Pyrolysis of Organic Waste: A Way to Solid Waste Management and Extraction of Fuel

Abstract

Bangladesh is a developing country and is one of the most densely populated countries in the world. Her per capital energy consumption is also low compared to others. At present, the energy demands are becoming more acute day by day. Environmental issues and energy scarcity led the government of the developing countries to think about new and alternative energy resources. Renewable energy resources may be one kind of alternative energy. Various waste materials derived from agriculture or industrial sectors can contribute to these issues. Tyre wastes, mixture of organic and inorganic materials, already become potential source to derive liquid fuel as well as solid fuels by pyrolysis. Shoe/sandal soles have similar compositions like tyres and also create environmental pollution problems. Rubber containing wastes such as shoe/sandal soles are solid waste which is non-biodegradable and with increased production of shoe/sandal, the volume of waste soles will also be increased. Some typical problems are created to the environment as well as to our surroundings by the disposal of such wastes. The dumping of waste (shoe/sandal soles) in the drain is one of the main environmental issues in the municipal/city areas of Bangladesh. Blockage of drain and generation of mosquitoes or other bacteria are favored by the disposal of such wastes in unplanned manner. So, deliberately this matters to the authority and researchers to manage these nonbiodegradable waste materials (soles of shoe/sandal). So, a way to manage waste as well as extraction of fuel may be a good solution to this problem. Under the circumstances, extraction of fuel from shoe/sandal sole waste materials that manages the environment, pyrolysis is the best way. It will indirectly help to manage such non-biodegradable wastes, also low grade liquid fuels may be obtained. When waste materials were pyrolyzed, they generate oil, char and gas, which are valuable. The oil has sufficient calorific value and may be used to provide process energy and char may be used as activated carbon or carbon black. So, they may be considered as a new raw material for pyrolysis. In the present study, waste shoe/sandal soles were collected from the nearby local area of Jashore and Khulna city of Bangladesh were pyrolysed in a batch type reactor. Experiments on pyrolysis of shoe/sandal soles were conducted by varying the temperature within the range of 200-250oC at every 25oC. The batch type fixed-bed pyrolysis system was constructed and installed in the Heat Engine Laboratory of Department of Mechanical Engineering, Khulna University of Engineering & Technology. The maximum yield of pyrolytic oil and pyrolytic solid from waste shoe/sandal soles was 36.0 % (by weight) and 53.0 % (by weight) with the feed size of 0.75 × 0.50 cm and 1.25 × 1.0 cm respectively with loading size of 1.7 kg. The properties of pyrolytic oil obtained from waste soles of shoe/sandal such as density, flash point, boiling point and pour point were measured and the respective values are in the range of 0.877 – 0.934 g/cm3, 96 - 108oC, 153 – 158oC and -11 to -12.5oC respectively and the gross calorific value (GCV) is around 35 - 38 MJ/kg. The gross calorific value (GCV) of pyrolytic solid is around 11 - 16 MJ/kg which is comparable to same of peat (12 to 16 MJ/kg) and lignite coal (13 to 16 MJ/kg). The concentrations of elemental compositions of pyrolytic liquid obtained from shoe/sandal sole pyrolysis were found to be almost 71.7% for carbon, 10.9% for hydrogen, 1.12% for nitrogen, 0.50% for sulphur and 15.78% for others at 200oC. The derived oil from pyrolysis of waste shoe/sandal soles were investigated for FTIR four groups: alkane, alkenes, alkynes and aromatic compounds. The results showed more aromatic hydrocarbons. The TGA analysis of the same shows that the experimental curve is higher from 200 to 400ºC, when the rate of weight loss of shoe/sandal sole pyrolysis is higher. The oil obtained from pyrolysis of shoe/sandal sole wastes can be used as alternative fuel or chemical feedstock after some treatment. The results show that these properties are similar to that of the low grade liquid fuels and thus pyrolysis of such waste soles of shoe/sandal will reduce environmental pollution to some extent as well as be an alternative source of energy.