Production and characterization of smokeless bio-coal briquettes incorporating plastic waste materials

Accepted Manuscript Production and characterisation of smokeless bio-coal briquettes incorporating plastic waste materials F.I. Nwabue, U. Unah, E.J. Itumoh

PII: DOI: Reference:

S2352-1864(16)30072-4 http://dx.doi.org/10.1016/j.eti.2017.02.008 ETI 129

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Environmental Technology & Innovation

Received date : 15 September 2016 Revised date : 29 December 2016 Accepted date : 26 February 2017 Please cite this article as: Nwabue, F.I., Unah, U., Itumoh, E.J., Production and characterisation of smokeless bio-coal briquettes incorporating plastic waste materials. Environmental Technology & Innovation (2017), http://dx.doi.org/10.1016/j.eti.2017.02.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Production and Characterisation of Smokeless Bio-coal Briquettes Incorporating Plastic Waste Materials

F. I. Nwabue*, U. Unah and E. J. Itumoh Department of Industrial Chemistry, Ebonyi State University Abakaliki, Nigeria *e-mail: [email protected]

Abstract Sub-bituminous coal from Okaba mine in Kogi State, Nigeria and locally available plastic and bio-waste materials (used sachet water bags, polythene bags, saw dust and maize husk) were partially carbonized, pulverized and used in varying proportions with limestone dust, cassava flour and laterite as binders for the production of solid fuel briquettes. The briquettes were characterized by testing for porosity index, briquette density, compressive strength, ignition and heating efficiency, volatile matter, calorific value, moisture and ash contents using ASTM and DIN standards. The gross calorific values of the briquettes were determined and their fuel properties of burning rate, power output and specific fuel consumption were as well measured. The briquette ash was analysed by X-ray florescence spectrometry (XRF). However, all the briquette ash samples were found to remain intact as a block without collapse after burning. Results of the briquette characterization showed that the briquettes produced with the compositions: 20-70% coal, 2-8% limestone, 10% plastic waste, 2.5-10% cassava flour and 10-60% biomass were of medium to high quality in terms of burning and cooking characteristics, smokelessness, environmental friendliness, binding and mechanical strength. These characteristics suggest that the briquettes produced are good alternative to fuel wood for out-door and in-door cooking and for mitigation of deforestation, desertification and environmental pollution and degradation. Recycling of the plastic wastes into refuse derived fuel by incorporation in the production of these bio-coal briquettes shows great promise and could be considered as part of waste management options especially in the developing countries. Keywords: biomass, bio-coal briquettes, plastic waste recycling 1. Introduction One of the major challenges encountered in most parts of the world today, especially in the developing countries, is the scarcity of clean and affordable fuel for domestic cooking and

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other industrial activities. In these countries, majority of the citizens cannot afford the use of kerosene, liquefied or natural gas or electricity for cooking. The situation has led to the indiscriminate felling of trees and destruction of forest resources for use as fuel wood or charcoal [1-3]. For example, in Nigeria, millions of families in the rural and sub urban areas depend mainly on firewood or charcoal for their cooking and other energy needs. This has resulted in a nation-wide deforestation with the attendant problems of desertification and other environmental degradation such as global warming and loss of vital biodiversity [4, 5]. Another aspect of environmental degradation is the indiscriminate dumping of domestic and municipal wastes. In most developing countries, there are no strict legislations or waste management strategies put in place to mitigate the negative effects of indiscriminate waste disposal. Polythene materials are commonly used as bags and for housing 500mL of drinking water sold commercially in sachets which, after use, are discarded carelessly along the streets thus destroying the beauty of the environment as well as causing seasonal flooding due to blockage of drainages and water ways. Other wastes that are also generated in large quantity and constitute environmental nuisance include sawdust from timber shades and wood processing shops and some agricultural wastes such as groundnut shell and maize husks. These are either burnt or disposed of in a manner that could pollute the environment [6, 7]. These past decades have witnessed a considerable increase in research interest in the preparation of waste derived fuels for domestic and industrial uses. Production of solid fuel such as smokeless bio-briquettes from wastes that are readily available is one of the ways to address the negative environmental consequences associated with high use of fuel wood, waste generation and waste management [8-11]. These problems are of great concern especially in the developing countries [1, 3, 12-14]. Composite sawdust briquette is a good source of renewable energy for domestic cooking [1], and mixing of biomass and coal in the production of briquettes will give products with better quality such as good combustion properties compared to the use of the raw coal or sawdust alone [4, 10, 12]. In spite of improvements in the burning characteristics of briquettes, there are still environmental problems associated with briquette ash and initial smoke emission during usage [10-14]. In our search for methods of production of environmentally friendly solid fuel alternatives to fuel wood, we have found it promising to incorporate plastic wastes and bio-waste materials with carbonized coal in the production of smokeless bio-coal briquettes with good ignition properties, heating efficiency and mechanical strength.

