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To effectively utilize paper sludge and allow for energy recovery, the thermal behaviors of two paper sludge (PS) were studied by thermogravimetric analysis (TGA). The kinetic analysis was conducted according to Coats-Redfern (CR) method. The evolution of pore structure and surface morphology was investigated by N2 adsorption and scanning electron microscopy (SEM), respectively. The mineral transformation was analyzed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Derivative thermogravimetry (DTG) curves of PS show two different stages. The first stage was due to devolatilization (200–400 °C) and the second stage (650–800 °C) accounted for the mineral decomposition and char degradation. It was found that a large number of pores formed during pyrolysis because of char fragmentation. The specific surface areas increased from 5.161 to 22.894 m2 g−1 for PSA and from 9.007 to 16.126 m2 g−1 for PSB with the increase of temperature. The intense absorption bands of calcite (1426, 875 and 712 cm−1) in raw material indicated that calcite was the main mineral of PS. The decomposition of calcite at 700 °C and the further production of gehlenite (916 cm−1) at 900 °C, and the dehydration of kaolinite at 500 °C and further transformation into mullite (996 cm−1) at 900 °C were observed by both FTIR and XRD. The XRD results were generally consistent with FTIR analyses.

Previous studies showed that the cellulase hydrolysis of corn straw pretreated with circulating alkali black liquor combined with ozone was suppressed. In this paper, the alkali black liquor was sequentially withdrawn for 0–6 times under the optimal pretreatment conditions, and components characterization was analyzed to identify the main factors inhibiting cellulase hydrolysis in recycled alkali black liquor. Through the component analysis, the organic matter and acid precipitation contents increased throughout the cycles. At the fourth cycle, the cellulase hydrolysis rate was decreased significantly, the growth of lignin content in alkali black liquor was slowed down and the total dissolved solid increment was decreased to 8.33mg/mL, 69.52% lower than previous cycle increase. GC-MS results showed that phenols, benzene ring heterocyclic and furans were main degradation products. It indicated that small molecular organics and lignin were inhibitors of cellulase hydrolysis, which accumulated during recycling, reducing alkali utilization and delignification efficiency, resulting in lower enzymatic hydrolysis rate. This study has revealed the components inhibiting the enzymatic hydrolysis of corn straw in recycled alkali black liquor, which is beneficial to the recovery and efficient utilization of recycled alkali black liquor.

The developed Ni-La/Al2O3-CeO2-Bamboo charcoal (ACB) catalyst was applied to the co-pyrolysis of straw and plastic to produce hydrogen in a horizontal quartz tube pyrolysis furnace. In this study, the effects of the mixing ratio of straw and plastic, the presence and stability of the catalyst on the co-pyrolysis hydrogen production were investigated. Experiment showed that the addition of PE can increase the yield of H2 within a certain range, and the best mass ratio of 5:5 was found. In the co-pyrolysis process with the participation of the catalysts, the macromolecular tar can be cracked into combustible gases such as H2, and the H2 yield could be increased to 332.2ml/g (Ni-La/ACB) is much higher than 68.87ml/g without catalyst. Compared with Ni/ACB, Ni-La/ACB had been increased the alkalinity by adding La element and enhanced the carbon deposition resistance of the catalyst, which makes the catalyst maintain higher stability. This was also confirmed in stability test experiments.

This study aims to evaluate the effects of compaction on the anaerobic biodegradability of straw. In the study, compaction tests were carried out at different applied pressures, i.e., 0 (CK), 277 (T1), 555 (T2), and 1109 Pa (T3), respectively. The results showed that the maximum gain in biogas production was 298.35 mL·g−1 TS for the T2 reactor, significantly higher than CK (228.51 mL·g−1 TS) and T3 (249.14 mL·g−1 TS) reactors. The concentration of COD and TVFA of the T3 reactor was the highest throughout the anaerobic digestion (AD) process, the same thing for DHA, with maximum values of 39.12 g/L, 11.62 g/L, and 31.97 ug TPF/(h mL), respectively. However, the effect of compaction on the physical and chemical indicators of digestive fluid was not significant during the batch-type AD process. The factor analysis results suggested that the major factors affecting biogas production were influenced by the compaction and varied based on the different stages of digestion. Scanning electron microscopy (SEM) showed that the straw surface was damaged as the compaction increases. The degradation of TS in the AD did correlate to biogas yield, the best performance of TS loss rate was T2 (44.79%), and the lowest was CK (37.64%). This research concluded that compaction on gas production via changing the environment during the bath AD process and proper compaction could positively affect biogas yield, while excessive compaction will inhibit gas production. The impacts of compaction on the physicochemical indexes of the liquid digestate, structural and compositional changes of solid digestate, and biogas yield

Ultrasound technology is often associated with harmful effects on enzyme reactions, although it is possible to improve the productivity of bioprocesses when suitable conditions are employed. Sugarcane bagasse and straw are the feedstocks widely used in Brazil for second-generation (2G) ethanol production; however, the lignocellulose biomass conversion into fermentable sugars through the enzymatic route is not yet fully optimized. Lignocellulolytic enzymes represent a significant part of the costs related to 2G ethanol production. Nonetheless, they exhibit great potential for cost reduction due to improved enzyme features: mainly increment of its activity and an increase of hydrolysis yield. This enzymatic hydrolysis of feedstock can be enhanced by green technology ultrasound application’s combined action on the enzymes and their substrates. The mixed action increases the lignocellulose saccharification; hence, it is considered a promising alternative for fermentable sugar release. The process optimization using green approaches, such as ultrasound and enzymatic treatment, can boost the sugar yield, thus emphasizing the importance of steps integration towards biomass conversion. This review attempts to provide an overview of the effects of ultrasound treatment on lignocellulolytic enzymes used in the 2G ethanol production and those of the process intensification through an unprecedented bibliometric search.

