Recovery and Characterization of Fuel from Pyrolysis of Medical Wastes: An Alternative Source of Energy

Abstract

Bangladesh is a developing country and one of the most densely populated countries in the world. Energy consumption per capita of this country is also low compared to other developing nations. At present, the energy demands are becoming acute day by day. Environmental concerns and energy insufficiency led the government of the developing countries to think about innovative and nonconventional energy sources. Renewable energy sources may be a possible solution for meeting ever increasing energy demand as well as a way out of increasing environmental pollution. Various waste materials created from different sectors such as agricultural, industrial or medical sectors may also contribute to these matters. Inorganic materials like tyre waste are already contributing as a potential source of energy by deriving liquid and solid fuels through pyrolysis.

Appropriate and safe management of medical waste is acknowledged globally. Syringe/saline bottle wastes are mainly polyethelene and polypropelene plastic which are non-biodegradable and can create environmental pollution. Various typical problems are created to our surroundings by the disposal of such medical wastes. Sustainable management of such waste is important from various considerations. Lack of proper supervision of medical waste can cause some severe problems. The dumping of medical waste (syringe/saline bottle) into the drain is one of the main environmental issues in the municipal/city areas of Bangladesh. Blockage of drain and generation of mosquitoes and other bacteria are favoured by the disposal of such wastes in unplanned manner. The unmanaged recycling of infectious syringes and saline bottles represent a big threat to public health. Such circumstances are very likely to occur when medical waste is dumped in open space. Street children are chiefly at risk to come in contact with such wastes. Besides health-risk originated from direct contact, medical waste can harmfully affect the ecosystem by polluting water-bodies during waste treatment. Also, when such wastes are discarded in open areas close to water-bodies, they may become contaminated. So, deliberately this matters to the authority and researchers to manage these nonbiodegradable waste materials. So, a way to manage waste as well as extraction of fuel may be a good solution to this problem.

Management of medical waste is the accurate constraint, storage, treatment and dumping of infectious waste produced at human and animal health-care facilities. Adequate treatment procedures of medical waste are processes or techniques specifically designed to change the biological nature and composition/structure of medical waste. If this is done effectively, the wastes will no longer be contagious or biologically hazardous. The safe discarding and treatment of medical wastes have been ignored in Bangladesh. Land filling is largely used to manage medical waste which is not an appropriate option as dumped plastic wastes can cause serious damage to environment.

It is a shocking situation that waste produced inside the health-care facilities are collected by untrained cleaners without any separation in almost every city of Bangladesh. Then the cleaners dumped them into a hole or city corporation dustbin. Waste collectors use open basket or plastic bowl. Medical wastes are discarded in some open places, whereas rest of the waste is taken at the city corporation burning area. Open burning of medical waste is causing serious air pollution. Therefore, pyrolysis process can be a promising way out of this crisis. It will indirectly help to manage such non-biodegradable wastes, also low grade liquid fuels can be obtained. When waste materials are pyrolyzed, they generate oil, char and gas, which are valuable. The oil and char has adequate calorific value and can be used to produce heat energy.

In the present research, waste syringe/saline bottle were collected from the local clinics and hospitals of Khulna city areas and were pyrolyzed in a batch type reactor. Experiments on pyrolysis of syringe/saline bottles were conducted by changing the temperature within the range of 150-250° C at an interval of 50° C. The batch type fixed-bed pyrolysis reactor was constructed and installed in the Heat Engine Laboratory of the Department of Mechanical Engineering, Khulna University of Engineering & Technology. The maximum yield of pyrolytic oil and pyrolytic char from syringe waste was 35.94% (by weight) at 250° C and 51.08% (by weight) at 150° C with the feed size of 2×2 cm with loading size of 1.5 kg. The maximum yield of pyrolytic oil and pyrolytic char from saline bottle waste was 36.14% (by weight) at 250°C and 51.15% (by weight) at 150°C with the feed size of 2×2 cm with loading size of 1.5 kg.

The properties of pyrolytic oil from waste syringe/saline bottle such as density, kinematic viscosity, pour point, boiling point and cloud point were measured and the respective values are in the range of 726 to 758kg/m3 , 3.19 to 4.75cSt, -12 to -16° C, 86 to 95° C, -2 to 5°C and the gross calorific value (GCV) is around 42-44 MJ/kg which is comparable to diesel (42 to 46 MJ/kg). The GCV of pyrolytic char is around 42-43 MJ/kg which is comparable to anthracite coal (23 to 24 MJ/kg). The Gas chromatography-mass spectrometry (GC-MS) and Fourier Transform Infra-Red (FTIR) tests suggest presence of higher amount of aromatic compounds in pyrolytic oils evolved from the pyrolysis of syringe/saline bottle waste. The Thermogravimetric Analysis (TGA) shows that the experimental curve is higher from 150 to 300°C. The oil and char obtained from pyrolysis of syringe/saline bottle waste 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 high grade solid fuels and thus pyrolysis of such waste (syringe/saline bottle) will reduce environmental contamination to a degree as well as be a substitute source of energy.