Seaweed shown to reduce 99% methane from cattle

Welcome for Canadian and Australian studies that also show healthier, more fertile cattle

News that a slight dietary change could dramatically reduce the amount of environmentally harmful methane gas released by cattle has been given an enthusiastic welcome by Irish farmers.

Researchers at James Cook University in Queensland, Australia, found the addition of less than 2 per cent dried seaweed to a cow’s diet could reduce their methane emissions by as much as 99 per cent.

The study builds on the experience of a Canadian farmer who discovered in 2012 that cattle eating wind-blown seaweed were not just more healthy than others, but enjoyed a longer mating cycle. Researchers Rob Kinley and Alan Fredeen subsequently confirmed the results as well as finding seaweeds and similar plants reduced methane emissions.

This was further substantiated by the Australian study, which was led by Prof of Aquaculture Rocky De Nys in collaboration with the Commonwealth Scientific and Industrial Research Organisation.


Agriculture and transport are the largest contributors to Ireland’s climate change emissions and there have long been suggestions that the population should eat fewer burgers and steaks in an effort to reduce cattle numbers and protect the environment.

The gas is released via burps and flatulence by the estimated 1.5 billion cows as a byproduct of their biology. Cows, with the help of stomach bacteria, digest their food through a process called enteric fermentation, which allows them to live on a cellulose-heavy diet of grass.


The end result of their digestive habits is the daily leakage of some 200 to 500 litres of methane, which is about 25-times more harmful to the atmosphere than carbon dioxide over a 100-year time span.

The Irish Farmers’ Association gave a broad welcome to the study saying the research provides the opportunity to continue to build on Ireland’s “sustainable grass-based model of food production”.

The association’s environment chairman, Thomas Cooney, called on Irish researchers “to immediately investigate the potential for this research in an Irish agriculture context, and in the context of the opportunity that may exist for indigenous seaweed production”.

Ireland has a long tradition of harvesting seaweed, much of it by hand to help fertilise small holdings where the land is poor in nutrients. Frequently known as dulse or dillisk along the west coast, seaweed has long been regarded for its health-giving properties.

Tim O'Brien

Tim O'Brien

Tim O'Brien is an Irish Times journalist