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This paper reports our findings in the use of carbonized sub-bituminous coal, sawdust, maize husk and polythene wastes for the production and characterization of smokeless biocoal briquettes with good fuel properties, burning characteristics, environmental friendliness and fairly high heat content and mechanical strength.

2. Materials and Methods 2.1. Apparatus/Characterization tests The ash content, volatile matter, fixed carbon and optimal moisture content of the coal, biomass and briquette samples were determined according to ASTM D – 3172 – 89 specifications [15]. The calorific value was determined using Adiabatic OSK 100A Bomb Calorimeter (Hel India, Mumbai) at the International Institute for Tropical Agriculture Ibadan, Nigeria following standard procedure [16]. Total sulphur and nitrogen contents were determined according to ASTM D – 3177 – 89 specifications [17] at the National Centre for Energy Research and Development, University of Nigeria, Nsukka, while the compressive strength of the briquettes was tested using Universal Testing Machine (Jems Machines and Systems Maharashtra, India) at the Standard Organisation of Nigeria Laboratory Enugu, following ASTM D – 1037 – 93 specifications [18]. Analysis of the briquette ash for toxic metal levels was done using X-ray florescence spectrometer (XRF) (VEECO 5100L, NY USA) at the Centre for Energy Development Studies Zaria, Nigeria following standard procedure [19]. Briquette density was determined according to DIN 52182 and 51731 specifications described elsewhere [20] while the porosity index measurement for briquette quality and hardness was carried out following standard procedures [20,21]. 2.2. Briquetting materials Plastic waste materials (used water sachet and plastic bags) and bio-waste maize husks were collected randomly from different refuse dump sites and drainage blockages in Abakaliki metropolis, Nigeria, while sawdust, mainly from wood was collected from timber processing market in Abakaliki all at no cost. Low grade cassava flour was purchased from Abakpa Main Market, Abakaliki, while calcium carbonate (limestone) dust was obtained from Umuoghara Ezza granite stone quarrying site near Abakaliki metropolis, Ebonyi State, Nigeria. Carbonized sub-bituminous Okaba-Nigeria coal sample was purchased from Energymix Nigeria Limited. 2.3. Preparation of bio-waste materials The biomass (sawdust and maize husk) was sun-dried for three to four days to reduce the moisture content of the materials. The dried samples were cut into pieces with scissors,

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weighed and mixed as composite sample in the ratio 5:1 (saw dust : maize husk). The sample (20 kg) was packed in a pyrolysis stove and heated to about 300 0C to 5000C for about an hour. The partially carbonized materials were quenched with water and emptied on a clean concrete surface and allowed to cool and dry for about two hours. The dry char was pulverized using a mechanical grinder and sieved to 5 mm mesh size and then stored in sealed polyethylene bag for later usage. 2.4. Preparation of plastic waste material The plastic waste materials (used sachets water and polythene bags) were separately collected, cut into pieces using scissors and dried in the sun for three days to reduce the surface moisture. The dried samples were weighed, mixed in equal ratio (used water sachet : polythene bags) and packed in a pyrolysis stove and heated to between 200 - 2500C for about 40 minutes to reduce the volatiles. The partially carbonized materials were quenched by splashing with water and then emptied on a clean concrete surface and allowed to cool and dry for about three hours. The char was pulverized using mechanical grinder, sieved to 5 mm mesh size and stored in sealed polyethylene bags to be used later. 2.5. Preparation of coal sample The lumps of carbonized sub-bituminous Okaba coal samples were broken into smaller sizes using a hammer and were sun-dried for five days to reduce its moisture content. They were then pulverized using a locally fabricated hammer mill supplied by Energymix Nigeria Limited, sieved to 5 mm mesh size and stored in polyethylene bag for later usage. 2.6. Preparation of bio-coal briquette The briquettes were produced using a locally fabricated briquetting machine which operates on a 10 ton hydraulic jack that presses a compartment of three square moulds holding the sample mixture feed (Figure A1). The briquette compacting pressure was however not recorded but certainly should be far less than the applied 10 ton. The pulverized samples of biomass, polyethylene wastes, carbonized coal, cassava flour, limestone/laterite and water were mixed thoroughly in varying proportions to a semi paste consistency and fed into the moulds, locked and pressed using the hydraulic jack to produce the briquettes. The briquettes were either sun dried for about 3 days or dried in an oven at 110 0C for 2 hours. The dried bio-coal briquettes (Figure B2) were weighed and kept in a dry place for use in characterization tests.

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2.7. Determination of ignition time, water boiling test and other fuel properties Each of the briquette samples was ignited at the base using a lighter in a domestic briquette stove in the dark. The time required for the flame to ignite the briquette was recorded as the ignition time. The briquette is confirmed to be ignited by looking through the top ventilation holes of the briquettes (Figure B2) and seeing the red amber of the briquette. This is easily detected in the dark. Water boiling test was carried out measuring the time taken for a given mass (0.7 kg) of the briquette sample to first boil 1 kg of water under similar conditions. Specific fuel consumption, burning rate and power output of the briquette samples were determined by boiling 400 mL of water in a small stainless kettle using 0.7 kg of briquette noting the time and quenching the remaining briquette with water as soon as the water boiled. The quenched briquette was allowed to dry and weighed. Specific fuel consumption (SFC), power output and burning rate of the briquette samples were calculated using equations 1 – 3 below [13]. Burning characteristics of the briquette samples were also observed.

