The Global Carbon Capture and Storage Institute (GCCSI) project had reached the following Phase 1 interim conclusions:
- (EOR) was the technology most able to provide the revenue that might facilitate additional Carbon Capture and Storage (CCS) projects.
- The technologies identified as most promising for accelerating cost reductions for capture are Bauxite Residue Carbonation, Urea Synthesis, Renewable Methanol, and Enhanced Coal Bed Methane (ECBM) recovery.
- The CO2 reuse technologies that are most likely to accelerate the uptake of alternative forms of CCS include the mineralisation technologies (such as Carbonate Mineralisation, Concrete Curing, Bauxite Residue Carbonation), ECBM and EOR.
- Mineralisation technologies and ECBM are considered to have greater potential in developing countries where the demand for construction materials in the near term is likely to be high and Coal bed methane extraction is already generating significant interest in with ECBM being a logical means of development.
- EOR and Urea Synthesis are mature technologies already applied on a large scale, yet still have potential for significant growth in the short term.
- Bauxite residue carbonation and renewable are in operation and are close to commercialisation and hence are a potential future market for captured CO2.
- Carbonate mineralisation, and ECBM have the potential to be in commercial operation within 5 years.
The carbon dioxide reuse technologies themselves may consume energy directly or embodied in the equipment used to implement the technology. If these technologies are to show net CO2 storage benefits it is essential that they store CO2 at a higher rate than implementing the technology emits CO2-equivalents (CO2 plus otheremitted – methane, nitrous oxide etc.). This carbon dioxide trade-off can only be assessed using life cycle carbon dioxide (equivalent) assessment.
This report details the further work to conduct a ‘scoping’ life cycle carbon dioxide equivalent assessment (LCA) for each of the reuse technologies to ascertain its validity as an option for net reductions in greenhouse gas emissions. A ‘scoping’ LCA is one which approximately models processes and then uses sensitivity analysis to focus on getting accurate data for the 10–20 per cent of parameters that contribute to say 80–90 per cent of the impacts. In this way, quite accurate results can be achieved very cost-effectively. This is very appropriate for new technologies where the operating parameters are still somewhat uncertain.
This project has adopted an unusual approach to life cycle analysis. Conventionally, LCA measures the environmental implications of producing a product or service, but in this project, we are interested in understanding the quantities of product generated in the use of CO2 as an environmental pollutant. In conventional LCA, we define the product and a functional unit that represents this product. In this case, the functional unit is defined in terms of the use of one tonne of CO2 in the production of products/services. The goal of this study is:
To approximately assess the lifecycle CO2-equivalent greenhouse gas emissions associated with the act of reusing CO2 to produce some product or service, exclusive of any considerations of the permanence of storage in the product or service
The scope of this study is from CO2 source to product/service point of supply, Adoption of this goal, scope and functional unit enables all of the technologies to be directly compared – all consume one tonne of CO2 net of any CO2 equivalents from constructing and operating the processes.
The full details of the methodology are appended.
The report concludes that:
- There is no net benefit of carbon storage for Polypropylene Carbonate production, for Formic Acid production, for Urea Synthesis or for CO2 Concrete Curing in or for Renewable Methanol production in China.
- Net carbon storage for the different technologies is most for Carbonate Mineralisation, then Cultivation, then Enhanced Coal Bed Methane (ignoring the implications of burning the product), then Enhanced Oil Recovery (ignoring the implications of burning the product), then Bauxite Residue Carbonation, then Enhanced Geothermal.
- The project presumes that gas and oil will be recovered, and that urea, formic acid and polycarbonate polymers will be produced and takes no account of additionality or longevity of storage – these aspects being beyond the project scope.
- The project reveals large variations in
- operational and total consumptions (0.32 to 5.5tCO2-e/tCO2 reused); and
- embodied carbon in facilities/equipment (ranging from negligible to 6 per cent of total emissions).
- Greenhouse gas emissions from CO2 capture and pressurisation is a significant factor in several of the technologies assessed. However the emissions vary very significantly depending on the greenhouse intensity of the electricity used for the capture and pressurisation process (ranging from less than 0.2 to over 0.5 tCO2-e/tCO2 reused), which can have a proportionally significant impact on the overall results for several technologies.
- Sourcing of low carbon can significantly alter the total footprint of some technologies. Specifically, the upstream embodied material impacts are significant for Urea Synthesis (68 per cent of the impact from compressed ammonia feedstock), concrete curing (90 per cent of the impact from cement feedstock, primarily due to decarbonation), and Polymer production (94 per cent from propylene oxide feedstock).
- Although data gaps exist in the inventories, sensitivity analysis suggests that none are considered significant enough to alter the overall results from this study.
- Not assessed or included in this study:
- permanence of the captured CO2, e.g. whether the captured CO2 is re-emitted at a later life cycle stage;
- additionality of the captured CO2, e.g. whether the absorption of CO2 would occur in part or completely anyway, such as for example in concrete where CO2 is gradually recarbonated over time;
- marginal benefit in terms of mitigated enhanced greenhouse effect against conventional or business as usual technologies;
- what the consequences are of the CO2 reuse technologies in other environmental impact categories such as water depletion, emission of toxic pollutants or depletion of resources; and
- the financial value of these products or services for the extent to which they payback the financial costs of implementing the technologies.