Soil organic carbon

Restoring soil carbon can reverse global warming
Erich J. Knight, February 21, 2008

Here is a strait forward conversion of the impact of building soil organic material (SOM) on ppm of GHGs using just marginal land.

http://news.mongabay.com/2008/0221-soil_carbon_lovell_interview.html

Tony Lovell of Soil Carbon P/L in Australia estimates that by actively supporting regrowth of vegetation in damaged ecosystems, billions of tons of carbon dioxide can be sequestered from the atmosphere.

"Determining how much carbon dioxide (CO2) can physically be consumed from the atmosphere?

As the planet has 7.8 billion tonnes of carbon dioxide in circulation for each 1 ppm of atmospheric CO2, and there are 5 billion hectares of inappropriately managed or unmanaged, desertifying savannahs on the Earth (which on empirical evidence we contend to be the case), the question that should sensibly be asked is: How much carbon dioxide would be absorbed if policies were put in place (in Australia and elsewhere) that caused the focus of on-ground management to be deliberately directed towards the widespread consumption of cyclical GHGs within the currently under-utilised savannah lands?

Consumption of CO2 per hectare
• One hectare is 10,000 sq. metres. If a hectare of soil 33.5 cm deep, with a bulk density of 1.4 tonnes per cubic metre is considered, there is a soil mass per hectare of about 4,700 tonnes.
• If appropriate management practices were adopted and these practices achieved and sustained a 1% increase in soil organic matter (SOM)6, then 47 tonnes of SOM per hectare will be added to organic matter stocks held below the soil surface
• This 47 tonnes of SOM will contain approximately 27 tonnes of Soil Carbon (ie 47 tonnes at 58% Carbon) per hectare
• In the absence of other inputs this Carbon may only be derived from the atmosphere via the natural function known as the photo-synthetic process. To place approximately 27 tonnes of Soil Carbon per hectare into the soil, approximately 100 tonnes of carbon dioxide must be consumed out of the atmosphere by photosynthesis
• A 1% change in soil organic matter across 5 billion hectares will sequester 500 billion tonnes of physical CO2
Converting global Soil Carbon capacity to ppm of atmospheric GHGs
1. Every 1% increase in retained SOM within the topmost 33.5 cm of the soil must capture and hold approximately 100 tonnes per hectare of atmospheric carbon dioxide (the variability in the equation being due only to the soil bulk density). We submit that under determined, appropriate management, that this is readily achievable within a very few years
2. For each 1% increase in SOM achieved on the 5 billion hectares there will be removed 64 ppm of carbon dioxide from atmospheric circulation (500,000,000,000 tonnes CO2 / 7,800,000,000 tonnes per ppm = 64 ppm).
3. Soil Organic Matter is the plant material released into the soil during the natural phases of plant growth. It includes root material sloughed off below the soil surface and plant litter carried into the soil by microbes, insects and rainfall
4. Soil Carbon is the elemental carbon contained within Soil Organic Matter (SOM).
5. One tonne of CO2 contains 12/44 units of carbon (ie 0.27 tonnes of carbon per tonne of CO2.). Therefore 27 tonnes of carbon sequesters 27/0.27 = 100 tonnes CO2 (rounded). NB Carbon atomic weight 12, oxygen atomic weight 16 ie CO2 = 12+(16+16) = 44
The global opportunity and numbers

It appears that the pre-industrial level of atmospheric carbon dioxide was 280ppm, and that globally we are now at 455ppm, and heading towards 550ppm. To get from 550ppm back to 280ppm, 270ppm must be removed. Globally, a 4.2% increase in SOM would potentially reverse the expected situation. In any case, any form of determined management will substantially reduce the now crippling legacy loadings in the atmosphere.

Erich J. Knight
1047 Dave Berry Rd.
McGaheysville, VA. 22840
540-289-9750
shengar@aol.com

Soil Organic Carbon
Jan Skjemstad, CRC Greenhouse Accounting

In Summary

Soil OC is a significant source and sink of atmospheric CO2

Soil is a complex, biologically active medium

Soil OC is not one material

Changes in SOC can be measured directly or can be modelled

The C sink value of soils is limited BUT increasing and maintaining SOC has many benefits for improved productivity and soil resilience

Manage carbon to sustain soil structure
Jan Skjemstad, CSIRO LAND AND WATER AND CRC FOR GREENHOUSE ACCOUNTING in FARMING AHEAD No. 158 March 2005

Soil organic carbon plays a critical role in the biological, chemical and physical health of a soil. But little is known about how crop management impacts on soil organic carbon levels and thus soil health. This article describes how a new approach to understanding this relationship could help farmers better manage soil organic carbon.

Australian approaches to measuring and monitoring soil organic carbon
Jeff Baldock, Jan Skjemstad, Evelyn Krull
CSIRO Land and Water and CRC for Greenhouse Accounting PMB 2, Glen Osmond, SA 5064, Australia

SOC measurement and composition
Temporal variation in SOC content

delling measurable SOC fractions

Monitoring SOC contents in Australia (National
Carbon Accounting System, NCAS)

Black Carbon from Rice Residues as Soil Amendment and for Carbon Sequestration
Haefele, SM, Konboon, Y, Knoblauch, C, Koyama, S, Gummert, M, Ladha, JK
Cornell University Poster Presented to International Rice Research Institute, September 14 2006

On highly weathered soils in tropical and subtropical climates, maintenance of soil organic matter is essential to sustain system productivity and avoid rapid soil degradation. But climatic conditions as well as soil characteristics favor the rapid decomposition of organic matter. However, several recent studies indicated that black carbon, the product of incomplete combustion of organic material, could combine characteristics highly beneficial for soil nutrient dynamics with high stability against chemical and microbial breakdown.