Showing papers in "Biomass & Bioenergy in 2020"
TL;DR: In this article, the reaction pathways including negative and positive effects during (co)-HTC of biomass and plastic wastes are thoroughly concluded, in particular, the co-HTC in chlorinated plastic and biomass can enhance the dechlorination and inorganics removal from hydrochar.
Abstract: Hydrothermal carbonization (HTC) as a promising thermochemical process can convert organic solid wastes (e.g., biomass, plastics) into valuable products (i.e., hydrochar) at relatively low temperatures (180–250 °C) and saturated pressures (2–10 MPa). Hydrothermal conversion generally occurs via dehydration, polymerization and finally carbonization reactions. The carbon materials derived from hydrochar have high potential in various applications such as solid fuel, supercapacitor, fuel cell, and sorbent. Although the energy densification of hydrochar was increased at higher temperatures, most of the benefit was achieved at modest temperatures. Chemical structures of hydrochars include crosslinks of aromatic polymer, surface porosity, organic functional groups and ultimate components. All of these characteristics can be changed significantly by HTC, influencing the reactivity and fuel properties of hydrochars. The reaction pathways including negative and positive effects during (co)-HTC of biomass and plastic wastes are thoroughly concluded. In particular, the co-HTC of chlorinated plastic (e.g., PVC) and biomass can enhance the dechlorination and inorganics removal from hydrochar.
201 citations
TL;DR: The emergence of high throughput, next-generation sequencing techniques has enriched the databases of genes encoding glycoside hydrolase classes commonly involved in lignocellulose decomposition, and this knowledge can be readily used to analyse the involved processes.
Abstract: Lignocellulose, the most abundant and renewable resource on Earth is an important raw material, which can be converted into high value products. However, to this end, it needs to be pretreated physically, chemically, or biologically. Its complex structure and recalcitrance against physical, chemical, or biological degradation render its breakdown an important target of study. The understanding of the enzymatic processes of lignocellulose breakdown and the changes in its chemistry are thus essential. Here, we review the current analytical challenges in the analysis of lignocellulose composition, lignocelluloytic pretreatment, analysis of enzymatic hydrolysis catalyzed by cellulases or hemicellulases and their biotechnological applications. Complex techniques including biochemical, genomic, and metagenomics methods such as high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD), Respiration Activity Monitoring System (RAMOS), and next-generation sequencing are described. HPAEC-PAD is a promising, rapid, and reliable analytical technique for sugar quantification following lignocellulose breakdown. RAMOS is an effective technique for monitoring the growth of microorganisms during the different phases of enzyme production, enzymatic hydrolysis, and fermentation. The emergence of high throughput, next-generation sequencing techniques has enriched the databases of genes encoding glycoside hydrolase classes commonly involved in lignocellulose decomposition, and this knowledge can be readily used to analyse the involved processes. Still, novel analytical methods are highly welcome to understand the complete process of lignocelluloytic breakdown. In order to decrease environmental pollution and to save energy, lignocellulose conversion needs to be promoted in order to effectively compete with fossil resources on a global scale in future.
148 citations
TL;DR: Current advances and innovation in on-site cellulolytic enzymes production using plant biomass, and application of the enzymes in lignocellulose conversion to fermentable sugars for biofuel production are focused on.
Abstract: The potential of lignocellulosic feedstock has been widely studied, mainly for biofuels production, which usually requires an enzymatic step on the process. Cellulolytic enzymes have been studied as input for bioconversion and as a product from lignocellulose fermentation. The integration of these two perspectives may lead to an economically viable approach for second generation biofuels production, which is nowadays difficult due to high cost of commercial cellulase. Conversely, enzyme production by fermentation of lignocellulosic substrates is inexpensive and the hydrolytic activity of enzymes produced on these substrates, which are to be hydrolyzed, may be better than those enzymes produced on other materials, such as cellulose. Many studies have defined the ideal conditions for cellulase production and saccharification processes separately. In contrast, few reports have developed a unique and integrated process, based on the same feedstock. This review is focused on current advances and innovation in on-site cellulolytic enzymes production using plant biomass, and application of the enzymes in lignocellulose conversion to fermentable sugars for biofuel production.
126 citations
TL;DR: In this article, a summary of the extensive study that has been devoted to the catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic compounds and the conversion of raw Lignin into hydrocarbon liquid fuels is presented.
Abstract: Petroleum, one of the fossil fuels, is still the main source for liquid fuel production. Lignin derived from renewable biomass has the potential to replace petroleum. The abundance of aromatic units in lignin makes it potential to produce high-value liquid fuel. This review offers a summary of the extensive study that has been devoted to the catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic compounds and the conversion of raw lignin into hydrocarbon liquid fuels. Based on the product classification (cyclohexanes and arenes), different catalytic systems, mainly including catalyst species, solvents and reaction conditions, are analyzed in detail. A model study of lignin-derived compounds (phenolic monomers and dimers) is usually carried out to elaborate on the HDO reaction mechanism. 100% yield of hydrocarbon liquid fuels can be achieved in most tests. With respect to the real lignin-derived bio-oil, however, hydrocarbon yields only reach 16.2%–62.8% due to the various components and high instability of the substrate. The technical barriers and challenges in this part are highlighted throughout. Moreover, the conversion of raw lignin is also comprehensively summarized, which actually combines the depolymerization of lignin and HDO of lignin-derived bio-oil in one pot, and its hydrocarbon yields are generally lower than those of lignin-derived bio-oil. In light of this, the important features of raw lignin that influence the production of hydrocarbon liquid fuels are adequately addressed. Overall, this paper focuses on the scientific and technological advances of hydrocarbon liquid fuel production from lignin, and the potential strategies to produce renewable fuels from lignin are discussed.
