Abstract: The present invention is a biodegradable bag used as a liner for a grass-catcher bag of a lawnmower. The bag is releasably secured to the grass-catcher bag using a clip. A compost accelerant is placed inside the bag to speed the decomposition of the bag and the lawn waste contained inside. Once filled with lawn waste, the bag may be closed using a drawstring cinch-top and then placed in a compost heap for decomposition. The bag is adapted for use with grass-catcher bags for side-discharge and rear-discharge lawnmowers.