Energy Use and Carbon Dioxide Emissions from Cropland Production in the United States, 1990–2004
2009
Nelson, Richard G. | Hellwinckel, Chad M. | Brandt, Craig C. | West, Tristram O. | De La Torre Ugarte, Daniel G. | Marland, Gregg
Changes in cropland production and management influence energy consumption and emissions of CO₂ from fossil-fuel combustion. A method was developed to calculate on-site and off-site energy and CO₂ emissions for cropping practices in the United States at the county scale. Energy consumption and emissions occur on-site from the operation of farm machinery and occur off-site from the manufacture and transport of cropland production inputs, such as fertilizers, pesticides, and agricultural lime. Estimates of fossil-fuel consumption and associated CO₂ emissions for cropping practices enable (i) the monitoring of energy and emissions with changes in land management and (ii) the calculation and balancing of regional and national carbon budgets. Results indicate on-site energy use and total energy use (i.e., the sum of on-site and off-site) on U.S. croplands in 2004 ranged from 1.6 to 7.9 GJ ha⁻¹ yr⁻¹ and from 5.5 to 20.5 GJ ha⁻¹ yr⁻¹, respectively. On-site and total CO₂ emissions in 2004 ranged from 23 to 176 kg C ha⁻¹ yr⁻¹ and from 91 to 365 kg C ha⁻¹ yr⁻¹, respectively. During the period of this analysis (1990–2004), national total energy consumption for crop production ranged from 1204 to 1297 PJ yr⁻¹ (Petajoule = 1 × 10¹⁵ Joule) with associated total fossil CO₂ emissions ranging from 21.5 to 23.2 Tg C yr⁻¹ (Teragram = 1 × 10¹² gram). The annual proportion of on-site CO₂ to total CO₂ emissions changed depending on the diversity of crops planted. Adoption of reduced tillage practices in the United States from 1990 to 2004 resulted in a net fossil emissions reduction of 2.4 Tg C.
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