Climate expert claims to have developed cleanest way of fixing CO2 in 'biochar' for burial on an industrial scale
Alok Jha, guardian.co.uk 13 Mar 09;
Giant microwave ovens that can "cook" wood into charcoal could become our best tool in the fight against global warming, according to a leading British climate scientist.
Chris Turney, a professor of geography at the University of Exeter, said that by burying the charcoal produced from microwaved wood, the carbon dioxide absorbed by a tree as it grows can remain safely locked away for thousands of years. The technique could take out billions of tonnes of CO2 from the atmosphere every year.
Fast-growing trees such as pine could be "farmed" to act specifically as carbon traps — microwaved, buried and replaced with a fresh crop to do the same thing again.
Turney has built a 5m-long prototype of his microwave, which produces a tonne of CO2 for $65. He plans to launch his company, Carbonscape, in the UK this month to build the next generation of the machine, which he hopes will process more wood and cut costs further.
He is not alone in touting the benefits of this type of charcoal, known as biochar or biocharcoal. The Gaia theorist, James Lovelock, and Nasa's James Hansen have both been outspoken about the potential benefits of biochar, arguing that it is one of the most powerful potential solutions to climate change. In a recent paper, Hansen calculated that producing biocharcoal by current methods of burning waste organic materials could reduce global carbon dioxide levels in the atmosphere by 8ppm (parts per million) over the next 50 years. That is the equivalent of three years of emissions at current levels.
Turney said biochar was the closest thing scientists had to a silver-bullet solution to climate change. Processing facilities could be built right next to forests grown specifically to soak up CO2. "You can cut trees down, carbonise them, then plant more trees. The forest could act on an industrial scale to suck carbon out of the atmosphere."
The biochar could be placed in disused coal mines or tilled into the ground to make soil more fertile. Its porous structure is ideal for trapping nutrients and beneficial micro-organisms that help plants grow. It also improves drainage and can prevent up to 80% of greenhouse gases such as nitrous oxides and methane from escaping from the soil.
In a recent analysis of geo-engineering techniques published in the journal Atmospheric Chemistry, Tim Lenton, a climate scientist at the University of East Anglia, rated producing charcoal as the best technological solution to reducing CO2 levels. He compared it to other geo-engineering techniques such as dumping iron in oceans or seeding clouds to reflect the sun's radiation and calculated that by 2100 a quarter of the effect of human-induced emissions of CO2 could be sequestered with biochar production from waste organic matter, giving a net reduction of 40ppm in CO2 concentration.
Johannes Lehmann of Cornell university has calculated that it is realistically possible to fix 9.5bn tonnes of carbon per year using biochar. The global production of carbon from fossil fuels stands at 8.5bn tonnes.
Charcoal is usually produced by burning wood in high-temperature ovens but this process is dirty and only locks around 20-30% of the mass of the wood into charcoal. Turney's idea to use a microwave, which he found could lock away up to 50% of the wood's mass, came from a cooking accident when he was a teenager, in which he mistakenly microwaved a potato for 40 minutes and found that the vegetable had turned into charcoal. "Years later when we were talking about carbon sequestration I thought maybe charcoal was the way to go," he said.
A number of governments are investing their hopes for sequestering CO2 from the atmosphere in large-scale carbon capture and storage projects. But Turney said this would not provide a full solution. "It's only for large single sources of emissions like large power stations and that accounts for about 60% of emissions. It doesn't deal with anything up in the atmosphere already which is driving the changes we see today."
Chris Goodall, writer of the Carbon Commentary blog, proposed biochar as a solution to climate change in his recent book, Ten Technologies to Save the Planet. "The only big problem is organising it on a large enough scale," he said. "Organising it so that farmers get paid and put the charcoal in the ground rather than burning it for their own food is a big problem to organise on a global scale."
This could be done if biochar were incorporated into the carbon markets making it more profitable to bury rather than burn. There is an emerging campaign, he said, to get
governments to recognise biochar in the post-Kyoto agreement on climate change that will be negotiated in Copenhagen later this year.
Biochar: Is the hype justified?
Roger Harrabin, BBC News 16 Mar 09;
Green guru James Lovelock claims that the only hope of mitigating catastrophic climate change is through biochar - biomass "cooked" by pyrolysis.
