Study Of Co-pyrolysis Of Seaweed Biomass With Waste Plastic For Enhanced Biofuel Production

To understand the co-pyrolysis of seaweed biomass with waste plastics for enhanced biofuel production,this research project was conducted.This was made possible by investigating the co-pyrolysis of various blends of Enteromorpha prolifera(EP),a typical green seaweed(macoralgae)with waste plastic(high density polyethylene(HDPE))under different pyrolysis conditions using the fixed-bed reactor,thermogravimetric analyzer,pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)analysis,gas chromatography/ mass spectrometry(GC/MS)analysis,Fourier Transform Infrared(FTIR)spectroscopy analysis as well as modeling,simulations and optimization approaches.In the first study,the co-pyrolysis of the seaweed(Enteromorpha prolifera(EP))and waste plastic(HDPE),(with or without the catalyst HSZM-5)was investigated in a fixed-bed reactor and thermogravimetric analyzer for production of enhanced biofuels.Thus,in this study,the thermal behaviors,synergistic effects,product distributions/characteristics and kinetics of co-pyrolysis and catalytic co-pyrolysis of the seaweed(EP)and waste plastic(HDPE)for enhanced biofuels production were investigated.The novelty in results/findings and the significance of the results are outlined as follows:(i)Results unveiled that existence of synergy inhibited catalytic coking and reduced solid residues’ formation.The results also revealed that co-pyrolysis lowered the contents of the acids,oxygenates and nitrogencontaining compounds in the bio-oils,while the aromatics and light hydrocarbons contents of the oils were significantly increased.(ii)It was also observed that the addition of the HZSM-5 zeolite catalyst further improved the reaction activity,yields and selectivity of aliphatic hydrocarbons than the aromatics,and reduced the activation energy without changing the reaction mechanisms.Thus,the relative contents of the carboxylic acids/esters(41.72%)were observed to decrease by 13.57% and 19.87%,respectively,during the copyrolysis and catalytic co-pyrolysis processes while that of the nitrogen-containing compounds(19.73%)was reduced by 7.3% and 10.28% during the co-pyrolysis and catalytic co-pyrolysis processes,respectively.However,the relative content of the hydrocarbons(18.47%)was observed to increase by 32.05% and 45.70%,respectively,in the co-pyrolysis and catalytic co-pyrolysis oils.(iii)Besides,non-isothermal kinetic analyses were performed using the thermogravimetric analysis(TGA)data via five different kinetics evaluation methods: Friedman,Flynn-Wall-Ozawa(FWO),Vyazovkin,Kissinger-Akahira-Sunose(KAS)methods and distributed activation energy method(DAEM),as the single kinetics evaluation model lacks the flexibility to account for different types of materials without further modifications to reaction scheme.Thus,a comparison with different models could support the results,if differences were not so high.The kinetics studies’ results suggested that the catalytic co-pyrolysis could reduce,significantly,the energy inputs of the process by reducing the activation energy.(iv.)It was also noticed that the FTIR spectra of the co-pyrolysis and catalytic co-pyrolysis oils were consistent with the results of the GC/MS analysis of oils from co-pyrolysis and catalytic copyrolysis.(v)Thus,the results of this study provide valuable information for developing effective strategies for co-pyrolysis systems’ design,operational planning/regulations,resource recovery/recycling and waste management.In the second study,the co-pyrolysis of the seaweed(EP)and waste plastic(HDPE)was modeled based on their mass loss and mass loss rate profiles of volatile generation during the co-pyrolysis process using two different types of approaches of modeling(i.e.,non-interactive and interactive approaches)to investigate the energy-related synergistic effects between the seaweed(EP)and the waste plastic(HDPE)during co-pyrolysis.The novelty in results/findings in this study are highlighted as follows:(i)Two modeling approaches were proposed and employed in the evaluation of the possible energy-related synergistic effects that exist between the seaweeds(EP)and the waste plastics(HDPE)during co-pyrolysis.(ii)The results of the energy utilization during the co-pyrolysis process indicated a significant reduction in the energy used for the co-pyrolysis of the seaweeds(EP)and waste plastic(HDPE)for both proposed modeling approaches.However,the second modeling approach(i.e.,the interactive approach which allowed interactions between the feedstock materials)displayed a greater reduction(of about 7.82%)in the overall energy utilization during the co-pyrolysis process than the first approach,most especially when the mass percentage of the waste plastic(HDPE)in the feedstock mixture was 25 wt.%.(iii)The results of the co-pyrolysis modeling and simulation studies also revealed that the co-pyrolysis of seaweeds(EP)with waste plastic(HDPE)has the prospects of minimizing the energy inputs during the co-pyrolysis process,improving the pyrolysis products’ quality and quantity,maximizing the valuable pyrolysis product fractions,and enhancing the overall pyrolysis process’ efficiency.Furthermore,the third study of this research project focuses on the investigation of the co-pyrolysis of the seaweeds(EP)and the waste plastic(HDPE)in a fixed-bed reactor for maximum production of enhanced biofuels,but with emphasis on the modeling and simulation of the effects of co-pyrolysis parameters on the yields,and then optimization studies for maximum production of enhanced biofuels.The novelty in results/findings in this study and the significance of its results are summarized as follows:(i)The main and interaction effects of three effective co-pyrolysis parameters,(pyrolysis temperature,feedstock blending ratio and heating rate)on the oil,char and gas yields were modeled and simulated,respectively,and optimal conditions for maximum yield of enhanced biofuels were predicted.Analysis of variance was performed to determine whether the fit of the multiple regressions is significant for the second order model.