Generated Summary
This study explores the implications of shifting US dietary patterns on greenhouse gas emissions (GHGE). Using the USDA’s Loss Adjusted Food Availability (LAFA) dataset as a proxy for the current US diet, the researchers linked commodity foods to GHGE emission factors. The study then developed and analyzed various dietary scenarios projected to 2030, including maintaining the baseline diet, following USDA meat projections, reducing animal-based food consumption, and further reducing beef consumption. The aim was to estimate the potential for reducing GHGE through dietary changes, emphasizing the substitution of animal-based foods with plant-based alternatives. The methodology involved calculating per capita GHGE associated with each scenario and assessing the population-level impacts of these changes. The study also highlights the role that changes in diet can play in climate action.
Key Findings & Statistics
- The average US diet is associated with the emission of 5.0 kg CO2 eq. per person per day.
- Red meat (beef, pork, lamb) contributes 47% of the GHGE, although it represents only 9% of the calories.
- All animal-based foods contribute to 82% of the baseline diet GHGE.
- In 2016, the average American consumed 133 pounds of red meat and poultry.
- USDA projects slight increases in per capita red meat and poultry consumption by 2028 (scenario 2), increasing the carbon footprint to 5.14 kg CO2 eq. per person per day.
- Scenario 3 (reducing animal-based foods by half) results in a 35% decrease in GHGE from the baseline, to 3.3 kg CO2 eq per person per day.
- Red meat represents 36% of the total emissions under scenario 3.
- Scenario 4 (reducing beef consumption by 90% and other animal-based foods by 50%) cuts diet-related emissions by 51% compared to the baseline diet, resulting in 2.4 kg CO2 eq per capita per day.
- The average American would consume 50.1 pounds of meat and poultry per year under scenario 4.
- An unchanged diet would result in 646 million metric tonnes CO2 eq. (MMT) in 2030.
- Scenario 3 leads to 224 MMT less emissions per year in 2030, a reduction equivalent to the annual emissions of 47.5 million average passenger vehicles.
- The cumulative reduction in emissions from 2016 to 2030 is estimated to be 1634 MMT under scenario 3.
- By replacing 90% of beef, the cumulative emission reduction increases to 2408 MMT.
- Cutting the intake of all animal-based foods by half and replacing with equivalent quantities of plant-based foods (scenario 3) results in a 35% decrease in GHGE from the baseline, to 3.3 kg CO2 eq per person per day.
- Under this scenario 3, red meat represents 36% of the total emissions.
- Further reducing consumption of beef to only 10% of the baseline value, and subsequent replacement with plant-based proteins (scenario 4), cuts the diet-related emissions to 2.4 kg CO2 eq per capita per day, a 51% decrease from the baseline diet.
- The total emissions associated with producing the average US diet amounts to 5.0 kg CO2 eq. per person per day.
- Red meat (beef, pork, lamb) represents 9% of the calories available from this diet, contributing 47% of the GHGE.
- All animal-based foods combined (red meat, poultry, fish/seafood, eggs, dairy, and animal based fats) represent 82% of the baseline diet GHGE.
- The changes in meat consumption projected by the USDA reported in Table 4 lead to a slight increase in the calories (2563 Cal/capita/day) and the diet carbon footprint in 2030. The average diet GHGE increases to 1875 kg CO2 eq. per capita per year (5.14 kg CO2 eq. per capita per day) and the contribution from meat increases to 49%, with 41% coming from beef.
- Scenario 3 involves a 50% reduction in the weight availability of all animal-based foods in the diet, increasing the amount of legumes, soy products and nuts to match the baseline diet ounce equivalents of protein foods, adding soy milk to match the baseline diet cup equivalents of dairy, and increasing plant based fats to make up for reduced animal-based fats. The resulting diet can be seen in Table 9, in comparison to the baseline. In this scenario, the quantity of nuts in the diet increases by a factor of 1.9, soy products by a factor of 21, and legumes by a factor of 1.6. Total calories are slightly lower but still within 2% of the baseline diet. Diet related GHGE in this scenario decrease by 35% from the baseline to 3.3 kg CO2 eq/capita/day. After a 50% reduction in animal-based foods, meat still contributes 36% to the diet’s carbon footprint, with beef representing most of this at 31% of the total.
- Scenario 4 extends scenario 3 by increasing the reduction in beef to 90% (food quantity, calories and GHGE also shown in Table 9). Under this scenario, the quantity of nuts in the diet increases by a factor of 2.2, soy products by a factor of 24, and legumes by a factor of 1.8. Per capita beef consumption decreases to 4.0 lbs per year, or 0.18 oz. per day. At 2.4 kg CO2 eq per capita per day, diet GHGE decrease to 51% of the baseline diet, and meat now represent only 16% of the total with beef representing half of that.
- In the absence of dietary change, emissions associated with producing the food that we eat are expected to increase 9% by 2030 due to population growth.
- Scenario 3 – replacing 50% of all animal-based foods with plant-based alternatives – leads to an emission reduction of 224 million metric tonnes of CO2eq. (MMT) in 2030.
Other Important Findings
- USDA’s Loss Adjusted Food Availability (LAFA) data for 2016 were used as the baseline diet, with emissions factors derived from life cycle assessment literature linked to these commodity foods.
- A number of dietary scenarios projected to 2030 were developed to assess the impact of dietary changes on GHGE.
- The study considered the implications of the assumptions necessary in the exercise and discussed those impacts.
- In the absence of consistent, regionally specific datasets on environmental impacts of agricultural production, it is common practice in the current literature on diet-related environmental impacts to utilize generic representative data.