117 citations
TL;DR: In this paper, a fixed bed reactor has been used to assess the influence of slow pyrolysis process parameters on biochar yield from rice husk, and an ANOVA was utilized to verify the statistical significance of process parameters.
Abstract: A fixed bed reactor has been used to assess the influence of slow pyrolysis process parameters on biochar yield from rice husk. Taguchi's method (L9) was used for such a purpose, which four parameters varied according to three different levels: heating rate (β) of 5, 10 and 20 °C/min; temperature (T) of 300, 400, and 500 °C; residence time (t) of 3600, 5400 and 7200 s; rice husk mass (m) of 125, 250, and 500 g. ANOVA were utilized to verify the statistical significance of process parameters. Different physical-chemistry techniques have been performed to assess the energy potential of processing rice husk through thermochemical processes. The results showed that the highest biochar yield (37.71 %wt) was achieved through the following experimental conditions: 500 g of biomass, β = 20 °C/min, T = 300 °C, and t = 5400 s. However, the highest heating value (HHV = 23.41 MJ/kg) was obtained by using 125 g of biomass, β = 10 °C/min, T = 500 °C, and t = 5400 s. However, optimal conditions for higher fixed carbon content (60.10 %wt) were 500 g of biomass, β = 5 °C/min, T = 500 °C, and t = 7200 s. It was 49.05% higher than HHV found for raw rice husk. ANOVA results have revealed that temperature is the most significant parameter for the slow pyrolysis process. Furthermore, Taguchi's method was applied to define the levels of experimental conditions and optimize the process. Energy ratio assessment yielded values ranging between 0.38 and 1.77, which indicates that it is technically feasible to obtain energy gains through the slow pyrolysis of rice husk.
91 citations
TL;DR: In this article, the potential applications of HTL products (bio-crude, aqueous phase, solid residue, and gas) were thoroughly discussed, and the current challenges of treating HTL treatment, especially for the continuous operation, to produce bio-based fuel and chemicals was reviewed.
Abstract: Lignocellulosic biomass is a promising alternative to petroleum oil for producing energy and chemicals, owing to its abundance and sustainability. In the past decades, extensive research has applied a wide range of thermo-chemical technologies for converting biomass into value-added products. Among them, hydrothermal liquefaction (HTL) is regarded to be one of the most effective techniques to produce bio-fuels and bio-based chemicals. However, there are still several technical barriers that must be addressed before the industrialization of HTL technology. Although many previous reviews have summarized the reaction mechanism, properties of liquefaction products, and various operating parameters, few articles have discussed the potential applications of HTL products and the techno-economic problems facing by the industrialization of HTL. Therefore, in this review, the possible applications of HTL products (bio-crude, aqueous phase, solid residue, and gas) were thoroughly discussed. In addition, the current challenges of HTL treatment, especially for the continuous operation, to produce bio-based fuel and chemicals is reviewed. Finally, the possible future directions and the main conclusions are covered.
82 citations
TL;DR: In this article, the authors reported facile and cost-effective method to produce porous activated carbons for the first time by physical activation method using two different biomass sources Syzygium cumini fruit shells (SCFS) and Chrysopogon zizanioides roots (CZR) for fabrication of symmetric supercapacitors.
Abstract: Synthesis of biomass derived microporous activated carbon materials has fascinated attention in the emerging field of energy storage due to its high specific surface area, excellent electrical conductivity, low cost and environmental benevolence. Herein, we report facile and cost-effective method to produce porous activated carbons for the first time by physical activation method using two different biomass sources Syzygium cumini fruit shells (SCFS) and Chrysopogon zizanioides roots (CZR) for fabrication of symmetric supercapacitors. Biomass-derived activated carbon (BAC) materials were obtained via a two-step synthesis: (i) carbonization at 700 °C in N2 atmosphere (ii) CO2 activation at 700 °C in N2 atmosphere. The formation of high surface area and disordered micropores on the carbon by CO2 activation was identified by N2 adsorption-desorption and FE-SEM techniques. SCFS-AC and CZR-AC exhibit enhanced electrochemical performances in three-electrode configuration showing their high specific capacitances with good capacitance retention. These biomass derived activated carbon (BAC) based symmetric supercapacitors deliver energy density maximum of 27.22 W h kg−1 (SCFS-AC) and 16.72 W h kg−1 (CZR-AC) at 200 W kg−1 power density with an outstanding cycling stability over 5000 cycles. This work offers an environmentally safe and innovative approach to control the porosity in BAC for energy storage applications.
77 citations
TL;DR: In this article, the performance of anaerobic co-digestion of food waste with chicken manure was investigated for overcoming the challenges due to process inhibition during mono digestion.
Abstract: Anaerobic co-digestion in thermophilic condition leads to efficient waste treatment and energy recovery through accelerated and enhanced synergism. The performance of anaerobic co-digestion of food waste with chicken manure was investigated for overcoming the challenges due to process inhibition during mono-digestion of food waste. The bench scale anaerobic Continuously Stirred Tank Reactor (CSTR) system with the working volume of 87 L in wet condition with 10% total solids content was used for this study. Though thermophilic food waste anaerobic digestion indicated high methane yield and solids reduction, the process stability was affected at higher loading. Whereas, the reduction in FOS/TAC value (the ratio of volatile fatty acids to total alkalinity) through co-digestion indicated the higher capacity for organic loading rate in the anaerobic co-digestion system due to synergistic effect of microorganisms, buffering capacity and nutrient balance by C/N adjustment in the feedstock. Moreover, the percentage increases of specific methane yields in co-digestion compared with mono-digestion was found to be 33.2%, 10.4%, 12.1% and 89.9% at organic loading rates (OLR) of 1, 2, 3 and 4 kg VS‧m−3‧d−1 respectively, as a consequence of the improvement in stability through co-digestion.
