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A two-stage thermophilic hydrogen fermentation and mesophilic methane production from paper sludge was successfully explored. The maximum hydrogen and methane potential were 0.165 L/g VS and 0.376 L/g CODeffluent, respectively with Clostridium thermocellum augmentation. 63 L of hydrogen and 122 L of methane were recovered from 1 kg Paper sludge (PS, dry weight) with an energy yield of 4.5 MJ/kg PS, 50% higher compared to the single-stage anaerobic digestion (94 L CH4, 3.0 MJ/kg PS). The bacterial community of second-stage process was dominated by genus Propionispira, Mesotoga and Aminobecterium with stability, whereas the bacterial structure in single-stage process presented dynamic changes where genus Acetivibrio and Fibrobacter played an indispensable role. However, Genus Methanosaeta, Methanosarcina, Methanobacterium and Methanospirillum existed stably and predominantly in the archaeal community of single-stage and second-stage processes. The present study suggests the potential application of the established two-stage process in valorization of low-value waste biomass.

This paper describes the effect of the ash content in biomass on the distribution of pyrolysis products and the miscibility of bio-oil in diesel. Ash content of loblolly pine wood (0.5 wt %, 1.1 wt %, and 1.5 wt %) was systematically varied by impregnating the wood with potassium carbonate solution. Variation in the ash content did not create a significant change in the chemical composition of the impregnated biomass. However, the response to a variety of thermal treatments changed significantly. The volatile matter content decreased from 88.3% to 78.2%, while the bio-oil yield declined from 45.7% to 29.9% as the ash content increased. Although the total organic yield decreased with increased biomass ash content, the total concentration of phenolic monomers increased from 2.8 mg/g to 20.2 mg/g, and bio-oil miscibility with a commercial diesel fuel increased from 6.7% to 13.4% based on wet bio-oil. The miscibility of guaiacol and 4-methyl guaiacol in diesel was higher than that of catechol, due to the lower polar and hydrogen bonding contribution. Test in a diesel engine showed a simultaneous reduction of HC and NOx emissions using diesel extracts.

The aim of the present paper is to compare the combustion results of two solid biofuels suitable for industrial applications: olive tree pruning (OTP) pellets and sunflower husk (SH) pellets. The former derives from the thin prunings, along with the leaves, whereas the latter derives as a byproduct from the sunflower oil extraction industries. The combustion was performed in operating conditions at two industrial fixed bed biomass boilers (1.16 MWth capacity each) with a common flue gas stack used for greenhouse heating. Combustion tests were performed at the industrial boiler for two consecutive days. During the first day, the OTP pellets were combusted and monitored for emissions, whereas in the second day the reference fuel that is normally used in the plant (SH pellets) was monitored. While combusting OTP pellets, the boiler’s performance was found to exhibit a slightly worse, leading to a decrease of 3.5% points of the boiler efficiency compared to SH pellets. Lower emissions of CO and NOx were also observed for OTP pellets, while the ash formation exhibited signs of reduced slagging. Dust emissions were high for both fuels, indicating that particle emission abatement equipment should be installed at the facility.

Supercritical water gasification (SCWG) can achieve efficient utilization of solid wastes, including depolymerization slag, biomass, municipal sludge, and others, and can produce hydrogen-rich gas. But phenolic intermediates produced during the gasification process are difficult to be gasified. It restricted the increase of conversion efficiency. Thus, in this paper, two effective schemes were put forward to raise the gasification efficiency of depolymerization slag. The first one was to add oxidants to promote the decomposition of hydrolysates. Carbon gasification efficiency (CGE) and hydrogen gasification efficiency (HGE) reached 71% and 74% respectively at the time of 1200 s. They raised by 41.6% and 60.5%, separately compared with non-oxidants addition. The second one was to raise the reaction temperature since a higher temperature can accelerate the reaction rate and obtain a high hydrogen yield. The results showed that hydrogen percentage increased by 32.82% and CGE and HGE increased by 35.39% and 219.85%, respectively when the reaction temperature raised by 200 °C. Based on the obtained gasification mechanism, the catalytic gasification.

Hydrothermal carbonization (HTC) is a promising thermochemical treatment technique for converting wet biomass into value-added products, but the hydrochar properties of different biomass differ significantly due to the diversity of biomass feedstock and the complexity of HTC reactions. In this study, model biomass samples prepared from five representative components were carbonized hydrothermally under a typical condition of 220 °C, and mathematical models basing on the component recipes were developed to predict the mass yield (MY), higher heating value, energy yield (EY), and equilibrium moisture content of the hydrochar. Synergistic effects occurred between different components in increasing MY and EY, especially when the lipid existed, because the hydrolysed lipid was re-adsorbed on the hydrochar surface or interactively polymerized with other components. All the models showed R2 values above 89%, moreover, validation experiments using additional model biomass showed that the relative errors were less than 8% between the prediction and experiment values, suggesting the prediction models obtained from this study can be used to assess the hydrochar characteristics and bioenergy generation potential based on biomass components.

The impact of different nitrogen sources on the microalga, Chlorella vulgaris, was studied in a newly developed microalgal-bacterial photobioreactor via a dual nutrient heterogeneity mode. The mechanisms of nitrogen transformation and valorisation were unveiled, and subsequently, optimized via dual nutrient heterogeneity feeding modes comprising of various NH4+-N and NO3−-N concentrations. The nitrogen-assimilation mechanism from the microalgal-bacterial consortium was found to reduce microalgal growth inhibition, stemming at high NH4+-N concentrations. Accordingly, the total nitrogen removal efficiency was enhanced from 40.91% to 96.38% accompanied with maximum microalgal biomass production of up to 792 mg/L at a balanced or higher NH4+-N loading from mixed nitrogen environment. The harvested microalgal biomass contained high lipid accumulation of approximately 30% when fed with optimum NH4+-N and NO3−-N loadings at 60 and 58 mg/d, respectively. At this mixed nitrogen species loadings, high unsaturated fatty acid methyl esters (FAME) were attained. Indeed, the major FAME species (97%–100%) fell within the C16-18 range, signifying biodiesel characteristics conformity to the requirements for quality biodiesel application. Therefore, the dual heterogeneity modes of balanced NH4+-N and NO3−-N loadings into photobioreactor could offer effective microalgal nitrogen assimilation for sustainable wastewater treatment and microalgae-based biodiesel production simultaneously.

This work evaluated the influence of superheated water steam injection in an autothermal 80 kWth pilot-scale bubbling fluidized bed during biomass direct (air) gasification, focusing on the effect of steam to biomass ratio in the producer gas composition and gasification efficiency parameters. The process was also evaluated in an externally heated 3 kWth bench-scale bubbling fluidized bed and simulated in a thermodynamic equilibrium model. For low-density biomass, the steam injection resulted in a producer gas with higher H2 concentration and H2/CO molar ratio, although with lower energy content, and in a decrease of the process efficiency. Thus, steam injection promoted a trade-off between parameters, that can be associated with a higher occurrence of the water-gas shift reaction. For high-density biomass, along with an increase of H2 concentration and H2/CO molar ratio, steam injection promoted an increase of the producer gas energy content and process efficiency, which can be justified by a higher char accumulation in the reactor bed and consequent higher occurrence of char-steam reforming reactions. Therefore, steam injection shows high potential to improve the producer gas quality from high-density biomass air gasification, however, for low-density biomass, it shows limited potential and should only be used to adjust H2/CO molar ratio.