Where Mw = Mass of water (kg) boiled by the briquette sample; Mf = mass of briquette sample (kg) consumed to boil Mw of water; Ef = calorific value of the burnt briquette sample (kcal/kg); t = time taken to boil Mw of water by Mf of the briquette sample.

3. Results and Discussion 3.1. Briquette composition and proximate analysis Table A1 shows the composition of the formulated briquette samples while Table B2 shows the results of proximate analysis of the coke, biomass mixture and the briquette samples. Our previous work [22] showed that 10% was the limit of incorporation of plastic wastes in the preparation of the briquettes with good ignition and burning characteristics while briquettes of good quality were obtained using 10-20% binder composition. The

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studied briquette compositions as shown in Table A1 were therefore varied linearly for coke and carbonized biomass while the composition of the plastic waste was kept constant at 10%. The starch, limestone and laterite binders were varied randomly while maintaining their total composition to a maximum of 10 or 20%. From Table B2, the ash content of the briquette samples increases with increase in the percentage of coke and the inorganic binders (limestone and laterite) used for the briquette sample preparation and this gave rise to the moderately high percentage ash values for the briquettes. However, the use of the inorganic binders compensates for this drawback in that they help to trap the volatiles in the briquette samples giving rise to efficient and smokeless combustion. The results of the proximate analysis compare well with those obtained by Tahir et al [23]. 3.2. Fuel properties of samples Figure C3 shows the time it takes to ignite the briquette sample and sustain burning (ignition time) which increases with increase in the quantity of coke present in the sample. The briquette sample without coke but with 80% biomass, S00, ignites fastest in 53 seconds, compared to the other briquette samples. The sample without biomass, S 90 with the highest percentage of coke (90%) ignites in 156 seconds. This is probably because of higher volatile matter present in biomass as shown in Table B2. Generally, the short time (less than 2 minutes) of ignition observed for most of the briquettes is as a result of added biomass and plastic waste materials. The observed ignition time of less than 3 minutes for sample S80 and S90, composed of coke and plastic waste but no biomass, is considered short given that briquettes produced from coke take longer time to ignite [10]. As seen in Figure D4 and Table C3, the time required for the briquette sample to boil 1 kg of water decreases with an increase in the quantity of coke present in the briquette samples. The briquette sample with 90% coke, S90 boils the same 1 kg of water in 5 minutes 20 seconds unlike briquette sample S00, with 0% coke that boiled it in 12 minutes 1 second. This is expected as the briquette sample, S90 have higher calorific value of 5,124.08 kcal/kg than briquette sample, S00 with calorific value of 3,315.74 kcal/kg as shown in Table B2. Figure E5 shows the specific fuel consumption, measured as a ratio of mass of fuel consumed in cooking to mass of the food cooked, decreases with increase in biomass concentration. Briquettes with higher specific fuel consumption are more economical as smaller amount of it is required to cook a given quantity of food. The burning rate of the briquettes as shown in Figure F6 decreases with increase in the quantity of coke present in the briquette but increases with corresponding increase in

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biomass. This is due to the fact that biomass increases the porosity of the briquette and has higher volatile matter content as shown in Table B2, which makes the briquette to burn faster. Table F6 shows Pearson’s correlation coefficient (r, ranging from -1.0 to 1.0 inclusive) used to show the extent of linear relationship and degree of association among the fuel properties and parameters of proximate analysis of the briquette samples. The results show that the fuel properties are highly correlated among themselves. 3.3. Nitrogen and sulphur content Figure G7 shows the results of percentage nitrogen and sulphur in the briquette samples and indicate a decrease of both elements with decrease in the quantity of biomass present in the briquette. Table E5 shows that biomass has a higher percentage of nitrogen (0.43%) and sulphur (0.21%) compared to that of coke (0.05% N and 0.1% S). Therefore, the increase in the percentage of nitrogen and sulphur present in the briquette samples may be attributed to be from biomass and plastic waste materials which have 0.14% nitrogen and 0.68% of sulphur respectively. The low content of N and S in the briquettes especially S 80 and S90 showed that when burnt the briquettes will release little nitrogen and sulphur oxides to the environment. 3.4. Compressive strength, density, porosity index and shelf life In this work, we were not able to carry out the mechanical durability tests on the briquettes using CEN-TS 15210-2:2011 method [24]. We therefore adopted the ASTM S D1037-93 (1995) method [18] of evaluation of compressive strength of wood based fibre and particle board materials to the estimation of the compressive strength of our briquettes, and the results are shown in Figure H8. The results are to be regarded as approximation which gives a little insight into the briquettes’ resistance towards shock and abrasion during handling and transportation [24]. The compressive strength decreases with an increase in the quantity of coke present in the briquette samples but increases with increase in the quantity of biomass. The briquette sample, S90 with 90% coke has the least compressive strength (0.96 N/mm3), while briquette sample, S00 with 0% coke has the highest compressive strength of 4.61 N/mm3 as shown in Table E5. This is probably due to the nature of biomass with the presence of cellulose which helps to bind the briquette together and probably reduce the brittleness of the briquette [12]. Briquettes with higher compressive strength are safer to store and transport as they will not break or wear off very easily. Briquette density is known [20] to influence the burning rate of the briquettes. Table C3 shows that briquettes with higher density (S60–S90) have lower burning rates which implies that lower amount of the briquettes will be consumed per min and will therefore last longer

