Alternate Energy Sources

Coal

Coal is another fossil fuel like oil and gas but created from vegetation (mainly from the Carboniferous Period) that was compressed under pressure at the bottom of swamps, initially creating peat. Much of this peat later turned to coal. There are several forms of coal with varying amounts of carbon, ash and volatile matter. Some of these forms are listed below (with wood and peat for comparison).

Disadvantages

Coal is one of the dirtiest of fuels. Burning it produces enormous amounts of ash, and flue gasses containing pollutants such as sulphur dioxide, nitrogen oxides, sulphuric acids and arsenic. It also produces almost twice as much carbon dioxide as gas (for the same heat).

These pollutants can be cleaned out of the system before they are released although this obviously adds an extra expense to the cost. There is also the danger that poorer or less conscientious countries will skimp on these controls.

There is also the environmental, human and energy costs of extracting the coal: subsidence, spoil heaps, miners' death and illnesses. It should be noted that something like 50% of the energy used to mine coal comes from oil.

Advantages

The biggest advantage of coal is that it is far more abundant than oil and gas. There are about 200 years of coal left (but only 100 years if it was used to replace oil and gas). Neither does coal peak like oil although it does have the problem that, as it is used up, the remaining reserves will be harder to mine.

Like oil, large amounts of coal tends to be found within relatively few countries although, generally and fortunately, these are countries which have little oil or gas themselves. This will help to lessen the effects of resource wars (see chart below).

AC1. Reserves by Region

The six countries with the largest coal reserves are the USA (27.1% of the world), Russia (17.3%), China (12.6%), India (10.2%), Australia (8.6%), and South Africa (5.4%).

Coal can also be converted into oil (at a rate of about 3 units of coal to 1 unit of oil (see below).

The Future of Coal

Concerns about global warming will likely restrict expansion of coal until the oil decline becomes severe. Then it is likely that many countries will turn to coal in desperation, particularly those who cannot get hold of oil/gas or who have large reserves of coal themselves. Countries like China and India, with little oil of their own, are most likely to step up coal usage to feed their increasing economies and populations. There is a great danger that they may put the environment in second place.

The increase in global warming though may be tempered by the fall of world population and decline of technological society. The increase in pollution, especially locally, may be the greatest problem.

Coal Liquefaction

Liquefaction is the process of converting one fuel into oil. The most important conversion is from coal to oil because of the vast reserves of coal we presently have (although these reserves would obviously deplete quickly if we started using them in a major way for this process.) Rates of conversion vary but the Chinese have several plants in existence and they report a rate of 3 tonnes of coal to 1 tonne of oil. If we use this factor to compare present coal reserves with oil consumption:

A simple calculation shows that converting all of this coal to oil would produce 80 years of oil (at current rates). But if we look at coal produced in 2004, we have 5,540 million tonnes which would make 1,850 tonnes of oil, only half of the oil consumed. Since the coal produced was used for heating and electricity production, it means that we would have to produce three times as much coal to keep the existing usage and replace oil. The R/P ratio for coal would then drop dramatically.

In reality, not all coal is suitable for conversion and there is still the problem of carbon dioxide sequestration and removal of other pollutants. It would probably be better to use the coal to create electricity and then use that electricity to power vehicles, rather than go through the inefficient process of conversion.

Have a look at the chapter on "Efficiency" for more information.

Remember there is a table of disadvantages on the Alternate Energy Sources page.

Unconventional Oils : Natural Gas : Coal : Nuclear : Renewables : Hydrogen