Improving the Quality of Pyrolysis Oil from Co-firing High-density Polyethylene Plastic Waste and Palm Empty Fruit Bunches

This study aimed to produce and improve the quality of pyrolysis oil as a source of bioenergy that is made by mixing palm empty fruit bunch (EFB) with high-density polyethylene (HDPE) plastic waste. The slow co-pyrolysis method was employed, and HDPE waste and EFB were fed into the pyrolysis reactor at HDPE amounts of 0, 10, 25, 50, 75, and 100% by weight. The pyrolysis oil product was obtained by co-firing EFB with HDPE using the slow co-pyrolysis method in a fixed bed reactor at 500°C with a flow rate of 750 mL/min and a heating rate of 5°C/min. The chemical compositions of pyrolysis oil were analyzed by gas chromatography-mass spectroscopy. A pyrolysis oil produced by HDPE 100 wt.% was dominated by the chemical compounds of phenols, aromatics, aliphatic, and acids, while for EFB 100 wt.% was dominated with aldehydes, acids, phenols, furan and aliphatic. The addition of HDPE reduced the amount of pyrolysis oil yield, increased the pH, reduced the viscosity, and reduced the oxygen content of the pyrolysis oil. These results proved that the HDPE affected the decrease in pyrolysis oil and the increase in gas production from co-firing HDPE and EFB using the slow co-pyrolysis method.

Bioenergy; HDPE; Improving the quality; EFB; Pyrolysis oil; Reduced the oxygen

Pyrolysis oil is an important alternative energy resource, as it has the potential to replace fossil fuels with a renewable resource to diminish greenhouse gas emissions and at the same time to increase the value of agricultural and plastic waste. Therefore, pyrolysis oil could create an additional economic value for poor communities, such as rural populations and individuals who recycle plastic waste (Sukiran et al., 2017). Pyrolysis oil can be synthesized from forestry biomass, crop residues (agricultural biomass) such as empty fruit bunches (EFB), palm kernel shell, mesocarp fiber, oil palm frond, corn cobs and oil palm trunk (Das et al., 2009; Supramono et al., 2016a; Sukiran et al., 2017). An advantage of agricultural biomass is that it contains less sulfur and is abundantly available as a feedstock.

EFB is the main agricultural waste of the palm industry, and it is an abundant waste biomass that is harvested in tropical regions such as in Indonesia and Malaysia (Purwanto et al., 2015; Ro et al., 2018). EFB quantities have been increasing in recent years due to the increasing cultivation of palm. Although EFB can be returned to the soil as fertilizer or burnt to generate steam for electricity production, most EFB is dumped in landfill because of its low economic value. Thus, a large amount of EFB is currently not utilized and can be used as a feedstock for pyrolysis oil production (Chang, 2014; Purwanto et al., 2015). The oil is obtained from the pyrolysis of EFB at approximately 500°C in a fluidized bed reactor; the calorific value usually is approximately 20 MJ/kg (Sukiran et al., 2017). A similar observation has been reported for pyrolysis of biomass with heating at temperatures of 450–550°C (Oudenhoven et al., 2016). As has been recently reported, rapid pyrolysis that involves brief contact time is a promising method (Das et al., 2009; Kim et al., 2011). The co-pyrolysis method is a more promising way to convert the waste into higher-value oil (Gang & Aimin, 2008). It can reduce the phase separation of pyrolysis oil, and thus it can improve the stability of the oil (Supramono et al., 2016b). This technique can therefore reduce the volume of waste and achieve synergy by co-processing biomass with plastics and other materials (Gang & Aimin, 2008).

Through pyrolysis, environmental pollution could be reduced and the added value of agro-waste could be increased by energy generation mainly through the conversion of agricultural biomass together with plastic (high-density polyethylene [HDPE]) waste into energy. In addition, co-pyrolysis has an advantage over pyrolysis of either agricultural waste or plastic waste separately. The co-pyrolysis product yield is higher than when adding the individual pyrolysis oil produced separately by pyrolysis of agricultural or plastic waste, because of the interaction of free radicals during the thermal treatment process (Bhattacharya et al., 2009; Supramono et al., 2016b). The chemical composition of oil from waste agricultural biomass contains significant amounts of oxygenated organic compounds, and therefore results in a high O/C ratio, high moisture causing low energy density, and a low heating-value product. This also leads to high soot formation. Furthermore, the presence of oxygenated products reduces the stability and therefore the shelf life and storage duration of the oil (Sabil et al., 2013). The consumption of plastic has increased very quickly worldwide, making plastic waste very abundant (Bhattacharya et al., 2009). Increasing plastic demand leads to increasing waste accumulation every year (Sabil et al., 2013; Sharuddin et al., 2016). A significant percentage of plastic dumped in landfills are HDPE (57%) (Sogancioglu et al., 2017). 

