Economic evaluation of sewage irrigated agricultural lands in the rural suburbs of Beijing.

Environmental economic methods were used to evaluate the economic effect of sewage irrigation on suburban farms of Beijing. The results show that economic benefit of sewage irrigation in 2002 is 462 million RMB, a 9.3% increase in agricultural production value.Savings from polluted water processing and clean water consumption are in the highest proportions,49.7% and 27.6% respectively, and those from fertilizer and crop yield increase account for 18.1% and 3.1% of overall value increase. Total loss induced by sewage irrigation stands at 139 million RMB, constituting 2.8% increase in agricultural production in 2002, 46.5% of which is from crop yield drop, 2.2% from crop pollution,30.3% from soil pollution, 15.7% from health risk and 5.2% from groundwater pollution. The positive to negative value ratio of sewage irrigation is 3.3 and sewage irrigation direct benefit is about 1.7 times of total environmental loss. This implies that economic benefit from sewage irrigation is sustained at the expense of the environment.Thus much attention should be paid to such losses by relevant agencies,government or otherwise.