Potential for Carbon Sequestration in European Soils

One of the main options for carbon mitigation identified by the IPCC is the sequestration of carbon in soils. In this paper we use statistical relationships derived from European long-term experiments to explore the potential for carbon sequestration in soils in the European Union. We examine five scenarios, namely (a) the amendment of arable soils with animal manure, (b) the amendment of arable soils with sewage sludge, (c) the incorporation of cereal straw into the soils in which it was grown, (d) the afforestation of surplus arable land through natural woodland regeneration, and (e) extensification of agriculture through ley-arable farming. Our calculations suggest only limited potential to increase soil carbon stocks over the next century by addition of animal manure, sewage sludge or straw (<15 Tg C y-1), but greater potential through extensification of agriculture (~40 Tg C y-1) or through the afforestation of surplus arable land (~50 Tg C y-1). We estimate that extensification could increase the total soil carbon stock of the European Union by 17%. Afforestation of 30% of present arable land would increase soil carbon stocks by about 8% over a century and would substitute up to 30 Tg C y-1 of fossil fuel carbon if the wood were used as biofuel. However, even the afforestation scenario, with the greatest potential for carbon mitigation, can sequester only 0.8% of annual global anthropogenic CO2-carbon. Our figures suggest that, although efforts in temperate agriculture can contribute to global carbon mitigation, the potential is small compared to that available through reducing anthropogenic CO2 emissions by halting tropical and sub-tropical deforestation or by reducing fossil fuel burning.

For related work, see:

Smith et al. 1998. Preliminary estimates of the potential for carbon mitigation in European soils through no-till farming Global Change Biology 4:679-685. Abstract and data at http://cdiac.ornl.gov/programs/CSEQ/terrestrial/PeteSmithetal98/PeteSmith98.htm.

Smith et al. 2000. Meeting Europe's climate chanage committments: quantitative estimates of the potential for carbon mitigation by agriculture. Global Change Biology 6:525-539. Abstract at http://cdiac.ornl.gov/programs/CSEQ/terrestrial/PeteSmithetal2000/petesmith00.htm.

Smith et al. 2001. Enhancing the carbon sink in European agricultural soils: Including trace gas fluxes in estimates of carbon mitigation potential. Nutrient Cycling in Agroecosystems 60:237-252.

Smith et al. 1997. Opportunities and limitations for C sequestration in European agricultural soils through changes in management. In: Management of Carbon Sequestration in Soil (R. Lal ed.), pp. 143-152. Advances in Soil Science. CRC press, Boca Raton, Florida.

Smith et al. (eds). 1997. Evaluation and comparison of soil organic matter models using datasets from seven long-term expermints. Special Isssue of Geoderma, 81:1-225.