Microalgae biomass can be a feedstock for anaerobic digestion, but the recalcitrance of the cell wall limits fully exploiting this source of organic matter. Alkaline pretreatments modify the structure of the cell wall facilitating bacterial attack and solubilizing the organic matter content. It is unknown whether alkaline hydrogen peroxide can help to improve biogas production from microalgae biomass compared to other alkaline pretreatments. This work focused on methane production at alkaline conditions (pH 9) with pretreated microalgal biomass (Scenedesmus obtusiusculus). Alkaline hydrogen peroxide (AHP) was used for the thermo-alkaline pretreatment and compared with pretreatments using NaOH or CaO. The pretreatment with 15% CaO solubilized the highest carbohydrates (22.1%) and proteins (18.3%), while the microalgal biomass pretreated with 4 M NaOH or 1.5% AHP attained the highest yields of methane (227.1 mL and 208.4 mL CH4/g VS, respectively), improving the methane potential between 34 and 46%, and producing biogas with methane content up to 91%. A preliminary techno-economic and energy analysis showed energy savings of 40% with 4 M NaOH and 31% with 1.5% AHP; therefore, AHP could be considered a suitable option for the pretreatment of microalgal biomass.

Thermal pretreatment by torrefaction is known to produce improved properties in biomass fuels, but the role of pellet size on key properties in commercially available hardwood derived fuel has not been investigated to date. In this study, densified Australian woody biomass was torrefied over different temperatures (250–300 °C), time (30 and 60 min) and mean pellet size (7 ± 0.5 mm and 15 ± 0.5 mm). Benchmarking, relative to raw fuel properties, is reported in terms of proximate analysis, high heating value (HHV) and water immersion tests as well as FTIR and thermal stability (TGA). Significant differences of 23.55% in mass loss (ML) and 10% in hygroscopic behaviour were observed at varied pellet size. FTIR analysis of the samples identified reduction of polar species such as the hydroxyl (-OH) functional group during torrefaction. This increased the hydrophobicity of torrefied pellets. Torrefaction of larger sized pellets was also accompanied with lower hemicellulose and cellulose degradation. A correlation predicted the HHV of the torrefied pellets which fits well with the actual HHV’s of the wide body of literature with an average difference of less than 1 MJ/kg. Pellet sizing was found to impact the fuel properties only at milder torrefaction conditions. As such, with the increase in torrefaction severity, the effect of pellet size became insignificant. The outcomes emphasise the need to describe pellet size distributions when reporting torrefaction performance indicators, particularly if commercial scale torrefaction is used at higher temperatures and longer times.

Made available in DSpace on 2022-04-29T08:30:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) This study aimed at investigating the binderless densification of biomass for the production of a durable solid biofuel by mixing cassava rhizome, sugarcane bagasse, and sugarcane straw. Six different treatments were applied with specific percentages of these three biomass feedstocks for the densification in a lab-scale press with heating of 120 °C. Three blend treatments and three 100% material treatments (without mix) were analyzed. Achieved briquettes were examined via various tests including proximate analysis, volumetric expansion, compression test, and energy index to assess the mechanical and energetic properties. Results indicated that the mixtures are suitable for the production of briquettes and treatment B2 was the best blend for briquette production. This study suggested that binderless densification of biomass can be achieved with the mixing of cassava rhizome, sugarcane bagasse, and sugarcane straw, which will support the development of qualified solid biofuels without the cost of binders. Department of Energy Engineering BioJoule - Biomass Densification Laboratory Department of Energy Engineering São Paulo State University (Unesp), Campus of Rosana, SP Department of Mechanical Engineering São Paulo State University, SP Department of Environmental Sciences Federal University of São Carlos, SP Department of Energy Engineering BioJoule - Biomass Densification Laboratory Department of Energy Engineering São Paulo State University (Unesp), Campus of Rosana, SP Department of Mechanical Engineering São Paulo State University, SP FAPESP: #2018/11837-2 FAPESP: #2018/14827-8 CAPES: 001

With realizing the potential of algal biomass as a good natural resource for the harnessing of valuable bioproducts, algal biomass production has gained a lot of interest in recent years. However, due to some limitations such as low harvesting efficiency, higher nutrient supply, and high water requirement, the production of algal biomass is uneconomical. Over the past several years, researchers are continuously working on growing algae as a biofilm for easy microalgae harvesting, concentration of algal biomass to a great extent, and requiring less quantity of water as compared to other microalgae cultivation methods. Most of the documented studies have been carried out on either use of algal biomass for tertiary treatment of wastewater or cultivation and harvesting of algal biomass for biofuel production. Limited research studies have documented other applications of the algal biofilm system. The present review paper summarizes the current knowledge on various factors affecting microalgae growth, development of algal biofilm, and operation of algal biofilm systems to help properly understand and optimize these factors for better economics, more positive environmental impacts, and successful potential applications of the attached growth systems. The important factors include the structure of algal biofilms, EPS matrix, supporting materials, nutrient availability, environmental conditions, and biofilm thickness and harvesting frequency. The potential applications such as wastewater treatment, CO2 sequestration, microalgae–microbial fuel cell, large-scale biomass production, and water quality improvement are also discussed.

