Suitability of Kibuye Market Organic Waste for Composting as a Means of Solid Waste Management for Kisumu City

Purpose: Organic waste comprises most of the waste in dumpsites in Kenya and this causes environmental challenges at such sites. With Kisumu as a case study, the purpose of this work was to explore the suitability of organic wastes from Kibuye market, hotels and livestock farms for compost manure making as a means of organic solid waste management. Methods: The study was cross-sectional in design. Compost manure was prepared from organic market waste, hotel food remains and livestock dung. Samples were then taken to a laboratory to test for the content of nitrogen, phosphorous (P 2 O 5 ) using TES/06/TM/21 and TES/06/TM/24 methods respectively and potassium (K 2 O) using Atomic Absorption Spectrometry (AAS) method as well as for heavy metals (Cd, Cu, Fe, Pb) while the Ph of the compost was tested by KS-158 method. Results: Laboratory tests for the presence of important crop elements were Nitrogen (0.4%), Phosphorous (0.4%), and Potassium (0.9%) whereas for heavy metals were Cd=Nil, Cu=10.1, Fe=1.08, Pb=Nil, and pH=8.4. Conclusion: It is safe to use organic waste from Kibuye as augmented by those from hotels and livestock farms for composting as a means of organic solid waste management if other supporting systems are in place.


INTRODUCTION
Sustainable Integrated Solid Waste Management (ISWM) is one of the important obligatory functions of any Urban or City authority. It refers to all activities pertaining to the control, collection, transportation, processing, treatment and disposal of wastes in accordance with sustainability principles. The fundamental objective of solid waste management is to protect the health of the public, promote environmental quality, and create employment through a circular economy of waste resources [1]. Many urban centers in Kenya, including Kisumu City, generate a lot of organic matter. However, proper management of such wastes have proved a challenge nationally. Consequently, a larger proportion of such waste end up in drainage channels, open spaces and municipal dumpsites where they are poorly managed thus clogging them [2]. Even though the advantages of organic manure are widely known; advantages which include increasing soil fertility, improving soil physical conditions and microbiological conditions as well as crop yield [3,4], lack of knowledge of their exact nutritive value and possible contaminants deter farmers from utilizing them on their farms. Consequently, they are left to fill dumpsites, be fed on by scavenging livestock and birds or left to decay thereby emitting repugnant odours and greenhouse gases which cause air pollution. These gases contribute to global warming with its attendant environmental hazards. In order to contribute to the mitigation of these effects, this study sought to determine the suitability of organic wastes from Kibuye market for compost manure as a means of solid waste management in Kisumu City. Specifically, this study assessed the nutritive value of such manure and the presence of heavy metal contaminants.

METHODOLOGY
The study design adopted by this investigation was cross-sectional in nature in that the organic matter used for compost making was only from one season. It was not a year-round exercise. Materials required for composting were measured by a wheelbarrow of 0.045m 3 capacity. The amounts, therefore, were 5 wheelbarrows of each of the following; 1) vegetable waste, 2) avocado and Irish potato wastes, 3) mango and orange wastes, 4) tomato and carrot wastes, 5) pineapples and green banana peels, and 6) guano. Additional materials were 1 wheelbarrow each of banana peels, and hotel food remains, and, 2 wheelbarrows each of saw dust, and cow dung. In order to make the compost, a secure secluded spot in the market backyard was cleared for the compost heap. Thereafter, the vegetables, avocado and Irish potato, mango and orange, tomato and carrot, pineapples and green banana peels were mixed in a heap and covered with polythene (1000 gauge) to prevent unnecessary moisture, (e.g. from rain) from being added into the mix. This was regularly checked and turned for mixing to realize even decomposition. At four weeks, the guano, saw dust and cow dung were again added and the whole mixture thoroughly mixed for even distribution of the materials and proper composting. The mixture was again covered with polythene and left for three weeks after which it was ready. It was once again mixed for aeration then moved under a shade, covered with polythene, and left for one and a half weeks to dry. Thereafter, it was ground using fabricated grinding machine to achieve homogeneity of grain size. This was repeated two more times so that there were a total of three preparations. Samples from these three preparations were taken to a government facility (

RESULTS AND DISCUSSIONS
First, we present and discuss laboratory findings on nutrient content followed by the presence of heavy metal contaminants. Thereafter, we wind up this section with a conclusion and some recommendations.

