Underground Coal Gasification

Overview History Underground coal gasification (UCG) Between 1974 and 1989, the U.S. was the converts coal in place (underground) into site of major research and deployment a gaseous product, commonly known as efforts in UCG. This was largely driven by synthesis gas or syngas, through the the OPEC oil embargos and increasing oil same chemical reactions that occur in prices, and ended effectively with the conventional above-ground gasification 1986 drop in oil prices. During this time, plants. It has many of the advantages of there were 33 UCG pilots in Wyoming, conventional gasification with respect to Texas, Alabama, West Virginia, and flexibility in commercial use, but has a Washington. These plants were potentially lower cost and a superior laboratories for major technology environmental profile. UCG could increase developments and validation of cavity coal resources available for utilization growth and gasification models. The enormously by gasifying otherwise Department of Energy (DOE) sponsored unmineable deep or thin coal seams. much of this research, and Lawrence Livermore National Lab was a major UCG may have a cost advantage over participant, managing 50% of the pilot other coal conversion technologies. This plants. advantage may be particularly relevant to the area of carbon dioxide capture and The FSU was the first nation to initiate a storage (CCS). national program of UCG research and development, in 1928. Underground As a result, UCG may not only provide an experiments had begun by 1933 in important avenue for low carbon use of parallel with the experimental and coal in the U.S., but also eventually in theoretical programs. Commercial-scale rapidly developing economies. production of syngas was achieved at UCG technology was first developed in numerous locations and for long periods the former Soviet Union (FSU) in the of time, most notably at Angren, 1920s. The U.S. and Europe also Uzbekistan. The Angren mine began conducted several tests in the 1970s and production in 1959 and still has UCG 1980s. In the 1990s, China began UCG technology in place to produce 18 billion research and development and is cubic feet of gas for the Angren power continuing with this effort. station. By 1996, UCG plants in the FSU had extracted and processed over 17 UCG is currently experiencing a million metric tons of coal. resurgence with the development of a handful of initial commercial start ups in UCG production peaked in the FSU in the the last decade, as well as some mid-1960s, and then decreased in the successful pilot projects. However, a 1970s. It is likely that the discovery of significant research and development extensive natural gas deposits curtailed effort is needed to fully commercialize the support for the UCG effort to build gas technology and make it available for wide- pipelines and other infrastructure. UCG scale use. ceased to be economically competitive with this new gas resource.

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Current Activity • A 300% to 400% increase in recoverable coal reserves is Currently, only a few companies in possible by using coals that are Canada, Australia and China claim unmineable (too deep, low grade, commercial readiness. There is little thin seams); activity in the U.S. The ability to expand • No conventional gasification commercial operations is limited by facilities are needed; hence, experience, know-how, and availability of capital costs are substantially staff with past experience in this area. reduced; In 2007, the South African power utility • UCG with CCS appears cost- Eskom initiated a UCG pilot plant. The competitive with other coal-based results have been extremely positive, and technologies (e.g. super critical Eskom, the Ministry of Coal, and Ministry combustion, IGCC) without CCS; of Energy have announced plans to build • Conventional coal mining is not a a 2,100 MW combined cycle plant to run part of UCG facilities, reducing entirely on UCG syngas. operating costs and surface impacts, as well as eliminating In addition, the XinAo Group (one of mine safety issues; China’s largest private companies and • No coal is transported at the largest natural gas distributor) initiated a surface, reducing cost, emissions, pilot project in 2007. The results have freight congestion, and facility been sufficiently positive to develop a footprint associated with coal 20,000 ton/year coal-to-methanol plant by storage and shipping; summer 2008, and have prompted an • Most of the ash in the coal stays expansion project for a 300,000 ton/year underground, thereby avoiding the coal-to-methanol plant by end of 2009. need for additional syngas clean- up, and the environmental issues Several proposed projects are proceeding associated with ash storage; with lease purchases, exploratory drilling, and local construction. These include • There is no production of some projects in Australia, New Zealand, China, criteria pollutants (e.g., SO2, NOx) India, South Africa, Brazil, Canada, the ,and many other pollutants United Kingdom, and the U.S. In (mercury, particulates, sulfur particular, GasTech announced its plans species) are greatly reduced in to build and begin a UCG pilot in the volume and easier to handle; and Powder River Basin in 2006. In 2007, BP • Commercial UCG applications use and GasTech announced a joint venture substantially less water than in which BP would assess the project for conventional gasification potential sponsorship of the field pilot. technologies.

