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Biochar is a carbon-rich product obtained
when biomass is heated in a closed container. It is similar
to charcoal and largely resistant to decomposition. Biochar
offers a unique tool to combat global warming because
it can stabilise carbon that has been absorbed by growing
plants and store it in the soil for hundreds of years,
so preventing its re-entering the carbon cycle. Biochar
has a number of benefits.
It can:
• improve soil fertility and structure
• reduce the need for costly fertilisers such as nitrates
and phosphates, the production of which themselves
add significantly to greenhouse gas emissions
• reduce nitrate runoff, thereby reducing nitrous oxide
greenhouse gas emissions
• improve the soil’s water retention ability , reducing
irrigation costs and combating desertificatio
Biochar’s potential as carbon-negative
has been recognised by a number of leading commentators,
including Lord Nicholas Stern, and the United Nations
Convention to Combat Desertification (UNCCD) has successfully
procured that biochar was included on the Agenda for
the 2009 UNFCCC Copenhagen climate change negotiations.
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Biochar increases the productivity
of most soils. This has been well documented both in
the UK and abroad, with small pot trials and larger field
trials. The efficacy of biochar is well documented in
Biochar for Environmental Management, edited by Johannes
Lehman of Cornell University and Stephen Joseph of Anthroterra,
published by Earthscan.
Once in the soil, biochar provides
long-term benefits that cumulatively build up as more
biochar is added to the soil each year. It has a highly
porous structure, similar to charcoal which is used as
a filter for many industrial purposes, and thus retains
moisture and reduces leaching of nutrients from the soil.
This saves in both irrigation and fertiliser costs. The
porous structure provides a protective environment for
the beneficial soil fungi and bacteria which help plant
roots extend their reach, resulting in greater plant
growth and productivity. The resulting higher land yields
and further carbon credits due to the reduction in nitrate
application and run off can be further monetised.
The images above show increased plant growth in a number
of trials:
The Copenhagen climate talks, while
disappointing in some aspects, led to agreement that
forest and soil carbon sinks will be included in any
future global climate agreement. As a result the importance
of biochar as a way of long-term augmentation of soil
carbon levels will be recognised when an agreement is
finally achieved. A major weakness of the Kyoto Protocols
was that they ignored forest and soil carbon sinks. This
new understanding of the importance of agricultural activity
and of the soil as a secure carbon sink will help ensure
that biochar production and sequestration in soil will
be economically rewarded in any future carbon regime.
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