This study is concerned with tracing young children’s ideas about the biological process of decomposition, as well as about everyday waste management, and with using these ideas for shaping the objectives of a potentially effective learning environment in the theoretical context of constructivism. Conducting individual, semi-structured interviews with 28 preschoolers (age 5-6) of 2 public kindergartens at the area of Patras, we traced their ideas about (a) decomposition of organic materials and man-made ones, (b) domestic garbage and their fate after being removed from the house and collected by the garbage trucks, and (c) recycling and its usefulness. The findings of the tracing phase, as well as the shift from these to the objectives of a learning environment for promoting a better understanding of the topic in question and get children engaged in environmentally responsible everyday practices, are thoroughly discussed in the paper.