69 citations
TL;DR: A systematic review of BSC modeling and optimization to identify future research directions and show that researchers are motivated to use mixed integer programming models for BSC problems because of the complexities of nonlinear models as well as the simplicity of the linear approaches.
Abstract: Biomass is a valuable renewable source of energy as an alternative to fossil fuels. The main barriers in biomass and biofuel development are feedstock high cost, lack of reliable supply, and uncertainties. A systematic review of comprehensive solution tools to overcome the biomass supply chain (BSC) planning challenges is critical for both academic research and industry. Therefore, the aim of this study is to conduct a systematic review of BSC modeling and optimization and identify future research directions. We reviewed 300 papers that have been published in the past 40 years on this topic to assess the various models of BSCs, their objective functions, solution approaches, and decision levels employed. Results show that researchers are motivated to use mixed integer programming models for BSC problems because of the complexities of nonlinear models, as well as the simplicity of the linear approaches. There is a lack of multi-objective optimization approaches to address the economic, social, and environmental issues simultaneously in BSC. Although factors such as the political regulation, governmental subsidy, impact of biomass and oil price and cost of raw material are uncertain, most studies formally treat only the supply and demand of biomass as uncertain parameters. It is highly recommended that an integrated and holistic model that consider all facilities in the whole BSC be developed and tested with real data. In addition, incorporating strategic, tactical, and operational decision levels in the model is suggested to address the challenges of incorporating day-to-day inventory control and fleet management issues.
65 citations
TL;DR: In this article, the effect of temperature and alkali catalyst on product distribution was investigated, and the results showed that the temperature had a negligible influence, whereas catalyst slightly improved the bio-crude yield and quality for both sub-supercritical conditions (350 and 400°C).
Abstract: With the rapid growth in population and urbanization, sustainable disposal of sewage sludge has become a prominent problem worldwide. Therefore, an adequate treatment is required to reduce the environmental impacts created from traditional methods such as incineration, landfill, etc. In this context, sewage sludge was liquefied hydrothermally under sub-supercritical conditions with and without catalyst (K2CO3). The effect of temperature and alkali catalyst on product distribution was investigated. Obtained results showed that the temperature had a negligible influence, whereas catalyst slightly improved the bio-crude yield and quality for both sub-supercritical conditions (350 and 400 °C). Bio-crude contained N-containing compounds, ketones, phenols, acids, and long-chain hydrocarbons. Carbon and nitrogen recoveries revealed that 58–67% of the carbon went into bio-crude, while the majority of the nitrogen was transferred to the aqueous phase. ICP-AES analysis indicated that approximately 80% of the heavy metals were concentrated in the solid phase. The leaching action of citric acid with sewage sludge not only removed 40% of ash content but also reduced 38% of the fat content.
59 citations
TL;DR: A review of the role of bioenergy within energy models is undertaken with a key objective of critiquing their performances in analysing bioenergy research questions, showing strong argument for using multiple models in parallel to build robust overall conclusions.
Abstract: Transition towards renewable low carbon energy is a fundamental element of climate change mitigation, energy from biomass technologies are targeted within many country's decarbonisation strategies. Decision makers globally face many challenges developing strategies to drive this transition; models are increasingly used to road-test policy interventions before their implemented. A Bioenergy Literature Database was developed of 124,285 papers published 2000–2018. These document an exponential rise in research focusing on biomass and bioenergy. On average 35.4% of papers apply modelling analyses, 99.5% of these use bespoke models rather than high profile Integrated Assessment Models (IAMs) or Energy System Models – although it is these high profile models that are widely used in policy development. A review of the role of bioenergy within energy models is undertaken with a key objective of critiquing their performances in analysing bioenergy research questions. IAMs are found to be widely applied to investigate the impact of bioenergy within wider energy and environmental systems, e.g. for reducing emissions. Energy System Models focus on bioenergy processes, technologies and feedstocks, although don't capture wider environmental, economic and social themes. Specialist Bioenergy Models offer methods for bespoke analyses of all bioenergy issues, their narrow system boundaries generate targeted outputs but wider effects such as land-use change may not be captured. Caution is required when interpreting modelling outputs, particularly when used to inform policy. It's not feasible to develop all-encompassing bioenergy models covering all nuances between systems, but there is strong argument for using multiple models in parallel to build robust overall conclusions.
TL;DR: In this article, the authors reported the conversion of palm fatty acid distillate (PFAD), a low-value side product of physical refining of crude palm oil, into green diesel using a solventless and hydrogen-free deoxygenation (DO) reaction using catalytic deoxgenation over solid acid catalysts.
