WASTE TO ENERGY (MARCH FREE REPORT)

Waste to energy refers to a technology that treats waste to recover energy in the form of

heat, electricity or alternative fuels such as biogas from the solid waste UNEP (1996).

The scope of the term ‘Waste-to-Energy’ is very wide, encompassing a range of technologies of different scales and complexity. These can include the production of cooking gas in household dig-esters from organic waste, collection of methane gas from landfills, thermal treatment of waste in utility size incineration plants, co-processing of Refuse Derived Fuel (RDF) in cement plants or gasification. This research takes a very broad understanding of Waste to energy, referring to large scale plants at the municipal level using the technologies of incineration, co-processing, anaerobic digestion, landfill gas collection and pyrolysis/gasification. These five technologies apply to different waste streams and have different functions and characteristics. Their applicability must therefore be assessed independently based on the local context and waste stream discussed USEPA (2002).

Growing concerns regarding shrinking natural resources, contribution of improper waste management to global warming and shortage of power generation have triggered discussions regarding waste as a resource in general and Waste to Energy concepts in particular. Decision makers at national and local level in developing and emerging countries may be tempted by technology providers who promise that Waste to Energy plants will solve their waste disposal problems, create a lucrative business opportunity and contribute positively to energy supply. As such, waste seems to be an ideal feedstock for energy recovery. So far however, some projects built in developing and emerging countries have operated successfully in the long term (Senkoro, 2009; Schiibeler, 2006).

Some positive experiences so far lie in state-of-the-art co-processing in cement kilns and landfill gas collection applied to sanitary landfills. However to date, there are many anaerobic digesters fed with segregated organic MSW in successful operation on a large scale in developing countries, more than a handful of waste incinerators in continuous operation in developing countries in Africa and Asia ( Humphrey and Water, 2001).

 Recycling Rand et al, (2000) notes that one of the approaches to waste management is by separating or sorting waste generated and eventually using it for other form of production. Separating waste materials at the household level occurs to some extent almost universally, and prevents the most valuable and reusable materials from being discarded. Following in-home retention of valuable material, waste-pickers currently remove most valuable materials either before garbage enters the waste stream or en route, especially in the lower and middle-income areas of many municipalities. In Uganda sorting of waste has not been successful for unclear reasons (UNEP, 2006). Companies could help to divert many materials out of the waste stream. Since recycling materials is a financially viable undertaking, small enterprises have and will continue to spring up whenever there is an opportunity. In fact the theft of source separated 17 recyclable materials has been documented in many pilot schemes in both developed and developing nations (UNEP, 2006). Municipalities should not only recognize the trade in recyclables, they should embrace it. By allowing small enterprise to address the problem, valuable funds are saved, jobs are created and landfill space is saved. Perhaps through micro-loans or some small-scale assistance, local governments could support and legitimize these entrepreneurs. Johannes sen (2009) asserts that recycling inorganic materials from municipal solid waste is often well developed by the activities of the informal sector although such activities are seldom recognized, supported, or promoted by the municipal authorities. Some key factors that affect the potential for resource recovery are the cost of the separated material, its purity, its quantity and its location. The costs .of storage and transport are major factors that decide the economic potential for resource recovery. In many lowincome countries, the fraction of material that is won for resource recovery is very high, because this work is done in a very labour-intensive way, and for very low incomes. Recycling has the advantage of reducing costs of the disposal facilities, prolonging the site span.Composting A somewhat more low-technology approach to waste management is composting. The waste of many developing nations would theoretically be ideal for reduction through composting, having a much higher composition of organic material than industrialized countries. For example, generally, in developing countries, the average city’s municipal waste stream is over 50% organic material (Hoornweg et al., 2002). Studies in Bandung, Indonesia and Colombo, Sri Lanka have revealed that residential waste composed of 78% and 81% compo-stable material, and market waste 89% and 90% compo-stable, respectively. However, composting has not been overwhelmingly successful and widespread in practice throughout the developing world. Although well documented in China and other areas of eastern Asia, composting projects have had a spotty record throughout Africa, Latin America and elsewhere, and have had the largest number of failed facilities worldwide (UNEP, 2006). 18 There are many advantages to composting. First and foremost, it would reduce, in some cases significantly, the amount of waste requiring ultimate disposal, extending the life of landfills. When done correctly, the end result becomes a useful product, capable of being used at the household or farm level to augment soil nutrient levels and increase organic matter in the soil, increasing soil stability. If the product is of high enough quality and markets exist, the product can be sold. Environmentally, the process by which composting decomposes organic waste is preferable to landfill processes. In a landfill, bacteria break down organics anaerobically in the absence of oxygen, resulting in the releases of methane gas which may be used for home actives. When properly composted, however, the organic matter is decomposed using an aerobic process, which produces no methane by-product (Mugisha, 2010).