On a hot December day on a cattle farm in Western Australia, the smell of manure is hard to ignore. But not for long – as I watch, a cluster of dung beetles is hard at work and soon the cows’ manure will be buried in the soil. On a warm day it can take less than an hour for the beetles to eradicate a cowpat completely from the paddock’s surface. Other times, when the conditions are cooler and the beetles are less active, it may take up to two weeks. Either way, the insects work fastidiously until the only odour cutting through the dry summer air is the scent of eucalyptus from the giant Karri trees.

The cowpats that these particular beetles are burying are not ordinary cowpats. On this farm near Manjimup in south-west Australia, they are rich in a substance called biochar – essentially charcoal produced through a slow-bake process – that has been added to the cattle’s feed. This black, coal-like substance is leading a quiet revolution in this pocket of rural Australia, in an effort to reduce the cows’ methane emissions and to sink more carbon into the soil.

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Biochar is one way farmers are working to reduce the hotly debated environmental impact of cattle. As cows digest their food they release methane, a greenhouse gas more than 25 times more potent than carbon dioxide. The methane leaves their digestive tract at both ends – through “eructation”, better known as burping, and a small amount through flatulence. Once out of their system, their dung continues to release small quantities of methane.

There are more than 1.4 billion cattle in the world today, and together they release 65% of all greenhouse gases from livestock. Efforts to reduce the methane emissions from cows have ranged from vaccines to feeding them seaweed. There is now growing interest in whether by adding another substance to a cow’s diet methane emissions could be reduced: biochar.

This crumbly black substance is often made as a by-product of forestry and other industries. It is created when biomass is left in high-temperature, low-oxygen conditions, where it undergoes a process called pyrolysis. Long before its recent uptake in modern farming, biochar was created and added to soil by indigenous farmers in Amazonia from around the 5th Century BC, to form the rich black earth of the Amazon Basin known as “terra preta”.