Refocus Weekly

Lifecycle assessment shows favourable impact of renewables

LONDON, England, 2004-07-28 (Refocus Weekly) Renewables have been shown to have a favourable impact in a lifecycle assessment study from the World Energy Council. The study analyzes all stages of energy production and use for a range of conventional and alternative energy sources from raw materials supply, production, transport and energy generation to recycling and disposal stages.

Comparison of the various renewable energy sources shows greenhouse gas emissions from solar PV are five times higher than wind turbines when calculated on a lifecycle basis. A solar PV module will emit as much as 104 tonnes of CO2 equivalent for every gigawatt-hour of electricity it generates over its 30 year life, according to data in the report, ‘Comparison of Energy Systems Using Life Cycle Analysis.’ The minimum lifecycle emission is 12.5 tonnes. Offshore wind is shown as 22 tonnes, with onshore wind as high as 14.5 and as low as 6.9 tonnes per GWh. Nuclear is 3 to 40; hydro is 4 to 120; gas cogeneration is 398 to 499; and coal emits 800 to 1,372 tonnes per GWh of electricity.

For heating technologies, wood chips are lowest at 10 to 23 tonnes per GWh of thermal energy, followed by earth energy heat pumps at 24 to 105, natural gas at 263 to 302, gas-fired electric space heating at 712 and coal-fired electric at 1,102 t/GWh-t.

“A rapidly growing number of people around the world are becoming concerned about environmental issues” and it is important to examine ways in which negative effects on the environment are assessed, the report notes. The objective of lifecycle accounting is to “describe and evaluate the overall environmental impacts of a certain action by analysing all stages of the entire process from raw materials supply, production, transport and energy generation to recycling and disposal stages.”

Lifecycle evaluation of emissions from energy production and transportation has been the principal target of studies, with some assessments reflecting the large amounts of land required for “dilute” solar and wind resources. “It can also be argued with reason that some of the externalities cannot be covered by the LCA methodology – or any other analytical method – but must be addressed within the political process.”

“In addition to the results of LCA studies, a number of other factors must be taken into account in decision-making on energy systems,” such as long-term impacts from nuclear waste releases and the gradual depletion of primary energy resources, it argues. “Adding LCA to the decision-making process provides an understanding of impacts on human health and the environment not traditionally considered when selecting a product or process; this valuable information provides a way to account for the full impacts of decisions, especially those occurring outside the site, that are directly influenced by the selection of a product or process.”

With renewables, GHG emissions “arise from other stages of the life cycle than power generation,” such as raw material extraction, component manufacture, fuel and material transportation, and construction and dismantling of facilities. The study examined solar PV panels of single-crystalline silicon, multi-crystalline silicon, amorphous silicon and copper indium gallium diselenide cells, where panels are supported by galvanized steel framing on concrete foundations. Emissions from wind turbines depend on the amount of material and work needed to construct the turbines and on load factors.

“In these evaluations, renewable fuels and sources and nuclear compare favourably,” and the environmental performance of fossil fuel use can be improved significantly by using advanced technologies with higher efficiencies, it concludes. In heating, “direct use of fuels compares favourably with electric heating based on the same fuels.”

“Perhaps the most important issue in LCA is the question of time and discounting,” it adds. “This is particularly critical in discussing the greenhouse gas emission problem, since the damage caused by global warming will occur mainly in a rather distant future and will vary with time; thus it cannot be definitively assessed today.”

“It must be remembered that ‘politics will decide’ how and to what extent environmental impacts are ultimately incorporated into economic decisions,” it closes. “Politicians are not making the best of all possible decisions in the best of all possible worlds.”

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