(ii)Properties of oils and chars produced during the process were determined.Results of the determined fuel properties unveiled that the synergistic effects of co-pyrolysis of seaweeds(EP)and waste plastic(HDPE)could improve the fuel quality,besides increasing the yield rates.(iii)Results of statistical analysis conducted revealed that the HDPE mass percentage in the feedstock blends,pyrolysis temperature and heating rate significantly influenced the oil,char and gas yield rates.Optimal conditions for maximum yield of enhanced bio-oil were thus obtained as 492 oC and 17.8oC/min with 80% mass of HDPE in the feedstock blend.Confirmatory tests gave 76.84%,76.27% and 76.65% of oils compared to the maximum predicted value of 76.0%,which validated that the model developed was adequate and of low error.(iv.)The results of this study also provided valuable information for development of effective strategies for design of co-pyrolysis systems,operational planning and regulations,resource recovery/recycling and waste management.The fourth study of this research project compares the results of the co-pyrolysis of the seaweeds(EP)and waste plastic(HDPE)with those of a typical lignocellulosic biomass(rice husk)under the same conditions(of pyrolysis temperatures and heating rates)in a fixed-bed reactor.Besides,the effects of the co-pyrolysis parameters on the products’ yield were modeled and simulated in both cases and the results were then compared.Likewise,the results of the numerical optimization studies for maximum yield of enhanced biofuels from each blend of the two different feedstock materials with the seaweed(macrolagae),were also compared.The results of the treatment of the seaweed biomass with waste plastic(HDPE)were as presented above in the third study of this research project while the novelty in results/findings from the co-pyrolysis of seaweeds with lignocellulosic biomass(rice husk)and the significance of the results are summarized as follows:(i)Results of the co-pyrolysis of seaweed with lignocellulosic biomass(rice husk)revealed that the rice husk(RH)mass percentage in the feedstock blends,pyrolysis temperature and heating rate significantly influenced the bio-oil and char yields.The optimal conditions for maximum oil yield were obtained as a temperature of 455?C and heating rate of 20 o C/min with 80% mass of RH in the feedstock blend.The confirmatory tests gave 48.20%,48.05% and 47.90% of bio-oil yields compared to the predicted maximum value of 47.70%,which validated that the model developed was adequate and the error in the prediction is low.(ii)The results of this study also provided relevant reference information for developing effective strategies in terms of resource recovery/recycling and organic waste management,as well as overall copyrolysis process’ efficiency enhancement.The final study of this research project investigated the pyrolysis mechanisms and characteristics of the seaweed(Enteromorpha prolifera(EP))based on its model compounds(castor oil,soybean protein and glucose),the roles and interactions of the major components(lipids,proteins and carbohydrates)during pyrolysis as a preliminary study which provides an important basis for easy understanding of the complex mechanism of seaweed co-pyrolysis.Thus,in this study,Py-GC/MS analysis was employed for identification and quantification of the entire compositions of the seaweed and its model compounds,with or without the HZSM-5 catalyst.The novelty in results/findings in this study are thus highlighted as follows:(i)Several possible reaction pathways were proposed for the pyrolysis of seaweed based on its model components and their interactions using the results obtained via Py-GC/MS analysis of the individual feedstock materials and their blends as well as the GC/MS analysis of bio-oils produced from their fixed-bed reactor experiments.(ii)Besides,the results of this study also unveiled that castor oil offered the highest contribution to bio-oil formation among other model compounds,however,it pyrolyzes at a higher temperature region,while the bio-oil from soybean protein pyrolysis contains more N-heterocyclic compounds and phenols than those of the other model compounds.(iii)The study’s results also indicated a considerable improvement in the aromatic hydrocarbon yields as the catalyst to feedstock ratio increased.(iv.)The results of this study have also provided the essential fundamentals for easy understanding of the complex mechanisms of seaweed co-pyrolysis,improvement of reactor’s design,pyrolysis process optimization and scaling up of operations.Thus,the overall results of this research project have made available valuable information for developing effective strategies for clean energy recovery via co-pyrolysis of residual seaweed biomass and waste plastics,co-pyrolysis systems’ design,operational planning/regulations,process parameters’ optimization,process scaling up into a large industrial scale,resource recovery/recycling and effective waste management.Thus,for future research work on the co-pyrolysis of seaweeds and waste plastics,it is therefore recommended that further studies should be focused on understanding of the entire mechanisms of co-pyrolysis of seaweeds and waste plastics,understanding the mechanisms of the co-pyrolysis products distributions,understanding the effects of the minerals that are indigenously present in the seaweed biomass during the co-pyrolysis of its blends with waste plastics,and also the application of varieties of catalysts and determination of their effects on the activation energy of the co-pyrolysis process in order to obtain the best suitable catalyst for the process.