stacks was always a silly idea, because, as the article notes, it’s expensive and ends up wasting a potentially valuable substance.
• If this or something similar turns out to work, will it, in effect, make current coal burning power plants “clean”? And will this in turn eliminate the rationale for biofuels by making electric cars the more simplest alternative to imported oil?
• Turning CO2 into fuel is a long way from commercialization, so it’s premature to be making cost comparisons between methanol produced this way and other kinds of biofuels now in development. But the profusion of similar breakthroughs has to make the people putting up tens or hundreds of millions of dollars for next-gen biofuel plants a bit nervous.
{ 2 comments… read them below or add one }
I dont see why this threatens biofuels at all!!!!!
This strategy requires a carbon gas as waste but the author neglects to mention how much organic carbon waste is produced daily from the manufacturing process, services process, consumer retail and of course SEWAGE!!!!
This is a death blow to ethanol and biodiesel from food stock (corn and soy) and a death blow to cellulosic ethanol but what we are rapidly finding is that we have limited supplies of metals and rare earth elements that need to be recycled, we need to get legal and illegal drugs out of our water supply, pollutants out of our rivers and find productive use for waste.
Chemical processes called Thymergy which turn carbon based plant material into various forms of biodegradable plastics and foams instead of from oil is yet another new form of chemistry.
I can see a parallel path for gaseous carbon based waste, organic carbon based waste, recycling of metals all competing and surpassing nuclear, coal, oil, natural gas, wind and solar. The future does not belong to a single source but a multitude of sources all being fed into a grid of electricity shared with a backup fuel source.
Every time I see one of these ideas for turning CO2 into a useful product or fuel, I am hopeful that something promising has been found. Unfortunately, as I read about the processes, I inevitably find one of two things:
1) If the processes purports to make a “useful product”, the actual market for that product is a miniscule fraction of a percent of the CO2 currently being emitted.
2) If the process claims to make a fuel, it requires the addition of electric energy or, as in this case, “added hydrogen gas”. Well, duh. If you have electricity or hydrogen gas, you would not bother to use it to make a fuel from CO2; you would just use the electric energy or the hydrogen fuel.
The bottom line is, you cannot violate the law of “conservation of energy”. Biofuels work because they use solar energy to convert CO2 to biomass. Somewhere in all of these processes there has to be a source of energy.