The effects of the blends of charcoal fines and Schizolobium parahyba var. amazonicum (parica) wood on the briquette quality and on the combustibility of this solid biofuel is not fully understood, especially from fast-growing plantations with Amazonian tree species. In addition, this paper presents new information about the occurrence of inorganic elements that may contribute to increase the emission of toxic compounds in the combustion of parica wood, for example, Cl. Thus, this study evaluated the composition of charcoal and S. parahyba var. amazonicum wood for briquettes, investigating the occurrence of inorganic elements responsible for the toxic organochlorine contaminants. Different formulations between charcoal and S. parahyba var. amazonicum wood were analyzed and later compacted in a laboratory briquetting machine with temperature of 90 °C and pressure of 5 MPa. The chemical and elemental composition of S. parahyba var. amazonicum wood was determined using X-ray fluorescence spectrometry (μ-XRF). The briquettes produced were tested for bulk and energy densities, proximate composition, heating value, equilibrium moisture, and resistance to diametral compression. S. parahyba var. amazonicum wood had chlorine levels below the recommended by international standards for solid biofuel intended for non-industrial use (< 300 mg kg−1). S. parahyba var. amazonicum, despite being a fast-growing species, has ideal chemical characteristics for energy purposes (Cl, S, and ashes). The most suitable briquettes were those produced with 50% of charcoal and 50% of S. parahyba var. amazonicum wood. This solid biofuel showed higher heating value of 22.74 MJ kg−1 and ash content of 2.65% db.

Cassava (Manihot esculenta) is a woody bush extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. The main residue from its cultivation is the cassava stalk, which is normally used as soil fertilizer or in culture propagation. The main goal of this paper is to evaluate two routes (biochemical and thermochemical) for bioenergy production (ethanol and synthesis gas—electricity) using cassava stalk as raw material. A detailed techno-economic and energy assessment is carried out based on the simulation approach of both conversion routes to determine the production costs of main products and the overall energy efficiency of the processes. The electricity production costs vary from 0.008 to 0.037 USD/MJ, whereas the ethanol production costs range from 1.11 to 2.02 USD/L (including subsidies). The change in the production costs was observed due to the assumptions of the model, e.g., cassava stalk, transportation, and enzyme costs. The overall energy efficiency of the gasification and ethanol fermentation was 68.7 and 25.1%, respectively.

Lignocellulosic biomass is one of the most abundant raw materials in the world, and it is mainly composed of carbohydrate polymers (cellulose and hemicellulose) and lignin. Its applications vary from the production of pulp and paper, to the most recent plant-based bioethanol production, which has challenge due to low hydrolysis conversion rates by the inherit recalcitrance of biomass. The biomass is naturally resistant due the high complexity in the component organization and interaction in the cell wall. The application of pretreatment technologies is one of the most used strategies to overcome biomass recalcitrance. These techniques often require a catalyst to modify the lignocellulosic structure which can be acids, alkaline compounds, ionic solutions, organic solvents, and even pressurized steam among others. The type of catalyst dictates the name of the pretreatment involved. This work presents an overview of these strategies, along with some recent contributions from the scientific community to improve biomass conversion technologies. The discussion is focused on the key factors related to the recalcitrance and conversion process, as well as the composition and physicochemical properties.

Rice husk is a prospective bio-oil feedstock due to its plentiful supply, but its unfavorable characteristics like high moisture content, high ash content, and low energy density tend to jeopardize both the yield and quality of bio-oil produced by fast pyrolysis. Lately, various pretreatments, namely, washing, torrefaction (dry and wet), and their combined pretreatments, have been researched on rice husk with the aim of improving its unfavorable characteristics for bio-oil production. However, the influences of different pretreatments on pretreated rice husk and the subsequent bio-oil produced have not been compared. Hence, this review paper presents an overview of rice husk as a bio-oil feedstock and its pretreatment methods for bio-oil production via fast pyrolysis. Particular emphasis is placed on the rice husk characteristics and their impacts on the bio-oil production via fast pyrolysis, as well as the different types of rice husk pretreatment and their influences on the characteristics of pretreated rice husk, product yields of fast pyrolysis, and the composition and physical properties of the bio-oil produced. A comparison of the physicochemical properties of rice husk- and other biomass-based bio-oil alongside those of petroleum fuel oil is also outlined. Major challenges and future prospects towards the utilization of rice husk as a bio-oil feedstock and the integration of rice husk pretreatment with fast pyrolysis for large-scale applications are also discussed.

