Higher Heating Value Of Bio-oil Research Articles

Hydrothermal bio-oil yield and higher heating value of high moisture and lipid biomass: Machine learning modeling and feature response behavior analysis

The yield and higher heating value (HHV) of bio-oil products are significant performance parameters for the hydrothermal conversion of high-water and high-lipid biomass. Machine learning (ML) modeling prediction is a fast and convenient means of obtaining performance parameters. An informative dataset with 243 samples was prepared, and two highly adapted ML algorithms were used: Random Forest (RF) and Extreme Gradient Boosting Tree (XGBoost). It is interesting to note that the developed ML models demonstrated great prediction ability; for example, the regression coefficient (R2) of the XGBoost model for yield and HHV prediction was as high as 0.942 and 0.940, respectively. Furthermore, partial dependence plots (PDP) and SHapley Additive exPlanations (SHAP) interpretability methodologies were adopted to address the main contributions of the feature identification and response behavior analysis of the features. The results demonstrated that the biomass composition had the greatest effect on bio-oil yield, with fat contributing up to 40 %. In contrast, the elemental composition had the most significant effect on the HHV of bio-oil. Notably, hydrogen content affected the HHV of up to 4.5 units. The interaction response behavior showed that the interaction of the process parameters with feedstock properties was most common and significant. The information obtained from the response mechanism can be used to enhance the subsequent hydrothermal fuel preparation process for bio-oils.

Co-pyrolysis of sewage sludge and biomass waste into biofuels and biochar: A comprehensive feasibility study using a circular economy approach

Enormous annual sewage sludge (SS) volumes pose global environmental challenges owing to contamination and significant greenhouse gas emissions. Here, we investigated the economic viability of co-pyrolyzing SS and biomass waste to produce biofuels (bio-oil and gas) and biochar. Net present worth (NPW) analysis, the sale product break-even price, and sludge handling price (SHP) were used to determine the profitability of co-pyrolysis compared with SS pyrolysis alone and conventional treatment methods. In this study, the sale prices of biochar based on quality (i.e., stability, carbon sequestration effectiveness, and heavy metal content) were estimated to be 2.24, 1.44, and 0.98 CAD/kg for high-, medium-, and low-grade biochar. The bio-oil prices, estimated based on the higher heating values of bio-oil and diesel, ranged from 0.80 to 1.22 CAD/kg. Sawdust (SD) and wheat straw (WS) were the chosen co-pyrolysis feedstocks, with four mixing ratios (20, 40, 60, and 80 wt%). Economically, SD (40 wt% mixing ratio) co-pyrolysis achieved the best performance, with a maximum NPW of 8.71 million CAD. SD single and co-pyrolysis were the only profitable scenarios. Moreover, SS single pyrolysis and WS co-pyrolysis exhibited higher profitability than conventional SS treatment methods, with SHPs of 65 and 40 CAD/1000 kg dry sludge, respectively. Sensitivity analysis highlighted the dependence of economic performance on biochar and bio-oil market value. This study offers the first economic analysis of this approach and enhances our understanding of the potential of co-pyrolysis for biofuel and biochar production, providing innovative solutions for the environmental challenges of SS disposal.

Reducing nitrogen content in bio-oil from hydrothermal liquefaction of microalgae by using activated carbon-pretreated aqueous phase as the solvent

Hydrothermal liquefaction (HTL) is a promising thermochemical technology for converting wet biomass into liquid fuels, with aqueous phase (AP) as one main by-product. The strategy for recycling AP into the HTL process is extensively studied due to its potential to enhance bio-oil production. However, an increased concentration of nitrogen elements in the bio-oil has been reported in recycling cases. In the current work, the aqueous phase was first pretreated with activated carbon to solve this problem before recycling it back into the liquefaction system. Results showed that nitrogen content was decreased, and bio-oil quality was improved due to pre-adsorption. The optimal pretreatment conditions were 160 mg activated carbon and 40 min adsorption time. Although the bio-oil yield obtained from the recycling HTL with the pretreated solvent (35.75 wt%) was lower than the untreated case (39.77 wt%), the nitrogen content of the bio-oil was also reduced up to 39% simultaneously. Moreover, the bio-oil's higher-heating value (HHV) was increased slightly when using the pretreated solvent. And the content of n-hexadecanoic acid in the bio-oil was expanded due to the decline of N-based compounds. This study concluded that liquefaction of biomass with the activated carbon-pretreated AP solvent leading to high conversion efficiency and bio-oil quality would be more favorable from an economic point of view.

