What’s more, feeding cattle algae is really only practical where it’s least needed: on feedlots. This is where most cattle are crowded in the final months of their 1.5- to 2-year lives to rapidly put on weight before slaughter. There, algae feed additives can be churned into the cows’ grain and soy feed. But on feedlots, cattle already belch less methane—only 11 percent of their lifetime output

[...]

Unfortunately, adding the algae to diets on the pasture, where it’s most needed, isn’t a feasible option either. Out on grazing lands, it’s difficult to get cows to eat additives because they don’t like the taste of red algae unless it’s diluted into feed. And even if we did find ways to sneak algae in somehow, there’s a good chance their gut microbes would adapt and adjust, bringing their belches’ methane right back to high levels.

[...] All told, if we accept the most promising claims of the algae boosters, we’re talking about an 80 percent reduction of methane among only 11 percent of all burps—roughly an 8.8 percent reduction total

https://www.wired.com/story/carbon-neutral-cows-algae/

[–] semi@lemmy.ml 1 points 9 months ago* (last edited 9 months ago)

Thanks for sharing! I agree with your main point about overall emissions not changing too much since most of that reduction comes from feedlots already.

One small addition: the product that I originally linked is based on 3-nitrooxypropanol, a petrochemical-derived active ingredient, not from red algae (so there is probably a different calculation about production cost and CO2 impact than growing, processing and transporting red algae on a large scale).