THE hype surrounding the potential of biochar as a soil health resuscitator and crop yield booster may be justified but as the science stands at the moment not warranted.
Its inclusion on the positive list for the Carbon Farming Initiative before adequate research and field trials were undertaken fuelled this situation.
The January issue of Australian Farm Journal investigates the science behind claims being made about biochar and finds its potential is not as clear as many advocates make it out to be.
To start with senior CSIRO research scientist Dr Evelyn Krull says the term biochar is misleading “because there is no such thing as biochar per se”. She says the word should be used in the plural.
“We probably have to think about adding something that qualifies it, like either ‘low-temperature biochar’ or ‘wood-based biochar’ or ‘manure-based biochar’.
“We know that, for example, if you take a biochar – that’s produced at let’s say 400 degrees from poultry litter – it may not have a residence time that classifies it as permanent under the Carbon Farming Initiative or the carbon protocol. Because it has to be stable over 100 years. These sorts of biochars have so many nutrients and minerals and don’t have that much of a connected structure that they actually may degrade quicker, or much of it degrades quicker.
“Compare it to biochar produced from oil mallee at 500 degrees, [where] you’re talking about residence times of most of this biochar of thousands of years,” says Dr Krull.
So it’s misleading to say that biochar is stable, biochar can increase crop productivity, or biochar can decrease nitrous oxide emissions because biochar properties vary.
“We know some biochars don’t increase crop productivity, some biochars can actually decrease crop productivity, and some biochars only work in certain soil types,” says Dr Krull. “Under certain conditions biochars do not decrease nitrous oxide emissions. We have to be very careful how we communicate our findings to the general public.”
Inclusion of biochar of any denomination on the Carbon Farming Initiative positive list has most likely heightened farmer and agribusiness interest in the product.
In the February 2012 issue Australian Farm Journal talks to three biochar based agribusinesses, two of which import the product from Indonesia and China and one manufactures it in Australia.
At depot prices which equate to $650 - $800 per tonne CO2e the businesses are realistic about its likely uses in Australia and it’s not in broadacre agriculture as a soil ameliorant on its own, even with a potential $25 per tonne CO2e Australian Carbon Credit Unit price tag.
If you are trying to understand the potential for biochar in broadacre agriculture, don’t miss this series of articles. Part 1 is in January Australian Farm Journal out now in newsagents around Australia, or ring 1300 131 095 for a copy.
Patrick Francis is the editor of Australian Farm Journal
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