Enhancing aromatic hydrocarbon formation via catalytic depolymerization of lignin waste over Ru/WOx/N-C catalyst

Direct converting Kraft lignin into valuable chemicals by catalytic hydrogenolysis is a promising method to develop biomass valorization. In our research, the multifunctional porous carbon material catalyst was prepared for lignin depolymerization reaction. Through the introduction of ammonium oxalate as both foaming agent and nitrogen source increased the carbon materials surface area (608.74 m2/g), which improved the stability and dispersion of Ru and WOx nanoparticles. Based on the catalyst characterization and liquid product composition analysis, the lignin could quickly achieve hydrodeoxygenation process over the connected multi-stage pore structure assisted with Ru metal center and WOx oxophilic sites. Especially, the 96.89 wt% bio-oil yield, 36.85 wt% monomer yield and 20.85 wt% arenes yield were achieved over a porous 5Ru/30WOx/N-C catalyst. Under the optimal reaction condition, the higher heating values of bio-oil could increase to 35.68 MJ/kg. This research provided a new method for catalyst design towards highly efficient and selective hydrogenolysis of lignin to useful aromatic chemicals.

Conversion of biomass into biofuel by microwave pyrolysis: Assessment of energy and exergy aspect

Higher heating value, energy and exergy analysis of bio-oil and biochar from microwave pyrolysis have been assessed. The energy efficiency for the pyrolysis system has been analyzed by the comparisons of energy based on heating values. The exergy analysis was done using standard relationships by the fraction of energy actually available for practical uses as biofuel. The yield of bio-oil and its higher heating value (HHV) were increased by 2–13% and 25–130% respectively when the microwave power increased from 500 W to 700 W, then both are decreased at 900 W. Using activated carbon (AC) had a remarkable effect on increasing the yield and HHV of bio-oil by 18–31% and 3–7 times respectively more than other cases. By using the additives, the yield of biochar decreased remarkably, while its HHV increased by 12%-40% compared to without additive. The maximum energy and exergy rate (1.74 MJ/h) of the bio-oil were obtained at 700 W level of microwave power using AC additive, while for biochar were 1.95 MJ/h and 2 MJ/h when no additive used. The maximum values of energy and exergy of the bio-oil were computed to be 27% and 26% respectively at 700 W using AC as an additive. The maximum values of energy and exergy efficiency of biochar were calculated to be 33% and 32% respectively when pyrolyzed at 500 W using AC. The energy and exergy efficiencies of the pyrolysis system were computed to be maximum value of 53.3% and 52.8% respectively at 700 W using AC additive.

Processing of Leucaena Leucocepphala for renewable energy with catalytic fast pyrolysis

