In this paper, a regionally disaggregated global energy system model with a detailed treatment of the whole chain of CO2 capture and storage (CCS) is used to derive the cost-optimal global pattern of CO2 sequestration in regional detail over the period 2010-2050 under the target of halving global energy-related CO2 emissions in 2050 compared to the 2005 level. The major conclusions are the following. First, enhanced coalbed methane recovery will become a key early opportunity for CO2 sequestration, so coalrich regions such as the US, China, and India will play a leading role in global CO2 sequestration. Enhanced oil recovery will also have a participation in global CO2 sequestration from the initial stage of CCS deployment, which may be applied mainly in China, southeastern Asia, and West Africa in 2030 and mainly in the Middle East in 2050. Second, CO2 sequestration will be carried out in an increasing number of world regions over time. In particular, CCS will be deployed extensively in today’s developing countries. Third, an increasing amount of the captured CO2 will be stored in aquifers in many parts of the world due to their abundant and widespread availability and their low cost. It is shown that the share of aquifers in global CO2 sequestration reaches 82.0% in 2050.
Avoiding dangerous climate change is an increasingly formidable challenge. CO2 capture and storage (CCS) is now recognized as an important option for mitigating climate change. Research, development, and demonstration for CCS are ongoing not only in developed countries, but also in at least 19 developing countries. Although it has been indicated that CCS has advantages over other CO2 mitigation options in terms of CO2 emissions reduction potential and cost-effectiveness (e.g., [1,2]), there are still major hurdles to widespread deployment of CCS. First of all, it must be proven that CO2 can be permanently and safely stored underground. Second, public acceptance of storing CO2 underground must be gained.
Under these circumstances, identifying in advance the future likely CO2 storage sites is considered to be highly useful in overcoming the above two hurdles. This is because much time and effort can be spent on better understanding the geological properties of potential CO2 storage sites, on giving potential host communities for CO2 storage sites a detailed explanation on the necessity, scope, and safety of the CO2 storage project, and on building a reliable relationship with them. Also, taking into account that an important feature of CCS is that it is capital intensive, this would help all stakeholders (including governments, utilities, and CCS industries) make rational decisions on CCS infrastructure design.
Thus, the purpose of this paper is to derive the costoptimal global pattern of CO2 sequestration in regional detail over the period to 2050 under a stringent CO2 emissions reduction constraint (i.e., a halving of global energy-related CO2 emissions in 2050 compared to the 2005 level). The cost-optimal global pattern of interregional CO2 transportation to CO2 storage sites is also drawn and analyzed under this constraint. These analyses are done by using the global energy system model REDGEM70 (an acronym for a REgionally Disaggregated Global Energy Model with 70 regions) [3,4], which treats the whole chain of CCS in detail.
REDGEM70 is a technology-rich, bottom-up global energy systems optimization model formulated as an intertemporal linear programming problem.
choice of technology options) from 2010 to 2050 at 10-year intervals for each of 70 world regions so that total discounted energy system costs are minimized under constraints on the satisfaction of exogenously given energy end-use demands, the availability of primary energy resources, material and energy balances, the maximum growth rates of new technologies, etc. In the model, price-induced energy demand reductions and energy efficiency improvements, fuel switching to less carbonintensive fuels, and CCS in geologic formations are the three options for CO2 emissions reduction.
Furthermore, in the current version of the model used in this study, there is also a constraint that global energyrelated CO2 emissions in 2050 are to be halved compared to the 2005 level. This constraint is the same as that given in the International Energy Agency’s BLUE Map scenario [1,5]. The model has a full flexibility in where CO2 emissions reduction is achieved to meet this constraint.
Future trajectories for energy end-use demands were estimated as a function of those for socio-economic driving forces such as population and income in the intermediate B2 scenario developed by [
Assumptions on the availability and extraction cost of fossil energy resources are taken from [
In REDGEM70 as shown in
The cost of intraregionally transporting the captured CO2 from fossil-fueled plants to a storage site was estimated to be 24.1 US $2007 per tonne of carbon, assuming that it is transported intraregionally through 250 km of pipeline [8,10]. On the other hand, due to the dispersed nature of biomass feedstocks, the intraregional transportation of the captured CO2 from biomass-fueled plants to a storage site is assumed to suffer from diseconomies of small scale. Based on [
REDGEM70 treats the interregional transportation of CO2 between representative cities/sites in the 70 model regions and is able to determine its cost-optimal evolution path.
The geologic CO2 sequestration options included are enhanced oil recovery (EOR), enhanced coalbed methane recovery (ECBMR), depleted gas-field disposal, and aquifer disposal.