- Solar. Solar panels on the roofs of the building, including those covering the stockpiles, will be used to supply a portion of the electricity to run the plant, says Brock. "Solar mirrors will heat the hot oil," he says. "The asphalt storage tank acts as a battery absorbing the heat and overheating the asphalt in the tank when the sun is shining. Heat from the asphalt can then be used at night or on non-sunny days as heat is required. "In peak production, line electric power will be required to supplement the solar power, but the solar will be sold back to the system when the plant is not running; thus making it a zero cost to the owner," he says.
- The best fuel? To remain competitive, higher percentages of recycle will be mandatory in the future, and the least expensive fuel to keep aggregates dry will have to be used. "I expect to see the plants being fired with natural gas since it will most likely be the most economical fuel available," says Brock. "If natural gas is not available, most likely wood would be used; also wood may be used if it is required to meet renewable requirements." Whatever fuel is the most economical will be chosen. "If you're next to a landfill, you can run the plant off methane," says Hunt. "Biomass fuel burners are another option. Anything with a caloric value we can burn can be used as fuel. We've made biomass fuel burners before, and they could become popular again," he notes. "And there are plants utilizing methane right now as well."
The future is now
We've come a long way from noisy, dirty, dusty asphalt plants.. Right now, say both Brock and Hunt, you can stand beside an asphalt plant and not hear the plant. "You hear the chains and conveyors but not the plant itself," says Hunt.
"Through using the latest technology available, plants today can be run at levels as low as 83-84 decibels, which is extremely quiet." Brock says.
You really can't smell an asphalt plant these days either. "Plants in California don't smell," says Hunt. "We have load-out tunnels, and we collect the fumes, which are incinerated or go through a filtering system. You don't see anything, and you don't smell anything."
With the warm mix foamed asphalt systems, smell is eliminated from the plant other than the loading of trucks into the asphalt storage facility. "By using a closed loop system to catch the air coming out of the tanks as they are filled and dumping them back into the transports, smell on the liquid side can also be eliminated," says Brock.