Biochar 'can cut' greenhouse gases

Canberra Times
Saturday 21/8/2010 Page: 12

Using biochar made from crop waste or chicken manure to improve farm soil health can cut the world's greenhouse emissions by 12%, or roughly 1.8 billion tonnes a year, a new study says. A research team led by United States energy department soil chemist Jim Amonette found the organic charcoal-like substance could play "a significant role" in tackling global warming while also boosting the world's food production.

The study, published online by science journal Nature Communications, calculated the carbon content of the world's crop wastes such as rice husks, peanut shells, corn leaves and stalks, as well as farm animal manure and urban green waste. It used computer modelling to estimate how much of this biomass, could be used to produce biochar.

It found using biomass to produce biochar was up to 80% more beneficial than burning organic waste to produce bioenergy or biofuels. But Dr Amonette warned ambitious projects were needed to reap the benefits of biochar, and using it to cut global emissions "will not be accomplished by half-hearted measures".

An Australian team member. University of New South Wales renewable energy engineer Professor Stephen Joseph, said the study showed biochar "can help tackle our climate concerns in a major and sustainable way". "The beauty of the technology is that it is a win-win solution: it can be used to produce energy but at the same time reduce CO2 emission in the atmosphere", Professor Joseph said. According to the study, biochar can improve soil health and fertility by increasing microbial activity, reduce soil acidity, reduce loss of nutrients and raise plant nutrient uptake by boosting water retention.

Biochar is a fine-grained, highly porous charcoal made by burning plants, wood and other organic materials at high temperatures of between 400-800° in a process called slow Pyrolysis. Former Australian of the Year, climate change campaigner Professor Tim Flannery has described biochar as potentially "the single most important initiative for humanity's environmental future".

Dr Amonette said the scientific community had been "split on biochar" because of fears it could lead to loss of habit and land for food production. The study warns land clearing to establish plantations would release carbon in soils and trees, "Leading to an unacceptably high carbon pay back times" before any cuts to carbon emissions were achieved. Converting grasslands to biomass carbon crops" would result in a carbon-payback time greater than 10 years, and clearing rainforest would result in a carbon debt "in excess of 50 years".

The study's estimates of avoided greenhouse emissions were based on assumptions no agricultural land or native forest would be converted to biomass crop production. Other sustainability criteria included leaving sufficient crop waste to prevent soil erosion, not using crop waste used for fodder, not adding biochar made from treated building materials to agricultural soils and using only modern Pyrolysis technologies be used. These technologies fully recover the energy released in the process, and eliminate soot, methane and nitrous oxide emissions.