Elizabeth Kolbert looked at the Swiss 2,000-Watt Society project in the New Yorker of 7 July. Her interviewees provided estimates of the energy use of the typical Swiss inhabitant. The figures added up to about 5,000 watts. To be clear, this means each person is responsible for about five kilowatts of continuous energy use. This includes home electricity and gas, personal transport, industry, and office. To keep us in the ease and comfort we have got used to we are consuming, directly and indirectly, enough energy to keep two electric kettles boiling continuously, or driving a fuel-efficient car four hours in every day.

This article looks at the composition of energy demand in the UK. The figures are then broken down by sector and by fuel. The numbers are used in the introduction to Ten Technologies to Save the Planet (Profile Books, November 2008), where I try to assess whether we are likely to be able to use technology to reduce fossil fuel demand substantially.

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Over a year, continuous energy use of five or six kilowatts by the typical European means a total consumption of around 50,000 kilowatt hours per person. (A kilowatt hour is power of one kilowatt maintained for one hour. There are 8,760 hours in the year.) The figures for North America are approximately double the European level. Japan is lower than Europe, and the fast-industrialising countries of Asia and elsewhere are lower still, at perhaps a quarter of the European level.

The 2,000-Watt Society project is an initiative to try to reduce European consumption down from five or six kilowatts (5,000 to 6,000 watts) down to 2,000 watts, a reduction of up to two-thirds from current levels. Even 2,000 watts is probably incompatible with stable global temperatures if the world achieved this level and still used fossil fuels. The 2,000-Watt Society project thinks that no more than a quarter, or 500 watts, can come from use of non-renewable carbon fuels.

So the engineers backing the 2,000-Watt Society think that the world needs both to use less energy and ensure that three quarters of the reduced amount of energy supplied to homes and businesses is provided by sources other than fossil fuels. Any sensible set of public policies will certainly try to find ways of reducing the total demand for energy in the modern economy as well as minimising the use of non-renewable sources of fuel. However, some societies may decide that the continuation of normal life requires large amounts of continuing energy use. What really matters is not the precise figure for total energy need but rather that we find the best ways of almost completely phasing out the use of fossil fuels.

It is not just about energy use. Global warming gases are also produced by the way we use the world’s lands. In addition to decarbonising energy use, we will also be obliged to reduce the emissions of CO2 from deforestation and agriculture and radically cut the production of the main other greenhouse gases, such as methane and nitrous oxide, from agriculture.

The table below gives approximate figures for the amount of continuous energy use per person in the UK. This table and the others in this article are generated from numbers contained in the compendious Digest of United Kingdom Energy Statistics (‘DUKES’) published by the UK government.

Table 1

Energy source	Average continuous use per person (watts)
Electricity	1,900
Gas	1,400
Coal	150
Oil	1,650
TOTAL	5,150 (i.e. 5.15 kilowatts)

Of course, electricity is not itself a fossil fuel, but most power is generated from carbon-based sources, of which the most important are gas and coal. In the UK, almost 80% of coal and about a third of the gas used is employed in power stations to make electricity. I have calculated the amount of other fuels used to make electric power and then allocated these numbers to electricity. It is important to do this because much of my book, Ten Technologies to Save the Planet, deals with alternative, non-carbon, means of generating electric power.

Almost half of all energy use is a direct consequence of how individuals run their lives.

Table 2

Energy use by sector	Average continuous use per person (watts)
Individuals at home and in personal travel	2,400
Offices and commercial activities	1,050
Industry	1,700
TOTAL	5,150 (i.e. 5.15 kilowatts)

It may be easier to replace fossil fuel sources in the home and in personal transport than in many industrial applications. For example, in my book, the chapter on electric cars shows how we should be focusing on switching to vehicles powered by batteries. Natural gas use for home heating can be replaced by renewable liquid fuels in fuel cells or by biomass-based district heating plants. Or we can use electric heaters.

Other chapters look at how fossil fuel electricity can be replaced by renewable sources such as wind and solar power. The remaining coal and gas power stations can be equipped with carbon capture plants. The figures below show approximately how the energy directly used by individuals in the UK is split between various activities.

Table 3

Energy use by individuals	Average continuous use per person (watts)
Electricity in the home	650
Gas in the home	850
Car use	550
Aviation	250
Oil use	100
TOTAL	2,400 (i.e. 2.4 kilowatts)

Eight of the ten technologies assessed in the book will help reduce the use of fossil energy sources. Acting together, they can replace the large part of existing energy sources. A single large wind turbine in a good location can typically substitute for the total energy needs of about five hundred people. Of course the wind doesn’t blow all the time, and the chapter dealing with this technology looks in some detail how we can cope with unreliable sources such as this.

Decarbonising our sources of electricity is relatively simple challenge. Renewable electricity is well understood, and we will learn how to capture carbon from power plants, although widespread adoption of the technology is at least a decade off. Combined heat and power plants, whether using renewable fuels such as cellulosic ethanol or woody biomass, will also contribute substantially.

Reducing gas demand by a large percentage is more difficult. The cheapest route will be through improved building insulation but fuel cells and district heating plants will also have a role to play. Additionally, it may make good sense to use renewable electricity and replace gas for heating of homes and other buildings.

