Statoil has for many years worked to develop technology and processes to meet the climate challenge associated with extraction and use of fossil-based energy carriers. The debate regarding CO2 capture, transport and storage has mainly focused on technology and economy, and a complete environmental analysis for a Norwegian case has not been available. This is why Statoil in 2007 decided to comission a Life Cycle Assessment (LCA) of a possible future Tjeldbergodden gas power plant case, including CO2 capture, transport and storage (CCS).
The strength of an LCA is the holistic perspective from ‘cradle to grave' (the analysis includes all of the activities throughout the whole value chain) and the inclusion of several environmental impact categories.
The project will give useful information regarding improvements in the design of the CCS system. The model made is now being used in an iterative process and will provide information about the environmental improvements possible with suggested improvements in design, and is thus an useful ecodesign tool for StatoilHydro's CCS system development.
Ostfold Research is a private research company in Norway, with high level competence on holistic environmental assessments. Ostfold Reseach has previously carried out life cycle inventory studies of platform-based production of oil and gas in the Norwegian sector and LCAs of gas power plants at Kårstø and Kollsnes.
2. Aim and functional unit
The aim of the study is to compare the environmental impacts of four different gas power plant scenarios and by this give input to future strategic choices in StatoilHydro. The model developed is to be the basis for scenarios and will thus be an ecodesign tool for StatoilHydro in their CCS development process.
The functional unit is 1 TWh electricity generated at Tjeldbergodden gas power plant and delivered to the grid.
3. System boundaries and project design
The four scenarios analysed:
· Reference Gas power plant without CCS
· CCS-1 Gas power plant with CCS, separate gas fuelled steam boiler for amine regeneration
· CCS-2 Gas power plant with CCS, separate biofuelled steam boiler for amine regeneration
· CCS-3 Gas power plant with CCS, steam from steam turbine for amine regeneration (process integration)
In these four scenarios, natural gas from the Heidrun field is used in a combined cycle process. The CO2 capture process is based on post-combustion decarbonisation using MEA (monoethanolamine) absorbtion. After the capture process, the CO2 is transported in a 150 km pipeline to storage at the Heidrun licence area. A simplified flowsheet of the gas power plant scenarios is shown in Figure 1.
Figure 1 Simplified flowsheet of the Tjeldbergodden gas power plant case with CO2 capture, transport and storage (four scenarios)
The power plant is designed with two gas turbines of 262 MWnominal each in addition to one steam turbine of 328 MWnominal. The nett power production will be 832 MW for the reference scenario and 789 MW for the scenarios CCS-1 and CCS-2. For scenario CCS-3 the net power will be 702 MW. The nett efficiency of the power plant is assumed to be 59.1% in the reference scenario and 44.8% in the CCS-1 scenario. It is assumed that the CO2 capture fraction will be 90%, or 2.1 million tonnes per year. The capture facility will have emissions of CO2, NO2, MEA and NH3 in addition to waste containing MEA, which is treated as hazardous waste. Construction and demolition of infrastructure such as pipelines, platform, terminal, buildings, turbines and process equipment are included in the analysis. The following environmental impact categories are included: global warming, acidification, eutrophication, photochemical ozone creation potential and cumulative potential energy demand.
4. Data sources
Design information and technical specifications for a suggested StatoilHydro power plant, capture facilities and CO2 transport system at Tjeldbergodden have been available for this study [1, 2]. In addition, data for a future capture facility at Naturkraft's power plant at Kårstø have been used . Literature data from the IEA Greenhouse Gas R&D programme and Statistics Norway have also been useful [4, 5].
5. Project status and further work
The project started in spring 2007, and in phase I, two different gas power plant scenarios were compared. In phase II, which started in September 2008, two additional scenarios will be analysed. This work will be complete in the spring 2009, enabling the authors to present details, assumptions and results at the JAOCC conference.
Preliminary results indicate that the carbon capture facility will significantly decrease the greenhouse gas emissions from the system, but that the efficiency penalty will lead to an increase in the other environmental impact categories. In addition, it is possible that airborne emissions of MEA and NH3 from the carbon capture facility will increase the potential acidification and eutrophication impacts. It is also likely that using a separate biofuelled steam boiler and steam extraction/process integration (scenarios CCS-2 and CCS-3) for amine regeneration will decrease the greenhouse gas emissions more than using a separate gas fuelled steam boiler (CCS-1).
 Kvamsdal, H.M., Mejdell, T., Steineke, F., Weydal, T., Aspelund, A., Hoff, K.A., Skouras, S. and Barrio, M. 2005. Tjeldbergodden power/methanol - CO2 reduction efforts, SP2: CO2 capture and transport. Sintef Energy Research, TR A 6062, Trondheim, Norway
 Fluor. 2005. Study and Estimate for CO2 Capture Facilities for the proposed 800 MW Combined Cycle Power Plant - Tjeldbergodden, Norway. A Fluor and Statoil non-confidential report.
 Svendsen, P.T (red.). 2006. CO2-håndtering på Kårstø. NVE-report no. 13 (in Norwegian), ISBN 82-410-0612-8, Oslo, Norway.
 IEA Greenhouse Gas R&D Programme (IEA GHG). 2006. Environmental impact of solvent scrubbing of CO2. 2006/14, Cheltenham, UK, http://www.ieagreen.org.uk
 Hoem, B. (red.) 2006. The Norwegian Emission Inventory 2006. Statistics Norway 2006/30, ISBN 82-537-7061-8, Oslo, Norway, http://www.ssb.no/emner/01/04/10/rapp_emissions/index.html