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on usage. The density also influenced the specific fuel consumption and power output of the briquettes which show increase with the briquette density. Briquettes with density values ˃ 1 and ˂ 1.4 are recommended as standard on the bases of high durability and quality [20]. Briquettes S50 – S80 are therefore recommended as being of fairly good quality. The porosity index of a briquette gives a measure of the briquette’s resistance against disintegration or breakage and absorption of water during transportation and storage. Hence, it gives an indication of the briquette’s quality and durability [10, 20]. The higher the porosity index, the higher the chance of absorbing water and ease of disintegration during handling. Table 3 shows that porosity index decreased with increase in the percentage of coke in the briquette-mix. This implies that briquette-mix with higher percentage of coke (S60–S80) will be of better quality and durability on usage. However, the values of the porosity index of the briquettes S10–S90 showed that they could be regarded as being of fairly high quality. The highest porosity index of 2.13 observed for briquette sample S00 (almost twice that of S10) was expected because of the cellulosic content of biomass used (bio-waste maize husks, starch and sawdust). Cellulose is water-soluble, a factor which could affect the water adsorption capability of briquettes made with only biomass-mix and subsequently their ease of disintegration in water. Porosity index also has an influence on the burning rate of the briquettes. Briquettes S00–S50 with higher porosity index also showed high burning rate. This is possibly because their more porous nature allows for inflow of air and outflow of combustion products through the briquettes while burning [12]. The shelf life of the briquettes was monitored by storage. The briquette density and moisture content stabilized within 30 days of storage. It was also observed that the briquettes have stayed for more than 2 years without fungal attack or disintegration. This is possibly due to the carbonized biomass-mix used in the briquette preparation. Carbonization of the biomass could have reduced the amount of possible nutrients available for microbial activities to take place. 3.5. Volatile matter Figure I9 and Table B2 show that the volatile matter decreases as the quantity of biomass present in the briquette decreases. Therefore, the sample containing higher quantity of biomass will ignite faster compared to the one with higher percentage of coke because of higher percentage of volatile matter in biomass. The results of the burning characteristics (Table E5) showed that the briquettes produced burn with little or no smoke contrary to works by other researchers [10-14, 25, 26] who did not report the burning characteristics of their produced briquettes. In our previous work [22], analysis of toxic metal levels of the

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briquette smoke emissions showed that Al, Cr, Ni, Fe, Mn, Cu, Zn, Co, Cd and Pb were below detectable limits using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). In this work, CO/CO2 ratio was not determined. 3.6. Ash and moisture contents Figure J10 shows that the ash content decreases with decrease in the quantity of coke and inorganic binders present in the briquette samples. Coke contains higher percentage of ash, 23.50% compared to 19.97% of biomass (Table B2). Also, limestone dust and laterite contain more mineral (non-combustible) matter which will also contribute to increase in the percentage of ash present in the briquette samples. Generally, high ash content lowers the briquette quality [10]. The results of analysis of metals and some other elements present in the ash of two of the briquette samples S00 and S20 are shown in Table D4. Compared with the World of Coal Ash (WOCA) standards [27] for the metal oxides in the ash, the results showed that some of the metal oxides were slightly above, while some were below the permissible limits. The results indicate that the briquettes are environmentally friendly. Our previous work [22] on the briquette ash showed that it has good potential for use as an abrasive washing powder, additive for soil and white-wash paint. The use of binders affected the quality of the briquettes produced because of their ability to hold firmly the briquette-mix particles. Even though the inorganic binders of laterite and limestone contributed to high percentage of the ash content of the spent briquettes as shown in Table B2, we observed that the binders performed two important functions first; they held the briquette and its ash together and thus prevented disintegration during and after usage. This reduced to the barest minimum the occurrence of fly ash. Secondly, they provided surface area for adsorption and eventual combustion of obnoxious gases and retention of particulate matter during briquette usage thus improving on the smokeless nature of the briquettes [11]. Figure M13 shows the results of optimal moisture content, determined when the briquettes had stabilized, which increases as the quantity of biomass present in the briquette increases. Low moisture content has been noted [4, 7, 28] to improve briquetting process and quality. As shown in Table B2, biomass has higher moisture content of 10.62% than coke with 5.00%. The briquettes S50 – S80 with low percentage of moisture content are of desirable quality than the others with lower percentage of moisture content.

