We look into the past we see the history of composting as a history of problems. So, we have discussed: 1965 glass in compost1970 plastic in compost1975 heavy metals in compost1978 PCBs in compost1984 odour emissions from composting plants1989 dioxin in compost1990 micro-organisms in the exhaust air Every single problem mentioned above is enough to prevent composting. Especially odour is becoming an increasingly sensitive issue as people move closer to existing treatment plants. When sites for new facilities are proposed, the potential for odour is invariably one of the first concerns raised by local residents. Therefore, odours have been rated as the primary concern of the public relative to implementation of composting facilities. Designers must be conscious of this fact and be familiar with odour generation and odour control.