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The current energy and climate crisis calls for immediate action in replacing fossil fuels with those derived from renewable sources. The Energreen process performs the direct liquefaction of biomass to produce a liquid biofuel for the cement industry and an aqueous solution of added-value compounds for further processing. The present work details the development of an Aspen Plus® model to simulate this biomass liquefaction process. The proposed model describes the Energreen liquefaction process using simplified reaction kinetics and thermodynamic models. The model was validated using data from a real liquefaction pilot plant with a deviation of 6.4%. The simulation, conducted with several biomass samples of variable compositions, showed that the process is robust enough to deal with different compositions and, due to the substitution of the fossil fuels presently used in the cement plant, it will allow savings of up to USD 102,000 per year to be achieved. Several analyses of the sensitivity of the results to the process variables were performed and it was possible to identify the reactor temperature and the reaction activation energy as the most impactful parameters on the process output. Overall, the results allow us to conclude that the proposed model is a solid framework for the optimization of industrial liquefaction processes.

Lignin is a remarkable natural polyphenol that provides trees with physical and (bio-)chemical resistance, as well as the ability to reach considerable heights. Lignin is also intrinsically circular with slow biodegradability, thereby serving as a carbon source for soils. There is a growing interest in using industrial lignin as an environmentally and economically beneficial material. However, most of the industrially produced lignin is still used as a cost-efficient energy source by the forestry sector. To efficiently redirect the use towards material applications and to avoid the end-of-life problems connected to traditional plastics, there is an imminent need and opportunity to include circularity as an important design parameter. In this review, we critically assess opportunities and obstacles for lignin as a component in circular materials, as guided by life cycle assessment and benchmarking to best practices in materials science and engineering, e.g., circularity “by design”. We cover and reflect on recent and emerging advances in nanotechnology and materials science that showcase how lignin can contribute to carbon fixation as a viable alternative to its combustion in the pulping processes. We argue that, with adequate considerations, lignin has the potential to enable the development of new circular biobased materials that do not cause accumulation of environmentally persistent waste, and are equipped with attractive functionalities and performance for the benefit of a sustainable society.

Bioenergy recovery from biomass by-products is a promising approach for the circular bioeconomy transition. However, the management of agri-food by-products in stand-alone treatment facilities is a challenge for the low-capacity food processing industry. In this study, the techno-economic assessment of a small-scale anaerobic digestion process was evaluated for the management of jabuticaba by-product and the production of biomethane, electricity, heat, and fertilizer. The process was simulated for a treatment capacity of 782.2 m3 y−1 jabuticaba peel, considering the experimental methane production of 42.31 L CH4 kg−1 TVS. The results of the scaled-up simulated process demonstrated the production of biomethane (13,960.17 m3 y−1), electricity (61.76 MWh y−1), heat (197.62 GJ y−1), and fertilizer (211.47 t y−1). Economic analysis revealed that the process for biomethane recovery from biogas is not profitable, with a net margin of −19.58% and an internal rate of return of −1.77%. However, biogas application in a heat and power unit can improve project feasibility, with a net margin of 33.03%, an internal rate of return of 13.14%, and a payback of 5.03 years. In conclusion, the application of small-scale anaerobic digestion can prevent the wrongful open-air disposal of jabuticaba by-products, with the generation of renewable energy and biofertilizer supporting the green economy toward the transition to a circular economy.

Xylan is a renewable polysaccharide, readily available in agricultural and forestry residues. It can be hydrolyzed to produce xylooligosaccharides (XOS) with prebiotic activity and xylose, a precursor for several industrial chemicals. Enzymatic hydrolysis of xylan in the lignocellulosic biomass to obtain xylose and XOS requires a pretreatment to facilitate xylanase activity. In this study, organosolv was evaluated for the delignification of corncob while retaining xylan in the pretreated biomass. The treatment at 170 °C for 1 h with 70% ethanol provided 50% lignin removal and 81% xylan recovery. Increasing temperatures and decreasing ethanol fractions decreased the pH and the xylan recovery. Loss of xylan in the organosolv at 190 °C and in the liquid hot water treatment could be prevented by the addition of 100 mM MgO, without compromising lignin removal. Pretreated corncob was suspended in citrate buffer and hydrolyzed by commercial xylanases. Accellerase XY (250 U/ml) at pH 5.5 and 55 °C and Econase XT (0.6 U/ml) at pH 6.0 and 70 °C provided around 65% xylan digestibility and generated xylose (9.8 g/l) and XOS (10.9 g/l), respectively. This approach could decrease xylan loss and degradation in the pretreatment step and yield clear hydrolysates composed of essentially xylose or XOS. Lignocellulosic biorefineries can benefit from the efficient utilization of xylan, increasing sustainability.

The Sustainable Development Goals defined by the United Nations established a roadmap on the way to a sustainable society based on a circular economy in which the residual fractions of process streams emerge as raw materials for the provision of material goods and services. In this context, the approach of biorefineries as the technological scheme for processing integrally renewable resources stands out. Among the different target products, "bioactive" compounds have aroused great interest given their high added value. This work evaluates the environmental profile associated with the valorization of residual lignocellulosic waste streams: olive pruning and eucalyptus residues for the biotechnological production of nisin, an antimicrobial compound produced by Lactoccocus lactis with application in the food preservation and biomedical sectors. Process modelling in combination with Life Cycle Analysis allowed addressing the conceptual design and the environmental assessment of a full-scale production process. As a main conclusion, the technological feasibility of the valorization of waste fractions as sources of fermentable sugars in the biotechnological process has been demonstrated. Moreover, the integral use of the raw materials can allow not only the production of nisin as an economic driver, but also of other biotechnological products such as lactic acid and energy for the self-supply of the process. The main novelty of this manuscript is based on rethinking the valorization of lignocellulosic waste beyond energy recovery to obtain bioproducts with high added value in the market with applicability in the food sector. Although energy recovery is the most widely implemented end-of-life option, the use of lignocellulosic waste as fermentable sugars has been shown to improve sustainability and circularity outcomes This research has been financially supported by the European project iFermenter (Grant Agreement 79057). The authors belong to the Galician Competitive Research Group (GRC ED431C 2017/29) and to the Cross-disciplinary Research in Environmental Technologies (CRETUS Research Center, ED431E 2018/01 SI

Ionic liquids (ILs) have been widely used in the pretreatment of biomass. However, the effects of residual ILs on the enzymolysis and fermentation of biomass are still unknown. Therefore, a large quantity of water-washing is usually followed after biomass pretreatment to eliminate the inhibition of residual ILs on subsequent hydrolysis and fermentation steps. In this work, the effect of choline glycine ([Ch][Gly]) concentration on the activity of cellulase and Bacillus sp. strain P38 was systematically investigated to explore the impacts of residual ILs on enzymolysis and fermentation. The results confirmed that the activities of them were almost not inhibited in low concentrations (less than 0.5 wt%) of [Ch][Gly]. Under optimal pretreatment conditions, the maximum cellulose digestibility was 99.23%. Enzymatic hydrolysate was suitable for l -lactic acid fermentation without appreciable inhibition, and the highest sugar-acid conversion rate of 96.33% was obtained by simplified detoxification. This work provides an economic route to produce fermentable sugar and l -lactic acid, which shows an industrial application prospect in lignocellulosic biorefinery.

