How to clean up coal

Coal’s sins of emission are forgiven in Denmark, where the fuel works double time

The twin bogeymen at the Copenhagen climate change summit were the Alberta oil sands, the easy target of the coalition of environmental groups that awarded Canada a string of “Fossil of the Day” awards, and coal. The sooty fuel shared the distinction because it’s the quick-and-dirty fuel of choice for the developing world, notably China, where coal-fired generating plants big enough to light every home in a city the size of Vancouver are opening at the rate of almost one a week.

Globally speaking, coal, not the oil sands, could be the far bigger threat to the health of the planet. Over the next two decades or so, the growth in greenhouse gas emissions from China’s coal use alone is expected to exceed the growth in all emissions from the industrialized world. But in some countries coal is seen as part of the solution to global warming. How can that be?

The Danes have figured out how coal, used the right way, can bring down emissions significantly. So have the Finns, the Dutch and the Austrians. Canada, where coal is still a big part of the electricity-generation mix, should take note.

Denmark’s green image belies its addiction to coal, which generates about half its electricity. The Danes don’t feel guilty about running the grubby coal plants because they also supply most of the heating for the country’s 5.5 million citizens. This thanks to a marvellous technique called district heating that has actually been around for decades.

Any coal plant makes two things—electricity and heat. In most coal burners, the heat is sent on its merry way up the smokestack. In Denmark’s combined heat and power (CHP) plants, the biggest of which are coal-fired, most of the heat is captured and used to heat water, which is pumped through a vast network of super-insulated pipes to homes throughout the country. At last count, the CHP plants supplied 53% of Denmark’s electricity and 81% of its district heating. In areas where district heating is available, electric heating is forbidden.

Coal plants that make both electricity and hot water are extraordinarily efficient, even if the plants are geezers. A natural gas plant is about 35% efficient, meaning about two-thirds of the energy produced by the fuel is wasted as heat. Denmark’s best CHP plants claim an efficiency rating as high as 90%.

Besides bringing down heating costs for Danes, the district-heating system is taking some weight off Denmark’s carbon footprint (its carbon dioxide emissions have fallen by 13% since 1990). That’s partly because district heating displaces individual electric, gas and oil furnaces whose collective emissions would have been far higher—the reduction in fuel consumption is about 30%, according to the Danish government. And that may not be the limit: Aldyen Donnelly of Vancouver’s WDA Consulting, an emissions consulting firm, estimates that district heating can reduce greenhouse gas emissions from home heating by as much as half.

District heating of the steam (not water) variety used to be fairly common. The New York Steam Co. started to heat Manhattan office buildings in the 1880s. In the same decade, London, Ontario, used it to heat government, hospital and university buildings. The systems are fairly rare today.

But they may be poised for a comeback, even though $1.5 billion (U.S.) intended to finance new district-heating systems was dropped from Barack Obama’s economic stimulus package last year. A recent U.S. Department of Energy report said an aggressive push into CHP plants could attract $234 billion (U.S.) in investments by 2030, create nearly one million jobs and reduce greenhouse gas emissions by 848 million tonnes a year, the equivalent of taking more than half of American passenger cars off the road. And both climate-change bills before U.S. legislators—Waxman-Markey and Kerry-Boxer—have given their blessing to coal-based district heating. Each bill proposes to make the plants exempt from any emissions cap once age reduces their electricity output to 33% or less of normal capacity, as long as the heat thrown off is put to good use, like making hot water.

Which brings us to Canada. Ontario alone has five fossil-fuel plants—four coal, one gas-oil hybrid—and wants to shut them down. Maybe one or two of them could be reinvented as double-use electricity and water-heating plants, bearing in mind that Canada’s low population densities mean district heating isn’t suitable for many areas. Interestingly, Canada is already a pioneer in the district-cooling business: Enwave Energy takes cold water from the bottom of Lake Ontario and uses it to keep downtown Toronto buildings from baking in the summer. The company also runs a district heating system. So obviously we have some alternatives. Shutting the coal plants before figuring out whether they could be used to heat cities would be a mistake. Let’s hope China has the same idea.