Production of Liquid Biofuels from Microalgae Chlorella sp. via Catalytic Slow Pyrolysis

This study investigates the effects of catalyst preparation techniques on the yield and quality of liquid biofuel produced from slow catalytic pyrolysis of microalgae Chlorella sp. using various catalysts, including acid catalysts (HZSM-5) and base catalysts (activated carbon). The effects of different temperatures, catalyst loading, and reaction time on the yield and quality of liquid biofuels, including chemical composition, density, and the resulting viscosity at the optimal variable, were investigated. The results showed that slow catalytic pyrolysis using 1 wt.% activated carbon catalyst, a temperature of 550°C, and a reaction time of three hours produced a maximum yield of liquid biofuel at 50.38 wt.% with high aromatic hydrocarbons, less oxygen and acid, a density of 0.88 kg/L, and a viscosity of 5.79 cSt that satisfied specifications of biodiesel No. 2. Slow catalytic pyrolysis with a variety of catalyst types and catalyst preparation techniques affects the increase in yield and quality adjustment of liquid biofuel. The proposed technology can be further developed for commercial applications, replacing conventional diesel fuel.

Activated carbon; Chlorella sp.; HZSM-5; Liquid biofuel; Slow catalytic pyrolysis

Globally, CO₂ emissions are a product of the consumption of fossil fuels, especially crude oil, as the primary energy source impacting climate change and global warming (Hosseini et al., 2019). One of the alternative renewable energy resources that can meet global demand is biomass in the form of third-generation biofuels (Alaswad et al., 2015). The third generation of biofuels, especially those derived from microalgae biomass, is an ideal source of raw materials  and has advantages over the first and second generations biofuels in terms of cultivation, lipid composition, product yield, viscosity, density, and calorific value of biofuels (Mahfud et al., 2020; Shihab et al., 2020). However, the conversion efficiency of biofuel production from microalgae compared with biofuels from other biomass is still very low (Rizzo et al., 2013).

One of the thermochemical conversion methods to produce liquid biofuel (aka bio-oil) from microalgae biomass is pyrolysis (Yang et al., 2019). Studies related to pyrolysis have been reported in the literature. Supramono et al. (2016) investigated the co-pyrolysis of biomass and plastics (polypropylene). The results showed that adding polypropylene composition in the feed blend from 37.5 to 87.5 wt.% increased the bio-oil yield from 25.8 to 67.2 wt.%. The pyrolysis could also be used to fabricate advanced materials, such as as nanocomposites (Kusdianto et al., 2019) and fluorine-doped tin oxide (Yuwono et al., 2017).

The characteristics of microalgae Chlorella sp. as biofuel feedstock have been studied widely by many researchers. Hu et al. (2014) investigated the production of liquid bio-oil via fast catalytic pyrolysis from microalga Chlorella vulgaris using different catalysts and contents of activated carbon. They found that catalysts only affected the pyrolysis products. The maximum liquid and gaseous yield were achieved with activated carbon. Zainan et al. (2018) investigated slow catalytic pyrolysis of microalgae Chlorella vulgaris using Ni supported zeolite (Si/Al=30). The effects of different temperatures and catalyst to algae ratio on bio-oil yield and quality were analyzed. They found that the optimal pyrolysis temperature for slow catalytic pyrolysis of Chlorella vulgaris was 500°C with high hydrocarbon production and low oxygenated and acid compounds in the oil. Also, a lower catalyst to algae ratio produced a higher bio-oil yield was observed. The catalyst preparation method did not affect the yield but affected the bio-oil composition. Oxygenated bio-oil compounds were lower for catalyst prepared using wet impregnation than catalyst prepared using ion-exchange at all temperature variations (400°C and 500°C).

Although the studies mentioned above researched the Chlorella sp. as the bio-oil feedstock, studies on slow catalytic pyrolysis to increase the yield and quality of bio-oil from Chlorella sp. are still scarce in the literature, especially those using acid and base types of catalysts. In this study, we investigated the production of bio-oil (i.e., bio-oil yield) using various types of catalysts, including acid catalysts (HZSM-5) and base catalytic (activated carbon) with variations of catalyst treatment. The quality of bio-oil, including its chemical composition, density, and viscosity, at optimum conditions of catalyst treatment, temperature, and reaction time, was analyzed. The primary outcome of this study is expected to produce bio-oil that can easily meet the requirements of diesel fuel No. 2 in commercial applications. 

