Used anti-freeze can be recycled, normally at the local dump. You only need to capture the initial amount drained. This will have the highest concentration of glycol and contaminates. The material that remains after flushing w/water or if you choose to use a chemical flush will be diluted to an acceptable level that it becomes biodegradable (except maybe California). I would check your local rules and regs. At the end of the day, more coolant is spilled on the ground daily by vehicles over-heating then is purposely sweep out on the shop floor.
