I wasn't sure about that either, so I did some research. Hopefully an expert can chime in.
http://www.nolo.com/legal-encyclopedia/alkaline-hydrolysis-laws-your-state
What Is Alkaline Hydrolysis?
Alkaline hydrolysis is a chemical process that uses a solution of 95% water and 5% potassium hydroxide or sodium hydroxide to reduce a body to components of liquid and bone.
Bone fragments are retained so they can be dried and turned into a substance similar to cremated ashes. The bone byproduct of AH may be scattered, buried, or disposed in any way cremated ashes are handled. Implants such as dental fillings or pacemakers can be easily separated from the bone fragments before the bones are rendered into “ash.”
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https://www.academia.edu/7731061/Flush_and_Bone_Funeralizing_Alkaline_Hydrolysis_in_the_US
Flush and Bone: Funeralizing Alkaline Hydrolysis in the US
These systems [AH] were first put to use by US medical schools—notably the Mayo Clinic in Rochester, MN and the University of Florida’s Shands Hospital in Gainesville—to dispose of donated human cadavers.
Minnesota was the first US state to legalize AH (2003), thereby sanctioning the Mayo Clinic’s interest in hydrolyzing anatomical donations. Minnesota legalized AH under its mortuary laws (149A) in apparent anticipation of commercial funerary offerings of AH, which became a reality in2012 when Twin Cities–based Bradshaw Funeral Services began operating an AH system. In Florida, the city of St. Petersburg’s Water Resource Department (WRD) has closely monitored and restricted the flow of effluent produced by the state’s first commercial AH system, installed at Anderson-McQueen Funeral Home’s Cremation Tribute Center in 2011.
. . . a high-pressure system operating at145 psi can hydrolyze a body in about three hours. . .
In contrast, a low-pressure system operating at 0 psi takes about twelve hours to hydrolyze a body, . . .
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http://abcnews.go.com/Technology/story?id=4828249&page=1
New in mortuary science: Dissolving bodies with lye
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http://www.slate.com/articles/news_and_politics/explainer/2009/12/soluble_dilemma.html
How long does it take to dissolve a human body?
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http://resomation.com/about/need-for-change/
A funeral involving Resomation is the same as one involving flame cremation until the point at which the body is committed from public view. In Resomation a special wool coffin is placed into the Resomation chamber, and instead of fire, uses a water and alkali based method – also known as alkaline hydrolysis – to rapidly reduce the body sympathetically to ash. Nature also uses a form of alkaline hydrolysis after burial to help reduce the body to bone.
The process is on average 3-4 hours long and once complete the pure white bone ash that remains is returned to the family in an urn as happens with flame cremation.