Nutrient content
Laboratory tests for nutritive content are as indicated in Table 1. Nitrogen and phosphorous (P 2 O 5 ) content were 0.4% of the sample mass while for potassium was 0.9%. These nutrient contents are not static but expected to vary with different proportions of and types of brown and green matter for composting. These findings are, however, important as a point of information for farmers that would want to apply this organic manure on their farms. Moreover, these lab results can inform efforts to augment the compost with inorganic fertilizer in order to meet specific soil and plant nutrient requirements; a practice that is recognized by other studies [5]. This further helps allay farmers fears, as we have noted locally, that in buying or making composts, they are not sure the nutrient composition is suitable for their soil and plant needs. The greatest nutrient benefit of compost, nevertheless, is that it releases nutrients over a long period of time as it further decays thus reducing the need to continually fertilize soils.
Composting holds the promise of providing a sustainable management solution to the 60 -65% organic waste [6] that usually comprise the waste at Kachok dumpsite, a dumpsite that is currently being relocated. However, a number of challenges still stand in the way of this realization. Notable among these obstacles are that organic wastes are not separated at source and urban residences are too small to manage them within their compounds as also observed in Uganda [7]. Furthermore, the City does not have composting spaces in its solid waste management dumpsite at Kachok. If the City solves these bottlenecks in its future strategies for solid waste management, then the one hurdle that will remain is to create demand for the compost by farmers.

Presence of heavy metal contaminants
Lab results indicate that the compost was free from Lead and Cadmium contamination. The content of Iron and Copper were at 1.08%m/m and 10.1mg/Kg respectively. The value of Iron was slightly above the minimum quantity (10 mg/kg) required in soils [8] while that of Copper was way below the threshold value (100mg/kg) according European Standards [9]. These results indicate that the compost is free from heavy metal contamination and thus suitable for farming as a waste management strategy. These values are most likely due to the fact that they were separated at source and that sludge was not used. Had they been sourced from sludge or the City's dumpsite, they could perhaps have been contaminated by chemicals from medicines, pesticides, and other polluting substances (e.g from electronics) that find their way into sewerage systems or get dumped at dumpsites [10]. Organic wastes from markets and hotels, when captured at source, often escape this contamination. Even though heavy metals occur naturally in the environment, when their concentrations exceed a certain limit, they become toxic to plants and humans.
The availability of heavy metals for plant uptake and the actual uptake by plants is greatly a function of soil pH besides other factors such as plant absorption and metabolism characteristics [11]. Studies indicate that the lower the pH value, the more available heavy metals are for plant uptake [12,13]. Our findings indicated that the pH for the compost was 8.4, which is within the acceptable range (6.5-8.5) for most plants to grow and limit the availability of heavy metals according to Kenyan standards. Even though pH may fluctuate in soil overtime, the value of our compost is suitable for farms and limits the availability of heavy metals for plant uptake in a manner not to cause toxicity (Table 2) [14][15][16].

CONCLUSION AND RECOMMENDATIONS
Since the compost manure was free from heavy metal pollution according to Kenyan and International standards, it can be utilized as a means of solid waste management in Kisumu City. This will have the triple advantage of: 1) sustainably managing organic solid waste which comprise the greater percentage of solid wastes reaching Kisumu's dumpsite, 2) creating business and 3) improving food production through improved soil quality in the region. This is particularly important noting that a greater proportion the organic waste reaching the dumpsite comes from Kibuye market and hotels. Their utilization for compost making, therefore, is a viable and promising way to sustainably manage them. Furthermore, almost all of the city's waste can be managed this way if separation at household can be achieved, as is recommended by other studies. Already, the City, through its manager, Doris Ombara, has indicated that the City plans to manage its organic waste through composting and biodigesters. However, in order for such initiatives to succeed, as the objective of this study envisions, further steps need to take place. Such include waste separation at source to avoid contamination, awareness creation among farmers regarding the importance of compost or organic manure, regular testing of compost for nutrient content and possible contamination, creation of space(s) for composting at the City level and proper marketing of the composts.