Made available in DSpace on 2022-04-28T19:40:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This is a pioneer study evaluating the methane (CH4) production potential from residues of integrated first (vinasse and filter cake) and second (deacetylation pretreatment liquor from straw) generation (1G2G) sugarcane biorefinery, providing a fully chemical characterization of them and their relation with the anaerobic digestion (AD) process. Small-scale assays provided fundamentals for basing the co-digestion optimization by assessing the optimal co-substrates synergistic conditions. Biochemical methane potential (BMP) tests showed co-digestion enhanced CH4 yield of isolated substrates, reaching up to 605 NmLCH4 gVS−1. The association of vinasse and deacetylation liquor as co-substrates increased the BMP by ~ 38% mostly by nutritionally benefiting the methanogenic activity. The kinetic analysis confirmed that the deacetylation liquor was the co-substrate responsible for improving the CH4 production in the co-digestion systems due to the highest CH4 conversion rate. The alkaline characteristic of the liquor (pH ~ 12) also prevented alkalizing from being added to the co-digestion, an input that normally makes the process economically unfeasible to implement on an industrial scale due to the large quantities required for buffering the reactor. The filter cake had the lowest BMP (262 NmLCH4 gVS−1) and digestibility (≤ 40%), further limited by the required stirring to improve the mass transfer of biochemical reactions. The present study drives towards the more sustainable use of vinasse, the most voluminous waste from the sugarcane industry, and lignin-rich residues derived from pretreatment alkaline methods, aiming at an energy-efficient utilization, by at least 16% when compared to the traditional vinasse AD. The experimental and modeling elements from this work indicated the lignin-rich liquor is the main responsible for putting the co-digestion as a disruptive technological arrangement within the 1G2G sugarcane biorefineries, reinforcing the biogas production as the hub of the bioeconomy in the agroindustrial sector. Interdisciplinary Center of Energy Planning University of Campinas (NIPE/UNICAMP), R. Cora Coralina, 330 – Cidade Universitária, São Paulo Interdisciplinary Research Group On Biotechnology Applied To the Agriculture and the Environment (GBMA) School of Agricultural Engineering (FEAGRI) University of Campinas (UNICAMP), Av. Candido Rondon, 501 – Cidade Universitária, São Paulo Brazilian Biorenewables National Laboratory (LNBR) Brazilian Center of Research in Energy and Materials (CNPEM), Giuseppe Máximo Scolfaro, 10000 – Bosque das Palmeiras, São Paulo Department of Bioprocess and Biotechnology College of Agricultural Sciences São Paulo State University (UNESP), Av. Universitária, nº 3780 – Altos do Paraíso, São Paulo Chemical Engineering School University of Campinas (FEQ/UNICAMP), Av. Albert Einstein 500, São Paulo Department of Bioprocess and Biotechnology College of Agricultural Sciences São Paulo State University (UNESP), Av. Universitária, nº 3780 – Altos do Paraíso, São Paulo FAPESP: 2015/50612-8 FAPESP: 2016/16438-3 FAPESP: 2018/09893-1

The combination of carbon and nitrogen-rich co-substrates results in a better balance and increases the stability of the anaerobic co-digestion (AcoD) process. In this work, the AcoD process of waste from the leather industry (shavings and sludge) with waste from agriculture (oat straw) was assessed with regard to the energy (biogas production) and waste treatment efficiency (reduction of organic matter). The results indicate that the addition of untreated oat straw improved the AcoD process, increasing biogas production (25.44 mL of cumulative biogas/g of VSS added) by almost 60% when compared to the AcoD of only leather waste (16.17 mL/gVSS). Also, the effect of acid, alkaline, thermal, and the combination of these pretreatment techniques was evaluated on the lignocellulosic composition of oat straw and on methane yields. Pretreatments improved the characteristics and bioavailability of oat straw, particularly in methodologies that use alkali, with a significant increase in cellulose content accompanied by a decrease in hemicellulose and lignin content. However, the possible formation of secondary products or sterilization of important microorganisms did not reflect in a greater production of biogas: 21.06 mL/gVSS for oat straw pretreated only with HCl and 21.91 mL/gVSS for oat straw pretreated with HCl in autoclave; 5.20 mL/gVSS for oat straw pretreated with NaOH; and 3.43 mL/gVSS for oat straw pretreated with NaOH in autoclave; thermal pretreatment probably has generated toxic compounds from hemicellulose and cellulose degradation, which inhibited the AcoD process and, as consequence, virtually no biogas was produced.

Biomass (especially algae) is a renewable energy source that can be a great alternative to fossil fuels. Wet algal biomass converts into products such as solid, aqueous, and gaseous phases as well as biocrude in hydrothermal liquefaction (HTL). The aim of this work was to provide detailed exergy analyses of the production of biocrude from Nannochloropsis sp. by HTL. Physical and chemical exergy of the HTL products, exergy losses, exergy efficiency, and exergy distribution of the HTL process were determined in this research. The highest exergy loss and the lowest efficiency values obtained for the heat exchanger were 65,856.83 MJ/hr and 66.64%, respectively, which was mainly caused by the irreversibility of the heat transfer process. Moreover, the HTL reactor had high efficiency (99.9%) due to the complex reactions that occurred at high temperature and pressure. Also, the optimum operating conditions of the reactor were obtained at 350 °C and 20 MPa by using sensitivity analysis. The high overall exergy efficiency of the process (94.93%) indicated that HTL was the most effective process for the conversion of algae. In addition, the exergy recovery values of the overall exergy input values in the HTL process for biocrude, as well as the aqueous, solid, and gas phases, were nearly 74.88%, 18.42%, 0.86%, and 0.76%, respectively. Exergy assessment provides beneficial information for improving the thermodynamic performance of the HTL system.

Sweet sorghum bagasse displays many characteristics rendering it a promising substrate for lignocellulosic ethanol production. In this study, the steam pretreatment catalyst, enzymatic hydrolysis and the substrate loading for the fermentation were investigated in order to maximise the production of ethanol from the feedstock. The results deemed water as a sufficient pretreatment catalyst since the SO2 impregnation of the biomass did not produce any significant beneficial effects on the yield of ethanol produced. The preferred pretreatment and enzymatic hydrolysis conditions were incorporated in a fed-batch simultaneous saccharification and fermentation (SSF) process using pressed-only (not washed) WIS at a final solid loading of 13% (w/w) that resulted in the targeted ethanol concentration of 39 g/L with a corresponding yield of 82% of the theoretical maximum. Yeast inhibition coupled with significant glucose accumulation was observed at higher solid loadings of 16% and 20%. Ultimately, the sweet sorghum bagasse could be integrated into existing ethanol production regimes to improve the global bioenergy production.