Abstract: The utilization of non-edible and low-cost feedstock in bioenergy research is getting more attention in recent decades. Catalytic deoxygenation of fatty acids from waste oil feedstocks is a promising route to produce diesel-like hydrocarbons. Here we report the conversion of palm fatty acid distillate (PFAD), a low-value side product of physical refining of crude palm oil, into green diesel using a solventless and hydrogen-free deoxygenation (DO) reaction using catalytic deoxygenation over solid acid catalysts (Co/SBA-15, Ni/SBA-15, and Ni–Co/SBA-15) with total metal loadings of 5 wt%. Metal precursors (Ni, Co, Ni–Co) were doped on the mesostructured catalyst supporter, SBA-15 by wet impregnation. The catalysts were characterized by nitrogen adsorption-desorption isotherm analysis, X-ray diffraction, X-ray fluorescence, infrared spectroscopy, and high-resolution transmission electron microscopy with elemental mapping. The DO reaction was carried out in a semi-batch reactor with a catalyst loading of 10 wt% at 350 °C for 3 h. The use of both Ni/SBA-15 and Ni–Co/SBA-15 afforded products with high contents of liquid hydrocarbons (C8–C17) with yields of 85.8% and 88.1%, respectively, and selectivity for diesel-range hydrocarbons (C13–C17) above 85% were achieved. Cobalt seems to have a larger particle size, then associates with the carbon formation and introduces coke formation. It blocks some pores and deactivates the active sites of the catalyst, thus reducing the catalytic activity.
TL;DR: In this article, microwave dilute acid pretreatment of wheat and rye stillage in terms of the amount of sugars released, formation of fermentation inhibitors and their removal, and fermentation efficiency was evaluated.
Abstract: The main problem in the production of cellulosic ethanol is to ensure an efficient and cost-effective raw material pretreatment, guaranteeing a high degree of lignocellulose decomposition. Microwave radiation can be an alternative to conventional biomass heating, which in association with the use of dilute acid and a cellulolytic enzyme ensures a high degree of cellulose degradation. We evaluated the effectiveness of microwave dilute acid pretreatment of wheat and rye stillage in terms of the amount of sugars released, formation of fermentation inhibitors and their removal, and fermentation efficiency. Regardless of the type of stillage used, the highest glucose concentration after pretreatment (above 156 mg g−1 of DW) and the highest yield of cellulose hydrolysis after 24 h of the process (over 75%) were obtained using microwave power of 300 W, 15 min, 54 PSI. Fermentation of lignocellulosic hydrolysates obtained under the above-mentioned conditions ensured high ethanol concentrations of up to 20 g L−1 with full attenuation after just 48 h. Too intensive microwave treatment (152 PSI, 10 min) increased the concentration of sugar dehydration products which inhibited yeast fermentation activity and led to a lower ethanol yield. Detoxification with activated carbon reduced the toxic stress caused by the high concentration of HMF in hydrolysates. The application of microwaves is an interesting alternative to conventional barothermal methods. The possibility of an effective use of waste biomass of wheat/rye stillage for the production of cellulosic ethanol creates a prospect of integrating first and second generation ethanol production within one technological process.
TL;DR: In this paper, three types of metal sulfates (aluminum sulfate, aluminum potassium sulfate and ferric sulfate) were applied as flocculants to harvest microalgae Chlorella vulgaris biomass.
Abstract: Flocculation is regarded as an effective, convenient and promising means for microalgal harvesting of microalgal biomass. In this study three types of metal sulfates (aluminum sulfate, aluminum potassium sulfate and ferric sulfate) were applied as flocculants to harvest microalgae Chlorella vulgaris biomass. The optimal operating parameters such as dosage, rotation speed, flocculation time and sedimentation time during microalgal biomass harvesting were determined, and the effects of metal sulfate application as flocculants on lipid extraction were investigated. The results showed that the optimal dosage for the three flocculants to harvest microalgal biomass was identically 2.5 g L−1, and the optimal rotation speeds for coagulation and flocculation were 150 and 25 rpm, respectively, while the flocculation time of 10 min was found to be appropriate. The findings also suggested that metal residuals in flocculated biomass would affect lipid extraction, resulting in 5.9%, 4.4% and 3.3% reduction of lipid contents for aluminum sulfate, aluminum potassium sulfate and ferrous sulfate, respectively. The contribution of this study lies in the provision of the optimal operating parameters during the microalgal biomass flocculation, thus potentially offering the technical guidance for the harvesting of microalgal biomass using metal sulfates as flocculants in practice.
TL;DR: In this paper, a review of the effect of heterogeneous catalyst addition on the hydrothermal liquefaction of lignocellulosic biomass, looking specifically at the improvement in bio-crude yield and quality, is presented.
Abstract: The biomass conversion into more valuable fuels represents one of the most viable routes for the exploitation of this material. Hydrothermal liquefaction is currently considered one of the most efficient processes to convert wet biomass into a bio-crude, which however requires expensive upgrading treatments to be used as biofuel. The use of catalysts able to directly improve bio-crude yield and quality during the reaction is of fundamental importance to increase the overall process efficiency. Homogeneous alkaline catalysts are the most studied, but they are not recoverable at the end of the process and so cannot be reused. The use of heterogeneous catalysts allows to overcome this issue making the recovery and reuse possible, maintaining anyway high activity and selectivity in the bio-crude production. The aim of this review is to critically summarize the effect of heterogenous catalyst addition on the hydrothermal liquefaction of lignocellulosic biomass, looking specifically at the improvement in bio-crude yield and quality. On the basis of literature data about the effect of heterogeneous catalyst addition on bio-crude yield and quality in the hydrothermal liquefaction of lignocellulosic biomass, a common catalytic action was identified allowing to group the several catalysts into four classes (alkaline metal oxides, transition metals, lanthanides oxides and zeolites). The hydrodeoxygenation activity of the catalysts, their effect on bio-crude yield and quality and the operating conditions used are highlighted. The highest bio-crude yields are reported using transition metals and lanthanide oxides which are able to guarantee, at the same time, a high-quality bio-crude.
