Scientists claim biochar ‘fertiliser’ will cut emissions
The principles and practices of organic farming, such as the use of clover for nitrogen fixing, are helpful in highlighting the options and opportunities for conventional farming.
There may be another, newer option. According to new research just published by a team of international scientists in the journal, Nature, a substance which can be made from farm waste could reduce the world’s greenhouse emissions by as much as 12%: biochar is a fine charcoal that can store carbon while improving soil.
Biochar is made by decomposing biomass, like plants, wood and other organic materials, at high temperature, in a process called slow pyrolysis.
“Biochar offers one of the few ways we can create power, while decreasing carbon dioxide levels in the atmosphere. And it improves food production in the world’s poorest regions by increasing soil fertility. It’s an amazing tool,” said Jim Amonette, a soil chemist at the US Department of Energy’s Pacific Northwest National Laboratory.
Some of the benefits of biochar include: it can take carbon and store it for hundreds of years; it can improve the soil’s functioning (water retention and nutrient levels); it can decrease nitrous oxide and methane emissions from the soil into which it is tilled; and it can produce some bio-based gas and oil during pyrolysis.
It is also one of the few substances that can disrupt the carbon dioxide cycle, because it releases oxygen from the cycle, as did coal in its formation millions of years ago.
The origins of biochar are in South America. Before settlers arrived, agricultural waste was smouldered by the farming inhabitants to help with soil fertility. This involved covering burning biomass with soil and then letting it smoulder. This process was labelled terra preta — or terra pretta de indio — by the European settlers who arrived.
This dark soil is still today more fertile (from the charcoal) than surrounding soils.
As with all supposed magic bullet solutions to climate change, there are pros and cons. Most who query biochar’s potential, and, indeed, many undecided experts, see it as a small part of a multi-strand solution.
It is acknowledged that it needs careful management of its potential, if it is to emerge as a positive. “Using biochar to reduce greenhouse gas emissions at these levels is an ambitious project that requires significant commitments from the general public and government. We will need to change the way we value the carbon in biomass,” said Jim Amonette.
This latter point is the key. While biochar can work, throwing it to the wolves of global carbon trading could lead to a very messy situation, full of unintended consequences.
Critics worry about plantations to produce biochar displacing forestry. Anything from 200m to one billion hectares have been suggested.
This would replace existing forest, savannah and woodlands with biochar plantations. Ironically, people who currently use these, in western terms uneconomical lands, produce hardly any green house gases (other than the deforestation that scientists say accounts for up to 20% of the global greenhouse gas emissions).
There are examples where biochar has been shown to suppress rather than improve plant growth, and also stimulate bacteria that cause other types of climate change.
But biochar can be one of the baby steps in the right direction, using farm wastes that would otherwise be costly to treat, and climate-change-causing, if left untreated.
Here in Ireland, FEASTA (the Foundation for the Economics of Sustainability) have been engaged in a Department of Environment-funded, multi-agency initiative to examine carbon cycles and sinks.
Research into biochar for arable farming has been part of this. For more on this subject, see the www.carboncyclesandsinks.org website.
