from what i understand, there is a mercury free version of daguerreotypes also, it's called the bequerel process,
it takes more time to develop, but the process does exist.
another apug user, jason greenberg motamedi is a daguerrotypist ...
he's been making them for a long long time, and gives workshops on making them from what i remember.
his website has some stunning dags on it too ... http://motamedi.info/