Awash in garbage

Okay, I admit it—every morning since early August I’ve been bathing in garbage.

Well, not exactly. But a significant portion of the hot water we use for heating, washing clothes and dishes, as well as bathing, is produced from the combustion of municipal waste. In fact, almost everyone living in Uppsala, Sweden, where my wife and I are living right now, gets their hot water this way.

This doesn’t mean that the residents of Uppsala carry their garbage into their basements to burn in a furnace. Instead, people separate the combustibles from the compostables and put them into different bins for pickup by waste collection companies. Further sorting is done and some post-consumer products, including various plastics and paper, are shipped to a heating plant on the outskirts of the city.

There, the garbage is burnt in one of the most advanced furnaces in Europe and the exhaust gases are scrubbed three times before being released to the atmosphere. In fact, because of stringent Swedish air-quality guidelines, the emissions from the facility are some of the lowest (if not the lowest) in Europe.

Of course, emissions aren’t the only products of burning garbage—a great deal of heat is also released. By capturing this heat, the owners of the heating plant can use it to generate electricity or hot water, or both (heating plants that produce both heat and electricity (power) are referred to as combined heat-and-power or CHP plants). If the product is electricity, it is shipped to the consumers by wires, whereas hot water is transmitted around the city in insulated, underground pipes.

These pipes form a district heating network that can span a town or city. In Sweden, about half of all buildings are connected to a district heating network; in Uppsala, about 90 percent of the buildings in the city obtain their heat and hot water from the local district heating plant.

The hot water supplied by a district heating plant does not flow directly from a building’s hot-water taps; instead, it passes through a heat-exchanger that transfers the heat to water that is used within the building. This means that most district heating networks consists of two sets of pipes: one for taking the hot water to the community and the other returning the cooled water (that has passed through the heat exchanger) back to the heating plant to be reheated. Consumers are billed for the volume of hot water they use.

Because most Swedish district heating systems (that is, the network and the central heating plant) use multiple fuel sources to obtain their heat, buildings connected to a district heating network are more energy secure than those with their own furnaces. For example, Uppsala’s district heating system can burn post-consumer waste, wood chips and pellets, peat, oil, and coal—such a wide variety of sources means that a price spike or supply shortage in one fuel source can be offset by one or more others. This wasn’t always the case, the city built a new central heating plant in the 1970s to operate on oil; however, soon after the two oil “shocks” of the 1980s, the plant was redesigned to start burning a variety of products.

District heating systems offer more than flexibility and security in the types of fuels used for heating. A typical thermal power station generating electricity is about 30 percent efficient (that is, it converts about 30 percent of the energy in a fuel into electricity; the remaining 70 percent is discarded as “waste” in the form of heat), whereas CHP plants have efficiencies of over 70 percent (25 percent electricity and 45 percent heat, with only 30 percent waste).

When people hear about district heating, they often ask, if it can be done in other cold countries like Sweden, why can’t it be done in Canada?

In order to be economic, a district heating system requires a certain heat density, that is, a neighbourhood or part of a town must have a minimum heating requirement in order to make the system cost effective. The reason for this is quite straightforward: the installation costs for district heating are quite high and if there is not sufficient demand for the heat, then the economics can make the project unfeasible.

After World War II, the development of district heating in Canada was hindered by the availability of low-cost energy. Inexpensive gasoline encouraged people to drive more, which allowed the development of suburbs with low heating densities. Even in communities with sufficiently high heat density, low-cost fuel oil (and subsequently natural gas) for space heating, blocked the development of district heating systems.

The aforementioned oil price shocks of the 1970s did lead to the development of a small, European-like district heating system in Charlottetown. It uses municipal waste and biomass residue to meet the heating needs of two hospitals, the university and veterinary college, malls, some commercial and retail buildings, and a number of residential buildings.

Despite Canada’s miserable record on district heating, there are two places where it should be considered. The first is in existing communities where there is sufficient heat density to warrant the development of a district heating network. For example, parts of the Halifax peninsula fit this description; however, local politicians recently opted for natural gas instead—given Nova Scotia’s limited natural gas resource, it is unclear why such a decision was made. The other is in new communities, where regulations could specify the required minimum heat densities to justify the installation of a district heating network.

There is one other catch, and that is time. In the late 1940s, the Swedes made a commitment to develop district heating, sixty years later they can be justifiably proud of the fact that about half of the buildings in Sweden are heated by district heating. (In the mid-1980s, a delegation of Nova Scotian politicians visited Sweden to learn more about biomass district heating; they may have visited, but they clearly didn’t do much learning.)

It is generally agreed that the growing world demand for oil, natural gas, and coal will result in production challenges and higher energy prices. District heating offers a way to cushion the effects of energy market volatility; however, if it is going to make a difference, communities will need to act now, building networks in neighbourhoods with the right heat density and ensuring that neighbourhoods meet certain heat density standards. The Swedish experience has shown that it is a long-term commitment.

In the meantime, I’ll continue using water heated by garbage (and other fuels).

Larry Hughes
Atlantic Construction and Transportation Journal, November 2009