Calculation Model of Energy Consumption Inventory for Comparison of Warm Mix Asphalt and Hot Mix Asphalt

Warm Mix Asphalt (WMA) is a relatively new technology that allows significant lowering of the production and pavement temperature of conventional Hot Mix Asphalt (HMA). It promises various benefits, but probably the most significant is the possibility to reduce the energy demand for asphalt industry thus supporting the demands of Kyoto protocol for reducing greenhouse gas emission in the atmosphere. An easy to use life cycle assessment tool would be beneficial in assessing the environmental benefits of WMA in comparison with HMA, however developing an entire calculation model for Life Cycle Assessment (LCA) is very complex. This is mostly because of immense information that needs to be included, many variables and questions about the long-term performance of WMA pavements that need to be answered. The calculation model, presented in the paper, was developed as inventory of energy flow for asphalt production, which is the first phase in developing LCA tool. The calculation involves all the main areas that can be influenced by choosing WMA instead of HMA, including production, paving and compaction of asphalt, mining and/or manufacturing of all component materials and transportation. The amount of used energy and the energy sources were defined for each of the processes allowing to express the results in terms of total energy demand distribution by the energy source or by unit process, which is significant in further calculation of carbon footprint. The case study results present the comparison of asphalt energy consumption for seven different modules. Transportation distances and the asphalt type were defined as typical for a paving site in Latvia. The results showed 7% to 18% energy gain for the WMA in comparison with the reference HMA and indicated that the amount of reduction is mostly attributed to the reduction in heating temperature of the production plant