    The yield and quality of liquid biofuel from microalgae Chlorella sp. via slow catalytic pyrolysis is influenced by the type of catalyst (acid and base catalyst) and catalyst preparation method. The conditions for slow catalytic pyrolysis include temperature, catalyst amount of algae, type of catalyst, and the optimum reaction time for liquid biofuel yield. The maximum yield composed of aqueous and organic fractions is 550^oC, 1 wt.% activated carbon catalyst and 3 hours. The characteristics of liquid biofuels in chemical composition, density, and viscosity at optimum process conditions show that the type of catalyst and catalyst preparation method affects the yield and quality of the product.

    This work was financially supported by the Indonesian Ministry of Research, Technology and Higher Education (RISTEK-DIKTI) through the basic research of higher education excellence scheme.

Alaswad, A., Dassisti, M., Prescott, T., Olabi, A.G., 2015. Technologies and Developments of Third Generation Biofuel Production. Renewable and Sustainable Energy Reviews, Volume 51, pp. 1446–1460

Amin, A., Gadallah, A., El Morsi, A.K., El-Ibiari, N.N., El-Diwani, G.I., 2016. Experimental and Empirical Study of Diesel and Castor Biodiesel Blending Effect, On Kinematic Viscosity, Density and Calorific Value. Egyptian Journal of Petroleum, Volume 25(4), pp. 509–514

Aysu, T., Maroto-Valer, M.M., Sanna, A., 2016. Ceria Promoted Deoxygenation and Denitrogenation of Thalassiosira Weissflogii and its Model Compounds by Catalytic In-Situ Pyrolysis. Bioresource Technology, Volume 208, pp. 140–148

Conti, R., Pezzolesi, L., Pistocchi, R., Torri, C., Massoli, P., Fabbri, D., 2016. Photobioreactor Cultivation and Catalytic Pyrolysis of the Microalga Desmodesmus Communis (Chlorophyceae) for Hydrocarbons Production by HZSM-5 Zeolite Cracking. Bioresource Technology, Volume 222, pp. 148–155

Dai, M., Xu, H., Yu, Z., Fang, S., Chen, L., Gu, W., Ma, X., 2018. Microwave-Assisted Fast Co-Pyrolysis Behaviors and Products between Microalgae and Polyvinyl Chloride. Applied Thermal Engineering, Volume 136, pp. 9–15

Du, Z., Li, Y., Wang, X., Wan, Y., Chen, Q., Wang, C., Lin, X., Liu, Y., Chen, P., Ruan, R., 2011. Microwave Assisted Pyrolysis of Microalgae for Biofuel Production. Bioresource Technology, Volume 102(7), pp. 4890–4896

Duan, P., Bai, X., Xu, Y., Zhang, A., Wang, F., Zhang, L., Miao, J., 2013. Non-Catalytic Hydropyrolysis of Microalgae to Produce Liquid Biofuels. Bioresource Technology, Volume 136, pp. 626–634

Hosseini, S.M., Saifoddin, A., Shirmohammadi, R., Aslani, A., 2019. Forecasting of CO₂ Emissions in Iran based on Time Series and Regression Analysis. Energy Reports, Volume 5, pp. 619–631

Hu, Z., Ma, X., Li, L., Wu, J., 2014. The Catalytic Pyrolysis of Microalgae to Produce Syngas. Energy Conversion and Management, Volume 85, pp. 545–550

Hu, Z., Zheng, Y., Yan, F., Xiao, B., Liu, S., 2013. Bio-Oil Production through Pyrolysis of Blue-Green Algae Blooms (BGAB): Product Distribution and Bio-Oil Characterization. Energy, Volume 52, pp. 119–125

Kusdianto, K., Widiyastuti, W., Shimada, M., Nurtono, T., Machmudah, S., Winardi, S., 2019. Photocatalytic Activity of ZnO-Ag Nanocomposites Prepared by a One-Step Process using Flame Pyrolysis. International Journal of Technology, Volume 10(3), pp. 571–581