This study addresses the development of a non-sterile heterotrophic microalgae process, mainly using Scenedesmus sp., for the treatment of wastewater with high concentration of organic matter and biomass production. Urban and swine wastewaters were used as source of organic carbon. A C:N ratio of 3.4:1 provided a maximum biomass concentration of 1.22 g/L on day 13 using autotrophic conditions. Using the same C:N ratio under dark conditions a maximum biomass concentration of 1.1 g/L was measured on day 14. Heterotrophic growth removed 81.6% of the total organic carbon (TOC), 83.7% of the chemical oxygen demand (COD) and 85.1% of the biochemical oxygen demand (BOD5). Results indicated that the application of a non-sterile heterotrophic process contributed to the removal of organic matter with the advantage of biomass generation, and although more detailed analysis is needed, it is likely due to the microalgae-bacteria association .

Agricultural residues (e.g. corn stover (CS)) representing a huge lignocellulosic biomass waste are regarded as a promising renewable resource that can be converted to fuels and chemicals via biochemical route. Nevertheless, the unfavorable properties, such as low bulk density, contamination by microorganisms, fluffy and thereby difficult to handle, cause huge problems for biomass logistics and biomass conversion. Furthermore, traditional biomass pretreatment methods often use severe conditions, consume much energy, difficult to scale up and generate a feedstock with many toxic degradation products that inhibit fermentation. In this study, we developed a novel, low-cost and easy-to-implement pretreatment method: “Densifying Lignocellulosic biomass with acidic Chemicals (DLC)” on CS. The DLC-CS owning a uniform shape showed a bulk density 4 times higher compared to loose CS and was highly resistant to microbial contamination, which greatly facilitates biomass handling, transportation and storage. DLC-CS after regular steam autoclave treatment at 121 ○C exhibited high enzymatic digestibility and much higher fermentability compared to traditional dilute acid pretreatment. An ethanol titer as high as 68.1 g/L was achieved without washing or detoxification of the pretreated biomass. The superior performances of DLC for biomass logistics and biomass conversion render it very promising for industrial use.

Brazilian charcoal is produced from planted eucalyptus forest wood in traditional batch reactors. The ordinary technology applied in Brazil does not use pyrolysis waste gases, which leads to the loss of 30% of wood energy and decreases air quality. This study evaluated the synchronous use of industrial batch kilns, waste gas burning, and energy recovery to produce electricity. Three scenarios were analyzed: (S1) Eucalyptus charcoal production without gas burning (Base Scenario); (S2) with gas burning; and (S3) with gas burning and electricity generation. Since a eucalyptus forest can fix carbon into its biomass through photosynthesis and finally into charcoal, S1 was able to reduce 3402.5 kg of CO2-eq per Mg of charcoal produced, and S2 reduced 6453.1 kg of CO2-eq due to waste gas methane burning. Electricity production is environmentally positive for all evaluated environmental indicators thanks to gas pollutants destruction and renewable energy generation. For S1, a ratio difference of 6.3 was found between the output of renewable energy and fossil energy input during the charcoal life cycle. For a combined production of charcoal and electricity (S3), a ratio difference of 6.9 was found. Photochemical oxidation was the main impact which can be significantly reduced by adopting gas flaring.

Anaerobic biotechnology has been widely used for swine wastewater (SWW) treatment. However, its organic loading rate (OLR) is far lower than expected, mainly because of the low rate of hydrolysis. In this study, the comparative process performance and efficiency of an up-flow anaerobic sludge blanket (UASB) reactor (R1) and an up-flow microaerobic sludge blanket (UMSB) reactor (R2) were evaluated for SWW treatment, operating for 264 days under higher OLRs and lower hydraulic retention times than those found in the literature. The R2 was subjected to the three different air doses: 0.09 (stage I), 0.17 (stage II), and 0.25 (stage III) LO2 Lfeed−1 d−1 aiming at enhancing the hydrolysis step of the anaerobic digestion (AD). The overall results showed that 0.17 LO2 Lfeed−1 d−1 was the best experimental condition evaluated, which provided volatile suspended solids, total chemical oxygen demand, and particulate chemical oxygen demand removal efficiencies of 85.0 ± 1.9%, 83.8 ± 2.5%, and 82.1 ± 4.8%, respectively. This performance was due to the higher organic matter hydrolysis, resulting in higher methane production. Therefore, the UMSB reactor treatment was demonstrated to be a feasible alternative for SWW, although some strategies to control biomass washout must be investigated.

Electrochemical pretreatment is considered a promising technique to reduce recalcitrance nature of lignocellulosic biomass. Yet, a comprehensive knowledge on the performance of alkaline reagents in electrochemical pretreatment and the associated environmental impacts are at an early stage. The present study investigated and compared the effect of electrochemical pretreatment by using NaOH reagent (EN) and electrochemical pretreatment by using Ca(OH)2 reagent (EC). The results showed that, both pretreatment techniques elicited the structural breakdown of the biomass, as evidenced by compositional changes, supernatant properties, SEM, FTIR, and XRD analyses. The batch anaerobic digestion results revealed that the improvement in methane production was highest for the EC pretreatment (434 mL/gVS) followed by the EN pretreatment (346 mL/gVS) and the untreated yard waste (245 mL/gVS). The Modified Gompertz model showed the best fit for untreated and pretreated yard waste. The results of economic analysis confirmed the highest net profit of 8922 rupees (US$ 119.29) for EC pretreatment. The findings of life cycle analysis revealed that the net environmental performance considering the inventory used and the limitations of the system boundary was highest for EC pretreatment followed by EN pretreatment and untreated condition.

The aim of this study is to evaluate the most suitable operating conditions for anaerobic co-digestion processes with high replacement rates (64% on average) of dedicated crops (silage of maize and triticale) with residual biomass, represented by a mixture of whey (scotta), pitted olive pomace, olive mill wastewater, and sheep manure. Experimental trials were first carried out at pilot plant scale and then at industrial plant scale. Univariate and multivariate statistical analysis demonstrates that almost 70% of the dedicated crops, ordinarily used in industrial scale anaerobic digestion plants, can be replaced by a mixture of residual biomass, available on the territory, without a reduction in performance. Compared to the industrial plant, the pilot plant shows much higher values of biogas production rate and specific production rates for both biogas (about 0.64–0.86 Nm3/kgVS vs 0.35 Nm3/kgVS) and methane (about 0.30–0.43 Nm3/kgVS vs 0.20 Nm3/kgVS). With reference to a case-study of the Sardinia island, the use of all available biomass residues in existing and new anaerobic digestion plants can provide a production of more than 160 million Nm3/y of biogas, that corresponds to about 87 millions Nm3/y of biomethane, that is about 20% of the forecasted natural gas demand of the island.

