The Use of Organic Waste as an Eco-Efficient Energy Source in Ghana


The problem of municipal solid waste (MSW) management has been an issue of global concern in recent times and has engaged governments and local authorities in their quest to manage solid waste in a sustained manner. One proposition which has the potential of solving three problems at the same time is the use of the biodegradable component of MSW as a source of energy to augment energy supply. This research therefore assessed the use of the organic fraction of MSW as an eco-efficient energy source in Ghana. A study of Ghana’s solid waste profile was undertaken and the fraction of biodegradable component was found to be approximately 60%, with a heating value of 17 MJ/kg and a moisture content of 50%. Moreover, it was established that 0.5 kg of solid waste is generated daily by each Ghanaian, meaning that about 5610 tons of the organic fraction could be made available every day to generate energy to the national grid. It was also established that waste disposal in Ghana is largely by way of open dumping as primary collection of waste from households in Ghana is limited to high-income communities which represent only 11% of the population, whereas secondary collection from transfer points to the disposal facilities is inefficient. With representative power output of 1.66 MWh/tonne a total of 3320 GWh of energy can be produced annually from the 4 proposed plants, generating net revenue of about $111,600,000. As an optimizing step, a waste incineration scheme was suggested in which the off-gases produced from organic waste combustion could be used to produce electrical power with steam in a multi-stage heat exchanger-steam turbine configuration, and the off gases again used for pre-drying of the organic waste in a cycle. A state-of-the art waste incineration technology was used as a model and adapted to suit Ghana’s tropical conditions. MSW combustion releases less CO2 for the same power output (837 Ib/MWh) than any of the other conventional fuels do, and is therefore a good fuel for the fight against climate change.

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Ohene Adu, R. and Lohmueller, R. (2012) The Use of Organic Waste as an Eco-Efficient Energy Source in Ghana. Journal of Environmental Protection, 3, 553-562. doi: 10.4236/jep.2012.37066.

1. Introduction

As the world economy grows, so does the amount of waste generated. There is thus an increasing burden on governments and municipal authorities to find new ways of handling solid waste in an efficient and cost-effective manner.

Thermal treatment of domestic waste with energy recovery is already a popular technology in many advanced countries and is fast catching up in some developing countries today. About 35 countries worldwide currently employ Waste-to-Energy (WtE) technologies using about 130 million tons of waste annually, and this benefits some 2.6 billion people [1]. In the U.S alone, the amount of waste converted into energy is about 30 million tons a year and this produces about 2800 MW of power.

Over the past 100 years, countries in Europe such as Denmark and Sweden have utilized waste for electricity and district heating, with Denmark deriving 4.8% of her energy from this technology [2,3]. Waste-to-energy technology has particularly benefited countries with small land size such as Japan since it has been known to reduce original volumes by up to 90% and weights to as high as 67% [4].

In developing countries like Ghana where solid waste disposal is increasingly an environmental burden with its attendant health hazards, the idea of converting the organic fraction of municipal solid waste into energy for the national grid is a welcome proposition towards reducing volumes of domestic waste to be disposed of or land-filled. In addition, the conversion of organic waste into energy would doubtless cut down on the amount of fossil-derived fuel needed for the generation of power in Ghana. This will reduce the amount of CO2 emissions and of other noxious gases that are produced from fossilfired power plants.

At an annual growth rate of 3%, Ghana’s population has been estimated to double every 26 years, rising from a figure of about 6 million at independence in 1957 to an estimated 23 million in 2007 [5]. Thus, the population reached about 24 million by 2009. This trend, coupled with a growing GDP means that the amount of municipal solid waste (MSW) generated is obviously on the increase.

Studies undertaken by [6] suggest, based on an estimated population at the time of 18 million that about 3.0 million tons (2.7 million tonnes) of solid waste were generated annually in Ghana, and that on average, each person generated daily 0.45 kg of solid waste. More recent data suggest that every Ghanaian generates 0.50 kg of solid waste daily [7]. Thus, the per-capita generation of waste in Ghana amounts to some 183 kg per year. This is lower than values in advanced countries which range between 250 kg and 750 kg per capita [8]. Most of these wastes find themselves in open dumps and water bodies creating nuisance in the environment, therefore any attempt to convert them into energy is a laudable idea. This paper therefore looked at the possibility of using the organic waste fraction to produce energy in Ghana by employing the Bremerhaven waste incineration plant model being used in Germany.

2. Viability of Waste Incineration in Ghana

2.1. Assessment of the Heating Value of Organic Waste in Ghana

The heating value or energy density of municipal solid waste is very much dependent on the moisture content of the waste. High moisture content in the waste considerably lowers its heating value. Thus, a distinction ought to be made between the minimum heating value of MSW which contains water and the maximum heating value of MSW which is dry.

Unlike conventional fuels which have negligible water content and therefore have practically one heating value, municipal solid wastes have high water content and therefore big differences between the minimum and maximum heating values. This means that initial energy input is required to raise the temperature of the waste to the boiling point of water and also to vaporize the water. This effectively reduces the net energy output obtainable from the combustion of MSW.

Studies undertaken by [9], to evaluate the energy potential of MSW from three zones of Accra Metropolis, the capital of Ghana, found the average moisture content to be approximately 50% (Table 1).

It can be seen that the mean gross calorific value of

Table 1. Mean Energy densities of MSW components from urban waste zones in Accra, Ghana.

MSW in Ghana is approximately 17 MJ/kg and is largely dominated by the organic/putrescible component which constitutes about 60% of the average waste stream.

In spite of the perceived low heating values of biodegradable waste, the increasing volumes of MSW as well as the generally high percentage of the organic component observed in Ghana’s MSW means that the amount of energy that can be obtained from the waste is not insignificant.

2.2. Case Study of Bremerhaven Waste Incineration Plant

An analysis of the waste incineration plant, BEG, in Bremerhaven, Germany is used as a case study for the proposed waste-to-energy plants for Ghana. This wasteto-energy facility was constructed in 1977 with three incineration units. Construction of a fourth unit began in 2002 and was to be completed in 2009. This fourth unit is specially designed to run on pure oxygen, as a way of reducing nitrogen oxides. The throughput of waste incinerated in this plant is 1000 tons/day.

A schematic of the various stages of the waste incineration process is given in Figures 1 and 2.

2.3. Flow Sheet

Figure 3 shows a flow sheet of the waste incineration process using organic waste as the main fuel. It must be borne in mind that even with organic waste combustion the scheme has all the features and elements of a massburn incineration plant. The organic waste material in Ghana still contains traces of substances that can release harmful emissions. For example, food waste is a significant source of hydrogen chloride gas since it contains chlorides from salts. However, the flue gas cleaning technology needed here is the basic technology and not the advanced technology. The metals in the ash can be recovered after incineration.

Conflicts of Interest

The authors declare no conflicts of interest.


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