TL;DR: In this paper, the basic fuel characteristics, ash composition, the subsequent pyrolysis behavior and relevant reaction kinetic parameters of obtained hydrochar were evaluated, and the results indicated that co-hydrothermal treatment improved the fuel characteristics of hydrochar with high HHV and low N and S contents.
Abstract: Co-hydrothermal treatment is an effective approach to recovery the energy and fuels from organic matter in rice straw (RS) and sewage sludge (SS). In this study, the basic fuel characteristics, ash composition, the subsequent pyrolysis behavior and relevant reaction kinetic parameters of obtained hydrochar were evaluated. The results indicated that co-hydrothermal treatment improved the fuel characteristics of hydrochar with high HHV and low N and S contents. FTIR analysis indicated that the presence of the synergy between RS and SS during co-hydrothermal treatment that the organic acids from hydrolysis of hemicellulose promoted the degradation of N-containing functional groups. In addition, the ash composition analyses showed that the obtained hydrochar had high ash fusion temperature as a result of the high removal efficiency of alkali metals during co-hydrothermal treatment. Moreover, co-hydrothermal treatment can promote the pyrolysis reaction by reducing the activation energy with the synthetic effect of RS and SS during co-hydrothermal treatment process. In summary, co-hydrothermal treatment improved the physiochemical properties and promoted the pyrolysis behavior of obtained hydrochar from RS and SS.
TL;DR: In this paper, the effect of four variables (i.e., methanol to chicken fat oil, catalyst loading, reaction time, and temperature) on free fatty acid (FFA) conversion was studied via the one-variable-at-a-time method.
Abstract: Biodiesel, as an alternative fuel for petroleum-derived fuel, has gained significant attention from society In this research work, biodiesel is produced via simultaneous esterification and transesterification of chicken fat and skin oil (CFSO) over Ce supported sulfated activated carbon derived from coconut shell (ACcs-S) Details of a study on the effect of Ce concentrations in the range of 5–15 wt% were also investigated The results showed that 5 wt% Ce was an optimum concentration for the esterification and transesterification of CFSO with approximately 93% free fatty acid (FFA) conversion High FFA conversion by 5Ce/ACcs-S is attributed to it having a sufficient amount of acid-base and noticeable pore structures The effect of four variables (ie, methanol to chicken fat oil, catalyst loading, reaction time, and temperature) on the FFA conversion was studied via the one-variable–at-a-time method Optimum FFA conversion (93%) was achieved at a temperature of 90 °C, 12:1 MeOH to oil ratio, 3 wt % catalyst loading, and 1 h reaction time 5Ce/ACcs-S shows high chemical stability by maintaining the FFA conversion at up to 90% within five consecutive reaction cycles
TL;DR: In this paper, the potential of using chicken manure (CM) as a sole feedstock for renewable biogas production under anaerobic conditions before spreading the digested chicken manure biomass on the fields as an organic biofertilizer was determined.
Abstract: The objective of this work was to determine the potential of using chicken manure (CM) as a sole feedstock for renewable biogas production under anaerobic conditions before spreading the digested chicken manure biomass on the fields as an organic biofertilizer. The chicken manure samples from four different locations of Lithuania were analysed and compared in order to better understand the chemical composition of the locally generated biomass resource. The annual quantities of chicken manure produced were investigated allowing estimation of the biogas potential if such biomass was treated anaerobically. Laboratory biomethane potential (BMP) tests performed indicated the biogas potential of methane – 508 mL CH4 g−1 VS added and this result was compared to biogas yields obtained in full scale anaerobic digestion plant using manure as a core substrate. Fermentation process data analysis of anaerobic digestion performance indicates that the system is able to adapt even if the same operational conditions, such as organic loading rate and retention time are applied. Once adapted, the performance of biogas plant fermenter was able to deliver 93% of chicken manure biogas potential with an OLR of 3.14 kg VS L−1d−1 and TAN concentration of 5.5 g L−1. The results indicated that it is possible to digest chicken manure as a stand-alone feedstock if ammonium concentration was carefully controlled via optimized fresh water dilution process.
TL;DR: In this article, date palm mixture wastes (DTM) and date seed (DS) biomass were used as starting materials in the production of bio-oil by pyrolysis.
Abstract: The prevailing trends in global energy consumption and the rapid depletion of fossil fuel present an urgent need for alternative fuels, particularly from renewable sources of biomass. In this study, date palm tree mixture wastes (DTM) and date seed (DS) biomass were used as starting materials in the production of bio-oil by pyrolysis. The yields of the pyrolysis oils from DTM and DS were optimized by tuning the experimental parameters. The DS provided a maximum yield of 68 wt% obtained from 30 min of pyrolysis with a biomass loading of 200 g, fluidizing gas flow rate of 10 mL min−1, and at a temperature of 500 °C. In addition, we evaluated the impact of the aging process of the obtained pyrolysis oils. The produced pyrolysis oils (freshly made) were aged for 15 and 30 days at room temperature under closed conditions. All the feedstock biomass were subjected to proximate and ultimate analysis. The TG-DTA results indicated that both biomasses were richer in cellulose and hemicellulose contents than in lignin content. The FT-IR and GC/MS analyses of the fresh and aged oil samples demonstrated the outstanding characteristics of the DS derived bio-oil for use as a bio-fuel. The variation in the chemical composition of the fresh and aged pyrolysis oils are completely described and presented elaborately. This study demonstrates the significance of and a new functionality for the date palm industry to process date palm wastes, particularly the DS as a rich biomass source for the production of bio-fuel.
