There’s a chapter in the Garnaut Report that the Federal Government studiously ignored. It’s Chapter 22, on land use, the issue of biosequestration and ways in which changing our land use practices could increase our capacity to store carbon. Most of the rest of us ignored it as well, except to make jokes about Garnaut wanting us to eat more kangaroos.

But it’s the chapter that’s behind much of Malcolm Turnbull’s weekend speech on addressing climate change, where Turnbull committed — albeit in the vaguest possible terms — the Coalition to annual carbon emission reductions of 150m tonnes of CO2-equivalents.

By way of perspective, in 2006, we produced net 576m tonnes and we’re on track to produce about 660m tonnes in 2020.

How would this near-miracle be accomplished?

The Turnbull speech proposed three elements — a Green Carbon Initiative on biosequestration, energy efficiency in buildings and investment in carbon capture projects, solar, geothermal and tidal power. It’s altogether light on detail, although accelerated depreciation for green retrofitting for energy efficiency isn’t exactly new; it’s been proposed by green groups for years.

Biosequestration was Turnbull’s main focus, however. Garnaut identified a range of biosequestration options — ending land clearing (still proceeding at a rate of knots in Queensland), reducing methane emissions from sheep and cattle, better land management, restoration of mulga, and biochar.

Some of what Turnbull proposed won’t go down that well with the Nationals — particularly the bits about growing more trees — but he thinks he is on a winner with biochar.

Biochar is what you get when you cook biofuels — eg agricultural waste — without oxygen. It’s off-the-shelf technology, in the same way that fire is an off-the-shelf technology. It produces a gas or oil that can be used as a fuel source and the leftover is charcoal that can be returned to the soil, locking carbon away for at least a few hundred years or longer, and significantly improving soil productivity.

Carbon sequestration, improved productivity, fuel. Win-win-win, as one American exponent of “The Charcoal Vision” declared. Win-win-win, as Malcolm Turnbull declared, perhaps not uncoincidentally, on Saturday.

The Charcoal Vision has a lot of people very excited for just that reason. Tim Flannery has expounded its virtues. James Lovelock reckons its our only hope, although his apocalyptic tone is increasingly hard to take, especially when the economic world is ending a lot more quickly than the environmental one.

There’s a catch though — measuring what we’re doing and actually driving the rollout of appropriate processes. It might be off-the-shelf technology, but what precisely we do with biochar, and how we know what we’re doing, is the problem. The Government has left agriculture out of its ETS for exactly this reason. The inclusion of biosequestration measures in the post-Kyoto framework (Kyoto doesn’t address them) are still being negotiated. As Garnaut admits, there’s a strong element of speculation about biochar and other land use measures, because measuring how much carbon is actually being locked away is difficult without several thousand carbon inspectors touring every property in the country.

Greg Hunt, Opposition climate change spokesman, reckons the measurement issue, at least for biochar, can be easily addressed — especially compared to measuring the carbon benefits of revegetation. Hunt was the one who realised the importance of Garnaut’s land use chapter and the potential of biosequestration early. He has talked to several Australian biochar producers, including Alumina in WA, which obtained improvements in soil productivity of 25-30% in biochar demonstration projects. He is mystified as to why the Government is ignoring Garnaut, Flannery and others on the issue, given its potential benefits.

The problem with Hunt’s approach is that, while the production of biochar is measurable, as he notes, its use by farmers is much less so. Once produced, the stuff needs to be returned to the soil, not blowing around as dust or piled up somewhere. Biochar relies on not much less than a revolution in farm management involving the collection and pyrolysis of agricultural waste and the distribution of the solid product back into the soil, across every farm in the country — and the world.

Hunt says further R&D is required, although the pyrolysis process itself is relatively straightforward. The use of microwave pyrolysis — which can keep temperatures low, producing more biochar — is being tested overseas. He argues that if farmers are permitted to opt in to an ETS to obtain carbon credits, it will provide incentives for the widespread adoption of biochar.

That’s what underpins all of the Coalition’s proposals. They all need an effective ETS to provide the broader incentive framework for renewable energy and efficiency measures. Encouragement, tax breaks and demonstration projects won’t be sufficient. And without sending the Budget deeper into deficit, R&D investment needs to be sourced from ETS revenue — except that the model offered by the Government spends it all rewarding polluters and households.

To properly encourage measures like energy efficiency and changed land use practice, the ETS needs both meaningful emissions targets and funding for technology innovation. That would require the Opposition to toughen up the Government’s weak, ineffective ETS model in directions neither side want to go — higher targets, and less compensation, to provide real price signals and more research funding.

We also need a massive — and probably expensive — research effort to master land use emissions measurement. If it’s to be one of our greenhouse saviours, as Turnbull argues it should be, we need to know what exactly we are doing.