Sustainability and Food Systems
Plant-based food doesn't sit in a vacuum — it sits inside a global food system with land, water, energy, biodiversity, labor, and policy all in tension. This module gives you the analytical tools to think clearly about sustainability claims, and to spot the easy ones from the genuine ones.
Learning objectives
- Define life-cycle assessment (LCA) and identify its main impact categories.
- Compare the environmental footprints of major plant and animal protein sources.
- Discuss honestly the trade-offs of plant-based supply chains (palm oil, monocultures, transport).
- Place plant-based food within broader frameworks like the EAT-Lancet planetary health diet.
Life-cycle assessment, briefly
A life-cycle assessment totals the environmental impacts of a product from "cradle to grave" — raw material extraction, production, transport, processing, packaging, use, end-of-life. The most common impact categories in food LCAs:
- Greenhouse gas emissions (kg CO₂-equivalent per kg product) — climate impact
- Land use (m² per kg) — opportunity cost vs forests, grasslands, biodiversity
- Freshwater withdrawal (L per kg) — pressure on rivers and aquifers
- Eutrophication potential — nitrogen and phosphorus runoff into waterways
- Acidification potential — sulfur and ammonia emissions
LCAs are powerful but assumption-heavy. The same product can score very differently depending on the system boundaries chosen (e.g. do you include the methane from manure? the carbon stored by pasture? the deforestation embedded in a soy crop?). Treat point estimates as orientation, not gospel — and trust well-cited meta-analyses over single studies.
What the numbers actually say
The 2018 Poore & Nemecek meta-analysis (in Science) pooled LCAs covering 38,700 farms and 1,600 processors across 119 countries. It remains the most comprehensive view we have. Selected medians, per kg of food product:
| Food | kg CO₂-eq / kg | Land use (m²) | Freshwater (L) |
|---|---|---|---|
| Beef (beef herd) | ~60 | ~164 | ~1,450 |
| Lamb & mutton | ~24 | ~185 | ~1,800 |
| Cheese | ~21 | ~88 | ~5,600 |
| Pork | ~7 | ~11 | ~1,800 |
| Poultry | ~6 | ~7 | ~660 |
| Eggs | ~4.5 | ~6 | ~580 |
| Tofu | ~3 | ~2 | ~150 |
| Peas | ~1 | ~3.4 | ~400 |
| Other legumes | ~1 | ~3.4 | ~400 |
| Nuts | ~0.4 (carbon-negative on some farms) | ~7 | ~4,100 (almonds high) |
| Wheat | ~1.6 | ~3.9 | ~1,650 |
The pattern is unambiguous: animal foods (beef especially) sit at the high end of nearly every category; plant proteins sit at the low end. Even the most thoughtfully produced beef is typically more impactful per kg than the most carelessly produced legumes.
Why so much higher for animals?
Three structural reasons: trophic inefficiency (about 90% of the energy a cow consumes is used by the cow itself, not stored as edible mass — only 10% becomes meat); methane (ruminants like cows and sheep generate methane via enteric fermentation, a far more potent greenhouse gas than CO₂ over short timescales); and land (grazing and feed production together occupy roughly half of all habitable land on Earth).
Honest trade-offs
Plant-based isn't a free lunch — it has its own footprint. A serious sustainability practitioner reckons with the trade-offs:
Palm oil
Palm is the highest-yielding oil crop on Earth — far more efficient per hectare than rapeseed, sunflower, or soy. The problem is where it's grown: vast tracts of tropical rainforest in Indonesia and Malaysia have been cleared for oil palm, displacing biodiversity (orangutans, tigers) and releasing stored carbon. The answer isn't necessarily to switch oils — alternatives often need more land — but to demand certified, deforestation-free palm.
Almonds and water
Almonds are wonderfully nutrient-dense and have low GHG emissions — but California's drought-stressed almond industry uses extreme quantities of irrigation water. Almond milk's water footprint is high per liter even though its carbon footprint is low.
Soy and deforestation
The vast majority of global soy is grown for animal feed, not for direct human consumption. Soy-fed beef carries soy's land-use and deforestation cost plus the cow's. Soy products eaten directly (tofu, tempeh, soymilk) are dramatically more efficient. The "soy is bad" rhetoric typically conflates these two flows.
Ultra-processed plant meats
Modern HMMA and isolate-based products use processing energy that a chickpea does not. Even so, multiple LCAs find their footprints sit comfortably below conventional beef and even pork — though above whole legumes. The honest framing: an Impossible Burger is far better than a beef burger, and a bowl of lentils is better still.
Whole plant foods → minimally processed plant foods → modern plant meats → poultry → ruminant meats. The gradient is real, the differences are large, and any move down the list helps.
Beyond the plate
Personal food choices matter — and so does food policy. The EAT-Lancet Commission's 2019 "planetary health diet" — a flexitarian pattern dominated by plants with modest animal protein — was modeled to feed 10 billion people in 2050 within Earth's planetary boundaries. Many of its recommendations look a lot like a thoughtful plant-based diet plus optional small servings of fish or eggs.
Levers beyond the individual:
- Public procurement — schools, hospitals, and government cafeterias choosing plant-forward menus.
- Subsidy reform — most agricultural subsidies historically support commodity grains for feed, not direct human food.
- Labelling and pricing — putting environmental footprint on the package; ending ambiguity about what a "plant-based meat" is.
- Farmer transition support — land restoration, agroforestry, plant-protein crops for direct human consumption.
Kitchen Lab #10 — Audit your week
~1 hourWhat you'll do
Run a simple, honest audit of your last week of meals. Without guilt or claim, just look. The aim is to identify the biggest single shifts that would meaningfully reduce your food footprint.
You'll need
- A notebook or spreadsheet
- A free calculator: the Our World in Data food carbon explorer is excellent for orientation
Procedure
- Write down every meal, snack, and drink for the past 7 days as best you can recall.
- For each, note the dominant protein source: beef, lamb, pork, poultry, fish, dairy, eggs, legumes/tofu, nuts, etc.
- Multiply portion sizes (in grams) by the per-kg CO₂-eq from the table earlier in this module to estimate weekly food emissions.
- Identify your top 3 emission contributors. Are they daily habits or occasional indulgences?
- Imagine swapping each top contributor for one tier "down" the hierarchy. Don't commit — just calculate the difference.
What to take from this
For most people in industrialized countries, > 50% of food emissions come from a small number of high-impact items — especially red meat and cheese. Reducing these (not eliminating anything else) is the single highest-leverage food choice available to almost everyone.
Discussion
Questions, corrections, or your own results from the lab? Drop them here. Comments are powered by GitHub Discussions via giscus; you'll need a free GitHub account.