Wind and Biomass Are Cheaper Than Carbon Sequestration
ralia uses coal to generate 80% of its electricity and those power plants emit 30% of the country’s total GHG emissions, explains Hugh Saddler in ‘Geosequestration: What is it and how much can it contribute to a sustainable energy policy for Australia?’ Oil and natural gas companies are investigating geosequestration as a solution to CO2 emissions, including a large-scale trial at a gas field in the Norwegian sector of the North Sea.
Geosequestration involves injecting CO2 into underground geological formations where it would be stored for hundreds of years. Recent proposals by the Australian government to use geosequestration to reduce GHG emissions to a small fraction of their present level, while allowing continued combustion of coal, “has great superficial appeal,” concedes the discussion paper. “The reality is that Australia will continue to rely on fossil fuels for the bulk of its expanding power requirements, for as long as the reserves last,” but there are other options.
CO2 capture & storage (CCS) from existing power stations would require “large and expensive equipment and use large amounts of energy, thereby reducing overall power station efficiency,” and research has started on new coal utilization technologies to reduce the cost and complexity of capturing CO2, such as integrated gasification combined cycle and oxy- fuel combustion. Transport of CO2 is relatively energy intensive and will require large investments in pipeline infrastructure.
The paper examines the capital and operating costs of a CCS system and its overall thermodynamic efficiency of supplying electricity, as well as the ultimate level of emissions and the large uncertainty in the cost of CCS, “it is clear that coal-fired generation with CCS will be more costly than a number of other low-emission electricity generation options” including wind, many types of biomass and gas-fired cogeneration.
“All these technologies are far more mature than CCS; they are proven, already in widespread commercial use but, also, particularly in the case of wind, likely to fall considerably in cost over time as further experience with the technologies is gained,” it concludes. When the costs of abatement are considered, wind, biomass, energy efficiency and natural gas “are more economically attractive than CCS as abatement options.”
“It is difficult to see how coal-fired power stations, with the additional cost of CCS, will be able to compete with the alternative means of cutting emissions, at least for some decades,” and the report says it does not examine the environmental risks that CO2 may escape from storage sites.
“If gas-fired generation and renewable energy were built instead of new coal-fired generation, to achieve the same cumulative abatement by 2030 as CCS would require only a doubling of the current very modest MRET target,” it concludes. “Scenarios that include more extensive energy efficiency improvements, though still well within identified technical potential, combined with use of gas-fired generation and renewables instead of new coal-fired plant, could reduce emissions in 2030 by more than five times as much as CCS alone, and cumulative emissions by ten times as much.”
The use of CCS alone would reduce emissions by 9% in 2030, and cumulative emissions from 2005 to 2030 by only 2.4%, but modestly-increased energy efficiency could reduce emissions in 2030 by the same amount and cumulative emissions by twice as much, but at “zero or even negative cost.”
The key to these results is that wind, biomass, end-use efficiency and gas-fired generation are currently commercially available, and do not have to wait until 2020, although the paper concedes that CCS may be an effective abatement option after 2030.
“For the foreseeable future, end-use efficiency, gas-fired generation and wind will continue to have lower costs than coal-fired generation with CCS,” it says. “A policy that neglects or excludes other low-emission technologies, in favour of coal with CCS, will place Australia on an unnecessary high-cost path to reducing emissions. This is not an economically optimal policy for reducing GHG emissions from the energy sector.”
CO2 emissions from renewable energy technologies, including wind, bioenergy, hydroelectricity and solar, “are close to zero during operation, although there may be lifecycle emissions if non-renewable energy is used during manufacture,” it explains. One estimate of a 5 MW windfarm in Australia said life-cycle emissions would be 12.2 kg CO2-e/MWh.
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