Food Hacks on eight reasons why you should never throw away eggshells, primarily because they have additional uses you probably never thought about:

2. Make Your Coffee More Drinkable< Do you hate how bitter your morning cup of coffee is? Here are two pieces of advice: read our coffee primer, and add crushed up eggshells to the grounds when you brew your cuppa.

I know, I know: it sounds weird and gross. But the eggshells serve to clarify the coffee, which helps reduce the bitter taste (and they add no taste of their own). However, make sure that you’re using eggshells that have been washed (note: in America, all eggs are washed before being sold).

なるほど. Who knew?