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3.7. Calorific value The presence of biomass in the briquette-mix reduced the gross calorific values to moderate or medium ranking. Table B2 shows that the gross calorific values of the briquettes are influenced by their moisture contents in an inverse relationship. Therefore the preferred briquettes are those of the mix S50–S80 with relatively low moisture content. Figure N14 shows that the calorific value increases with an increase in the quantity of coke present in the briquette samples. The power output as shown in Figure L12 and Table C3 increases as the percentage of coke present in the briquettes also increases. Briquette sample S90 has a power output of 394.16 watts/kg and calorific value of 5,124.08 kcal/kg. This means it will cook the same quantity of food faster than the other briquettes. Coke has the highest calorific value of 5,700 kcal/kg compared to 3,008.16 kcal/kg and 4,418.65 kcal/kg for plastic waste and biomass respectively. High calorific value entails high heat output which will help to cook food faster. 4. Conclusion Production of bio-coal briquette incorporating carbonized plastic waste materials has been found to be successful. The briquette produced were found to be of good quality as they ignite easily, burn efficiently and generate less ash. The briquettes were also good in terms of moderately high gross calorific value. The density and porosity index of some of the briquettes were also found to be favourable to ensure durability and safety of handling, transportation and storage without breakage. For domestic cooking, the briquette samples S10, S20 and S60-S80 were shown to be most efficient in terms of ignitability, ash content, density, porosity index, calorific value and no smoke emission. References 1. Olawole, A. K. and Adegoke, C. O. (2008). Comparative Performance of Composite Sawdust Briquette with Kerosene Fuel under Domestic Cooking Condition. Australian Journal of Technology 12(1): 57-61. 2. Aina, O. M., Adetogun, A. C., and Iyiola, K. A. (2009). Heat Energy from Valueadded Sawdust Briquettes of Albizia Zygi. Ethiopian Journal of Environmental Studies and Management, 2(1): 42-49. 3. Oladeji, J. T. (2010). Fuel Characterization of Briquettes Produced from Corncob and Rice Husk Residues, The Pacific Journal of Science and Technology. 11(1): 101-106. 4. Pierrick, J. and Rolf – peter, O., (2004). Bio Coal out of Firebreak and Agricultural Residue: Between Forest Protection Management and Local Household Fuel Supply. Senegalese Forest Management, 2: 78-86.

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5. Omaka, O. N., Nwabue, F. I., Itumoh, E. J. and Okeke, G. N. (2013). Gas Emissions and Metallic Contents of Commonly used Fuelwood in Nigeria. Environment and Pollution 2(3): 100-106. 6. Demirbas, A. (1999), Physical Properties of Briquettes from Waste Paper and Wheat Straw Mixtures. Energy Conversions Management 40: 437-445. 7. Jaan, K., Priit, K., Aare, A., Viktor, L., Peter, K., Lubomir, S. and Ulo, K. (2010), Determination of Physical, Mechanical and Burning Characteristics of Polymeric Waste Material Briquettes. Estonian Journal of Engineering 16(4): 307-316. 8. Islam, R. F., Islam, R. M., and Beg, R. A. (2008), Renewable Energy Resources and Technologies Practice in Bangladesh. Renewable and Sustainable Energy Reviews, 12: 299-343. 9. Vongsaysana S. and Achara U. (2009), Comparison of the Physical and Chemical Properties of Briquette and Wood Charcoal in Khammouane Province, Lao PDR. Environmental and Natural Resources Journal 7(1): 12-24. 10. Onuegbu, T. U., Ekpunobi, U. E., Ogbu, I. M., Ekeoma, M. O., and Obumselu, F. O. (2011). Comparative Studies of Ignition Time and Water Boiling Test of Coal and Biomass Briquettes blend, International Journal of Research and Review in Applied Science, 7(2): 153-159. 11. Emerhi, E. A., (2011), Physical and Combustion Properties of Briquettes Produced from Sawdust of three Hardwood Species and Different Organic Binders. Advances in Applied Science Research 2(6): 236-246. 12. Onuegbu, T. U., Ogbu, I. K., Ilochi, N. O., Ekpunobi, U. E., and Ogbuagu, A. S. (2010). Enhancing the Properties of Coal Briquette using Spear Grass (Imperata Cylindrica). Leonardo Journal of Sciences 17: 47-58. 13. Olawole, A. K. (2009). Performance of Composite Sawdust Briquette Fuel in a Biomass Stove under simulated condition. Australian Journal of Technology 4: 284288. 14. Oladeji, J. T. (2011). Comparative Fuel Characterization of Briquettes Produced from two Species of Corncob. (On-line: http://www.sciencepub.net/researcher) 3(4): 1-4. Accessed; September 4, 2014. 15. American Society for Testing and Materials Standard (ASTM S), D3177-89 (2002). Standard Test Methods for Sulphur and Nitrogen in the Analysis Sample of Coal and Coke.

