CCS Roadmap in China
Kejun Jiang, Energy Research Institute, National Development and Reform Commission (NDRC)
Background and introduction
With the rapid development of energy technologies in the 20th century, fossil energy plays an important role in the survival and evolution of human society. Utilization of fossil energy brings conveniences to human beings, but at the same time, it badly destroys the global ecological environment. Heavy exploitation and utilization of coal and other energy resources not only destroy the ecological environment of exploitation areas (energy resource bases), but also contaminate the atmosphere of consumption areas (terminals). Since the 1990s, facing global climate warming and frequently abnormal climate phenomena, such as floods, droughts and typhoons, people have realized the importance of climate. Abnormal climate phenomena are mainly attributed to greenhouse gases (CO2, CH4, N2O, fluorides etc.) emission. And the sustained increase of CO2 concentration in the atmosphere mostly stems from unreasonable use of fossil resources, which has already attracted wide international attention. Generally, pollutant emission control pertains to the method of ‘polluting primarily and controlling subsequently’ that a pollutant is produced in energy utilization and controlled after energy utilization. However, the traditional chain-mode of resource, energy utilization and environment in series brings profound lessons on luxurious waste of resources,low efficiency of energy utilization and intolerable environmental pollution.
To the present, China’s economic development was basically at the cost of excess depletion of resources and indulgence of environmental pollution in the above two stages. Exorbitantly relying on exploiting and utilizing fossil fuels (coal, petroleum and natural gas etc.) and natural resources (water, soil and biomass etc.), then converting them into energy by simple means, e.g. combustion, ultimately utilizing the energy in forms of heat and work, the contradiction among resource, energy and environment is increasingly intensified under the situation of superabundant population and relatively scarce resources in China. In China’s present energy consumption structure, coal, petroleum and natural gas occupies 68%, 23.45% and 3%, respectively, which determines that the coal-dominating energy consumption structure will be unchangeable in short order. Taking an example fromthe coal-fired power generation industry in China, the installed capacity of power generation is augmented annually to satisfy rapid economic development, and the total installed capacity reached 500 million kilowatts in 2005, in which new installed capacity exceeded 60 million kilowatts. Consequently, the emission of pollutants remains at ahigh level. On the basis of the relational statistic, 70% of soot emission, 90% of SO2 emission, 67% of NOX emission and 70% of CO2 emissions come from coal combustion. In addition tothe pollutant emissions in the process of energy consumption, a large number of harmful gases are also yielded in the processes of exploitation, refining and supply, which badly impacts the ambient air quality. The tenth Five-Year (2001~2005) Plan indicated that main pollutant emissions should decrease 10% in the five years. However, according to 2005statistics, a large amount of pollutant mitigation, such as soot and chemical oxygen demand, did not achieve anticipated goals. Among the most severely-polluted 20 cities listed on World Bank’s development report, 16 are in China. According to the environmental sustainable indexes promulgated by the World Economic Forum in Davos, Switzerland，China ranks 133rd among 144 countries and regions. The World Bank predicted 390 billion dollars would be neededto treat diseases caused by coal-fired pollution in 2020, which is the equivalent of 13% of China’s GDP. The social effects of pollution appearing in the middle and late periods of industrialization in developed countries have taken place in China as well, which induces greater polarization between the wealthy and the poor and incites more sharp social conflict.
Greenhouse gas causedby human activities are mainly comprised of CO2 emission from combustion of fossil and biomass fuels, CH4 emissions and leakage from exploitation of fossil resources, emissions from industrial production, emissions (CH4) from agriculture and farming, and the reduction of CO2 absorbers such as vegetation. In fact, fossil fuels are the dominant forms of energy utilization in the world (86%), which account for about 75% of current anthropogenic CO2 emission sources (IPCC, 2001c). Thus, the mitigation of CO2 released from fossil fuel combustion will be the focus of CO2capture and storage (CCS).