TL;DR: In this paper, a new composite, biochar derived from pecan nutshell with ZnO (biochar-ZnO) was prepared, in order to obtain a potential catalyst for degradation of Reactive Red 97 (RR97) from aqueous solutions.
Abstract: A new composite, biochar derived from pecan nutshell with ZnO (biochar-ZnO) was prepared, in order to obtain a potential catalyst for degradation of Reactive Red 97 (RR97) from aqueous solutions. Composites with different ratio of ZnO supported in the biochar were produced using mechanical mixing and pyrolysis in a reducing atmosphere from N2 at 650 °C. The catalyst composites were characterized by XRD, FT-IR, UV–Vis, FE-SEM, EDS, and BET. The composites presented higher activity compared to ZnO pure. The composite with greater amount of ZnO supported in the biochar (N20Z) degraded 100% of RR97 in only 67 min (30 min biosorption + 37 min photocatalysis). This remarkable performance could be associated to decrease of electron-hole recombination rate, reducing the band gap energy, and increasing the surface area of the photocatalyst. The recycling of the composite N20Z indicated that it can be used for more than 9 cycle and be easily removed from solution. Radical scavenger tests indicated that •OH and h+ were the predominant active species involved on the degradation of RR97. The proposed mechanism indicated that RR97 molecule degrades into lower-mass intermediates Therefore, the composite presented intrinsic properties that become it a promising catalyst for removal of emerging contaminant in water.
TL;DR: It is suggested that microalgal biomass derived VFAs could be converted into yeast lipid suitable as feedstock in the chemical (including biofuel) industry.
Abstract: Using residual material instead of sugars as substrate for oleaginous microorganisms is a promising approach that may reduce the production costs of microbial lipid. In this study, five oleaginous yeasts were screened for their ability to grow and produce lipid utilizing volatile fatty acids (VFAs), generated from anaerobic fermentation of microalgal biomass, as the only carbon and energy source. Yeasts growth and lipid accumulation capacity at three VFAs concentrations (i.e. 5, 10 and 15 g L−1) were evaluated. Regardless of VFAs concentration four of the five strains were able to grow in digestates reaching biomass yields from VFAs between 0.22 and 0.37 g g−1. The highest lipid content in dry biomass was observed in Cutaneotrichosporon curvatum and Cyberlindnera saturnus (36.9 and 33.9% on dry biomass, respectively) corresponding to lipid yields from VFAs of 0.11 and 0.13 g g−1, respectively. Oleic, palmitic and linoleic acids were the major fatty acids, accounting for more than 70% of the fatty acids contained in total yeast lipids, profile similar to that of common vegetable oils. The above findings suggest that microalgal biomass derived VFAs could be converted into yeast lipid suitable as feedstock in the chemical (including biofuel) industry.
TL;DR: Deep eutectic solvents (DESs) as discussed by the authors have been used in many applications and processes such as biorefinery, lignocellulose dissolution, bioactive compound extraction and electrochemical applications.
Abstract: Deep eutectic solvents (DESs) are green solvents that are developing rapidly, used in many types of applications as well as fundamental investigations. The physicochemical properties of DESs are one of the most important factors which led to their increased interest in science and technology. DESs are thermally and chemically stable, non-flammable and have a negligible vapor pressure. Furthermore, most of the newly formulated DESs are liquids at room temperature. DESs are more economical and less expensive compared to ionic liquids. DESs are frequently prepared from renewable and non-toxic precursors, in addition, there are wide selections of biocompatible and biodegradable DESs. Hence, DESs have been used in many applications and processes such as biorefinery, lignocellulose dissolution, bioactive compound extraction and electrochemical applications. In this review, an update of the application of DESs in biomass processing as renewable sources is presented. This review aims to cover as much as possible the ongoing research and applications of DES and invite opinions to broaden the applications of DESs, rather than concentrating on the physicochemical fundamentals of new DESs. The future of these solvents is bright but require further investigations and efforts for a better understanding and future for sustainable resources.
TL;DR: In this article, the authors highlight research findings from authors in relation to factors influencing effective degradation of lignin based biomass in other to ascertain the best possible strategies to scale up the process.
Abstract: Since the first use of anaerobic digestion technology to generate biogas in 1895 to power street lights in Britain and also as a Municipal Solid Waste Management technique in the US in 1939, significant advances have been developed to optimise the process in a sustainable manner. In practice, optimising anaerobic digesters to increase biogas production dependent on a balanced pH (neutral), tolerable volatile fatty acids and alkalinity levels by anaerobic bacteria. Others include maintaining suitable temperature regime, providing suitable organic loading rate to prevent noxious conditions, well-balanced carbon to nitrogen ratio to limit ammonia build-up and appropriate choice of substrates. In terms of biomass, lignocellulose substrates constitute the most abundant bio-resource. This resource however requires modification of the chemistry of the structure to improve its biodegradation, biogas production and effluent quality. There have been attempts by most researchers to improve lignocellulose biomass utilization in anaerobic digesters through delignification to prevent non-productive binding of bacteria as well as reduce the crystalline in cellulose with the aim of making the holocellulose fractions bioavailable. However, none of the techniques so far applied for the purpose of optimising biogas production has attained the maximum theoretical biogas yield of 120,000–650,000 L t−1. Techniques frequently applied include among others; pretreatment (chemical, biological, physical or their combinations), co-digestion, application of inoculum or bio-augmentation, and supplementing anaerobic digesters with micronutrients and nanoparticles. This review thus highlights research findings from authors in relation to factors influencing effective degradation of lignin based biomass in other to ascertain the best possible strategies to scale up the process.
