Eating egg shells: advantages v.s. disadvantages?

Question

I am an engineer and a scientist, but not in the field of medicine or health. Partial answers/comments are welcome.

Some of my family members start eating egg shells for the sake of obtaining nutrition like Calcium and minerals, once one egg a day before noon. By boiling the egg and microwaving the egg shells. Here are my questions:

1) Does eating egg help the consumption of Calcium and Minerals? And are they digestible in our body?

2) Is it clean, hygiene and healthy to eat egg shells? Concern that the Hen produces the egg and its metabolic waste through the same Anus? Can we get sick eating the egg shells, even if it has been boiled?

3)The egg shells are sharp, buy we can try to crush the shells through our teeth as much as possible. Once we consume the egg shells in the Esophagus and the stomach and intestines, more generally, in the Gastrointestinal tract, would the egg shells hurt or cut the organs by any chance? Would it be healed by itself, or would it potentially cause the cancer for any gastrointestinal tract? Also how likely it is a dangerous source of Salmonella / harmful bacterias?

4) How likely consuming the egg shells causes Kidney Stone and Renal Calculus? Say, if I am a young adult, or someone is a senior person?

5) There are known advantages of eating egg shells: https://www.youtube.com/watch?v=txtut6GS2NU. But are there known disadvantages for eating egg shells, say if just consuming one shell per day, and fully cooked and boiled? Are there Clinical Medicine test for advantages and disadvantages? Anyone gets Cancers through eating egg shell? Kidney Stone and Renal Calculus?

Again, Partial answers/comments are welcome. Thank you.

Answer 1

Not allowed to comment, so just a partial answer from my part: Salmonella bacteria are commonly found in the excrements of birds and egg shells are usually contaminated with them, and even let them through to some extent. Therefore it is very important to boil the shell in advance. This should kill more than 99% of the Samonella bacteria found on the shell: source link.

Not sure about the cancer risk or the likelihood of small cuts. However, Paparazzi is wrong that egg shell contains a lot of fiber. The main components of egg shell are chalk, with some traces of magnesium and protein, so no fibers in there. Please don't downvote this answer, it's only meant as a comment.