At present, the options forreducing net CO2 emissions to the atmosphere include:
Changing the energy structure, switching to low-carbon fuels, e.g. natural gas instead of coal, increasing the use of renewable energy or nuclear energy, which emits little or no net CO2;
Technological solutions, involving reducing energy consumptionby either increasing energyconversion and utilization efficiency, or capturing and storing CO2with sequestration technologies;
Sequestering CO2 by enhancing biological absorption capacity in forests and soils.
As a key driver of development in modern society, fossil fuels (mainly including coal, natural gas and petroleum) play an important role in supplying energy. Chemical energy of fossil fuels can be converted into physical energy through combustion, and then may be used in different forms like electricity and work. However, accompanying the combustion process, a large amount of CO2isproduced because most energy carriers in fossil fuels are carbon and hydrogen. Along with the distinctionincomponents, heat values and utilization technologies, the characteristics of CO2 emissionsfromdifferent fossil fuels are various. The carbon content of coal is 0.024kg/MJ~0.026kg/MJ, which is the highest level among fossil fuels. thismeans that 0.08kg~1.0kg CO2is generated when coal is directly burnt resulting in arelease of1MJ heat.Another important form of fossil fuel is which is mainly composed of CH4. The carbon content of natural gas isabout 0.015kg/MJ, which is only about half of that in coal. Natural gas is much cleaner than coal from the viewpoint of CO2 emission. In addition, the average efficiency of coal-based power plants is about 40%; whilethe efficiency of natural gas-based combined cycle can be as high as 58%. As a result, with 1kWh electricity output, 0.35kg CO2 will be released in natural gas-based combined cycle, far lower than 1kg CO2 emission in conventional coal-based power plants. Conclusively, conversion of high-carbon fuels to low-carbon fuels will be cost-effective where an appropriate supply of natural gas is available.
Known as zero-emission energy resources, nuclear energy and most renewable energy do not emit any CO2 in their conversion and utilization processes. The application of bio-energy, whose carbon element comes from atmosphere during the growth of plants, will not increase net CO2concentration in air. So bio-energycan also be considered as a kind of clean energy resource. Furthermore, if CO2 produced in a bio-energy utilization process can be captured and stored, net removal of CO2 from atmosphere can achieve. The overall effect is referred to‘negative net emission’, an innovative concept that has attractedwide attention among European policy makers.
It is apparent that an energy structure adjustment usinglow-carbon fuelsinstead ofcarbon-concentratedfuels,is a potentialpathway to reduce CO2 emission. However, it is restricted by many factors, including resource structure, technical level and energy safety. China has nearly half of global coal reserves, while holding only has 14.3% of the average global natural gas reserves. This limits the development of natural gas-based combined cycle with high efficiency and low pollutant emission. High costs and technical problems make it impossible that China’s energy structure is shifted to mainly renewables in the short run. CO2 control by the use of energy structure adjustments will be a long-term task.
Besides adjusting energy structure, another important pathway to control greenhouse gases is to improve energy utilization efficiency as well asto exploit CO2technologies of separation, storageand utilization. With anincrease of utilization efficiency, less fossil fuel will be consumed, which will lead to CO2 emission mitigation. However, it will not become the fundamental solution in greenhouse gas control. First, the contributionof the finite increment of efficiency is insignificant; second, with economic development,the increase in energy demand will be much greater than energy consumption reductionsfrom efficiency promotion,which will result ina net increase of CO2 emission. Accordingly, the technical exploitation of separation, storage and utilizationof CO2will be the ultimatesolution to achieve the goal of greenhouse gas control.
Storage and utilization of CO2 provide a receiving terminal for excessive CO2. The CCS process isto separateCO2from flue gas in a combustion system and to compress it under high pressure, thento transport it to the site for storage. So far, a considerable amount of CO2 needs to be captured and stored in order to alleviate climate warming. Some geological reservoirs underground may provide room for CO2 storage, includingformer oil and gas fields which could make a contribution tooffsetting the cost of increasingthe production of hydrocarbons. Considerable potential CO2 storage exists under the sea, however there remain technological problems to address and unpredictable factors to confirm with under sea storage. Anemerging and promising techniqueto recoveryCO2from bio-energy systemsto reach zero-emission is attracting increasingworldwide attention. Some chemical and food industryprocessesalso use CO2 as raw material. In most cases, CO2 should be used and stored in high purity forms. Therefore, separating CO2 from other gases should be the first step of CCS technologies.
