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Biosequestration

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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, depleted oil or gas reservoirs (see oil depletion and peak oil), deep saline aquifers, or deep coal seams (see coal mining) (for all see geosequestration) or through the use of industrial chemical carbon dioxide scrubbing (see carbon capture and storage).

Plants and absorbing carbon from 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 and preventing deforestation. 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.A recent report by the Australian CSIRO found that forestry and forest-related options are the most significant and most easily achieved carbon sink making up 105 Mt per year CO2-e or about 75 per cent of the total figure attainable for the Australian state of Queensland from 2010-2050. Among the forestry options, the CSIRO report announced, forestry with the primary aim of carbon storage (called carbon forestry) clearly has the highest attainable carbon storage capacity (77 Mt CO2-e/yr) and is one of the easiest options to implement compared with biodiversity plantings, pre-1990 eucalypts, post 1990 plantations and managed regrowth. Legal strategies to encourage this form of biosequestration include permanent protection of forests in National Parks or on the World Heritage List, properly funded management and bans on use of rainforest timbers and inefficient uses such as woodchipping old growth forest.

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 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.

Improved agricultural and farming practices

Zero-till farming practices occur where there is much mulching but ploughing is not used, so that the carbon-rich organic matter in soil is not exposed to atmospheric oxygen, or to the leaching and erosion effects of rainfall. Over grazing is reduced by moving cattle and sheep away from grazed areas for several months. Ceasing ploughing has been alleged to encourage more ants to become predators of wood-eating (and C02 generating) termites, allows weeds to regenerate soils and helps slow water flows over the land. Dedicated biofuel and biosequestration crops, such as switchgrass (panicum virgatum), are also being developed. It requires from 0.97 to 1.34 GJ fossil energy to produce 1 tonne of switchgrass, compared with 1.99 to 2.66 GJ to produce 1 tonne of corn. Given that switchgrass contains approximately 18.8 GJ/ODT of biomass, the energy output-to-input ratio for the crop can be up to 20:1. Biosequestration can also be enhanced by farmers choosing crops species that produce large numbers of phytoliths. Phytoliths are microscopic spherical shells of silicon that can store carbon for thousands of years.

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. The Garnaut Climate Change Review recommends that a carbon price in a carbon emission trading scheme could include a financial incentive for biosequestration processes. Garnaut recommends the use of algal biosequestration (see algae bioreactor) to absorb the constant stream of carbon dioxide emissions from coal-fired electricity generation and metal smelting.

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." Saddler and King have argued that biosequestration and agricultural greenhouse gas emissions should not be handled within a global emissions trading scheme because of difficulties with measuring such emissions, problems in controlling them and the burden that would be placed on numerous small-scale farming operations.

References

  1. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008 p558. Garnaut (p609) defines biosequestration as involving greenhouse gases in general.
  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. CSIRO An Analysis of Greenhouse Gas Mitigation and Carbon Biosequestration Opportunities from Rural Land Use. Canberra. 2009. http://www.csiro.au/resources/carbon-and-rural-land-use-report.html, last accessed 8 October 2009
  7. Mark Diesendorf. Climate Action. UNSW Press. Sydney. 2009 p116
  8. 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.
  9. 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.
  10. 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
  11. David Beerling. The Emerald Planet. How Plants Changed Earth's History. Oxford University Press. Oxford 2007 pp194-195.
  12. 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
  13. 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
  14. Chris Goodall. Ten Technologies To Save The Planet. Green Profile. London 2008 pp 210-231
  15. Chris Goodall. Ten Technologies To Save The Planet. Green Profile. London 2008 pp 236-247
  16. Peter Andrews. Beyond the Brink. ABC Books. Sydney. 2008 p40
  17. Biotechnology Industry Organization (2007). Industrial Biotechnology Is Revolutionizing the Production of Ethanol Transportation Fuel pp. 3-4.
  18. Dale, B., Kim, S. Cumulative Energy and Global Warming Impact from the Production of Biomass for Biobased Products. Journal of Industrial Ecology. 2004; 7(3-4):147-162
  19. Samson, R. et al. Developing Energy Crops for Thermal Applications: Optimizing Fuel Quality, Energy Security and GHG Mitigation. In Biofuels, Solar and Wind as Renewable Energy Systems: Benefits and Risks. D. Pimental. (Ed.) Springer Science, Berlin, Germany. 2008. 395-423
  20. Parr JF and Sullivan LA. Soil carbon sequestration in phytoliths. Soil Biology and Biochemistry 2005; 37:117-124.
  21. Tom Fearon. Australia’s ‘massive advantage’ in bio-sequestration. Environmental Management News. Monday, 3 August 2009
  22. Guy Healey. Pond life fuels bio research The Australian. July 23, 2008
  23. International Energy Agency (2006). World Energy Outlook 2006 p. 8.
  24. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008. p558
  25. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008 p432.
  26. Ross Garnaut. The Garnaut Climate Change Review. Cambridge University Press. Melbourne (copyright held by Commonwealth of Australia) 2008. p582
  27. Saddler H and King H. Agriculture and Emissions Trading: The Impossible Dream. Australia Institute Discussion Paper 102. Australia Institute, Canberra. 2008.
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