Environmental Impact calculation

Methodology overview

The environmental impact of your meat free days is an estimate of a very complex calculation.

CO₂ emission reduction estimate

For our calculation, we considered some standard CO2eq emission associated to each type of diet (1):

  • A Western standard meat‑based diet: ~ 7.2 kg CO₂e/day
  • Vegetarian diet: ~ 3.8 kg CO₂e/day
  • Vegan diet: ~ 2.9 kg CO₂e/day

Based on these, switching one day to a vegetarian saved around 3.4 kg CO₂e while a vegan diet would save 4.3 kg CO₂e

Energy reduction

For the calculation of energy reduction associated to a meat-free diet, we considered the average meat intake to be 165 g a day (2). We then assumed that the meat is replaced 1:1 by plant products. In reality, swaps happen by calories or protein, but the trend is the same: plant foods require far less energy.

Finally, we considered the average energy consumption for meat products and plant based products (3)

Average Cumulative Energy Demand

  • Beef: ~22 kWh/kg
  • Pork: ~29 kWh/kg
  • Chicken: ~18 kWh/kg
  • Plant analogs (pea/soy): ~2.8–3.9 kWh/kg (avg ~3.3 kWh/kg)

As most users mix all sort of meat, we just took an average value of 23 kWh/kg.

So in the end, a day without meat saves around 3.3 kWh of energy.

Water Saved

For this calculation, we made the same hypothesis of 165 g of meat consumed a day and that it is replaced 1:1 by plant products on a meat-free diet.

Then, when it comes to water consumption, we distinguished 3 kinds of water footprints:

  • Blue = irrigation water withdrawn from rivers/groundwater
  • Green = rainfall stored in soils
  • Grey = water needed to dilute pollution to standards.

For a conservative and fair evaluation, we focused on blue water only because it is the part of water use that can lead to conflicts: farms, cities, industries, and ecosystems all depend on the same freshwater sources. Reducing blue water use directly eases this competition.

On the other hand, the switch from one kind of agriculture (cattle) to the other (plant) is much less obvious for green and grey water.

Life-cycle averages consumption of blue water for various kind of food (4):

  • Beef ≈ ~600 L/kg (≈4% of ~15,400 L/kg total).
  • Pork ≈ ~360–450 L/kg (blue share of ~6,000 L/kg total).
  • Chicken ≈ ~120–200 L/kg (blue share of ~4,300 L/kg total).
  • Plant replacement (legumes/soy/peas, tofu): ~50–150 L/kg

We estimate a day without meat saves around 50 L of blue water.

Land use saved / Surface agricole épargnée (Surface préservée)

Same as previous we assumed the average daily meat consumption to be 165g and that it is replaced 1:1 by plants.

We then use the land use intensity (area × time) in m²·year per kg (5). It measures how much land is occupied to produce food. Less land used = less pressure to clear forests

For each food category, here the average values we took (6):

  • Beef: average of 38 m²/kg → use 38
  • Pork: average of 10.5 m²/kg → use 10.5
  • Chicken: average of 9.4 m²/kg → use 9.4
  • Average of these three meats: 19.3 m²/kg
  • Plant replacement (pulses/legumes): average of 4.5 m²/kg

We then estimate a day without meat preserves around 2.4 m² of land.

Sources

(1) Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK - https://link.springer.com/article/10.1007/s10584-014-1169-1

(2) Our World in Data - daily meat consumption per person - https://ourworldindata.org/grapher/daily-meat-consumption-per-person

(3) Comparative Life Cycle Assessment of Plant and Animal based meat - Good Food Institute https://gfi.org/wp-content/uploads/2024/11/Comparative-life-cycle-assessment-of-plant-and-animal-based-meats_Key-findings.pdf

(4) Water footprint network - https://www.waterfootprint.org/water-footprint-2/what-is-a-water-footprint/

(5) https://josephpoore.com/Science 360 6392 987 - Accepted Manuscript.pdf

(6) Sustainable Production and Consumption - https://www.sciencedirect.com/science/article/pii/S2352550921000178