With the recent dramatic collapse of the ice bridge to the Wilkins Ice Shelf in Antarctica, climate change is back in the headlines.

But Malcolm Turnbull and Coalition environment spokesman Greg Hunt think they have an answer: biochar. Many of the world’s top climate scientists, including James Hansen, agree with them.

So what exactly is biochar? Will it work, and can it save us?

Essentially, biochar is charcoal — the burnt remains of organic material. The CSIRO has published a handy fact-sheet which explains that biochar is "a type of charcoal which results from the thermal treatment (heating) of natural organic materials (eg crop waste, wood chip, municipal waste, or manure) in an oxygen-limited environment. This process is referred to as pyrolysis."

The pyrolysis is the important part. Merely burning organic matter on a big bonfire won’t give you biochar; limited oxygen and very high temperatures are required.

What biochar can do is sequester carbon. By turning typical organic molecules into carbon-containing aromatic rings, pyrolysis has the potential to be "carbon negative". This means the process can actually take up more carbon than it gives out, potentially reducing the amount of carbon in the atmosphere. It’s the holy grail of climate change mitigation. No wonder Tim Flannery is into it.

But will it work? Proponents point to native Amazonian slash-and-burn farming practices, which appear to have produced the dark soils called terra preta that remain rich in soil carbon for thousands of years. Biochar can be produced quite easily using current technologies, and small-scale pyrolysis systems for use on farms are commercially available: the NSW Department of Primary Industries is researching a pilot biochar reactor in Gosford. Indeed, one of the biggest benefits of biochar might be to help subsistence agriculture in developing nations, for example in Central America.

But much research remains to be done. Dr Evelyn Krull, the author of the CSIRO’s biochar fact sheet, told the ABC’s Anna Salleh that it will take three to five years before CSIRO can recommend it to farmers. "What we don’t know is what the safe upper limits of biochar applications are for different soil types," she told Salleh.

And, as with nearly all renewable energy technologies, there is the problem of scale. There is a vast difference between small-scale research plants and the kind of large-scale, industry-wide solutions that can make a difference to climate change. One of biochar’s chief proponents, Cornell University’s Johannes Lehmann, admits that the big question about biochar is "whether this approach can be scaled up to national and regional, or even global, scales."

The CSIRO’s Evelyn Krull appears to agree, telling the ABC that estimates on how much carbon can actually be trapped using biochar are rubbery, at best. "I don’t know where these numbers come from," she said.

One source of these optimistic figures is a 2009 paper by UK meteorologist Tim Lenton (based on work by Lehmann), which estimated that biochar technology might be able to sequester as much as 0.56 gigatonnes of carbon a year, globally. This really would make a big impact. At the moment, though, it’s only a figure in a scientific paper.

So can biochar save us? Probably not. As George Monbiot has pointed out in The Guardian, the biggest problem with the biochar campaign may well be its allure as a miracle solution to global warming.

This has been a common human response to gigantic problems that threaten to overwhelm us. Ever since the Reverend Thomas Malthus wrote his gloomy tome An Essay on the Principle of Population, the standard retort of pragmatic conservatives and Panglossian optimists has been that humanity’s ingenuity will enable us to innovate our way out of ecological disasters. The "game-changing" ability of technological innovation has indeed been a key factor in saving the world from starvation since Malthus’ time — but at the cost of significant environmental degradation in many parts of the globe.

In the 1970s, we saw a re-run of the Malthusian debate with the publication of the Club of Rome’s groundbreaking report, The Limits to Growth. Authored by a group of analysts from MIT, The Limits to Growth famously predicted that global ecosystems would eventually be overwhelmed by a "business-as-usual" approach to economic growth. It foreshadowed the depletion and exhaustion of crucial energy resources, and the "overshoot and collapse" of global population. Enjoying blockbuster sales at the time, the survey soon attracted strong criticism from economists such as Julian Simon, and has often been dismissed by skeptical optimists like Bjorn Lomborg as a case-study in the perils of doom-laden prediction.

Unfortunately, the Cassandras are looking more prescient than the Panglossians just now. A recent research paper by the CSIRO’s Graham Turner looked at the projections of The Limits to Growth 30 years on, in the light of three decades of accumulated data. He found that the Club of Rome’s business-as-usual (or "standard run") model was surprisingly accurate, giving essentially correct figures for things like global population, non-renewable resource depletion and global pollution.

One of the key criticisms of the Club of Rome’s models was that technological innovation would solve many of the resource constraints it predicted. So far, this hasn’t happened with fossil fuels like oil. Likewise, a series of renewable energy technologies have been mooted as the saviour of the global economy and environment. First it was solar energy. Then wind. Then more exotic renewables like geothermal and tidal power. And finally the mirage of "clean coal", or Carbon Capture and Sequestration, motivated governments and politicians (including in Australia) to invest billions in the hope of allowing humanity to burn dead trees forever. Time and again, commercial realities, political complacency and vested interests have defeated the promise of renewable energy industries. Biochar is, in this sense, simply the latest in the long line of such false dawns.

None of this is to say we shouldn’t pursue biochar technology. As Chris Goodall wrote in The Guardian in response to Monbiot, "yes, we don’t yet understand fully why biochar works but this is not an argument to ignore it or rule it out."

Clearly, if we are to seriously address the global crisis of anthropogenic global warming, we need every shot in the technological armoury. But biochar will never be enough. If we are to stave off ecological catastrophe this century, we are going to have to stop burning carbon.