Emissions Study Summary

How low are emissions from a typical asphalt plant? The answer: startlingly low. In one of the most closely monitored emissions categories – volatile organic compounds (VOCs) – an asphalt plant gives off in one year what two residential fireplaces do. Or about the same as an average commercial bakery does in only two days.

Those are among the findings of the respected independent Clayton Group Services in a study. Issued in December 2000, the study compared emissions from a hot mix asphalt plant with those from a number of other common sources.

For purposes of the comparison, the hot mix asphalt plant was defined as one with an annual production rate of 100,000 tons – about average for a North Carolina asphalt plant. The consumer-oriented sources tested for comparison included: residential fireplaces and woodstoves, bakeries, gasoline filling stations, barbecue grills and fast-food restaurants.

The test sources were chosen for frequent occurrence in communities and the ready availability of emissions data for comparison. The Clayton Group study found that during the course of a year an asphalt plant gave off:

  • the VOCs of two residential fireplaces during the course of one year
  • the VOC emissions of a typical commercial bakery operating for two days
  • the total organic compounds (TOCs) emissions of three gasoline filling stations during the course of a year
  • the TOC emissions of five fast-food restaurants during the course of one year
  • the polycyclic aromatic hydrocarbons (PAH) emissions of 10 residential woodstoves over the course of a year.
  • the benzene emissions of a gas station operating for five months.

Volatile organic compounds (VOCs) are carbon-containing compounds that readily evaporate at normal air temperature. VOCs come from sources such as gasoline, hair sprays, household cleaning products and dry-cleaning fluids, as well as from a variety of adhesives, copier fluids and other common chemicals. Trees, grasses and other kinds of vegetation also emit VOCs.

TOCs are any organic compounds, volatile or not, containing carbon atoms.

PAHs are found in wood smoke and diesel exhaust.

Benzene is a clear, colorless aromatic liquid used as a solvent in printing, paints, and dry cleaning. Benzene is released in the fumes and exhaust of gasoline, from other natural fuels, as a result of the combustion process, and in the manufacturing of other chemicals.

For a complete copy of the Emissions Comparison Between Asphalt Plants and Selected Source Categories report, contact Clayton Group Services at 919.851.2160.