Specific emergy of cement and concrete: An energy-based appraisal of building materials and their transport

Use and production of building materials, such as cement and concrete, is a major cause of global ecological problems with special reference to the overexploitation of non-renewable natural resources due to high temperature production processes, fossil fuels combustion, extraction of raw materials and non-recycling. In this paper, an environmental accounting method was applied to the production of cement and concrete in order to evaluate its dependence on natural resources even non-renewable and heavily relied on external inflows. The main steps of the production process (1) cement production, (2) transport of materials and (3) concrete mixing, were assessed by the emergy analysis (spelled with an “m”). This was performed to measure the amount of environmental resource use in terms of equivalent solar energy, extending the energy hierarchy principle to building materials. The resulting unit emergy values of cement and concrete were compared with previous emergy assessments in order to highlight how emergy analysis is sensitive to local context and reference system's boundaries. An Emergy Investment Ratio (EIR) was assessed and presented as a synthetic indicator of sustainability. Results showed a high dependence of cement and concrete production on external resource flows. Furthermore, the high value of EIR suggested a weak competitive capacity due to a high sensitivity to external instabilities.