As an industrial energy plant, the whole parts of the sunflower crop were used for biofuel production through a biorefinery approach. Two scenarios were suggested for this biorefinery, i.e., using all parts of the crop separately and the whole residues as a mixture. The oil extracted from seeds was applied for biodiesel production through transesterification using a 6:1 methanol to oil molar ratio with 0.7% catalyst at 50 °C for 65 min. The process resulted in a 96.2% biodiesel yield with a heating value of 41.6 MJ/kg, corresponding to 84 kg biodiesel per ton of sunflower crop and 108.8 L gasoline-equivalent. Three physiochemical pretreatments were employed for structural modification of lignocellulosic residues, and the solid and liquid phases of the pretreatments were anaerobically digested for biomethane production. The effects of hot water (180 °C, 1 h), concentrated phosphoric acid (50 °C, 1 h, 85%), and sodium carbonate (142 °C, 18 min, 4%) pretreatments on composition, crystallinity, morphology, and biogas production of solid samples were evaluated. The highest methane yield of solid fractions was obtained from samples treated with phosphoric acid, and the seed cake showed the maximum yield of 342.7 N mL/g VS among all parts. Furthermore, the liquid phase of the hot water and alkaline pretreatments produced a high amount of biomethane, contrary to the acidic pretreatment. The overall mass balance showed that 11095.0 MJ/t energy (containing 346.7 L gasoline energy) was produced through the optimum biorefinery, where the untreated mixture and seed cake were used for biomethane production and the extracted oil for biodiesel production.

The development of an effective, realistic, and sustainable microbial biorefinery depends on several factors, including as one of the key aspects an adequate selection of microbial strain. The oleaginous red yeast Rhodotorula sp. has been studied as one powerful source for a plethora of high added-value biomolecules, such as carotenoids, lipids, and enzymes. Although known for over a century, the use of Rhodotorula sp. as resource for valuable products has not yet commercialized. Current interests for Rhodotorula sp. yeast have sparked from its high nutritional versatility and ability to convert agro-food residues into added-value biomolecules, two attractive characteristics for designing new biorefineries. In addition, as for other yeast-based bioprocesses, the overall process sustainability can be maximized by a proper integration with subsequent downstream processing stages, for example, by using eco-friendly solvents for the recovery of intracellular products from yeast biomass. This review intends to reflect on the current state of the art of microbial bioprocesses using Rhodotorula species. Therefore, we will provide an analysis of bioproduction performance with some insights regarding downstream separation steps for the extraction of high added-value biomolecules (specifically using efficient and sustainable platforms), providing information regarding the potential applications of biomolecules produced by Rhodotorula sp, as well as detailing the strengths and limitations of yeast-based biorefinery approaches. Novel genetic engineering technologies are further discussed, indicating some directions on their possible use for maximizing the potential of Rhodotorula sp. as cell factories. Key points: • Rhodotorula sp. are valuable source of high value-added compounds. • Potential of employing Rhodotorula sp. in a multiple product biorefinery. • Future perspectives in the biorefining of Rhodotorula sp. were discussed.

Sugarcane bagasse, the major by-product of the sugarcane industry, can be used to produce valuable materials such as cellulose or cellulose-based materials. In order to obtain more accessible and purified cellulose, pretreatment processes of lignocellulosic feedstocks are applied to decompose the complex cellulose-lignin-hemicellulose matrix, which facilitates access to isolated compounds. The influence of various autohydrolysis conditions, alkaline sulfite extraction and bleaching were evaluated in terms of extract yield, chemical profile and structural properties upon a solid fraction rich in cellulose. Among the treatments applied, autohydrolysis at 170 °C for 1 h followed by a bleaching step was the treatment that presented the best results in terms of cellulose purity (77.8%), crystallinity (73.4%), whiteness and glucose production by enzymatic hydrolysis, when compared with the non-treated fraction. The combination of autohydrolysis with a totally chlorine free bleaching step showed as a promising eco-friendliness alternative to obtain a white and solid fraction rich in cellulose, thus contributing to the valorization of this by-product.

About 95% of global hydrogen production is made by fossil fuels using different technologies which are all characterized by high energy consumption and high carbon emissions. Alternatively, more sustainable production methods, such as biological fermentation processes, are under study. Dark fermentation, also called acidogenesis, entails the transformation of a great variety of organic substances into a mixture of organic and inorganic products, as well as gases (H2 and CO2). In this study we tested an exhausted fermentation broth, derived after Clostridium fermentation for H2 production, as a biostimulant via foliar application in an intensive apple orchard. Two different doses were applied upon dilution of the broth in water (100 mL L−1 and 10 mL L−1), evaluating the main fruit quality parameters (fresh weight, fruit diameter, dry matter, firmness, soluble solid content, color lightness, DA index) in addition to macro- and micro-nutrients and heavy metals concentrations. Chemical characterization of the broth showed a high amount of low-MW polypeptides (Trp-Glu-Lys, Ile-Pro-Ile, Phe-Pro-Lys, His-Pro) and organic acids (formic acid, butyric acid, butanedioic acid); moreover, quantitative analyses of inorganic ions showed no heavy metal detection but high concentrations of nitrogen, phosphorus and potassium, compatible with use in agriculture. The fruit quality parameters showed significantly higher mean fruit weight compared to the untreated trees, as well as higher dry matter. No statistical differences were recorded among the treatments for fruit firmness, diameter and yield. Soluble solids content in both treatments were significantly lower than the controls, whereas the DA index mean values were higher in both treatments compared to the controls, indicating a delay in fruit ripening probably due to the high nitrogen broth concentration. Regarding the chemical analyses of fruits, no particular differences were found among the treatments, except for Fe, which showed a significantly higher amount upon treatment with the lower dose. As concerns leaves, no phytotoxic symptoms were detected in both treatments, making the described exhausted broth a candidate for its use as a plant biostimulant. Additional studies are needed to evaluate the ideal application dose, identify further action targets and implement appropriate strategies to concentrate the biostimulant active compounds.

Lactobacillus rhamnosus is a homofermentative probiotic strain that was previously demonstrated to grow on lignocellulosic-derived raw materials and to convert glucose into L-lactic acid (LA) with yields that vary between 0.38 and 0.97 g/g. Lactic acid is a key platform chemical, largely applied in different biotechnological fields (spanning from the pharmaceutical to the food sector) and also as a building block for the production of biodegradable polymers. In the present study, grape stalks were evaluated as sources of fermentable sugars for the growth of L. rhamnosus IMC501 and for the production of LA, since millions of hectoliters of wine are produced every year worldwide, generating a huge amount of waste. Although grape stalks are quite recalcitrant, the combination of a steam explosion pre-treatment with optimized two-step hydrolysis and commercial enzymes (Cellic-CTec2) allowed us to obtain a cellulose conversion efficiency of about 37% and to develop small-scale 2 L batch fermentation processes. Results successfully demonstrate that L. rhamnosus IMC501 can tolerate biomass-derived inhibitors and grow on grape stalk hydrolysate without the need for additional sources of nitrogen or other nutritional elements, and that the strain can convert all glucose present in the medium into LA, reaching the maximal theoretical yield.

