The thing is that nut shells can take years to decompose. Because of this long decomposition time, you can toss them into an ordinary composting bin along with the broccoli peelings and other kitchen and green waste, but you can expect to see them them there, rock solid, long after the other material is ready for the garden.
So, what do you do with them?
The most constructive thing to do with nut shells is to use the shells as mulch. Take advantage of the natural properties of the nut shells, rather than fighting them.
Break the nut shells into small pieces and spread them on the ground underneath shrubbery or in between crops in the vegetable garden. Mulch helps keep weeds at bay, and also helps keep moisture from evaporating. People very frequently use wood chips or bark chips as mulch, which is fine, but nut shells will last longer and anyway, you can easily intersperse them.
Shells will last a long time, but not forever. Eventually, they will decompose and release their contents into the soil. So what if it takes a few years? Let it. Mother Nature is patient.Image: Unsplash | Markus Winkler