North Ronaldsay, a remote island in the Orkney archipelago off Scotland's northern shore, long ago built a flint wall to keep sheep close to the shore and away from the cows' grazing land. Since then, the sheep have adapted so well to beach life they only eat seaweed, and scientists have found they belch less methane as a result.
In a year, a cow produces about the same greenhouse effect as a car that burns 1,000 litres of petrol, so it's fairly evident how beneficial it would be to reduce livestock's carbon hoof-print simply by altering their diet. Experiments have shown that carbon dioxide as well as methane emissions are lowered when seaweed is introduced into feed. And if he succeeds in creating a nutritious seaweed blend that's palatable to ordinary livestock there would be other environmental benefits too, including being able to source more animal feed locally and sustainably.
The seaweed business was once big on North Ronaldsay and elsewhere in Scotland, so its use as food could be a commercial boon to islanders.