Bioactive extracts are often the target fractions in bioprospecting, and halophyte plants could provide a potential source of feedstock for high-value applications as a part of integrated biorefineries. Tripolium pannonicum (Jacq.) Dobrocz. (sea aster) and Crithmum maritimum L. (sea fennel) are edible plants suggested for biosaline halophyte-based agriculture. After food production and harvesting of fresh leaves for food, the inedible plant fractions could be utilized to produce extracts rich in bioactive phytochemicals to maximize feedstock application and increase the economic feasibility of biomass processing to bioenergy. This study analyzed fresh juice and extracts from screw-pressed sea aster and sea fennel for their different phenolic compounds and pigment concentrations. Antioxidant and enzyme inhibition activities were also tested in vitro. Extracts from sea aster and sea fennel had phenolic contents up to 45.2 mgGAE/gDM and 64.7 mgGAE/gDM, respectively, and exhibited >70% antioxidant activity in several assays. Ethanol extracts also showed >70% inhibition activity against acetylcholinesterase and >50% inhibition of tyrosinase and α-glucosidase. Therefore, these species can be seen as potential feedstocks for further investigations.

Bioactive extracts are often the target fractions in bioprospecting, and halophyte plants could provide a potential source of feedstock for high-value applications as a part of integrated biorefineries. Tripolium pannonicum (Jacq.) Dobrocz. (sea aster) and Crithmum maritimum L. (sea fennel) are edible plants suggested for biosaline halophyte-based agriculture. After food production and harvesting of fresh leaves for food, the inedible plant fractions could be utilized to produce extracts rich in bioactive phytochemicals to maximize feedstock application and increase the economic feasibility of biomass processing to bioenergy. This study analyzed fresh juice and extracts from screw-pressed sea aster and sea fennel for their different phenolic compounds and pigment concentrations. Antioxidant and enzyme inhibition activities were also tested in vitro. Extracts from sea aster and sea fennel had phenolic contents up to 45.2 mgGAE/gDM and 64.7 mgGAE/gDM, respectively, and exhibited >70% antioxidant activity in several assays. Ethanol extracts also showed >70% inhibition activity against acetylcholinesterase and >50% inhibition of tyrosinase and α-glucosidase. Therefore, these species can be seen as potential feedstocks for further investigations.

Valuable products, including carotenoids, phenolic compounds, and pectin were obtained from granadilla peel using green technologies based on pressurized fluids. The processes of pressurized liquid extraction (PLE) and CO2-expanded ethanol (GXE) were evaluated to recover the carotenoids and phenolic compounds, while pressurized hot water extraction (PHWE) was evaluated to extract pectin from the granadilla peel. The results demonstrated that although PLE and GXE had no significant difference in the carotenoids yield and antioxidant activity of the extracts obtained, PLE was faster than GXE to achieve the highest extraction yield. The pectin yield obtained by PHWE was affected by the process temperature with the highest value obtained at 160 °C. Further studies are needed to characterize the chemical composition of the pectin obtained, but the present results enable establishing a biorefinery for the complete use of granadilla wastes (seeds and peel)., The authors thank the financial support of the Ministry of Education (MECESUP) through the Program Strengthening Featuring MECESUP-ANT 1999 (Attraction of Advanced Human Capital from Abroad short-term visits) and the FONDEQUIP EQM160073 Project of the National Agency for Research and Development (ANID) ex-National Commission for Scientific and Technological Research(CONICYT) of Chile. Renata Vardanegathanks Horizon 2020 MSCA grant agreement No 101062938 for the postdoctoral fellowship., info:eu-repo/semantics/publishedVersion

Tidal waste causes accumulation of seaweed and marine plants on coasts, resulting in an.eutrophication process and proliferation of insects, nematodes, and bacteria that negatively affect the beach ecosystem and local human economic activities. This work highlights the potential of beach wrack from the Andalusian Mediterranean coastline as cellulosic materials, in the frame of concepts such as waste management, revalorization, and reduction of hazardous chemicals. With this purpose, beach waste was harvested, washed with water, characterized, and subjected to chemical-free hydrothermal treatments. A central composite design was defined in order to relate the hydrothermal treatment conditions to the composition of the liquid and solid fractions. It was concluded that polynomial models encompassing linear, quadratic, and binary effect parameters reproduce the experimental results satisfactorily (e.g., R2 = 0.97–0.98 for saccharides released). As expected, severe conditions resulted in higher removal of hemicellulose, and of small amounts of lignin along with it, but at the expense of the yield. Results allowed us to choose high temperature (150 °C), short time (30 min) and low liquid/solid ratio (8) as a compromise solution, by which the yield and the outlet concentrations of glucose, xylose, and arabinose approached their optimal values. Although longer times grant further removal of non-fibrous materials, this small difference is compensated by energy savings and reduction on water consumption., ECOWAL Group, Molelular Biology and Biochemical Engineering Dpt. Universidad Pablo de Olavide

Producción Científica, Biogas-based biopolymer production represents an alternative biogas valorization route with potential to cut down plastic pollution and greenhouse gas emissions. This study investigated for the first time the continuous bioconversion of methane, contained in biogas, into poly(3-hydroxybutyrate) (PHB) by a mixed methanotrophic culture using an innovative high mass-transfer Taylor flow bioreactor. Following a hydrodynamic flow regime mapping, the influence of the gas residence time and the internal gas recirculation on CH4 abatement was assessed under non nutrient limiting conditions. Under optimal operational conditions (gas residence time of 60 min and internal gas recycling ratio of 17), the bioreactor was able to support a CH4 removal efficiency of 63.3%, a robust CH4 elimination capacity (17.2 g-CH4 m-3h-1) and a stable biomass concentration (1.0 g L-1). The simultaneous CH4 abatement and PHB synthesis was investigated under 24-h:24-h nitrogen feast/famine continuous operation. The cyclic nitrogen starvation and the Taylor flow imposed in the bioreactor resulted in a relatively constant biomass concentration of 0.6 g L-1 with PHB contents ranging from 11 to 32% w w-1 (on a dry weight basis), entailing an average PHB productivity of 5.9 g-PHB m-3 d-1 with an associated PHB yield of 19.8 mg-PHB g-CH4-1. Finally, the molecular analysis of the microbial population structure indicated that type II methanotrophs outcompeted non-PHB accumulating type I methanotrophs, with a heterotrophic-methanotrophic consortium enriched in Methylocystis, Hyphomicrobium, Rubinisphaeraceae SH PL14 and Pseudonocardia., Ministerio de Ciencia, Innovación y Universidades (project RTI2018-0-096441-B-I00), Erasmus+ International Master of Science in Environmental Technology and Engineering (project 2017-1957/001-001-EMJMD), Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (grants CLU 2017-09 and UIC 315)

International audience; This paper aims to investigate the effect of extrusion at high solid loading on corn stover (CS) properties and its enzymatic hydrolysis. This biomass was extruded under different screw speeds and different solid loadings and the impact of these parameters on physicochemical properties was evaluated. It was found that lignocellulosic components were not significantly affected by the pretreatment, while surface area increased with solid loading and rotation speed. Different enzyme cocktails were used for the enzymatic hydrolysis of extruded and untreated CS. Overall, mild twin-extrusion enhanced the enzymatic hydrolysis of corn stover through an increase in glucose and xylose yields by 134-212% and 214-294% respectively when using T. longibrachiatum cellulase. The highest sugar content was obtained from CS extruded under 400 g total solids (TS) per liter and 200 rpm. The energy efficiency of the pretreatment was also assessed and was found to be maximal at 400 gTS/L and 200 rpm.

