The walls of your home are probably covered with Drywall, and then painted or papered. That Drywall is nearly 100% lime; the same material that sweetens your garden soil. If you are building or remodeling, you may want to recycle the waste Drywall for your plants.
Lime from Drywall
First you should remove any nails or other metal and discard them. Then the Drywall should be pulverized. The amount you have will determine the method you use. It can be mashed through 1/2" hardware cloth by a hammer. Or you may hire a local Recycler if you have a large amount. If you have a constant supply, you may even want to convert a Cement Mixer to do the work.
Prepare the Mixer by first removing the internal blades that tumble the concrete. Then add some 6-pound stones (not round) to the tub. Half-fill the tub with pieces of drywall and operate the Mixer until the Drywall is fine enough to satisfy you. Then remove the lime and refill the tub.
You may prefer to take another step and drill the tub full of 1/2" holes. This will allow the lime to fall through the tub as you add more Drywall. The finished product may be added to your garden soil or to your Compost pile.