Municipal Solid Wastes (MSW) issues have become talk of the day worldwide because of the current and the future threats it has to both life and the environment. Malaysia, like other developing nations, has been facing serious problems in recent years in terms of MSW and its management due to the nation's rapid economic growth. The objective of this paper is to review and present the current state of MSW and its management in Malaysia and to estimate the economic potentials of some recyclables as well. MSW generation in Malaysia has increased significantly in recent years, ranging between 0.5 -2.5kg per capita per day (or a total of 25000 -30000 tons per day). Generally, the waste contains high amount of organics, moisture content and bulk density. More than 70% of the generated wastes are collected using both curbside and communal centers with a collection frequency varying from daily to every two days. In addition, both compactor trucks and open lorry trucks are used. Landfilling is the main disposal method practiced; about 90 -95% of the collected wastes is still disposed in landfills, with a recycling rate of 5 -10% despite the fact that 70 -80% of the waste is recyclable. Estimation of the amount of recyclables and their revenue generation potential shows an impressive result. Recycling and composting of the municipal solid waste is therefore recommended.
Release of green house gases (GHGs) from landfills as a result of ineffective management of those landfills is a serious environmental problem especially in developing countries. The landfill gas (LFG) thus released is a potential resource that can be converted to renewable energy. LFG is made up majorly of methane and carbon dioxide and produced by anaerobic biodegradation processes of municipal solid waste in landfills. This study estimates the amount of this methane emitted from landfills and its potential economic benefits. Using the Intergovernmental Panel on Climate Change (lPCC) methodology, in 2002, methane emission of 251,000 tonnes per year was estimated for Peninsular Malaysia based on 16,988 tonnes per day of municipal solid waste generated. This can generate 1.5 billion kWh of electricity per year worth over RM 450 million (US$I41 million). In addition, this leads to carbon dioxide reduction of 5,271,000 tonnes per year equivalent to carbon credit of RM 222 million (US$69 million). Therefore, the exploration of this resource, besides the economic benefits helps in reducing the dependence on depleting fossil fuel and hence mitigating global warming.
The combination of Irish potato waste (IPW) and poultry waste (PW) can form a synergy resulting into an effective substrate for a better biogas production due to some materials they contain. In this work, optimization and kinetic study of biogas production from anaerobic digestion of IPW and PW was investigated. Response surface methodology (RSM) was applied to optimize conditions such as initial pH, solids concentrations and waste ratios. The anaerobic digestion of the two wastes was carried out in the mesophilic condition and Box-Behnken design (BBD) was used to develop and analyze a predictive model which describes the biogas yield. The results revealed that there is a good fit between the experimental and the predicted biogas yield as revealed by the coefficient of determination (R2) value of 97.93%. Optimization using quadratic RSM predicts biogas yield of 19.75% at the optimal conditions of initial pH value 7.28, solids concentration (w/v) 9.85% and waste ratio (IPW:PW) 45:55%. The reaction was observed to have followed a first order kinetics having R2 and relative squared error (RSE) values of 90.61 and 9.63% respectively. Kinetic parameters, such as rate constant and half-life of the biogas yield were evaluated at optimum conditions to be 0.0392 day-1 and 17.68 days respectively. The optimum conditions and kinetic parameters generated from this research can be used to design real bio-digesters, monitor substrate concentrations, simulate biochemical processes and predict performance of bio-digesters using IPW and PW as substrate.
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