Trona, a low-cost and commonly available evaporite mineral was investigated as a novel pre-treatment material for enhancing the methane yield during the anaerobic digestion (AD) of grass silages. The results from BMP tests indicated that reactors fed with hot water pretreated Guinea grass and reactors fed with the grass pretreated with 5 mg/L and 10 mg/L Trona achieved maximum methane production rates (Umax) of 28.0, 56.4 and 58 N mL CH4/d, respectively, signifying an increase in Umax from Trona-pretreated grass by 201% and 207%, compared to the control reactors. The degradation yields in the three pairs of reactors were 68%, 79% and 75%, respectively. Kinetic modelling showed that the substrate hydrolysis rates (kh-values) were 0.32, 0.35 and 0.34 d−1, respectively, indicating that Trona-pretreatment enhanced the hydrolysis of Guinea grass. A step-change in temperature significantly affected methane yield. Kinetic models also satisfactorily predicted methane productivity in the reactors with >92% prediction accuracy. These results demonstrate that Trona pretreatment and mesophilic temperatures provided accelerated hydrolysis of biomass contents which enhanced methane production.

Beet pulp is an extremely very wet organic waste derived from sugar production. It can be utilized for energy purposes, e.g. biogas production or as very valuable fodder for animals, mainly horses. The high moisture content (80%) in beet pulp makes it an adequate feedstock for the hydrothermal carbonization process. Therefore, this study is focussed on the hydrothermal carbonization of beet pulp. The following parameters were studied: temperatures of 180, 200, and 220 °C through 1, 2, 3, and 4 h of residence time. The optimal conditions of the process were determined (220 °C and 1 h), based on the physical and chemical properties of solid product hydrochar. The ultimate and proximate analyses, high heating value, energy and mass yields, and energy densification ratio were investigated. The obtained hydrochars were of a coal-like solid biofuel, with high heating values much higher than raw feedstock (c.a. 150% higher). The combustion performance and kinetics of hydrochar based on TGA were determined, indicating better combustion. Moreover, the fibre analysis of hydrochar, supported by infrared spectra and scanning microscope analysis confirmed the changes in its structure. Concluding, organic waste, beet pulp, is of great potential as an energy source using the hydrothermal pretreatment process.

Made available in DSpace on 2022-04-29T08:30:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Suomen Akatemia This work presents a technical analysis of an Integrated Biomass Direct Gasification/Gas Turbine (BIG-GT) technology within a sugarcane industry to produce electricity and thermal energy (process heat) using bagasse as fuel. Four possible configurations for the implementation of this technology were considered. A sensitivity analysis was made to assess the risks and the uncertainty level for each proposed solution. The results indicated that with the BIG-GT implementation the power generation efficiency increases for all the studied configurations as compared to the conventional system (η = 14.3%). For the configurations I, II, and III the efficiency increase was 9.1%, 11.0% and 12.6%, respectively. However, to support these configurations of the system, the fuel (bagasse) consumption is increased beyond the production capacity of the mill, and the additional amount of bagasse must be acquired to other mills. On the other hand, in configuration IV it is only considered the gasification of the bagasse produced in the mill, being the additional needs of thermal energy for the industrial process supplemented through the combustion of other biomass types (sugarcane straw produced in the mill plantations) in a Heat Recovery Steam Generator. In configuration IV, the electricity generation efficiency is only 5.9% higher than the conventional cycle, this efficiency is getting without the need for an external supply of bagasse. Ultimately, the sensitivity analysis showed that the plant's energy performance with the implementation of BIG-GT technology is particularly sensitive to variations related to the gasifier's efficiency. UNESP-Sao Paulo State University Faculty of Engineering Campus of Guaratinguetá Bioenergy Research Institute (IPBEN-UNESP) Laboratory of Energy Systems Optimization (LOSE), Av. Dr. Ariberto Pereirada Cunha, 333 Portal Das Colinas Guaratinguetá University of Oriente Efficiency Energy Study Center (Faculty of Mechanical Engineering) Julio Antonio Mella Headquarters, Ave de Las Américas y Casero Department of Environment and Planning - Centre for Environmental and Marine Studies (CESAM) University of Aveiro Campus Universitário de Santiago Polytechnic Institute of Portalegre Instituto Superior Técnico University of Lisbon UNESP-Sao Paulo State University Faculty of Engineering Campus of Guaratinguetá Bioenergy Research Institute (IPBEN-UNESP) Laboratory of Energy Systems Optimization (LOSE), Av. Dr. Ariberto Pereirada Cunha, 333 Portal Das Colinas Guaratinguetá Suomen Akatemia: 320229

Anaerobic co-digestion of waste activated sludge with wheat straw has been applied in this study. Four novel two-dimensional mathematical models (TDMMs) along with an artificial neural network (ANN) have been used to simulate and predict the biogas production via anaerobic co-digestion process. In addition, a proposed moth flame optimization (MFO) technique is used to identify the optimal structure of the proposed multilayer feedforward neural network (MFFNN) to predict the produced biogas, then, a comparison is conducted based on the results obtained from both TDMMs and ANN. The experimental results demonstrated that the co-digestion at 7% mixing ratio (straw to sludge based on weight) improved the C/N ratio to 35, and the highest yield of biogas (15-fold higher than sludge mono) was recorded, along with the largest reductions in the total solids (TS), volatile solids (TVS) and chemical oxygen demand (COD) with percentages of 58.06%, 66.55% and 74.67%, respectively. The four introduced TDMMs showed high correlation with the experimental data. Among them, the logistic kinetic model is considered the best one for the experimental data representation. However, the ANN results showed that the training, validation and testing of the MFFNN-MFO model yielded very high correlation coefficients in comparison with the other used models, demonstrating that it is the most useful tool for modeling the biogas production process. These findings can support decision-makers in the establishment of sustainable development strategies that utilize ecofriendly technologies for efficient power generation from biomass residues and in predicting the model behavior.

Potato pulp waste is a potential biomass material and easily acidified substrate for anaerobic digestion. The present study evaluated the methane yield and microbial community resulted from biochar amendment for the co-digestion of potato pulp waste and dairy manure at different feed-to-inoculum ratios (2:1, 1:1, 1:2, and 1:3) and potato pulp waste to dairy manure ratios (4:0, 3:1 and 1:1). The results indicated that the digesters with a high feed-to-inoculum ratio (2:1, 1:1) and without biochar lead to volatile fatty acid accumulation and process failure, whereas the addition of biochar and/or co-digestion can increase the buffer capacity and improve the digestion efficiency. The biogas and methane yields of the digesters with biochar were 1.1–2.8 and 1.4–5.3 times higher, respectively, than those without biochar. The maximum biogas and methane yields of 476 and 200 mL/g TS, respectively, were achieved with a feed-to-inoculum ratio of 1:2, potato pulp waste to dairy manure ratio of 4:0, and biochar addition. Biochar and co-digestion can also enhance the relative abundance of the bacterial community. Methanomicrobiales and Methanosaetaceae were the main methanogens present in the anaerobic digestion of PPW. This paper provides a theoretical basis of easily acidified substrates used for biogas production.

