permaculture

["Saor Stetler" <sstetler@earthlink.net>]

Can Compost Heaps Cure Global Warming?

        

Submitted by News <http://www.scientificblogging.com/profile/news>  Account
on 24 February 2008 - 4:00pm. Environment
<http://www.scientificblogging.com/environment>  

Applying organic fertilizers, such as those resulting from composting, to
agricultural land could increase the amount of carbon stored in these soils
and contribute significantly to the reduction of greenhouse gas emissions,
according to new research published in a special issue of Waste Management &
Research.

Carbon sequestration in soil has been recognized by the Intergovernmental
Panel on Climate Change and the European Commission as one of the possible
measures through which greenhouse gas emissions can be mitigated. 

One estimate of the potential value of this approach - which assumed that
20% of the surface of agricultural land in the EU could be used as a sink
for carbon - suggested it could constitute about 8.6% of the total EU
emission-reduction objective. 

"An increase of just 0.15% in organic carbon in arable soils in a country
like Italy would effectively imply the sequestration of the same amount of
carbon within soil that is currently released into the atmosphere in a
period of one year through the use of fossil fuels," write Enzo Favoino and
Dominic Hogg, authors of the paper.

"Furthermore, increasing organic matter in soils may cause other greenhouse
gas-saving effects, such as improved workability of soils, better water
retention, less production and use of mineral fertilizers and pesticides,
and reduced release of nitrous oxide." 

However, capitalizing on this potential climate-change mitigation measure is
not a simple task. The issue is complicated by the fact that industrial
farming techniques mean agriculture is actually depleting carbon from soil,
thus reducing its capacity to act as a carbon sink. 

According to Hogg and Favoino, this loss of carbon sink capacity is not
permanent. Composting can contribute in a positive way to the twin
objectives of restoring soil quality and sequestering carbon in soils.
Applications of organic matter (in the form of organic fertilizers) can lead
either to a build-up of soil organic carbon over time, or a reduction in the
rate at which organic matter is depleted from soils. In either case, the
overall quantity of organic matter in soils will be higher than using no
organic fertilizer. 

"What organic fertilizers can do is reverse the decline in soil organic
matter that has occurred in relatively recent decades by contributing to the
build-up in the stable organic fraction in soils, and having the effect, in
any given year, of ensuring that more carbon is held within the soil," they
explain.

But calculating the value of this technique to climate change policies is
complicated. To refine previous calculations and to take account of the
positive and negative dynamics of carbon storage in soil, Favoino and Hogg
modelled the dynamics of compost application and build-up balancing this
with mineralization and loss through tillage.

Their results suggest that soils where manure was added have soil organic
carbon levels 1.34% higher than un-amended soils, and 1.13% higher than
soils amended with chemical fertilizers, over a 50-year period. "This is
clearly significant given the evaluations reported above regarding carbon
being lost from soils, and the increasing amount of carbon dioxide in the
atmosphere," they say.