Environment
Environment
Update: This webpage summarizes my PhD research. Since then I have done a lot of new research. Please visit the publications section to read the newest articles.
Full description of the effect on environment when using 100% recycled asphalt can be found in the article: 100% Recycled Hot Mix Asphalt: A Reviewand Analysis, Resources, Conservation and Recycling
100 % recycling can provide true sustainability by closing the materials cycle and allowing to use the reclaimed asphalt in the same high value application as conventional asphalt. A reduction in energy use of 20 % can be achieved by switching to 100 % RAP asphalt, mostly due to embedded energy for production of constituent materials. Along with this 18 kg CO2eq emissions per ton of paved mixture can be saved. With respect to transportation distance, hauling of materials from 100 km distant site for 100 % RAP production would still generate less emissions than production of virgin mix at materials quarry. These environmental effects and implementation of innovative production process would greatly benefit the agencies that have applied certification systems for sustainable construction practices (LEED, Greenroads, etc.)Full results of the research are summarized in the article.
Emission calculations
The existing state of practice for 100% recycling does not allow for conclusive evidence on the long-term performance of such pavements. Thus the analysis is currently limited to unit inventory or cradle-to-gate analysis, which at the time time is the most reliable part of any life cycle calculation.
The developers of the different technologies also claim that emissions are similar to traditional asphalt plants. A mixture containing 25% sand, 70% crushed stone and 5% bitumen was used in the calculations as a representation of a typical virgin mix. 100% RAP mixture is considered having 12% recycling agent added from binder mass. It is also assumed that 100% RAP mix does not require any virgin binder addition. In practice this is often the case, since any lost binder is replaced by the addition of recycling agent.
For simplicity, the transport distance was considered equal and consists of 50 km distance from quarry/RAP site to asphalt plant plus 50 km asphalt plant to paving site. The only variables in the process are energy use for production of constituent materials. The calculation results in Figure demonstrate that 18 kg of CO2 equivalent per ton of paved mixture can be saved by producing asphalt from 100 % reclaimed material.
The emission factors that were used in the calculation and full results can be found in the article.