The direct use of pyrolysis oil from agricultural waste as a fuel is not viable because of the low heating value of pyrolysis oil. This is caused by the rich oxygen-containing compounds (Ro et al., 2018; Rodionova et al., 2017). Co-pyrolysis of EFB with plastic waste can reduce the oxygen compounds and increase the caloric value of pyrolysis oil. The addition of plastics in biomass pyrolysis increases the yield and the resulting oil calorific value compared with biomass pyrolysis alone, due to the presence of paraffin-containing hydrocarbon polymers, isoparaffin, olefin, naphtha, and aromatics (Bhattacharya et al., 2009; Abnisa et al., 2014; Uzoejinwa et al., 2018).

In this study, we produced pyrolysis oil by co-firing EFB with HDPE using a slow co-pyrolysis method at 500°C with a flow rate of 750 mL/min and a heating rate of 5°C/min using a fixed bed reactor. The EFB and HDPE as feedstock were located inside a metal half-cylindrical boat in a pyrolysis reactor. The characteristics of the pyrolysis oil product were analyzed in detail.

In this work, we have investigated the impact of co-pyrolysis of plastic waste (HDPE) with agricultural waste (EFB) for pyrolysis oil production. We demonstrated that the addition of HDPE waste in EFB reduces the pyrolysis oil yield. The pH of pyrolysis oil is increased with lower EFB, which is an advantage for its further use. 

The authors greatly acknowledge the Universitas Indonesia for financial support through Multidiscipline Grant No. 1650/UN2.R12/HKP.05.00/2015. Authors thank Assoc. Dr. Anwar Usman of Universiti Brunei Darussalam for providing graphical abstract of this manuscript.

Abnisa, F., Wan Daud, W.M.A, Sahu, J.N, 2014. Pyrolysis of Mixtures of Palm Shell and Polystyrene: An Optional Method to Produce a High Grade of Pyrolysis Oil. Environ Prog Sust Energy, Volume 33(3), pp. 1026–1033

Bhattacharya, P., Steele, P.H., Hassan, E.B.M., Mitchell, B., Ingram, L., Pittman Jr., C.U., 2009. Wood/Plastic Copyrolysis in an Auger Reactor: Chemical and Physical Analysis of the Products. Fuel, Volume 88(7), pp. 1251–1260

Chang, S.H., 2014. An Overview of Empty Fruit Bunch from Oil Palm as Feedstock for Bio-oil Production. Biomass and Bioenergy, Volume 62, pp. 174–181

Das, D.D., Schnitzer, M.I., Monreal, C.M., Mayer, P., 2009. Chemical Composition of Acid–base Fractions Separated from Bio-oil Derived by Fast Pyrolysis of Chicken Manure. Bioresource Technology, Volume 100, pp. 6524–6532

Degirmenci, V., Pidko, E.A., Magusin, P.C.M.M., Hensen, E.J.M., 2011a. Towards a Selective Heterogeneous Catalyst for Glucose Dehydration in Water: CrCl₂ Catalysis in a Thin Immobilized Ionic Liquid Layer. ChemCatChem, Volume 3, pp. 969–972

Degirmenci, V., Cinlar, B., Yilmaz, A., van Santen R.A., Shanks, B.H., Hensen, E.J.M., Uner, D., 2011b. Sulfated Zirconia Modified SBA-15 Catalysts for Cellobiose Hydrolysis. Catalysis Letters, Volume 141, pp. 33–42

Degirmenci, V., Hensen, E.J.M., 2014. Development of a Heterogeneous Catalyst for Lignocellulosic Biomass Conversion: Glucose Dehydration by Metal Chlorides in a Silica-supported Ionic Liquid Layer. Environmental Progress & Sustainable Energy, Volume 33(2), pp.  657–662

Egorov, R.I., Antonov, D.V., Valiullin, T.R., Strizhak, P.A., 2018. The Ignition Dynamics of the Water-filled Fuel Compositions. Fuel Processing Technology, Volume 174, pp. 26–32

Kusrini, E., Setiawan, E.A., Sofyan, N., 2018. Exploring Potential Materials, Science, and Technology for Improvements in Reusing Energy and Waste. International Journal of Technology, Volume 9(6), pp. 1085-1091

Gang, W., Aimin, L., 2008. Thermal Decomposition and Kinetics of Mixtures of Polylactic Acid and Biomass during Copyrolysis. Chinese Journal of Chemical Engineering, Volume 16(6), pp. 929–933

Kim, K.H., Eom, I.Y., Lee, S.M., Choi, D., Yeo, H., Choi, I.-G., Choi, J.W., 2011. Investigation of Physicochemical Properties of Biooils Produced from Yellow Poplar Wood (Liriodendron tulipifera) at Various Temperatures and Residence Times. Journal of Analytical and Applied Pyrolysis, Volume 92(1), pp. 2–9

Martí-Rosselló, T., Li, J., Lue, L., 2018. Quantitatively Modelling Kinetics through a Visual Analysis of the Derivative Thermogravimetric Curves: Application to Biomass Pyrolysis. Energy Conversion and Management, Volume 172, pp. 296–305