Glycerol, the “co-product” in the biodiesel process, can be considered as a raw material to expand a biorefinery scheme. Selective reductions and oxidations and steam reforming of glycerol were studied to produce added-value chemicals and energetic compounds, and also to show a possible integration of processes into a biorefinery framework. Selective reductions of glycerol in gas phase produced: i) propylene glycol on Cu-Ce/Al2O3, reaching 99.8% conversion and 83.2% selectivity to propylene glycol; and ii) ethylene glycol on Ni/SiO2, achieving 100% conversion and 91% selectivity to ethylene glycol in the liquid fraction. These reduction reactions demand hydrogen, which can also be obtained by steam reforming of glycerol using Ni/Al2O3 promoted by adding compounds as Ce, Co, Mg, and Zr; the steam reforming also produced carbon oxides and methane, being possible to use the syngas (hydrogen plus carbon monoxide) and methane as energetic compounds and carbon dioxide to carbonylation. Selective oxidations of glycerol in liquid phase produced: i) dihydroxyacetone on Pt/K-FER, being the first active and selective monometallic catalyst for this transformation, improving the catalytic behavior by using Pt-Bi/K-FER, reaching 75.9% conversion and 93.9% selectivity to dihydroxyacetone; and ii) lactic acid on Cu/Al2O3, obtaining 99.8% conversion and 86.5% selectivity to lactic acid. From the strong link with the productive sector, one pilot plant to produce 100 t/y of propylene glycol from glycerol but versatile to also obtain acetol and/or ethylene glycol is in the final building stage, and another one for reforming glycerol to produce the hydrogen demanded for those reduction processes was finished. Consequently, glycerol was converted to propylene glycol, ethylene glycol, hydrogen, dihydroxyacetone, lactic acid, syngas, carbon dioxide, and methane; therefore, the possible integration of the corresponding processes allows consider the co-product of biodiesel as a compound to expand a biorefinery scheme.

10 páginas.- 5 figuras.- 2 tablas.- 50 referencias.- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acssuschemeng.2c01274, Innovative schemes for lignocellulosic biomass refining could optimize the chemical use and biomass conversion efficiency, providing diversified biorefinery products. A new biorefinery scheme used mild alkaline-sulfite chemithermomechanical processing to pretreat sugarcane bagasse, producing highly digestible solids and diluted lignosulfonates in the black pretreatment liquor. Most of the glucan and xylan contained in the pretreated solids were converted into monosaccharides by saccharification with commercial enzymes. The undigested biomass solids remaining from the saccharification process were recycled with the existing alkaline-sulfite black pretreatment liquor. The optimized reaction conditions (159 degrees C and 13% NaOH amendment in the liquor) enhanced the lignosulfonate concentration from 7.1 +/- 0.3 to 33.5 +/- 0.7 g/L. Mass balance for the process indicates that most of the original sugarcane bagasse lignin were split into lignosulfonates contained in the resulfonation liquor (57.3%) and in the enzymatic hydrolysate (16.2%). 2D-NMR analysis of a lignosulfonate fraction recovered by ultrafiltration confirmed that approximately 9-10% of all beta-O-4' alkyl-aryl ether substructures were alpha-sulfonated. The combined chemical characteristics of the prepared lignosulfonate suggested its suitability for use in several lignosulfonate applications., This work was supported by FAPESP (grant number 2019/25867-3), CNPq (grant number 308570/2017-0), and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (CAPES)-Finance Code 001. J.R. and J.C.d.R. were funded by MCIN/AEI/10.13039/501100011033, by "ERDF A way of making Europe" (project PID2020-118968RB-I00), and by the Regional Andalusian Government, Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades/FEDER (project P20-00017).

Biorefinery is pivotal to the sustainability of modern chemical industry. However, since biomass is oxygen-enriched, new and green chemical strategies are required for expanding the biomass derived chemical space. In this work, synthesis of natural products dihydrocapsaicin and dihydrocapsiate was achieved exclusively from lignocellulosic platform chemicals. Natural products dihydrocapsaicin and dihydrocapsiate were synthesized exclusively from lignocellulosic platform chemicals, using furfural (from hemicellulose) and methyl isopropyl ketone (from cellulose) through aldol condensation-hydrolysis-hydrodeoxygenation to synthesize 8-methylnonanoic acid and then combined with vanillin derivates (from lignin). This synthesis demonstrates the feasibility of constructing natural products entirely from renewable biomass platform through green processes. The utilization of inherent functional groups of biomass demonstrates their potential to open up chemical space.

5 figures, 7 tables.-- Supplementary information available., The acid-free hydrothermal microwave–assisted selective scissoring (Hymass concept) of cellulosic substrates is gaining keen interest in the field of materials science. Besides, implementing catalytic methodologies to upgrade side streams produced during this process could contribute to better, holistic utilisation of the starting feedstock. This work depicts a zero-waste biorefinery concept based on cellulose defibrillation from almond hulls using various hydrotreatment technologies (hydrogenation and hydrodeoxygenation) for downstream processing on a ruthenium catalyst. Therein, the hemicellulose separated from the biomass preconditioning step was converted into sugar alcohols and/or marketable polyols with a relatively high yield (47.4%) by hydrolytic hydrogenation (437 K, 3h, 5.0 MPa H2). Meanwhile, a family of bioactive compounds (3-hydroxypyridines) could be directly extracted from the hydrolysate stream derived from microwave digestion, along with an energy carrier that was chemically stabilised (503 K, 60 min, 4.0 MPa H2) to obtain fuel additives (diethyl succinic acid, DES) and/or fuel intermediates., The authors are grateful for the financial support from the Spanish Ministry of Economy and Competitiveness (MINECO, Project ENE2017-83854-R) and the I+D+i project PID2020-115053RB-I00, funded by MCIN/AEI/10.13039/501100011033. J.R. is grateful to the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva Incorporación (JdC-I) fellowship (Grant Number: IJC2018-037110-I) awarded.

