Why sustainable energy matters
Why sustainable energy matters

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Why sustainable energy matters

6.2 (a) 'Cleaning-up' fossil and nuclear technologies

This means mitigating some of the adverse 'environmental' consequences of fossil and nuclear fuel use through the introduction of new, 'clean' technologies that should substantially reduce pollution emissions and health hazards. These include 'supply-side' measures to improve the efficiency with which fossil fuels are converted into electricity in power stations; cleaner and more efficient combustion methods; the increasing use of 'waste' heat in combined heat-and-power schemes; and 'end of pipe' technologies to intercept and store pollutants before they enter the environment. This approach also includes 'carbon sequestration' (Box 3) and 'fuel switching' – shifting our energy use towards less-polluting fuels, for example from coal to natural gas. It may also be possible to 'clean up' nuclear power by adopting more advanced technologies that are safer and entail the emission of fewer radioactive substances over the entire nuclear fuel cycle.

Box 3: Carbon sequestration

One way of mitigating climate change that could be important is called 'carbon sequestration'. To sequester means to 'put away', and sequestration of carbon essentially involves finding ways of removing the carbon generated by fossil fuel burning and storing it so that it cannot find its way back into the atmosphere.

One way of sequestering carbon is to plant additional trees which 'soak up' CO2 from the atmosphere while they are growing. However, whilst this could provide a partial response to the problem of rising CO2 levels, the sheer magnitude of world emissions is now so great that sequestration in forests alone is probably impractical. It has been estimated that to sequester in trees the carbon produced by world fossil fuel combustion over the next 50 years would require the afforestation of an area the size of Europe from the Atlantic to the Urals (RCEP 2000). Also, when these trees eventually decayed and died, they would emit a similar quantity of CO2 to that which they absorbed during growth, so it would be necessary to replace the old trees with new ones on an indefinite basis.

However wood fuel from fast-growing plantations, managed sustainably, could be harvested and used as a substitute for fossil fuels, instead of simply being allowed to grow to maturity and then decay. This would offset the carbon emissions that would otherwise have been generated by burning the fossil fuels.

Another approach to sequestering CO2 is to extract it after combustion in, for example, a power station and store it in some suitable location. It appears to be technically possible to transport by pipeline large quantities of post-combustion CO2 and store it indefinitely in disused oil or gas wells or in saline aquifers beneath the sea bed (Figure 55). Further research is required to confirm the feasibility, security, safety and economic viability of such techniques. They would only be a realistic option in the case of power stations or similar large installations: it would hardly be practicable to apply this approach to emissions from vehicles or homes.

Figure 55: Norwegian Statoil's Sleipner field project. Gas from this field has a very high CO2 content. Excess CO2 is pumped into a saline aquifer, the Utsira formation, about 800 m below the sea bed. A million tonnes per year of CO2 are 'sequestered' in this way

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