Essais de valorisation des déchets solides ménagers biodégradables de la ville de Bujumbura par compostage.

Abstract

The problem of solid wastes in Bujumbura Capital is acute following the pace of its galloping demographic evolution and growing urbanization which are the cause of the increase in waste. This study of composting household solid waste generated in Bujumbura city was conducted in order to contribute to the protection of the environment through the recovery of the organic fraction of household solid waste into a quality organic fertilizer. To carry out this study, two kinds of windrow (A1 and A2) have been developed based on bush straw, grass clippings, peelings mixed with adjuvants consisting of cow dung (A1) and hen droppings (A2). A physicochemical characterization was carried out in order to determine the amount of each component necessary to form an initial C/N ratio of 30 for the two windrows. The process of composting by turning the aerated windrows was chosen and the process lasted 70 days. For windrow 1, the total organic matter (TOM) content of composted waste is 86.54%. Analysis of the different physico-chemical; microbiological, biological and agronomic parameters of the compost obtained from windrow 1 after 70 days reveal the following values: TOC (15.24±0.15 %); TOM (C1: 33.55±1.31 %); NTK (C1: 1.19±0.05 %); C/N (12.82); pH (8.8); P (1180.61±51.72 ppm); N+P+K (C1: 2.70±0.00 %). For windrow 2, the total organic matter (TOM) content of composted waste is 86.49 %. Analysis of the different physicochemical; microbiological, biological and agronomic parameters of the compost obtained from windrow 2 after 70 days reveal the following values: TOC (15.85±0.17 %); TOM (37.56±1.02 %); NTK (1.19±0.05 %); C/N (14.28); pH (8.4); P (1150±46.48 ppm); N+P+K (2.68±0.05 %). The average germination indices of corn and peanut seeds applied to 25% and 75% compost extracts (IG25 and IG75) are greater than 50%. The lead, nickel, cobalt and manganese contents are respectively 4 mg/kg; 3.58mg/kg; 3.57 mg/kg and 124 mg/kg. The growth rate of the amaranths applied to the D25% and D50% doses is higher than that of the control with a high growth rate for the application of the D25% dose. All these values are within the range of values appreciable by compost quality standards and show that these composts have a good quality and could improve soil fertility.