Microbial production of 2,3-butanediol (BDO) has received considerable attention as a promising alternate to fossil-derived BDO. In our previous work, BDO concentration >100 g/L was accumulated using brewer’s spent grain (BSG) via microbial routes which was followed by techno-economic analysis of the bioprocess. In the present work, a life cycle assessment (LCA) was conducted for BDO production from the fermentation of BSG to identify the associated environmental impacts. The LCA was based on an industrial-scale biorefinery processing of 100 metric tons BSG per day modeled using ASPEN plus integrated with pinch technology, a tool for achieving maximum thermal efficiency and heat recovery from the process. For the cradle-to-gate LCA, the functional unit of 1 kg of BDO production was selected. One-hundred-year global warming potential of 7.25 kg CO2/kg BDO was estimated while including biogenic carbon emission. The pretreatment stage followed by the cultivation and fermentation contributed to the maximum adverse impacts. Sensitivity analysis revealed that a reduction in electricity consumption and transportation and an increase in BDO yield could reduce the adverse impacts associated with microbial BDO production.

published

The spread of heavy metal(loid)s at soil-food crop interfaces has become a threat to sustainable agricultural productivity, food security, and human health. The eco-toxic effects of heavy metals on food crops can be manifested through reactive oxygen species that have the potential to disturb seed germination, normal growth, photosynthesis, cellular metabolism, and homeostasis. This review provides a critical overview of stress tolerance mechanisms in food crops/hyperaccumulator plants against heavy metals and arsenic (HM-As). The HM-As antioxidative stress tolerance in food crops is associated with changes in metabolomics (physico-biochemical/lipidomics) and genomics (molecular level). Furthermore, HM-As stress tolerance can occur through plant-microbe, phytohormone, antioxidant, and signal molecule interactions. Information regarding the avoidance, tolerance, and stress resilience of HM-As should help pave the way to minimize food chain contamination, eco-toxicity, and health risks. Advanced biotechnological approaches (e.g., genome modification with CRISPR-Cas9 gene editing) in concert with traditional sustainable biological methods are useful options to develop ‘pollution safe designer cultivars’ with increased climate change resilience and public health risks mitigation. Further, the usage of HM-As tolerant hyperaccumulator biomass in biorefineries (e.g., environmental remediation, value added chemicals, and bioenergy) is advocated to realize the synergy between biotechnological research and socio-economic policy frameworks, which are inextricably linked with environmental sustainability. The biotechnological innovations, if directed toward ‘cleaner climate smart phytotechnologies’ and 'HM-As stress resilient food crops', should help open the new path to achieve sustainable development goals (SDGs) and a circular bioeconomy.

Lignin is a remarkable natural polyphenol that provides trees with physical and (bio-)chemical resistance, as well as the ability to reach considerable heights. Lignin is also intrinsically circular with slow biodegradability, thereby serving as a carbon source for soils. There is a growing interest in using industrial lignin as an environmentally and economically beneficial material. However, most of the industrially produced lignin is still used as a cost-efficient energy source by the forestry sector. To efficiently redirect the use towards material applications and to avoid the end-of-life problems connected to traditional plastics, there is an imminent need and opportunity to include circularity as an important design parameter. In this review, we critically assess opportunities and obstacles for lignin as a component in circular materials, as guided by life cycle assessment and benchmarking to best practices in materials science and engineering, e.g., circularity “by design”. We cover and reflect on recent and emerging advances in nanotechnology and materials science that showcase how lignin can contribute to carbon fixation as a viable alternative to its combustion in the pulping processes. We argue that, with adequate considerations, lignin has the potential to enable the development of new circular biobased materials that do not cause accumulation of environmentally persistent waste, and are equipped with attractive functionalities and performance for the benefit of a sustainable society.

Corn cob is an abundant agricultural residue worldwide, with high potential and interesting composition, and its valorization still needs to be studied. Selectively fractionating its structural components (hemicellulose, cellulose, and lignin), value-added products can be produced, eliminating waste. In this work, integrated fractionation approaches were developed and evaluated. First, an organosolv process was optimized (ethanol:water, 50:50, w/w). Then, as a comparative method, alkaline delignification (using NaOH, 1-2%) was also studied. The organosolv process allowed a significant delignification of the material (79% delignification yield) and, at the same time, a liquid phase containing a relevant concentration (14.6 g/L) of xylooligosaccharides (XOS). The resulting solid fraction, rich in cellulose, showed an enzymatic digestibility of 90%. The alkaline process increased the delignification yield to 94%, producing a solid fraction with a cellulose enzymatic digestibility of 83%. The two later techniques were also used in a combined strategy of hydrothermal processing (autohydrolysis) followed by delignification. The first allowed the selective hydrolysis of hemicellulose to produce XOS-rich hydrolysates (26.8 g/L, 67.3 g/100 g initial xylan). The further delignification processes, alkaline or organosolv, led to global delignification yields of 76% and 93%, respectively. The solid residue, enriched in glucan (above 75% for both combined processes), also presented high enzymatic saccharification yields, 89% and 90%, respectively. The fractionation strategies proposed, and the results obtained are very promising, enabling the integrated upgrading of this material into a biorefinery framework. info:eu-repo/semantics/publishedVersion

The evaluation of macroalgae as a new raw material for diverse bioprocesses is of great interest due to their fast growth rate and low environmental impact. Lactic acid has a high value in the bio-based industry and is mainly produced via fermentation. The anaerobic lactic acid fermentation of Kappaphycus alvarezii hydrolysates using the high-producing strain Lactobacillus pentosus was evaluated for detoxified and non-treated hydrolysates prepared from concentrated algal biomass and dilute acid solution mixtures. A novel hydrolysate detoxification procedure, combining activated charcoal and over-liming, for 5-hydroxymethylfurfural (HMF) removal was used. L. pentosus was found to successfully ferment detoxified and untreated hydrolysates produced in up to 30% and 20% w/v solutions, respectively. Significant production rates (1.88 g/L.h) and short lag phases were achieved in bioreactor fermentation operating at 37 °C and pH 6 with 150 rpm impeller velocity. A 0.94 g/g yield from fermentable sugars (galactose and glucose) was achieved, indicating that K. alvarezii could be used as a raw material for lactic acid production, within the context of Third Generation (3G) biorefinery.

Decarbonization of the aviation sector relies on deployment of sustainable aviation fuels (SAF) at commercial scale. Hydrothermal liquefaction (HTL) has been recognized as a promising technology to help supply the increasing projected SAF demand. High availability of agro-industrial residues, combined with a well-established biorefinery system, makes the sugarcane industry in Brazil a good option for HTL technology deployment. Moreover, challenges regarding the economic feasibility of SAF from HTL could be partially addressed by the RenovaBio policy, a market-driven incentive mechanism of carbon credits implemented in Brazil. This study investigated both the techno-economic and life cycle assessment of SAF production from sugarcane lignocellulosic residues, considering HTL integrated to a first-generation ethanol distillery and a HTL stand-alone facility. The evaluated scenarios showed great climate mitigation potential, reaching a reduction of up to 73–82% when compared to fossil jet fuel. The minimum fuel selling price of SAF at 15.4 USD/GJ indicated potential of economic competitiveness with fossil jet fuel in the best integrated scenario. The economic benefits obtained from carbon credits are not enough to enable feasibility of HTL in the stand-alone scenarios, even with carbon prices projected at 125 USD/tonne CO2-eq avoided.

We found an effective catalytic consortium capable of converting glucose to 5-hydroxymethylfurfural (HMF) in high yields (50%). The reaction consists of a consortium of a Lewis acid (NbCl5) and a Brønsted acid (p-sulfonic acid calix[4]arene (CX4SO3H)), in a microwave-assisted reactor and in a biphasic system. The best result for the conversion of glucose to HMF (yield of 50%) was obtained with CX4SO3H/NbCl5 (5 wt%/7.5 wt%), using water/NaCl and MIBK (1:3), at 150 °C, for 17.5 min. The consortium catalyst recycling was tested, allowing its reuse for up to seven times, while maintaining the HMF yield constant. Additionally, it proposed a catalytic cycle by converting glucose to HMF, highlighting the following two key points: the isomerization of glucose into fructose, in the presence of Lewis acid (NbCl5), and the conversion of fructose into HMF, in the presence of CX4SO3H/NbCl5. A mechanism for the conversion of glucose to HMF was proposed and validated.

