The next calculation starts with the world's total grain and oilseed production.
Animals eat much of both.
In 1988 in the United States, according to national statistics, cattle consumed the equivalent of 13 kg of maize to produce 1 kg of beef. Nevertheless, let us examine how many calories and grams of protein the world's grain and oilseed would furnish humanity if people ate it all rather than sharing it with farm animals or fish. To translate these quantities into calories and protein, I multiplied the weight of grain and oilseeds by the energy and protein in wheat and soybeans. If the protein in the grain and oilseeds produced in 1991 were divided among ten billion people, the average would be 86, still more than the 71 reaching people today. Clearly, if they shared the food reaching present consumers, the ten billion people would not be able to spare even the present land occupied by Nature.