I've found a lot of empty and broken hazelnut shells lying under huge hazelnut shrub. (Most of them were eaten by squirrels but some have worm holes). Is it safe to use them for composting (maybe grinding them would speed up the process)? Or they can be used for mulching because they seem to last long?
If you have enough, try using them for mulch on a pathway. They last a long time, are a durable mulch, and make a lovely sound. In the Northwest US you can actually purchase bags of hazelnut shells to use on your pathways.
Yes you can use them for composting, with good composting conditions (greens, browns, temperature, and moisture) they should be no problem for the micro-organisms responsible for composting.
However, some people advice not to put seeds in your compost. This is because of the obvious reason that the seeds can germinate when using the final compost for other plants. For me, I don't mind that, in my compost there are still some seeds left from fruits or other crops. I remove 'bad weeds' anyway in the growing season.
Hazelnut and many other tree nut shells are packed with BTUs. If you have a wood stove, try tossing them in.
See the following web page for examples: https://www.harvesttimeshells.com/half_shell.html
It notes that hazelnut shells can be used for mulch, with the following qualities:
- Holds moisture, keeping potted plants & flowerbeds moist
- Keeps weeds down
- Adds beautiful color
- 100% Renewable, All Natural & Sustainable [depending on your source/methods]
- Compacts Well
- Lasts 5-7 Years
It also mentions hazelnut shells as fuel:
- Burns at 8,500 BTU's per pound
- Burns Clean, Little Ash
- Use in Wood Stoves & Fireplaces
Or you can use empty hazelnut shells for cheese smoking. It is well known that hazelnut shells are one of the best smoke sources for that purpose.
Many famous cheeses have their "smoked" versions, like:
...and they are as a rule even more appreciated than their basic version.
Many delicious dishes can be made using smoked cheese. Here is a recipe for smoked cheddar souffle.
you can grind them up and use them for sandblasting delicate surfaces