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Reducing the greenhouse cost of steak

Greener beef Feeding livestock more energy-rich diets could cut greenhouse gas emissions from meat production by 23 per cent in the next two decades, according to a new paper.

The findings, reported this week in the Proceedings of the National Academy of Sciences, suggest it is possible to reduce the deforestation associated with supplying the world's growing demand for meat, says co-author Dr Mario Herrero, a researcher in food systems and the environment at Australia's CSIRO.

"A lot of people have been saying that we should stop eating meat," says Herrero. "But it's very difficult to change a consumer's attitude to what they're eating. It's a lot easier to tackle land use change."

Livestock are responsible for 12 per cent of human-related greenhouse gas emissions, mainly due to factors such as clearing of forests for pasture.

According to the Food and Agriculture Organization, the annual global demand for meat is expected to double to 470 million tonnes by 2050.

"The amount of meat that we eat is increasing in the world because people are getting richer," says Herrero, adding the hunt is on for a more sustainable way to increase meat production to the levels required.

In research funded by the CGIAR Research Program on Climate Change, Agriculture and Food Security, Herrero and colleagues report modelling that shows a system called "sustainable intensification" could reduce the amount of forest clearing involved in supplying the world with meat.

They show that by 2030, 162 million hectares of natural land could be saved if there was a shift towards this system.

Energy-rich diets

Sustainable intensification involves shifting animal from grass or straw to more energy-rich diets that include grains and other improved feeds. The system can also involve mixing livestock and crops, and feeding high-energy crop waste to livestock, says Herrero.

The more energy-efficient production of meat and milk that results from this system leads to less pressure on resources, he says.

"You produce the same amount of meat and milk with less animals, so ultimately you less land is required globally."

Herrero adds that the animals can digest their feed better and produce less methane, which is also a potent greenhouse gas.

He says most of the changes recommended by the researchers would be relevant to the developing world where there is the lowest efficiency of conversion of feed to meat and milk.

Lifecycle analysis

Stephen Wiedemann, an independent livestock researcher from FSA Consulting in Toowoomba, says he has found feeding grain strategically for a relatively short period at the end of the animal's life reduces the amount of greenhouse gasses produced per kilogram of meat.

"We found 17.5 per cent greenhouse reductions from grain feeding compared to grass feeding," says Wiedemann.

He says his study involved a lifecycle analsysis which took into account factors such as the production, transporting and milling of grain.

Wiedemann says the reduction in greenhouse emissions in his study was mainly due to the fact that the grain-fed animals had a higher growth rate and shorter life span for the same amount of beef produced.

"They achieve the same market weight but they may achieve it three, six or 12 months earlier than they would off grass," he says.

There were also lower methane emissions per kilogram of feed consumed by cattle consuming grain-based diets than those consuming grass, adds Wiedemann.

But he says in the future global scenario addressed by Herrero and colleagues, there were many external factors to consider, for example the impact of using more arable land and grains to feed ruminants rather than humans.

"You do have a challenge because there's potentially a trade off that's going to occur," says Wiedemann. "It's definitely a balancing act."

He says the approach could be viable if only a small amount of grain was used to make a big improvement in the efficiency of ruminants that are mainly eating grass on land that can't be used for anything else.