The researchers studied how different organic materials and nitrogen sources affect composting of waste mushroom bed from Agaricus bisporus. They found that using waste mushroom bed with fowl manure and sawdust resulted in the highest organic matter and nitrogen content. Composting with rice straw reduced the volume of compost more than using sawdust. The compost met legal criteria for heavy metal content. Microorganism populations increased during fermentation, with aerobic bacteria and Bacillus sp. being the major groups. The optimal composting period was 50-60 days.