What is EFU?
What is EFU? The human-scale unit that makes planetary material flows visible
We usually measure the world’s material flows in billions of tonnes, gigatonnes or abstract indicators. The EFU (Human Flux Unit) takes a different approach: it translates every large number back to the daily material throughput of the human body. Suddenly the scale of planetary processes becomes understandable, comparable and personal — not as abstract statistics, but in human terms.
1. The core definition – what is 1 EFU?
1 EFU = the total daily material throughput of an average adult human ≈ 20 kg per day.
This 20 kg includes:
- inhaled air (~15 kg),
- water intake (~3 kg),
- dry food (~0.5 kg),
- and metabolic water plus minor components (~1.5 kg).
Over an 80-year lifetime, roughly 542 tonnes of material flow through us — equivalent to about 29 200 EFU.
A human being is therefore not a static 70 kg object, but a continuous flux pattern sustained by more than half a million tonnes of flowing matter.
Simple conversion formulas:
- Daily: kg/day ÷ 20 = EFU/day
- Annual: kg/year ÷ 7300 ≈ EFU/year
2. Physiological & Material Balance – the 20 kg model
The 20 kg/day figure is not arbitrary. It is based on a closed metabolic mass-flow model:
ComponentApprox. amountNoteInhaled air~15 kgO₂ + N₂Water intake~3 kgdrinks + food waterDry food~0.5 kgMetabolic water + other~1.5 kg
Total~20 kgdaily total throughput
The energy side is also linked: human basal metabolic rate is roughly 100 W continuous power (~2000–2500 kcal/day). EFU is mass-based, yet metabolic energy and material flows are tightly coupled.
3. Humanity’s economic material throughput and inequalities
Around 2023, materials extracted and used by humanity reached approximately 104 billion tonnes per year (about 30 billion tonnes in 1970).
Converted:
- Annual economic material throughput ≈ 14.2 billion EFU
- Daily average ≈ 39 million EFU
- Per person currently ~ 35 kg of material per day
Population vs. material throughput:
- Population 1970→2023: ~2.2-fold
- Material throughput: ~3.5-fold
- Per capita: from ~1.1 EFU/year (1970) to ~1.75 EFU/year (2023)
Inequalities become visible in EFU terms:
- North America / Australia: ~2.7–3.4 EFU/year
- Europe: ~2.0–2.5 EFU/year
- India / Africa average: ~0.5–0.7 EFU/year
One Western person’s material throughput can equal that of 5–6 people in lower-income regions.
Relative to long-term sustainability estimates (roughly 6–8 billion EFU/year), the current ~14.2 billion EFU/year sits in the overshoot zone — about 1.8 planet-equivalents.
(EFU can also be read as a human-normalised MFA / Industrial Ecology indicator and placed in parallel with the biogeochemical flows of the Planetary Boundaries framework.)
4. Citizen Science data protocol
Household- or community-level data (water, food, energy, waste) can be converted into EFU using the simple formulas above.
Validation relies on standardised templates and open Zenodo files, so citizen-collected data can reach research-grade quality.
The project is registered as Active on the European Citizen Science Platform (Project #836).
5. Practical example – case study
1 kg of primary aluminium (including mining overburden), according to published MFA data, can mobilise several thousand kilograms of total material.
Converted to the 20 kg human daily baseline, one kilogram of aluminium corresponds to several hundred EFU — the daily material throughput of hundreds of people.
A similar order-of-magnitude calculation can be made for a city of 100 000 inhabitants: its daily material metabolism reaches hundreds of thousands of EFU, far exceeding the pure biological throughput of its residents.
These examples show how technological and biological scales become directly comparable on the same unit.
6. Future directions and call for collaboration
Open research questions include:
- How can EFU be integrated into existing LCA (Life Cycle Assessment) software?
- What regional weighting factors (local water and material scarcity) should be applied?
- How can delayed-effect modelling (e.g. “Ghost Coupling”) be empirically validated?
We invite researchers, professional partners and interested parties to joint publications, data analysis and further refinement of the framework.
If you are not a researcher but curious about the material throughput of your own household in EFU terms, you will find simple calculators and further information on the CitizenScience.eu platform.
Detailed materials are available in the Zenodo archive and on the CitizenScience.eu platform.
Guided Links
- Basics and definition: CitizenScience.eu – Project #836 · Status declaration
- Global material throughput and inequalities
- Sustainability boundary and overshoot
Further information
• European Citizen Science Platform – Project #836: citizenscience.eu
• Status declaration: doi.org/10.5281/zenodo.22066598
• EFU framework: doi.org/10.5281/zenodo.18888082