Some compost made from mixed solid waste contains plastic and glass.
Harry Hoitink and Charles Krause found the particles using microscopic techniques. The result, Hoitink says, can be polluted farmland. The scientists say more research is needed to determine the level of contamination and a level that may be acceptable to farming. And they emphasize that mixed solid-waste compost is not the same as compost made from separated solid waste. Separated- waste compost, the most common type, lacks serious problems and has many benefits.