Oudenhoven, S.R.G., van der Ham, A.G.J., van den Berg, H., Westerhof, R.J.M., Kersten, S.R.A., 2016. Using Pyrolytic Acid Leaching as a Pretreatment Step in a Biomass Fast Pyrolysis Plant: Process Design and Economic Evaluation. Biomass and Bioenergy, Volume 95, pp. 388–404

Oozeerally, R., Burnett, D.L., Chamberlain, T.W., Walton, R.I., and Degirmenci, V., 2018. Exceptionally Efficient and Recyclable Heterogeneous Metal–Organic Framework Catalyst for Glucose Isomerization in Water. ChemCatChem, Volume 10(4), pp. 706–709

Pidko, E.A., Degirmenci, V., van Santen, R.A., Hensen, E.J.M., 2010. Glucose Activation by Transient Cr²⁺ Dimers. Angewandte Chemie International Edition, Volume 49(14), pp. 2530–2534

Purwanto, W.W., Supramono, D., Muthia, R., Firdaus, M.F., 2015. Effect of Biomass Types on Bio-oil Characteristics in a Catalytic Fast Pyrolysis Process with a Ni/ZSM-5 Catalyst. International Journal of Technology, Volume 6(7), pp. 1069–1075

Sukiran, M.A., Abnisa, F., Wan Daud, W.M.A., Bakar, N.A., Loh, S.K., 2017. A Review of Torrefaction of Oil Palm Solid Wastes for Biofuel Production. Energy Conversion and Management, Volume 149, pp. 101–120

Ro, D., Kim, Y.-M, Lee, I.-G., Jae, J., Jung, S.-C., Kim, S.C., Park, Y.-K., 2018. Bench Scale Catalytic Fast Pyrolysis of Empty Fruit Bunches over Low Cost Catalysts and HZSM-5 using a Fixed Bed Reactor. Journal of Cleaner Production, Volume 176, pp. 298–303

Rodionova, M.V., Poudyal, R.S., Tiwari, I., Voloshin, R.A., Zharmukhamedov, S.K., Nam, H., Zayadan, B., Bruce, B.D., Hou, H.J.M., Allakhverdiev, S.I., 2017. Biofuel Production: Challenges and Opportunities. International Journal of Hydrogen Energy, Volume 42(12), pp. 8450–8461

Sabil, K.M., Aziz, M.A., Lal, B., Uemur, Y., 2013. Effects of Torrefaction on the Physiochemical Properties of Oil Palm Empty Fruit Bunches, Mesocarp Fiber and Kernel Shell. Biomass & Bioenergy, Volume 56, pp. 351–360

Sharuddin, S.D.A., Abnisa, F., Wan Daud, W.M.A., Aroua, M.K., 2016. A Review on Pyrolysis of Plastic Wastes. Energy Conversion and Management, Volume 115, pp. 308–326

Sogancioglu, M., Yel, E., Ahmetli, G., 2017. Pyrolysis of Waste High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) Plastics and Production of Epoxy Composites with Their Pyrolysis Chars. Journal of Cleaner Production, Volume 165, pp. 369–381

Supramono, D., Jonathan, J., Haqqyana, H., Setiadi, S., Nasikin, M., 2016a. Improving Bio-oil Quality through Co-pyrolysis of Corn Cobs and Polypropylene in a Stirred Tank Reactor. International Journal of Technology, Volume 7(8), pp. 1382–1392

Supramono, D., Kusrini, E., Yuana, H., 2016b. Yield and Composition of Bio-oil from Co-Pyrolysis of Corn Cobs and Plastic Waste of HDPE in a Fixed Bed Reactor. Journal of the Japan Institute of Energy, Volume 95(8), pp. 621–628

Stefanidis, S.D., Kalogiannis, K.G., Iliopoulou, E.F., Michailof, C.M., Pilavachi, P.A., Lappas, A.A., 2014. A Study of Lignocellulosic Biomass Pyrolysis via the Pyrolysis of Cellulose, Hemicellulose and Lignin. Journal of Analytical and Applied Pyrolysis, Volume 105, pp. 143–150

Uzoejinwa, B.B., Hea, X., Wanga, S., El-Fatah Abomohra, A., Hu, Y., Wang, Q., 2018. Co-pyrolysis of Biomass and Waste Plastics as a Thermochemical Conversion Technology for High-grade Biofuel Production: Recent Progress and Future Directions Elsewhere Worldwide. Energy Conversion and Management, Volume 163, pp. 468–492

Zhang, Y., Degirmenci, V., Li, C., Hensen, E.J.M., 2011. Phosphotungstic Acid Encapsulated in Metal-organic Framework as Catalyst for Carbohydrate Dehydration to 5-hydroxymethylfurfural. ChemSusChem, Volume 4(1), pp. 59–64