The exploitation of waste heat from industrial processes is deemed as a useful tool to achieve national energy saving objectives. If fed into district heating networks, residual heat would allow for a reduction in fuel consumption in district heating plants and consequently a reduction in polluting and climate-changing gas emissions. From a regulatory point of view, industrial waste heat recovery projects must be subjected to cost-benefit analyses that also take environmental costs into account.

In this framework, the study aims at defining a methodology that allows for the evaluation of national average environmental costs and benefits (or environmental externalities) resulting from the exploitation of industrial waste heat in district heating networks.

To this purpose, the emission factors of the pollutants that contribute most to air pollution phenomena have been identified for the main fuels currently used in district heating plants: fine particulate matter (PM2.5), nitrogen oxide (NOx), sulphur oxide (SOx), ammonia (NH3), non-methane volatile organic compounds (NMVOC). Similarly, for the same fuels, the emission factors for the main greenhouse gases have been identified: carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4).

Since feeding industrial waste heat into the grid also entails additional electricity consumption due to the operation of pumps and auxiliaries, as well as a lack of electricity production from cogeneration district heating plants that are replaced by industrial waste heat, the study also identifies the emission factors that characterize the average national electricity vector.

The monetization of the impacts due to atmospheric emissions refers to the simplified methodology for the evaluation of external costs proposed by the NEEDS project (New Externalities Developments for Sustainability) [24] and applied on several occasions by both the European Commission and the Parliament (see for example Directive 2009/33/EC). The methodology has been appropriately modified to adapt it to the geographical, socio-economic and technological context under examination.

The developed methodology allows the decision maker to quantify environmental costs and benefits of industrial waste heat recovery projects and to overcome the classic cost-benefit analysis, integrating the environmental dimension into the decision-making process.