Limitations/Concerns Key Advantages Even though UCG has a number of UCG has several key significant advantages, the technology has several advantages including: limitations and potential concerns:

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• Siting and operation of UCG have at Chinchilla, Australia in 2000. Also, environmental consequences, operations at the Chinchilla pilot plant including groundwater impacts and employed “clean cavity” technology that ground subsidence. Current flushed contaminants from the reactor knowledge and practice can cavity and treated the waste water after a eliminate or reduce these controlled shut-down. environmental risks.

• While UCG may be technically Solutions to that can be employed to feasible for many coal resources, a protect groundwater impacts include: number of deep seams may be limited by geologic and hydrologic hazards. • Balancing operating conditions to • UCG operations cannot be minimize outward transport of controlled to the same extent as contamination from improperly conventional gasifiers. Many over-pressurized burn zones; important process variables, such • Siting plants where geologic seals as the rate of water influx, the sufficiently isolate the reactor from distribution of reactants in the surrounding strata; gasification zone, and the growth • Selecting sites with favorable rate of the cavity, can only be hydrogeology to minimize estimated from measurements of widespread movement of potential temperatures and product quality contaminants; and quantity. • Isolating UCG locations from • While UCG economics appear groundwater resources (e.g., promising, uncertainties in capital choosing deep seams); and and operating costs are likely to • Removing potential contaminants persist until such time as a and undissolved pyrolysis products reasonable number of UCG-based after the reactor feedstock is power plants are built and gasified. operated. • UCG is not a steady-state process, Surface subsidence can be mitigated and both the flow rate and the using three key steps: heating value of the syngas will vary over time. • Appropriate site selection, including depth and strength of rock volume; Environmental Management • Spacing of UCG reactors to leave walls and pillars between UCG may impact ground-water. Also, the produced zones; and issue of surface subsidence needs to be • Identification and avoidance of addressed. Careful site selection and structural weaknesses (e.g., pre- adoption of best management practices existing faults). for operations will minimize both of these issues. Examples of this include the RM 1 test in Colorado in the 1980s and the pilot

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Carbon Management hazards, and synergies with carbon management remain unexplored. • Detailed Engineering Analysis - Given Carbon management policies will create the relatively minimal experience in further support for UCG. The composition the U.S. with UCG, a detailed and outlet pressures of UCG streams at engineering analysis of each step in the surface are comparable to those from the entire process should be conventional gasifiers; as such, the costs undertaken, along with a thorough and methodologies for pre-combustion economic analysis that includes separation are directly comparable. estimates of the costs at various Conventional post-combustion options stages of development and operation may also be applied to UCG-fired power and a comparison of UCG with other plants. In addition, the close spatial power generation technologies. coincidence of conventional CCS options • Engage with Field Demos – The two with UCG opportunities suggests that pilot plants in China and South Africa operators could co-locate UCG and CCS and the emerging programs in North projects. America and India provide near-term opportunities for investigating key There is also the possibility of storing technical and non-technical concerns. some fraction of captured CO2 in the Also, projects might be pursued subsurface reactor (reactor zone carbon through the Asian Pacific Partnership. sequestration). While this appears to have Public-private partnerships should be many attractive features, there remains investigated. scientific uncertainty and some risk in • Develop Standards – At present, there storing CO2 this way. As such, reactor are no broadly accepted standards for zone sequestration needs additional siting and operation of UCG facilities. research. Commercial development would be facilitated by a 3-5 year research program aimed at providing industry, Conclusions regulators, and decision-makers with The NCC has recommended that DOE the technical basis needed to find should further assess the use of UCG acceptable sites and encourage sound technology. There are multiple possible investments. actions DOE could take, either solely from • Assessing UCG with CCS - These two government action or in collaboration with technologies are fundamentally industry or other nations. The NCC distinct and have their own technical, recommendations include: commercial, and environmental issues. A formal program to assess • Renewed Research Program – Since the incorporation of UCG with CCS 1989, no government agency has would identify potential synergies that sponsored research into UCG could enhance economics and site processes or products. A number of performance. outstanding technical issues, including costs and economics, process engineering, subsurface process monitoring and control, risks and

As a public advisory committee to the Secretary of Energy initially chartered in 1984, The National Coal Council has compiled over 30 reports at the Secretary’s request on numerous issues affecting coal and U.S. energy policy. The factual information in this paper, and the conclusions based thereon, are drawn from these studies and the documents used to compile them, all of which have been submitted to the Secretary of Energy.

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