TL;DR: In this paper, slow pyrolysis (SP) and hydrothermal carbonization (HTC) were compared and framed into the International guidelines for soil improvers/amendments in agriculture.
Abstract: Carbonization of anaerobic digestion digestate from an Italian plant fed with local feedstock was investigated by slow pyrolysis (SP) and hydrothermal carbonization (HTC); the properties of pyrochar and hydrochar were compared and framed into the International guidelines for soil improvers/amendments in agriculture Experiments were carried out in newly designed thermochemical conversion systems, with the aim of generating the original data necessary for future scale-up and for evaluating the characteristics of the product versus existing biochar market standards SP was carried out in a paddle pyrolysis reactor at 500 °C for 1 h, while several HTC experiments were performed in a custom-made test bench, investigating the influence of temperature (200–250 °C) and time (05–3 h) on hydrochar properties Both processes were run in batch mode SP showed lower char yield (331%w/w db), while the maximum hydrochar yield was obtained at 200°C-05 h (726%w/w db) Most char properties fall within the thresholds set by biochar standards The Carbon content was slightly higher for pyrochar (643%w/w db) than hydrochar (629%w/w db at 250°C-3 h) The specific area was rather low for both chars; however, pyrochar area (2310 m2 g−1), was one order of magnitude higher than hydrochar The ash content of pyrochar was nearly twice the hydrochar, while O/C and H/C ratio of the former were lower The HTC aqueous phase was also characterized in terms of inorganics concentration and organic composition In average, the concentration of the former increased with reaction severity: more than 50 compounds were identified and 20 quantified Acetic acid was the most abundant (up to 326 g l−1)
TL;DR: In this paper, a two-stage approach was proposed for the upgrading of highly nitrogenous biocrudes derived from the hydrothermal liquefaction (HTL) of primary sewage sludge and microalga Spirulina biomass.
Abstract: Effective catalytic hydrotreatment of highly nitrogenous biocrudes derived from the hydrothermal liquefaction (HTL) of primary sewage sludge and microalga Spirulina biomass was explored. A critical issue is the lack of thermal stability of raw HTL biocrudes at the severe conditions (~400 °C) required for hydrodenitrogenation. This fact suggests the need for a two-stage approach, involving a first low-temperature stabilization stage followed by another one operated at higher temperature. In this study, DSC was successfully used to indicate the thermal stability of both biocrudes. During hydrotreating, it was observed that complete deoxygenation was already achieved in the first stage at 350 °C, with limited coke formation. Moreover, after second stage up to 92% denitrogenation associated with the higher hydrogen consumption (39.9 g kg −1 for Spirulina and 36.9 g kg −1 for sewage sludge) was obtained for both biocrudes. Consequently, comparable oil yields but significantly less coke yields were recorded during two-stage upgrading (1.0% for Spirulina and 0.7% for sewage sludge), compared to direct processing at 400 °C (9.1% for Spirulina and 3.4% for sewage sludge). In addition, the properties of the upgraded oils were enhanced by increasing the temperature in the first stage (310 °C, 330 °C and 350 °C respectively). Finally, the results indicated that remarkable drop-in fuel properties were obtained, with respect to heteroatom (O and N) removal, HHV, and H/C ratio during the two-stage hydrotreatment. Two-stage hydrotreating is therefore proposed as a successful approach for the upgrading of HTL biocrudes with high nitrogen content.
TL;DR: In this paper, the effect of addition of Ca- and Mg-saturated resin and phosphate-laden biochar on single-stage hybrid dark-photo hydrogen fermentation from food waste was investigated.
Abstract: Bio-hydrogen production from organic wastes is considered as one of the most promising alternatives for sustainable, green energy production. In this study, the effect of addition of Ca- and Mg-saturated resin and phosphate-laden biochar on single-stage hybrid dark-photo hydrogen fermentation from food waste was investigated. In the first step, fermentation was performed using different amounts of Ca- and Mg-saturated resin ranging from 2.5 to 20 g l-1 to analyze the effect of released calcium and magnesium on both the H2 production rate and the system pH. The addition of 5 g l-1 saturated resin resulted in an increase of hydrogen yield from 101.60 ± 2.4 to 164.4 ± 2.6 ml H2g−1 VS, and at the same time it prevented pH drop and improved bacterial function. In the second step, 5 g l-1 saturated resin combined with various amounts of phosphate-laden biochar were added to the reactor. The maximum accumulated hydrogen production (3130 ± 16.8 ml) and hydrogen yield (197.15 ± 2.9 mlg−1VS) was observed when 5 g l-1 resin and 0.5 g l-1 biochar was used. This corresponds to 94% increase in the yield compared with the control. The analysis of the fermentation products indicated that butyrate and acetate were the major by-products during hydrogen production. Moreover, the optimum concentrations of resin and biochar served to facilitate substrate degradation and shorten the lag phase from 8.19 ± 0.4 to 4.79 ± 0.5 h. Thus, the application of Ca- and Mg-saturated resin and phosphate-laden biochar in a single-stage hybrid dark-photo fermentation process enhanced the efficiency of the conversion of organic waste to hydrogen while maintaining the stability of the process.
