C remation is a relatively recent option for the deceased in the West. It was first introduced in the 1870s, and was only accepted by the Catholic Church as late as 1963. The idea of incinerating the bodies of their dearly departed is not easy to accept for many people. This is one reason why proposals to recover the waste heat from crematoria for district heating has generated a debate.
“This question raises strong feelings and many people would prefer this topic to be off-limits. I believe it’s all about the picture we have of a loved one becoming ash. To reuse the heat can be seen as much too prosaic and lacking due dignity,” says Claes Hedström, a priest of the Church of Sweden in Uppsala.
The fact that waste heat can be reused as district heat at all is due to recent environmental requirements. The greatest hazard to the environment coming from cremations is the mercury from amalgam fillings, as it is vaporised and, in the worst case, expelled directly into the air. This is why the flue gases are now filtered.
But to be filtered, they must first be cooled down from the cremation oven’s 1,000°C to below 160°C. This is done in a flue gas cooler where pipes with cold water cool the gas. The water in the pipes then heats up. The question is: what should be done with this heated water – let it cool down or reuse it?
“At a cremation, the same routines and the same respect for the deceased are shown irrespective of whether a technical solution is available to clean the flue gas and use the hot water. I see reusing the heat for a district heating system as one way of doing something useful with the energy that is otherwise emitted directly into the air,” says Hedström.
Cremation has become very common in northern Europe, especially in cities. The crematorium at Berthåga, outside Uppsala, handles cremations for the whole of Uppland County – some 2,000 annually. Built in 1965, its two ovens consume 80 cubic metres of oil each year.
CLEVER OR CONTROVERSIAL?
Adjacent to the crematorium there are two chapels and administration buildings, which used to be heated by a local boiler unit using a further 20 cubic metres of oil. Last autumn, the site was connected to Vattenfall’s district heating network in Uppsala. At the same time, the flue gas cooler was connected to the same system.
“We decided to replace the boiler unit with district heat, mainly as it’s much better from an ecological point of view and in line with Church policy on this matter. At the same time, we wanted to see if we could use our energy more efficiently by recovering the heat from the flue gas cleaning unit instead of simply pumping the hot water to a cooling unit on the roof as before,” Tord Engström, manager of Uppsala’s cemeteries, says.
The question of whether it may be seen as lack of respect and unseemly to use waste heat from crematoria for heating has been widely discussed. In Denmark, when it became mandatory to clean flue gases in 2009, the Danish Minister of Ecclesiastical Affairs asked the country’s Ethical Council to decide to what extent such use might be unethical. The Council’s conclusion was that this was not the case.
To begin with, the Council pointed out that cremations are not carried out in order to generate heat, and anyone is free to choose a conventional burial if they wish. Further, they noted that there was no reason to suggest that corpses are used as fuel. In fact, cremation requires heat to be supplied from a source of energy, most often of fossil type, and, ultimately, the flue gases have to be cooled anyway in order to be cleaned (a legal requirement), which results in water being heated. The Council also said that “human beings and organisms return inevitably to the cycle of nature after death” and that there is no real difference in this respect between heat recovery and the decomposition of bodies in the earth after burial.
However, the Council also insists that any revenues generated from heat recovery should be used to reduce the operating costs of the crematorium, so that it is not primarily viewed as a way of generating income.
THE ENVIRONMENTAL FACTOR
At Berthåga, the crematorium and adjacent buildings are connected to the same district heating system, allowing the Church to benefit from lower heating costs during the six colder months. This solution produces major environmental gains. Firstly, the oil boiler was replaced by district heating, which is already very largely based on renewables and will be completely biofuel-fired within a few years. Secondly, the oil consumption of the two crematoria is believed to decrease thanks to heat recovery: “By drawing water from the district heat network into the flue-gas cooler we kan keep the temperature at 70°C when it is not used, such as over a weekend. In this way we don’t have to pre-heat the flue-gas cooler after a standstill and we use less oil,” says Engström.
And for Hedström, as a priest, environmental awareness is self-evident. “The ecological view of the Church comes from its belief in God as the Creator who made human beings in His image. So it’s our duty to act as good stewards of the Earth that we have been given,” he says.