 |
Biochar is charcoal type created by the pyrolysis of
biomass.
It differs from ordinary charcoal only in the sense
that its primary use is not for fuel, but for biosequestration
or atmospheric carbon capture and storage.
As much as 12 percent of the world's human-caused greenhouse
gas emissions could be sustainably offset by producing
biochar.
|
That's more than could be offset if the same plants and
materials were burned to generate energy, concludes a recent
study published in the journal Nature Communications.
Biochar could sequester carbon in the soil for hundreds to
thousands of years.
Biochar is a high carbon, fine grained residue which, today,
is produced through modern pyrolysis processes. Pyrolysis
is the direct thermal decomposition of biomass in the absence
of oxygen to obtain an array of solid (biochar), liquid (bio-oil)
and gas (syngas) products.
For their study - 'Sustainable biochar to mitigate global
climate change' - the researchers looked to the world's
sources of biomass that are not already being used by humans
as food. For example, they considered the world's supply of
corn leaves and stalks, rice husks, livestock manure and yard
trimmings - to name a few. The researchers then calculated
the carbon content of that biomass and how much of each source
could be used for biochar production.
With this information, a mathematical model was developed
that could account for three possible scenarios. In one, the
maximum possible amount of biochar was made by using all sustainably
available biomass. Another scenario involved a minimal amount
of biomass being converted into biochar, while the third offered
a middle course.
The maximum scenario required significant changes to the
way the entire planet manages biomass, while the minimal scenario
limited biochar production to using biomass residues and wastes
that are readily available with few changes to current practices.
The study found that the maximum scenario could offset up
to the equivalent of 1.8 billion metric tons of carbon emissions
annually and a total of 130 billion metric tons in the first
100 years. Avoided emissions include the greenhouse gases
carbon dioxide, methane and nitrous oxide. The estimated annual
maximum offset is 12 percent of the 15.4 billion metric tons
of greenhouse gas emissions that human activity currently
adds to the atmosphere each year.
Researchers also calculated that the minimal scenario could
sequester just under 1 billion metric tons annually and 65
billion metric tons during the same period.
Instead of making biochar, biomass can also be burned to
produce bioenergy from heat. Researchers found that burning
the same amount of biomass used in their maximum biochar scenario
would offset 107 billion metric tons of carbon emissions during
the first century. The bioenergy offset, while substantial,
was 23 metric tons less than the offset from biochar.
However, the team also added that a flexible approach - including
the production of biochar in some areas and bioenergy in others
- would create optimal greenhouse gas offsets. Their study
showed that biochar would be most beneficial if it were tilled
into the planet's poorest soils, such as those in the tropics
and the Southeastern United States.
Those soils, which have lost their ability to hold onto nutrients
during thousands of years of weathering, would become more
fertile with the extra water and nutrients the biochar would
help retain. Richer soils would increase the crop and biomass
growth - and future biochar sources - in those areas.
Biochar has been found or used in the Amazonian soils. Pre-Columbian
Amazonian natives are believed to have used biochar to enhance
soil productivity and made it by smoldering agricultural waste.
European settlers called it Terra Preta de Indio.
Biochar can be used to hypothetically sequester carbon. In
the natural carbon cycle, plant matter decomposes rapidly
after the plant dies, which emits CO2
- the overall natural cycle is carbon neutral. Instead of
allowing the plant matter to decompose, pyrolysis can be used
to sequester some of the carbon in a much more stable form.
Biochar thus removes circulating CO2
from the atmosphere and stores it in a stable soil form, making
it a carbon-negative process.
There is still much to learn about this process which shows
so much potential.
Download the study - 'Sustainable biochar to mitigate
global climate change' - Click
Here
|