Grass clippings have a good biomethane potential and, if acquired from roadside verges, nature management or natural grasslands do not compete for arable land, avoiding the food versus fuel debate. However, before the grass is processed in a wet anaerobic digester, a pretreatment step is advisable to minimize the problems associated with its fibrous nature. In this study, the effects of a semi-industrial extrusion pretreatment on fresh and ensiled grass were investigated through an energetic and economic assessment. Extrusion improved the mixing properties of the grass feedstock and reduced the formation of a floating layer even at a solid concentration of 10% (w/v). This pretreatment also enhanced the biomethane potential of ensiled grass and fresh grass by, respectively, 18 and 11% on a fresh matter basis, while shredding reduced this value by 14% when compared to fresh grass. This was attributed to changes in the volatile solids (VS) content of the treated samples, as all conditions resulted in similar biomethane yields when calculated per ton of VS, ranging from 325.5 to 337.6 Nm3 CH4/ton VS. However, ensiling resulted in a longer lag phase during biogas production attributed to the leaching of readily available sugars from the ruptured plant cells; nevertheless, this is not expected to be significant in a buffered industrial system. The revenue resulting from the extrusion treatment, between €6 and €17 per tonne of FM, compensated the cost of this additional step, indicating that extrusion would be a techno-economically sound process for the anaerobic digestion of grass.

The potential for obtaining renewable energy from organic substrates such as food waste (FW) and biowaste has generated increasing interest in the anaerobic digestion process. Kinetic models are used to analyse the impact of different parameters on biological processes and thus, to optimize them to achieve and to increase the quality and quantity of biogas. This study presents an approximation of the pre-dimensioning of semi-continuous anaerobic reactors treating FW, based on: (i) biochemical methane potential (BMP) assays, in different conditions of substrate-inoculum ratio (S/I: 0.5 and 4.0 g volatile solid-VSsubstrate·g VSinoculum−1) and nutrients (with macro-nutrients (N and P) and micronutrients, only micronutrients (Ni, Co, Mo and Fe) and without nutrients), and (ii) the kinetic performance through three kinetic models (transfer function-TF, logistic function-LF and modified Gompertz-MG), using Pmax (maximum methane production) and Rmax (maximum rate of methane production) as kinetic parameters related to the hydraulic retention time. The best S/I ratios were below 1.0 gVSsubstrate·gVSinoculum−1 with nutrients. Although the three kinetic models obtained a good fit (R2 > 0.9 and RMSE

Microalgae are a non-food grade, fast-growing, and non-land competitive biomass with relatively high energy content. The high lipid and mineral contents of microalgae render it beneficial for the production of biofuels and value-added products. The complete energy-effective harnessing of microalgae potentials concerning biodiesel production is faced with drawbacks because of the energy-intensive steps required to harvest and dry microalgae. The limitations have impelled the search for alternative and low-cost utilization of microalgae in wet form for biofuel production. Anaerobic digestion (AD) is among the wet techniques for the valorization of microalgae that is gaining immense research attention because of its simplicity. Also, the products can be recycled to reduce material costs. This review is focused on the recent trends and comparison of the AD process to maximize energy recovery from microalgae biomass and co-digestion of microalgae waste coupled to biodiesel production (after lipid extraction), respectively. The yield of methane gas in these two processes is compared and the pros and cons of biogas production using microalgae biomass and microalgae waste considering that the former produces biofuels and the later value-added products are discussed.

The aim of this study is to cultivate Spirulina platensis and Scenedesmus obliquus microalgae in consortia using effluents of cattle waste anaerobic treatment in order to give possibilities to the production of microalgae biomass to biorefineries uses. The biomasses obtained were characterized to evaluate the potential for the production of biofuels and other bioproducts. The effluent was used in sterile and non-sterile conditions to better understand the influence of other microorganisms in N and P removal. The biomass obtained with the addition of 10% of sterile effluent in Zarrouk media (20%) presented 44.12 and 34.62% of carbohydrates, using Spirulina platensis in monoculture or the 50%/50% consortia of Spirulina and Scenedesmus, respectively, this biomass presenting the potential to be used to bioethanol production. Nitrogen and phosphorous removal were higher in non-sterile conditions and reached 92.7 and 49.66% of nitrogen and phosphorous removal, respectively, using the consortia and with the addition of 30% effluent in the media. The cultivation of microalgae in a consortium may be used to assist the treatment of water concurrently with the production of biomass to different applications.

The possibility of using waste distillery stillage (first-generation technology) after dilute acid pretreatment, as a medium for the preparation of beet molasses mash, for ethanol production according to the simultaneous saccharification and fermentation (SSF) technology, was assessed. The combination of lignocellulosic hydrolysates made from acid-pretreated stillage with sugar-rich beet molasses is an effective way of utilizing the first-generation ethanol production by-products in the second-generation ethanol production technology. It was demonstrated that the final ethanol concentration could be as high as 90 g/L. The process yield was over 94% of the theoretical yield when the molasses was diluted using acid-pretreated maize distillery stillage. An attempt to increase the pool of fermentable sugars by using cellulases to hydrolyze cellulose failed due to product inhibition in the fermentation medium with a high glucose concentration. A more than threefold increase in the concentration of ethyl acetate (even up to 924.4±11.8 mg/L) was observed in the distillates obtained from the media incubated with cellulases. The use of beet molasses combined with the hydrolysate of pretreated distillery stillage also changed the concentration of other volatile by-products. An increase in the concentration of aldehydes (mainly acetaldehyde to a concentration of above 1500 mg/L), methanol, 1-propanol, and 1-butanol was observed, while the concentration of higher alcohols (isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol) decreased. Interestingly, the use of cellulases in fermentation media from molasses and stillage hydrolysates resulted in an average fourfold increase in the concentration of this ester to a maximum level of 924.4±11.8 mg/L. Hydrolysates made from acid-pretreated distillery stillage, combined with sugar-rich beet molasses to boost the efficiency of the conversion process, can be successfully used in the production of second-generation fuel ethanol. However, further optimization of the cellulose enzymatic hydrolysis process is required for efficient use of the raw material.

