Make a bit of space in your loft or shed, by getting rid of all the old parts you’ve replaced and are saving for just in case, but will probably never use again!
The idea is that, for example, a tyre or chain that has reached the end of it’s useful working life in the mud of Surrey, will still be very useful to people in dry and dusty Namibia, using their bikes more lightly, often as their only way to get to work and school.