There is relatively little debate about the carbon footprint from constructing renewable energy production facilities, such as offshore wind farms.
Recently the question has been taken up in Danish parliament, considering the huge investment costs of the possible future energy islands in the North Sea and in the Baltic Sea, and the large offshore wind farms that will deliver electricity to the energy islands for export to shore, trading or the use in producing green fuels.
The debate concerns the question of the carbon payback period.
The carbon payback period is an estimate of how long it will take a project to offset the greenhouse gases emitted as a result of its construction, and begin displacing grid-based electricity generated from non-renewable sources (here as defined by IEMA - the Institute of Environmental Management and Assessment).
The amount of displacement is calculated using the principles of counterfactual analysis, which provides a comparison between what actually happened and what would have happened in the absence of the intervention. Using this approach it is possible to estimate how long a wind farm needs to be operational before it repays its own carbon impact, and also the total carbon mitigated over its life time.
The CO2 payback time for offshore wind turbines will be different from manufacturer to manufacturer and will also differ within the different turbine types.
Manufacturers are working to reduce CO2 emissions in connection with the production of wind turbines. However, in Denmark there is no requirement for the CO2 payback period for wind turbines.
With the Supplementary Agreement on tender frameworks for 6 GW offshore wind and Energiø Bornholm recently entered into in Danish parliament, a broad political majority in the Folketing agreed that in future tenders for offshore wind it will be a requirement that reusable turbine blades must be used, unless market analyses from the Danish Energy Agency show that the requirement will prevent the establishment of one or more of the 6 GW capacity before the end of 2030.
If this is the case, the requirement will instead be that the wings be reused for other purposes at the time of removal.
In addition, it is expected that green electricity and green fuels will in the future be among the primary inputs related to steel production, and so the provision of faster and more renewable energy from offshore wind or other sources themselves will help decarbonize the industry.
