Home Uncategorized New bacteria that can turn sunlight into liquid fuel

New bacteria that can turn sunlight into liquid fuel

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These bacteria can take hydrogen molecules that have been split from
water using the energy of the Sun, and convert them into an
alcohol-based fuel.
Credit: Dominick Reuter/MIT
Chemist David Nocera from the Massachusetts Institute of Technology
(MIT) in late 2011, introduced the world to his ‘artificial leaf’ – a silicon solar
cell device that can produce energy using nothing but sunlight and
water. The device is steeped in water, and when sunlight beams down on
it, it splits the water into hydrogen and oxygen molecules that can be
stored as an energy source. This is just what an actual leaf does,
except Nocera’s cheap little invention can do it 10 times faster.
The
stored energy can then be fed into a fuel cell to produce
electricity. “With a single gallon of water (3.7 litres), Nocera says,
the chip could produce enough electricity to power a house in a
developing country for an entire day,” Mark Brown reported for Wired,
back when it was unveiled. “Provide every house on the planet with an
artificial leaf, and we could satisfy our 14-terrawatt need with just
one gallon of water a day.”
It sounded really promising at the time, but there’s one big problem – “You guys don’t have an infrastructure to use hydrogen,” Nocera told Christina Nunez at National Geographic. “You guys,” as in, the world outside the lab. Which is true – while electric cars
are being built to run on hydrogen gas, petrol stations around the
world aren’t rushing to install new vapour-friendly pumps. They’re
sticking with their good, old-fashioned liquid pumps for now. 
So
the question Nocera asked himself was, ‘Can I invent a device that
converts hydrogen gas into a something other than electricity, say, a
liquid fuel?’
The answer, he found, lies in engineered Ralstonia eutropha
bacteria, which can take hydrogen molecules – either from Nocera’s
artificial leaf, or something similar – and convert them into a form of
liquid fuel. According to the paper, published this week in the Proceedings of the National Academy of Sciences,
the bacteria are able to absorb the hydrogen molecules, split them into
their base protons and electrons, and combine them with carbon dioxide.
The
bacteria have specially engineered metabolic pathways that can then
convert this hydrogen-carbon dioxide blend into an alcohol-based fuel
called isopropanol, which is sort of like ethanol.
Nunez reports at National Geographic
that the idea would be to set up a bacteria ‘farm’ to produce this fuel
in bulk, sort of like an algae farm, but the bacteria will be much
cheaper to maintain because they don’t need a continuous light source or
much hands-on care to survive. 

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The team is only in the beginning
stages of developing something that could feasibly be put on the
market, and their most pressing challenge is to up the efficiency of the
system. “We’re almost at a 1 percent efficiency rate of converting
sunlight into isopropanol,” Nocera says in the press release, which is about the same rate that’s found in nature when a plant uses photosynthesis to convert sunlight into biomass. 
They’re
working on increasing their efficiency to 5 percent. “There have been
2.6 billion years of evolution, and Pam [Silver, from Harvard] and I
working together a year and a half have already achieved the efficiency
of photosynthesis.”

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