The worldwide increase in the demand for wood pellets has led to increased interest in the use of biomass feedstock. However, the quality of pellets depends directly on the biomass feedstocks. This paper brings new insights about the influence of lignin distribution, physicochemical characteristics, and microstructure on the quality of pellets. The aim of the study was to characterize the physical, chemical, mechanical and energy properties of pellets produced from Pinus radiata (PR), Eucalyptus nitens (EN), Paulownia elongata × fortune (P), and Miscanthus × giganteus (MG), as well as to use microscopic techniques to examine how lignin distribution influences the mechanical properties. The findings show that the pellets made from PR were more suitable for bioenergy production compared to those produced with EN, P, and MG. Anatomical structure proved to be important in relation to pellet quality. The clear areas on the surface of the pellets presented relationship with the percentage of biomass lignin (which ranged from 26.4 to 34.2%). The P and PR pellets were more durable and had fewer empty spaces between particles. The pellets made from EN, which was the material most difficult to compact, had abundant cracks.

Bamboo is a fast-growing perennial plant rich at lignocellulose convertible for biofuels and biochemical production. Despite various physical and chemical pretreatments have been implemented for bamboo biomass utilization, it becomes essential to explore optimal technology for complete biomass saccharification to maximize bioethanol production in the desirable bamboo substrates. In this study, the steam explosion followed with optimized green-liquor pretreatments were conducted in different-year-old bamboo samples using response surface methodology. Compared to the older samples, the one-year-old bamboo (PhY1) showed a complete biomass enzymatic saccharification with hexoses yield of 100.0% (% cellulose), leading to the highest bioethanol yield of 20.3% (% dry biomass) achieved among all previously-reported bamboo processes. Notably, those combined pretreatments could not only cause an effective co-extraction of hemicellulose-lignin complexes, but also distinctively modify major wall polymer features (cellulose DP and accessibility, hemicellulosic Xyl/Ara and lignin S/G) for significantly reduced lignocellulose recalcitrance, which should lead to an integrated enhancement to biomass enzymatic saccharification in the PhY1 bamboo sample. Therefore, this study has demonstrated a powerful strategy for a green-like biomass process, providing an applicable technology to achieve maximum bioethanol production in bamboo and other lignin-rich bioenergy crops.

Major challenges in cultivation, harvesting, CO2 capture and downstream processing of microalgae biomass have to be confronted for successful commercial deployment. This study explored a sustainable process train to mass-produce a native marine algal strain, Nannochloropsis salina, for biocrude production and CO2 capture. The microalga was cultivated in a 3-m2 raceway pond with manual agitation, 10-m2 raceway ponds with and without CO2 supplementation and a 120-m2 pond with CO2 supplementation using carbonation column reactor (CCR). During the above experiments, the areal productivities obtained ranged from 7.5 to 34.4 g m−2 d−1 and the lipid content was between 29 and 80%. This study also demonstrated a novel 10 KLPD (kilolitres per day) capacity electropreciflocculation (ePF) reactor (∼0.56–0.78 KWh/KL) and filter press for biomass harvesting with 98.24% efficiency. The CO2 capture of N. Salina estimated was in the range of 45.38–208.12 tons ha−1 y−1, and the average was 95.39 tons ha−1 y−1. The cost estimated based on the 120-m2 pond trials was $3.46/kg of dry algal biomass. Thus the findings provide immense scope for future research on large-scale cultivation of Nannochloropsis salina for biofuel production and carbon capture applications.

Algae biomass has been recognized as one of the most suitable, efficient, and reliable feedstocks for bio-oil production. Among the different processes, hydrothermal liquefaction (HTL) is emerging as an effective technology for the valorization of various types of wet or dry biomass. Several factors, including temperature, retention time, and catalyst, significantly influence the overall efficiency of HTL products. The temperature ∼280 ± 40 °C is reported to be the most suitable range to achieve maximum bio-oil. Both homogeneous and heterogeneous catalysts have been used to improve bio-oil yield. For several advantages, heterogeneous catalysts are the preferred choice due to improved bio-oil generation, easy recovery, and uses. The eco-friendly approach and the reduction of heteroatoms in bio-oils make heterogeneous catalysts an ideal choice to be fortified. Alkaline catalysts have been considered most suitable to improve HTL yield. Variations in temperature and catalysts not only influence the yield of the bio-oil but also influence the characteristics of the bio-oil (e.g. high heating value, oxidative stability, gaseous emission, etc.) simultaneously. This review reveals interesting features including HTL temperature vs. yield, catalysts vs. yield, and the effect of wet and dry biomass on bio-oil properties, and finally, observations, remarks/limitations are presented for future studies.

Bioenergy crops provide enormous renewable biomass resources convertible for biofuel production, but lignocellulose recalcitrance fundamentally determines its enzymatic saccharification at high cost and low efficiency. In this study, total 30 diverse Miscanthus lignocellulose substrates were incubated with T. reesei strain to secret lignocellulose-degradation enzymes, and their major wall polymers features (cellulose crystallinity, hemicellulose arabinose and lignin H-monomer) were meanwhile examined with distinct impacts on the enzyme activities. Using characteristic Miscanthus (Msi62) de-lignin residue as inducing substrate with the reesei strain, this study detected that the Msi62-induced enzymes were of consistently higher enhancements on enzymatic saccharification of various lignocellulose residues examined in 17 grassy and woody bioenergy crops, particularly for the hemicellulose hydrolyses, compared to other two reesei-secreted cellulases and three commercial enzymes. Notably, based on SDS-gel protein separation profiling and LC-MS/MS analysis, the Msi62-induced enzymes consist of distinct cellulases (CBHI, BG, EGII) compositions and high-activity xylanases. Therefore, this study has demonstrated an applicable approach to achieve the optimal cellulases and xylanases cocktails that enable for low-costly and high-efficient enzymatic saccharification of diverse lignocellulose sources, providing a potential strategy for large-scale biofuel production in all major bioenergy crops.

The presence of inhibitors is still an economic bottleneck that needs to be resolved in order to make the biorefineries feasible, requiring the development of technologies capable of improving their competitiveness in the biofuel marketplace. Soluble and insoluble lignin can impair the enzymatic hydrolysis process by inhibition, deactivation, and unproductive adsorption of enzymes. Washing the pretreated biomass or using lignin-blocking additives during saccharification could mitigate these negative effects in future biorefineries. Here, an investigation was performed of the combined mitigation processes, in terms of their technical and economic feasibility in an integrated first and second generation (1G2G) sugarcane biorefinery. Evaluation was made of the impacts of biomass washing and soybean protein addition, separately or in combination, on glucose yields for enzymatic hydrolysis in the presence of high (liquor) and low (buffer) concentrations of soluble inhibitors/deactivators. Combining washing and soybean protein addition provided the highest glucose yields, with an increase of up to 50%. The effect of the mitigation processes could be explained by a combination of catalytic mechanisms acting on both soluble and insoluble lignin. In an industrial context, biomass washing (90 °C, 15% (w/w) solids, 3 steps) followed by soybean protein addition (12% (w/v) solids) provided a cost-competitive methodology for bioethanol production, with an estimated net present value of US$ 9.16 × 107, optimizing hydrolysis process in the 1G2G sugarcane biorefinery.

