R. Honda, A. Hiramatsu, Y. Hara and M. Sekiyama

Transcription

1 Supply-Demand Balance of Compost between Urban and Agricultural Sectors According to Peri-Urban Development in an Urban-Rural Fringe Area in Asia: A Case Study in Nonthaburi, Thailand R. Honda, A. Hiramatsu, Y. Hara and M. Sekiyama Abstract We investigated the current situation of supply and demand potential of compost and illustrated the shift of supply-demand balance of compost between urban and agricultural sectors according to peri-urban development in an urban-rural fringe area of Bangkok. In the study area in Bang Maenang, Nonthaburi, Thailand, 42% of the supply potential is estimated to exceed the demand balance in The population density where supply and demand potential balance was estimated as approximately 1,300 1,400 persons/km 2. Since the nitrogen supply potential in the study area exceeded the estimated demand potential, proper collection and treatment of surplus nitrogen was required to protect the canal water environment. Key words: Resources circulation, compost, peri-urban development Introduction Many developing Asian countries face serious environmental problems associated with rapid economic growth. Although there is an urgent need to learn from the experience of industrialized countries that have solved serious pollution problems, existing pollution-control measures must be applied in a manner appropriate to the target region (Takiguchi et al., 2007). Bangkok Metropolitan in Thailand is one of the largest expanding cities in Asia. Increase of middle-income citizens promotes their migration from the urban center to the wider suburban area, where they can own their houses (Hiramatsu et al., 2008). Responding to their demand, there is robust development of new residential communities found in the urban fringe of Bangkok. R. Honda A. Hiramatsu Y. Hara M. Sekiyama Transdisciplinary Initiative for Global Sustainability (TIGS), Integrated Research System for SustainabilityScience (IR3S), UniversityofTokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo , Japan K. Fukushi et al. (eds.), Sustainability in Food and Water: An Asian Perspective, Springer Science+Business Media B.V. 2010

2 290 R. Honda et al. In Asia, built-up areas tend to expand in such a way that areas of urban-rural mixed land use are created. This tendency is rooted in socio-cultural conventions such as long-standing and speculative private land ownership and the absence of appropriate land-use planning (Evers, 1984). Existing land-use plans may seem ineffective, according to Western urban planning theory that negatively regards mixed land uses. However, urban-rural mixed areas in the urban fringe offer the potential for resource circulation and for the development of sustainable societies through the harmonization of human beings and the environment (Yokohari et al., 2000). In this study, we supposed nitrogen resources circulation by utilization of compost generated from municipal solid waste in the neighboring agricultural fields. We investigated the current situation of supply and demand potential of compost, and those estimated from land-use change in variation of population density, in order to illustrate the shift of supply-demand balance of compost between urban and agricultural sectors according to peri-urban development in an urban-rural fringe area of Bangkok. Materials and Methods Study Area We targeted Bang Maenang District in Nonthaburi Province as a study area, and conducted the study focusing on the area along the two canals in the district, Bang- Kho Canal (Canal 1) and Bang-Kra-Boo Canal (Canal 2). We chose these canals because development of a new residential area was active along the canals, and because there is a certain difference in robustness of the developments, although they are neighbors. Basins of Bang-Kho Canal and Bang-Kra-Boo Canal were divided for descriptive purposes as C1-1 to C1-4 and C2-1 to C2-2, respectively (Figure 1). The area of basins of Canal 1 and 2 was 1.95 km 2 and 1.10 km 2. The total area of the target site was 3.05 km 2. Land-Use Change and Population Land-use change due to urban development in the target area between 2003 and 2007 was spatially investigated using GIS software (ArcGIS, ESRI). The 2003 urban plan- ning base map in vector format with a scale of 1:4000 (Department of Public Works and Town & Country Planning, Ministry of Interior, Thailand) was obtained and used for GIS analysis. The map for 2007 was constructed by editing a 2003 vector map through on-screen visual interpretation of ALOS PRISM satellite imagery observed in An area of a residential land use, the number of houses, an area of rice fields and vegetable fields in each year and their changes were calcu-

