Tweaking Bacteria, Scientists Turn Sunlight Into Liquid Fuel

National Geographic News ^ | February 9, 2015 | Christina Nunez

[2ndDivisionVet]

Daniel Nocera's artificial leaf splits water using the sun's energy, but the world isn't yet set up to use the hydrogen gas it produces. New research uses bacteria to convert the hydrogen to liquid fuel.

Daniel Nocera pioneered an "artificial leaf" that mimics the real thing, using only the sun and water to produce energy. He's touted the silicon cell as a breakthrough that could allow every home to become its own power station.

His compelling concept, unveiled a few years ago, attracted a lot of publicity but hasn't quite taken off. The leaf—a cheap, wafer-thin device—works well, Nocera says, but there's a key flaw.

"The problem with the artificial leaf," Nocera says, is that "it makes hydrogen. You guys don't have an infrastructure to use hydrogen."

By "you guys," Nocera means the world outside the lab. Although Toyota and others companies are making cars built to run on hydrogen, emitting only water vapor, filling up is a problem: Most gas stations are set up to serve liquid fuel.

Storing the Sun

Enter Nocera's latest creation, a collaboration with biologists at Harvard University and detailed in the Proceedings of the National Academy of Sciences Monday. The researchers created a specially engineered bacteria that can convert hydrogen (from the artificial leaf or another source) into alcohol-based fuel.

The Harvard researchers are aiming to solve a problem known to any electric utility: Capturing energy from the sun has come a long way, but how can it be stored for times when there's no sunlight? Going a step further, how can that stored energy be used for purposes other than electricity?

In natural photosynthesis, biomass is produced when sunlight meets with water and carbon dioxide. Another step is typically required to turn that biomass into fuel—breaking down corn to make ethanol, for example.

Instead, the researchers made a genetically modified bacterium that could bypass the biomass step and go straight to producing liquid fuel. Using the artificial leaf, they split water into oxygen and hydrogen. The special bacterium absorbed the hydrogen, combining it with carbon dioxide to produce isopropanol: an alcohol fuel comparable to ethanol.

The resulting system would look like an algae farm, Nocera says, except that the bacteria wouldn't need the continuous light or maintenance that algae require.

"Shocking" Finding

Nocera says his team also solved a problem that long bedeviled researchers working with bacteria and solar energy: The bacteria die. Keeping them alive requires high-voltage current, making the process far less efficient.

The culprit was known to be a type of molecule called reactive oxygen species, but the surprise lay in where they were coming from. When water split, the reactive oxygen species were coming out of the hydrogen side of the water splitting, not the oxygen side.

"We were shocked," Nocera says. "That confused us for a while." By pinpointing that problem, the Harvard researchers were able to produce fuel much more efficiently.

Despite the streamlined process, Nocera's system has quite a way to go before it's filling gas tanks.

John Turner, a research fellow who works on hydrogen energy at the National Renewable Energy Laboratory, says the paper is "some very excellent science," but cautions that the Harvard researchers "are a long, long way from showing any commercial viability."

Aside from the energy needed to grow the microbes and eventually extract the fuel, Turner says, any system that needs carbon dioxide must get it from the atmosphere to be sustainable. "That," he says, "will be a very energy-intensive process."

Nocera acknowledges that his system needs to become more efficient. To start running it as an industry, he says, "we'd still have to do more science."

Still, Nocera says, the paper contains advances that apply to work other scientists are doing: "There's a lot of neat science in here that people will now be able to build on."

[Cowboy Bob]

I’ve heard that Twerking helps to spread bacteria.

[Pontiac]

John Turner, a research fellow who works on hydrogen energy at the National Renewable Energy Laboratory, says the paper is "some very excellent science," but cautions that the Harvard researchers "are a long, long way from showing any commercial viability."

And when they do show commercial viability it will be very limited.

There simply are not enough watts per square foot at the earth’s surface to make it a replacement of current commercial sources of power.

[Artie]

“There simply are not enough watts per square foot at the earth’s surface to make it a replacement of current commercial sources of power.”

But, there is an unending supply of government grants and federal subsidies to make this “work”

[thackney]

There simply are not enough watts per square foot at the earth’s surface to make it a replacement of current commercial sources of power.

That is not close to being true. Far more power hits the earth via solar energy than we use ourselves in all the other forms. The State of Arizona receives over 100 times the energy in solar power per year than the entire US uses in a year.

The problem is capturing, storing and distributing it. But all the energy we need, a more than a thousand times over, strikes our territory for all our uses.

Arizona = 295,254,200,000 sq m
6 kWH/d/sq m
1,771,525,200 MWH/d
365 d/yr
646,606,698 GWH/yr
3,412 BTU/kWH
2,206,222,054 Billion BTU/yr
2,206 Quads/yr (Quadrillion BTU)

[norwaypinesavage]

This reads like the ham sandwich story: “If I had some bread, I could make a ham sandwich, as long as I could get some ham and mayonnaise, too. Getting some cheese would also help.”

[taxcontrol]

I distinctly noted the lack of cost and/or ROI data. Many things which are doable in the lab are not so doable in the field.

[SunkenCiv]

Chlamydomonas reinhardtii

Google

Chlamydomonas reinhardtii site:freerepublic.com/focus/

Google