This research aimed processing of Leucaena Leucocepphala in a fluidized-bed reactor with catalysts for renewable energy. The reaction was tested over different type of catalysts such as natural zeolite, kaolin and dolomite. These catalysts were loaded under the heating zone with a supplementary hot filter. The rate of feedstock added in the reactor was 1 kg/h and the pyrolysis temperature was 500 °C. Product yields was calculated after each experiment was completed.The results demonstrated an optimum bio-oil yield of 65.1 wt% after undergoing fast pyrolysis. A reduction in bio-oil yield was observed when natural zeolite, kaolin and dolomite was employed during fast pyrolysis. The minimum bio-oil yield recorded for the dolomite catalyst was 54.5 wt%. On the other hand, kaolin catalyst produces a maximum bio-oil yield of 59.6 wt%. The organic content of bio-oil from kaolin catalyst increased significantly compared with other catalysts. Addition of an ESP condenser, instead of water-cooled condenser resulted in bio-oil with the highest heating value (HHV). Higher heating value of bio-oil derived from natural zeolite catalyst maximized at 35.8 MJ/kg and 37.3 MJ/kg, respectively. The range of hydrocarbon component of bio-oil was C15–C44 for ESP condenser and C12–C35 for water-cooled condenser. The availability of bio-oil was optimized when natural zeolite catalyst added into the process. On the other hand, density and viscosity of bio-oil was increased when dolomite catalyst was used. Additionally, the presence of dolomite catalyst reduced acidic compounds such as 2-Octenoic acid (C8H14O2) and Methyl propiolate (C4H4O2) in the bio-oil. Bio-oil yield was found to be significantly improved by the large pore diameter and small surface area of the catalyst. Among the three catalysts in was observed that kaolin catalyst gave the highest bio-oil yield. Natural zeolite catalyst was found to improved bio-oil product’s thermal quality. However, bio-oil with better viscosity and lower acidity was produced from the dolomite catalyst.

Estimation of fast pyrolysis bio‐oil properties from feedstock characteristics using rough‐set ‐based machine learning

In this work, a data-driven rough-set-based machine learning model has been proposed as a pre-processing and predictive modelling tool to predict the pyrolysis bio-oil properties based on pyrolysis temperature and feedstock characteristics. A database consisting of feedstock proximate and ultimate analyses, pyrolysis temperature, bio-oil's pH value, and bio-oil's higher heating value was compiled and used to train the rough-set-based machine learning model. The resulting rule-based rough-set-based machine learning model demonstrated promising strength, certainty, and coverage factor. Furthermore, the emergent patterns and mechanistic plausibility of the rough-set-based machine learning models were analysed. The generated rules illustrated reasonable predictive capability in estimating the higher heating value and pH value of bio-oil based on the feedstock characterisation and pyrolysis temperature. Rough-set-based machine learning model is thus demonstrated to be a simple and straightforward approach for feedstock composition and pyrolysis temperature selection in pyrolysis/co-pyrolysis bio-oil production.

Effect of algae (Scenedesmus obliquus) biomass pre-treatment on bio-oil production in hydrothermal liquefaction (HTL): Biochar and aqueous phase utilization studies.

Environmental concerns due to fossil fuel usage has turned the research interest towards biomass and bioenergy field. Renewable biomass such as microalgae provides numerous advantages as they can grow in wastewater; sequester carbon dioxide, economical and eco-friendly. In this study, effect of pretreatment of microalgae (Scenedesmus obliquus) biomass using post-hydrothermal liquefaction wastewater (PHWW) for bio-oil production through hydrothermal liquefaction at a temperature of 300°C was studied. Results showed liquefaction of pre-treated biomass yielded 48.53% bio-oil whereas 28.35% was resulted from biomass without pretreatment. The analysis of higher heating value of bio-oil showed that pretreated biomass oil has 36.19MJ.Kg-1 against non-pretreated biomass oil, which has 28.88MJ.Kg-1. Bio-oil (pretreated biomass) analysis revealed that 60% of compounds are in diesel and gasoline range with 58.09% of energy recovery. Bio-oil was rich in hydrocarbons of C7-C21 range with less oxygenated compounds. Carbon balance showed that an increase of 13% of carbon was sequestered in solid residue obtained from pretreated biomass and about 146% of increase also obtained in bio-oil.

CO-PYROLYSIS CANGKANG KELAPA SAWIT DAN LIMBAH PLASTIK KEMASAN

In the present study, the co-pyrolysis of biomass waste, i.e. palm kernel shells (PKS) and industrial packaging plastic waste, namely polyethylene terephthalate (PET) and polyethylene (PE) were conducted. Prior to the pyrolysis, the raw materials were analyzed by thermogravimetric and elemental procedures. The pyrolysis was conducted in a fixed bed reactor which was heated from room temperature to 500 °C in an N 2 atmosphere with a heating rate of 10 °C/min. The raw materials were weighted and mixed together manually with variations of weight composition ratios between biomass and plastic, i.e. 100% biomass (100/0); 90% biomass and 10% plastic (90/10); 70% biomass and 30% plastic (70/30); 50% biomass and 50% plastic (50/50); and 100% plastic (0/100). Then, they were put under pressure to obtain a pellet. The synergistic effect of biomass and plastic was investigated to see the difference between the pyrolysis products yields in theory and experiment. The bio-oil products were characterized by several methods and showed the potential to be used as a fuel. The optimum condition was obtained from 50/50 weight composition ratio. It was gained 30% improvement of the higher heating value of bio-oil, and the percentage area of hydrocarbon was contained in bio-oil increased from 4.68% to 53.40%.