3 Supply-Demand Balance of Compost between Urban and Agricultural Sectors 291 Fig. 1 Target area in Bang Maenang, Nonthaburi, Thailand. lated by overlaying the 2003 and the 2007 maps. Population was extrapolated from the average household size: 3.4 persons/household (Thai Census, 2000). Nitrogen Demand in Agricultural Sectors Demand for nitrogen in agriculture fields in the target area was estimated based on field surveys. The amount of applied nitrogen in rice and vegetable fields was 9.61 and 6.67 g/m 2 /year, respectively, which was estimated from the amount of applied fertilizer and nitrogen contents in the fertilizer according to the results of interview surveys of the farmers. Nitrogen Discharge from Urban Sectors The amount of municipal solid waste generation and nutrient contents in the waste were obtained by field surveys. We investigated solid waste generated by 24 randomly selected households in Bang Maenang (Hiramatsu et al., 2008). The amount of municipal solid waste generation was 346 kg/household/year, and the average nitrogen content was 4.02%. Wastewater discharge was assumed to be equal to the amount of water usage, 279 L/person/year, which was obtained at Water Management Association in Nonthaburi. A nitrogen concentration in wastewater was as-

4 292 R. Honda et al. sumed as 50 mgn/l (Lee and Wong, 2003). Amount of nitrogen discharge from a residence was estimated as 47.5 g/household/year (Honda et al., 2010). Estimation of Supply-Demand Balance in Variation of Population Density The residential area was estimated from population as an independent variable. All residents in the target area were assumed to live in detached houses. The average space per household was 240 m 2 /household, which was obtained by analysis of the GIS data. Land for rice fields, vegetable fields, and other uses were allocated to the remaining area with the same ratio as in 2007, which was 2:1:1 along Canal 1 and 4:5:1 along Canal 2. Nitrogen supply potential in compost was estimated from the amount of municipal solid waste. The amount of municipal solid waste generated with a nitrogen basis was calculated from a given population value and the number of households. Nitrogen discharge from wastewater was also estimated from the number of households. Nitrogen loss by composting was estimated as 43.2% by N-loss equation (Equation 1) (Kirchmann, 1985). The C/N ratio of the solid waste was according to the result of field surveys. N loss ratio = C/N ratio (1) Nitrogen demand potential was estimated from the amount of applied nitrogen in fertilizer and total area of rice and vegetable fields. We assumed that demand for nitrogen in compost was half of that in fertilizers. Results and Discussion The Current Situation of Balance of Supply and Demand Potential Population in the target area was estimated to increase 50% from 5,100 in 2003 to 7,600 in 2007, approximately. Rate of land-use change were faster along Canal 1 than Canal 2, and in the downstream area, which is closer to the urban center, than in the upstream area (Figure 2). Along Canal 1, agricultural area decreased 12 % and residential area in- creased 25% from 2003 until Along Canal 2, agricultural area decreased 10 % and residential area increased 9% (Table 1). Nitrogen demand in fertilizers in agricultural sectors was estimated to decrease 14 and 12%, while generation of municipal solid waste increased by 52 and 4% along Canal 1 and 2, respectively. Compost supply was redundant along Canal 1, while it was deficient along Canal 2. In total, though supply and demand balance almost matched in 2003, 42% was estimated to remain redundant in 2007, according

5 Supply-Demand Balance of Compost between Urban and Agricultural Sectors 293 Table 1 Land-use change of the target area from 2003 until 2007 in Bang Maenang, Nonthaburi, Thailand. The values in parentheses are ratios in total area. Table 2 Supply and demand potential of nitrogen. to reports of an increase of supply from urban sectors and decrease of demand in agricultural sectors. Municipal solid waste in this area was basically collected and brought to the waste disposal site located in the northern part of Nonthaburi province. According to the interview survey to the farmers, most of the farmers did not use compost or manure, or they used only small amount of compost in personal basis. Estimation of Supply-Demand Balance in Variation of Population Density The supply and demand potential of compost in variation of population density is shown in Figure 3. The estimated lines are probably reasonable because most of plots corresponding to observed data in Nonthaburi are almost on the line. The lines of supply and demand potential meet when population densities are approximately 1,270 and 1,390 along Canal 1 and 2, respectively. Ratios of residential area corresponding to these points are 9 and 10%, respectively. The population density where

6 294 R. Honda et al. Fig. 2 (a) Land-use change from 2003 until 2007 in the target area in Bang Maenang, Nonthaburi, Thailand. The circled area shows a newly developed area. (b) Land-use change from 2003 until 2007 in the target area in Bang Maenang, Nonthaburi, Thailand. The circled area shows a newly developed area.