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16. Sumner, H. R., Sumner, P. E., Harmnond, V. C., and Monroe, G. E. (1983). Indirectfired Biomass Furnace Test and Bomb Calorimeter Determinations. Trans. ASAE 28: 238-241. 17. American Society for Testing and Materials Standard (ASTM S), D3172-89 (2002). Standard Practice for Proximate Analysis of Coal and Coke. ASTM International: West Conshocken. 18. American Society for Testing and Materials Standard (ASTM S), D1037-93 (1995). Standard Methods of Evaluating the Properties of Wood Based Fibre and Particle Board Materials: ASTM, Philadelphia. 19. Jenkins, R., (1999). X-ray Fluorescence Spectrometry, 2nd ed., John Wiley & Sons, Inc. p. 207. 20. Krizan, P., Soos, L. and Vukelic, D. (2009). A Study of Impact Technological Parameters on the Briquetting Process. Facta Universitatis ser.: Working Living Environ. Prot. 6: 39-47. 21. Piersol, R. J. (1948). Briquetting Illinois Coal without Binder. State Geological Survey Bulletin 72: 34-35. 22. Unah, U. (2014). Production and Characterization of Smokeless Bio Coal Briquettes Incorporating Plastic Waste Materials. Unpublished MSc Dissertation, Department of Industrial Chemistry, Ebonyi State University Abakaliki Nigeria. 23. Tahir, D., Gareso, P. L., Suariamiharja, D. A., Subar, S., Inzana, N. and Palentek, N. (2012). Physical Properties of Briquettes based on Charcoal from Groundnut Shell, Cassava Peel and Durian Shell. Proceeding of International Conference on Sustainable Energy Engineering and Application (6-8 Nov. 2012), Yogyakarta, Indonesia. 24. Institute for Standardization of Serbia, SRPS EN 15210-2 (2011), Solid biofuels – Determination of mechanical durability of pellets and briquettes – Part 2: Briquettes. 25. Chaiklangmuang, S., Supa, S and Kaewpet, P. (2008). Development of Fuel Briquettes from Biomass-Lignite Blends. Chiang Mai J. Sci. 35(1): 43-50. 26. Davis, R. M. and Abolude, D. S. (2013). Mechanical Handling Characteristics of Briquettes Produced from Water Hyacinth and Plantain Peel as Binders. J. Scientific Research and Reports 2(1): 93-103. 27. World of Coal Ash (WOCA) Conference in Nasvhille, TN-May 5-7, 2015, (On-line: http://www.worldofcoalash.org/). Accessed; December 29, 2015.

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28. Krizan, P. (2009). Wood Waste Compacting Process and Conception of Presses Construction, Unpublished Thesis, Department of Material Science, Slovak University of Technology, Bratislava, 2009, pp. 34 - 46.

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Figure A1. Locally fabricated briquetting machine

Figure B2. Dried bio-coal briquettes

15 Table A.1, Percentage composition of the briquette samples Constituents (%) Coke Carbonized Biomass Carbonized Plastic waste Binder Starch Binder Limestone Binder Laterite

S00 80 10 5 5

S10 10 60 10 10 5 5

S20 20 60 10 5 2.5 2.5

S30 30 50 10 3 3.5 3.5

S40 40 40 10 4 3 3

S50 50 30 10 5 2.5 2.5

S60 60 20 10 2.5 7.5 -

S70 70 10 10 7 1.5 1.5

S80 80 10 1 8 1

S90 90 5 5

Key:

S00 = Briquette with 0 per cent coke S10 = Briquette with 10 per cent coke S20 = Briquette with 20 per cent coke S30 = Briquette with 30 per cent coke S40 = Briquette with 40 per cent coke S50 = Briquette with 50 per cent coke S60 = Briquette with 60 per cent coke S70 = Briquette with 70 per cent coke S80 = Briquette with 80 per cent coke S90 = Briquette with 90 per cent coke Table B.2, Proximate analysis of coke, biomass mixture, briquette samples and their burning characteristics Gross Calorific Burning characteristics Ash Moisture Volatile Fixed Value on dry basis Parameter (%) Content Content Matter Carbon (kcal/kg)

S00

27.93 ± 0.21

8.47 ± 1.12

31.74 ± 0.11

31.86 ± 0.33

3315.74

Low smoke on ignition and disappears after 2 minutes

S10 S20 S30 S40 S50 S60 S70 S80 S90 Coke Biomass-mix (carbonized)

30.34 ± 0.44 32.03 ± 0.36 33.91 ± 0.11 34.55 ± 0.38 35.21 ± 0.19 35.10 ± 0.17 35.75 ± 0.27 36.33 ± 0.23 36.38 ± 0.40 23.50 ± 0.31 19.97 ± 0.14