Sawdust pyrolysis from the furniture industry in an auger pyrolysis reactor system for biochar and bio-oil production

This study investigated the potential of sawdust from the processing of Acacia wood for the furniture making industry to produce bio-oil and biochar in an auger pyrolysis reactor system. The necessary characterization to assess the suitability of feedstock and strategies the pyrolysis parameters was also carried out. The volatile matter, ash content, carbon content and the higher heating value of the sawdust feedstock were reported as 68.46 wt%, 1.13 wt%, 47.40 wt% and 19.33 MJ/kg, respectively, with very low nitrogen and sulfur content. The thermogravimetric (TGA and DTG) analysis of sawdust showed that the weight loss from biomass occurred in three main stages as a result of the removal of moisture and extractives, decomposition of hemicellulose, cellulose, and the lignin components. Based on the decomposition temperature window and peak conversion temperature the pyrolysis experiments were carried out in the range of 400–600 ℃ by maintaining the nitrogen flow rate, biomass feeding rate, rotation speed of the conveyer the residence time of materials and biomass particle size as 300 cm3/min, 180 g/h, 4.5 RPM, 5 min, and 0.5–1.0 mm, respectively. The yields of the non-condensable gases, biochar and bio-oil were reported in the ranges 16.70–38.47 wt%, 29.72–51.85 wt% and 29.40–45.10 wt%, respectively. The pyrolysis products were pragmatically analyzed to evaluate the influence on yield and their properties. The higher heating values of bio-oil produced were reported in the range 28.781–29.871 MJ/kg while the pH of bio-oil indicated the strongly acidic nature with values in the range of 2.9–3.4. Chemical compounds in bio-oils were categorized as phenols, nitrogen containing compounds, guaiacols, organic acids, ketones, anhydrous sugars, esters, and aldehydes. Biochar characterization showed an energy potential comparable to those of the low ranked coals with the higher heating values reported in the range of 25.01–25.99 MJ/kg. The surface morphological characteristics and Brunauer–Emmett–Teller (BET) analysis of the biochars indicated potential for other valued applications in the adsorption, environmental, catalyst, and agricultural context.

Effects of reaction conditions on products and elements distribution via hydrothermal liquefaction of duckweed for wastewater treatment

Wastewater treatment by duckweed is a naturally sustainable technology. However, its development is limited due to the lack of a follow-up treatment of duckweed. The duckweed was proposed for the treatment of rural domestic wastewater and agricultural wastewater, and it was further processed to produce bio-oil via hydrothermal liquefaction at various temperatures (250 °C–370 °C) and residence times (15–60 min). The highest bio-oil yield of 35.6 wt% was obtained at 370 °C, 45 min. The higher heating value of bio-oil was 40.85 MJ/kg, and the H/C ratio (1.72–1.98) was similar to that of petroleum (1.84). The gas chromatography-mass spectrometry analysis results revealed that the bio-oil mainly consisted of N-heterocycles, cyclic ketones, esters, amides, long-chain hydrocarbons, phenols, and aromatic intermediates. Valuable compounds (3-pyridinol, 2-pyrrolidinone, and its analogues) of high concentration were identified in the water-soluble organic matter. Compared with other materials, this study produced higher-quality bio-oil and water-soluble organic matter.

Food and Market Waste-A Pathway to Sustainable Fuels and Waste Valorization.

