The first step in the process for making asphalt is having a stockpile of aggregate. Aggregate comes in multiple forms of crushed stone, gravel, and sand. The blending of these aggregates is the next step in the manufacturing process. Each aggregate is sorted into cold feed bins that adjust the proper amount for the desired mixture. The aggregates run through a conveyor belt system that will transport them to the drying drum. Inside the dryer drum the aggregates are tumbled though a heated air stream. In this step asphalt cement or bitumen is added. Bitumen is the black tar type substance that is a form of crude oil extracted from oilsands. The fourth step is the emission control system. As the drying process takes place fine particles of sand and dust collect. The ECS (emission control system) removes these particles before the air goes back into the atmosphere. The primary collection chamber allows for these particles to be added back to the aggregate mix.