Most larger cities have a hazardous material disposal site open to the public. I have taken old powder and other items such as old half filled paint cans to the one here in Dallas. They dispose of it somewhere else. Quick and easy solution to your problem. There was no fee for my disposal either. If you have access to rural land (yours or by permission of the land owner) do as someone above said. Dig a 12" deep hole, pour in small portions of powder, and burn it off. It won't blow up, but be careful not to burn too much at one time. We do not need a Yosemite type fire here in Texas.