Why of why is there a constant stream of advice to add egg shells to compost bins? They do not break down and neither do they add calcium to soil. It is an internet problem, somebody puts it on a web site or social media page and it becomes ‘the truth’. Nobody bothers to check, nobody challenges or tests it.
They last a very long time in a garden: “The study looked at a property in Virginia that was at one time owned by Thomas Jefferson. It was a tobacco plantation that contained a small community of slaves from 1840 to 1860. Excavation of the site found thousands of eggshell fragments from both chickens and ducks, which had been raised by the community.”
Click image for full article.