The aim of the study was to investigate the potential of microalgal cultivation on anaerobic liquid digestate as a growth medium. The two methods of liquid digestate treatment including centrifugation and distillation and the two algal strains (Chlorella vulgaris and Arthrospira platensis) were compared. Additionally, the volume of the liquid digestate used to prepare the culture medium constituted from 10 to 50% of the medium volume. The study demonstrated that the highest C. vulgaris and A. platensis biomass productions of 2490 mg TS/L and 2990 mg/L, respectively, were obtained by adding 50% of distilled digestate to a growth medium. Regarding centrifuged liquid digestate, only 10% dilution was required to obtain the maximum final biomass concentration. A. platensis removed 81.1% and 66.4% of the total nitrogen from medium prepared on distilled and centrifuged digestate, respectively, while C. vulgaris ensured 64.1% and 47.1% of removal, respectively. The phosphorus removal from both culture media was higher than 94.2% with A. platensis, while it was 70.4% from distilled and 87.4% from centrifuged media with C. vulgaris. The study confirmed a great potential of microalgal biomass production on anaerobic liquid digestate with a high treatment efficiency of digestate.

Microalgae have been reported to exhibit mutualistic interactions with other microorganisms like bacteria, filamentous fungi, and yeast and help each other co-exist. The potential of microalgae to perform photosynthesis and accumulate lipids make them suitable candidates for lipid production. Biofuel production from various single oleaginous microorganisms is already in practice. However, the high cost of biomass harvesting, extraction of lipids, and contamination issues are significant challenges of biofuel bioprocess commercialization. Recent microalgal co-culture studies showed considerable potential for easy biomass harvesting and reduction in overall energy consumption cost. Therefore, microalgal co-culture could be an alternative to overcome these constraints and enhance biomass and lipid production. Additionally, the integration of the nutrient sequestration process from potential agro-industrial wastewater using microalgal co-culture can reduce the cost of the substrate requirement for cultivation as well as ecological load. The co-culture in wastewater has shown excellent total phosphate removal efficiencies by microalgae Chlorella sorokiniana and yeast Rhodotorula glutinis, nitrogen removal by microalgae C. sorokiniana with activated sludge, and ammonium-nitrogen removal by C. vulgaris and fungi Aspergillus sp. co-culture. This review summarized the current advances towards biofuel and its value-added production from various microalgae co-culture and compared it with monoculture fermentation. It also includes some critical challenges of co-culturing for the economically viable bioprocess development for biofuel production. Furthermore, techno-economic analysis and life-cycle assessment of co-culture technology were also discussed for biofuel production feasibility from microalgal co-culture.

Made available in DSpace on 2021-06-25T12:38:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-20 National Commission for Scientific and Technological Research in Chile FIC Atacama 2016 This study assesses whether the use of Tessaria absinthioides (TA) pellets as a bioenergy resource is feasible or not. Its fuel properties were characterized and its combustion behavior assessed via a traditional log wood stove with a basket of wood pellets. Combustion of pinewood (Pinus radiata) commercial pellets (CP) was used as a reference in order to analyze experimental results. TA has a high ash content of 8.1% and an HHV of 17.47 MJ kg(-1). Alkaline index on the TA pellets was of 1.46 kg alkali GJ(-1), a relatively high value, which resulted from high sodium content in ash. Oven and exhaust temperatures during the combustion of TA and CP present similar behavior. The combustion chamber's highest temperature for CP was 841.15 degrees C, while for TA, the highest temperature was 685.65 degrees C. Furthermore, CO and PM emission was superior for TA pellets, averaging about 4943.6 235.2 mg Nm(-3) and 32.45 6.49 mg MJ(-1), respectively at 13% O-2. Results obtained have shown that there were no apparent hindrances for an extensive use of TA as a bioenergy resource and use of pellet baskets to combust pellets in traditional wood log stoves.Graphical Abstract Univ Bio Bio, Fac Ingn, Dept Ingn Mecan, Concepcion, Chile Univ Concepcion, Unidad Desarrollo Tecnol, Concepcion, Chile Univ Concepcion, Fac Ingn, Dept Ingn Mecan, Concepcion, Chile Sao Paulo State Univ, Fac Engn Guaratingueta, Energy Dept, Guaratingueta, Brazil Fed Ctr Technol Educ Celso Suckow Fonseca CEFET R, Angra Reis Campus, Angra Do Reis, Brazil Sao Paulo State Univ, Fac Engn Guaratingueta, Energy Dept, Guaratingueta, Brazil National Commission for Scientific and Technological Research in Chile: CONICYT PIA/APOYO CCTE AFB170007 National Commission for Scientific and Technological Research in Chile: FAPESP-CONICYT 2018/04819-4 National Commission for Scientific and Technological Research in Chile: FONDECYT 11180828 FIC Atacama 2016: BIP 30486479

