I still think that there is a simple explanation for the 'reduction in methane' effect, and that the plan has some severe loopholes<p>Raising cattle in a regular diet of seaweed for its entire life and expecting it to grow correctly is still uncharted territory. Are we pushing cow metabolism to the brink of famine?<p>Wild seaweeds are harvested and sold for several purposes:<p>1) To make agar-agar. A substance that is used (among other purposes) as a gut filler without calories in slimming diets and treatments for obesity.<p>2) As source of medical compounds. Seaweed, specially the red ones, have evolved a battery of chemical weapons to survive its many grazers. They are used to make antibiotics<p>So, the lack of methane emission... is maybe because the gut microorganisms that released methane have been killed after giving the cattle a cocktail of antibiotics?.<p>The problem is that cattle needs special gut microorganisms for surviving. They can not process cellulose into sugar without it. How can be (competitively) raised a cow that can not eat plants anymore? In a diet of fish or meat?<p>This is a serious point that should be explored, in my opinion. If this cows don't grow muscle fast enough (and will produce milk with a funny flavor), all the project is doomed from the start.<p>On the other hand there is an environmental impact to take in mind, seaweed is related with fisheries and marine production. Kelp grows really fast, but I had seen experiments removing other species of brown seaweed in some tidal rocks and it seems that it takes decades to return.<p>As seaweed has an economical value, either the farmers buy it at a higher price, or import if from the country that cultures million tons of seaweed each year (China). They could have problems to assure enough cheap seaweed for the cattle.<p>The cow meat raised in seaweed would be more expensive and with more waste and fuel consumption. Would increase also the dependency of third countries and external policies (that sometimes are not specially nature friendly), and wouldn't be so much sustainable as we think.