About 56% ofthe CO2 emissions caused by fossil fuels combustion (which accounts for 83% of total CO2 emission),comes from power plants, steel industries and chemical production processes,and about 32% and 12%from transportation and daily life, respectively. As the largest sources of emissions, power plants, steel industries and chemical production processes, especially energy industries,which provide steady and centralized sources for CO2 capture, will play a significantrole in greenhouse gas control.
According to the principle of “common but differential responsibility”, only developed countries in AnnexI haveto implementa GHG emissionreduction commitment. However,increasing emissions caused by economic development, is increasing the pressure imposed on developing countries. China also has a lot of CH4 and N2O emissions. CO2 emissionswere 823 million tons in China during the period of 1990~2001, which accounted for 27% of the total global growth in emissions. It is predicted that CO2 emissions in 2020 will be 132% greaterthan in 2001, exceeding the total global emissions from 1990~2001. Although the CO2 emission rate per capita in China is currently lower than the global average, thisfaint superiority will be diminished by 2025. However, due to old equipment, out datedtechniques and high energy consumption intensity, CO2 emissions per unit of GDP in China is higher than the average global level.
Greenhouse gas control will impose asignificant international burdenon the future world. Although China is not requiredto commit to a CO2 emissionsreduction, China should be positive in finding technicalsolutions. Both the U.S. and EU have presented their own technical routes to support their national strategies and international negotiating positions. Comparatively, China will becomepassive in negotiations without a clearstrategic objective and technical route, which willdegradeits internationalstanding, and will retardits sustainable development.
A suitable technical route of greenhouse gas control should be proposed as soon as possible during the processes of industrialization, urbanization and modernization in China, in order to offer a scientific foundation and theoretical support for policy making, and contribute to abating global climate change.
1.Current Status and Challenges
1.1An assessment of present technology
At present, most research is seeking ways to capture CO2 from energy systems with a focus on the CO2 separation process and system integration. For system integration research, three types of approaches for integrating CO2 capture into energy systems have been investigated: post-combustion capture, pre-combustion capture, and oxy-fuel combustion. For example, Andersen and Bolland[8] studied the pre-combustion capture option for a combined cycle using auto-thermal reforming of natural gas. For a coal-based energy system, a pre-combustion capture scheme was investigated by Chiesa and Lozza[9―11]. A comparison between the oxy-fuel combustion cycle and post-combustion capture was presented by Bolland and Mathieu[12]. An IGCC system adopting chemical-looping combustion has been proposed and investigated by Jin and Ishida [13, 14].
Post-combustion capture is generally regarded as a more feasible approach because it can be adopted by existing power plants, but since exhaust gas is diluted by nitrogen, the concentration of CO2 in exhaust gas is rather low, causing considerable energy consumption in the CO2 separation process. Consequently, around 8.0 to 13.0 percentage points in efficiency will be lost due to the energy penalty for CO2 capture in power plants adopting the post-combustion scheme[9,12]. To increase the CO2 concentration before separation, another important scheme, which is pre-combustion CO2 capture, recovers the CO2 before it is diluted in air. To achieve this, extra processes such as shift reaction should be employed. Consequently, the energy penalty for pre-combustion capture is mainly composed of three parts, including the energy consumption caused by the shift reaction, by CO2 separation processes, and the reduction inpower output caused by the decrease in the heating value of fuel gas. Most studies indicate that the thermal efficiency of a system adopting pre-combustion capture will be decreased by 7.0 to 10.0 percentage points.
As mentioned above, most systems have an overall thermal efficiency penalty of nearly 7.0—13.0 percent points for CO2 capture. Therefore, it can be concluded that the high energy penalty is one of the common problems of energy systems with CO2 capture.
