Rifkin provides the most comprehensive estimate, "Much of the spent CO₂ in the atmosphere comes from our highly mechanized agriculture, which uses up 12% of the energy consumed in the US. Some of the energy is used to run tractors, milking machines, reapers, and other machines. Additional energy is consumed in the use of massive amounts of petrochemical fertilisers and pesticides. Still more energy is used in marketing the produce. Modern mechanized agriculture uses more energy inputs per unit of output than any other agricultural system in history. Only 20% of the energy used in agriculture goes into growing the food. The remaining 80% is burned in processing, packaging, and distributing the produce to market. The food processing industry is now the fourth largest industrial user of energy in the United States. Some sources estimate that food processing consumes nearly 6% of the country's total energy budget."[89]

Goldsmith believes pharmers make an even bigger contribution than that suggested by rifkin, “When activities associated with farming are accounted for worldwide, agriculture is responsible for approximately one quarter of anthropogenic emissions of carbon dioxide, nearly 60% of methane and up to 80% of nitrous oxide.”[90]

"Modern animal rearing systems are even less efficient (than modern agriculture) once account is taken of the energy involved in producing artificial feeds and in building, heating, and lighting large sheds to accommodate the animals. Meat production in the industrialized world now consumes between two and three times the energy that it produces. The process of catching and producing frozen fish is probably the most inefficient form of energy use in the sphere of food production - it consumes about 20 times more energy than it makes available for human consumption. If modern agriculture comes out badly when looked at from this angle, modern food retailing makes things worse. The processing and distribution of food before it is eaten takes about three times as much energy as producing food itself. Once this is taken into account, then all food production in the industrialized world uses more energy than it creates."[91]

The brutish government’s estimate of agriculture’s contribution is much more conservative - which is about par for the course given that many mps are pharmers, “Agriculture appears not to be responsible for disproportionate CO₂ emissions as it consumes about 4.5% of u.k. energy usage, contributing less than 2% of total u.k. atmospheric Carbon emissions. Agriculture is .. responsible for a significant proportion of two other powerful greenhouse gases, nitrous oxide and methane, accounting for 17% and 32% respectively. Nitrous oxide emissions from agriculture are considered to be more damaging than its CO₂ output.”[92]