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[SANET-MG] algae for biodiesel and carbon capture
ISIS Press Release 03/03/06
Green Algae for Carbon Capture & Biodiesel
A sustainable option overlooked? Prolific green algae that capture
carbon dioxide to make biodiesel.
Dr. Mae-Wan Ho
The article, along with others, will form part of ISIS’ 2006 Energy
Report (see advertisement below) to be submitted to UK government’s
A fully referenced version of this article is posted on ISIS members’
website. Details here.
Carbon Capture and Storage mega-project beset with problems
The UK government has invested in a £25 million Carbon Capture and
Storage (CCS) demonstration project led by British oil company BP as a
way of reducing greenhouse gas emissions. This involves capturing carbon
dioxide from the exhausts of power stations and hydrogen or oil and gas
production facilities in a relatively pure form and storing it
geologically underground, in porous layers of rock, depleted or
near-depleted oil and gas fields, deep saline aquifers (porous rock
layers containing salty water deep underground), or in coal seams that
cannot be mined.
UK’s energy sector is responsible for 35 percent of carbon emissions, so
CCS seems an effective way of tackling the problem head on. UK’s sector
of the North Sea has large storage potential, estimated at ~20 000 to
260 000 Mtonne CO2. But it is illegal to dump large quantities of CO2
under the North Sea at the moment. Nevertheless, the Norwegian company
Statoil has been re-injecting CO2 co-produced with natural gas into a
deep aquifer overlying its offshore Sleipner field since 1996, and
nothing seems to have leaked from the 6 mt CO2 stored so far. Geologists
are continuing to monitor the situation.
Another approach already adopted in the North Sea Enhanced Oil Recovery
(EOR) programme is to pump CO2 underground to dissolve in the oil,
making it more mobile and easy to extract. The North Sea Oilfields have
an estimated storage capacity of ~700 Mtonne CO2. UK’s oil operations
are nearing the end of their operation, and EOR could postpone
decommissioning and recover more oil.
However, there are problems in capturing carbon dioxide economically and
without compromising the efficiency of the power plants. The carbon
dioxide captured also has to be transported to the storage sites, and
that could involve thousands of kilometres of pipelines.
Moreover, there are major concerns over the integrity of the geological
storage, the possibility of leakage during storage and transport, and
the potential impacts on the marine ecosystem when CO2 is injected into
the deep ocean.
Global warming is accelerating and energy prices are soaring. We have to
find the right survival strategies, and we have to find them now. Time
and energy resources are both running out; squander them on the wrong
technologies and the consequences will be catastrophic, invest in the
right options and we can mitigate climate change and thrive in a post
fossil fuel world.
This report will help you make the right choices
among nuclear, biofuels, wind, solar, energy from wastes, and more…
Send it to your policy-makers to input to the global energy debate.
Sponsor this report by making a donation that will entitle you to
multiple copies at print price plus p&p. For details please e-mail:
Individual copies are available for pre-order at the ISIS online store
According to the US Department of Energy, CO2 capture is the limiting
factor economically, and is generally estimated to represent 75 percent
of the total cost of CCS.
What no one seems to be aware of is that the humble green algae could
offer a cost-effective and environmentally benign way to capture carbon
dioxide on-site that does not need transport or storage, and at the same
time, provides renewable biodiesel fuel much more effectively and
sustainably than energy crops (“Biofuels for oil addict”, this volume).
Green algae to the rescue
Isaac Berzin, a rocket scientist at Massachusetts Institute of
Technology, is using algae to clean up power-plant exhaust, saving
greenhouse gas emissions and satisfying energy needs.
The idea occurred to him three years ago, although it is not exactly new
(see later). He bolted onto the exhaust stacks of a 20 MW power plant
rows of clear tubes with green algae soup inside. The algae grew
happily, gobbling up 40 percent of the carbon dioxide for
photosynthesis, and as a bonus, 86 percent of the nitrous oxide as well,
resulting in a much cleaner exhaust.
The algae is harvested daily and its oil extracted to make biodiesel for
transport use, leaving a green dry flake that can be further processed
to ethanol, also a transport fuel (but see “Ethanol from cellulose
biomass not sustainable nor environmentally benign”, this series).
GreenFuel, the company set up by Berzin in Cambridge Mass., has already
attracted £11 million in venture capital funding and is conducting a
field trial at 1 000 MW plant owned by a major southwestern power
company. GreenFuel expects two to seven more such demo projects, scaling
up to a full production system by 2009.
One key to success is to select an alga with a high oil density – about
50 percent by weight. Algae are prolific and can produce 15 000 gallons
of biodiesel per acre, compared to just 60 gallons from soybean. Berzin
estimates that a 1 000 MW power plant using his system could produce
more than 40 million gallons of biodiesel and 50 million gallons of
ethanol a year. But that would require a 2 000 acre farm near the power
Greenfuel is not alone in racing to make oil out of algae. Greenshift
Corporation, an incubator company based in Mount Arlington New Jersey,
licensed a CO2-scrubbing screen-like filter developed by David Bayless,
researcher at Ohio University. A prototype is capable of handling 140
cubic metres of flue gas per minute, an amount equivalent to the exhaust
from 50 cars or a 3-megawatt power plant.
The US National Renewable Energy Laboratory (NREL) had a research
project from1978 to1996 on creating renewable transportation fuel with
algae making use of waste CO2 from coal fired power plants. The project,
led by NREL scientist John Sheehan, was funded at $25.05 m over the
20-year period, compared to the total spending under the Biofuels
Program over the same period of $459 m. It resulted in a collection of
300 species of green algae and diatoms, now housed in the University of
Hawaii and still available to researchers. Although some technical and
economic problems remained to be solved, it was estimated that just 15
000 square miles (or 3.8 m ha) of desert (the Sonoran desert in
California and Arizona is more than 8 times that size) could grow enough
algae to replace nearly all of the nation’s current diesel requirements,
and algae use far less water than traditional oilseed crops.
Researchers also suggested using algae to clean up Salton Sea in
Southern California , into which more than 10 000 tons of nitrogen
and phosphate fertilizers are discharged annually. The idea was to use
some 1 000 ha of pond system to grow algae such as Spirulina with the
sea water, harvest the algae biomass and convert that into fuels, while
the residual sludge could be recycled to agriculture for its fertilizer
value. An estimate suggests that such a process could mitigate several
hundred thousand tons of CO2 emissions at below $10/ton CO2 equivalent.
But it is perhaps the algae’s potential for carbon-capture that makes
them most attractive, and it is as yet almost untapped.
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