Whenever I give a talk which mentioned agricultural emissions, I get asked about the prospect of seaweed supplements as silver bullet solution to methane.

Short thread on magic seaweed.

Trials in Australia have shown potential of very dramatic reduction in methane belching from cows (20% of Ireland's CO2e) with very small supplementation of a type of seaweed. Understandably, that's caused a lot of excitement. However, we can't rely on this as a mitigation option

First, the trials relied on the supplement being mixed to dry feed. This won't work in Ireland where cows are out on grass for 10+ months of the year (it's the selling point of our beef & dairy).

Second, what is the seaweed resource required to feed the world's cattle on such a large scale? Not established.

Third, the long-term effects of the supplement on cow health, food quality and long-term emissions is not established. The rumen could adapt.

Ultimately, when a silver bullet is proposed as the answer, you have to first ask what is the question? Even if magic seaweed could be used to reduce CH4 emissions there are many other aspects of environmental sustainability which it wouldn't address, like excess nitrogen.

There is research ongoing in Ireland, which is great, but relying on the prospect of feed supplements to reduce CH4 is like relying on cheap nuclear fusion being available before 2030 to solve energy emissions. It delays meaningful action.