21 Jul 2018 18:54 IST

Even death is an alternative source of energy

It is time we looked beyond wind and solar when we talk about clean-tech and green energy

The day after my father was cremated, I searched the ashes for a small metallic object — an artificial valve that had kept his heart beating for over 10 years — to preserve his memory. I poked around the hot mixture of ash and bones with a stick but didn’t find the titanium piece. It had melted in the heat!

Disappointed, I walked out of the crematorium with the pot of ash (to be delivered to the sea). At the back of my mind, I wondered how hot a furnace gets when it burns bodies.

That is when I read that it can get as high as 800 degrees Celsius. In which case, could we not find a way to use that heat? How much energy goes to waste!

Debatable idea

Turns out I was not the first to think on those lines.

The Aalborg crematorium in Denmark makes money by selling heat to nearby villages. And Durham Crematorium in the UK makes some electricity from the ‘dead heat’ and supplies it to villages. Another in Redditch, UK, warms waters of a nearby swimming pool with the heat it produces. A Spanish company called Kalfrisa supplies cremation kilns embedded with heat recovery systems.

And this is in Europe, where people prefer burials. In India, the ‘cremation rate’ is higher, at 85 per cent, as compared to the 60-75 per cent (but rising) in Europe. Japan ranks the highest with 99.97 per cent.

The idea of using crematorium heat is not new. But it is a controversial one. Reactions to the idea range from, ‘It doesn’t ring right’ to ‘I’d rather use the heat than see it go up the chimney and warm the sky’.

Can we — I mean, is it morally right to — recover crematorium heat? Sounds like a nice topic for debate, right?

But my point is not to stress that we build heat recovery systems in all our crematoria. My point is, it is time we started looking beyond wind and solar when we talk about clean-tech and green energy.

Identifying sources

Students could, for starters, begin to identify places where there is surplus heat (or other forms of energy). One example is data centres — according to the International Energy Agency, they are mostly powered by renewable energy, but they also produce heat as they work. In Zurich, Switzerland, heat from a data centre built in an underground World War II bunker is used to warm waters of a nearby swimming pool. Pools are excellent candidates for using vagrant heat as they don’t need much of it.

Heat (rather than electricity) produced by burning city waste is another good source of energy. Today, the few waste-to-energy plants we see produce electricity, because that is more easily dispatchable than heat. But if you crack the problem of transmitting heat, you are in money. It can be done.

I have seen a plant in Helsinki, Finland, that burns city waste, uses the heat to produce boiling water, which is sent to a village called Vantaa, some 25 km away. The heat of the water is picked up by the city’s water supply and hot water is pumped to homes.

There will be some heat loss during the transfer, but so what? When it starts at Helsinki, the water is 100 degrees; by the time it is supplied to homes, it is around 65 degrees — which is exactly the temperature people expect tap water to be. You wouldn’t want to open a shower and have boiling water come out, right?

The next wave of green energy could (should) be tapping heat energy from wherever it is available — crematoria to data centres and furnaces in factories. Here lurks an entrepreneurial opportunity for start-ups.

Think about it.

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