Something that I’ve never thought about is happening in New Zealand and that’s using microwaves to store carbon in charcoal.

“The application of microwaves to charcoal making is new,” says Tim Flannery of Macquarie University in Sydney, Australia, an expert on climate change and not associated with Carbonscape. “If it increases efficiency in the charcoal-making process it could prove to be a real winner.”

The plant is months away from running at full capacity, and is currently being used to produce charcoal that can be used to fertilise soil and for academic research.

The use of charcoal as a fertiliser, or “biochar”, is well known. Nearly 500 years ago, tribes in the Amazon used to smoulder their domestic waste, and the resultant charcoal was mixed into the soil. In places in the Amazon, this terra preta, or black earth, is nearly half a metre thick.

Charcoal makes the soil more fertile by binding nutrients to itself and making them available for plants, and is extremely resistant to breakdown. “You do quite often get a very significant boost in soil fertility and water holding capacity,” says Michael Bird at the University of St Andrews, UK.

“The unknowns that remain are exactly how long [the charcoal] stays in the soil. In some circumstances it can be millions of years, or decades, depending on how it is made, and soil conditions.”