Category Principles, technologies, and impacts

Conclusions

Pacola and Socolow have shown that there are several established ways by which we can hold CO2 emissions at a constant level. Wind, solar, nuclear, carbon capture and storage, and fuel savings in transport are all methods that could make a significant difference soon. However, these all require a determination by governments and a realization by the public to curb our CO2 emissions immediately. The Kyoto Protocol is a step in the right direction but needs all nations to be involved, and the rate of CO2 abatement needs to be speeded up.

If the world carries on as it has been there is the real threat of dangerous climate changes within 100 years. It would be unwise to rely on the lower predictions being correct for global temperatures rises...

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Enhancement of natural carbon sinks

Finally, CO2 reduction can be obtained by enhancing natural sinks on land. Ending deforest­ation by 2055 and replanting some 250 million hectares of tropical forest, or a slightly larger area of plantations, would produce one wedge. When land is tilled for replanting, about half of the stored carbon in the soil is lost, mainly through aeration. Extending conservation tillage, in which seeds are planted without re-ploughing the land, to all the world’s cropland, coupled with using ground cover crops that help prevent soil erosion, would provide a further wedge.

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Increase in carbon-free and carbon-neutral energy

Introducing 700 GWe of nuclear power by 2055 would yield another wedge of C02 reduction. This is about double the total nuclear capacity deployed today. While the public is becoming less opposed to nuclear power, serious concerns remain about safety, waste disposal, and proliferation. The wind turbine generating capacity is currently about 40 GWp, which corresponds to about 14 GW continuous power, assuming a capacity factor of This would need to increase by 50 times over the next 50 years to produce another wedge. There has been public opposition to siting wind farms in some areas due to their effect on the landscape and on the bird population...

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Reduction and capture of carbon emissions

Switching about 1400 GW of power from coal-fired to natural-gas-fired plants would also provide a wedge, since the amount of carbon from gas per kWh is about half that from coal. Of more long-term importance is the identification of a wedge from increased carbon capture and storage (CCS). One technique first produces hydrogen and carbon dioxide from the fossil fuel. The hydrogen is then burnt to provide power, or could be used in fuel cells, and the carbon dioxide is stored underground. Another technique separates the C02 from the flue gas and then compresses it before pumping it underground. Currently, C02 is injected into oil reservoirs to enhance oil recovery (EOR). An increase of about 100 in the amount of EOR would produce another wedge.

Besides storage in old oil and gas reservoirs, ...

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Energy efficiency and conservation

In 2002 transport produced 22% of all CO2 emissions, with industry and buildings producing 36% and power generation 42%. A wedge would be provided by improving fuel efficiency from an expected 30 miles per gallon in 2055, from its present value of just over 20 to 60 miles per gallon, or by reducing the average annual mileage from 10 000 to 5000 miles. Another efficiency wedge could be provided by building more energy-efficient buildings. For

Energy efficiency and conservation

Fig. 11.4 Predicted and proposed carbon emissions using stabilization wedges. Future CO2 levels and temperature rises based on simple linear model (see text).

11.6 STABILIZATION WEDGES FOR LIMITING C02 EMISSIONS

example, installing compact fluorescent instead of filament bulbs could provide a quarter of a wedge.

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Stabilisation wedges for limiting C02 emissions

Stabilization at about 500 ppm requires holding the current emissions of 7 Gt C y"1 constant for the next 50 years, rather than letting them rise to around 14 Gt C y“!, which is roughly the rate expected if we allow the situation to follow the current trend. Assuming the same

Stabilisation wedges for limiting C02 emissions

constant fraction of close to a half is absorbed by the Earth during this period, as has been the case over the last 50 years, then we would estimate the level of CO2 to rise to around 475 ppm. After 2055, Pacala and Socolov assume that the amount of CO2 would fall linearly until there is no net gain per year after 2105. In our simple model the effect of this would be that the level of C02 would stabilize at around 525 ppm.

A fall in the amount emitted each year would be possible if by 2055 we had developed carbo...

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Renewables obligation

A renewables obligation is a mechanism set up in the UK to promote the growth of renewable energy. It requires electricity suppliers to obtain a specified fraction of their energy from generators using renewable energy sources. This fraction will increase to 10% by 2010. The obligation sets up a market in tradeable green certificates (renewable obligation certificates, ROCs). Suppliers have to buy a certain number of ROCs to show that they have obtained the specified fraction of renewable energy. This they can do by buying ROCs directly from the renewable generator or on the open market. Alternatively, they can pay a buyout price of 3 репсе/kWh to make up any shortfall.

Renewable generators of electricity will earn revenue from selling both electricity and ROCs, which will give them e...

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Carbon tax

A simpler scheme to set up than emissions trading is to impose a tax (collected by the government) on all fuels that emit CO2. The tax is based on the amount of carbon emitted, so coal would have a higher tax per kWh than gas. This scheme, which was introduced in Sweden, Finland, The Netherlands, and Norway in the 1990s, provides an inducement for everyone to

11,6 STABILIZATION WEDGES FOR LIMITING C02 EMISSIONS

Carbon taxreduce emissions and applies to transport, domestic consumers, and industrial consumers. It also demonstrates the importance attached to reducing global warming by the government concerned. It is more costly for countries with less efficient energy usage, which was why the United States was in favour of emissions trading rather than a carbon tax.

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