Cover: Growing Toward a Low-Carbon Future

Growing Toward a Low-Carbon Future

Estimating Greenhouse Gas Emissions in California's Westlands Water District

Published Mar 1, 2023

by Michelle E. Miro, Nidhi Kalra, Jonathan Lamb, Nihar Chhatiawala

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Research Questions

  1. What existing crop production and related land use practices account for the most and least GHG emissions?
  2. How do GHG emissions from crop production and related land uses change under climate change?
  3. How would changes in crop production and related land use practices impact GHG emissions and key resource trade-offs, such as water use?

The authors assessed the greenhouse gas (GHG) emissions of crop production in California's Westlands Water District and the trade-offs of policies aimed at decarbonization. The authors developed a bottom-up carbon and nitrogen cycle model to evaluate GHG emissions from 37 different crop types and five different land uses (e.g., solar energy generation, pasture), as well as key resource trade-offs introduced by options to decarbonize Westlands' crop production. This model was coupled with a water use model and an energy use model. They also analyzed how these resource trade-offs could differ under climate change.

They found that crop production and land use in Westlands will release about 1.2 metric tons of carbon dioxide equivalent per acre per year from 2020 to 2050. Almonds and pistachios, as well as fallowed land, are the major contributors to these emissions because of the number of acres planted. In the short term, Westlands will offset more emissions than it releases through solar generation and will not start contributing net emissions until 2033. Further expanding solar generation in the district by converting a portion of Westlands-owned land to solar generation would shift the year in which Westlands becomes a net positive emitter to 2043.

Key Findings

Crop production and land use in Westlands will release about 1.2 metric tons of carbon dioxide equivalent (MtCO2eq) per acre per year, on average, from 2020 to 2050

  • Almonds, pistachios, and fallowed land are the major contributors to emissions in Westlands because of the number of acres planted.
  • When emission offsets from solar generation from the 15,500 acres dedicated to solar energy are factored in, this value drops to an average of 0.47 MtCO2eq per acre per year from 2020 to 2050.

Although these are average values across the study horizon, annual emissions change over time

  • In the short term, Westlands will offset more emissions than it releases through solar generation and will not start contributing net emissions until 2033.
  • This transition happens as California's grid becomes less carbon intensive over time, and the net offset from solar energy declines.

Introducing or expanding alternative practices in Westlands, such as fertilizer or tillage choices, could reduce emissions further

  • Introducing no-tillage practices across all farms in the district would reduce net emissions from 0.47 MtCO2eq per acre per year to 0.12 MtCO2eq per acre per year, a net emissions reduction of over 75 percent.
  • Converting some Westlands-owned land to solar generation in 2025 provides the largest reductions in emissions and shifts the year in which Westlands becomes a net positive emitter to 2043.
  • By combining this alternative of additional land conversion to solar energy with no-tillage practices, any positive emissions after 2043 would be reduced without increasing water demands.

Research conducted by

The research described in this report was sponsored by Westlands Water District and conducted in the Community Health and Environmental Policy Program within RAND Social and Economic Well-Being.

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