S. polyrhiza will be considering as a 2G feedstock, as generating 15–22 g/m2d fresh biomass by improving the quality of sewage. We propose a tractable circular process for pigments, lipid, Nano-catalysts and energy dense substrate (starch) from S. polyrhiza biomass. A ton of S. polyrhiza biomass was responsible for production of 0.8–1.2 kg of R-phycoerythrin, 0.7–0.9 kg of R-phycocyanin, 2.7–4.3 kg of lipids, 5.3–6.1 kg of ZVI, 79.7–80.4 kg of starch. The produced starch was further fermented to yield 38.8–40.8 l of ethanol. The waste generated in each step was utilized to produce 2.23 lakh liter biogas equivalent 8.51 GJ energy. The elimination of residue, reduce ∼79–85% in chemicals and energy usage in starch extraction. The synthesized ZVI efficiently mineralized RV5 wastewater at the rate of 26.29 ± 0.23 kgCODm−3d−1 up to seven cycles. S. polyrhiza reduce ∼240 kgCO2-eq for attaining one-ton fresh biomass. Overall findings will the base for starting bio-industries which minimizing the dependence on the terrestrial resources for food, energy and chemicals.

The effects of the briquetting temperature, briquetting pressure and hydrothermal pretreatment (HT) on the physicochemical properties of the resulted briquettes prepared from one herbaceous biomass, cotton stalk (CS) and one woody biomass, Chinese pine wood sawdust (WS) were mainly addressed in the paper. The apparent density, compressive strength and combustion characteristics of the resulted briquettes (CS/WS-Bs and CS/WS-HT-Bs) were investigated to evaluate their feasibility as the biomass briquette fuels. The results showed that the increase of briquetting temperature and pressure was beneficial to the densification of CS/WS-Bs. Compared with CS/WS-B, the hydrothermal pretreatment significantly improved the physical properties of the resulted biomass briquettes. As the hydrothermal pretreatment temperature increased, the heating values of the resulted CS/WS-HT-Bs increased, the content of fixed carbon increased and the yields of volatiles decreased. Furthermore, HT promoted the combustion characteristics. In addition, the Mad and heating values of all CS/WS-HT-Bs meet the Sweden Standard (SS18 7120). The most cost effective CS/WS-HT200/230-Bs were prepared from the cotton stalk and wood sawdust hydrothermal pretreated at 200 °C and 230 °C under the briquetting conditions of 75 °C and 80 MPa. However, the changes in the physical and chemical properties of the briquettes prepared from CS and WS followed different trends.

The main goal of this paper is the evaluation of combustion and grindability of torrefied palm kernel shells (PKS) obtained in a pilot-scale installation. The torrefied samples were prepared in different time conditions and temperatures, ranged from 220 to 300 °C. The physico-chemical properties were identified. Thermogravimetric analyses (TG-DTA) were used for characterization of the combustion performance and evaluation of the activation energy E α . The grindability of the pre-treated biofuel was investigated in a pilot-scale, coal bowl-roller milling unit. The results were compared to those of the raw PKS and bituminous coal. Torrefaction was found to increase carbon C content and HHV by 2–33 and 2–26%, respectively. Moreover, the combustion characteristics of the torrefied PKS samples are close to each other, but the ignition and burn-out temperatures differ significantly. The torrefaction changes the activation energy E α and it approaches the E α values to those of coal. Both the torrefaction temperature and residence time significantly affect the grindability. The grinding effect of PKS torrefied at 220 °C reached the value of 10%, whereas after torrefaction at 300 °C it doubled. The torrefaction considerably improves the properties and combustion behaviour of biomass, which is a good predictor for burning and co-burning in industrial units.

Torrefaction is a developing thermal process that has mainly been used to convert lignocellulosic feedstocks, both cultured and wasted, into a “charred” product that can be used as a fuel for power plants, combustion units, and gasifiers. Beneficial characteristics of torrefied products are increased energy density, removal of free water from the feedstock so that water is not being transported to the use facility, grindability indices similar to coal, and a more bio-stable product better suited for outdoor piled storage over the raw input material. A thorough review of the literature involving the torrefaction of fibrous agricultural wastes, food wastes, and non-lignocellulosic wastes (bacteria, algae, yeast, etc.) is presented in this paper. In general, average torrefaction operating conditions yielded greatly improved biofuels over the raw input feedstocks.

Chemical looping gasification is an efficient technology to convert biomass into valuable syngas. The iron-based oxygen carriers are a promising option for large-scale commercial applications due to their low cost and environmentally-friendly properties. The present study aims at evaluating the performance of the syngas production from the chemical looping gasification of torrefied woodchips in a pilot-scale bubbling fluidized bed reactor using iron ore and ilmenite as oxygen carriers. The effects of the operating parameters were investigated in this study. The results show that an increase in operating parameters could favor the process performance. Carbon conversion efficiency and the yields accelerate at high operating conditions. Carbon conversion efficiency showed a maximum value of 91.42% for iron ore at the ratio of oxygen carrier-to-biomass of 6, while the gas yield reaches the peak at SBR of 1.4 for ilmenite. The addition of steam in biomass chemical looping gasification improves hydrogen production and syngas quality in the product gas. Despite ilmenite provides better performance for hydrogen production, it characterizes by a lower reactivity compared to iron ore. It is also found that iron ore performs better at lower values of steam-to-biomass ratios and temperatures, while ilmenite shows good results at higher those parameters.

Nannochloropsis gaditana is a microalga, constituting cellulose 33 ± 1.3% and hemicellulose 18.2 ± 0.8%; used for the biofuel production. The cellulose in microalgal biomass would contribute to protecting the environment and constitute an attractive renewable raw material for bioethanol production. Ethanol production from N. gaditana microalgal biomass was investigated through Consolidated Bioprocessing (CBP) using Hangateiclostridium thermocellum KSMK1203 bacterial isolate. Screening and optimization of biomass pretreatment with different acids in different dosages, various hydrolysis time at 100 °C were performed and statistically validated using one-way ANOVA for efficient hemicellulose removal from NaClO2-treated N. gaditana biomass. Medium components and process parameters were statistically optimized by Response Surface Methodology. The maximum cellulase of 13.96 ± 1.354 IU/mL and ethanol of 12.90 ± 0.987 g/L were obtained in pretreated N.gaditana biomass. This study demonstrates that N. gaditana is a substitution for vegetal cellulose and these optimized conditions could be successfully used for commercial ethanol production using H. thermocellum KSMK1203.

This study presents a numerical investigation of steam gasification of hydrochar derived from fruit wastes. Four fruit wastes, apple chip pomace, grape pomace, rotten apple, and apple juice pomace, were used as feedstocks. Aspen Plus was used to simulate the gasification process. The syngas composition, hydrogen to CO ratio (H2/CO), CO to CO2 ratio (CO/CO2), and heating value (HHV) of the resulting syngas were analyzed. Results show that hydrothermal carbonization (HTC) increases the CO and reduces the CO2 content of the syngas after gasification. Accordingly, H2/CO reduces, and CO/CO2 increases after HTC treatment. Hydrothermal treatment also improves the HHV of the syngas. The obtained HHV of syngas from hydrochar gasification ranged from 10.1 to 15.3 MJ/Nm3 depending on the process parameters. Additionally, effects of process parameters were studied. Increasing the steam to biomass ratio (SBR) leads to a higher H2/CO, enriching the syngas with hydrogen (up to 64.7 vol%). Higher SBR also lowers the CO/CO2 ratio due to the consumption of CO and a rise in CO2. HHV increases with increasing pressure, and hydrochars exhibit more changes in HHV than raw feedstocks. The reaction temperature contributes to an increase in the fraction of CO in the syngas (up to 39.6 vol%). Although hydrogen increased initially with temperature, a slight reduction was observed for the gas at elevated temperatures, reducing the H2/CO ratio and increasing the CO/CO2 ratio.

