Hot Mix Asphalt Calculations Based on 2001 Hot Mix Asphalt Agreement

DNR entered into an agreement (PDF, 342KB) with the hot mix asphalt industry (PDF, 38KB) in 2001 regarding the calculation of emissions for asphalt plants. The agreement defines which hot mix asphalt processes should be included in the air emission inventory and the calculation of emissions for hot mix asphalt mixers. The industry has requirements that it also must meet under this guidance because of discussions regarding sulfur dioxide emissions from the asphalt mixer. The DNR configures all new and existing HMA plants according to the information contained in this agreement for air emission inventory purposes.

The HMA agreement identifies equipment common to all Wisconsin HMA plants. The agreement also recognizes optional equipment. Each piece of equipment is assigned an emission factor for a particular pollutant. The intent of the agreement is to have HMA emissions calculated uniformly across Wisconsin with each HMA reporting emissions based on a representative base of equipment. The identified base equipment was:

• Rotary dryer or parallel flow, counter flow drum mixer
• Asphalt cement storage heater
• Loader
• Conveyor
• Primary collector
• Haul road (unpaved or paved)
• Screen
• Diesel/natural gas generators (gensets)

As part of the agreement, sulfur dioxide emissions from the asphalt mixer calculations were decreased by 50% based on the industry's stack testing information supporting a contention that the hot asphalt mix absorbed half of the sulfur dioxide emissions from the fuel oil burned necessary to produce the asphalt. This 50% correction occurs after the sulfur dioxide emissions are calculated using this emission factor:

EMF= 26.784 lbs SO₂/ton product x %Sulfur (weighted percent)

In order to calculate the % sulfur (weighted percent) in the equation the hot mix asphalt company can use an Excel spreadsheet (ZIP, 10KB)which calculates a weighted percent sulfur after the HMA owner supplied their fuel oil usage numbers. The paper version of this Excel spreadsheet was supplied as Appendix A in the Hot Mix Asphalt Plant Agreement.(PDF, 342KB)

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