We’ve had this question often before. I run into trouble each time I respond but I’m sticking to my guns.
There is NO federal EPA regulation regarding the disposal of antifreeze. A few states may have such regulations but these are intended primarily for those shops that collect large quantities of it.
Since small quantities of antifreeze possess no environmental hazard and it is biodegradable, you may dispose of it safely by sprinkling it on your lawn or gravel driveway. You may do so with a clear conscience.