Indiscriminate, casual mingling with a number of partners is generally frowned upon these days.
But a certain type of promiscuity could hold the key to solving global warming. It could also help accelerate development of carbon-neutral biofuels.
ClimateWire recently reported that scientists have engineered a bacterium that can turn carbon dioxide (CO2) into fuel in a single, enzyme-catalyzed metabolic step.
Summarizing a paper published on August 22, 2016, in the journal Proceedings of the National Academy of Sciences, ClimateWire noted: “The process draws on sunlight to produce methane and hydrogen inside the bacterium Rhodopseudomonas palustris, in essence reversing combustion.”
CO2 is, of course, vital to life on Earth.
It’s also a significant greenhouse gas. The rapid increase in its atmospheric concentration since the dawn of the Industrial Revolution is widely associated with global warming.
We’re in the process of figuring out how to deal with global warming, from political, policy, and scientific perspectives.
One such approach includes biofuels — or fuels made through biological processes such as anaerobic digestion and agriculture rather than through geological processes that convert prehistoric biological matter into fossil fuels.
The use of liquid biofuels has grown in response to the U.S. Renewable Fuel Standard (RFS), established as part of the Energy Policy Act of 2005. It was then and expanded and extended in the Energy Independence and Security Act of 2007.
Such policies are founded on the belief that biofuels are inherently carbon neutral.
But according to a recent study from the University of Michigan Energy Institute (UMEI), the data do not support a conclusion that corn ethanol and other biodiesel fuels are actually carbon neutral.
Total U.S. biofuel use rose from 0.37 exajoules (EJ) in 2005 to 1.34 EJ in 2013. But the UMEI found that “additional carbon uptake on cropland was enough to offset only 37% of the biofuel-related biogenic CO2 emissions.”
If one accounts for the fossil fuel inputs that go into growing corn and other feedstock for liquid biofuels, “the conclusion is that U.S. biofuel use to date is associated with a net increase rather than a net decrease in CO2 emissions.”
But we may be on the verge of going well beyond King Corn and the “ethanol pledge.”
Removing what the overwhelming scientific consensus considers excess CO2 from the atmosphere and turning it into fuels that don’t release more CO2 is a classic “two birds, one stone” solution.
The “madam” in our story is Professor Caroline Harwood of the University of Washington, whose work in microbiology has focused on an enzyme called nitrogenase.
Harwood is talking about “carbon fixation” — a way of producing renewable biofuels via photosynthesis.
“It’s been sort of recently appreciated that this enzyme is kind of promiscuous,” Harwood told ClimateWire, “and can do other reactions, as well, only not as efficiently.”
Scientists have long known about a process called “nitrogen fixation” — the conversion of atmospheric nitrogen into organic compounds.
Nitrogenase reduces nitrogen to ammonia, using natural energy provided by adenosine triphosphate (ATP).
What Harwood and her co-authors have accomplished in their experimental brothel is describe a “nitrogenase variant” that converts CO2 into to methane, the most basic component of natural gas.
In the first step, researchers isolated and changed nitrogenase to use CO2 to produce methane.
That’s cute in the confines of a research laboratory. But it was a tedious pain in the rear to produce the modified enzyme on a small scale in test tubes. And it’s no way to demonstrate a way to produce biofuels on an industrial scale.
So Harwood et al. modified their variant.
And their engineered strain of the photosynthetic bacterium Rhodopseudomonas palustris “manufactured” nitrogenase at maximum capacity.
R. palustris uses natural sunlight to produce ATP, so natural sunlight also helped power nitrogenase in the variant.
Light-driven carbon dioxide reduction to methane by nitrogenase in a photosynthetic bacterium is just a starting point, but it’s nevertheless a critical one.
Professor Harwood’s engineered nitrogenase in R. palustris makes methane out of carbon dioxide in one relatively simple step.
It happens in a living organism at normal temperature and pressure conditions, so there’s no additional energy required to produce a biofuel.
The next step is to improve the efficiency of the process, so the modified nitrogenase reduces carbon dioxide to methane, as well as it makes ammonia from nitrogen.
Harwood’s nitrogenase gets around — it hooks up with multiple partners and sucks them dry. And it does so in a way that’s not just harmless, but actually may be beneficial to society.
And it leaves us satisfied with honest-to-goodness carbon-neutral biofuels.
It makes a virtue of the ancient profession.
Let’s get it on, indeed.
This Week In…
In the late 1990s, Americans started referring to tract-built luxury homes popping up in the suburbs as McMansions, a biting portmanteau implying that the structures were mass-produced and ugly. There was also the implied snark that their denizens, however wealthy, lacked the sophistication to tell filet mignon from a Big Mac.
Lately, these homes have been the subject of fresh scorn, thanks to an anonymously authored blog that breaks down the genre’s design flaws in excruciating detail. Posts lambasted builders for erecting garages bigger than the homes they’re attached to, dropping giant houses on tiny lots, plus shoddy construction and a mishmash of contrasting styles. (Gothic Tudor, anyone?)
That nevertheless raised the question: How well have these homes kept their value? Not well, compared with the rest of the U.S. housing market.
Editorial Director, Wall Street Daily
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