Biomatter conversion was first used by FAS in its Chariot line of military combat automatons, intended as an emergency alternative fuel source in the event of fuel supply line interdiction.. Any and all organic matter, living or dead, was suitable. For the Chariot robot known as Scarabs and Khopeshes, the process worked via the robots releasing a cloud of nanites called a nano-haze. The nanites stripped the organic matter and passed it back to the robots. When the Chariot swarm owned by the corporation known as Hartz-Timor went rogue due to a programming glitch, the robots defaulted to biomatter conversion as a fuel source to fuel their rapidly and exponentially increasing numbers. Thus the swarm, which became known as the Faro Plague, became an existential threat to life on Earth. The threat was realized when the Plague ultimately consumed the biosphere, eradicating every form of life and leaving the Earth completely sterile. In the global fight against the Plague known as Operation: Enduring Victory, the scope and nature of casualties and fatalities caused by the nano-haze were highly disturbing to witnesses.
Additionally, a swarm's Horus robots could engage in a form of biomatter conversion in which they they directly consumed the bodies of living organisms rather than using a nano-haze. During the early days of the Faro Plague, a Hartz-Timor Horus was observed refueling thusly by feeding on a pod of endangered dolphins from the shore of the Banda sea.
Biomatter conversion is performed by many Zero Dawn Acquisition Class machines. The most basic herd machines, such as the Grazer and the Strider, were made for the purpose of gathering plant biomass and converting it into Blaze for use as fuel in Zero Dawn Cauldrons, as well as to presumably power themselves. This form of biomatter conversion is far more restrained and symbiotic than the destructive biomass consumption of the Faro Plague, as the gathered fuel is used to maintain the ecosystem. It is unknown if other, non-herd machines (such as the Sawtooth) can also use this process for self-fueling, as they do not seem to consume any biomatter.
The reactivated Corruptors and Deathbringers in the new world, being remnants of the Faro Plague, presumably use biomatter conversion to fuel themselves as they did before, though being only of a limited number, they do not have as much of an impact on local biology as they once did.
Biomatter conversion was the lynchpin of the plan hatched by the former GAIA Subordinate Function HADES to annihilate the new biosphere created by Zero Dawn. It had intended to use Zero Dawn itself to do so, but was denied when GAIA self-destructed, putting control of Zero Dawn out of its reach. It therefore decided to reactivate the Faro Plague and allow it to use its biomass consumption to again consume the biosphere, eradicating life yet again, this time without means of reestablishment. It was ultimately defeated and its machinations halted by the efforts of the Nora huntress Aloy.