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Environmental Benefits

Environmental Benefits

The reduction of production temperature and the increased workability of the mixtures provide a potential for significant reduction in energy consumption and emissions when using WMA.

My WMA publications


Zaumanis. Warm Mix Asphalt., K. Gopalakrishnan et al. (eds.), Climate Change, Energy, Sustainability and Pavements, Green Energy and Technology, Springer-Verlag, (2014), DOI: 10.1007/978-3-662-44719-2_10

Zaumanis, Martins, and Juris Smirnovs. 
Analysis of Possibilities for Use of Warm Mix Asphalt in Latvia.” 
In Civil Engineering. International Scientific Conference. Proceedings. Vol. 3. Jelgava, Latvia, 2011.
Laboratory Evaluation of Organic and Chemical Warm Mix Asphalt Technologies for SMA Asphalt.” 
The Baltic Journal of Road and Bridge Engineering 7, no. 3 (2012): 191–197. doi:10.3846/bjrbe.2012.26.
“Laboratory Evaluation of Warm Mix Asphalt Properties.”
5th International Conference “Bituminous Mixtures and Pavements.” Thessaloniki, Greece, 2011.
Development of Calculation Tool for Assessing the Energy Demand of Warm Mix Asphalt.”
Procedia - Social and Behavioral Sciences 48 (January 2012): 163–172. doi:10.1016/j.sbspro.2012.06.997.
“Laboratory Testing of Organic and Chemical Warm Mix Asphalt Technologies.” 
St. Louis, MO, USA: National Asphalt Pavement Association, 2011

My book:                                          My Masters thesis:  

Energy Use

https://sites.google.com/site/martinszaumanis/warm-mix-asphalt/emissions/Figure%201.jpg?attredirects=0One of the most significant benefits of WMA is the decrease in energy use. It has been reported that for every 6°C reduction in temperature, fuel consumption is reduced by approximately 2-3% (Young, 2007). Naturally, this will greatly depend on other parameters, most notably moisture content. Figure on the left by Robert Frank summarizes the effect of moisture and temperature on the energy consumption for asphalt production.

The results from various studies confirm the expected reduction in energy consumption. A scanning report of European WMA production sites demonstrated a 20 to 35% decrease in fuel use (D’Angelo, 2008). Prowell et al. (2012) have summarized the energy consumption from fifteen WMA projects, representing six technologies and report an average measured fuel consumption reduction of 23%. Similarly, the draft NCHRP 9-47A final report demonstrates savings of 22.1% for an average temperature reduction of 27°C at five different production plants. The project results also indicate that the theoretical calculations underestimate the actual fuel savings at an average by 45%. The additional reduction is attributed to casing losses – heat radiated through the drum, ductwork, and baghouse or otherwise lost. Zaumanis et al. (2012a) have calculated energy reduction in the entire production cycle and 7% to 18% reduction in energy use has been reported, with the conclusion that the savings are strongly linked with the reduction in production temperature. Practical field measurements have shown that if technologies that allow WMA production close to the boiling point of water are utilized (LEA, LEAB), the energy savings in production can be greater than 50% (Prowell et al., 2008).

Reduction of Emissions

Reducing the asphalt production temperature limits the emissions from production, thus reducing the carbon footprint of the asphalt industry. As expected from the reduction of fuel consumption, the vast majority of reports indicate reduction of CO2 emissions due to use of WMA. The relationship between fuel and CO2 reductions is shown to be linear as seen in figure by R.Frank. This concurs with the NCHRP report 9-47A that evaluated seven different technologies at three locations and reports an average 20% reduction in CO2 emissions resulting from a 21% reduction in fuel use for a mean temperature reduction of 29°C (NCHRP 9-47A draft). Data provided by UK Carbon Trust (2010) allows calculations which show that switching to WMA production would allow CO2 savings of 9%. D’Angelo (2008) reports plant stack emission reduction of CO2 in the range of 15% to 40%, SO2 – 20% to 35%; nitrous oxides (NOX) – 60% to 70%, volatile organic compounds (VOC) up to 50%, and carbon monoxide (CO) – 10% to 30%. Frank et al. (2011) notes that the CO and VOC emissions are a part of broader plant practices and may not be directly related to the use of WMA.

The reduced temperature in some cases may require plant burner tuning. As reported in NCHRP 9-47A it can be difficult to properly adjust the burner to maintain the optimum fuel/air ratio over the whole firing range. Incomplete combustion will result in both increased fuel use and higher emissions (NCHRP 9-47A draft). The unburned fuel may cause contamination of the produced asphalt and an increase in the VOC and/or CO emissions (Harder, 2007; NCHRP 9-47A draft).

Crew Exposure

The reduction of aerosols and fumes is also beneficial to paving crews as visible in Figure. Keeping the emissions low is especially important in unfavorable settings like tunnels or underground garages. The results of a study by Kriech et al. (2011) showed average reduction in total organic matter (TOM) of 36% compared to HMA. The authors also noted that different asphalt binders exhibit significantly different breathing zone exposure levels, thus the effects of lowering the temperature may vary from site to site. A report by D`Angelo et al. (2008) indicate reductions of aerosols/fumes and polycyclic aromatic hydrocarbons (PAHs) in the range of 30-50%. McClean et al. (2012) reports reduced dermal absorption of polycyclic aromatic compounds (PACs) metabolites when reducing temperature from 154°C to 121°C. It has also been recognized that use of WMA is very beneficial for application of mastic asphalt (gussasphalt) (D’Angelo et al., 2008). This type of pavement is placed at much higher temperatures compared to HMA and thus exhibits higher emissions. It has been demonstrated by Spickenheuer et al. (2011) that a 10°C increase in in application temperature results in a 20% increase in concentrations of vapors and aerosols at the typical mastic asphalt application range of 216-270°C.