Muscle power: Abundance
Billions of people, millions of oxen, little work
What this tab covers How much of this energy there is: the natural flow or stock, the share that could be harnessed, and how much is used today, compared with world primary energy use (592 EJ in 2024).The food that fuels 8.2 billion people carries about 37 EJ a year, around 6% of world primary energy use, but only a small part becomes physical work; some 400 million draught animals still work on farms.
A flow: renewed continuouslyHow much there is
| Measure | Value | Compared with world energy use | Note |
|---|---|---|---|
| World dietary energy supply per person (2022) | 2,985 kcal per person per day (about 145 W, calculated)3 | Up 5% since 2010. | |
| World population (2024) | 8.2 billion4 | Projected to peak at about 10.3 billion in the mid-2080s. | |
| Food energy supply for all people (calculated) | about 37 EJ per year3 | about 6% of world primary energy use | 2,985 kcal (4,184 J each) x 8.2 billion people x 365 days = 37.4 EJ; 2022 supply per person times 2024 population. Supply, not intake, so it includes food wasted. |
| Draught animals working in agriculture | about 400 million animals5 | FAO estimate for the early 21st century. | |
| Farmers by power source | more than 800 million manual; more than 400 million with animal traction; about 30 million mechanised farmers5 | FAO estimate. |
Muscle power is a flow that is limited by food supply and by the number of people and animals. World primary energy use was 592 EJ in 2024 (Energy Institute Statistical Review 2025); the food supplied to humanity is equivalent to about 37 EJ, roughly 6% of that, and the useful mechanical work extracted from it is far smaller because most food energy sustains metabolism and much of the population does no heavy physical work.
In farming the picture is very different: by FAO estimates about two-thirds of the world's farmers still work by hand and about a third use animals, while only about 30 million farm with machines. For them muscle remains the dominant source of field power.