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Reaching the heart of energy production through calculation of life cycle emissions: solar and wind power, hydropower and geothermal and nuclear energy are the cleanest energy sources

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2020-09-25 Karoliina Auvinen

When talking about the climate and energy, many people are doubtful whether bioenergy, wind power or solar power actually reduce greenhouse gas emissions by a very large margin.

The emissions calculations of states and municipalities generally use emission coefficients based on “chimney” emissions, calculating the emissions of solar and wind power, hydropower and nuclear energy as zero. Bioenergy emissions are also usually calculated as zero as the carbon dioxide from burnt biomass is expected to be reabsorbed by growing forests, even though the chimney emissions correspond to those produced by coal and peat.

Many criticise these emission coefficients based on the emissions produced by burning bioenergy and manufacturing solar panels and wind turbines.

The most comprehensive method for reviewing and comparing the emissions of energy sources is the life cycle assessment, the most wide-ranging means of analysing product and production emissions. Life cycle emissions include the emissions from the manufacture, use and waste of devices and raw materials as extensively as possible.

Why, then, have life cycle emission coefficients not become more established in official emission calculations? The primary reasons are that calculating life cycle emissions is complex and laborious and the calculating methods have not been standardised in terms of using initial data. Therefore, the results of case studies often differ considerably, depending on the assumptions and limitations used.

Assessments of life cycle emissions of energy sources

Life cycle assessments have been compiled into reviews containing results from a large number of different studies. The publications of the IPCC and the EU, for example, present a relatively accurate image of the life cycle emissions of energy sources.

The results of the compiled reviews show that the life cycle emissions of wind and solar power, hydropower, nuclear energy and geothermal energy are considerably lower than the emissions produced by fossil fuels and peat. The emissions of bioenergy depend on the development of forest carbon stores and vary in fractions, depending on whether we are talking about biowaste, field biomass or wood. Biomass can be low-emission when the carbon stores of forests and fields are maintained at the same time, or more preferably, when carbon sinks are increased.

However, it is important to note that life cycle emissions do not extensively depict the environmental impact of various forms of producing energy. For example, the method does not account for the disadvantages of radioactive nuclear fuels or the potential damage caused by hydropower or the use of biomass on biodiversity.

Senior Specialist Karoliina Auvinen, Finnish Environment Institute

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