IT Sustainability Think Tank: The circular economy in the context of the datacentre

In the realm of datacentres, circularity efforts typically focus on the upgradability, refurbishment, reuse and disposal of end-of-life IT products. Heat reuse – the process of capturing the waste heat from datacentre operations for heating purposes at other facilities – is also part of the circularity topic area.

IT teams generally refresh their IT hardware on schedules that vary from one to eight years, with typical refresh rates of three to five years. Refresh rates slowed from 2015 to 2020, but are likely to increase again after the next generation of more energy-efficient datacentre IT equipment began appearing on the market in 2021.

Operators are expected to manage their end-of-life equipment responsibly, maximising the refurbishment and reuse of server, storage and network products; the reuse of components for spare parts; and the reclamation and recycling of critical materials.

Best practice in equipment management is to upgrade or refurbish equipment for reuse in an operator’s own datacentres. Efforts should be made to minimise the percentage of end-of-life equipment sent to landfills. Most countries, states and provinces have laws designed to encourage or enforce recycling and reuse.

Datacentre operators should understand and comply with local regulations governing end-of-life products from their datacentre facilities. They will also need to exercise due diligence to verify that their chosen product recycler(s) manage products and materials as promised and that equipment does not end up in a landfill. Datacentre operators that fail to verify the responsible management of their discarded equipment have faced heavy fines and reputational damage.

The reuse of recovered waste heat from datacentre cooling systems has become a topic of intense interest in many jurisdictions, particularly the European Union. Heat reuse is categorised as a circularity topic, as heat generated in the operation of the datacentre can be captured, recovered and put to a beneficial use heating other facilities, such as offices, swimming pools and greenhouses, or providing heat to a district heating system.

Heat reuse systems are most effective and economical when operated in conjunction with a direct liquid cooling system. The return water temperature will typically be much higher than can be achieved in an air cooling-to-chilled water or refrigerant-based cooling system.

An air-cooled IT equipment/chilled water heat removal system can feed a heat reuse system, but it will require more equipment and energy use to concentrate the heat. In either case, a plate-and-frame heat exchanger or heat pump will be required to concentrate the heat before its transfer to a heating supply loop outside the datacentre.

In general, the payback or return on investment of heat recovery systems is low, particularly at smaller datacentres. Innovations in datacentre cooling techniques will be required to improve the economics of heat recovery. These innovations could have the ancillary benefit of reducing, and possibly even eliminating, water use in datacentres – a significant advantage for a new cooling technique.