Every year, about 986 billion ft3 (28 billion m3) of methane are emitted to the atmosphere from coal mining activities around the world. In several countries, coal mines are tapping this wasted resource, converting it to pipeline gas, heating, or electricity. These revenue-generating uses make such projects cost-effective ways to increase mine productivity and reduce emissions of methane, a potent greenhouse gas.
In the US, projects at 14 coal mines recovered over 46 billion ft3 of methane that would have otherwise been emitted from underground coal mines (2006). Nearly all of this methane was injected to natural gas pipelines after gas treatment. One groundbreaking project mitigates dilute methane from a mine ventilation shaft. At one surface mine, methane is recovered in advance of mining for pipeline injection. Methane is also captured and used from over 30 abandoned underground mines.
Globally, more than 240 operating or planned projects recover and use coal mine methane (CMM), avoiding emissions of over 15 million tpy CO2 equivalent. Such activities are underway in at least 12 countries, including Australia, which hosts many innovative projects.
Image 1: Technology used at an abandoned mine site in Illinois to clean up coal mine methane prior to pipeline injection
Challenges in China
China leads the world in coal production and CMM emissions, with about half of its large, state-owned coal mines considered ‘gassy.’ Despite the enormous potential for recovery and use of CMM in China, the geology of many Chinese coal basins presents challenges for effectively using degasification techniques that are used successfully in the West, and much of the drained gas in China is of medium to low methane concentrations. Nonetheless, China is rapidly developing its CMM resources, with well over 50 projects operating or underway, mostly for power generation but also for uses such as town gas and industrial gas. The world’s largest CMM to energy project, located in Jincheng, Shanxi Province, produces 120 MW of power and will reduce emissions by an estimated 7 million tpy CO2e.
Image 2: Power generation facility in Jincheng, China, the world’s largest coal mine methane to power generation facility (120 MW capacity)
US EPA’s work in China
The US Environmental Protection Agency (US EPA) actively supports CMM project development in China, where it recently conducted three comprehensive, site-specific feasibility studies. One study evaluated a pioneering project to gather, purify and liquefy medium concentration CMM from six coal mines of the Songzao Coal and Electricity Company in Chongqing Municipality. The project will mark the first commercial scale deployment of CMM purification/liquefaction technology in China, producing 170 million m3 of liquefied natural gas (LNG), which will be sold into China’s booming natural gas market. The study recommended optimising the system by using CMM from two remote pumping stations as fuel for new mine mouth power generation facilities with total capacity of 26.9 MW, for use by the mines and the LNG plant. The lead project sponsor, Chongqing Energy Investment Group, has requested approval from China’s central government and is negotiating investment funding. If approved, construction will begin in 2010 and operations in 2012. Total emissions reductions are expected to reach 44.1 million t CO2 equivalent over the 15 year project life. EPA is finalising similar studies at a coal mine in Hebi (Henan Province) and the Liuzhuang mine (Huainan Mining Group, Anhui Province).
Image 3: methane vented to the atmosphere from Shihao coal mine, Songzao coal mines, Chongqing Municipality, China, site of an EPA-funded feasibility study
Coalbed Methane Outreach Program
The Coalbed Methane Outreach Program, a voluntary programme at US EPA, promotes the cost-effective recovery and use of methane emitted from coal mining activities that would otherwise be wasted. Internationally, EPA works through the Methane to Markets Partnership, a public-private initiative that works to reduce methane emissions from four key sectors, including coal mining. The US collaborates with 30 partner countries and over 900 organisations from the private sector to identify and promote cost-effective methane mitigation technologies, practices, and opportunities. The Partnership will host an Expo in New Delhi, India, from 2 - 5 March 2009, to showcase project opportunities and cutting edge technologies and developments.
Author: Pamela Franklin, Team Leader, Coalbed Methane Outreach Program, Climate Change Division, US Environmental Protection Agency.
Read the article online at: https://www.lngindustry.com/liquid-natural-gas/30092009/methane_from_coal_mines_presents_opportunity_to_recover_energy_and_generate_revenues/