Waste heat for drying, water and food: Impact and additionality

Water and food from waste heat, with a lock-in catch

What this tab covers The impact and additionality lens: direct emission cuts, side benefits for water and air, and the risk of prolonging the life of a polluting host plant.

These uses can turn waste heat into water or food, but the carbon benefit is only real if the heat is truly surplus and the alternative would burn fuel.

Direct Scope 1 and Scope 2 abatement

Mixed

Abatement equals the fuel the user would otherwise burn: a gas-heated greenhouse or dryer avoids about 0.0053 t CO₂ per therm of heat replaced. For water, the comparison is with RO electricity of about 3.5 to 5.0 kWh per m3, so waste-heat MED avoids only the grid emissions of that power, minus its own 1.5 to 2.5 kWh. The grain dryer case cost about USD 52 per tonne of CO₂, far above the sample average of about USD 9. Carbon capture is the largest use by tonnage: Heidelberg Materials' Brevik cement plant in Norway, operating since June 2025, captures about 400,000 t CO₂ a year, half the plant's emissions, with much of the solvent heat coming from the CO₂ compressor and cement process; the available waste heat set the capture size.²¹¹⁴¹²

CO2 per therm of gas replaced 0.0053 t² Grain dryer abatement cost about USD 51.77 per t CO2² Brevik CCS capture about 400,000 t CO2/yr (50% of plant emissions)¹⁴¹²

Water and air synergy

Favourable

Desalination creates fresh water, valuable in water-stressed Indian coastal industrial zones, though it returns concentrated brine to the sea. Putting heat to use instead of rejecting it cuts cooling-water use and warm discharges. Greenhouses can also use the host's CO₂ to boost crop growth if flue gas is cleaned (no figures retrieved).¹

Global desalination capacity share, RO 60%¹

Avoided lock-in

Unfavourable

This is the tile with the highest lock-in risk. A greenhouse cluster, town water supply or carbon-capture unit that relies on a coal plant or refinery creates local pressure to keep that host open. Carbon capture is the clearest case: using waste heat for solvent regeneration lowers capture cost and can extend the life of fossil hosts, though for cement, whose process emissions cannot be avoided by fuel switching, capture may be needed anyway. Brevik cost about EUR 421 million to build, with an estimated abatement cost of about EUR 100 per tonne. Investors should test whether the host is on a credible path to closure or decarbonisation.¹²

Brevik CCS capital cost about EUR 421 million¹² Brevik abatement cost about EUR 100 (NOK 1,150) per t CO2¹²

Sources

Water Desalination Using Renewable Energy, Technology Brief I12 IEA-ETSAP and IRENA, 2012
Not Just Hot Air: Low-Cost Decarbonization through Heat Recovery (Zahlan and Talan, Cadmus), ACEEE Summer Study on Energy Efficiency in Industry ACEEE, 2021
Brevik CCS Facility Profile Global CCS Institute, 2026
Pioneering the transformation to net zero: Brevik CCS project in Norway reaches mechanical completion (press release) Heidelberg Materials, 2024