Environmental Engineering Reference
In-Depth Information
The term 'renewable energy' is more complex. Strictly speaking, fossil fuels are
renewable since they are formed from dead biomass. However, the time span of their
formation - millions of years - makes them non-renewable in practical terms. No matter
how carefully or economically we use fossil fuels, they cannot be replaced at the rate
of consumption. Therefore, a more practical definition of renewables might be “any
energy storage reservoir which is being 'refilled' at rates comparable to that of extraction”
(Sorensen 2004 , 17). In the case of biomass fuels, we have the option of consuming them
at the rate they are regenerated. This is the idea behind forest management; the biomass
resourceiscultivated inmuchthesamewayasanagricultural crop,maximising production
while ensuring that the resource remains viable over time.
Solar and wind energy are, strictly speaking, not renewable, but rather inexhaustible, at
least within a human time span. By the time the sun finally runs out of fuel (roughly 5
billion years from now), human beings will have long ceased to exist, at least in our present
form. Solar energy is beyond our control, and we can neither deplete nor cultivate it. The
amount of this energy we harness depends only on our will and ingenuity.
The terms 'renewable' and 'sustainable' are often used interchangeably, but this is also
not quite right. Sustainability is a measure of the effects rather than the means of energy
production. The term entered common use in the 1980s as more people became aware
of the difficulties of reconciling economic growth with environmental protection. The
influential Brundtland Report of the United Nations defined sustainable development in
1987 as “development that meets the needs of the present without compromising the ability
of future generations to meet their own needs” (United Nations 1987 , 41).
Energy that is renewable is not necessarily sustainable, and in recent years many have
questioned the sustainability of some renewables, particularly biofuel production that
competes with food, and wind farms in areas of scenic beauty.
2.3 Fuels: The Elixir of the Industrial Age
Anything that contains mass (in essence, anything we can see and touch) also contains
energy. In a mass-to-energy conversion, mass physically disappears and is replaced by pure
energy. According to Einstein's famous formula, E = mc 2 , if we could fully convert matter
into energy, a tiny pebble weighing a single gram would release 90,000 billion joules or 25
million kWh, enough to meet the electricity needs of a European town of 20,000 people for
a year. If full mass-to-energy conversion were possible, all our energy problems would be
solved.
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