Life cycle assessments of oilseed crops produced in rotation with dryland cereals in the inland Pacific Northwest

Authors: ANKATHI, S - Michigan Technological University; Long, Daniel; Gollany, Hero; PRAJESH, P - Michigan Technological University; SHONNARD, D - Michigan Technological University

Submitted to: International Journal of Life Cycle Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2018
Publication Date: 6/4/2018
Publication URL: http://handle.nal.usda.gov/10113/6353305
Citation: Ankathi, S.K., Long, D.S., Gollany, H.T., Prajesh, P., Shonnard, D. 2018. Life cycle assessments of oilseed crops produced in rotation with dryland cereals in the inland Pacific Northwest. International Journal of Life Cycle Assessment. 24(4):627-641. https://doi.org/10.1007/s11367-018-1488-y.
DOI: https://doi.org/10.1007/s11367-018-1488-y

Interpretive Summary: This study investigated the integration of bioenergy oilseeds into food grain cropping under low precipitation, non-irrigated conditions in the Columbia Plateau in eastern Oregon. Cradle-to-farm gate carbon footprint and cumulative energy consumption of intensified dryland cropping systems were determined on the basis of 1 kg of grain. The yields of winter wheat (WW) did not change noticeably when reduced tillage fallow (RTF) replaced summer fallow (SF) or when oilseeds were integrated into WW rotations with RTF. In addition, WW yields did not diminish for more intensive 3-yr rotations compared to conventional 2-yr rotations with or without oilseed crops. For all WW cases, greenhouse gas (GHG) emissions for WW were in the lower part of the range from literature for U.S. average conditions, providing evidence for the validity of these field trials. Fossil energy invested for bioenergy return for oilseed oil production showed net positive returns of nearly a factor of 2-4 across all spring and winter varieties. From a trade-off plot of GHG emissions versus total sales over six years per hectare, the WW-SF and WW-RTF were shown to be the most promising with low emissions and high sales. This study demonstrated that bioenergy oilseed cultivation can be incorporated into dryland food production systems without diminishing per area food grain yields, yet economic performance could be enhanced with higher yielding, drought tolerant oilseed varieties in order to encourage adoption by farmers.

Technical Abstract: Oilseed crops are expected to become increasingly important as feedstock for production of renewable jet fuel for the airline industry. However, there are potential social and environmental problems associated with using agricultural land to produce energy crops. The objective of this study was to determine the life cycle energy and greenhouse gas (GHG) emissions of several 2- and 3-yr crop rotations with cereals and oilseeds in a low precipitation environment of the Columbia Plateau. The purpose is to ascertain whether cropping intensification could improve energy efficiency and reduce the production of greenhouse gas emissions from agricultural operations. A life cycle assessment (LCA) was carried out to evaluate the fossil energy and carbon footprint of nine cropping systems characterized by different inputs applied to spring carinata (Brassica carinata) and winter canola (B. napus) in rotation with wheat and other cereal crops. Grain yield and field activity data from cropping systems were acquired from a long-term field experiment over a 5-yr period. Trace gas emissions were measured weekly over a 2-yr period using chamber methodology and laboratory gas chromatography. Inputs for the LCA regarding fertilizers, machinery fuel use, and pesticides were taken from the field trials and literature for fuel use. The results of winter wheat (WW) rotations are within the range of 320-430 g CO2/ kg WW, which are in good agreement with the literature for U.S. average WW cropping emissions, between 300-600 g CO2/ kg WW. The best oilseed result was 660 g CO2/ kg oilseed for canola following reduced tillage fallow (RTF). Highest yields were observed when food or bioenergy crops were planted following RTF. Bioenergy return on fossil energy invested for oilseed crops was between a factor of 2-4 depending on oilseed yield. The effect of allocation method (market value or mass allocation) on LCA results was negligible. From a trade-off plot of GHG emissions versus total crop sales over six years per hectare, WW-summer fallow and WW-RTF-winter canola-RTF were shown to be the most promising with low emissions and high sales. This study demonstrated that bioenergy oilseed cultivation can be incorporated into dryland food production systems without diminishing per area food grain yields, yet economic performance could be enhanced with higher yielding, drought tolerant oilseed varieties in order to encourage adoption by farmers.