The road from Petri dish to fuel pump starts here. Berkeley Lab’s Jana Mueller is part of a team of scientists working to take a common soil bacterium and use it to create an efficient way to produce diesel and jet fuel. Photo: Lawrence Berkeley National Laboratory
Is there a new path to biofuels hiding in a handful
of dirt? Lawrence Berkeley National Laboratory (Berkeley Lab) biologist Steve
Singer leads a group that wants to find out. They’re exploring whether a common
soil bacterium can be engineered to produce liquid transportation fuels much
more efficiently than the ways in which advanced biofuels are made today.
The scientists are working with a bacterium called Ralstonia
eutropha. It naturally uses hydrogen as an energy source to convert carbon
dioxide into various organic compounds.
The group hopes to capitalize on the bacteria’s
capabilities and tweak it to produce advanced biofuels that are drop-in
replacements for diesel and jet fuel. The process would be powered only by
hydrogen and electricity from renewable sources such as solar or wind.
The goal is a biofuel—or electrofuel, as this new
approach is called—that doesn’t require photosynthesis.
Why is this important? Most methods used to produce
advanced biofuels, such as from biomass and algae, rely on photosynthesis. But
it turns out that photosynthesis isn’t very efficient when it comes to making
biofuel. Energy is lost as photons from the sun are converted to stored
chemical energy in a plant, which is then converted to a fuel.
“We’re after a more direct way,” says Singer, who
holds appointments with Berkeley Lab’s Earth Sciences Division and with the Joint
BioEnergy Institute (JBEI), a multi-institutional partnership led by Berkeley
“We want to bypass photosynthesis by using a
microbe that uses hydrogen and electricity to convert carbon dioxide into a
fuel,” he adds.
Widespread use of electrofuels would also reduce
demands for land, water, and fertilizer that are traditionally required to
Berkeley Lab’s $3.4 million electrofuel project was
funded in 2010 by DOE’s Advanced Research Projects Agency-Energy (ARPA-E)
program, which focuses on “high risk, high payoff concepts—technologies
promising genuine transformation in the ways we generate, store, and utilize
That pretty much describes electrofuels. ARPA-E
estimates the technology has the potential to be ten times more efficient than
current biofuel production methods. But electrofuels are currently confined to
laboratory-scale tests. A lot of obstacles must be overcome before you’ll see it at
Fortunately, research is underway. The Berkeley Lab
project is one of thirteen electrofuel projects sponsored by ARPA-E. And
earlier this year, ARPA-E issued a request for information focused on the
commercialization of the technology.
Singer’s group includes scientists from
Virginia-based Logos Technologies and the University
of California at Berkeley. The project’s co-principal
investigators are Harry Beller, Swapnil Chhabra, and Nathan Hillson, who are
also with Berkeley Lab and JBEI; Chris Chang, a UC Berkeley chemist and a
faculty scientist with Berkeley Lab’s Chemical Sciences Division; and Dan
MacEachran of Logos Technologies.
The scientists chose to work with R. eutropha
because the bacterium is well understood and it’s already used industrially to
They’re creating engineered strains of the bacterium
at JBEI, all aimed at improving its ability to produce hydrocarbons. This work
involves re-routing metabolic pathways in the bacteria. It also involves adding
pathways from other microorganisms, such as a pathway engineered in Escherichia
coli to produce medium-chain methyl ketones, which are naturally occurring
compounds that have cetane numbers similar to those of typical diesel fuel.
The group is also pursuing two parallel paths to
further boost production.
In the first approach, Logos Technologies is
developing a 2-L bioelectrochemical reactor, which is a conventional
fermentation vessel fitted with electrodes. The vessel starts with a mixture of
bacteria, carbon dioxide, and water. Electricity splits the water into oxygen
and hydrogen. The bacteria then use energy from the hydrogen to wrest carbon
from carbon dioxide and convert it to hydrocarbons, which migrate to the
water’s surface. The scientists hope to skim the first batch of biofuel from
the bioreactor in about one year.
In the second approach, the scientists want to
transform the bacteria into self-reliant, biofuel-making machines. With help
from Chris Chang, they’re developing ways to tether electrocatalysts to the
bacteria’s surface. These catalysts use electricity to generate hydrogen in the
presence of water.
The idea is to give the bacteria the ability to
produce much of their own energy source. If the approach works, the only
ingredients the bacteria will need to produce biofuel would be carbon dioxide,
electricity, and water.
The scientists are now developing ways to attach
these catalysts to electrodes and to the surface of the bacteria.
“We’re at the proof-of-principle stage in many ways
with this research, but the concept has a lot of potential, so we’re eager to
see where we can take this,” says Singer.