Sunday, October 7, 2007

Potential GHG reduction for regionally-directed food purchasing

A team of University of Washington students and professor(s) recently released a comprehensive report on the local food system entitled the "Seattle Food System Enhancement Project". Within this work is their Greenhouse Gas Report that compares the ghg emissions of a local plate of food to a comparable global plate. The team used a life cycle assessment approach using the ISO 14040 definition. Their methods are an attempt to create "A benchmark for examining the greenhouse gas impact of cultivating and transporting specific items of food into the city of Seattle."

The foods compared, and their ghg emissions:
  • Regional plate
    • WA apple, asparagus, potato; Alaska wild salmon
    • GHG emissions = 2,102 grams CO2e
  • Global plate
    • New Zealand apple, Peruvian asparagus, Idaho potato, Norway farmed salmon
    • GHG emissions = 3,083 grams CO2e
Net savings for local plate: 981 grams CO2e

I decided to start playing with this number and try to calculate potential ghg reductions if this was applied to a segment of the whole state population for part of the year.

There are about 6.4 million people in WA state. The major assumptions for my calculations are that 20% of the population would eat a comparable plate of lower carbon food for half the year (182 days). These assumptions are further tied to carbon savings that are comparable with this plate of food. Why such variables? Well, the research is just not there to elaborate on this pressing issue. We absolutely have to do more of these calculations to understand where ghg reductions can occur, but in the meantime I am going to work with such estimates. I also understand that people are not going to eat this same meal for half the year, but I will assume that 20% of the people could eat a plate of food, or total food for the day, that has a comparable ghg savings.

From these parameters comes the notion that if 20% of WA state residents ate a similar plate of lower carbon food for half the year we could reduce our food carbon footprint by 228,534 Metric Tons CO2e per year (.23 MMT CO2e/yr).

Here is a screenshot of my spreadsheet (click for larger image):

These types of savings are no small potatoes. I am a member of the Agriculture Technical Working Group for WA State's Climate Advisory Team. A medium reduction goal is 0.1 to 1.0 MMTCO2e per year by 2020.

Items for further research:
  1. What are the ghg reductions for other regional products?
  2. What are the economic impacts of such a change in purchasing?
    1. Local multiplier work shows a strong positive gain.
    2. Impacts on this trade-dependent state less clear.
Source: " Seattle Food System Enhancement Project", Program on the Environment Certificate in Environmental Management Keystone Project, 2006-2007, p.79,

Monday, October 1, 2007

Carbon footprint: vegan diet vs. Chevy Suburban

The paper Diet, Energy and Global Warming compares the carbon footprint of plant and animal-based first to each other, and then to the carbon footprint of a Toyota Prius and Camry Solara, and Chevy Suburban. From the paper:

Narrative description

" The greenhouse gas emissions of various diets varies by as much as the difference between owning an average sedan versus a Sport Utility Vehicle under typical driving conditions."

Scientific description
" While for personal transportation the average American uses 1.7 × 107 – 6.8 × 107 BTU yr−1 , for food the average American uses roughly 4 × 107 BTU yr−1 . Thus there exists an order of magnitude parity in fossil energy consumption between dietary and personal transportation choices." The key number here is the 1.7 and 4 comparison since the exponent is the same.

Source: Gidon Eshel and Pamela Martin, Diet, Energy and Global Warming, Earth Interactions, May 2005,