||Gidon Eshel and Pamela Martin, Diet, Energy and Global Warming, Earth Interactions, Vol. 10, pp. 1-17, March 2006 link p.2 3rd paragraph
||U.S. Department of Energy, 2004a: Annual energy review 2003. Rep. DOE/EIA-0384(2003), Energy Information Administration, 390 pp.
||P.2 3rd paragraph: "In 1999, Heller and Keoleian (2000) estimated the total energy used in food production (defined here as agricultural production combined with processing and distribution) to be 10.2 × 10^15 BTU/yr [BNID 104631]. Given a total 1999 U.S. energy consumption of 96.8 × 10^15 BTU/yr (Table 1.1 in primary source), energy used for food production accounted for 10.5% of the total energy used. In 2002, the food production system accounted for 17% of all fossil fuel use in the United States (Horrigan et al. 2002)." BTU=British Thermal Unit=1.06 kJ