26 May 2011
James Lovelock has said that charcoal – if adopted by farmers around the world to increase the yield of their crops – could be our main hope for combating the worst effects of global warming. George Monbiot wrote an article in The Guardian suggesting that biochar (charcoal intended for agricultural purposes) could lead to destructive monocultures if the process is allocated carbon credits and taken up by large-scale agribusiness. The hope and the fear are both realistic, though there is little chance that the technology can attract carbon credits because of difficulties over certification. We are focusing on Lovelock’s hope.
The science is complex so this is a gross simplification. Plants capture carbon dioxide from the air through photosynthesis. If you char the plants (wood is not necessary) and bury the char, carbon is captured, almost permanently, and oxygen released: hence carbon dioxide is extracted from the atmosphere. The microscopic cavities of charcoal allow it to retain moisture and provide a refuge for microbes, fungus and mycorrhizae, which associate with plant roots. So biochar is particularly useful for restoring fertility to degraded arid soils in the tropics.
The project is being run by SCAD, a large NGO in Tamil Nadu that is in touch with 500 villages. If farmers see positive results from trials it is likely that they will wish to adopt the process, particularly since the cost of synthetic fertiliser is rising. We have a head start because a banana farmer had been using waste rice-husk charcoal and ash from a mill and claims that his use of water has halved, less fertiliser is needed and his yield has increased in quantity and quality. The practice spread to his neighbours, and other farmers are showing an interest. Actually, the use of charcoal to modify soil has a long history in India.
There is a problem over equipment. Traditional charcoal-making uses wood and has health hazards. Our friend Dr Ravikumar (seen in the pyrolysis photo) first sparked our interest three years ago with his Anila cooking stove. But larger equipment is necessary for village communities if they are to produce sufficient biochar for agricultural use. Searching the web led to David meeting Black-is-Green in Australia who make a pyrolyser that is sufficiently robust and simple for operation by communities that do not have a background in the technology.
The pilot project, which opened in March, serves SCAD’s 5,000-student technical college, so is bigger than appropriate for villages. It has two parts. An anaerobic biodigester is run on green waste from the college kitchen and local markets. It produces gas (for cooking) and electricity as well as providing slurry to permeate the biochar. The pyrolyser is run on dry agricultural waste and prosopis (an invasive bush on the surrounding scrubland) and is driven by a thermal-electric generator strapped to its side. Waste materials and labour are the only inputs for both parts. SCAD has an organic farm adjacent to the project and this is where field trials using biochar are being carried out. However, the first programme is for rigorous scientific pot trials – designed by Evelyn Krull of CSIRO in Australia and analysed at Limerick University – to determine the nature of the products, and how much to mix with local soils.
We are not certain how the project will develop but anticipate that village communities, with whom SCAD has a close relationship, will gather waste materials. They will produce their own slurry from green waste, and a mobile pyrolysis unit will be taken round to process the dry waste. Villagers are, however, already attempting to make their own biochar. Their motivation, of course, is not global warming – although this is seriously affecting them – but to increase the yield of their crops. The project is founded on Lovelock’s view that farmers will adopt the practice when they see the benefits.
The RH Southern Trust funded the pilot project but other funding is needed for the Soil Fertility Project to spread at SCAD and elsewhere. We are already in consultation with an organisation in the Cameroons.