After being scaled, material is tipped. The incoming material is mixed to provide an optimal carbon to nitrogen ratio, between 20:1 and 30:1. The preferred content is 50 to 70 percent food scrap, and 30 to 50 percent yard waste. Extra yard waste received during the summer can be stored for introduction during winter, when the incoming yard waste component is smaller.
Unwanted foreign material such as plastic wrap, expanded polystyrene foam and metal is separated at this time, requiring extra handling. Care should be taken by householders to place this material into the appropriate recycling or waste stream.