The Life Cycle Of Greenhouse Gas Emissions From Maize
The life-cycle analysis of this multi-institutional project concentrated on determining the greenhouse gas emissions involved in pre-farm, on-farm and post-farm activities involved in the use of maize for the manufacture of corn chips.
When the emissions are all expressed in terms of CO2-equivalents, then pre-farm emissions comprise about 5% of the life-cycle emissions, on-farm activities comprise about 27%, and post-farm activities account for about 68% of life-cycle greenhouse gas emissions.
We have used a box of ten 400 g packets of corn-chips as the functional unit. The single largest source of greenhouse emissions is the electricity used during the manufacture of the corn-chips. This accounts for 0.09 kg CO2-e per box of corn chips. The next largest source is the emission of nitrous oxide on the farm as a result of fertilizer application (0.08 kg CO2-e per box). The manufacture of the box itself is the third largest source of greenhouse gas emissions, being 0.06 kg CO2-e per box.
The greenhouse gas emissions from fertilizer application are primarily nitrous oxide (N22O), which has a global warming potential of 310. In irrigated farm systems these emissions, when converted to CO2-equivalents, are about two and a half times as large as the greenhouse gas emissions as a result of the energy use in pumping water. Greenhouse gas emissions from the use of tractors on the form are about one-third of the emissions from pumping water.