In the dairy sector, the environmental challenge begins right at source. Cows can produce up to 600 litres of methane each day, most of which they expel into the atmosphere. Over the course of a year, that adds up to some 150kg per cow, or 1% of the UK’s greenhouse gas (GHG) emissions for the whole dairy herd. To put that in context, transport contributes over 24%.

Methane is a by-product of the enteric fermentation of grass, forage and other feed in the cow’s rumen – the largest of its four stomachs. This is an entirely natural process, and the gas produced is part of the short-term 20-year carbon cycle. But, since methane has 21 times the warming potential of CO2, it is a concern for the dairy industry.

A combination of science and good husbandry is being deployed to cut these cow emissions. The race is already on to find ways of feeding cows exactly the right mix of nutrients in the right form. And better breeding continues to push up cow productivity, reducing emissions per litre of milk.

Results vary, but research suggests that getting both the diet and the genetics right can cut methane emissions per litre of milk produced by at least 20%.