Food and market waste (FMW) is one of the most abundant unrecycled products which poses waste management issues and negative environmental impacts. Thermo-catalytic reforming (TCR) is a pyrolysis based technology which can convert a wide range of biomass wastes into energy vectors bio-oil, syngas, and char. This paper investigates the conversion potential of FMW into sustainable biofuels. The FMW was processed using a laboratory scale 2 kg/h TCR reactor. The process produced 7 wt % organic bio-oil, 53 wt % permanent gas, and 22 wt % char. The bio-oil higher heating value (HHV) was found to be 36.72 MJ/kg, comparable to biodiesel, and contained a low oxygen content (<5%) due to cracking of higher molecular weight organics. Naphthalene was detected to be the most abundant aromatic compound within the oil, with relative abundance of 12.95% measured by GC-MS. The total acid number of the oil (TAN) and viscosity were 11.7 mg KOH/g and 6.3 cSt, respectively. The gross calorific value of the produced biochar was 23.64 MJ/kg, while the permanent gas showed a higher heating value of approximately 17 MJ/Nm3. Methane (CH4) was found to be the largest fraction in the permanent gases reaching over 23%. This resulted either due to the partial methanation of biosyngas over the catalytically active FMW biochar or the hydrogenation of coke deposited on the biochar in the post reforming stage.

Hydrothermal Liquefaction and Photocatalytic Reforming of Pinewood (Pinus ponderosa)-Derived Acid Hydrolysis Residue for Hydrogen and Bio-oil Production

Pretreatment of lignocellulosic biomass (LCB) is a prerequisite for downstream bioconversion of its cellulosic components to second-generation biofuels. Acid hydrolysis pretreatment separates most of the hemicellulose and cellulose from lignin. However, the lignin-rich acid hydrolysis residue (AHR) may contain 20–50 wt % feedstock biomass. To improve the economics of LCB-based biorefinery, the AHR needs to be valorized. In this study, we have performed hydrothermal liquefaction (HTL) of AHR derived from the dilute acid treatment of pinewood for H₂ and bio-oil generation. A slurry of AHR at a biomass-to-water ratio of 1:30 was hydrothermally liquefied in the presence of a homogeneous Ni(NO₃)₂ catalyst at 250, 275, and 300 °C. About 16 wt % bio-oil and 51 mL of H₂ were generated at 300 °C and 60 min into the reaction. Based on elemental analysis, the higher heating value of bio-oil was found to be 29.8 MJ/kg. The aqueous coproduct generated during the HTL reaction was treated with activated carbon and subjected to the photocatalytic reforming (PR) process in the presence of a Pt/TiO₂ catalyst that produced an additional 90 mL of H₂ at NTP conditions. Preliminary calculations were performed to understand the energy recovery in terms of the products generated based on the total energy consumed for both HTL and PR processes.

Process optimization of biomass liquefaction in isopropanol/water with Raney nickel and sodium hydroxide as combined catalysts

Liquefaction co-catalyzed by Raney nickel and NaOH in isopropanol (2-PrOH)/H2O is an efficient method for transforming lignocellulosic biomass into bio-oil. The present study investigated the effect of reaction temperature, residence time, and dosage of the catalysts on the yield and composition of bio-oil. To understand the liquefaction mechanism, the transformation of lignin and cellulose at the same conditions was investigated as well. The results indicated that 240 °C was the optimum temperature in terms of bio-oil yield. It was also found that residence time had a great effect on not only the bio-oil yield but also the composition and higher heating value (HHV) of the bio-oil. Increasing the dosage of the catalysts also improved the yield and HHV of bio-oil. Most phenols in bio-oil were originated from lignin, while most ketones and hydrocarbons were produced by cellulose.

