This similar study by the same authors seems a bit more reasonable. https://iapreview.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=323593 htt

This similar study by the same authors seems a bit more reasonable. https://iapreview.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=323593 https://iapreview.ars.usda.gov/research/publications/publica... > Despite greater total availability of energy, a feasible solution could not be identified, meaning that the yearly nutrient requirements of the U.S. population could not be met under the defined constraints. Deficiencies in vitamins (A, D, E, B12, and choline) and minerals (Ca) were the primary cause of this infeasibility. Although eliminating animals from the food production system may seem advantageous based on surface-level comparisons of system energetics, a more comprehensive analysis of the food production system highlights the unique and essential role of livestock products in the food production system. This suggests that substantial gains in environmental impact could be made by simply reducing daily intake, rather than affecting dramatic shifts in consumption pattern. Two animal scientists had a silly hypothesis "is it a good idea to remove all farm animals", and proved the answer to be no. Too bad they don't provide access to these studies. To me it looks like they just left it at that, and didn't investigate any further, e. g. the question of how many farm animals could be removed while still meeting all dietary requirements.