Pub. 1 2018-2019 Issue 3

22 ENVIRONMENT M any U.S. communities are close to industrial asphalt plants, which are regulated by the EPA. The plants are located in cities, suburbs, and rural areas, andmost of them have a good relationship with their neighbors, who see their efforts to be good neighbors and who understand that these plants are dedicated to being sustainable. At the same time, some people seemisleading information that makes it difficult for them to evaluate what it is like to have an asphalt plant nearby. The purpose of this article is to explain what is and is not true about asphalt plants, as well as describ- ing the different kinds of asphalt products that are available. Employees at asphalt plants create asphalt pavement. They combine liquid asphalt binder, or asphalt cement, with asphalt binder and with aggregates that consist of gravel, crushed rock, and sand. Sometimes mixes also have additives in them, depending onwhat the asphalt will be used to build. The addi- tives might be chemicals to improve the performance of the mix, and they might also be natural fibers that make the spe- cialty mixes stronger. The binder, which is processed so that it meets defined standards, glues the aggregates together and is distilled by oil refining plants along with other products. All of the materials are monitored and regulated to ensure that they are used and stored correctly. In addition, the manufac- turing process uses recycled materials where possible. The asphalt pavement industry hasmade tremendous improve- ments to the process of making asphalt over the course of several decades. The plants use multiple emission control systems and the emissions that are released are monitored in order to be sure that they are low. As a result, the carbon foot- print for asphalt is very small when compared to other pave- ment materials. Not only that, but asphalt is also an excellent way to sequester carbon. That matters because carbon seques- tration is one way tomitigate climate change by reducing the atmosphere’s carbon dioxide concentrations. Federal and state environmental agencies that include the EPA regulate asphalt plants, and they have confirmed that the plants are not major polluters and therefore aren’t a health hazard or an environmental hazard. For example, one study found that a year’s worth of emissions was approximately the same as the emissions froma bakery during a two-week period. It was also about the same as 13 residential fireplaces during the course of a year, and the emissions amounted to less than six months of toluene emissions from a gas station. The EPA delisted asphalt plants once it became clear that their environmental impact was comparatively minor. Asphalt emissions come mostly from burning fuel such as natural gas. The fuel dries and heats the aggregate or the rock andmaintains a hot temperature for the asphalt. The dust that is created during other parts of the production process, such as when the aggregate is drying, are captured before they can be released to the environment by using baghouse filters or other control methods.What thismeans is that if you see steam coming out of the stack at an asphalt plant, it is almost always just that: steam. The steam is created by the loss of water vapor as the aggregate dries. Part of the confusion about asphalt is caused by the fact that there is more than one kind. Asphalt pavement material is dif- ferent than roofing asphalt. Coal tar is another product alto- gether. The pavement industry has concentrated its efforts in part in reducing the temperature it needs to produce asphalt pavement. That has been one of the main ways it has been able to reduce emissions. Another advantage to asphalt pavement is the fact that more than 99 percent of it can be recycled and reusedmultiple times. When it is recycled, it is called RAP (that is, recycled or reclaimed asphalt). It is also inert. It is waterproof, so thematerials used to create it can’t be leached from the pavement. This is whymany reservoirs that hold drinking water, as well as fish hatcheries, HOW ASPHALT PLANTS AFFECT THE