CO2 Footprint of the Norwegian Longship Project

Abstract

An analysis of the CO storage efficiency of the Longship project has been performed using a spreadsheet based LCA tool. Results are presented in terms of the CO2 footprint for each value chain measured in units of “tonnes of CO2 equivalent emissions per tonne of CO2 stored underground”. In other words, the results from the tool show the impact of the implementation and operation of the chain on the CO2 storage efficiency. The work was commissioned by Gassnova, the Norwegian State Enterprise for Carbon Capture and Storage. The work was performed by DNV GL and Carbon Limits The method used is consistent with the principles of ISO 14040 “Life Cycle Analysis – principles and framework” and ISO 14044 “Life Cycle Analysis – requirements and guidelines” and has been designed to calculate CO2 equivalent emissions to atmosphere in a 100-year perspective. The functional unit of the system studied is 1 tonne of CO2 stored, where storage refers to permanent geological storage .as defined in ISO 27914 “Carbon dioxide capture, transportation and geological storage – Geological storage”. The tool is capable of accounting for direct and indirect greenhouse gas emissions of each building block of the Carbon Capture and Storage (CCS) chain for the life cycle of the project. As such, for each building block, all project phases are included (construction, operation, decommissioning for capture and transport – construction, injection, post injection, decommissioning and post closure for storage) and for each phase CO2 emissions from the use of fuel, energy, chemicals, materials and transport are considered. In the Longship project, CO2 is captured from two capture sites, the cement factory of Norcem in Brevik and the waste to energy facility at Klemetsrud in Oslo, transported by ship to a receiving terminal at Naturgassparken near Bergen and further transported in a subsea pipeline to the Aurora CO2 storage license area near the Troll field in the North Sea for final geological storage. Three main value chains have been investigated corresponding to each of the two capture sites individually and one combining the two capture sites all with the same sort of transport and storage. Calculation results are then presented as total CO2 footprint measured in tonnes of CO2 equivalent per tonne CO2 stored for the value chain of each capture site separately and for both capture sites combined. In other words, the results from the tool show the impact of the implementation and operation of the chain on the CO2 storage efficiency. In addition, all three alternatives above are estimated when utilizing the full capacity of the storage infrastructure, 1.5Mt/y by introducing CO2 from other sources. The capture from these other sources are not included in the footprint calculations presented. Generally, the Longship project shows very low CO2 footprint compared to projects studied elsewhere. The 3 main reasons for the low CO2 footprint are 1) waste heat or internal steam is utilized for the CO2 capture processes,,2) the Norwegian electricity mix have a very low CO2 footprint and 3) the project has had high focus on using low footprint energy and fuel alternatives wherever possible. Since both capture sites have an element of biologically based raw materials the impact of BioCCS is also discussed as Longship can lead to net negative emissions.