Dear Evil Engineer: Can I save on my energy bills by burning bodies?

Dear Evil Energy-Saving Expert,

Like everyone else – heroes, villains, and morally grey protagonists – I have been thinking a lot these days about how to better manage my outgoings amid this cost-of-living crisis. Already, I’ve implemented plenty of measures of which Martin Lewis would be proud, such as switching to energy-efficient lightbulbs, switching off devices on standby, culling and eating the pet sharks, and sending the kids to work part-time in the local e-commerce order fulfilment centre – but all this has turned out to be trivial in comparison with my ballooning energy costs.

So, I’ve been wondering about whether I could utilise existing resources as fuel to keep down the energy bills a bit. Over the last financial year, I’ve been fulfilling an average of one order per week (and by order, I mean assassination). Unless my client requests a bespoke service, I default to dissolving the bodies in acid baths, but the cost of chemicals is also growing prohibitive. Perhaps I could kill two birds with one stone by feeding the bodies to my home boiler. Would this be a good way to save on my energy bills?

Yours,

A thrifty villain

Dear villain,

Thank you for your letter, which, though not addressed to me, I shall do my best to answer. Burning bodies for heat may come across as morbid to some, but there is plenty of precedent for it, dating back to long before the invasion of Ukraine sent global energy markets reeling and nations scrambling for alternative fuels.

In the early 2010s, Durham County Council carried out a feasibility study into capturing and using waste heat from cremations to generate electricity. This was prompted by an environmental review which concluded its crematorium chimneys were releasing too much smoke into the atmosphere and contributing to air pollution. The study suggested installing two turbine generators in its cremation chambers to provide power for the facilities, selling any excess energy to the National Grid under the feed-in tariff scheme. Engineers estimated that the turbines could each generate 250,000kWh annually from 2,100 services.

Around the same time, Redditch Borough Council in London started using excess heat from cremations to heat pools at a local sports centre, reportedly saving over £14,500 in its annual energy bills.

Excess heat from cremations is also used to meet energy needs in Denmark and Sweden, with many crematoria connected to district heating networks.

It is worth noting, however, that only a small fraction of this useful heat originates from the body itself. Cremation is an incredibly energy-intensive process (the chamber must be heated to above 1,000°C for up to three hours to dry, burn, vaporise and calcify a typical adult body), and the heat harvested comes almost entirely from the gas burnt. We do not burn bodies for the energy; it is simply the case that, given the quantities of energy used in the process of cremation, it would be foolish not to try to capture and use some heat rather than allowing all of it to dissipate into the atmosphere.

That prompts the question, then – is there a way of extracting energy from dead bodies which is more than just an energy-efficiency measure for crematoria? Yes, although it is not as straightforward as chopping up a fresh corpse and popping it in the boiler.
There is no reason why animal carcasses (and this does not exclude humans) cannot be processed for use as biomass. This has been done for thousands of years. The Ancient Egyptians soaked reeds in animal fat to make a predecessor of the candle, while the Romans used tallow to make wicked candles.

A 2014 study described how, in Zhejiang Province, waste pig carcasses from slaughterhouses were collected and heated in a pressure cooker for six hours to render fat to convert into biodiesel. The carcasses were worth $56 per tonne as fuel.

While it makes little environmental sense to raise animals for biomass feedstock, it is a smart way to use animals that have been slaughtered without a better use in mind for their carcasses (in 2013, over 16,000 pig carcasses were found dumped in one of Shanghai’s major drinking water sources). Use of animal carcasses as biomass feedstock seems to be on the rise. For a more recent example, a biomass plant in Denmark announced in 2021 that it would start burning tonnes of dead mink – controversially culled amid concern that the species was harbouring a new coronavirus strain – along with household waste to generate electricity for the grid.
So, several tonnes of dead mink may be worth burning, but how about the occasional human body?

A pig (commonly used as a proxy for humans due to similarities in the properties of their skin and flesh) yields approximately 70 per cent of its overall mass in meat, and 1kg of pork contains around 3,000 calories. So, an adult human weighing 80kg may be expected to yield 56kg of meat and around 170,000 food calories (kcal). This is close to a figure calculated less crudely by US-based dietician Samantha Scruggs, who considered the fractions of fat, protein and carbohydrates of a typical human body.

170,000kcal is equivalent to 700MJ, or 195kWh. The average UK home tends to use around 35kWh per day, so a single human body could theoretically keep your house toasty for more than five and a half days. One body a week, then, if you have access to the infrastructure to turn them into biofuel, could certainly help keep down the heating bills.

Yours,

The Evil Engineer