[jorgen123]

Here is a calculation done by project Drawdown. Potentially 2.5 to 4.72 gigatons CO2e reduced/sequestered over a 30 year period: https://drawdown.org/solutions/seaweed-farming

It is one of many viable solutions and humanity is working on many or most of them. We need them all. Seaweed would be great as cattle feed is one of the pathways this highlights.

[roboticmind]

It doesn't do as much as you think for cattle feed as most the high % numbers you see touted are only looking at feedlot emissions - which are only 11% of overall cattle emissions. Actual reductions are pretty small

>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/

[Springtime]

The authors' argument about the 8.8% reduction hinges on both their assumption that it wouldn't be feasible to add to cows' diets on pastures and the uncertain possibility their guts would adapt and mitigate the effectiveness.

Yet the articles they cite (which both quote the same study) describe that on a diet of 0.75% seaweed (0.25% more than the research I saw years prior) only some cattle didn't like the taste and there was an unspecified reduction in feed intake, which hardly seems the foregone conclusion the Wired authors make it out to be. While the aspect about cows' gut reactions long term is also unknown, though one of their links mentions both a 72 and 90 day trial which showed no gut adaption or reduction in effectiveness which is said to be hopeful since 'most adaptations happen within a few weeks'.

Ironically the On Pasture link Wired cites for their argument against is more neutral/optimistic and also mentions that two other more common types of seaweed reduce methane output by 20% and encouraged experimenting with for cattle diets.

[actionfromafar]

Yeah that brings me to another problem. We have too much cattle already. Also, they emit methane.