- Concerted effort was made in the linking process to assure that the weight basis properly corresponded between LAFA and emission factor data, especially in the inclusion or exclusion of inedible portions (rinds, peels, cores, bones, etc.)
- After establishing projected national average dietary patterns under each scenario, associated annual per capita emissions were calculated by multiplying commodity intake by the corresponding emission factor and summing across all foods.
- The “retail weight” for meats in the LAFA dataset is on a boneless basis, and the necessary conversion can be derived from the Food Availability spreadsheets, and is reported in Table 3.
- The study used population projections from the US Census Bureau to estimate a cumulative change in emissions from the status quo for each scenario.
- The emission estimates presented in Figure 3 and Table 7 include contributions from food losses, as agricultural production of food loss and waste carries the same environmental burden as consumed food.
Limitations Noted in the Document
- The study relies on the USDA’s LAFA dataset and associated emission factors, which may not fully capture the complexities of food production and consumption.
- The study focuses on GHGE and does not investigate other dietary changes that might accompany the substitution of animal-based foods for plant-based foods (e.g., changes in grain consumption, fruits, vegetables, or added fats).
- Secondary effects on production, market supply, and prices, either within the US or internationally, were not considered.
- It is assumed that agricultural production in the US adjusts to changes in domestic demand without significant increases in exports to other countries.
- Indirect economic rebound effects were not considered, which could influence the overall environmental impact.
- The emission factors used were based on generic commodity-specific emission factors and are not specific to US production conditions.
- The average emission factors are assumed to remain static across the changes in dietary patterns.
- The study only captures agricultural production and basic processing of processed commodity foods and does not include the downstream stages of additional processing, packaging, distribution, retail, food service, and home storage and cooking.
- The study did not investigate changes in grain consumption, fruits, vegetables, or added fats.
Conclusion
The study highlights the critical role dietary changes can play in mitigating greenhouse gas emissions associated with food production. Replacing animal-based foods with plant-based alternatives can significantly reduce the carbon footprint of the average US diet. The findings underscore the importance of addressing agriculture and food systems in climate change interventions. The authors conclude that significant reductions in greenhouse gas emissions are achievable through dietary shifts. The results emphasize the importance of considering agriculture, food systems, and nutritional education when addressing climate change interventions. The projection scenarios presented in this report point to the urgency of such efforts, as decisions made now will have a cumulative impact over the next decade. A 224 MMT reduction in annual emissions represents 24% of the reduction from 2017 emissions needed to meet the US Intended Nationally Determined Contribution. The study stresses the need for action from all sectors of society to achieve these reductions. The study demonstrates that sizable reductions in greenhouse gas emissions are possible through reductions in animal-based foods. These findings emphasize the importance of addressing agriculture, food systems, and nutritional education when considering climate change interventions. The projection scenarios presented here point to the urgency of such efforts, as decisions made now will have a cumulative impact over the next decade. The study calls for a multi-faceted approach involving policymakers, the food industry, and consumers to facilitate these dietary shifts and realize the associated environmental benefits. Moreover, the potential for reducing greenhouse gas emissions through dietary changes is significant, which requires further attention on how to transform food systems to be sustainable. The findings serve as a call to action, demonstrating that changes in diet, particularly the substitution of animal-based foods with plant-based alternatives, are critical for reducing the environmental impact of food systems and aligning with climate goals.
IFFS Team Summary
- https://www.ecowatch.com/meat-consumption-greenhouse-gases-vegetarian-2645891904.html?rebelltitem=1#rebelltitem1
- Background: This paper calculates the decrease in food related GHG per capita in USA:
- According to 2016-2017 data
- If there was a reduction in meat consumption
- And a corresponding increase in plant based proteins and fats
- Dairy milk is replaced with soy milk but not other plant milks
- Equivalent caloric intake is considered within 2%
- Packaging is not considered
- The paper promotes the idea that reduction in animal products, even without their elimination, is more palatable
- But still causes a drastic reduction of total GHG emissions needed to reach US government targets
- Paper uses DATAfield Database from University of Michigan
- Baseline Stats: in 2016, the average person in USA 2016
- Consumes 897 lbs or 406 kg of food per year (including the weight of liquid dairy milk or soy milk)
- Consumes 2543 kcal per day
- Creates food related GHG emissions of 5.0 CO2 equivalent person per day
- 82% of this is from animal based foods
- Avg person consumers 133 lbs = 60.3 kg of red meat and poultry per year
- Red meat, especially beef, has the largest GHG impact
- Food related GHG equivalents are calculated over 100 years, thus diluting the impact of methane and nitrous oxide
- Total of 662 MMT (Million Metric Tonnes) per year in USA
- 29% of these GHG are from food losses (from retail to consumer)
- Animal based foods contribute 80% of this amount
- Thus 23% of GHG emissions from food waste are from animal foods
- Results: 50% reduction in meat eggs dairy (scenario 3 in the paper)
- Results in 35-36% reduction in food related GHG
- 5.0 -> 3.3 kg of CO2 equivalent person per day
- This results in a 224 MMT reduction for total us population
- Achieves 24% of the reduction needed to achieve USA 2017 GHG reduction targets
- Equivalent to removal of 47.5 million vehicles from the road
- 50% reduction in meat dairy and eggs, but including 90% reduction in beef, would result in even greater GHG reduction
- 4) dataFIELD: data from University of Michigan Centre for Sustainable Systems
- http://css.umich.edu/page/datafield
- Excellent resource for GHG data for different food items
- Looks at food in the edible form – i.e. removing bones, rather than carcass weight
- Distinguishes pulses in dried and fresh forms
- See second tab for main data set
- Looks at GHG emission and CEA