Carbon Neutral
Carbon Neutral means that producing and burning a carbon
based fuel will not increase the carbon dioxide in the atmosphere.
This can only be possible if the amount of carbon released into
the atmosphere is extracted from the atmosphere.
CO2 in the atmosphere is plant food, and that is a good thing, but nature
is very efficient and will often have multiple purposes for a natural
process: CO2 in the atmosphere also helps keep the planet
warm. Too much of a good thing can lead to a bad thing—Global
Warming. Carbon neutral fuels help prevent too much CO2 from
accumulating in the atmosphere.
Burning plant biomass, either directly for heat and electricity generation,
or as biofuels for transportation, will release carbon into the
atmosphere in the form of CO2 emissions, where the carbon can
then be used
again for new plant growth. When biofuels release carbon into
the atmosphere the emissions are considered to be carbon neutral
because the
carbon is continuously
recycled from the atmosphere as new energy
crops are
grown each season to make more biofuels.
When carbon based fuels are burned, oxygen molecules from the air combine
with carbon atoms in the fuel, producing carbon dioxide (CO2) molecules.
When the CO2 molecules enter the atmosphere they quickly disperse.
In other words, CO2
naturally spreads through the atmosphere, equalizing
CO2 concentrations
around the globe, similar to how oxygen released by trees and plants
in remote locations is shared by the entire planet. CO2 does not
form “clouds” of
carbon dioxide in the atmosphere hovering over its place of origin.
CO2 will spread through the air quickly, so it really doesn’t matter
where CO2 is released: Mexico, China, India, Los Angeles, London
or Moscow — it doesn’t matter, CO2 produced anywhere, will
soon be everywhere.
The carbon atoms released during the combustion of biomass or biofuels
will not cause a net increase of carbon in the atmosphere because
growing the crops takes carbon out of the atmosphere. In contrast,
the carbon
released by burning fossil fuels is not part of the natural carbon
cycle—because
the fossil carbon was taken out of the earth and added to the
atmosphere, causing a net increase of atmospheric CO2.
In order for fossil fuel emissions to be carbon neutral, the carbon
released from the fossil fuel combustion must either be prevented
from entering the atmosphere, as with carbon capture and sequestration
(CCS),
or taken back out of the atmosphere (extracted). However, if
the emissions are allowed to enter the atmosphere, it would not
be necessary to extract the carbon out of the atmosphere immediately
after it
is released from a vehicle,
or elsewhere,
because achieving a carbon neutral balance averaged over one
year would be all that is required. The CO2 emissions would need to
be removed from the atmosphere within one year, mimicking nature's
cycle of new biomass growth each season.
And, it would not be necessary to extract the carbon from the same
location where the combustion and emissions occurred, because, as described
above, CO2 released anywhere on the planet is soon everywhere,
therefore, the opposite
is also true: removing CO2 from the atmosphere anywhere on the planet
will soon reduce
CO2 concentrations everywhere.
One ton of pure carbon when burned with pure oxygen will produce
3.67 tons of CO2—one
CO2 molecule weighs about 3.67 times more than a single carbon
atom. This means that dividing the weight
of a given volume of CO2 by 3.67 will give the weight, or amount,
of carbon within the given volume. For example, The
2009 U.S. Greenhouse Gas Inventory Report Executive Summary,
published by the Federal EPA, says the U.S. Transportation sector
releases about 2 billion tons of CO2 into the atmosphere annually:
2 billion tons divided by 3.67 gives 545 million tons of carbon
that must be extracted
from the atmosphere each year in order to maintain a carbon neutral
balance. (The removal of 545 million tons of carbon will reduce
atmospheric CO2 by two billion tons.)
Giving allowance for the increasing volume of carbon neutral biofuels,
let's say a rounded figure of 500 million tons of carbon (equal
to 1.835 billion tons of CO2) would
need to be extracted from the atmosphere over the period of one
year by deliberate human (anthropogenic) design; in other words,
by technology—in
order to make the transportation sector carbon neutral.
500 million tons is a lot of carbon, equal to about half the
amount
of coal mined in the U.S. every year, but less than 1/10th of
annual
global
anthropogenic carbon emissions* which
is about 7 billion tons annually.
(* Carbon
emissions and CO2 emissions are not the same thing. Remember, CO2
weighs 3.67 times more than pure carbon—7 billion tons of
carbon emissions multiplied by 3.67 explains the 25 billion tons
of CO2 emissions often cited by the media. Of course, extracting
carbon from the atmosphere will remove the
entire
CO2 molecule
from the atmosphere. The oxygen within the CO2 molecule will be
separated and released back into the atmosphere. The pure carbon
can then be isolated and buried for centuries;
thereby keeping it out of the atmosphere.)
Fortunately, Nature has provided a biological
Carbon Sponge capable of absorbing an additional 500 million
tons of carbon (equal to 1.835 billion tons of CO2) from the
atmosphere, and more, every year. But it isn’t going to
happen without human effort—we are going to have to “farm” the
carbon out of the atmosphere.
Carbon Farming
When we think of farms, the first image that comes to mind may be
wheat or corn, or perhaps soybeans, potatoes or sugar beets.
