Old battery acid can be handled in two ways.
The acid is neutralised with an industrial compound similar to household baking soda. This turns the acid into water. The water is treated, cleaned and tested to be sure it meets clean water standards. Then it is released into the public sewer system.
Another way to treat acid battery is to process it and convert it to sodium sulphate, an odourless white power that is used in laundry detergent, glass and textile manufacturing. This takes a material that would be discarded and turns it into a useful product.
During the battery breaking process the container and lid are broken up into small pieces which are also recycled and when mixed with a small proportion of virgin material new plastic feed stock is produced and the cycle continues!