The fossil-fuel revolution: Coal and the great transition

1.1 England went first because wood ran short and coal lay close to the surface

By the 16th century England had a problem that every crowded pre-industrial society eventually met: its forests could not keep up. Wood was needed for cooking and heating, for charcoal to smelt iron, for ships, houses and barrels. As the population of London grew, firewood had to come from further away, and transport over land by cart was so costly that the price of fuel in the city rose steeply.

England also had something most countries lacked: coal seams near the surface, many of them close to rivers or the sea. Coal from Newcastle could be loaded onto ships and carried down the coast to London far more cheaply than wood could be dragged in from the countryside. So the switch began at the bottom of the economy, not the top. Households, brewers, dyers, salt boilers, brick and lime kilns and glassmakers moved to coal long before any engine existed, because all they needed was heat.

The result was striking. By around 1700 England was mining most of the world's coal, at a time when the rest of Europe still ran almost entirely on wood, charcoal, muscle, water wheels and windmills. Coal was dirty and smoky, and many people disliked it, but it was cheap and there was a lot of it.

The important lesson is about motive. The first great energy transition was not driven by a new technology looking for a market. It was driven by scarcity and price in an old fuel, combined with the geological luck of an accessible substitute. The new fuel then created the conditions in which new technologies, above all the steam engine, could be invented and pay their way.

• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M5 'Coal and the great transition'
• Smil, Energy in World History (1994) · via Smil Mastery Course, M5 'Coal and the great transition'

1.2 Coal broke the land limit that had capped every earlier civilisation

Coal is plant matter that was buried in swamps, mostly around 300 million years ago, and slowly compressed and heated until much of its hydrogen and oxygen was driven off. What remains is rich in carbon. A kilogram of good coal holds roughly 20 to 30 MJ of chemical energy, against about 15 to 18 MJ for a kilogram of dry wood and less for the damp wood people actually burned.

The bigger difference is not per kilogram but per hectare. A forest is a slow, spread-out collector of sunlight. Managed woodland in a temperate climate might yield a few tonnes of usable wood per hectare per year. To keep a large town or an iron industry supplied with fuel, you needed a great deal of land around it, and that land was also wanted for crops and pasture. Smil calls the ratio of energy flow to land area power density, and wood's is low.

A coal mine reverses this. Seams a metre or more thick contain the accumulated growth of many thousands of years, concentrated under a small patch of ground. A single colliery could deliver as much energy each year as many thousands of hectares of forest. A country no longer had to choose between growing food and growing fuel.

This is the root of the fossil-fuel revolution. Industrial growth before coal always ran into a ceiling set by the land needed for wood, fodder and food. Coal let societies draw on a stock of past sunshine rather than living only on the current year's flow. That stock was huge, cheap to tap at first, and could be moved by water to wherever it was needed.

• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M5 'Coal and the great transition'
• Smil, Power Density: A Key to Understanding Energy Sources and Uses (2015) · via Smil Mastery Course, M5 'Coal and the great transition'

1.3 Energy transitions are slow, national and uneven

It is tempting to imagine that once coal was available, everyone switched. The records show something quite different. Each country made the change on its own timetable, and each change took decades.

In the United States, a country with enormous forests, wood remained the main fuel for most of the 19th century. Coal provided more energy than wood only in 1884. France passed the same point in the late 1860s or early 1870s. Russia did so only during the Soviet period. In much of Asia and Africa, wood, crop residues and dung stayed dominant well into the 20th century, and for hundreds of millions of rural households in India and elsewhere they still matter today.

Add all of this together and the global picture is surprising. The 19th century is remembered as the age of steam, yet for the world as a whole it was still an age of biomass. Fossil fuels overtook wood and other plant fuels in global primary energy only around the start of the 20th century.

Smil draws a general rule from these histories. A new energy source typically needs several decades to rise from a few per cent of a country's supply to a dominant share. In the United States coal took more than four decades to go from 5% to 50%. Oil and natural gas later showed similar timescales. The reasons are practical: mines, ships, railways, furnaces, boilers and stoves all have to be built, financed and learned, and the old equipment keeps working until it wears out. That pattern matters for anyone judging how quickly today's transition away from fossil fuels can run.

• Smil, Energy Transitions: History, Requirements, Prospects (2010; 2nd ed. 2017) · via Smil Mastery Course, M5 'Coal and the great transition'
• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M5 'Coal and the great transition'

See it in the table

Check your understanding

What first pushed English households and workshops toward coal?

Why could a coal mine supply energy that would otherwise need a huge area of forest?

Roughly when did fossil fuels overtake biomass in world primary energy?