Yes, this is a realistic solution to combat global warming, but it is not the only one. We need to come up with as many solutions as possible because it is such a major issue. We need to do everything we possibly can, and if feeding seaweed helps, we should do it.
As the world’s nations continue to miss their carbon reduction targets and the quest by scientists for new forms of effective and consistent clean energy sources are being frustrated, it is important to reduce greenhouse gases using any means possible. The methane produced by cows forms a considerable bulk of the greenhouse gases in our atmosphere and reducing them by any means is a good step forward.
Feeding cows seaweed to reduce methane production may be one small solution toward combating global warming. First, it would have to be determined safe for the cows, since seaweed is not a natural food for these animals. Then, it would have to be determined useful. Any small step toward solving this huge problem would be great.
If year you feed cows seaweed, you are going to radically change how they taste. Most likely, you are going to make them taste much, much worse. Nobody will eat the meat, and so a whole bunch of cows will have been raised and slaughtered for no reason whatsoever
Oh into the idea that cows are somehow massively contributing to global warming is, of course, completely stupid. It's like you think that massive herds of ungulates never existed before 1850.
While changing the diet of cows to produce less methane would be an improvement in the right direction, it is not a drastic enough solution to combat global warming. Methane is an important aspect of global warming, but it is not the only factor. Fossil fuels are one of the top contributors to global warming and greenhouse gases, and replacing fossil fuels with clean energy could make a much larger impact on our carbon footprint than reducing methane from the cow population alone. While feeding seaweed to cows may reduce the amount of methane produced, it is not a large enough solution to combat global warming on a worldwide scale.