The Price of Energy Consumption - The Renaissance of Renewable Energy - page 193

Figure 6.5. Water supply is as integral to the electricity sector as the fuels that are
burned. The power sector's water needs are likely to grow, making water an increasingly
important factor affecting the viability of energy projects. Source: IEA ( 2012a )
(modified).

Human control and use of water resources on a grand scale invariably entails pollution.
The energy industry is the source of various forms of water contamination, ranging from
acid mine drainage (the flow of acidic water from coal or metal mines into rivers and
groundwater) to oil spills. Most of these releases have only localized impacts, and small oil
spills are usually quickly mitigated by evaporation and the action of microbes. Large oil
spills following large tanker accidents or offshore well leaks damage local ecosystems by
killing fish and birds and, less obviously but more profoundly, by coating the ocean floor
with slick that prevents oxygen from permeating the sediments that support the bottom of
the marine food chain.

Finally, we must consider the energy cost of a water supply, which varies from 1 to
4 kilowatt-hours per cubic metre, depending on local conditions. When desalination is
required, for example, in countries such as the Maldives or Saudi Arabia, where demand
for freshwater far outstrips the natural availability, the energetic cost may be as high as 24
kilowatt-hours per cubic metre (Smil 2008 ) .

Table 6.1. Water demands of different activities in the energy industry compared
with the global demand of agricultural crops

Sector l/GJ

Global crop harvest 150,000 l/GJ

Coal mining at surface 2-5 l/GJ

Coal deep mining 20 l/GJ

Oil extraction 5-10 l/GJ

Oil recovery from Alberta tar sands 30 l/GJ