I think its either clinical waste or chemical waste if it has needed to be reliquified and either way requires proper disposal these days (think blood bourne infections) sorry if TMI
Down the drain.
"The embalming process involves removing the body fluids and replacing them with a solution of formaldehyde, often containing a pink dye. The body fluids are treated and disposed of via the public sewer. The embalming fluid normally consists of a 2% solution of formaldehyde, an irritant, volatile acid. "
I would plead that anyone who has the very sad burden of arranging a funeral refuse the embalming (often called hygienic treatment) process unless there is a good need for it.
If there is no intention to view the deceased more than a day or two after death there is absolutely no need for this process.