Just What is Clean Coal?

Some people consider low-sulphur coal to be clean coal. But low-sulphur coal contains more carbon and  while low-sulphur coal emits fewer oxides of sulphur when burned, it emits more carbon dioxide. Sort of a lesser-of-two-evils thing.

The problem is that while not the cleanest of fossil fuels, coal is the most abundant and cheapest, and energy demand is increasing. Coal will be a part of the global energy future.

Clean coal technology, on the other hand, works to reduce harmful emissions resulting from the combustion of coal. There are several different types of technologies are used in Canada:

• Coal Cleaning – Before the coal is used, it is pulverized and cleaned of impurities, either by chemical means or gravity separation.
• Supercritical Steam Cycles – Advanced materials and fabrication techniques have allowed pulverized coal to be combusted at higher temperatures and pressures, thus increasing the efficiency of the operation. More power can be generated using less coal.
• Fluidized Bed Combustion – Fuel and other particles, such as sorbents, are kept floating by air jets, allowing for more efficient combustion and the absorption of impurities, thus producing fewer oxides of nitrogen and sulphur.
• Gasification – Syngas is created by reacting coal, steam and either air or oxygen at high temperature. The resulting gas consists of carbon monoxide, hydrogen and some impurities. The impurities are removed prior to combustion.
• Carbon Capture and Storage – Carbon dioxide is captured and sequestered either in depleted reservoirs or deep saline formations. With raw coal, the carbon dioxide is captured post-combustion. With syngas, it is captured pre-combustion.

Two coal-fired generation plants in Alberta, Genesee 3 and Keephills 3, use supercritical steam technology. Carbon dioxide emission at Genesee 3 have been reduced by 18 per cent using this new technology. As well, carbon capture and storage has been proposed for Keephills 3 where the captured CO2 will be piped to the Pembina oil field for use in an enhanced oil recovery program.

Coal as Renewable Energy?

Okay, so coal isn’t renewable. BUT, abandoned coal mines can be an alternate source of renewable energy. And that is true!

Take for example, the town of Springhill, Nova Scotia. The coal beneath Springhill provided for a thriving industry from about 1870 to 1962. The town was home to the largest and deepest coal mining operations in North America. The mines were also home to disastrous accidents in 1891 and 1956 and to the Big Bump in 1958, which led to the final mine closure.

Over the years, the abandoned mine workings, some of which extended four kilometres deep, filled with water. At depth, the water is heated geothermally; the hot water rises and mixes with the other mine water. A 140-metre well drilled at the No. 2 Mine brings water at a temperature of 18° C to the surface. Heat pumps transfer the heat to a heating system which provides space and water heating for an industrial park as well as individual commercial buildings and homes. The water is injected into another mine connected to the source mine, where it is heated and the cycle begins again.

In summer, the heat pumps are reversed, and the mine water is used for space cooling. One customer, a large manufacturing operation claims a saving of $45,000 per year in heating costs compared to an oil –fired system.

You can teach an old coal mine new tricks.

Source: Natural Resources Canada, Office of Energy Efficiency
Geothermal Mine Water as an Energy Source for Heat Pumps

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Not All Coal is the Same

It’s all a function of heat and pressure. Coal began as plant remains that accumulated in a moist environment like a swamp or bog. As the bog filled in with sediment, the plant remains were buried. As more sediment accumulated, the depth of burial increased, as did the temperature and pressure. High temperature and pressure reduce the moisture content of the plant remains and increase its carbon content, turning it first into peat, then into lignite or brown coal, then sub-bituminous coal, bituminous coal and anthracite, the highest grade or rank of coal in terms of both carbon content and heating value.

Coal Rank	Carbon Content (per cent)	Heating Value (megajoules/kilogram)	Per cent of World Reserves
Anthracite	86 to 97	Up to 35	1
Bituminous	45 to 86	24 to 33	52
Sub-bituminous	35 to 45	19 to 26	30
Lignite	25 to 35	15 to 17	17

Although anthracite is found in British Columbia and Yukon, it is not mined in Canada.

Bituminous coal is found and mined in British Columbia, Alberta and Nova Scotia, and was mined in New Brunswick until 2009, when the last mine closed. Bituminous coal is used in steel making and in electricity generation. In 2009, about 27.9 million tonnes of bituminous coal were mined in Canada.

Sub-bituminous coal is mined only in Alberta, which produced 24.6 million tonnes in 2009, most of which was used to generate electricity.

Saskatchewan is the only province to mine lignite. In 2009, the province produced 10.6 million tonnes for electricity generation.

Until recently, peat was considered by the Intergovernmental Panel on Climate Change, an organization operating under the auspices of the United Nations, to be a fossil fuel. However, peat bogs contain living, growing plant life, and if harvested properly, are sustaining. As well, peat is carbon-neutral, meaning that the carbon dioxide bound up in the plant while it is growing is released to the atmosphere whether the plant decays naturally or is burned as fuel. Consequently, the IPCC now classifies peat in its own category and as a “slowly renewable fuel.”

Coal – A World Resource

Coal is the world’s most abundant fossil fuel. It provides about 27 per cent of the world’s total energy, second only to oil. It also fuels about 41 per cent of the world’s electricity, more than any other energy source.

According to the Coal Association of Canada, the world’s coal reserves amount to 1,000 billion tonnes, with Canada holding about 10 billion tonnes of that. There is more energy in the world’s coal reserves than there is in its combined crude oil and natural gas. But what makes coal a truly world resource is that about 70 countries have recoverable reserves of coal.

And those that have it, use it!

Eight of the world’s top producers are in the top ten in terms of coal-fired electricity generation. Indonesia and Kazakhstan are the sixth and tenth largest producers of coal, and although most of their electricity generation is coal-fired, they are not ranked in the top ten.

Japan and South Korea are the fifth and tenth largest generators of coal-fired electricity, but Japan does not produce coal, and South Korea ranks 44th in coal production. Canada ranks 14th in coal production and 13th in coal fired generation.

The Energy Information Administration predicts that coal consumption will increase 56 per cent from 132 quadrillion British thermal units in 2007 to 206 quadrillion British thermal units in 2035.

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