Waste heat for drying, water and food
Low-grade heat put to work drying products, making fresh water and warming greenhouses.
Recovery and reuse · Heat to heat · No. 124
- Recovery and reuse
- Heat grade: Low to medium
Heat too cool to boil anything can still make fresh water, dry grain and grow tomatoes, if it is free.
Chart: Illustration: Waste heat for drying, water and food
Where it comes from
Chart: Map of where it comes from
Drying, desalination, greenhouses and carbon capture can all run on low-grade heat. ORNL estimates about 570 TBtu a year of US industrial waste heat sits below 149 C.
Three things to know
- Multi-effect distillation runs at about 70 C, cool enough to use heat that boilers and furnaces throw away.
- Bought at gas prices, the heat alone would add about USD 1.6 per cubic metre of water, so thermal desalination needs truly free heat.
- Using a cement plant's full waste heat cut carbon capture cost from EUR 61.4 to 48.0 per tonne of CO2.
The journey
- 1 Spare heatExhaust or cooling water from a host
- 2 Heat loopPipes carry it to a neighbour
- 3 End useDesalination, drying, greenhouses, carbon capture
- 4 ProductFresh water, dried grain, tomatoes, CO2
- 5 BackupBoiler on standby if host stops