Why the Big Biochar Experiment?
There is increasing interest in the use of biochar as an organic soil enhancer. The first UK Biochar Research Centre was established in Edinburgh in 2008. Since its official introduction into the Climate Change debate at the United Nations Conference of Parties in Poznan, biochar has been hailed as the solution to several environmental problems of our century, including climate change, deforestation and food security [6]. Experiments in tropical and sub-tropical soils have shown that biochar massively increases crop productivity [2]. However, research on biochar in Britain is still in its infancy [5]. Whereas we understand the long term benefits it has had on the Amazonian Terra Preta soils, studies on European soils are just beginning.
Biochar
Biochar is the carbon rich product obtained from heating biomass (e.g. plant waste) in a closed container with little or no available air. In more technical terms, biochar is produced by thermal decomposition of organic material under a limited supply of oxygen (O2), and at relatively low temperatures (<700°C), a process termed low temperature pyrolysis. This produces a highly stable form of carbon, essentially trapping carbon in a structure that prevents its release back to the atmosphere for hundreds to thousands of years. Therefore biochar has potential as a carbon sequestration and climate change mitigation technology as well as providing a sustainable way to restore the soil fertility of existing farmed areas.
Application of biochar to land is not a new concept. Recent research on the dark earths of the Amazon Basin, the 'Terra Preta', has revealed that large applications of charred materials, likely residues from burning biomass, were applied to the soil making them significantly more fertile than surrounding soils that did not benefit from this practice [8, 10]. What the Terra Preta story really tells us is that the future of humanity and this planet could well rest on us re-learning what our ancestors once knew [4].
Application of biochar to land is not a new concept. Recent research on the dark earths of the Amazon Basin, the 'Terra Preta', has revealed that large applications of charred materials, likely residues from burning biomass, were applied to the soil making them significantly more fertile than surrounding soils that did not benefit from this practice [8, 10]. What the Terra Preta story really tells us is that the future of humanity and this planet could well rest on us re-learning what our ancestors once knew [4].
Physical properties.Most of the beneficial effects of biochar are due to the extremely high surface area of biochar particles at the microscopic level. This structure changes the physical properties of the soil, creating a reef-like structure in which microfauna and microflora thrive [1] and that nutrients are thought to attach themselves to (adsorb), thus increasing their availability to plants [4].
 Micrograph of biochar. Its high porosity, small holes are about 1 / 100 of a millimeter in diameter, make it an ideal environment to retain water, nutrients and microorganisms. Image: Best Energies |
Storing Carbon Image: soil science, creative commons
Terrestrial ecosystems contain large amounts of carbon in the living biomass, in the dead organic matter on the forest floor, and incorporated in the soil. Due to the accumulation of biomass and the increase in dead organic material, soil has the potential to absorb carbon from the atmosphere, making it a net carbon sink. As plants photosynthesize, they take CO2 out of the atmosphere. When biochar is made, some of this carbon returns to the atmosphere when the plant material is burned (during pyrolysis). However, up to 50% of the carbon in dry plant material remains in biochar as a highly stable form of carbon. When added to soil, this carbon will remain there for hundreds or thousands of years, which is far longer than most carbon contained in compost, plant or animal residues, which rapidly oxidizes and returns carbon to the atmosphere. As a result, the use of biochar in the soil offers a large and long-term carbon sink [6, 8].
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