7.10 ± 0.32 5.88 ± 0.18 5.06 ± 0.03 4.89 ± 0.05 4.05 ± 0.17 4.39 ± 0.24 3.23 ± 0.02 3. 43 ± 0.84 3.98 ± 0.32 5.00 ± 0.52 10.62 ± 0.16

27.77 ± 0.64 25.69 ± 0.72 24.05 ± 1.22 23.55 ± 1.13 22.85 ± 0.07 22.37 ± 1.22 22.01 ± 0.09 19.58 ± 0.37 17.23 ± 1.02 15.00 ± 0.41 32.11 ± 0.93

34.79 ± 0.52 36.40 ± 2.13 36.98 ± 0.49 37.01 ± 0.32 37.89 ± 0.12 38.14 ± 1.61 39.01 ± 1.02 40.66 ± 1.66 42.41 ± 0.61 54.36 ± 4.81 34.30 ± 0.80

3522.01 4092.01 4208.07 4361.81 4430.04 4604.55 4492.36 4860.82 5124.08 5700.00 4418.65

Smokeless Smokeless Smokeless Smokeless Smokeless Smokeless Smokeless Smokeless Smokeless -

Table C.3, Fuel properties of briquette samples Sample

S00 S10 S20 S30 S40 S50 S60 S70 S80 S90

Water Boiling Time (min/kg) 12.06 ± 0.31 8.53 ± 0.25 8.20 ± 0.20 8.01 ± 0.93 7.83 ± 0.32 7.20 ± 0.86 7.03 ± 1.06 6.09 ± 2.04 6.43 ± 0.40 5.20 ± 1.03

Ignition Time (sec.) 53 61 70 82 91 101 105 122 144 156

Burning Rate (kg/min) 3.77 ± 0.22 3.28 ± 0.19 2.86 ± 0.26 2.44 ± 0.22 2.19 ± 0.09 1.98 ± 0.31 1.90 ± 0.14 1.68 ± 0.52 1.39 ± 0.27 1.28 ± 0.61

Specific Fuel Consumption

Power Output (watts/kg)

0.20 ± 0.14 0.25 ± 0.08 0.27 ± 0.16 0.31 ± 0.12 0.38 ± 0.22 0.40 ± 0.09 0.46 ± 0.31 0.48 ± 0.11 0.50 ± 0.29 0.52 ± 0.42

109.97 ± 6.81 165.16 ± 7.71 199.61 ± 4.32 210.14 ± 5.11 222.83 ± 3.07 246.11 ± 4.05 261.99 ± 7.04 295.06 ± 4.55 302.38 ± 9.80 394.16 ± 6.11

Compressive strength (N/mm3) 4.61 4.37 3.91 3.32 3.58 2.92 2.63 2.20 1.03 0.96

P In

2 1 1 1 1 1 0 0 0 0

17

Table D.4, Results of the oxides of metals and elemental analysis (mg/kg) of the briquette ash Composition Al2O3 SiO2 SO3 Cl K 2O CaO TiO2 V 2O 5

Cr2O3 MnO Fe2O3 NiO CuO ZnO Br RbO2 SrO ZrO2 Ag2O In2O3 Eu2O3 Re2O7 PbO Ga2O3 Yb2O3

S00 20.000 43.000 3.500 NA 4.180 10.700 2.830 0.120 0.032 0.081 12.200 0.012 0.031 0.055 0.004 0.033 0.170 0.330 1.600 0.910 0.068 0.030 0.083 NA 0.005

S20 20.000 43.900 3.100 0.020 4.230 11.200 2.760 0.120 0.033 0.075 11.310 0.013 0.028 0.059 0.003 0.038 0.210 0.330 0.930 1.000 0.079 0.030 0.084 0.010 NA

WOCA 25.80 52.00 3.300 NA NA 8.70 NA NA NA NA 6.90 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

NA = not available WOCA = 2015 World of Coal Ash Table E.5, Percentage of nitrogen and sulphur of the briquette samples, coke, biomass and plastic waste Sample S00 S10 S20 S30 S40 S50 S60 S70 S80 S90 Biomass Coke Plastic Waste

Nitrogen Content (%) 0.36 0.28 0.28 0.25 0.23 0.22 0.13 0.11 0.07 0.06 0.43 0.05 0.14

Sulphur Content (%) 0.20 0.24 0.19 0.17 0.15 0.14 0.12 0.10 0.08 0.07 0.21 0.01 0.68

18 Table F.6, Pearson’s correlation coefficients for fuel properties and proximate analysis of the briquette samples WBT 1.00

WBT IT BR SFC PO GCV MC VM AC FC

IT -0.86 1.00

BR 0.93 -0.95 1.00

Key: WBT = Water Boiling Time IT = Ignition Time BR = Burning Rate SFC = Specific Fuel Consumption PO = Power Output GCV = Gross Calorific Value MC = Moisture Content VM = Volatile Matter AC = Ash Content FC = Fixed Carbon