Li, G., Xiang, S.N., Ji, F., Zhou, Y.G., Huang, Z.G., 2017. Thermal Cracking Products and Bio-Oil Production from Microalgae Desmodesmus sp. International Journal of Agricultural and Biological Engineering, Volume 10(4), pp. 198–206

Mahfud, M., Kalsum, U., Aswie, V., 2020. Biodiesel Production through Catalytic Microwave In-situ Transesterification of Microalgae (Chlorella sp.). International Journal of Renewable Energy Development, Volume 9(1), pp. 113–117

Mostafazadeh, A.K., Solomatnikova, O., Drogui, P., Tyagi, R.D., 2018. A Review of Recent Research and Developments in Fast Pyrolysis and Bio-Oil Upgrading. Biomass Conversion and Biorefinery, Volume 8, pp. 739–773

Pattiya, A., 2011. Bio-oil Production via Fast Pyrolysis of Biomass Residues from Cassava Plants in a Fluidised-Bed Reactor. Bioresource Technology, Volume 102, pp. 1959–1967

Pattiya, A., Sukkasi, S., Goodwin, V., 2012. Fast Pyrolysis of Sugarcane and Cassava Residues in a Free-Fall Reactor. Energy, Volume 44(1), pp. 1067–1077

Pourkarimi, S., Hallajisani, A., Alizadehdakhel, A., Nouralishahi, A., 2019. Biofuel Production Through Micro-And Macroalgae Pyrolysis – A Review of Pyrolysis Methods and Process Parameters. Journal of Analytical and Applied Pyrolysis, Volume 142, https://doi.org/10.1016/j.jaap.2019.04.015

Rizzo, A.M., Prussi, M., Bettucci, L., Libelli, I.M., Chiaramonti, D., 2013. Character of Microalg Chlorella as a Fuel and its Thermogravimetric Behavior. Applied Energy, Volume 102, pp. 24–31

Shihab, M.A., Dhahir, M.A., Mohammed, H.K., 2020. Kinetic Study of Air Bubbles-Cetyltrimethylammonium Bromide (CTAB) Surfactant for Recovering Microalgae Biomass in a Foam Flotation Column. International Journal of Technology, Volume 11(3), pp. 440–449

Supramono, D., Jonathan., Haqqyana., Setiadi., Nasikin M., 2016. 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. 1381–1391

Thahir, R., Altway, A., Juliastuti, S.R., Susianto., 2019. Production of Liquid Fuel from Plastic Waste using Integrated Pyrolysis Method with Refinery Distillation Bubble Cap Plate Column. Energy Reports, Volume 5, pp. 70–77

Tripathi, M., Sahu, J.N., Ganesan, P., 2016. Effect of Process Parameters on Production of Biochar from Biomass Waste through Pyrolysis: A Review. Renewable and Sustainable Energy Reviews, Volume 55, pp. 467–481

Williams, P.T., Horne, P.A., 1995. The In?uence of Catalyst Regeneration on the Composition of Zeolite Upgraded Biomass Pyrolysis Oils. Fuel, Volume 74(12), pp. 1839–1851

Yang, C., Li, R., Zhang, B., Qiu, Q., Wang, B., Yang, H., Ding, Y., Wang, C., 2019. Pyrolysis of Microalgae: A Critical Review. Fuel Processing Technology, Volume 186, pp. 53–72

Yuwono, A.H., Arini, T., Lalasari, L.H., Sofyan, N., Ramahdita, G., Nararya, A., Firdiyono, F., Andriyah, L., Subhan, A., 2017. The Effect of Various Precursors and Solvents on the Characteristics of Fluorine-Doped Tin Oxide Conducting Glass Fabricated by Ultrasonic Spray Pyrolysis. International Journal of Technology, Volume 8(7), pp. 1336–1344

Zainan, N.H., Srivatsa, S.C., Li, F., Bhattacharya, S., 2018. Quality of Bio-Oil from Catalytic Pyrolysis of Microalgae Chlorella Vulgaris. Fuel, Volume 223, pp. 12–19