With increasing energy and resource consumption due to population growth, the biorefinery concept is becoming popular. This concept aims to harness all the properties of biomass by producing energy and recovering useful chemical products. Nutrients such as nitrogen and phosphorus play a key role in the world’s food production because they are the main elements used in fertilizer production. Hydrothermal carbonization (HTC) has been presented as a suitable option for energy recovery that can also be used as a pre-treatment for enhanced nutrient recovery. During the HTC process, part of the nitrogen and phosphorus are solubilized into the process water and the other part remains within the hydrochar. Hydrochars are mainly used as soil amendments due to their high content of phosphorus and nitrogen, but in this process, water still contains a considerable concentration of these compounds making it a potential source for their recovery. Therefore, HTC may boost the nutrient recovery strategy by extraction (process water) or densification (hydrochar) from biomass if it is coupled with another nutrient recovery process. This review presents an overview of the phosphorus and nitrogen fate during the HTC process from a perspective of nutrient recovery, presenting existing technologies and future trends.

Rubberwood biomass is widely available in the southern region of Thailand and it has high potential for biofuel applications. Applications of this biomass still have some limitations, however, such as low energy properties and high biological decomposition. Therefore, the aim of this study was to enhance the fuel properties of rubberwood biomass by a torrefaction process. Rubberwood sawdust (RWS) was torrefied at different temperatures (200, 250, and 300 °C) and for various times (20, 40, and 60 min) in a moving bed reactor. The product yield and characteristics of torrefied RWS were investigated. Results showed that the solid yield of torrefied RWS was in the range of 39.07–88.69%, depending on temperature and time. The fuel atomic ratios of torrefied RWS were better than of raw RWS. The energy content and energy density of torrefied RWS were clearly enhanced (19.78–27.17 MJ/kg and 4.94–6.59 GJ/m3). ICP-OES results revealed a variation of inorganic elements in torrefied RWS, which was consistent with the ash components given by XRF. Ash fusion temperature of raw RWS and torrefied RWS ashes was stable at 1458 °C. The slagging index of torrefied RWS was decreased, while its fouling index was elevated.

The current work is focused to investigate the synergetic interactions between biomass (groundnut shell, bagasse, rice husk, Prosopis juliflora, mixed wood sawdust) and hydro-rich plastics (Low-density polyethylene (LDPE) and Polyisoprene (PIP)) in microwave co-pyrolysis. The heating value of co-pyrolysis oil (38–42 MJ kg−1) was enhanced dramatically compared to biomass pyrolysis oil (20–28 MJ kg−1). Among biomasses studied, the energy yield of bio-oil obtained from rice husk with LDPE mixture is higher (42%). Whereas bio-oil from polyisoprene and groundnut shell mixture has the highest energy yield (78%). Each gram of co-pyrolysis feedstock consumed 12–18 kJ of incident microwave energy. An increase in overall energy efficiency in co-pyrolysis (62–70%) is observed compared to that of biomass pyrolysis (46–57%). Actual mass yield (31–47 wt%) of co-pyrolysis bio-crude is lower than its predicted value (42–57 wt%) due to the formation of lighter gases. In the combinations of and hydrogen-rich plastics considered in this study, it was found that co-pyrolysis of LDPE: bagasse has produced bio-crude with the highest yield of aliphatic hydrocarbons (25.78%), and co-pyrolysis of LDPE: rice husk has produced bio-crude with high selectivity of aromatics (11.7%). The extent of de-oxygenation was promoted in the co-pyrolysis due to synergy.

The utilisation of waste biomass in biodiesel production as a sustainable energy source can lead to the incorporation of circular bioeconomy principles in the current economic systems. Herein, we synthesised a magnetically recyclable solid acid catalyst for the esterification of waste date seed oil. The catalysts possessed superparamagnetic behaviour and high saturation magnetisation, allowing them to be easily separated from the reaction mixture using an external magnetic filed. The esterification reaction was modelled and optimised by RSM (Design Expert program) and parametric study. The magnetic solid acid catalyst showed high catalytic performance with 91.4% biodiesel yield with optimum conditions of residence time, catalyst loading and temperature of 47 min, 1.5 wt %, and 55 °C, respectively. The solid catalyst was easily recovered by simple magnetic decantation and reused five consecutive times without significant degradation in its catalytic activity. This approach of using waste date seed coupled with cheap magnetic solid acid catalyst has the potential to create more sustainable and cost-effective catalytic systems for biodiesel production. This will complete the full cycle of waste date seed sustainably and facilitate the development of circular bioeconomy. The LCA results by using CML-IA baseline V3.06 midpoint indicators, for 1000 kg of biodiesel production showed the cumulative abiotic depletion of fossil resources over all the processes as 19037 MJ, global warming potential as 1114 kg CO2 eq, and human health toxicity as 633 kg 1,4-DB eq (kg 1,4 dichlorobenzene equivalent). The highest damage in all categories was observed during catalyst preparation, and reuse, which was also confirmed in endpoint LCA findings performed using ReCiPe 2016 Endpoint (E) V1.04.

Wood pellets are a commonly used biomass for energy production. However, due to the growing demand, many entrepreneurs have begun to produce non-wood biomass pellets. During experimental research, the process of combusting pellets of forest and agricultural origin at different furnace temperatures and different oxidizing atmospheres in a two-phase flow with the use of inert material modelling conditions in the upper zone of the fluidized bed reactor was analyzed. Inert material caused very significant differences in the time and mechanism of forest and agro biomass combustion. These differences are mainly associated with problematic phenomena during combustion, including sintering of ashes. The inert material accelerated the mass loss of forest biomass pellets at all temperatures by about 50–60%. In the case of agro biomass, the combustion time at the temperatures of 650 °C and 750 °C was shortened by about 20–30%, and in the case of the temperature of 850 °C, it was extended by about 10%. Increasing the value of the inert material stream resulted in a reduction of the combustion time at all temperatures. Increasing the concentration of oxidant in the atmosphere of combustion caused the reduction of the combustion time of all tested fuels.

In this study, a prototype of a passive-cum-active dryer with a biomass fired-heater and a plate heat exchanger was developed and tested. The developed dryer consists of a vertical plate heat exchanger, a biomass combustion chamber, and a drying chamber. It can be run in both passive and active modes. Sliced turmeric fingers were dried in the dryer in both the modes. While drying the turmeric slices from its initial moisture content of 87.62% (w.b.) to 12.78% (w.b.) in 32 h, the dryer consumed 24–25.5 kg of mango wood of the moisture content of 12.5% (w.b.). The thermal efficiency of the dryer was estimated from the experimental data that was found to be in the range of 4.35–4.62%. Wide varieties of biomass can be used as fuel in the developed dryer. As it runs both in the passive and active mode, the dryer is expected to be useful in remote areas where the power supply is not available or there is a frequent outage of the power supply.

