The researchers studied compost made from municipal solid waste to see how the quality is affected by the materials used and the way it's processed. They looked at 30 samples from 10 different plants and found that most compost had high levels of nutrients like nitrogen, potassium, and phosphorus, making it good for fertilizing. However, many samples had too much plastic and glass in them, which can be harmful. The problem comes from the organic waste used to make the compost, which often contains these materials. To make better compost, the sorting and refining processes need to be improved to remove these impurities.