Nutrient Management Research Database

This is the first article of a two-article series. This first article describes the development of a framework and life cycle assessment (LCA) model for orchard system products, which is tailored to California almond production. Regionally-specific data are used to construct a comprehensive, multi-year life cycle assessment model for orchard agroecosystems, including models for tree biomass accumulation, nursery production, on-field equipment use, material and chemical transport, and hulling and shelling operations. Surveys were used to collect data from multiple actors in the production chain, including nursery and orchard managers, agricultural service providers, hullers and shellers, and biomass power facility operators who use co products from almond production. The result is a life cycle inventory for energy use, greenhouse gas emissions, and criteria air pollutants, and an inventory of direct water use for typical almond production in California, from field to factory gate. One kg of almonds at the processing facility gate requires 24.2 MJ of energy, and results in 0.70 kg CO2-equivalent. Nutrients and irrigation water were the dominant causes of both energy use and emissions in the almond life cycle, and co-product credits play an important role in reducing the life cycle environmental impacts attributable to almonds; co-product credits of 11.7 MJ and 1.62 kg CO2-equivalent are generated from orchard biomass and almond shells used in electricity generation and almond hulls used as cattle feed. Uncertainty and temporary carbon storage in the orchard agroecosystem are explored in the second article of this series.

• The following processes are quantified over a 25-year period (the productive lifespan of an almond orchard): nursery production of almond saplings; orchard establishment; field operations; production and transport of chemical and material inputs to the orchard; pollination services; biogeochemical field emissions; and transport and utilization of co-products
  
  
• The following environmental flows are captured in the analysis: renewable and non-renewable primary energy; biogenic carbon assimilated during biomass growth and emitted during biomass utilization; direct water use; GHG emissions; criteria air pollutants
  
  
• UC Davis Cost and Return studies were used as the basis for the orchard LCA model. These document annual crop production costs for various California crops by inventorying typical inputs and practices on a regional basis up to the farm gate. Gaps in the Cost and Return studies data were filled by collecting primary data via surveys administered to businesses and individuals involved in orchard crop production.
  
  
• Life Cycle Inventory (LCI) data quantifying energy inputs, material inputs, and emissions for a variety of materials used throughout the orchard crop production cycle were used in the model. Several original LCIs were created for the model, including the following: nursery production of orchard saplings; orchard pollination by commercial beekeepers; irrigation water from the California aqueduct system; and LCIs for a number of custom operations, most notably orchard removal.
  
  
• Impact assessment characterization included in this assessment is global warming potential (GWP), using 100-year and 20-year GWPs from IPCC to report summary outcomes.

Nutrient management and irrigation water were the dominant causes of both energy use and emissions in the almond life cycle, and co-product credits play an important role in reducing the life cycle environmental impacts attributable to almonds.

For field to farm-gate:

• Agrochemical inputs (pesticides and fertilizers) represent 33.3% and 48.8% of energy and 100-year GWP, respectively
• Nutrient management represents 23.9% and 39.1% of energy use and 100-year GWP, respectively
• Production phase dominates energy use and 100-year GWP: 74.8% and 53.0%, respectively
• Field operations contribute 12.5% of energy use and 30.9% of 100-year GWP

Almond orchard energy use is 11.2 MJ per kg in-hull almonds at farm gate, and 100-year GWP is 0.74 kg CO₂e.

• When hulling and shelling operations are included, both energy use and 100-year GWP per kg of almond kernel more than triple to 35.8 MJ and 2.31 kg CO₂e (respectively)
• When credits from co-products used in electricity production and livestock feed are included, energy use is reduced to 2.42 MJ per kg in-hull almonds at farm gate; 100-year GWP is reduced to 0.70 kg CO₂e.