SFC -0.89 0.96 -0.98 1.00

PO -0.93 0.97 -0.94 0.94 1.00

GCV -0.90 0.94 -0.98 0.94 0.95 1.00

MC 0.91 -0.85 0.96 -0.92 -0.85 -0.91 1.00

VM 0.95 -0.95 0.98 -0.94 -0.97 -0.98 0.91 1.00

AC -0.93 0.88 -0.98 0.93 0.89 0.96 -0.98 -0.96 1.00

FC -0.95 0.96 -0.96 0.93 0.98 0.97 -0.90 -0.99 0.93 1.00

19

180 160

Ignition Time (sec)

140 120 100 80

60 40 20 0 S00

S10

S20

S30

S40

S50

S60

S70

S80

S90

Briquette Samples Figure C.3, Results of ignition time

Water Boiling Time (min/kg)

14 12

10 8 6 4 2

0 S00

S10

S20

S30

S40

S50

S60

Briquette Samples

Figure D.4, Results of water boiling time

S70

S80

S90

20

Specific Fuel Consumption

0.6 0.5

0.4 0.3 0.2 0.1

0 S00

S10

S20

S30

S40

S50

S60

S70

S80

Briquette Samples Figure E. 5, Results of specific fuel consumption

4

Burning Rate (kg/min)

3.5 3 2.5 2

1.5 1 0.5

0 S00

S10

S20

S30

S40

S50

S60

Briquette Samples Figure F.6, Results of burning rate

S70

S80

S90

S90

21

0.4

% Nitrogen and Sulphur

0.35 0.3 0.25 0.2

% Nitrogen

0.15

% Sulphur

0.1 0.05

0 S00 S10 S20 S30 S40 S50 S60 S70 S80 S90 Briquette Samples

Figure G. 7, Results of nitrogen and sulphur content

Compressive Strength (N/mm3)

5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 S00

S10

S20

S30

S40

S50

S60

S70

Briquette Samples

Figure H. 8, Results of compressive strength

S80

S90

22

35

% Volatile Matter

30

25 20 15 10 5

0 S00

S10

S20

S30

S40

S50

S60

S70

S80

S90

Briquette Samples

Figure I.9, Results of volatile matter

40 35

% Ash Content

30 25 20

15 10 5

0 S00

S10

S20

S30

S40

S50

S60

S70

Briquette Samples

Figure J.10, Results of the ash content

S80

S90

23

45 40

% Fixed Carbon

35

30 25 20 15 10 5

0 S00

S10

S20

S30

S40

S50

S60

S70

S80

S90

Briquette Samples

Figure K.11, Results of fixed carbon

450 Power Output (watts/kg)

400 350 300 250 200 150 100 50 0 S00

S10

S20

S30

S40

S50

S60

S70

S80

Briquette Samples

Figure L.12, Results of power output

S90

24

9

% Moisture Content

8 7 6 5 4 3 2 1 0 S00

S10

S20

S30

S40

S50

S60

S70

S80

S90

Briquette Samples

Figure M.13, Results of moisture content

Gross Calorific Value (Kcal/kg)

6000 5000

4000 3000 2000 1000

0 S00

S10

S20

S30

S40

S50

S60

S70

S80

Briquette Samples

Figure N.14, Results of calorific value

S90

Production and Characterisation of Smokeless Bio-coal Briquettes Incorporating Plastic Waste Materials

 The article is aimed at producing bio-coal briquettes from available waste materials that litter the streets of Abakaliki metropolis in Ebonyi State of Nigeria. The waste materials include; sawdust, sachet water bags, used polythene bags and corn husk.  The briquettes were characterized by testing for porosity index, compressive strength, ignition and heating efficiency, volatile matter, calorific value, moisture and ash contents using ASTM standards.  The results of proximate analysis of the briquette samples showed the range: 27.93% 36.38% for ash content, 17.23% - 31.74% for volatile matter, 31.86% - 42.41% for fixed carbon and 3.23% - 8.47% for moisture content while coke and biomass mixture gave 23.50% and 19.97% for ash contents, 15.00% and 32.11% for volatile matter, 54.36% and 34.30% for fixed carbon and 5.00% and 10.62% for moisture content respectively.  The determined gross calorific values of the briquettes which are in the range of 3315.74 – 5124.08 kcal/kg were lower than that of the coke (5700 kcal/kg) and the fuel properties of the briquette samples showed burning rate of 1.3 – 3.8 kg/min and power output of 109.97 – 394.16 watts/kg.  These characteristics suggest that the briquettes produced are good alternative to fuel wood for out-door and in-door cooking and for mitigation of deforestation, desertification and environmental pollution and degradation. Recycling of the plastic wastes into refuse derived fuel by incorporation in the production of these bio-coal briquettes shows great promise and could be considered as part of waste management options especially in the developing countries.