No, Really, Can We Grow Enough Seaweed to Help Cows Fight Climate Change?

I enjoyed a recent Civil Eats feature by Gosia Wozniacka, headlined “Can We Grow Enough Seaweed to Help Cows Fight Climate Change?” Wozniacka investigates the possibility of reducing methane emissions from cattle production by feeding cows seaweed, which have compounds shown to suppress enteric fermentation. It’s a compelling example of innovation driving improved environmental outcomes.

I would nitpick, though, by observing that Wozniacka doesn’t fully consider the question of her headline. What amount of seaweed production would be “enough” to meaningfully reduce carbon emissions? What scale of solution are we talking about here?

There are good reasons to avoid conversations about scale. We can’t predict the future. Plenty of technologies defied initial skepticism: think personal computers, or fracking. Seaweed feed might really take off, or it might not. What journalists and advocates might most appropriately be interested in are precisely the things Wozniacka discusses: the practices and goals of people working on the problem today. 

Still, if we never work through the scale implications of different environmental solutions, we risk emphasizing solutions that are out of proportion to the problems we aim to address. On the seaweed question in particular, I did some quick math for the United States. Assuming 10,000 pounds of feed per cattle per year and that seaweed supplement amounts to 1% of total feed volume, I got:

(My math is intentionally slapdash and approximate here. I’m not trying to get a precise estimate — that would be futile and impossible — but rather to get a sense of scale.)

4.5 million tons of seaweed, just for use in US cattle production. Considering the United States consumes less than 50,000 tons of commercial seaweed today, that implies a rather significant increase in cultivation and wild harvest, a significant increase in imports, or all of the above. On its face, it sounds feasible, if ambitious, to me. Growing more seaweed in marine environs or intensive aquaponics systems certainly seems plausible. But this first-order concern is elided in most of the writing I’ve seen on the subject. 

This brings me to a question for all of us thinking, working, and writing on solutions to address global environmental challenges like climate change: does it scale? So much of what passes for environmental stewardship fails this test. For instance, last year I wrote about the pitfalls of “plastic straw environmentalism.” Foregoing or replacing plastic straws with metal or paper alternatives might be fine, but it is a minuscule gesture compared to the scale of aggregate plastic pollution. Such a gesture might indeed bring more attention to a problem or motivate significant action elsewhere. Or, more likely in my view, it might indulge our impulse to address the problem without materially changing much of anything. 

Feeding cows seaweed does seem to offer real and potentially significant environmental benefits, not least because it’s on the higher-leverage production side of the equation as opposed to the consumption side. But we still need to understand the scale of the challenge. How large a share of global emissions is cattle production responsible for? What are the options for reducing these impacts? What would be required by these options, and what new impacts would they create? 

I am by no means immune from the challenges created by considering scale. I have written frequently, for instance, about the climate imperative of keeping existing nuclear plants operating, which is, indeed, an obviously cost-effective and common-sense way to prevent increasing carbon emissions. But it should not go unsaid that existing nuclear power plants account for only about 10% of global electricity generation, and about 4.5% of global primary energy production. Keeping nuclear plants operating is a good idea, but one reason Breakthrough focuses so much on advanced reactors simply comes back to scale. We need to understand the role that existing nuclear plays within deep decarbonization, and the roles it doesn’t. 

People often get around talking about the scale of a challenge by using relative terms to describe growth trends. Take this Good Food Institute infographic on fake meat from Inverse:


10% growth in plant-based meats, like those from Impossible Foods and Beyond Meat, is certainly a good sign; my colleague Dan Blaustein-Rejto has
written before about the environmental mitigation potential of these products. But these percentages are somewhat meaningless without attaching absolute values to them. Doing so would reveal that, according to recent figures, plant-based meat accounts for less than 1% of the global meat market.  

I am a fan of the Good Food Institute and am hopeful that plant-based and lab-based meats can make a big dent in the environmental impacts of meat production over the coming decades. But to do so, they’ll need to make a difference in physical scale, not arithmetic. 

Otherwise, we can easily fall into the trap of extrapolating nominal growth rates to anticipate trends into the future. For instance, in a recent article in his “Solar Singularity” series at Greentech Media, Tam Hunt writes, "If we continue at 25 percent annual [solar energy] growth for the next decade, we get to 273 percent of U.S. 2018 electricity demand by 2030.” This is, indeed, how math works. But solar growth rates have been reliably trending downwards for years, even as absolute capacity has grown, as is pretty much always the case with new technologies. (Software and computing power are a slightly different story, which is one reason to be skeptical of comparisons between things like Moore’s Law and energy technology deployment.) Actual sustained deployment of solar energy will depend on the cheapness of the solar technologies themselves, the penetration at different grid levels, the composition of other generation and electricity storage capacity, the availability of land, transmission infrastructure, and other considerations. 

None of this is to say that seaweed, existing nuclear, fake meat, or solar have little or no environmental promise. And I don’t mean to be too critical of the style of journalism or advocacy that spotlight exciting, if very early-stage, innovations. Indeed, I decided to dwell on these technologies precisely because I am personally optimistic about all of them. And of course, if we set the bar for scalability so high that no one solution could possibly clear it, then we are making a similar mistake in the opposite direction. 

But there exists a spectrum between solution fetishism and let-a-thousand-flowers-bloom solutionism. In the former, one approach is expected to do all the work: solar, or nuclear, or fake meat, or whatever, will solve an environmental problem almost single-handedly. The latter is, if anything, more admirable, but treating all solutions as equally valuable sacrifices any discussion of strategy and prioritization. It is in between these two extremes that an evidence-based conversation about scale must take place.