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Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by an increased volume or quality of photosynthesis (through practices such as growing more trees and genetic engineering respectively), as well as enhanced soil carbon in agriculture. It has been crucial to the initiation, evolution and preservation of life and is a key policy concept in the climate change mitigation debate. It does not generally refer to the sequestering of carbon dioxide in oceans (see carbon sequestration) or rock formations (see geosequestration) or through the use of industrial chemical carbon dioxide scrubbing (see carbon capture and storage).

Carbon in the Earth's atmosphere

It is generally accepted by Geochemistry that the carbon dioxide content of the atmosphere since before the industrial revolution was 0.03 percent. The capture of atmosphereic C02 has been largely a function of absorption by sea water, vegetation and soils. The capacity of the oceans to absorb C02 is decreasing. Given the potential adverse effects of rising atmospheric C02 levels (see climate change) this increases the importance of developing policies and laws that increase both the global amount and efficiency of photosynthesis and biosequestration.

Reforestation

Canadell and Raupach have outlined four major strategies to mitigate atmospheric carbon emissions through reforestation. First, to increase the amount of forested land through a reforestation process. Second, to increase the carbon density of existing forests at a stand and landscape scale. Third, to expand the use of forest products that will sustainably replace fossil-fuel emissions. Fourth, to reduce carbon emissions that are caused from deforestation and degradation.

Enhanced photosynthesis

Biosequestration may be enhanced by improving photosynthetic efficiency by modifying RuBisCO genes in plants to increase the catalytic and/or oxygenation activity of that enzyme. One such research area involves increasing the earth's proportion of C4 carbon fixation photosynthetic plants. C4 plants represent about 5% of Earth's plant biomass and 1% of its known plant species, but account for around 30% of terrestrial carbon fixation. A new frontier in crop science consists of attempts to genetically engineer C3 staple food crops (such as wheat, barley, soybeans, potatoes and rice) with the "turbo-charged" photosynthetic apparatus of C4 plants.

Biochar

Biochar (charcoal created by pyrolysis of biomass) is a potent form of longterm (thousands of years) biosequestration of atmosphereic C02 derived from investigation of the extremely fertile Terra preta soils of the Amazon Basin. Placing biochar in soils also improves water quality, increases soil fertility, raises agricultural productivity and reduce pressure on old growth forests. As a method of generating bio-energy with carbon storage Rob Flanagan and the EPRIDA biochar company have has developed low-tech cooking stoves for developing nations that can burn agricultural wastes such as rice husks and produce 15% by weight of biochar; while BEST Energies in NSW Australia have spent a decade developing an Agrichar technology that can combust96 tonnes of dry biomass each day, generating 30-40 tonnes of biochar.

Implications for climate change policy

Industries with large amounts of C02 emissions (such as the coal industry) are interested in biosequestration as a means of offsetting their greenhouse gas production. In Australia, university researchers are engineering algae to produce biofuels (hydrogen and biodiesel oils) and investigating whether this process can be used to biosequester carbon. Algae naturally capture sunlight and use its energy to split water into hydrogen, oxygen and oil which can be extracted. Such clean energy production also can be coupled with desalination using salt-tolerant marine algae to generate fresh water and electricity.Many new bioenergy (biofuel) technologies, including cellulosic ethanol biorefineries (using stems and branches of most plants including crop residues (such as corn stalks, wheat straw and rice straw) are being promoted because they have the added advantage of biosequestration of C02. Dedicated biofuel and biosequestration crops, such as switchgrass, are also being developed. The Garnaut Climate Change Review recommends that a carbon price in a carbon emission trading scheme could include a financial incentive for biosequestration processes.

Barriers to increased global biosequestration

The Garnaut Climate Change Review notes many such barriers. "There must be changes in the accounting regimes for greenhouse gases. Investments are required in research, development and commercialisation of superior approaches to biosequestration. Adjustments are required in the regulation of land use. New institutions will need to be developed to coordinate the interests in utilisation of biosequestration opportunities across small business in rural communities. Special efforts will be required to unlock potential in rural communities in developing countries."

References

1. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008. p558
2. JE Lovelock. Gaia. A New Look at Life on Earth. Oxford University Press. Oxford. 1989 p80
3. Tim Flannery. The Weather Makers. The History and Future Impact of Climate Change. Text Publishing. Melbourne.2005. p29
4. CL Sabine et al. The oceanic sink for anthropogenic C02 Science 2004; 305:367-71.
5. Canadell, J. G., Raupach, M. R. Managing Forests for Climate Change. Science. 2008; 320: 1456-1457
6. Spreitzer RJ, Salvucci ME (2002). "Rubisco: structure, regulatory interactions, and possibilities for a better enzyme". Annu Rev Plant Biol. 53: 449–75. doi:10.1146/annurev.arplant.53.100301.135233. PMID 12221984.
7. Bond, W.J.; Woodward, F.I.; Midgley, G.F. (2005). "The global distribution of ecosystems in a world without fire". New Phytologist 165 (2): 525–538.
8. Osborne, C.P.; Beerling, D.J. (2006). "Review. Nature's green revolution: the remarkable evolutionary rise of C4 plants". Philosophical Transactions of the Royal Society B: Biological Sciences 361 (1465): 173–194
9. David Beerling. The Emerald Planet. How Plants Changed Earth's History. Oxford University Press. Oxford 2007 pp194-195.
10. Laird, David A., The Charcoal Vision: A Win–Win–Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil and Water Quality, Agronomy J 2008; 100: 178-181
11. Glaser, Bruno, Johannes Lehmann, and Wolfgang Zech, Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal – a review. Biology and Fertility Soils 2002;35:219
12. Chris Goodall. Ten Technologies To Save The Planet. Green Profile. London 2008 pp 210-231
13. Tom Fearon. Australia’s ‘massive advantage’ in bio-sequestration. Environmental Management News. Monday, 3 August 2009
14. Guy Healey. Pond life fuels bio research The Australian. July 23, 2008
15. International Energy Agency (2006). World Energy Outlook 2006 p. 8.
16. Biotechnology Industry Organization (2007). Industrial Biotechnology Is Revolutionizing the Production of Ethanol Transportation Fuel pp. 3-4.
17. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008. p558
18. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008. p582

• Photosynthesis
• Plant physiology
• Plant morphology
• Plant anatomy
• Climate change
• Climate forcing agents
• Greenhouse gases
• Carbon finance