Diesel fuel is the primary solvent of the liquid "AC" they called it aka the black stuff. For instance, you get any hot AC on you, you're in big trouble because it is super hot, but on your clothing or a spill, the only way to get it cleaned up is with diesel fuel. There are stages of containment around the storage of the stuff. As far as recycle, it is just enough diesel to wet the old AC in the grindings. There is no excess. It has to be wet for the new and old to mix. The operator is wetting the surface well then feeding the aggregate bins for the plant. Each time they feed a bin, they scoop and drop the recycle grindings. Every 4-5 times, they add a scoop to the conveyer bin, put a fresh scoop on the back of the stall, and soak the mix in diesel. The diesel doesn't penetrate very deep and the point is to keep it consistent. That area is in the second containment zone for AC, so it is not a part of the groundwater environment. Spending a fortune on wasted diesel is also not the point. Feeding the plant is a monotonous routine. Dialing in these kinds of this is all the mental stimulation there is really. The whole job is, service the machine as needed, don't spin the tires, and NEVER let a aggregate bin go empty or put the wrong class in the wrong bin.