The feasibility of fuel property analysis of the biomass fuel by laser induced breakdown spectroscopy (LIBS) has been demonstrated in a previous study. As a further move to apply this quick method to industrial application for direct monitoring of the woody biomass pellets quality, effects of four key parameters during the pelletizing process on the LIBS spectral data have been investigated before applying LIBS directly to the woody biomass pellet. Partial Least Squares (PLS) models were built to evaluate the performance of the LIBS fuel property analyses directly on the wood pellets supplied by different manufacturers, which were produced on different pellet mills, with different pelletization technologies and under various pelletizing conditions. The results showed satisfactory performance using LIBS technique for direct determination of the fuel property of wood pellets without further sample preparation. The coefficient of determination (R2) of calibration models were all above 0.98. The root mean square error of prediction (RMSEP) of the gross calorific value (GCV), volatile matter (VM) and ash content (AC) were 0.09 MJ/kg, 0.52% and 0.15% respectively, while the average relative error (ARE) were 0.39%, 0.54% and 8.52% respectively, and the average standard deviation (ASD) were 0.14 MJ/kg, 0.52% and 0.18% respectively.

Microalgae were grown in 12-L airlift photobioreactors (PBR) containing biodigested swine manure (BSM), cattle manure (BCM) and domestic sewage (BDS), with 5% v/v, 25% v/v and 30% v/v respectively and compared with synthetic medium CHU. BSM with biogas/air mixture (10% CO2) injection on the 8th day led to of 13,257 ± 430 × 104 cell mL−1, and 2.0 ± 0.16 g L−1 dry biomass with a 26% lipid content, which was approximately 70% higher than with air. After microalgae purification, biogas at the PBR outlet averaged 91% v/v CH4. In terms of bioenergy: i) the biogas lower heating value (LHV) increased from 22,554 to 33,294 kJ m−3 (47.6%) with BSM, and similarly with BCM and BDS; ii) lipid content was increased, and iii) biohydrogen production is expected to increase from the PBR. For wastewater bioremediation, the microalgae Tetradesmus obliquus were able to remove 99.3% of ammonia and 99.2% of phosphorus concentration from BSM. There was a 96% BOD (628 mg L−1 to 23.3 mg L−1) and 91% COD reduction (1262 mg L−1 to 132 mg L−1). There was a 70% increase in biomass production and up to 4-fold lipid content increase with the procedure in comparison to air injection.

Microalgal biomass offers high biomass productivity, high photosynthetic efficiency, and low land requirement. However, there are challenges for the sustainable conversion of microalgae-to-biofuels. Through torrefaction, microalgal biomass can be upgraded to enhance its biomass characteristics. A life cycle assessment (LCA) is proposed to evaluate the environmental impact of the production of torrefied microalgal biomass (TMB). Using LCA, four different conversion pathways of generating TMB are considered and compared. The four scenarios include the effect of scaling-up the production to pilot-scale and comparing two cultivation systems (open pond and the photobioreactor). The analysis includes the influence of the torrefaction severity index (TSI) on environmental impacts. The results have shown that TSI is directly related to the global warming potential (GWP) wherein the influence of torrefaction temperature to the GWP was higher compared to the duration. The impact of the cultivation system was relatively higher compared to the other processes due to its high energy requirement. The scale-up effect of the cultivation phase resulted in a reduction of the GWP by 128% and 91% for the open pond and the photobioreactor, respectively. A net negative GWP impact is achieved in a pilot-scale with the use of an open pond cultivation system. With this configuration, the uptake of carbon dioxide during the cultivation outweighs the GWP impacts of producing TMB. Furthermore, the negative GWP result is lower compared with the results of previous studies on torrefaction and pyrolysis.

Depletion of fossil fuels and the adverse impacts burning these fuels has increased the attention towards utilizing biomass energy sources, thus increasing the focus on Bio-Coke technology, which can fully convert biomass waste into alternative fuels. This study analyzed the characteristics of Bio-Coke conversion from biomass abundantly found in Malaysia, which included rice husk, rubber wood sawdust, coconut husk, sugarcane bagasse, oil palm frond, oil palm trunk and empty fruit bunch (EFB). Results indicated better physical feature characteristics of biomass solid fuel. For example, Bio-Coke produced from EFB showed an apparent density of 1.414 g/cm3, combustion duration of 1664 s, and maximum compressive strength at room temperature (25 °C) and 700 °C of 95.107 and 9.412 MPa, respectively, which were found to be higher than that of wood pellet. This study showed Bio-Cokes can be potentially used as an alternative fuel to reduce the usage of coal coke in the future.

We propose an integrated strategy for the production of vital platform chemicals, levoglucosenone (LGO) and 5-hydroxymethylfurfural (HMF), used to produce a high-value chemical, 1,6-hexandiol, from lignocellulosic biomass. In such processes of producing essential chemicals from biomass, cellulose loading in the solvent has a significant impact on production yield and, consequently, the economics of the process. In this study, we compare four different loadings of 1, 3, 5, and 10 wt% to suggest the optimal cellulose loading in tetrahydrofuran. The integrated process is economically optimal at a cellulose loading of 5 wt%. The minimum selling price (MSP) of the LGO and HMF mixture is estimated to be $2387/ton, which is competitive compared with the previously reported MSP of $2920/ton (He et al. Green Chemistry,19, 3642–3653, 2017), at the optimal loading of 5 wt%.

This article analyses and evaluates the impact of the technology of soil processing on the biomass indicators of faba bean waste. Samples from five different primary tillage systems were taken and analysed. The raw material of faba bean waste was processed and pressed into cylindrical pellets. The results of the experimental research of the pellet properties revealed that the content of moisture of the pellets from faba bean waste changed from 8.2% (deep cultivation, 3-GP) to 10.8% (untreated soil, 5-ND). The highest density of faba bean waste pellets was obtained from the sample of conventional soil ploughing, (1-IA) (1311 kg m−3), while the lowest density was recorded under shallow ploughing (2-SA) – 1275 kg m−3. The lower calorific value of dry biofuel from faba bean waste pellets was similar in all the samples and ranged from 16.9 MJ kg−1 (5-ND) to 17.1 MJ kg−1 (2-SP). The calorific value of faba bean waste pellets was relatively high and was close to the calorific value of some types of wood waste. The following harmful gas emissions were analysed and evaluated: carbon monoxide CO, carbon dioxide CO2, unburned hydrocarbons CxHy, and nitrogen oxides NOx. The harmful gas environmental emissions detected while burning the pellets of faba bean waste have not exceeded the permissible limits. The best results of the pellet properties, the content of ash and the emissions were obtained under conventional ploughing (1-IA) and deep cultivation (3-GP). The research results suggest that faba bean waste could be used as granulated biofuel, since the main parameters of this legume waste correspond to the basic requirements of solid biofuel. It was determined that under untreated soil (5-ND) technology the CO2 emissions eqv. were twice lower than under conventional soil ploughing (1-IA). These results show that no-till technology is suitable for sustainable agricultural practise both for producing the faba bean grain and for processing the pellets from the waste.

