how to make tofu without the harmful chemical additive(lime or calcium carbonate)?

Not to be rude but why do you consider lime to be harmful?

Sorry but had to be asked. Now on to the 'good stuff'. There are several coagulants that can be used for tofu! Just remember that taste and texture are affected. Here are a few things I've used other than lime or epsom salts.

Vinegar (really soft large curd-boiling firms it up)

CItrus juices (grapefruit doesn't work! lemon/lime work quite well but end result is similar to vinegar)

Seawater (needs a lot of rinsing to remove sodium!)

saltwater (see above)

potassium chloride (in stores as a no sodium salt, strange taste and texture)

Lastly I thought you might enjoy this link.

The best thing to use is "nigari", which is magnesium chloride.

There is no such thing as a "non-chemical agent", LOL, 100% of YOU is made out of chemicals!

The "calcium carbonate" you are so concerned about is what your bones are made out of along with other things, and calcium carbonate is added to "organic soy milk" as a dietary supplement!

And actually, as I understand history, Nigari (derived from evaporated seawater) is actually the most traditional coagulant used in traditional tofu-making.

'Itadaki-masu!'

P.S. Just for perspective on "chemicals", cyanide is made from nitrogen and carbon. Does that mean nitrogen and carbon are bad for you? People die every year from inhaling Dihydrogen Oxide, should we ban it? (It's also called "water")

Why spend the time making tofu when you can buy it at the store. Just because bad stuff is used to make it doesn't mean bad stuff is in it.

How To Make Nigari

You should find this link interesting.