Valuation Study

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Benefits of Reducing Pollution using Water Hyacinth

Attributes

Medium: Air

Country: China

Analytical Framework(s): Economic Analysis

Study Date: 2010

Publication Date: 2013

Major Result(s)

Resource/Environmental Good CNY, million per year
(2010)
benefit of biogas 6.21
benefit of organic fertilizer 2.16
value of GHG emission reduction 0.47
value of water quality improvement 13.72

Study Note: The study was conducted in the Kunming region. Kunming City has a high demand for resources and is very polluted. Dianchi Lake, which is close to Kunming City, is one of three lakes given national priority for treatment, and is one of the most polluted lakes in China. The dominance of water hyacinth is one of the lake's biggest problems. Although many pollutants can be absorbed from the water by water hyacinth, only nitrogen, potassium and phosphorous were considered in this study. The value of water hyacinth in reducing pollutants was estimated against the cost of using wastewater treatment plants and silt dredging to remove the same amount of pollutants from the water. This study assumed that water hyacinth for the production of biogas comes from two sources; from natural growth and from cultivation.

Study Details

Reference: Zanxin Wang, Jin Wan. 2013. Cost-Effectiveness Analysis of Ground-Level Ozone Control in and Around Beijing. EEPSEA Research Report, No. 2013-RR7.

Summary: To control the rapid spread of water hyacinth in a eutrophic body of water, an economical use forthe water hyacinth that has been removed has to be found. This study analyzed the environmental performance and the financial and economic feasibility of using water hyacinth to reduce the nutrients in a eutrophic body of water, coupled with the production of biogas. The results revealed that the project is economically feasible and has a desirable energy gain. The results also revealed that the project is not financially feasible but to achieve the same level of control over water hyacinth in the without-project scenario, the government would spend less money on the control of water hyacinth if they were to implement the proposed project. Moreover, the project is desirable in terms of energy performance. For disposing of 11,004.2 tonnes of water hyacinth, the project has an energy gain of 5.3 trillion joules while the current approach has an energy loss of 162.9 billion joules.

Site Characteristics: Dianchi Lake is situated to the south of Kunming City, the provincial capital of Yunnan Province, China, at 102°29'-103°01'EL, 24°29'-25°28'NL. The Dianchi watershed forms part of the water systems of the Yangtze River, the Pearl River and the Red River. The total area of the watershed is 2920 km2 , with the lake taking up 309 km2 . Dianchi Lake is the water source for agriculture, industry, households and fisheries in Kunming. It also plays an important role in climate mediation. At present 3.57 million people live in the watershed and it's 61.9 thousand hectares of agricultural land play an important part in the economic and social development of Kunming City and Yunnan Province. As well as being a water source for Kunming City, Dianchi Lake also serves as a sink for urban sewage, industrial wastewater and agricultural runoff. With the rapid development of the economy and urbanization, Dianchi Lake has been severely polluted for several decades. Before the early 1970s, the water quality was judged to be level II, or drinkable with regular treatment. The water is now graded at level V or undrinkable without intense purification. The lake is suffering from eutrophication, with COD, BOD, TN, TP and NH3-N well above standard levels. As algae flourishes all over the lake, the aquatic system and biodiversity are destroyed, and the lake can no longer supply drinking water to the city. The city is now resorting to Songhuaba reservoir for water.

Comments: The study analyzed mainly the carbon balance and economic feasibility of using water hyacinth to reduce the nutrients in a eutrophic body of water and to produce biogas. However, determination of the optimal processing scale requires further study on the dynamics of water hyacinth in a given aquatic system. Moreover, the possibility of using water hyacinth to move a lake from a eutrophic state to a clean state is affected by both the dynamics of water hyacinth and that of the nutrient stock in the water. The latter is affected by the inflow and outflow of nutrients, as well as by the stock of water hyacinth. Further studies should investigate the effects of harvesting water hyacinth on the state of the water.

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