Biomass is the biological material that makes up a living organism. The biological material is used by the Prototypes to use their superhuman abilities and to regenerate themselves.
Fresh bio-matter is acquired by consuming living organisms. Along with regeneration, biomass is also used to transform a Prototypes' body into a deadly weapon or create a protective armor to defend themselves.
Elizabeth Greene used a vast amount of biomass to construct an extremely large infected form around her. This behemoth form of hers was called Mother by Blackwatch soldiers and was capable of destructive attacks.
Alex Mercer was able to regenerate his entire body after he was blasted to the city's shore by the nuclear weapon he had dropped into the sea. His remains were splattered into red puddles, seemingly inert. But once disturbed by a crow, he regenerates his body by consuming the fresh biomass of the crow.
James Heller was left with critically low health and severe burns all over his body after being incinerated in one of Gentek's labs, but was able to regenerate by consuming one of the Blackwatch soldiers sent to confirm his death, thus regaining enough strength to escape.