Exergy analysis of the environmental impact of paving material manufacture

Exergy analysis permits accurate measurement of the degradation of matter and energy using a single concept. A macroscopic exergy accounting method is proposed and applied to assess the environmental impact of road covering material manufacturing. Cement concrete and asphalt covers are examined. From the manufacturing process mass balances and exergy analyses conducted primarily by Szargut and his co-workers, the net exergy consumption for each type of paving material is calculated. This exergy consumption broadly reflects the minimum work required to reform the raw materials and restore the environment to its initial state. This minimum work may serve as a thermodynamic measure of the environmental impact of an entire manufacturing process, from the resource drawn from the environment to the finished product. In the two cases under study, the environmental impact depends on the type, thickness and manufacturing process of the paving material. An older technology, such as the manufacture of cement concrete using the wet process, appears disadvantageous, as is the production of asphalt cover which is manufactured during the fall. The proposed exergy indicator permits ranking of the materials according to their overall long-term impact on the environment.