Salt-tolerant plants, also known as halophytes, could provide a novel source of feedstock for biorefineries. After harvesting fresh shoots for food, the lignified fraction of Salicornia ramosissima J. Woods could be used to produce bioactive botanical extracts for high-value industries such as nutraceuticals, cosmetics, and biopharmaceuticals. The residual fraction after extraction can be further used for bioenergy or lignocellulose-derived platform chemicals. This work analysed S. ramosissima from different sources and growth stages. After pre-processing and extractions, the obtained fractions were analysed for their contents of fatty acids, pigments, and total phenolics. Extracts were also evaluated for their in vitro antioxidant properties and inhibitory effect towards enzymes related to diabetes, hyperpigmentation, obesity, and neurogenerative diseases. The ethanol extract from the fibre residue and the water extract from completely lignified plants showed the highest concentration of phenolic compounds along with the highest antioxidant potential and enzyme-inhibitory properties. Hence, they should be further explored in the context of biorefinery. Fundo Azul (FA-05-2017-028) info:eu-repo/semantics/publishedVersion

The rapid increases in fuel ethanol demand and food security concerns have driven the need for diverse feedstocks in the ethanol production process. Energy cane is an energy crop that is an ideal sustainable biofuel feedstock. The present study evaluated ethanol production of the juice and bagasse of two newly developed energy cane clones, TByEFC08-0035 and TByEFC10-0004. The results of the chemical composition analyses of the juice and bagasse samples revealed that the two energy cane clones contained high contents of both sucrose (15.36–17.95%) and fiber (13.44–24.16%). The maximum ethanol concentrations from the juice on a laboratory scale (87.10 g/L) and on an agronomic scale (1211.76 kg/ha) were recorded for TByEFC10-0004 fermented with a new isolate Kluyveromyces marxianus SJT83, whereas the maximum ethanol concentrations from bagasse on a laboratory scale (9.81 g/L) and on an agronomic scale (790.68 kg/ha) were reached with TByEFC08-0035 fermented with Scheffersomyces shehatae TTC79. The total ethanol yields from the juice and bagasse samples per cultivation area of both energy cane clones were in the range 1294.23–1469.14 kg/ha, being 1.70–1.93 and 1.08–1.23 times higher than the control energy cane Biotec2 variety and the commercial sugar cane Khon Kaen3 variety, respectively. This study revealed the potential of the energy cane clones TByEFC08-0035 and TByEFC10-0004 currently being developed as sugar and lignocellulose substrates for first- and second-generation ethanol industry applications.

Microalgae represent a promising solution in addressing the impacts associated with the current agricultural and manufacturing practices which are causing irreparable environmental damage. Microalgae have considerable biosynthetic potential, being a rich source of lipids, proteins, and high-value compounds. Under the scope of the H2020-BBI MULTI-STR3AM project, an innovative large-scale production system of valuable commodities for the food, feed, and fragrance sectors is being developed on the basis of microalgae, reducing costs, increasing the scale of production, and boosting value chain sustainability. In this work, we aimed to create a process model that can mimic an industrial plant to estimate mass and energy balances, optimize scheduling, and calculate production costs for a large-scale plant. Three autotrophic microalgae strains (Nannochloropsis sp., Dunaliella sp. and Spirulina sp.) were considered for this assessment, as well as the use of locally sourced CO2 (flue gas). The developed process model is a useful tool for obtaining the data required for techno-economic analysis (TEA) and life cycle assessment (LCA) of industrial biorefinery-based processes. Nannochloropsis sp. was the most economic option, whereas Dunaliella sp. was the most expensive strain to produce due to its lower productivity. Preliminary environmental assessments of the climate change impact category revealed that water recirculation and the use of flue gas could lead to values of 5.6, 10.6, and 9.2 kgCO(2eq)center dot kg(AFDW)(-1) for Nannochloropsis sp., Dunaliella sp., and Spirulina sp., respectively, with electricity and NaCl as the main contributors. The obtained data allow for the quantification of the production costs and environmental impacts of the microalgal biomass fractions produced, which will be fundamental for future comparison studies and in determining if they are higher or lower than those of the replaced products. The process model developed in this work provides a useful tool for the evaluation and optimization of large-scale microalgae production systems. info:eu-repo/semantics/publishedVersion

This study evaluates the production of lignin bioactive extracts from sugarcane bagasse (SCB) and straw (SCS) alkaline black liquors using greener precipitating agents (methane sulfonic acid (MSA), formic acid (FA) and lactic acid (LA)) as replacers of sulfuric acid (SA), the most common one used in industry. Results showed that the highest precipitation yield was achieved by LA when applied to SCB (14.5 g extract/g SCB). Lignin SCB extracts were similar in composition in terms of total carbohydrates (61–70 %), lignin (22–30 %) and inorganics (1.6–2.6 %). Regarding the SCS extracts, similar yields were obtained among all extracts, however; differences in composition were observed between SA and greener precipitating agents, particularly in terms of sugar content. All extracts exhibited radical scavenging activity; overall the extracts were more effective in the scavenging of ABTS radical. FA was the most promising alternative to SA to recover lignin bioactive extracts. This work suggests organic acids as good candidates for obtaining valuable extracts from alkaline pulping of SCB and SCS instead of the conventional sulfuric acid, thus suggesting a green solution for this biomass valorization.

International audience; In the development of botanical insecticides, the availability of a certifiable raw material and the guarantee of a stable biological efficacy over time are crucial factors. Sextonia rubra is one of the main tree species exploited by the Guianese forestry industry, and the valorization of the large volumes of sawmills residues available would represent an opportunity for the sustainable development of bioactive products in a biorefinery perspective. In this work, we studied the variability of the quality of S. rubra sawdust according to its origin and investigated the bioactivity of its extracts against Ae. aegypti mosquitoes. We evidenced homogeneous physico-chemical properties (particle size and NIRS profiles) of S. rubra sawdusts independently of the sawmill of origin, thus highlighting the consistency of the raw material before extraction. The amount of the γ-lactones rubrenolide and rubrynolide was measured in 12 extracts of S. rubra by quantitative NMR (qNMR). GLM regression indicated significant correlation between these values and larval mortality (adj-R2 0.93) for the extracts tested at 30 µg/ml. Additionally, a 48-h DL50 of 18.6 µg/ml was obtained for a S. rubra reference extract. While sawdust underwent chemical changes during the 10 months of storage, as shown by NIRS and qNMR analyses, we observed no significant impact on larval mortality for the extracts tested at 30 µg/ml. A stability of 9-months was also observed for a crude extract stored at room temperature. Sawmill residues of S. rubra thus appear to be suitable raw material for the production of significant quantities of wood extracts containing larvicidal compounds against Ae. aegypti. Their stability over time also makes it possible to consider production routes that could be transferred to an industrial scale.

