چشم انداز برای تبدیل ذغال سنگ به مایع: تجزیه و تحلیل تعادل عمومی

We investigate the economics of coal-to-liquid (CTL) conversion, a polygeneration technology that produces liquid fuels, chemicals, and electricity by coal gasification and Fischer–Tropsch process. CTL is more expensive than extant technologies when producing the same bundle of output. In addition, the significant carbon footprint of CTL may raise environmental concerns. However, as petroleum prices rise, this technology becomes more attractive especially in coal-abundant countries such as the U.S. and China. Furthermore, including a carbon capture and storage (CCS) option could greatly reduce its CO2 emissions at an added cost. To assess the prospects for CTL, we incorporate the engineering data for CTL from the U.S. Department of Energy (DOE) into the MIT Emissions Prediction and Policy Analysis (EPPA) model, a computable general equilibrium model of the global economy. Based on DOE’s plant design that focuses mainly on liquid fuels production, we find that without climate policy, CTL has the potential to account for up to a third of the global liquid fuels supply by 2050 and at that level would supply about 4.6% of global electricity demand. A tight global climate policy, on the other hand, severely limits the potential role of the CTL even with the CCS option, especially if low-carbon biofuels are available. Under such a policy, world demand for petroleum products is greatly reduced, depletion of conventional petroleum is slowed, and so the price increase in crude oil is less, making CTL much less competitive. Highlights ► We apply an economy-wide model to assess the economics of coal-to-liquid (CTL) conversion. ► Our approach allows us to consider how CTL competes with other conversion technologies. ► We find that without climate policy, CTL may account for a third of global liquid fuels by 2050. ► With climate policy, CTL may not be viable due to high conversion cost and huge carbon footprint. ► Although adding CCS reduces CO2 emissions, the additional cost would make CTL less competitive.

In this paper, we investigate the economics of a coal-to-liquids (CTL) conversion that can be considered a “polygeneration” technology. There are a variety of polygeneration strategies that have been proposed: in general they use gasification and Fischer–Tropsch (F–T) processes to convert a feedstock (e.g., coal or biomass) to liquid fuels, electricity, and other chemicals. As petroleum prices rise such a technology could help meet demand for transportation fuels. The CTL technology has been available since the 1920s. In 1944, Germany’s CTL plants produced around 90% of its national fuel needs (The Coal-To-Liquids Coalition (CTLC), 2009 and Nexant, Inc., 2008). The technology was then, for the most part, abandoned worldwide because of the availability of cheaper crude oil from the Middle East. The only exception was the development of the CTL industry in South Africa beginning in the 1950s. South Africa’s coal-to-liquids industry currently provides around 30% of that nation’s transportation fuel (CTLC, 2009). The high oil prices of 2008 and continuing concern about energy security has renewed interest in more expensive energy supply technologies. For instance, the U.S. and China imported around 58% and 45% of the petroleum they consumed in 2007, respectively (Energy Information Administration (EIA), 2009 and China Industry Security Guide, 2008). In both countries, proponents of CTL argue that they should take advantage of their abundant coal reserves to reduce their demands on imported energy. It is perhaps the combination of both economic and energy security considerations that has made this coal conversion technology under development in China, South Korea, and Australia (Reuters, 2009). A problem of CTL conversion, however, is its carbon footprint in the absence of carbon capture and storage (CCS). Studies by EPA (2007) and DOE, 2009 estimate that CTL without CCS could more than double life-cycle greenhouse gas (GHG) emissions compared to those by conventional petroleum-derived fuels. Environmental concerns are reasons that could hinder the development of CTL industry in more developed countries. On the other hand, according to the aforementioned research done by EPA and DOE, with CCS the CTL conversion would yield about the same or possibly somewhat lower life-cycle GHG emissions than petroleum-based fuels. The added cost of CCS would, however, make CTL harder to compete with petroleum-derived fuels than CTL without CCS does. We focus here on a CTL plant design described by DOE (2007) with the following three outputs: diesel, naphtha, and electricity. This polygeneration strategy of implementing CTL conversion is similar to Mantripragada and Rubin (2011) and Williams et al. (2009). In addition, we include the additional cost of upgrading naphtha to gasoline, and extend the representation of the CTL technology globally by taking into account the regional differences in input and output prices of this technology. Our goal is to investigate the viability of CTL conversion (without or with CCS) in the face of climate policies to reduce CO2 emissions. When, where, and under what conditions will this technology become profitable? Currently, for most research such as U.S. Department of Energy (DOE), 2007 and U.S. Department of Energy (DOE), 2009, a common strategy in analyzing the economics of conversion technologies such as CTL is to assume both the crude oil price and the CO2 price are exogenous. Sensitivity analysis of the results by changing these prices are then provided to see under what circumstances would the technology be viable. While this strategy could provide some preliminary insights, it fails to consider the interactions among different sectors of the global economy, nor does it account for the role of other competing technologies in the global liquid fuels market. To fill this gap, we apply the MIT Emissions Prediction and Policy Analysis (EPPA) model, a computable general equilibrium (CGE) model of the global economy as a tool for analysis. We incorporate the engineering data for CTL conversion from DOE (2007) into EPPA, and formulate the CTL technology as a multi-input, multi-output production function where the output shares of the multiple products can be either fixed or responsive to product prices. We find that without climate policy, CTL may become economic especially in coal-abundant countries such as the U.S. and China starting from around 2015, and in this scenario, this technology has the potential to account for about a third of global liquid fuels supply by 2050. However, climate policy proposals, if enforced, would greatly limit its viability even with the CCS option. In such a scenario, CTL may only become viable in countries with less stringent climate policies, or when the low-carbon fuel substitutes are not available. The paper is organized as follows: Section 2 describes the version of the EPPA model we use, Section 3 presents data on the CTL technology, Section 4 describes the policy simulation scenarios, Section 5 presents the simulation results, and Section 6 provides conclusions.

Due to the significant rise of crude oil prices in recent years, analyzing the prospects for alternative conversion technologies such as CTL has been of great interest. Unlike current research which often relies on sensitivity analysis of the results by changing the price that is exogenous to the analysis, we assess the commercial viability of CTL under the EPPA model, a CGE model of the global economy. Under this framework, we are able to investigate how could different climate policy proposals and the availability of other fuel alternatives influence the future of CTL conversion, and what could be the role of CTL on global liquid fuels supply. We find that without climate policy, CTL has the potential to account for around a third of global liquid fuels by 2050. The viability of CTL, however, becomes quite limited in regions with climate policy due to the high conversion cost and huge carbon footprint. Although adding CCS could reduce CO2 emissions, the additional cost from implementing CCS makes CTL less attractive. The main contribution of our research is to provide a comprehensive and consistent approach to investigate the future of CTL conversion, a strategy which has been discussed intensively especially in coal-abundant countries. In addition, the multi-input and multi-output structure we develop to represent CTL conversion could also be applied to other polygeneration approaches that produce different fixed or variable output shares or that relied on other feedstocks. Thus, future research may explore coal-biomass-to-liquid (CBTL) or biomass-to-liquid (BTL) processes which, while probably having higher conversion costs, could have significant benefit in terms of reduced CO2 emissions.