[Terrapreta] Pac NW Nat. Lab carbon sequestration research

[Thomas Deerfield]

In the last paragraph:
"On the horizon, researchers are looking at 
amending soil with highly persistent "biochar"...
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http://regionaloutreach.pnl.gov/nwtechtoday/article.asp?id=52

Synergy in Soil

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Researchers recently made a significant step in 
describing the complex interactions involved in 
using soil to store carbon, an important player in global climate change.


Researchers look to the soil to deal with rising CO2 levels

Researchers at Pacific Northwest and Argonne 
National Laboratories have made a significant 
step in describing the complex interactions 
involved in using soil to store carbon, an 
important player in global climate change. As 
atmospheric carbon dioxide levels rise, short- 
and long-term solutions are needed to store 
carbon removed from the air. Soil provides an 
abundant, readily available storage option­one 
designed by nature to hold carbon removed from air by plant photosynthesis.

"Creating short-term solutions, for say the next 
50 to 75 years, is critical to buy the world time 
to come up with greener energy sources and better 
ways to sequester carbon," said Vanessa Bailey, 
the team's microbiologist at PNNL.

Bringing together expertise and resources in soil 
physics, microbiology and chemistry, the 
researchers described the two major mechanisms 
they believe control the turnover of carbon in 
soil. By manipulating these mechanisms, the 
retention of carbon by soil can increase.

The first mechanism involves chemical alteration 
driven by the types of minerals present and by 
the diverse and abundant microbial community, 
which both stabilizes and releases carbon. Many 
fungi consume carbon in the soil, converting it 
into a more stable form; however, a portion of 
the consumed carbon is unavoidably respired as 
carbon dioxide to the atmosphere. While bacteria 
also contribute to carbon stabilization, they 
tend to use carbon less efficiently than fungi 
and to produce residues that are more readily degraded.

The second mechanism involves the physical 
properties of the soil itself. Soil structure, 
the arrangement of soil particles and the pore 
spaces between them, helps determine if a soil 
will hold carbon for decades or release it 
quickly. When present in certain types of soil 
pores, the carbon can be protected from 
microorganisms, oxygen, and other factors that could cause it to be released.

"We were able to clearly identify these 
mechanisms because we looked at the soil from a 
variety of scientific perspectives," said Jim 
Amonette, the team's soil chemist also at PNNL.

To increase the persistence of carbon in soil, 
the research team provided several 
recommendations. Encouraging the fungal community 
and increasing carbon inputs from roots by 
minimizing tillage and planting perennial crops 
enhances soil structure and increases carbon 
storage times. Managing water is also important. 
Cycling between moist and dry conditions, and 
avoiding long periods at either extreme, helps 
transform carbon into forms that are more likely to stay in the soil.

This research is part of the U.S. Department of 
Energy Consortium for Research on Enhancing 
Carbon Sequestration in Terrestrial Ecosystems 
(CSiTE) which also includes researchers at Oak Ridge National Laboratory.

In the near future, these researchers plan to 
develop methods to screen soils for carbon 
sequestration potential based on their microbial 
communities. On the horizon, researchers are 
looking at amending soil with highly persistent 
"biochar" that is produced when biomass is burned 
under low-oxygen conditions to release energy. 
This revolutionary approach may offer a long-term 
soil-based solution to the global climate change problem.
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