Energ’Iss, heating the city of Issoire with our casting furnaces

This project, conducted with Dalkia and the city of Issoire, will make it possible to use the waste heat from the foundry furnaces of our industrial site located in the city to heat a large number of city buildings (45 buildings).

Main project's drivers for reducing the greenhouse gas (GHG) emissions

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Energy and resource efficiency

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Energy Decarbonisation

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Energy efficiency improvements

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Improving efficiency in non-energy resources

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Emission removal

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Financing low-carbon issuers or disinvestment from carbon assets

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Reduction of other greenhouse gases emission

Project objectives

The objective is to use the waste heat from our casting furnaces, thanks to the installation of heat capture systems and heat exchangers. This heat recovery will supply part of the city's heating needs via a new network, avoiding the necessary energy consumption (mainly gas).

Detailed project description

Constellium has innovated and invested in systems for capturing and filtering the waste from aluminum casting furnaces. These rejects at 500°C allow to heat the city water at 95°C via heat exchangers.

This allows to heat about 45 buildings (hospital, high school, swimming pool, house…) of the city via a network of 11km. Thanks to the installation of a biomass boiler room, the city of Issoire will be heated by more than 90% renewable energy and will save 4,874 tons of CO2 per year for the region, the equivalent of removing 2,700 cars from the road. – An exemplary energy mix with 90% Renewable and Recoverable Energy, broken down  into 36% wood energy (biomass) and 54% waste heat recovered from the Constellium industrial plant (+ 10% gas to reach 100% and to respond to peak consumption).

Emission scope(s)

on which the project has a significant impact

Scope 1

Direct emissions generated by the company's activity.

Scope 2

Indirect emissions associated with the company's electricity and heat consumption.

Scope 3

Emissions induced (upstream or downstream) by the company's activities, products and/or services in its value chain.

Emission Removal

Carbon sinks creation, (BECCS, CCU/S, …)

Avoided Emissions

Emissions avoided by the activities, products and/or services in charge of the project, or by the financing of emission reduction projects.

Scope 1 – Installation and operation of new equipment.

Avoided emissions : To avoid the CO2 emissions of the city of Issoire thanks to heating provided by our activity.

Quantification : 4874  tCO2eq     (Constellium + heating with biomass)

The project’s installations will allow the recovery and injection into the city’s heating network of nearly 25 GWh of heat per year, 54% of which will come from Constellium (13.5 GWh per year). The biomass heating plant will be able to produce 9 GWh/year with an emission factor of 0 gCO2/kWh (if we exclude the road transport of the biomass).

Key points

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Invested amount

1,3 M€ for the recovery part at Constellium - 14 M€ for the construction of the network + the biomass boiler room (of which 60% subsidy by Ademe and CEE)

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Starting date of the project


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Project localisation

Issoir, Puy de Dôme

Project maturity level

Prototype laboratory test (TRL 7)

Real life testing (TRL 7-8)

Pre-commercial prototype (TRL 9)

Small-scale implementation

Medium to large scale implementation

Economic profitability of the project (ROI)

Short term (0-3 years)

Middle term (4-10 years)

Long term (> 10 years)

Not disclosed

Illustrations of the project

This is a first step that can be followed by others to increase the city’s heating coverage.

Dalkia, the city of Issoire

Dalkia has signed a 20-year public service delegation agreement with the city of Issoire. Dalkia is responsible for building the network of pipes, constructing the biomass and gas-fired boiler rooms that supplement the 54% of heat recovered from Constellium, connecting subscribers, and operating the service on a daily basis.

As part of the public service delegation, Dalkia finances and bears the commercial risk.

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