Project Abstract

<p>&nbsp;                  <b>ABSTRACT</b>&nbsp;</p><p>Composting of Municipal Solid Waste (MSW) has received renewed attention as a result of increasing waste disposal cost and the environmental concerns associated with using landfills. A targeted end use of the compost is for horticultural crop production. Currently, quality standards for MSW compost are lacking and there is the need to establish them. Elevated heavy metal concentrations in MSW compost have been reported; however, through proper sorting and recycling prior to composting, contamination by heavy metals can be reduced Compost has been shown to be useful in horticultural crop production as it improves soil physical properties, such as lowering bulk density and increasing water-holding capacity. Compost enhances supply of essential nutrients to some extent. However, supplemental fertilizer, particularly N, is usually required. A pilot dry digestion composting plant was thus established on the campus of the University of Nigeria, Nuskka. The setup was to assess the effectiveness of processing of organic municipal waste to obtain biogas for domestic use and digestate for the purposes of composting. The different composts obtained were then used in planting green beans (Phaseolus vulgaris). The aim of this work was to assess the effects of the different composts on the performance of green beans. Results of this work identified and highlighted the superiority of fertilized crops over non-fertilized ones in terms of growth and dry matter accumulation. A long term research should be carried out on the effects of prolonged use of composts produced by vermicomposting, co-composting and windrow composting on crop and soil. Public awareness on the effects of compost on soil, crop yield and environment should be intensified. <br></p>

Project Overview

<p> <b>1.0 INTRODUCTION&nbsp;</b></p><p><b>1.1 BACKGROUND STUDY</b></p><p>Rapid population growth and urbanization worldwide, have led to an enormous increase in solid waste generation per unit area (Kassim &amp; Ali, 2006). The management of specific waste streams such as biodegradable waste represents an important element of the strategy to help reduce the impact of waste on the environment. Considering the fact that the largest fraction of waste in developing countries is organic in nature and therefore amendable to anaerobic digestion, it makes environmental and economic sense to survey this option (Mbuligwe &amp; Kassenga, 2004). Biological treatment of biodegradable waste such as composting and anaerobic digestion (AD), has several advantages. It contributes to the reduction of greenhouse effect, as it diverts biodegradable waste from landfills where methane is produced and emitted in an uncontrolled manner to the atmosphere (Burri &amp; Martius, 2011). When used as soil amendment in agriculture it maintains or restores soil productivity. Its humified organic matter provides a unique property of compost itself. Another promising treatment option is anaerobic digestion which produces an energy-rich biogas and digestate. The latter one can be used as a soil amendment or fertilizer for arable land. Anaerobic digestion is a biological process where a diverse group of micro-organism convert the complex organic matter into a simple and stable end product in the absence of oxygen. This process is very attractive because it yields biogas, i.e. a mixture of methane (CH4) and carbon dioxide (CO2) which can be used as renewable energy source. The dry anaerobic digestion (AD) process is an innovative waste-recycling method to treat high-solid content bio-wastes. It is done at a solid concentration higher than 10% and enables a higher volumetric organic loading rate, minimal material handling, lower energy requirements for heating, limited environmental consequences and energetically effective performance. Dry anaerobic digestion [&gt;15% total solid (TS)] has an advantage over wet digestion (&lt;10% TS) because it allows for the use of a smaller volume of reactor and because it reduces waste water production. Additionally, it produces a fertilizer that is easier to transport. <br></p><p> Soil fertility is a limiting factor to agricultural productivity in many parts of the developing world. Among the problems of tropical soils, soil acidity, characterized by low pH, excessive aluminium, deficient calcium and low organic matter are most prominent (Hue, 1992). Tropical soils are often prone to strong phosphate fixation which renders phosphorus unavailable to plant. Such soils require extremely high phosphate application in order to alleviate the effect of phosphate fixation. Soil acidity and mineral deficiencies can be corrected by applying lime and fertilizers to the soil. Unfortunately, lime and fertilizers are not always easy options available to resource-poor farmers (Hue, 1992). However it is reported that green manures and composted organic material increase soil organic matter (SOM), provides nutrients for plant growth, alleviate aluminium toxicity and render phosphorus more available to crops (Beltran et al., 2002). This increased availability of phosphorus is probably caused by the reaction of organic matter-derived molecules with soil minerals (Hue, 1992). <br></p><p>&nbsp;The interests of urban waste recycling go well with the promotion of urban agriculture since urban and peri-urban farmers are in need of organic matter as soil conditioner. In a region of abundant rainfall, Nuskka possesses great potential for implementing planned organic waste collection and processing for local food production. <br></p><p>  <b>1.2 STATEMENT OF THE PROBLEM</b>&nbsp;</p><p>According to UNEP (2005) the rate of waste generation generally increases in direct proportion to that of a nation’s advancement in development, and failure to provide a management system could result in greater environmental degradation with increase health risk to the urban population (UNEP, 2005). In Nigeria, all district, municipal and metropolitan assemblies give urban sanitation and waste management a priority in their development objectives.&nbsp;</p><p>However, their ability to contain the problems of waste management is declining, because of rising capital cost for plant and equipment, increasing operation and maintenance cost, the rapid spatial and population growth of most urban areas with decreasing coverage levels, and increase in levels of waste generated, confronted by increasing public demand for improved services (Salifu, 1995). <br></p><p> Due to Nuskka's inability to handle SWM adequately, it has been supported largely in the delivery of environmental sanitation services over the past decade by central government/external donor interventions. However, as with other infrastructure and service sectors, the overuse of equipment and facilities to terminal ruin is the practice (Salifu, 1995). A pilot dry digestion composting plant was thus established on the campus of the University of Nigeria, Nsukka (UNN). The aim of this setup was to assess the effectiveness of processing of organic municipal waste. The primary purpose was to obtain biogas for domestic use. One of the potential benefits of the produced digestate is its potential to be used for the purpose of composting. The produced digestate thus had to be evaluated in terms of its agronomic potential and benefits. This is what necessitated this study which seeks to evaluate and compare the effects of using the fresh and post-treated (composted) digestates for crop production. <br></p><p> <b>1.3 JUSTIFICATION</b></p><p>Agricultural systems produce organic wastes for which the soil has the capacity to assimilate as well as waste from different sources (Soliva, 1994, Soliva &amp; Felipo, 2003). The proper management of organic waste through soil management could lead to economic and environmental benefits which contribute to sustainable development. It is therefore necessary to take into account conservation and crop nutritional needs when dealing with agro-waste. <br></p><p> <b>1.4 OBJECTIVE</b></p><p>The main objective of the study was to assess the impact of unprocessed and composted digestate from dry fermentation as an alternative to synthetic fertilizers on green beans yield. <br></p><p> The specific objectives of the study were to: <br></p><p> 1. Compare the effects of different unprocessed and composted digestates on growth parameters of green beans.&nbsp;</p><p>2. Compare the effects of different unprocessed and composted digestates on biomass and nutrient levels of green beans. <br></p>