Want Carbon-Neutral Cows? Algae Isn’t the Answer


Recent technological breakthroughs have us feeling hopeful about a green future. We have affordable electric cars, relatively cheap and efficient solar power, and even robots that might be able to remove plastic from the oceans. You might think then, that it shouldn’t be too hard to finally do something about cows belching methane into our atmosphere. The livestock industry, its allies in the scientific community, and its corporate partners like Burger King are aspiring toward carbon-neutral cows. And recently, many of them are clinging to seaweed as the hamburger’s saving grace.

This year, the world’s farms will churn out about 72 million tons of beef. Cattle production makes up about 6 percent of all greenhouse gas emissions, which is incompatible with keeping global warming under reasonable limits of 1.5 or 2 C. Our global appetite is fast turning into a massive environmental problem. But could a quick-fix cattle feed in the form Asparagopsis taxiformis, a red algae from tropical oceans, really offer redemption for climate-conscious burger lovers?

In recent studies, adding seaweed to cattle feed has shown promise in suppressing bovine methane. Some trials have achieved seemingly game-changing 80 percent reductions. Perhaps, instead of going vegan or embracing plant-based burgers, we can just feed cows algae and get on with it. Or so the thinking goes. This glimmer of hope has allowed algae to make headlines, startups to win millions of dollars in funding, and fast-food chains to say that their beef is going green. But do all these claims really hold up under scrutiny? Unfortunately not.

The truth is that the benefits of seaweed are likely far more limited, both in its capacity to reduce cows’ methane emissions and its potential to scale up to the size of the problem. Many of the claims about the technology’s promise are based on small-scale tests—to actually have a meaningful impact, we’d have to find a way to cater algae to most of the world’s 1.5 billion cows, including 100 million in the US alone.

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. That’s because most of their methane comes from their gut microbes breaking down the indigestible grass, leaves, and roughage they eat on the pastures beforehand, and not from feedlot corn and soy. This means that even if algae diets on feedlots worked perfectly, it wouldn’t help with the 89 percent of cows’ belches that occur earlier in their lives.

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. Maybe a little more if we can work algae into cows’ diets on pastures. And that would only really count as a serious climate change mitigation strategy if we could find a way to change the diets of hundreds of millions of cows. This is not only a major logistical and economic challenge, it might also pose its own issues since we’d have to contend with the potential ecological impact of large-scale algae farming, be it in the wild or in aquaculture operations.

And there’s another problem. Although cow belches are the largest source of agricultural methane, beef and dairy production involve lots of other climate emissions, from their manure to the fertilizer sprayed on their crops and grasses, through to the transport of the animals and later the meat. While there may be technological solutions to all of these different emissions in a cow’s life cycle, algae is far from the silver bullet that can solve all of them.

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