Skip Navigation

Features

'Dark earth' and its carbon-holding powers

Source: Nature Reports Climate Change

15 June 2009 | EN | 中文

charcoal_Wikipedia_Romary.jpg

Should we be squirreling away carbon in charcoal?

Wikipedia/Romary

Biochar has been touted as a great hope for mitigating climate change and boosting soil fertility. But critics caution that more research is needed to understand its effects.

Biochar is based on terra preta, or dark earth — a mixture of bone, manure and charcoal that was first used in the pre-Columbian era to enhance the infertile soil of the central Amazon basin. Some of the charcoal has remained in the soil for thousands of years, leading scientists to believe that it could be used elsewhere as a long-term carbon store.

Johannes Lehmann, a soil scientist at Cornell University, New York, and colleagues, calculate that half of the estimated six billion tonnes of carbon in agricultural, forestry and animal waste could be turned into biochar. And for every tonne of biochar, a third of a tonne of biofuel by-product could be produced.

Some advocates are developing industrial-scale microwaves to produce biochar but critics are concerned that developing a market for biochar could encourage the destruction of tropical rainforests — while others question whether the carbon would really remain in the soil for such long periods.

Lehmann admits biochar is "not a silver bullet" and that no technology could compensate for the current level of emissions. But biochar could help, he says.

Link to full article in Nature Reports Climate Change

Comments

Alan Page ( United States of America )

12 July 2009

The main argument against the use of biochar as a carbon sequestration agent takes two forms: 1) opposition to large industrial applications that profit from char production, and 2) Wardel's test of carbon loss within bagged samples. The control of the former issue is likely to be productively dealt with by society rather than by worrying - if small scale systems are feasible for farmers to use as part of their normal soil management activity and the benefits to them outweigh the use of additional fertilizer and they can accumulate the energy needed to run their local operations from materials that would be respired into CO2 in a few years, all will benefit. There are a number of other factors of biochar activity in soils that have been glossed over that opponents miss in their rush to maintain the status quo. This is unfortunate because there are many other damage points produced by current systems that widespread application of effective small scale systems could correct. Even advocates as prominent as Lester Brown decry the loss of soil carbon as the cause of failed states, but he has not begun to understand the potential for biochar to ameliorate that condition. I would worry more about human population levels than industrial perfidy. The US is now facing the effects of large scale agribusiness excesses and these will be reined in by people choosing against these greed based systems. Local farms need support with effective systems. As to the second item, Danny Day suggested that placing carbon in an isolated environment where a biological population can still operate but without the normal conditions where there are many different kinds of materials for fuel is not a fair measure of what actually will happen in a soil environment. It is akin to placing a human and a mouse in a confined space for an extended period and asking whether people eat mice. Writers could do more homework before writing!

Add your comment

All comments are subject to approval and we reserve the right to edit comments containing inappropriate/unsuitable language. SciDev.Net holds copyright for all material posted on the website. Please see terms of use for further details.

You need to be signed in to post a comment or to email a consenting comment author. Please sign in or sign up.

Back to Features
To the top