Waste not

Biofuels can be bad for the environment, but better options from wood waste could be on the horizon.

- Andrea Graves

King Charles has an Aston Martin that runs on surplus wine and whey, he told the BBC in 2021. It's one of K his efforts to reduce his carbon emissions. "The risks are so great," he said of the ever-escalating concentration of carbon dioxide in the atmosphere.

Wine and whey can be turned into biofuel, which can replace fuels made from fossil oil. When biofuels are burnt for energy, the carbon released is the same stuff they sequestered from the atmosphere as they grew.

This allure prompted the government's Sustainable Biofuel Obligation Bill, which was scrapped in February by Prime Minister Chris Hipkins.

The King's set-up is boutique, but the local proposal was to produce or import biofuel to comprise a percentage of fuel bought at the pump, as is required in Europe and the US.

Our currently available biofuels are food crops, ethanol, from fermented, and biodiesel, created by refining vegetable oil or animal fat.

The trouble with using plants as socalled "feedstocks" for biofuel is that people or livestock could otherwise eat them. Waste oil and fat with no other use are scarce. An alternative feedstock is forestry waste, but the cellulose and lignin that stiffen trees make that technically much trickier.