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Could we nourish an additional 3.5 billion people if we just ate the stuff we feed to animals?

In a popular YouTube video titled "Why Meat is the Best Worst Thing in the World 🍔" by the channel Kurzgesagt, they claim:

According to projections, we could nourish an additional 3.5 billion people if we just ate the stuff we feed to animals.

The source for information is a research paper titled: Redefining agricultural yields: from tonnes to people nourished per hectare, from which there is this example:

China feeds more people than India per cropland hectare with 8.4 people fed with delivered calories, albeit with a lower calorie delivery fraction of 62%. If all produced calories were food, that number would rise substantially to 13.5 people ha-1.

What I can't get my head around is the graph they have:

Calories lost

Maize and its fatty germs, have the biggest losses, but they are more suitable for digestion by ruminants. For us, we get little to no fat from maize, and compared to soybeans (which need more specific climates unlike maize), half the calories, and one-tenth the protein, for the same weight.

Are the projections correct (when we consider the different digestive systems)? Would using the same exact crops meant for animals (mostly maize) to feed humans really nourish an additional 3.5 billion people?

For example, we can produce corn oil for cooking: an industrial process that introduces inefficiencies, and after the oil is used for cooking, most of it is discarded. Since we can't break down maize directly like ruminants, wouldn't this skew the most directly consumable calories (by humans) per hectare?

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    Round here farm animals eat grass. In my old home of upland Yorkshire there were areas where nothing would grow but grass. Humans cannot live on grass.
    – RedSonja
    Aug 10 '19 at 18:41
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    @RedSonja But the vast majority of modern commercial farming does not use grass, they use manufactured feeds from things like (usually imported) maize, soya and sometimes food waste, so that the meat producers can produce more in a much smaller area. That's the point.
    – user56reinstatemonica8
    Aug 11 '19 at 12:00
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    C'mon kids, eat your plate of delicious cotton! When that's the first line of the graph, I'm not sure what to think.
    – Roger
    Aug 13 '19 at 14:24
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    @Roger cotton seed oil is a common cooking oil and food additive.
    – John
    Aug 20 '19 at 17:04
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    Note food waste is going to be added in to that calculation, becasue the initial study is about site production vs food eaten. Waste is huge, some estimates around 1/3rd of all food produced for human consumption. That will get you most of the way there just by itself. That they make no mention of this in their calculation makes their conclusions questionable at best.
    – John
    Aug 20 '19 at 17:14
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The claim quoted from the video is an over-simplification of a complex question.

If I understand the following correctly, the article you provide by Cassidy et al. directly acknowledges that even increasing the availability of calories to feed 1 billion people, purely by shifting currently produced human-edible crops away from animal or industrial use, is unlikely to work in practice.

Grassy forage crops and crop residues were not accounted for in this study and would change the livestock conversion efficiencies. A conclusion that could be made from our findings is that without large amounts of supplementation from grasses and crop residues, we are able to produce 41% (4.11 × 1014 calories) of total livestock production (1.01 × 1015 calories). We caution that this is unrealistic. This study separates human-edible crops from other forages due to data limitations, but this split is hypothetical. Livestock production requires a mix of grassy forages, crop residues and human-edible feed crops.

The highest number quoted in that article, 4 billion additional people, is therefore best understood as an upper bound to what we might conceivably feed on the basis of current cropland extents and yields if animal production, biofuel production, etc. was eliminated. This is not the same thing as saying that we could feed 4 billion more people tomorrow based on the same food system by diverting current supplies of animal feed to human consumption.

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  • Something that should be noted is the amount of food crops grown that go to produce things other then food (think corn and ethanol) and the amount of crop bearing land that sits idle every year in order to help control prices by limiting the supply.
    – Joe W
    Aug 11 '19 at 23:43
  • Another thing that should be noted is the quality of the crop - farm animals tend to be fed low-grade grain, even when it is the same type of grain used for human consumption. This doesn't mean it's bad or inedible, but it does go through significantly fewer regulations for consumption.
    – Zibbobz
    Aug 16 '19 at 15:03
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    @Zibbobz In the USA, it's called commodity grade goods. It's illegal to use in human foods. In general, it's considered substandard, therefore not fit for human consumption.
    – fredsbend ♦
    Aug 16 '19 at 16:33

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