It produces gas for energy generation, and charcoal - a stable form of carbon.
The charcoal is then buried in the ground, making the process "carbon negative".
Researchers say biochar can also improve farm productivity and cut demand for carbon-intensive fertilisers.
There's a flurry of worldwide interest in the technology, but is the hype justified?
Fertile ground
A ripe whiff of sludge drifts across the sewage works in Bingen, Germany, as a conveyor belt feeds a stream of semi-dried effluent into a steel container.
Behind the container, the treated effluent emerges in the form of glittering black granules. In a flash of eco-alchemy, they are turning sewage into charcoal.
The charcoal is then buried to lock the carbon into the ground and prevent it entering the atmosphere.
Proponents of the technology say it is so effective at storing carbon that it should be included in the next global climate agreement.
Burying the biochar can also improve soil fertility, say experts.
Field trials are about to begin at Rothamsted, south-east England, to assess the benefits to soil structure and water retention.
Experiments in Australia, US and Germany are already showing some remarkable results - especially on otherwise poor soils where the honeycomb granules of biochar act as a reservoir for moisture and fertilisers.
A growing worldwide movement is now bringing together the soil scientists fascinated by the benefits of biochar, which was first discovered in Pre-Columbian Amazonia, and the engineers devising new ways of making the char.
They are being backed by activists who are concerned about climate change.
At Bingen, the design engineer for the biochar plant, Helmut Gerber, originally devised the pyrolysis equipment to overcome the problem of ash from sewage waste choking conventional boilers.
Normally, sewage treatment is a significant source of greenhouse gases. The waste is usually incinerated (with more emissions) and the resulting ash is used in the building industry.
At Bingen, 10% of the sewage stream is being diverted to the prototype pyrolysis plant, where it is heated with minimum oxygen.
Carbon monoxide and methane are driven off and burned to heat the pyrolysis process.
Mr Gerber claims his process radically cuts the fuel costs and carbon emissions needed to treat the sewage.
'Carbon negative' process
Working with Professor Winfried Sehn from Bingen's University of Applied Sciences, Mr Gerber calculates that 60% of the carbon from the sewage is locked up in the char.
The buried carbon will be kept from entering the atmosphere for a projected 1,000 years or more.
And as the sewage was originally created from plants, which removed CO2 from the atmosphere, the total process is described as carbon negative.
The pyrolyser at Bingen - like others being developed elsewhere - can transform any carbon-based substance, including some plastics.
That means pyrolysis can get energy from agricultural waste, food waste and biomass. But the catch is that it creates less energy than burning biomass in a conventional way.
Research by oil giant Shell, showing a keen interest in biochar as a carbon storage mechanism, suggests that it can capture half the carbon from the biomass by foregoing a third of the potential energy.
For all its apparent benefits, there are substantial barriers to the progress of biochar.
Perfecting and disseminating the technology at an affordable price will be an issue.
Moreover, current financial systems reward energy production from biomass and waste - not carbon storage. Biochar would need clear global incentives.
One key to its progress will be ongoing research into the soil benefits.
The porous biochar attracts worms. It also captures nutrients that would otherwise run off the land, which reduces the need for carbon-intensive fertilisers.
Research at Cornell University in New York, US, suggests that burying biochar appears to double the capacity of soils to store organic carbon (compost releases its carbon in a few years).
Research in Australia suggests that biochar also reduces emissions of the powerful greenhouse gas nitrous oxide from soil.
New studies at the University of Bayreuth, Germany, shows that biochar may almost double plant growth in poor soils.
"Research on biochar began back in 1947," says Dr Bruno Glaser, a researcher from the University of Bayreuth.
"But this has been forgotten until the 1980s. Now there is a lot of excitement about what biochar can achieve."
Dr Glaser is working on studies to see how effective it proves to be on poor soils in northern Germany.
At Newcastle University, Professor David Manning is also an enthusiast. He says with the right incentives biochar could perhaps lock up as much carbon as the amount generated by aviation.
Several biochar stoves have been developed for use in developing countries. Belize and a number of African governments are attempting to get biochar accepted as a climate change mitigation and adaptation technology for the post-2012 treaty to be negotiated in Copenhagen in December.
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