Microalgae biomasses offer important benefits regarding macromolecules that serve as promising raw materials for sustainable production. In the present study, the microalgae Arthrospira platensis DHR 20 was cultivated in horizontal photobioreactors (HPBR), with and without temperature control, in batch mode (6 to 7 days), with anaerobically digested cattle wastewater (ACWW) as substrate. High dry biomass concentrations were observed (6.3–7.15 g L−1). Volumetric protein, carbohydrate, and lipid productivities were 0.299, 0.135, and 0.108 g L−1 day−1, respectively. Promising lipid productivities per area were estimated between 22.257 and 39.446 L ha−1 year−1. High CO2 bio-fixation rates were recorded (875.6–1051 mg L−1 day−1), indicating the relevant potential of the studied microalgae to mitigate atmospheric pollution. Carbon concentrations in biomass ranged between 41.8 and 43.6%. ACWW bioremediation was satisfactory, with BOD5 and COD removal efficiencies of 72.2–82.6% and 63.3–73.6%. Maximum values of 100, 95.5, 92.4, 80, 98, and 94% were achieved concerning the removal of NH4+, NO3−, Pt, SO42−, Zn, and Cu, respectively. Total and thermotolerant coliform removals reached 99–99.7% and 99.7–99.9%. This microalgae-mediated process is, thus, promising for ACWW bioremediation and valuation, producing a microalgae biomass rich in macromolecules that can be used to obtain friendly bio-based products and bioenergy. Supplementary Information The online version contains supplementary material available at 10.1007/s12155-021-10258-4.

The vinasse is a polluting effluent generated in large quantities in the ethanol production process, whose disposition is problematic and costly. In this work, the vinasse problem is addressed through a comparison between four alternatives for treating it with energy recovery: (i) concentration in an evaporator system until 25 Brix for volume reduction (CONC); (ii) concentration in an evaporator system until 65 Brix, with subsequent incineration of concentrated vinasse (CONC + INC); (iii) anaerobic biodigestion (BIOD); and anaerobic biodigestion and digestate treatment by membranes (BIOD + MEM). The techno-economic assessment is performed through mass and energy balances, evaluating two configurations of the cogeneration system: considering back-pressure (BPST) and condensing-extraction (CEST) steam turbines, in combination with an economic feasibility evaluation. Furthermore, an evaluation of GHG emission was performed in each case. The BIOD + MEM and CONC cases promoted a significant reduction in effluent volume (53% and 82.8% respectively), while the CONC + INC case practically eliminated the disposal expenses of this effluent. Regarding the cogeneration system, the BIOD case presented the highest bagasse surplus (59.9 kg/t cane) for the BPTS configuration, while the CONC + INC case presented the highest electricity surplus (89.7 kWh/t cane) for the CEST configuration. As for the economic assessment, the cases CONC with BPST, and CONC + INC for both BPTS and CEST presented economic feasibility, while the GHG emission assessment indicates that the BIOD case with BPST is the option with the lowest emissions. A sensitivity analysis was also performed to evaluate eventual variations in market and operating conditions.

Microalgal biodiesel is technically viable to power diesel engines. This third-generation biofuel has great performance of combustion and can reduce emission of greenhouse gases into the atmosphere. However, its production is currently very expensive, relative to petrochemical diesel. Development and implementation of strategies to optimize productivity and quality of biomass and thus ensure this future-proof biofuel is economically feasible to fabricate and competitive with diesel oil on an industrial scale is challenging. This meta-analytic overview documents the diversity of fastest-growing, oil-accumulating microalgae; performance of cultures and systems; strategies for inducing lipids; and quality and economics of microalgal biodiesel. The microalgae, Neochloris oleoabundans, Scenedesmus obliquus, Desmodesmus sp., and Micractinium sp., are hyperaccumulators of lipids. The genre, Micractinium sp., is a thermophile, and thus it can resist hydrothermal streams. Complementarily, it is the fastest to grow and the most productive in both biomass and biodiesel. This should be of great importance to roll-out sustainable, high-performance algal systems in marginal lands in tropical zones, where the heat often makes the planning and management of projects difficult and expensive. Heat shock, nutritional starvation, and photoperiod are the most effective algae-specific strategies for inducing mechanisms for lipogenesis in Ankistrodesmus dimorphus, Chlorella vulgaris and Leptolyngbya sp., Cylindrotheca closterium and N. oleoabundans, and Amphora subtropica and Dunaliella sp., respectively. Rhodococcus sp. produces a significant amount of biomass at very low cost, relative to diesel oil. The concept of synergistically co-culturing microalgae with this photosynthetically active bacterium may be an option to save the producer the expenditures and uncertainties of third-generation biodiesel.

There are still bottlenecks to be overcome for the feasible industrial production of first- and second-generation ethanol (1G2G EtOH). One of them is the pretreatment stage. Washing is a candidate strategy to remove lignocellulose-derived byproducts from pretreated biomass, in order to reduce the negative effects of furaldehydes and phenolic compounds in the downstream biochemical reactions. However, the effectiveness of the removal of these inhibitors is highly influenced by the operational conditions of the washing process. Here, evaluation was made of the techno-economic impacts of including a washing operation after hydrothermally pretreating sugarcane bagasse for 2G EtOH production in an integrated 1G2G biorefinery. Different washing protocols were tested, considering their effects on the enzymatic hydrolysis and fermentation, and experimental data were used for simulation of process scale-up. The removal of inhibitors improved the glucose yield by 40%, followed by an increase of ~ 30% in EtOH productivity. These findings showed that washing is a cost-competitive option for a 1G2G biorefinery, with a net present value for the industrial unit of ~US$ 2.3E + 8, which was the highest among the 1G2G scenarios analyzed.

