15. Conclusion

To assess a product's energy balance, we need to consider not only its use and the energy it consumes during this stage (use or operating energy), but also all the energy consumed outside this stage, from its development through to end-of-life management (grey energy). For many products, this grey energy is greater than the energy used. This hidden energy has long been overlooked. Alongside this energy consumption, there are pollutant emissions, waste generation and other environmental damage. These collateral effects are far from negligible, and for some products can even be predominant.

In some cases, such as for buildings, most of the grey energy consumed, as well as pollution and nuisances, are produced in the country where the buildings are constructed. For many other products, the grey energy and associated nuisances are produced in foreign countries and are...