Pinus pinea nuts are commercial relevant Mediterranean edible forest nuts, with an increasing production and market value, whose industrial processing yields a lignocellulosic by-product, the pine nut shells, currently only used for combustion. Little research has been done on pine nut shells that could support a value-added application for this residue. This work studies for the first time the production of oligosaccharides by autohydrosis, and aims at an integrated upgrade within the biorefinery framework. Autohydrolysis was explored in the temperature range between 150 and 230 °C (corresponding to severity factors 2.13–4.63). Oligosaccharides, mainly xylo-oligosaccharides (95% of the total), were the key soluble products, reaching 28.7 g/100 g of xylan of the feedstock at the optimal conditions (log R0 4.01). Other products were monosaccharides and phenolic compounds that reached 7.8 and 4.7 g/L, respectively, under the most severe conditions. The stability of the oligosaccharides at different temperatures (room, 37 °C and 100 °C) and pH (between 1 and 11) grant them significant market potential in the food and pharma sectors. The pre-treated pine nut shells by autohydrolysis presented an improved, although low, enzymatic digestibility (14%), and an improved high-heating value, therefore advising their further valorization by thermochemical pathways.

The transition towards a circular bioeconomy (CBE) in the European Union is not without contestation. In particular, research has highlighted potential trade-offs of the large-scale production of bio-resources, for instance with environmental quality goals. To date, however, it remains underexplored in the CBE literature how controversies develop throughout a transition process. To address this gap, this paper explores where controversies are situated in a transition, how they change throughout, and how they influence the transition process. First, we suggest that controversies can be situated on and between different system layers within a transition. Second, we offer an explanation of how controversies evolve, as actors confirm, integrate, disintegrate and polarize underlying storylines. Third, these controversies can have both productive and unproductive outcomes while they unfold throughout a transition. We illustrate this understanding with the example of biorefineries as CBE key technology and discuss a research agenda on controversies in sustainability transitions.

Microalgae have been evaluated as promising resource for biodiesel production, but algal biofuel production is not yet commercially viable, which reflects the high energy costs linked with cultivation, harvesting, and dewatering of algae. As crude oil processing declines, microalgae biorefineries are being considered for producing bioactives such as enzymes, proteins, omega-3 oils, pigments, recombinant products, and vitamins, to offset the costs of biofuel production. We believe that producing algal bioactives through advanced manufacturing pathways, encompassing a biorefinery approach, would be effective, profitable, and economical.

Wastewater is of general concern for environmental sustainability. At the industrial level, carbon-laden aqueous streams must be treated and should be valorized to reduce environmental and economic concerns. Lignocellulosic biomass processing (such as hydrolysis, pyrolysis, and hydrothermal liquefaction) results in secondary aqueous streams in which a high fraction of the initial carbon content of the biomass is virtually lost; food industry (like breweries and cheese factories) produces streams with a variety of organic load and salinity, which may complicate conventional valorization treatments; biodiesel production leads to glycerol excess in the market, which needs to be valorized. Among other alternatives, aqueous phase reforming (APR) has been proposed as a process driven at relatively mild conditions, able to convert oxygenated molecules into hydrogen. Despite its potential, APR has commonly been investigated with model compounds, and a systematic study on the possible fields of application of this technology is lacking. In the present review, the study of the available literature was focused on the valorization of complex feedstocks, such as real waste streams or synthetic mixtures, showing the outcome derived from laboratory-scale experiments. The results were critically discussed, pointing out the present limitations for the full development of this process and its application to the industrial scale. Despite the challenges of APR, its potential is noteworthy for the development of a circular low-waste economy.

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Lignocellulosic biomass generated from different sectors (agriculture, forestry, industrial) act as biorefinery precursor for production of second-generation (2G) bioethanol and other biochemicals. The integration of various conversion techniques on a single platform under biorefinery approach for production of biofuel and industrially important chemicals from LCB is gaining interest worldwide. The waste generated on utilization of bio-resources is almost negligible or zero in a biorefinery along with reduced greenhouse gas emissions, which supports the circular bioeconomy concept. The economic viability of a lignocellulosic biorefinery depends upon the efficient utilization of three major components of LCB—cellulose, hemicellulose and lignin. The heterogeneous structure and recalcitrant nature of LCB is main obstacle in its valorization into bioethanol and other value-added products. The success of bioconversion process depends upon methods used during pre-treatment, hydrolysis and fermentation processes. The cost involved in each step of the bioconversion process affects the viability of cellulosic ethanol. The lignocellulose biorefinery has ample scope, but much-focused research is required to fully utilize major parts of lignocellulosic biomass with zero wastage. The present review entails lignocellulosic biomass valorization for ethanol production, along with different steps involved in its production. Various value-added products produced from LCB components were also discussed. Recent technological advances and significant challenges in bioethanol production are also highlighted in addition to future perspectives. Graphical abstract

Microbial electrosynthesis (MES) for bioelectro carbon dioxide (CO2) recycling is an interesting and sustainable opportunity to exploit off gases from industrial facilities and convert them into valuable energy sources. In the present study, a two-step process based on coupling a bioelectrochemical system (BES) and heterotrophic microalgae Auxenochlorella protothecoides is proposed to convert carbon dioxide into a biodiesel compatible oil. The MES effluent was further processed in a heterotrophic microalgae batch reactor, where the acetate previously synthesized from CO2 was converted into bio-oil in a subsequent, extraction-free step. Two MES reactors were operated in batch mode at an applied cathodic potential of 0.8 V vs. SHE (standard hydrogen electrode) for 95 days. The system reached a concentration of up to 13 g L 1 of acetate (at a maximum production rate of 0.29 g L 1 d 1). Microbial community analysis revealed the presence of Clostridium spp. in both reactors. In a second stage, the effluent from the biocathode was transferred to microalgae reactors containing A. protothecoides to assess oil production. The bio-oil content was up to 22% w/w (dry weight), sufficient to further explore the feasibility of microalgae-to-oil recovery in the future. According to our estimations, 7.59 kg CO2 can be converted into 1 kg acetate, which can be used to grow heterotrophically 1.11 kg dry algae; an overall balance of 0.03 kg bio-oil produced per kg CO2 captured was assessed. The oil obtained can be further processed to produce a biodiesel compatible with EU requirements for biofuels This research was funded by the Spanish Ministry of Science through the grant RTI2018-098360-B-I00 and the Agency for Business Competitiveness of the Government of Catalonia (ACCIO) through the DigesTake Project (COMRDI16-1-0061). E. ´ P.-V. is grateful for the Research Training grant from the University of Girona (IFUdG2018/52). S. P. is a Serra Hunter ´ Fellow (UdG-AG-575) and acknowledges the funding from the ICREA Acad`emia award. LEQUiA and Ecoaqua have been recognized as consolidated research groups by the Catalan Government with codes 2017-SGR-1552 and 2017SGR-548, respectively

