Whilst Vaucanson invented his robotic pooping duck in 1739, it took until the year 2000 for the official field of Gastrobots to be founded, through the paper “Gastrobots —Benefits and Challenges of Microbial Fuel Cells in Food Powered Robot Applications” by Stuart Wilkinson in Autonomous Robots.
Because Gastrobots can digest generally available organic materials, they can survive in environments without constant human supervision - from mowing the lawn to be sent on 'start it and forget' long term exploratory missions.
Whilst digestion is a must have process for gastrobots, excretion unfortunately is seen as more optional, at least for Wilkinsons first gastrobot, Chew Chew. This bot was publicized as a meat eating robot, but until then only ran on sugarcubes, producing only carbondioxide and water as waste.