TL;DR: A detailed overview of the main strategies undertaken for controlling over-acidification in anaerobic digestion can be found in this paper, as well as a useful source of knowledge for future research and further development of biogas technology worldwide.
Abstract: Over the years, anaerobic digestion (AD) technology has earned considerable attention because in addition to treating organic wastes, it can produce biogas as a viable substitute for conventional fossil fuels. However, the widespread application of AD is restricted by concerns about the reduced efficiency and profitability of the process due to a variety of inhibitors. The excessive acidification of AD processes due to the accumulation of volatile fatty acids (VFAs) is one of the most commonly encountered drawbacks in AD, which can lead to instability and, even in some cases, the failure of the entire process. Therefore, many efforts have been made so far to tackle this problem and maximise AD biogas output. The present work aims to provide a detailed overview of the main strategies undertaken for controlling over-acidification in AD as a useful source of knowledge for future research and further development of biogas technology worldwide.
TL;DR: In this paper, the influence of Granular Activated Carbon (GAC) on anaerobic co-digestion of brewery waste activated sludge and food waste for the production of methane were investigated by analysing the VFA production, ammonia concentration, pH, oxidation reduction potential, and electrical conductivity.
Abstract: Granular activated carbon (GAC) as an economic and robust amorphous material could facilitate the syntrophic metabolism of acetogenesis and methanogenesis during anaerobic digestion of post-consumer substrates. In this study, influences of supplementing GAC on anaerobic co-digestion of brewery waste activated sludge and food waste for the production of methane were investigated by analysing the VFA production, ammonia concentration, pH, oxidation reduction potential, and electrical conductivity. Our data showed that a 45% increase in methane production with adding 1.5% (g/g) GAC was achieved. The maximum amount of 478 mL CH4/g volatile solids (VS)added was recorded along with 64% VS removal efficiency under a high ammonia concentration of 1420 mg L−1. Moreover, the analysis of scanning electron microscopy exhibited the formation of biofilms with the supplement of GAC. Our results elucidate that GAC evidently enriched activities of hydrolysis and acetogenesis and enhanced the electron transfer efficiency for methanogenesis, which improved the production of methane significantly. Our results also demonstrate that the supplementation of GAC is an efficient method for the enhancement of biogas production from post-consumer wastes.
TL;DR: In this article, the application of sorption-enhanced steam gasification to sewage sludge treatment is experimentally investigated to generate hydrogen-rich syngas in a fixed bed setup.
Abstract: Thermal conversion is an effective non-traditional method for sewage sludge disposal. Herein, the application of sorption-enhanced steam gasification to sewage sludge treatment is experimentally investigated to generate hydrogen-rich syngas in a fixed bed setup. The main aim was to determine the optimal conditions and suitable sorbents for this process. CaO was selected as the sorbent, and different CaO sorbents were prepared via the sol-gel method. Al2O3, La2O3, and ZrO2 were used as support materials for CaO to enhance the sorbent activity and stability. The CO2 capture capacities and stabilities of the sorbents over multiple cycles were examined. Additionally, different metal additives including CoO, MgO, and CeO2 were combined with the sorbent to increase the hydrogen mole fraction and gas yield. The integration of the support material increased the stability of the sorbents over multiple cycles. High temperature increased the syngas yield and cold gas efficiency but decreased the hydrogen mole fraction. In comparison to CaO–La and CaO–Zr, CaO–Al afforded a higher hydrogen mole fraction and yield. Moreover, as Al2O3 is cheaper than La2O3 and ZrO2, it was selected as the most suitable support material for CaO, considering both its performance and cost. Transition metal Co was also investigated as a catalyst for gasification. A high Co loading ratio improved the hydrogen yield and cold gas efficiency but decreased the hydrogen mole fraction. These findings suggest that the CaO sorption-enhanced gasification to produce hydrogen-rich syngas is an appropriate method for sewage sludge disposal.
TL;DR: In this paper, beechwood and pine were pretreated with a mild oxidative organosolv process to produce cellulose-rich solid fractions, which were tested for their ability to support the growth and high lactic acid productivity of Lactobacillus delbrueckii subsp. bulgaricus (ATCC® 11842).
Abstract: Lactic acid bioconversion processes have numerous advantages over the chemical synthesis route, not only due to the high-titer yield of the final product with great optical purity, but also due to the possibility of utilizing lignocellulosic biomass feedstocks as carbon source in an economic and environmentally friendly way. In the present study, beechwood and pine were pretreated with a novel mild oxidative organosolv process to produce cellulose-rich solid fractions, which were tested for their ability to support the growth and high lactic acid productivity of Lactobacillus delbrueckii subsp. bulgaricus (ATCC® 11842). We employed a simultaneous saccharification and fermentation (SSF) strategy in batch cultures with 9% w v−1 solids loading. The results for beechwood showed the highest production of 62 g L−1 lactic acid after 72 h of incubation, corresponding to a yield of 0.69 g g−1 of biomass (82.7% of the theoretical maximum yield) and a productivity of 0.86 g L−1 h−1. In the case of pine, the productivity was lower at 0.51 g L−1 h−1, leading to accumulation of 36.4 g L−1 lactic acid, corresponding to a yield of 0.40 g g−1 of biomass (41.4% of the theoretical maximum yield). Our study suggests that L. delbrueckii subsp. bulgaricus is an efficient lactic acid bacterial strain for the production of optically pure d -lactic acid from non-edible, organosolv pretreated hardwood and softwood biomass for the synthesis of bio-based plastics and other products.