Characteristics of biochar and bio-oil produced from wood pellets pyrolysis using a bench scale fixed bed, microwave reactor

Microwave pyrolysis of wood pellets was investigated in a pilot scale fixed bed microwave reactor at various biomass loadings and microwave power levels. A fixed proportion of biochar (10% of biomass loading) was used as a microwave absorber in each test conditions. Effect of biomass loading and the power level on the product yields and on the characteristics of biochar and bio-oil products were examined. While the bio-oil yield decreased when the biomass loading was increased from 1500 g to 3500 g, the biochar and gaseous product yields increased with the biomass loading. However, the microwave power level shows an opposite trend. Biochar exhibited good higher heating value (31 MJ/kg) and possessed a fine pore size (<1 nm), which can be used as a fuel or a source of porous carbon. Higher heating value of bio-oil was found in the range 12–14 MJ/kg. Kinematic viscosities of bio-oils were estimated in the range 1.8–6.1 mm2/s at 40 °C that is similar to the viscosity requirement for the gas turbine applications. Moisture content in bio-oils was found in the range of 57.3–69.3%, which is higher than the upper limit of water content (30% wt.). Only a few chemicals, including furfural, phenol, 3-Methyl-1,2-Cyclipentanedione, 3-Methylphenol, and 4-Methylguaiacol were found in the bio-oils because of the high moisture content. Results of product characterization of biochar and bio-oils confirm that both microwave power level and biomass loading does not have any significant impacts. Further research can be carried out to find out the measures to reduce the moisture content in the bio-oil.

Optimization of bio-oil production from solid digestate by microwave-assisted liquefaction

Microwave-assisted direct liquefaction of solid digestate was carried out in polyethylene glycol and glycerol employing sulfuric acid as catalyst, in order to convert it into a biofuel. Response Surface Methodology (RSM) coupled with Box-Behnken Design (BBD) with a total of 15 individual experiments was used to optimize the conditions of three independent variables (temperature, reaction time and solvent-to-biomass ratio) related to the bio-oil yield, the higher heating value (HHV) of bio-oil and the energy use of microwave treatment. Desirability function was employed to determine the optimal reaction conditions of the liquefaction process. The results showed that at the optimal conditions the bio-oil yield, the HHV of bio-oil and energy use were respectively 59.38%, 28.48 MJ/kg, and 115.93 Wh. The predicted responses showed a good compliance to the obtained experimental data. The optimized bio-oil was further characterized using FTIR analysis while the properties of the solid digestate and the liquefaction residue were analyzed by means of SEM analysis.

Bio-oil production from hydrothermal liquefaction of Pteris vittata L.: Effects of operating temperatures and energy recovery

Hyper-accumulator biomass, Pteris vittata L., was hydrothermally converted into bio-oils via hydrothermal liquefaction (HTL) in sub-supercritical water. The distributions and characterizations of various products as well as energy recovery under different temperatures (250–390 °C) were investigated. The highest bio-oil yield of 16.88% was obtained at 350 °C with the hydrothermal conversion of 61.79%, where the bio-oil was dominated by alcohols, esters, phenols, ketones and acidic compounds. The higher heating values of bio-oil were in the range of 19.93–35.45 MJ/kg with a H/C ratio of 1.26–1.46, illustrating its high energy density and potential for use as an ideal liquid fuel. The main gaseous products were CO2, H2, CO, and CH4 with the H2 yield peaking at 22.94%. The total energy recovery from bio-oils and solid residues fell within the range of 37.72–45.10%, highlighting the potential of HTL to convert hyper-accumulator biomass into valuable fuels with high conversion efficiency.

Thermo-catalytic reforming of co-form® rejects (waste cleansing wipes)

