Though cows emit less methane when they eat red seaweed, it can only be part of the solution to cleaning up the polluting beef and dairy industry.
Cattle for milk and meat production are responsible for about 9% of global greenhouse gas emissions. Methane — a gas about 25 times more climate-damaging than CO2 but which breaks down after just a decade — is spewed into the atmosphere in large quantities each time the 1 billion cows on the planet burp and fart.
And while scientists have shown that eating less meat is a necessary step to greening the farming sector — particularly in industrialized countries, where the average person eats three times as much as in poorer ones — world leaders have mostly avoided policies to achieve this.
So the game is on to come up with climate-friendly steaks. Meat ones.
The secret, according to a study published in the journal PLOS One earlier this year, is feeding them red seaweed every day. By mixing small amounts of Asparagopsis taxiformis into the fattening feed of 20 Angus-Hereford steers, researchers at the University of California Davis, in the US, cut methane emissions by 80%.
If the environmental footprint of cattle could be cut by feeding them red seaweed, it would reduce pressure on the limited land needed to feed a growing population without damaging the atmosphere.
Seaweed influence 'massively overestimated'
Experts, however, warn that climate-neutral steaks will not be landing on dinner plates any time soon.
The influence of seaweed on the climate footprint of beef is "massively overestimated," said Matthew Hayek, assistant professor at the Department of Environmental Studies at New York University.
While cattle in the US spend most of their lives on pastures and meadows, the study looked only at cows on feedlots. "Cattle emit the most methane, over 80%, when they are on pasture and eating grass," said Hayek. During fattening, the last phase of their lives, they emit 11% of their total methane — and this is where the seaweed in the study comes into play.
Adding red seaweed to feed is a viable solution, said Hayek, "but it's a solution that's a solution to the smallest part of the problem."
Digestion is responsible for about 40 per cent of a cow's total greenhouse gas footprint. The rest comes from feed, production, transport and processing, as well as the emissions from manure. Globally, beef has a much greater environmental footprint than even other red meats because ranchers clear vast tracts of tropical rainforest to graze cattle and grow soy to feed them.
There's also a second problem: red seaweed produces bromoform, a substance found in small quantities in chlorinated drinking water and swimming pools that is extremely toxic in high doses.
Bromoforms affect brain function and can damage livers and kidneys. In earlier studies of Asparagopsis taxiformis from the Netherlands and Australia, small amounts were detected in the meat or milk of the animals, said Hanne Helene Hansen, associate professor at the Department of Veterinary and Animal Sciences at the University of Copenhagen. No matter how much is there, she said, "we certainly don't want it in our meat or milk... and we don't want it in the animals either."
In the California study, no residues of bromoform were found in the animals, suggesting there is greater potential to safely reduce costs and emissions with the feed additive. But it also raises questions about where the seaweed will come from. Asparagopsis taxiformis is mainly found in Australia.
"This would be primarily produced in coastal areas and therefore the logistical exercise would be clearly an issue," said Pekka Pesonen of Copa-Cogeca, the European umbrella organization of farmers. They would also need more information on health effects on the animals, added Pesonen, who still finds the approach promising.
Some researchers are also studying the cultivation of seagrass varieties in the northern hemisphere that do not produce bromoform.
Plant fats, the better alternative?
Red seaweed isn't the only feed additive that cleans up cow burps. Vegetable fats like rapeseed, safflower and linseed oil can also cut methane emissions.
But the potential of such oils is limited. A diet too rich in fats "reduces the feed intake" of the animals, says Alireza Bayat, senior scientist at the Natural Resources Institute in Finland. That leads to problems because cows are ruminants and, unlike pigs, cannot tolerate large amounts of fat. That means a methane reduction of 10% by adding oil can be expected "without adverse effects on animal performance."
Pesonen, from Copa-Cogeca, estimates that using mixtures of fat-containing plants in the EU could save as much methane per year in the future as about 140,000 tonnes of CO2. While that may sound like a lot, it would cut emissions from beef production in the EU by just 0.04% per year.
Researchers also found that giving animals antibiotics to increase growth or prevent disease can reduce methane production. But authorities in countries like Australia have warned against using drugs to reduce methane because they would increase the risk of pathogens resistant to antibiotics. "We've got enough problems with antibiotic resistance," said Hansen. "This is not a viable solution."
Instead of waiting for the carbon footprints of burgers to shrink as research develops, said Hansen, the top priority is to rapidly cut greenhouse gas emissions in ways scientists already understand: powering cities and transport with renewable energy, throwing away less food and eating less meat. As it stands, alternative feeds like algae and rapeseed oil can only be a small part of the solution to cutting the climate contribution of meat and milk consumption.