Life cycle greenhouse gas and energy assessment of winegrape production in California

Authors: Steenwerth, Kerri; STRONG, EMMA - University Of California; Greenhut, Rachel; WILLIAMS, LARRY - University Of California; KENDALL, ALISSA - University Of California

Submitted to: International Journal of Life Cycle Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2015
Publication Date: 7/30/2015
Publication URL: http://Int J Life Cycle Assess (2015) 20:1243–1253 DOI 10.1007/s11367-015-0935-2
Citation: Steenwerth, K.L., Strong, E.B., Greenhut, R.F., Williams, L., Kendall, A. 2015. Life cycle greenhouse gas and energy assessment of winegrape production in California. International Journal of Life Cycle Assessment. 20:1243–1253. doi: 10.1007/s11367-015-0935-2.

Interpretive Summary:

Technical Abstract: Purpose: This study applies life cycle assessment (LCA) to assess greenhouse gas (GHG) emissions, energy use, and direct water use in winegrape production across common vineyard management scenarios in two representative growing regions of California, USA (Napa and Lodi). California hosts 90 percent of the U.S. grape growing area, and demand for GHG emissions estimates of crops has increased due to consumer interest and policies such as California’s Global Warming Solutions Act, which includes a cap-and-trade system for GHGs. Methods: Process-based LCA methods were used to characterize energy and GHG emissions from California winegrape production. The scope includes the annual cycle for winegrape production, beginning at raw material extraction for production of vineyard inputs and ending at delivery of winegrapes to the winery gate. Modeled production scenarios (240) were based on data from land owners, vineyard managers and third party vineyard management companies. Thirty in-person interviews with winegrape growers throughout Napa and Lodi were also conducted to identify the diversity of farming practices, site characteristics, yields and vineyard structures (among other factors) across 90 vineyards. These vineyards represent a cross section of the regional variability in soil, climate, and landscape used for winegrape production. Direct water use was modeled using reference evapotranspiration and crop coefficients. Results and Discussion: Energy use and global warming potential (GWP) across all possible 240 production scenarios range between 1653 and 7503 MJ/ton, and 84 and 471 kg CO2e/ton, respectively. Of the 240 possible scenarios, 12 were selected for closer inspection. Energy use and GWP in Napa were more than twice as great as Lodi per ton of winegrapes, but energy use and GWP were just 26 and 23% greater in Napa than Lodi per hectare of vineyard, respectively. Hand harvest practices in Napa (versus mechanical harvesting as is done in Lodi) and frost protection practices contributed to greater energy use and GWP on a per area basis, and lower yields in Napa account for the large difference on a per ton basis. Three other energy use and GHG emissions hotspots were identified: organic pesticide use and pesticide manufacturing; on-farm truck use and associated fuel use; and field nitrous oxide emissions associated with leguminous cover crops. Conclusion: The findings underscore the regional distinctions in winegrape production that affect the carbon footprint, energy footprint, and direct water use. When vineyards are managed for lower yields, the energy use and GWP will be higher per metric ton of grapes, which would then elevate the winery’s overall environmental impact. Additional co-products could distribute environmental impacts as growers manage intentionally for low winegrape yields to achieve other desirable production goals. Findings can be applied more broadly than Napa and Lodi as a range of soils, climates and management practices were modeled in this study.