But not all farms grow food. A Carbon farm would be dedicated
to growing biomass
for the production of biochar dedicated to the purpose of increasing Soil
Carbon — a form of carbon sequestration that not only removes
carbon from the atmosphere but also makes possible the conversion
of marginal or desert waste land into productive agricultural
land; a gift for future generations.
A Carbon farm would not need to use agricultural land or compete for
scarce water and fertilizer required for growing food crops. A Carbon
farm would do well on marginal land or useless land, requiring only waste
water, or seawater.
Microalgae are prolific carbon sponges, an ideal
crop for a Carbon farm. Microalgae (pond scum) are among the most prolific
photosynthetic
organisms on the planet, capable of doubling biomass every 24
hours if optimal growth conditions are maintained, resulting
in exponential growth.
One acre of shallow water properly maintained can produce 40
tons of microalgae per year (dry weight) having 30-50% carbon
content. Ten tons
of pure carbon in the form of biochar can be produced from
40 dry weight tons of microalgae.
A microalgae Carbon farm would be different from a microalgae biodiesel
farm. There is already a growing international interest in microalgae
to produce a bio-oil that can be used to make biodiesel—a substitute
for petroleum diesel fuel. Production of bio-oil from algae
has yet to fulfill its promise. The algae strains that produce
high concentrations of lipids (oil) do not produce well in open
ponds or open raceways,
because
the open ponds are invaded by local species, which are often
low-lipid algae strains that dominate the weaker high-lipid
algae; causing poor lipid production. High production
rates of algae oil are confined to closed systems, which are
very expensive.
Carbon farms would not be concerned with the oil content of the biomass.
Cheap prolific pond scum, low in lipids and low in proteins
will do just fine. A Carbon farm would only be interested in the carbon
locked within
the biomass molecules. It is the photosynthesis that matters;
and pond scum—local species low-lipid algae—are
just what is needed, and happen to be the least expensive biomass to
produce,
in fact, it is very expensive to try to stop an algal bloom.
In June of 2008, a giant algal bloom covering 5000 square miles of Chinese
coastal
waters threatened the Summer Olympic Sailing competition. The
official Chinese news agency, Xinhua, reported that the algae bloom covered
a
third of the coastal waters designated for the Olympic races.
It required 1,000 boats and 20,000 people scooping algae out of the Yellow
Sea to
keep the Olympic Games open.
Carbon Harvesting
Biochar can be produced through a process called pyrolysis, which is
also used to make charcoal. Any biomass can be prepared for
pyrolysis, and microalgae would require special preparation.
After removal from
the pond, the algae would be air dried or put through a centrifuge
designed to reduce the moisture, and then the dry bulk biomass
would be sent
through a machine to pelletize the
biomass before “cooking” the
pellets at 500-800 degrees F. without oxygen. The hydrogen
and synthesis gas expelled from the cooking chamber are then
burned, externally, to provide heat energy for the process, with plenty
of gas left over to produce electricity or methanol for resale
(in addition
to the
biochar produced inside the cooking chamber).
A one acre pond can produce 40 tons of algal biomass per year, which
can yield a carbon “harvest” of ten tons. The extraction
of 500 million tons of carbon per year from the atmosphere
would require 50 million acres of algae ponds: 500 million
tons divided by 10 tons of biochar
per acre, per year = 50 million acres.
Fifty million acres of algae ponds could make all U.S. transportation — cars,
trucks, airplanes, etc. — carbon neutral while still using fossil
fuels. After the carbon is extracted from the atmosphere
via photosynthesis and reduced to biochar, it must then be
buried in the earth in the
form of Soil Carbon in order to keep the
carbon out of the atmosphere.
The above example shows the potential of algae biochar, but algae is
only one possibility for the commercial production of biochar;
many other sources of biomass are available for producing biochar,
including agricultural waste, as well as forest residue left-behind
by
the lumber industry after clearing or after forest
pruning to prevent fires. Public landfills are another resource;
the enormous amount of yard clippings and other organic material
sent to
landfills could be “harvested” for carbon, rather than
allowed to decay and emit methane into the atmosphere.
Duckweed is another fast-growing aquatic plant currently being researched
for its biomass potential. Research has demonstrated the potential
of duckweed for bioremediation and environmental carbon capture.
The US Department of Energy (DOE) has announced that the Joint
Genome Institute, through DOE's national laboratories, will
support the genomic sequencing of duckweed as one of its priority
projects
directed toward new biomass and bioenergy programs.
Switchgrass is not an aquatic plant, but it would be a good candidate
for a Carbon crop; it will grow on marginal lands with little
fertilizer and is capable of high biomass yields per acre.
A carbon farm could
specialize in switchgrass biomass, and in a few years, when
cellulosic ethanol technology matures, the farm could switch
from carbon production
to ethanol production, or a combination of both. Designating
switchgrass as a carbon crop would
encourage farmers to begin large scale switchgrass farming
on marginal lands, and not wait for cellulosic ethanol technology
to be proven.
Continue reading on next page ——> Soil Carbon
Natural CO2 <—— Back
to Previous Page
Additional Recommended reading:
Carbon Neutral SNG — If biomass
is gasified with coal, it is possible to make a carbon
neutral synthetic or substitute natural gas
(SNG) from the synthesis gas produced by the gasification process;
but only if carbon capture and sequestration (CSS) of the process
CO2 emissions is performed on site, as part of the SNG
production process.
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