The Mining Sector and the Kyoto Protocol
The coal mining sector is uniquely positioned to contribute to national and international greenhouse gas emissions reductions strategies in a way that is not widely appreciated.
Canada is moving into a post-ratification phase under the Kyoto Protocol. According to World Bank estimates, worldwide trading in carbon dioxide (CO2) emissions reached 67 million tonnes in 2002 with total market value expected to reach US$10 billion by 2008–when the Kyoto commitment period officially commences.
Some of the early carbon trading initiatives (including those of mining companies) have already achieved success. Now there are new possibilities raised by recent research, which are gaining momentum. These include coal-mine ventilation, coal-bed methane enhancements, and underground coal gasification.
Serious advances in emissions mitigation technologies, measurement and validation as well as estimating the true cost of abatement, have raised the mining industry profile onto the same plane as some of the oil and gas industry projects in recent years.
Some disagreement still exists within the scientific community over what technically constitutes carbon dioxide sequestration. For inclusion within the scope of the Kyoto mechanisms, the term refers to the permanent underground storage of emissions from man-made sources within a host rock. Permanence is further defined as being a “geologically-significant” period of time!
Although the Kyoto Protocol identified six key criteria gases, the focus of attention has been almost exclusively placed upon CO2 as an agent of climate change. Recent communiqus within the greenhouse gas fraternity have begun to concentrate equally upon the significance of methane as a viable medium of exchange. With a global warming potential (averaged over a 100-year period) of 21 times that of CO2, what methane lacks in volume it more than makes up for in its contribution to the greenhouse effect.
The mining sector is well-placed to contribute to national targets and commitments through some recent initiatives that are aimed at treating both above- and below-ground methane.
It has been estimated that ventilation air methane (VAM) from all mining activity on a global scale is in the region of 16.6 billion m3 each year. This equates to approximately 237 million tonnes of carbon dioxide equivalent (CO2-e). (By comparison, Canada’s target for its 6% CO2-e reductions under Kyoto is 240 million tonnes.)
For the big emitters (China, the United States, Ukraine) there are significant benefits to adopting relatively new technologies such as flow reversal reaction technologies. In this process, methane is passed through a heat exchanger and the energy generated from compression and concentration is used for local power generation.
Recent research has been undertaken in which the marginal costs of emissions abatement are calculated for this type of technology (assuming local consumption of the energy produced). The results suggest that approximately two-thirds of all VAM from mine sites could be rendered “avoidable” at a cost of less than $3 per tonne of CO2-e. (For comparison, recent calculations of injecting CO2 directly into deep saline aquifers in the North Sea put the equivalent cost nearer to $18 per tonne.) The advantages of methane recovery from these reversal technologies is that up to 100% of the methane is recoverable with a wide range of concentrations–typically between 0.1% and 2% methane–being acceptable. The United States and Australia are leading the way with colliery projects in which VAM is used as combustion air for a series of internal combustion engines. Canada is well-placed to implement equivalent technologies.
The generation of CO2 as a minor byproduct of the VAM reversal technique offsets the overall benefits, but this could be used to assist in an area that is currently being seen as a critical addition to the fuel mix, coalbed methane.
In British Columbia alone, there are significant reserves estimated at between 90 and 250 trillion ft3 at 2,000-m depth–the largest base of its kind in Canada. The strong affinity of locally-abundant anthracite for CO2, and the scientific certainty of associated methane, is known. In northwest British Columbia the Klappan/Groundhog and Telkwa coalfields are at shallow depths of less than 500 m, with over 150 holes registered in the official database of the Coal Geologist of the New Ventures Branch of BC Energy & Mines. The proximity of existing pipeline infrastructure, provincial highways and the Trans-Canada route strongly support the idea of economically-viable additional pipelines as part of a CO2-injection program.
There are, of course, the “parasitic” costs of compressing the CO2 and raising its temperature/pressure characteristics to a supercritical level at which injection is possible. Below these thresholds, hydrates can form that may plug pipes and injection sites. Research already undertaken suggests that the geologic basins of Western Canada are suitable as receiving strata for injections of sour acid gases (produced in the natural gas sweetening process). The Williston Basin in southern Saskatchewan is currently proving itself as a medium for CO2 sequestration in an enhanced oil-recovery project at Weyburn, sinking gases sourced from a North Dakota gasification plant.
Historically viewed as a high-risk technique, the process of underground coal gasification (UCG) has only been commercially possible in Russia where environmental constraints have not been stringent. The in-situ ignition of sub-surface coal seams capped by impermeable overburden is used to generate usable hot product gas. Recent developments such as the Chinchilla demonstration project in Queensland, Australia, have proven this as a viable technology in the West, operating alongside an active environmental lobby. Although not suitable for anthracite, UCG processes are well-suited to lignite and bituminous types of coal.
Production of electricity from UCG through combined-cycle turbines produces more CO2 than natural gas but much less than conventional coal. The possibilities for CO2 injection within the cavity created by coal excavation are enhanced by lowered operations and maintenance costs for these systems. Proprietary technologies developed through Ergo Exergy in Quebec and licensed to partners including Laurus Energy in Toronto are pushing the envelope in this area.
As the measurement and monitoring phase of the Weyburn CO2 sequestration project in Saskatchewan approaches conclusion, the true costs of CO2 sequestration are being computed. The forestry sector now talks in terms of ‘carbon credits’ and the oil and gas suppliers are trading actively. The potential for the mining sector to contribute to national Kyoto targets is gaining momentum.
Peter Ion is a Vancouver, B.C.-based earth scientist who is a member of the European Emissions Trading Group, closely aligned with national bodies working toward the national Kyoto Protocol targets. He can be reached at [email protected]