Rendering recycles animal and poultry by-products such as fat, bones, hide, offal, feathers, hoofs, horns, hair, and blood. The by-products represent from 37% to 50% of the live weight of the various meat animals and as much as 57% of the live weight of many fish species. The current annual global production of meat and poultry is 325 million metric tons (MMT), and the resulting raw material for rendering would be 217 MMT per year if rendering was used everywhere. Rendered proteins and fats compete on the world commodity market with plant-based products. Rendered protein products are primarily used in food for poultry, pigs, ruminants, pets, and fish. Fat products are used for animal food, oleochemicals, and biofuels. Rendering meat by-products into animal food ingredients improves the sustainability of both the meat production industry and the users of the by-products. Composting or anaerobic digestion of these by-products is less environmentally impactful than landfills but results in more GHG production than feed ingredient use. Reducing food waste will improve global sustainability when otherwise wasted animal by-products are put to the highest value use. The future of rendering will depend on the industry adapting to the ever-changing environmental, social, health, and sustainability challenges.