Biochar is a carbon-negative soil improvement technology that takes at least 25% of organic carbon out of the cycle and converts it into solid mineral carbon that remains stable in soil for thousands of years.
It increases soil fertility and raises agricultural productivity, reducing the need for synthetic fertilizers. It slows evaporation by helping soil retain moisture, which reduces nutrient-leaching and the need for irrigation.
Decomposing biomass adds large amounts of methane and carbon dioxide to the atmosphere and so does traditional wood-burning and composting. Burying biochar instead reduces the flow of greenhouse gases into the atmosphere.
Sequestering carbon in the ground is now a sensible way to mitigate global warming, according to prominent scientists such as James Hansen, head of the NASA Goddard Institute for Space Studies, and James Lovelock, creator of the Gaia hypothesis.
Biochar acts like a coral reef for microbes and fungi that are beneficial to soil and plants, enhancing root growth.
Just as coral reefs are the richest ecosystems in the ocean for biodiversity, so biochar in the soil likewise provides a base on which soil biodiversity develops, creating a more resilient ecosystem. Building soil biodiversity restores degraded soils improves soil structure, reducing the need for pesticides by producing healthier plants.
Charcoal is a high-carbon, fine-grained residue produced by pyrolysis of biomass. If you heat almost any biological material to a certain temperature, and restrict or exclude oxygen, pyrolysis occurs instead of normal combustion.
Pyrolysis is the direct thermal decomposition of biomass in the absence of oxygen to obtain an array of solid (biochar), liquid (bio-oil) and gas (syngas) products. The specific yield depends on the design of the process - it can be optimised to prioritise either energy or biochar yield.
The gas can be used similarly to other fuels, to generate electricity, either by backyard mechanics or by sustainable energy entrepreneurs. The United Nations Global Clean Stove Initiative is providing 100 million clean biomass cook-stoves for the developing world.
Green technologies that convert waste to energy often produce biochar as a byproduct, and most processes that produce it use efficient renewable energy sources. Industry and communities can apply them to sustainably exploit waste biomass resources.
In Auckland Graham hopes to help set up a process using the proposed curbside collection of foodscraps as compost in combination with pyrolised greenwaste. Construction and demolition timber can be diverted from landfills, sawdust from sawmills and the output from chippers shredders can be used.
Biochar further advances the green cause when used as a filter: not only to purify water but also to absorb nutrient run-off from farms, and to clean and regenerate rivers and lakes.
Current forestry uses tree trunks only, leaving the branches and leaves to rot re-enter the atmosphere as greenhouse gases - so it makes sense to turn that into biochar instead.
Just consider the difference for reforestation of the Amazon: slash and burn leaves only 3% of the carbon from the organic material in the soil, whereas slash and char can sequester up to 50% of the carbon in a highly stable form! That's from biochar's Wikipedia page.
Dr. Tim Flannery is Professor of Environmental Sustainability at Macquarie University in Sydney, chairman of the Copenhagen Climate Council, and head of the Climate Commission in Australia. His 1994 book “The Future Eaters” is an ecological history of Australasia, and his 2005 book about global warming “The Weather Makers” made the New York Times best-seller list.
In his Amazon review of "The Biochar Revolution", he points out that biochar-making techniques are readily accessible to everyone - all of us, in our own gardens and communities, can contribute and make a genuine difference now without having to wait for our governments and institutions.
If enough people do so, the collective effort will generate sustainable benefits for everyone. He reckons that biochar may now be the most important initiative for the future of humanity!
Graham and Trevor are part of a group currently facilitating the formation of the "NZ Biochar Interest Group", which will be affiliated to the International Biochar Initiative.
If you are interested in finding out more, please contact: biocharnz [at] gmail.com