Material Insights · Understanding the Material World

Waste heat for drying, water and food: Economics and contracts

The whole business case rests on heat being free

What this tab covers Economics and commercial structures: levelised cost of the recovered energy against the fuel it avoids, host-site risk, and service models such as heat-as-a-service.

The economics rest on the heat being free. If it has to be bought at fuel prices, thermal desalination and drying lose against electric alternatives.

Levelised cost of heat or avoided cost

Mixed

Conventional desalinated water costs about USD 1 to 2 per m3, and large modern plants reach about USD 0.5. At 80.6 kWh of heat per m3, paying even a gas price of USD 5.66 per MMBtu (about USD 19 per MWh) would add about USD 1.6 per m3 (calculated), which is why thermal desalination needs genuinely free heat. Solar-heated MED was estimated at USD 2.3 to 2.9 per m3 (2012). For drying, the grain dryer in the Cadmus sample cost about USD 0.27 per therm saved, more than five times the sample average. For carbon capture, a cement study found that using kiln waste heat could cut MEA capture cost from EUR 61.4 to EUR 48.0 per tonne of CO2, and avoidance cost from EUR 84.7 to EUR 57.5, if all recoverable heat were used (the authors judge about 60% recovery realistic; the paper's figures have some internal inconsistencies).128

Desalinated water cost, conventional USD 1 to 2 per m3; about 0.5 for large plants1 Heat cost per m3 if bought at gas price about USD 1.6 (calculated)12 Grain dryer cost about USD 0.27 per lifetime therm2 MEA capture cost at cement plant, without and with full waste heat use EUR 61.4 vs 48.0 per t CO28

Host factory credit risk

Unfavourable

This is a double counterparty risk: the project relies on the host to keep supplying heat and on a buyer for the water, crops, dried product or captured CO2. If the host closes, the user faces a full fuel bill. Contracts need a minimum heat supply clause and a right to install backup heat.

Heat-as-a-service and ESCO models

Mixed

These projects usually rest on a heat supply agreement between host and user, sometimes with an industrial park operator in the middle. Public support is growing: the EU is piloting an Industrial Heat Auction worth EUR 500 million. Real examples: Greencoat Capital backed a GBP 120 million, 29 hectare UK tomato greenhouse project (announced 2019) heated by heat pumps drawing on Anglian Water's water recycling centres, plus waste heat from the gas CHP that powers them, aiming at over 20 t of tomatoes a day; Brevik CCS was built by Heidelberg Materials under Norway's state-backed Longship programme.61114

EU pilot Industrial Heat Auction EUR 500 million6 UK waste-heat greenhouse investment GBP 120 million for 29 ha11

Sources

  1. Water Desalination Using Renewable Energy, Technology Brief I12 IEA-ETSAP and IRENA, 2012
  2. Not Just Hot Air: Low-Cost Decarbonization through Heat Recovery (Zahlan and Talan, Cadmus), ACEEE Summer Study on Energy Efficiency in Industry ACEEE, 2021
  3. Can low-temperature heat in factories be electrified competitively? (commentary, undated; 2024 cost data) IEA
  4. Comparative techno-economic analysis of the integration of MEA-based scrubbing and silica PEI adsorbent-based CO2 capture processes into cement plants (Jaffar et al.), Journal of Cleaner Production 414, 137666 Elsevier (open access, Ulster University repository), 2023
  5. UK: 29 hectares of new tomato greenhouses to use waste heat (trade press) HortiDaily, 2019
  6. Pioneering the transformation to net zero: Brevik CCS project in Norway reaches mechanical completion (press release) Heidelberg Materials, 2024