The use of agro-industrial waste as substrate to produce enzymes has been widely studied in order to adjust the high productions of these biocatalysts with a reduction of the final cost in an ecologically correct process in the industry. This is the first work to use peach-palm (Bactris gasipaes Kunth.) waste for the production of carboxymethylcellulases (CMCase) by the Trichoderma stromaticum AM7 under solid-state fermentation (SSF) using the artificial neural network and genetic algorithm (ANN-GA) to optimize the cellulase production. ANN-AG was used to determine the optimal influence of nitrogen source concentration (2.46%), time (12 days), and temperature (26 °C) on the cellulase production with 98% of efficiency for algorithm prediction of endoglucanase activity. The predicted and experimental values of the CMCase activity in U/g of dry initial substrate (gds) were 122.9 and 120.0, respectively. After all optimization processes, the variation of these parameters allowed a final increase of 31.58-fold when compared to the initial fermentation. Moreover, the treatment of peach-palm waste with T. stromaticum AM7 endoglucanase had an effect on the degradation of the fibers analyzed by scanning electron microscopy and the saccharification of the waste by releasing reducing sugar (807.80 mg/g) for 8 h of incubation. These results are very promising to waste valorization and the biotechnological and industrial applications of cellulase of the T. stromaticum AM7 to food processes and biofuel production.

Cassava pulp (CP) is considered as a major and low-cost agro-industrial solid byproduct of cassava starch processing, where 48% of starch granules was still entrapped in its complex lignocellulosic matrix of cell wall structure with 21% cellulose and 8% hemicellulose. In this study, the liquid hot water (LHW) pretreatment was aimed to disrupt the cell wall structure of CP and solubilized hemicellulose and starch into saccharides to enhance biomethane production. Reaction conditions of LHW pretreatment, temperature (160–200 °C), and time (0–30 min) were optimized by response surface methodology. LHW pretreatment at 187 °C for 7 min boosted the highest level of starch and hemicellulose solubilization into the liquid phase, resulting in the maximized glucose yield of 444 mg/gCP. Starch and hemicellulose were mostly removed from CP at 99 and 79%, respectively, while 68% cellulose and 10% lignin particularly remained in solid residue. The disrupted cell wall structure and crystalline cellulose after LHW pretreatment were also observed. Microbial inhibitors such as furfural and hydroxymethylfurfural were found in low concentration at 31 and 32 μg/mL, respectively. In addition, there were no lag phase and inhibitory effect during anaerobic digestion of the pretreated CP. Biochemical methane potential of the LHW-pretreated CP showed the methane production rate and methane yield at 1.6 times and 35% higher than that of non-pretreated CP, respectively, by shortening anaerobic digestion time from 22 d to 10 d. It was shown that LHW was an efficient chemical-free method for enhancing biodegradability of CP in conversion to biomethane.

In addition to the use as biofuel, the utilization of poplar wood as a raw material from short-rotation coppice (SRC) became increasingly important in recent years. Because poplar SRCs are harvested during dormant season, wood storage is of particular importance to guarantee wood processing industries a continuous wood supply. The study focuses on the change of physical and chemical properties of poplar wood by the application of different storage strategies over a 9-month period. Therefore, a total amount of 60 m3 test log piles were set up in 2018 for six different storage variants: compact piles, compact piles with water sprinkling and oxygen exclusion, each with logs in bark and debarked. The effects on wood moisture content, equilibrium moisture content and wood density (ρ0) and the changes in the chemical components lignin, cellulose, hemicellulose and extracts were determined and evaluated. As expected, the wood moisture content changed in a wide range over the storage period, depending on the variant. The levels of equilibrium moisture (changes from − 4% to − 13.1%) as well as wood density (changes from − 2.61% to − 9.01%) decreased for all variants between start and end of storage. Changes in chemical composition were observed for all storage variants, which indicates microbial activity supporting the assumption that the observed mass loss is driven by wood decay. Overall, changes were more homogeneous for logs in compact piles compared to the other storage methods. Considering the weather conditions during the investigated period, the results indicate that storage in compact piles with debarked logs is the best method for the conservation of poplar wood from SRC.

Microalgae, as the most promising raw material for biodiesel, can absorb and transform N, P, and organic matter in wastewater into cell components such as oil, carbohydrate, and protein. The cultivation of microalgae in wastewater provides the possibility to realize harmless treatment and resource utilization of wastewater and reduce the cost of microalgal culture. Whether in a single microalgal culture process or wastewater system, there always be a large number of bacteria interacting with microalgae, forming a complex microecological system. Although microalgal–bacterial coculture system is feasible features for the higher biomass production and better nutrient adaptability from wastewater, the precise understanding of interaction and coexistence in water bodies is still unclear. Some major challenges are to develop sustainability in the microalgal–bacterial coculture system due to the incomplete knowledge about the mechanism of communication, algal growth promotion, and effect of microalgae on the indigenous bacteria in wastewater. In the present review, nutritional interaction and signal transduction, two main interaction models of algae and bacteria, and the effect of synergism of these two models on microalgal system are summarized. Moreover, the impact of algal–bacterial coculture on algal growth and removal of pollutants in wastewater treatment process was expounded systematically to develop highly efficient consortium systems by covering the sustainability limitations. This work would provide guidance for the establishment of efficient algal–bacterial symbiosis system in the wastewater with complex microecology and nutrient environment to improve the accumulation of microalgal biomass and reduce the cost of microalgal culture.