Tim Flannery loves it, Malcolm Turnbull wants it on the political agenda, and ancient Amazonian cultures used it to make soil that is still fertile after hundreds of years. Why aren't we knee-deep in biochar?
Biochar is the charcoal created by burning organic waste without oxygen—a charring process that also delivers a biofuel, syngas—to produce a very stable form of carbon that can persist, unchanged, for hundreds or thousands of years.
The technology's fans point out that unlike the end-product of the still-theoretical "carbon capture" technology being proposed for coal power stations, biochar both stabilises carbon and enhances the biological cycle that humanity depends on.
Studies around the world, including in Australia, have shown that adding the char to agricultural soils can boost water and nutrient retention and crop yields, and lower nitrous oxide emissions from fertiliser by 50-80pc.
The history of biochar explains what it is and its benefits.
Hundreds, sometimes thousands of years after they were created by people living in the Amazon basin of South America, the black soils known as 'terra preta‚' are still fertile to the point that some‚ 'like the Magic Pudding‚' regenerate after being harvested for potting mix.
Part of terra preta's secret, researchers believe, is the big quantities of slow-burned charcoal that people from ancient cultures dug into these soils.
Science is trying to recreate terra preta soils, so far unsuccessfully. But it seems that some of tera preta's qualities can be recaptured using biochar.
Biochar contains valuable nutrients that help plant growth, but its primary long-term benefit lies in its complex structure that holds big quantities of nutrients, moisture and microbes in a way that is still accessible to plants.
Biochar trials on maize at NSW Department of Agriculture's Wollongbar facility found that when applied at 10 tonnes per hectare, the char tripled the biomass of wheat and doubled that of soybean, while lifting soil pH and calcium levels and reducing aluminium toxicity.
There was more soil biology in the soil containing biochar, better water retention, and less carbon dioxide and nitrous oxide emissions.
However, CSIRO soil nutrient researcher Dr Evelyn Krull warns against treating biochar as a magic bullet for either carbon sequestration or agricultural productivity.
"Malcolm Turnbull is jumping the gun here a little bit, by saying that we need to do it now. I say there is potential, but let's get the fundamentals right," he said.
The qualities of biochar differ depending on its parent material, Dr Krull said, and the effects of biochar in different soil types is still to be established.
Nor has it been established that biochar can be produced cost-effectively enough to be attractive to farmers.
On Monday's edition of the ABC’s 7.30 report, climate change campaigner and chairman of the Copehagen Climate Council, Professor Tim Flannery, questioned why the Federal government was throwing $600 million at developing coal carbon capture technology, yet failed to recognise biochar.
"You can quantify (biochar) to the nearest kilogram, you can put it in the soil and know it will stay there for thousands of years, we know it's safe and it's good for agriculture—why wouldn't we recognise that when we're happy to recognise a technology that isn't in existence yet?" Professor Flannery said.
Ironically, biochar development seems to have suffered in Australia because it has been closely associated with agriculture.
"Because we were lumped in with the agricultural sector, biochar hasn't been included in the Carbon Pollution Reduction Scheme (CPRS)," said Adriana Downie, technical manager with BEST Energies at Somersby, NSW.
"At the moment there's no motivation and no funding for anyone to research the true greenhouse accounting balance of this technology."
Using home-grown technology, BEST have developed a pilot plant that demonstrates the feasibility of biochar’s mass production from organic waste as diverse as poultry litter, nut shells and woody weeds.
Adding biochar to farm soils is ideal because it creates additional production benefits, Ms Downie said, but the product could equally be put in a hole in the ground: the primary benefit of biochar is that it creates highly stable carbon from organic matter that would otherwise decompose and return carbon dioxide to the atmosphere.
"If you can grow a forest, stablise that forest carbon into biochar, and then regrow that forest, that’s a way to really bank those stocks of carbon," Ms Downie said.
"The fact that we were lumped in with agriculture (outside the CPRS) really isn’t fair. We want to see it go into farm soils, but the policy makers have got caught up in that and are missing the big picture."
BEST will continue to develop its home-grown biochar technology, but outcomes will be “perverted” in favour of syngas, the biofuel produced during biochar production, because that part of the technology can secure carbon credits to fund ongoing research.