Co-form® products are typically used for personal hygiene care (cleansing wipes), household cleaning (pads and mops) and absorbent applications. Co-form® is a thermo-bonded multilayer nonwoven composite and Kimberly-Clark patented its process in 2008. Co-form® rejects are composed of 30% plastic polypropylene and 70% wood pulp fibre. It is difficult to recycle and to-date no research articles explore pyrolytic valorisation for its energy recovery. This paper investigated pyrolytic valorisation of co-form® rejects into energy vectors. Pelletised co-form® rejects obtained from a secondary fibre paper mill were processed using a laboratory scale 2 kg/h Thermo-Catalytic Reforming (TCR®) reactor. The TCR® process combines intermediate pyrolysis, using an auger reactor to heat the material under moderate temperatures (350–450 °C) and moderate solid residence times (minutes) in the complete absence of Oxygen, with post catalytic reforming in a fixed bed reactor at 700 °C. Pelletised co-form® rejects were successfully converted into 12 wt% bio-oil, 9 wt% aqueous phase liquid, 8 wt% char and 71 wt% syngas products. The bio-oil higher heating value was found to be 39.36 MJ/kg, comparable to biodiesel. Naphthalene was found to be the most abundant aromatic compound within the oil, with a relative abundance of 15.22% measured by GC–MS. Oleic acid methyl ester (15.86%) was the most abundant long chain hydrocarbon detected. The higher heating value of produced gas was 11.02 MJ Nm3 and char 30.79 MJ/kg. TCR® conversion of co-form® rejects proved to be a feasible route for the valorisation of this waste stream into sustainable energy vectors. In previous works, gasification processes could not successfully convert organic waste streams with a high plastic content, without implications attributed to agglomeration and melting of plastics. The TCR® process overcome these issues with no evidence of agglomeration or melting of plastics present within the reactor. The success was believed to be through applying moderate heating rates (°C/min) and temperatures (max 700 °C), as well as the mechanical effect of continuous mixing of material within the reactor via the internal auger screw. Overall, TCR® is a promising future route for the valorisation of co-form® rejects to produce energy vectors.

Catalytic Hydrothermal Liquefaction of Food Waste Using CeZrOx

Approximately 15 million dry tons of food waste is produced annually in the United States (USA), and 92% of this waste is disposed of in landfills where it decomposes to produce greenhouse gases and water pollution. Hydrothermal liquefaction (HTL) is an attractive technology capable of converting a broad range of organic compounds, especially those with substantial water content, into energy products. The HTL process produces a bio-oil precursor that can be further upgraded to transportation fuels and an aqueous phase containing water-soluble organic impurities. Converting small oxygenated compounds that partition into the water phase into larger, hydrophobic compounds can reduce aqueous phase remediation costs and improve energy yields. HTL was investigated at 300 °C and a reaction time of 1 h for conversion of an institutional food waste to bio-oil, using either homogeneous Na2CO3 or heterogeneous CeZrOx to promote in situ conversion of water-soluble organic compounds into less oxygenated, oil-soluble products. Results with food waste indicate that CeZrOx improves both bio-oil higher heating value (HHV) and energy recovery when compared both to non-catalytic and Na2CO3-catalyzed HTL. The aqueous phase obtained using CeZrOx as an HTL catalyst contained approximately half the total organic carbon compared to that obtained using Na2CO3—suggesting reduced water treatment costs using the heterogeneous catalyst. Experiments with model compounds indicated that the primary mechanism of action was condensation of aldehydes, a reaction which simultaneously increases molecular weight and oxygen-to-carbon ratio—consistent with the improvements in bio-oil yield and HHV observed with institutional food waste. The catalyst was stable under hydrothermal conditions (≥16 h at 300 °C) and could be reused at least three times for conversion of model aldehydes to water insoluble products. Energy and economic analysis suggested favorable performance for the heterogeneous catalyst compared either to non-catalytic HTL or Na2CO3-catalyzed HTL, especially once catalyst lifetime differences were considered. The results of this study establish the potential of heterogeneous catalysts to improve HTL economics and energetics.

Fast pyrolysis of locally available green waste at different residence time and temperatures

ABSTRACTIn an effort to promote the sustainable utilization of waste biomass resources, the effects of biomass residence time and temperature on the fast pyrolysis yield, higher heating value (HHV), and gaseous composition were explored. Rice straw, corn stover, and its pyrolysis yields were analyzed using proximate analysis, ultimate analysis, and gas chromatography. Bio-oil yield of different biomass was characterized. Increase in biomass residence time favored bio-oil yield, gas yield, and HHV of char. Results showed that increase in fast pyrolysis temperature up to 500°C increases the bio-oil and gas yields while the char content decreases. Above 450-500°C, a sudden increase in gas yield was observed. HHVs of bio-oil and char were favored by increase in temperature up to an optimum value. Pyrolysis temperature had a pronounced effect on gas composition. Increase in temperature favored H2 and CH4 concentration.