7 Supply-Demand Balance of Compost between Urban and Agricultural Sectors 295 Fig. 3 Estimated supply-demand balance of compost in relation to population density. The plots shows the estimation from GIS data in 2003 and supply and demand potentials meet has a similar value although the ratio of rice fields to vegetable fields is significantly different between Canal 1 and Canal 2. Impacts of transportation cost on compost circulation are probably limited because total area of the target area was as small as 3 km 2. However, the values obtained in this study should be evaluated carefully especially in application to larger area, because they were focused only on balance of amount of supply and demand potential. Not only municipal solid waste but also domestic wastewater has a significant amount of nitrogen discharge. If utilization of nitrogen in wastewater is possible, supply and demand potential equals in lower population density. However, nitrogen circulation from wastewater, such as utilization of composted activated sludge was probably difficult in the current situation in the target area, because most of the wastewater was discharged directly to the canals without proper treatment. It was difficult to utilize a large part of the discharged nitrogen in the study area since nitrogen discharge was much larger than nitrogen demand in the area. Instead, the proper collection and treatment of surplus nitrogen was necessary in order to prevent it from discharging into the canal and from burdening the canal water environment. Conclusions We could observe increase of residential area and decrease of agricultural area according to population increase induced by the peri-urban development. As a result, supply potential of compost from municipal solid waste increased, while demand potential in the agricultural fields decrease. In the study area in Bang Maenang, Nonthaburi, Thailand, 42% of supply potential estimated to exceed demand balance in 2007, while they almost equaled in The population density where

8 296 R. Honda et al. supply and demand potential balance was estimated as approximately 1,300 1,400 persons/km 2. Since the population density in the study area exceeded the estimated value and a significant amount of nitrogen was also discharged from wastewater, the proper collection and treatment of surplus nitrogen was required to protect the canal water environment. Acknowledgements This study was supported by the Global Environment Research Fund (RF-067) of the Ministry of the Environment, Japan, and partly by the Ministry of Education, Culture, Sports, Science and Technology through Special Coordination Funds for Promoting Science and Technology. We thank Dr. Chart Chiemchaisri, Mr. Wajus Kanjana, Ms. Jutamas Kaewsuk, Mr. Rukapan Weerapong for their support in our field surveys. We also appreciate the local government and residents of Bang Yai and Nonthaburi Province for their kind cooperation. References Evers, H.D. (1984). Urban landownership, ethnicity and class in Southeast Asian cities. International Journal of Urban and Regional Research 8, Hiramatsu, A., Hara, Y., Sekiyama, M. and Honda, R. (2008). Municipal solid waste flow and waste generation characteristics in an urban-rural fringe area in Thailand. Waste Management Res. 27(10), Honda, R., Hara, Y., Sekiyama, M. and Hiramatsu, A. (2010). Impacts of housing development on nutrients flow along canals in a peri-urban area of Bangkok, Thailand. Water Sci. Technol. 61(4), Kirchmann, H. (1985). Losses, plant uptake and utilisationof manure nitrogen during a production cycle. Acta Agriculturae Scandinavica Supplementum 24, Sveriges Lantbruksuniv, Uppsala, Sweden. Lee, M.C. and Wong, P.K. (2003). Municipal wastewater treatment. In: Microbial Biotechnology: Principles and Applications, Y.K. Lee (Ed.), World Scientific, Singapore, pp PCD (2007). Water quality standards. Pollution Control Department, Ministry of Natural Resources and Environment, Thailand. serv/en reg std water.html. Takaya, Y. (1987). Agricultural Development of a Tropical Delta: A Study of the Chao Phraya Delta. University of Hawaii Press, Honolulu. Takiguchi, H., Takemoto, K., Hotta, Y. (2007). International development of the 3Rs and issues in Asia. Journal of the Japan Society of Civil Engineers 63(4), [in Japanese]. Yokohari, M., Takeuchi, K., Watanabe, T. and Yokota, S. (2000). Beyond greenbelts and zoning: A new planning concept for the environment of Asian mega-cities. Landscape and Urban Planning 47,