99. "We should switch all our energy to derive from renewable sources."
This is not a practical proposition from the standpoint of either cost or technology. Wind-power is uneconomic without subsidies, and involves huge energy expenditure in construction and maintenance of its wind farms. Rooftop windmills in urban areas, for example, take more energy to produce than they themselves generate. Since winds are unreliable, wind power necessitates huge back-up sources to be on standby.
Solar technology used to use the silicon rejected by the computer industry, but now high purity silicon is being manufactured specifically for power generation. However, this is a heavily energy intensive process, undermining the energy payback from the technology. Although great strides are being made here and it looks as if solar power could be price competitive in a decade, it still won't provide a steady flow of power, nor the concentrations of power needed for industry.
Biofuels currently use food crops such as wheat and maize, and drive up prices, affecting poor people most. The US and the EU have gone for them as an easy option that pleases the farm lobby, but they are not efficient. The crops it takes to fill the tank of a 4x4 with biofuels would feed someone for a year. Many also maintain (Greenpeace and Friends of the Earth amongst them) that they produce more emissions than they replace. If technology can obtain biofuels from plant waste and cellulose, they will be a more viable source, but this might be years away.
A more realistic approach would accompany research into efficient renewable sources with technology to use fossil fuel cleanly so that coal-fired power stations, for example, can capture the carbon produced. Clean fossil fuel technology can give abundant, secure and low-cost energy, which renewable sources currently cannot.
