Question: What can you tell me about how long our current stocks of coal, gas and oil are likely to last and any alternative energy forms that are available?  

Answer: Here are some suggested answers.

1. The obvious starting point is to say that it depends on how much fossil fuels are used. The less we use, the longer they will last. More and more industrialisation all over the world increases their consumption.

However, we assume that you mean how long they will last, if they are used at their current rates.

As far as coal is concerned, the world still has huge reserves which should last for hundreds of years. The demand for coal has not increased as much as predicted, partly due to coal being seen as more of a pollutant than oil or gas and also due to the adverse conditions experienced in mining it. Concerns were also expressed about the effect of acid rain due to the emissions from coal burning power stations. It is possible that given improving technologies, gas will be more cleanly and readily extracted from coal, which would of course, increase its usage and therefore the stocks will not last so long.

Crude oil is being used at an extremely high rate and present reserves could run out in 30 - 50 years time, unless we use less or something is found as an adequate replacement or new methods are discovered to extract the pools of oil which presently cannot be removed.

Natural gas is as exhaustible as the other fossil fuels, however, as the large natural gas fields dry up, new ones are being discovered. But locating these and drilling for them is very costly.


2. There are a number of emerging technologies which could make the petroleum reserves last longer.

Solar energy which can be divided into three main groups - heating and cooling applications; electricity generation; and fuels from biomass.

Heating and cooling: drawing on the heat of the sun to provide hot water and heating for households and industry. In the cooling, which is not widely used, a liquid is cooled by first being heated to a temperature sufficient to drive a refrigeration cycle.
Electricity generation: this can use a variety of technologies which arguably depend on the effects of solar radiation. Windmills, turbines, hydro-electric installations and wave power fall into this category. Photovoltaic cells convert sunlight directly into electricity and used in remote areas, such as orbiting space satellites, but this is costly. Ocean thermal conversion (OTC) generates electricity on offshore platforms.
Biomass: this happens where any solid liquid or gaseous fuel is produced from organic matter. Wood and dung are frequently used as well as other industrial, agricultural and domestic waste.

Geothermal energy: where steam trapped deep in the earth is brought to the surface to drive a turbine to produce electricity.

Synthetic fuels are made from substances found in nature; such as gasohol, a mixture of gasoline and alcohol made from living plants. This is done on a relatively large scale in Brazil.

Nuclear energy: where fission of uranium is used to produce heat which eventually drives a turbine to produce electricity.

There are drawbacks for the environment with most of these, e.g. nuclear energy - the problems of nuclear waste.
With synthetic fuels countries are encouraged to grow cash crops rather than agricultural for food.
Hydro-electricity also can have adverse effects on the environment when dams are built.

Within all this you cannot discount the fact that the industrialised nations have to become more energy aware and make serious attempts at reducing dependency on fossil fuels.