An efficiency decrease of a quarter means that the power technology falls back to the level of the last half century, which is unacceptable for apower system. Furthermore, the rise in energy consumption due to CO2 emission control will add to the rapid rising trends of energy consumption.
1.2Current global efforts
China‘s CCUS development will be supported by the following basic conditions: (1) China has many large scaled point emission sources suitable for CO2 capture, mainly in the electricity, cement, steel, chemical industries, etc.; it has the potential to reduce technical costs and facilitate deployment by scaling-up and integration; (2) China has considerable theoretical storage potential. It is estimated from preliminary studies that the potential for geologic storage of CO2 in China is approximately hundreds of billion tons, consistingmainly of saline aquifers, oil and gas reservoirs, coal seams and other geologic bodies; (3) there are multiple approaches for CO2 utilization in China, the potential profit of CO2 utilization may promote the development of other aspects along the CCUS technology chain. Among which, enhanced oil recovery (EOR) utilizing CO2 can improve the recovery and utilization rate of several billion tons of low-grade petroleum resources in China, and it’s capable ofenhancing oil recovery by 10% or more, with a great deal of further development potential.
Meanwhile, as a developing country, China faces challenges from its national conditions and unique geological features in developing CCUS technology: (1) China’s economic and social development level is still relatively low, and is difficult to bear the enormous costs for multiple integrated full-scale CCUS demonstration projects, not to mention the additional energy consumption and costs toscale-up deployment; (2) there exists a matching dislocation between source and sink, the imbalanced development between regions results in emission sources that are more concentrated in the densely populated eastern region, however, the western region hasgreaterpotential for storage; (3) the geologic conditions are complex in China, resulting in more technical difficulties in CO2 storage. In China, the geologic formations for CO2 storage are mostly continental deposits, the geologic formation is complicated, with stronger lithologic heterogeneity and lower permeability, featuring small average thickness and high fault density, therefore, additionalstorage technology will be required; (4) the dense population will also require higher security standards for transport and storage in China.
China has made significantprogress in developing CCUS technology, and launched successful industrial scale CO2 capture demonstrations in recent years. At present, under the guidance of governments, China’s CCUS R&D activities are basically implemented by enterprises, and are jointly participated in by research institutes and universities.
The public funded R&D activities on CCUS are mainly administrated by the Ministry of Science and Technology (MOST),Natural Science Foundation of China (NSFC) and other relevant Ministries. Since the tenth five-year plan period, through many national science and technology programs, including the National Basic Research (973) Program, the National High Technology Development (863) Program, and the National Key Technology R&D Program, Chinahas made systematic advances inCCUS basic research, R&D and demonstrations, targeting the emission reduction potential of CCUS technology, CO2 capture, bio-conversion and utilization, CO2-EOR and geologic storage, which each involve different types of CO2 emission sources, different capture technology paths, and different CO2 conversion and utilization modes. China has also invested considerable funds on the technical development and demonstration of CO2-EOR and CO2-ECBM through the National Major Science and Technology Special Program for “the Development of Large-sized Oil & Gas Fields and Coal-bed Methane”. Moreover, China has actively participated in the Carbon Sequestration Leadership Forum (CSLF), Clean Energy Ministerial (CEM) and other multilateral frameworks for cooperation on CCUS technology, and organized its research institutions and enterprises to participate in a number of bilateral and multilateral cooperation projects, thus effectively promoting the development in related fields. Table 1 shows some public-funded R&D projects and related international cooperation projects.
Table 1 List of Main CCUS Technology R&D Projects and International Cooperation Projects supported by Chinese Government
Project Name / Funding Sources / Execution Time / Main Participating Organizations / Project TypeGreenhouse Gas Enhanced Oil Recovery and Underground Storage / National Basic Research Program（973） / 2006-2010 / Institute of S&T Research, PetroChina, Huazhong University of Science and Technology, Institute of Geology and Geophysics of Chinese Academy of Sciences and China University of Petroleum (Beijing), etc. / Basic Research