Note from February 9, 2020: I’ve redone this analysis for the forthcoming non-fiction book, The Future without Animal Products. The new analysis is stronger and more correct than what’s shared originally on this post. That said, this post is still highly useful.
The animal agriculture industry has pursued creative paths to increase the productivity of their process. The industry breeds chickens and turkeys with such large breasts that they can’t walk or have sex. Cows are fatter and eat more. If you seek even more examples, I suggest Jonathan Safran Foer’s Eating Animals. It documents many ignominious ways in which breeders have attempted to boost productivity (e.g. getting hens to lay more eggs, cramming animals in tight space). Despite the lengths taken, animals are still fundamentally limited in productivity compared to prospective competitors (e.g. plants, yeast). I discuss the limits of animal-based productivity in this Animals by the Numbers post.
Productivity is how much product generated per time. Even though much input for meat is cheap (e.g. grass, corn, water), the producers pay dearly with time. A chicken requires about half a year to become full size; a cow requires almost 4 years . Productivity keeps the meat producers up at night and the breeders at work. So how does productivity relate to the biological substrate, in this case, the animal? Productivity equates to how fast an animal grows. Intuitively, this makes sense. Assuming all adult cows are the same size, if it takes Breed A five years to reach adulthood versus Breed B taking seven years, then Breed A is the more productive choice. Even if the Breed A eats way more grass to reach the same mass (sacrificing yield), I suspect most meat producers would prefer A.
As explained earlier, meat comes from the animal biomass. The purpose of growing animals is to generate biomass. Biomass productivity has another name in the biochemical engineering space, growth rate. And as you probably surmise, growth rates have been quantified for many domains of life, particularly microorganisms. Quantifying growth rate for animals is somewhat tricky because they follow the ontogenetic model, where they grow mostly in the adolescence and cease as adults. To get around this, we can consider the maximum growth rate (biomass productivity), or the fastest that a given organism will grow. I’ve derived such a metric for ontogenetically growing organisms. You can find that on the Github. So what do those numbers look like?
To give you a sense of how fast bacteria grow (~1 per h): If you could feed bacteria unlimited nutrients and sustain the optimal conditions, a single bacterium (665 femtograms) would generate biomass equivalent to Earth’s total mass in just 4 days. In contrast, if you could do the same with cows, it would take more than 100 years. (Again, I’m assuming one can always have the cows growing maximally. )
A subtle casualty of the terrible animal-based productivity is land usage. Animal agriculture has capitalized much of our terrestrial, ice-free surface. Specifically, a whopping 30% of such land is used for animal agriculture . The explanation is simple. There is a lot of demand for animal products. To meet such demand, producers employed contemptible ways to increase productivity. That alone wasn’t enough. To counter the still terrible productivity, the producers expanded the enterprise. If you have a slow process, just make the process bigger!
Therefore, we should acknowledge the tremendous opportunity cost to producing animal-based goods. It’s not just the copious CO2 that the animal-industry generates (~18% of emissions) . We also must note all the lost and putative forests that could be drawing back CO2. Without animal agriculture, we’d almost certainly have more trees/forests. Switching to a more productive biological substrate (e.g. yeast), would free the same fold of equivalent land. For instance, if yeast replaced cows for products, we’d free up +99.9% of the land from the tendrils of the cow agriculture behemoth.
Animal agriculture fixates on productivity, and the consequences have devastated moral and environmental realms. Growth rates (biomass productivity) of other organisms portend dramatically improved productivity, when we switch substrates for our products.
- This analysis particularly extols in vitro meat, or meat grown from animal stem cells in bioreactors. They will decimate old school animal agriculture in the productivity metric. I calculate that they would be at least 100 times more productive.
- This analysis particularly castigates tree-based goods (e.g. chestnuts, almonds). Trees-based products are not productive. Before the calculations, I figured nuts would fall short. I’m even more disappointed now.
- You may be wondering if one can modify/engineer a cow to be more productive. No, physics imposes certain limits. Can read more here.
- Productivity – The rate of product generated. How fast we can make something.
- Growth rate – A metric equivalent to the productivity of biological entities.
 G. B. West, J. H. Brown, and B. J. Enquist, ‘A General Model for Ontogenetic Growth’, Nature, 413.6856 (2001), 628–31
 P. K. Thornton and M. Herrero, “Potential for reduced methane and carbon dioxide emissions from livestock and pasture management in the tropics,” Proc. Natl. Acad. Sci. U. S. A., vol. 107, no. 46, pp. 19667–19672, Nov. 2010.