In this study, a novel renewable hybrid system was designed and constructed to efficiently produce biodiesel through various methods. First, a parabolic trough solar collector (PTC) was used as a renewable source for producing desalinated water in a solar still. Then, the heat dissipated by PTC and water produced by the solar still were used to generate biodiesel. Finally, the combined cycle of PTC/desalination/biodiesel generator was applied to produce heat and steady power. Necessary electricity in the hybrid system containing pumps, mixing tools, etc. was provided by photovoltaic panels. After launching the hybrid system and performing experiments to produce biodiesel on Palm and Chlorella bioenergy carriers, the percentage of the biodiesel production for these two species in different ways were as follows: alkaline catalyzed transesterification (79.17,81.46), acid-catalyzed transesterification (79.1,81.43), two-step transesterification (78.07,81.42), supercritical transesterification (75.16,80.68), microemulsion (76.3,81.4), electrolysis (50.25, 58.87), and pyrolysis (13.677,14.833). Moreover, the lowest price belonged to the alkaline catalyzed transesterification which for palm/chlorella was 0.65/0.972. In most methods, the cetane number of palm-based biodiesel was higher (∼58). Consequently, it had a better combustion quality compared to chlorella-based biodiesel (∼44). This study also modeled various processes for the bioenergy carrier conversion. The results were consistent with experimental data.

We report a strategy for production of 5-nonanone which is a bio-based platform chemical that can be produced in large quantity from a variety of lignocellulosic biomass sources. In this strategy, the cellulose and hemicellulose fractions of lignocellulosic biomass are catalytically converted to γ -valerolactone (GVL) using the biomass derived GVL as a solvent. To generate the integrated strategy, we develop separation subsystems to achieve high purity of product. Importantly, GVL can be upgraded to 5-nonanone with high yield in a single reactor using a dual catalyst bed of Pd/Nb2O5 plus ceria-zirconia. We design a heat exchanger network to satisfy the total energy requirements of the integrated process via combusting lignin fraction of biomass. Economic feasibility of the process is investigated using discounted cash flow analysis.

Olive stones obtained as a by-product from olive oil extraction in combination with the favourable climate in Mediterranean countries are value-added feedstocks for the energy sector due to low moisture content ( 20 wt. %), suitable calorific value ( > 18.7 MJ kg−1 as received) and high bulk density (about 750 kg m−3). The torrefaction process at Arigna Fuels with high energy efficiency of (above 90%) improves biomass properties for conversion to a high-value fuel for use in solid fuel stoves. This study reports the effect of moisture content, organic composition, inorganic matter, particle size, heat treatment temperature and residence time on product yields, O2/CO2 reactivity, calorific value, composition and thermal conductivity value of torrefied olive stones. Results showed that both lignocellulosic content and ash composition equally influenced the reactivity of torrefied material. For the first time, time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that the structure of torrefied material from small olive stone particles contains more cellulose than lignin when compared to large grains. Importantly from a technological standpoint, the lower heating values of torrefied olive stones (21.8 MJ kg−1) [1] from a small scale reactor were within the range of values for torrefied woodchip briquettes containing high starch binder content which was an energy increase of ≈ 15% when compared to the raw feedstock. The results showed that olive stones of particle size ≤ 2 mm produced during torrefaction at 270 °C for 30 min are the most suitable material and conditions for briquetting due to high solid yield, low reactivity and low thermal conductivity values. These conditions are recommended for the pilot plant operation using olive stones from the Mediterranean region.

Loss of energy potential during storage is a significant consideration when using crop residues for bioenergy production. However, previous studies about biomass storage only reported dry matter loss and composition change, but not the direct effects on bioenergy production. This study investigated the changes in chemical composition, enzymatic digestibility, and methane yield of corn stover after one-year outdoor dry bale storage under covered and uncovered conditions. The contents of easily degradable components, including extractives and hemicellulose, decreased by about 20%–50%, while the contents of cellulose and lignin did not change significantly. The methane yields of corn stover after one-year covered or uncovered storage declined by 13.2% and 22.7%, respectively, partially due to the decrease of cellulose degradability and the losses of hemicellulose and extractives. Increasing particle size from 1 mm to 12.7 mm reduced the methane yield of the stored corn stover by up to 26.4%. The modified Gompertz model suggested that both storage conditions and particle size affected methane yield, maximum methane production rate, and lag phase time of anaerobic digestion (AD) of corn stover. The information reported in this paper can provide important information for economic analysis and life cycle analysis of AD of corn stover.

The industrial-scale production of lignocellulosic-based biofuels from biomass is expected to benefit society and the environment. The main pathways of residues processing include advanced hydrolysis and fermentation, pyrolysis, gasification, chemical synthesis and biological processes. The products of such treatment are second generation biofuels. The degree of fermentation of organic substances depends primarily on their composition and chemical structure. Optimization of fermentation conditions leads to better understanding of occurring processes. Therefore, an overview of recent developments in fermentation modeling is necessary to establish process parameters enabling high yields of biofuels production. Among process parameters affecting the yield and rate of biogas and biohydrogen, pH of the pulp, temperature, composition, biomass pre-treatment and digestion time are to be considered. The technology of anaerobic co-digestion has been intensively developed as a valuable solution for the disposal of organic wastes and sewage sludge. Modeling of biogas production from lignocellulosic biomass has been intensively investigated and is well described by adapted ADM1 model. Modeling of fermentative hydrogen production lacks a kinetic model incorporating process parameters with the view of pretreatment and fermentation. This paper presents the state-of-the-art on the problems related to lignocellulosic biomass pre-treatment and discusses the mechanisms of lignocellulosics conversion to gaseous biofuels.

Miscanthus is a leading bioenergy crop with enormous biomass resource convertible into bioethanol and biochemicals. However, lignocellulose recalcitrance basically causes costly bioethanol production with potential secondary pollution to the environment. In this study, the green liquor (mixed sodium carbonate and sodium sulfide) pretreatments were optimized using response surface methodological modeling for enhancing biomass saccharification and delignification in Miscanthus. By comparison, the optimal saccharification approach led to relatively higher hexose yield of 87% (% cellulose) for bioethanol yield of 17.1% (% dry matter) with the sugar-ethanol conversion rate at 98%, whereas the optimal delignification approach could achieve the highest delignification rate at 93% potential for lignin-derived biofuel or value-added biochemicals. Notably, those two optimized pretreatments could distinctively extract hemicellulose-lignin complex and altered wall polymer features, leading to much increased cellulose accessibility for efficient biomass enzymatic hydrolysis. Exceptionally, the optimal delignification led to decreased biomass porosity accountable for relatively lower hexose yield, suggesting that its cellulose microfibrils may be aggregated from excessive non-cellulosic polymers extraction. Hence, this study has demonstrated two optional strategies for green-like and cost-effective biofuels and biochemical production in Miscanthus and other bioenergy crops.

Biodiesel, mainly produced from soybean, is an alternative to replace fossil fuels and to decrease the Brazilian external dependence on petrochemical diesel. However, soybean represents almost 85% of biodiesel production costs and government subsidies are necessary in order to make biodiesel production feasible. A possible solution to this problem is to look to the steps upstream of alkaline transesterification, like oil extraction and refining, where co-products can be isolated, making the soybean processing chain a biorefinery. This work aims to economically evaluate this idea and to show the real impact of biodiesel and the co-products on the biorefinery profitability. Operational and economic parameters were obtained from literature and were adjusted according to time, place, and flowrate. As a result, it is shown that biodiesel production can be profitable, but it should not be seen as the main destination for soybean and provided there is a market for its other fractions.