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The Next Green Thing: Seaweed

Did you know that feeding seaweed to cattle and sheep can significantly cut the emissions of the greenhouse gas methane – a by-product of the animals’ burping? Nick Hughes explains…

Hang on a minute, I’ve been ordering crispy seaweed for years in my Chinese takeaway…..Actually, you’ve probably been eating deep-fried spring greens, although in any case we’re not talking about humans but animals.

 Ok, tell me more…..Researchers in Australia and the USA have been feeding a red seaweed, asparagopsis taxiformis, to ruminant livestock. They have found that it virtually eliminates methane emissions in cattle and sheep when it’s fed as a dietary additive in low doses.

That sounds like a big deal….It is, potentially. Livestock are responsible for around 15% of global greenhouse gas emissions, according to the Food and Agriculture Organisation (FAO), and methane – released by burping cattle and sheep – is one of the key culprits. As a greenhouse gas, methane is 28 times more potent than carbon dioxide (CO2) over a 100-year timeframe and ruminants are responsible for around a third of all anthropogenic methane in the atmosphere. Feeding seaweed to cattle and sheep could reduce that significantly. In short-term studies, US researchers at Penn State University found that using seaweed as a feed supplement for lactating dairy cows decreased methane emissions by 80%. Similar results have been found in studies on cattle and sheep in Australia, according to the country’s national science agency CSIRO.

So how does it work? In short, the metabolites in the seaweed disrupt the enzymes that are responsible for producing methane in the stomachs of cattle and sheep.

If this is so effective why aren’t we feeding seaweed to all livestock? Experts believe the seaweed could be commercialised in as little as two years, but the extent to which it provides a solution at scale is debateable. Alexander Hristov, professor of dairy nutrition at Penn State University, told that for seaweed feed to make a difference globally, the scale of production would have to be immense, adding that with nearly 1.5 billion head of cattle in the world, harvesting enough wild seaweed to add to their feed would be impossible. There are also concerns around how to get the daily seaweed dose required into cows that graze over large areas of grassland, while there is fierce disagreement over the extent to which methane from livestock is a problem at all, with critics arguing that methane’s relatively short atmospheric life span makes it a far less damaging greenhouse gas than carbon dioxide.

So just to confirm, there’s no need for me to add actual seaweed to my diet anytime soon? Not so fast. In fact, algae – which includes seaweeds – is increasingly being recognised as a nutrient-rich alternative food source for humans. In their recent report highlighting 50 “future foods” we should be eating for their health and sustainability credentials, Knorr and WWF included two seaweeds: laver seaweed that is known for its link to Japanese cuisine, and wakame seaweed that has been cultivated for centuries by sea farmers in Korea and Japan and is one of the few plant-based sources of the omega-3 fatty acid EPA (eicosapentaenoic acid), which is found almost exclusively in fatty fish.

Whether eating either will help guard against embarrassing wind is another question entirely.