District Heating - Fuels

The most common fuel for Swedish district heating consists of resources that otherwise would have been lost. Examples include industrial waste heat and forest byproducts such as branches, tree tops, brushwood, and bark. Out of the total district heating production almost four fifths comes from energy that would not have been utilized if district heating was not available. One of the main advantages of district heating is fuel flexibility.

Waste heat
Waste heat is an example of heat that remains after production of electricity or excess heat from industrial facilities such as paper mills and oil refineries. In some cases industrial waste heat can be fed directly into the district heating grid, in other cases the temperature can be increased with the help of a heat pump.

Another form of waste heat comes from waste incinerator plants where waste that probably would have remained at the dump is burned. In order to utilize energy from the waste, the plants burn the waste that provides hot water to the district heating grids.

It is the same with wood based fuels consisting mainly of remnants after timber cutting, such as tree tops, branches, brushwood, and bark. These remnants would have been left in the forest if they had not been used as fuel for district heating. Many district heating plants also burn chips and wood residues from sawmills, carpentry, and furniture industries, for example.

Continuous improvements
This is not always been the situation. In the early 1980’s the district heating plants used oil for almost 90 percent of their heating requirements although they had already then started to use heat from waste combustion to a small degree.

In 1990 the situation changed dramatically. The use of oil was lowered to less than 10 percent of total fuel consumption. Instead, coal burning became the largest part of the production. Heat pumps became popular; the use of heat from waste burning increased and a lot of heat was produced by electric burners using cheap electricity from nuclear power.

Today, wood burning is the single largest fuel for district heating production while waste heat, heat pumps and heat from waste burning continue to be major contributors. Peat and natural gas are examples of other fuels that have been added the last 20 years.

Some district heating is still produced using coal, but only in connection with electricity production, i.e., power plants. The reason is that heat production using coal is heavily taxed, while electricity production is being favored by lower environmental tax for carbon dioxide emission.

The use of fuel oil in district heating systems is today at about the same level as in 1990. It is difficult to replace oil entirely since it is used for so called peak production, i.e., when it is so cold that heat production has to be increased rapidly. Today oil burning furnaces are primarily on standby or emergency status.

Source: Svensk Fjärrvärme, www.svenskfjarrvarme.se/