Most oil is refined into diesel and petrol and used for transport purposes. We can replace oil with cellulosic ethanol for petrol-driven cars, and switch to electric vehicles for many forms of transport. We will not find it as easy to replace aviation fuel or diesel for heavy vehicles. Although plant-based diesel substitutes can be made from any oil-bearing seeds, biodiesel is problematic because its production generally involves the switch of either virgin forest or crop-producing land. Cutting down forests to make fuel has a substantial carbon cost and reducing the food production area in order to meet the demand for diesel has obvious detrimental effects. It may be that we will eventually be able to create bio-kerosene in huge refineries without using oil seeds as a feedstock, but the search for a sustainable source of jet fuel has made little progress as yet.

Table 4

Energy source	Replacement technologies
Electricity	Renewable electricity (wind, solar, marine) Carbon capture and storage Combined heat and power (fuel cells using ethanol and district heating)
Gas	Combined heat and power (fuels cells using ethanol and district heating) Building insulation technologies
Coal	Most of the relatively small amount of coal not used in power generation is employed in the manufacture of metals. Switching to non-carbon sources is difficult.
Oil	Cellulosic ethanol as transport fuel Electric cars Fuel cells in some commercial vehicles Possibly algae derived from carbon capture plants

In addition to reducing the total amounts of oil, coal, and gas needed, we can expect to see a switch towards electricity and away from the ‘primary’ fuels extracted from the earth’s crust. If our cars are eventually powered by batteries and not petrol, we will need to increase the total amount of electricity generated. Similarly, it may make good sense to heat many of our buildings using electricity, rather than gas or oil.

Table 5

Energy source	Average continuous use per person (watts)	One suggestion to potential future switches between fuels
Electricity	1,900	+100 watts car travel +400 watts home heating
Gas	1,400	-350 watts home heating as some gas heating is replaced by electricity
Coal	150
Oil	1,650	-300 watts as many cars switch to batteries -100 watts as homes switch from oil heating to electricity
TOTAL	5,150 (i.e. 5.15 kilowatts)	-350 watts reduction to 4,800 watts

Why does oil use fall by 300 watts as car travel is powered by batteries, but electricity use only increases by 100 watts? The reason is that cars powered by internal combustion engines are must less efficient than battery powered electric cars at transferring energy into motion. The same amount of driving requires less energy.

The impact of the technologies discussed in my book will depend on the assiduity with which they are pursued, the price of fossil fuels, and the level of any carbon tax. They could replace a large fraction of all existing carbon-based energy use. There are two main exceptions to this conclusion:

Some liquid fuels for transport, particularly including kerosene for aviation.
Large scale heat requirements in industry. Manufacturing processes sometimes require huge amounts of heat. Gas and oil currently provide the large majority of this energy need. Although electricity can substitute for gas and oil in some applications, industry will continue to use fossil fuels.

Table 6

Estimates of how much energy use cannot be conveniently replaced by the technologies discussed in my book	Approximate continuous use per person (watts)
Gas and oil use in industry	315 (50% of current figure for industrial gas and oil use)
Aviation	313
Shipping	100
Heavy road transport	236
Diesel use on railways	16
TOTAL	980 (or slightly less than one fifth of today’s total energy use per person)

So even if we successfully replace fossil fuels in all home uses, we are left with a minimum of nearly 1,000 watts of energy use that is difficult to replace with non-carbon energy. To get to a net figure that corresponds to the 2,000-Watt Society’s recommended level of 500 watts of fossil fuel use, we will therefore need to find ways of offsetting, or counterbalancing, the irreplaceable emissions from transport and industrial use.

We could choose to offset the remaining emissions by ensuring that the total forested area of the planet is continually increased. Reforestation will extract carbon dioxide from the air and trap it in wood. Or we could increase the levels of carbon in the world’s soils. The last two chapters of my book on biochar and soil improvement demonstrate that this is relatively easy and probably not expensive although it will undoubtedly be difficult to organise on a large scale. Of equal importance to the climate change benefits, storing more carbon in the soil will probably improve the agricultural productivity of the world’s land, increasing the amount of food that can be harvested.

How much extra carbon do we need to store in the soil to offset completely 1,000 watts of fossil fuel energy so that the total amount of carbon dioxide in the air remains the same? This calculation is quite simple. Much of the remaining fossil fuel consumption will be of oil (primarily for aviation and heavy road vehicles). 1,000 watts of oil consumption implies a total of 8,760 kilowatt hours a year. This amount of energy would mean using about 800 litres of oil, which would add about 2 tonnes of CO2 to the atmosphere when burnt, containing somewhat less than 600 kg of carbon.

The chapters on soil improvement and biochar in Ten Technologies to Save the Planet suggest that we can reasonably aim to supplement soil carbon levels by 1%. We need less than 100 square metres (ten metres by ten metres) for a 1% improvement in soil carbon levels to offset completely all the emissions from 1,000 watts of a year’s continuous fossil fuel use. Even the UK, which is one of the most densely populated countries in the world, could offset the emissions from 1,000 watts from every person in the country for nearly 35 years by adding 1% to the levels of soil carbon in the country’s soils. In other parts of the world, the numbers would be even more striking: Australia could sequester the carbon from 1,000 watts of fossil fuel use for several thousand years just by improving soil carbon levels by 1%.

No single technology will provide us with the solution. We need to make progress across a number of fronts. I hope that the important conclusion of my book is that technological advances are making it possible for our societies to continue to have access to the ease and convenience of energy without imposing the huge costs of runaway global warming on our descendants.