Year: 2007
Type: dissertation
Abstract: In this case study, a nutrient budget was made to estimate import and export flows of \nphosphorus (P) on the ecotourism resort of Chumbe Island, Zanzibar. The P content in \nimported foods and goods was calculated using supply lists containing information on \nquantities of items bought and standard food composition data. Foods and goods not \nincluded in the standard data were subsampled for P analysis. \n \nTotal P import to Chumbe Island was 41.0 kg/year. More P was imported with foods to the guest kitchen than to the staff kitchen (13.2 and 9.1 kg P/year, respectively) although the guest kitchen served fewer meals (9333 and 14113 meals, respectively). This is explained by the more P-rich foods served in the guest kitchen. When charcoal and firewood were included, the staff and guest kitchens imported equal amounts of P since the staff kitchen used both firewood and charcoal while the guest kitchen only used \ncharcoal as a complement to gas. \n \nAsh and biodegradable waste such as fruit peel were composted on-site and used to \nfacilitate the degradation process in composting toilets. Biodegradable waste from both \nkitchens contributed 4.8 kg P/year to the compost heap, while the ash from kitchen stoves \ncontributed an estimated max. 17.4 kg P/year. Despite uncertainties regarding P amounts \nin the kitchen waste, estimations showed that P was lost from the compost heap during all \nstages of decomposition. Animals and birds scattering the compost during feeding and \nleaching during the rainy season are possible reasons for these losses. \n \nIn the guest kitchen greywater system, sludge and grease were removed before the \ngreywater was discharged into a small mangrove swamp, while staff kitchen greywater \nwas poured untreated into a mud-hole in rocky ground. The guest kitchen contributed \nslightly more to P discharge (0.3 kg P/year) than the staff kitchen (0.2 kg P/year). The \nsludge (discharged at unspecified locations on Chumbe) contained another 0.1 kg P/year. \nThe grease (added to compost) contained no P. \n \nFood scraps from both kitchens containing 2.4 kg P/year and composted toilet waste \ncontaining 21.6 kg P/year were re-exported to Zanzibar, i.e. approx. half the P imported \nwas exported. The other half of imported P was lost from compost, greywater outlets, as \nsludge or dissipated through fly ash dispersal. \n \nTo avoid P accumulation on Chumbe Island, I recommend that all toilet waste and ash be exported in future, since they contain nutrients useful on agricultural land on Zanzibar but harmful to the reef. Furthermore, Chumbe Island management should act to counteract current sources of P losses.
Author: Bodil Lindström
Language: English
Subfield: Waste Management and Disposal
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1826890914