In the current global scenario, the world is under a serious dilemma due to the increasing human population, industrialization, and urbanization. The ever-increasing need for fuels and increasing nutritional problems have made a serious concern on the demand for nutrients and renewable and eco-friendly fuel sources. Currently, the use of fossil fuels is creating ecological and economic problems. Microalgae have been considered as a promising candidate for high-value metabolites and alternative renewable energy sources. Microalgae offer several advantages such as rapid growth rate, efficient land utilization, carbon dioxide sequestration, ability to cultivate in wastewater, and most importantly, they do not participate in the food crop versus energy crop dilemma or debate. An efficient microalgal biorefinery system for the production of lipids and subsequent byproduct for nutraceutical applications could well satisfy the need. But, the current microalgal cultivation systems for the production of lipids and nutraceuticals do not offer techno-economic feasibility together with energy and environmental sustainability. This review article has its main focus on the production of lipids and nutraceuticals from microalgae, covering the current strategies used for lipid production and the major high-value metabolites from microalgae and their nutraceutical importance. This review also provides insights on the future strategies for enhanced microalgal lipid production and subsequent utilization of microalgal biomass. Graphical abstract

In recent times, biohydrogen production from microalgal feedstock has garnered considerable research interests to sustainably replace the fossil fuels. The present work adapted an integrated approach of utilizing deoiled Scenedesmus obliquus biomass as feedstock for biohydrogen production and valorization of dark fermentation (DF) effluent via biomethanation. The microalgae was cultivated under different CO2 concentration. CO2-air sparging of 5% v/v supported maximum microalgal growth and carbohydrate production with CO2 fixation ability of 727.7 mg L−1 d−1. Thereafter, lipid present in microalgae was extracted for biodiesel production and the deoiled microalgal biomass (DMB) was subjected to different pretreatment techniques to maximize the carbohydrate recovery and biohydrogen yield. Steam heating (121 °C) in coherence with H2SO4 (0.5 N) documented highest carbohydrate recovery of 87.5%. DF of acid-thermal pretreated DMB resulted in maximum H2 yield of 97.6 mL g−1 VS which was almost 10 times higher as compared to untreated DMB (9.8 mL g−1 VS). Subsequent utilization of DF effluent in biomethanation process resulted in cumulative methane production of 1060 mL L−1. The total substrate energy recovered from integrated biofuel production system was 30%. The present study envisages a microalgal biorefinery to produce biohydrogen via DF coupled with concomitant CO2 sequestration.

A pretreatment process is a preliminary stage to alter the recalcitrant structure of lignocellulosic biomass for enhancing its digestibility. An evaluation of the energy consumption and the environmental restrictions of the pretreatment step is required to develop a feasible eco-friendly process for industrial implementation. In this study, a combined alkaline-mechanical fractionation of rice straw for fermentable sugar (FS) production was developed with the objectives of i) evaluating energy efficiency and ii) addressing the sustainability of technology. The maximum fermentable sugar production was 0.54 kg/kg rice straw with an enzymatic hydrolysis efficiency of 97.34%. Furthermore, the results indicated that the pretreatment by 5% NaOH followed by mechanical size reduction provided the highest energy efficiency of 0.35 kg of FS/kWh with 94.44% glucose recovery, which also provided the lowest waste generation of less than 0.1 kg of waste/kg FS. These experimental results suggest that the combined alkaline-mechanical fractionation could effectively increase total FS yields and could be a promising pretreatment technology for an eco-friendly and sustainable pretreatment process integrated into a biorefinery platform.

The increasingly severe environmental pollution and energy shortage issues have demanded the production of renewable and sustainable biofuels to replace conventional fossil fuels. Lignocellulosic (LC) biomass as an abundant feedstock for second-generation biofuel production can help overcome the shortcomings of first-generation biofuels related to the “food versus fuel” debate and feedstock availability. Embracing the “circular bioeconomy” concept, an integrated biorefinery platform of LC biomass can be performed by employing different conversion technologies to obtain multiple valuable products. This review provides an overview of the principles and applications of thermochemical processes (pyrolysis, torrefaction, hydrothermal liquefaction, and gasification) and biochemical processes (pretreatment technologies, enzyme hydrolysis, biochemical conversion processes) involved in LC biomass biorefinery for potential biofuel applications. The engineering perspective of LC biofuel production on separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP) were also discussed.

The present study demonstrates the feasibility of a two-phase biorefinery process applied to waste substrates producing ethanol rich effluents. The process includes a dark fermentation step followed by photo fermentation and it is able to optimize hydrogen production from waste biomass. The study was conducted using winery wastewater as feedstock. The results indicate that no additional treatments are required when an appropriate dilution of the initial waste is applied. Microbial consortia contained in the winery wastewater promoted a fermentative ethanol pathway. The ethanol rich effluent was converted into hydrogen by phototrophic microorganisms. Despite the presence of inhibiting compounds, the adoption of a mixed phototrophic culture allowed to obtain good results in terms of hydrogen production. Specifically, up to 310 mLH2 gCODconsumed−1 were obtained in the photo fermentative stage. The effectiveness of ethanol rich dark fermentation effluents for hydrogen production enhancement was demonstrated. Noteworthy, polyhydroxybutyrate was also produced during the experiments. The work faces two of the major challenges in the sequential dark fermentation and photo fermentation technology applied to real waste substrates: the minimization of pre-treatments and the enhancement of the hydrogen production yields using ethanol rich DFEs.

Over the last few years, a paradigm shift has emerged towards a circular economy that seeks to return to the process as many material/energy flows as possible to increase the sustainability of products, reducing waste and pollution. The citrus industry is not an exception hence one way to apply this approach is through the re-use of certain outflows to produce bioproducts and bioenergy. The objectives of this work are, first, to present the environmental profile of lemons and derivatives in Argentina through the Life Cycle Assessment methodology, and second, to unveil environmental implications of shifting from traditional industries to biorefineries which apply circular economy principles. To do that, the current production scheme for manufacturing essential oil, concentrated juices and dehydrated peel is studied (baseline), to then consider new products, i.e., ethanol, limonene and biogas, through several scenarios with different degrees of biogas recirculation. We find that for lemon production, agrochemicals represent more than 60% in eleven of the twelve impact categories. For processed products, agriculture contributes with more than 50% in all the categories, followed by natural gas and electricity consumption. It also results that adding value to wastes and implementing circular economy strategies do not ensure a better environmental performance of the system. When comparing the current situation with biorefinery schemes, the most promising scenario is the one in which all the biogas is used to produce electricity, causing the least impact in eight of the twelve categories analyzed.

12 Páginas.-- 3 Figuras.-- 3 Tablas, Olive mill solid waste (OMSW) is an agro-industrial waste that has a high content of recalcitrant lignocellulose, which can adversely affect the environment. This study aimed to evaluate the phenol and lignin removal and the enzyme activity involved in the biological pre-treatment of OMSW supplemented with aquaculture sludge (AS) as an external nitrogen source by Anthracophyllum discolor. The highest lignin removal and enzymatic activity performance was obtained in the mixture of OMSW and AS prepared at a C/N ratio 45. In these conditions, the pre-treatment could remove 66% of lignin and 68% of phenols in the solid phase and 56% of phenols in the liquid phase and the maximum activity of laccase, manganese peroxidase and manganese independent peroxidase were of 10, 289 and 75 U L−1 in 25, 30, and 15 days of pre-treatment, respectively. These results propose that the addition of AS as a co-substrate for adjusting the C/N ratio allows a 41 and 141% increase in lignin removal and manganese peroxidase activity respectively, enabling the treatment of both OMSW and AS wastes and the possible recovery of an enzymatic extract of biotechnological interest., Fondecyt Project No. 1191230, Agencia Nacional de Investigación y Desarrollo de Chile, ANID.