Search

Lignin, the most abundant aromatic biopolymer on Earth, is often considered a biorefinery by-product, despite its potential to be valorized into high-added-value chemicals and fuels. In this work, an integrated superstructure-based optimization model was set up and optimized using mixed-integer non-linear programming for the conversion of technical lignin to three main biobased products: aromatic monomers, phenol-formaldehyde resins, and aromatic aldehydes/acids. Several alternative conversion pathways were simultaneously compared to assess the profitability of lignins-based processes by predicting the performance of technologies with different TRL. Upon employing key technologies such as hydrothermal liquefaction, dissolution in solvent, or high-temperature electrolysis, the technical lignins could have a market value of 200 €/t when the market price for aromatic monomers, resins, and vanillin is at least 2.0, 0.8, and 15.0 €/kg, respectively. When lower product selling prices were considered, the aromatic monomers and the resins were not profitable as target products.

Production of energy or chemicals from biomass and several waste substrates appears a concrete strategy for replacing fossil fuels and reducing carbon dioxide emissions in the atmosphere. In particular, methanol from biomass or bio-waste is considered a reliable energy vector and key intermediate for industrial chemistry. Currently, methanol is industrially produced via syngas conversion using natural gas as the main feedstock. Bio-methane produced via anaerobic digestion (AD) of Organic Fraction Municipal Solid Wastes (OFMSW) may be used as an alternative to natural gas for production of syngas with optimal composition via commercialized reforming processes. In this work, a techno-environmental assessment for methanol production from biogas is presented and discussed. In particular, three case studies were assessed to minimize the environmental impact of bio-methanol production.

The agri-food industry annually produces huge amounts of crops residues and wastes, the suitable management of these products is important to increase the sustainability of agro-industrial production by optimizing the entire value chain. This is also in line with the driving principles of the circular economy, according to which residues can become feedstocks for novel processes. Oleaginous yeasts represent a versatile tool to produce biobased chemicals and intermediates. They are flexible microbial factories able to grow on different side-stream carbon sources such as those deriving from agri-food wastes, and this characteristic makes them excellent candidates for integrated biorefinery processes through the production of microbial lipids, known as single cell oils (SCOs), for different applications. This review aims to present an extensive overview of research progress on the production and use of oleaginous yeasts and present discussions on the current bottlenecks and perspectives of their exploitation in different sectors, such as foods, biofuels and fine chemicals.

Industries currently rely on chicory and Jerusalem artichoke for inulin extraction but also cardoon is proved to synthetize and store high quantity of inulin in roots as well. Cardoon is a multipurpose crop, well adapted to marginal lands, whose main residues at the end of cropping cycle consist of roots. However, cardoon roots are a suitable source of inulin, that is of high interest for new generation biodegradable bioplastics production. On the other hand, a sustainable supply chain for inulin production from cardoon roots has not been developed yet. In particular, in the inulin supply chain the most critical part is storage, which can negatively affect both cost and inulin quantity. In the present study the effect on inulin content in cardoon roots stored as dried chipped roots (CRt) and dried whole roots (WRt) was investigated in a 6-month storage trial. Our findings suggest that chipping before storage did not affect the inulin content during the storage. Furthermore, it reduced the time needed for drying by 33.3% and increased the bulk density by 154.9% with the consequent reduction of direct cost for drying, transportation and storage., This research was performed within the Italian Project COMETA-Autoctone Mediterranean crops and their valorization with advanced green chemistry technologies. The project was funded by Ministry of Education, Universities and Research in the frame of PON "Ricerca e Innovazione" 2014���2020 and FSC/ARS01_00606 COMETA/CUP. B2G18000180004/Azione II.

Biorefineries are novel, productive models that are aimed at producing biobased alternatives to many fossil-based products. Biomass supply and overall energy consumptions are important issues determining the overall biorefinery sustainability. Low-profit lands appear to be a potential option for the sustainable production of raw materials without competition with the food chain. Cardoon particularly matches these characteristics, thanks to the rapid growth and the economy of the cultivation and harvesting steps. An integrated biorefinery processing 60 kton/y cardoon lignocellulosic biomass for the production of 1,4-butanediol (bio-BDO) is presented and discussed in this work. After designing the biorefinery flowsheet, the mass and energy balances were calculated. The results indicated that the energy recovery system has been designed to almost completely cover the entire energy requirement of the BDO production process. Despite the lower supply of electricity, the energy recovery system can cover around 78% of the total electricity demand. Instead, the thermal energy recovery system was able to satisfy the overall demand of the sugar production process entirely, while BDO purification columns require high-pressure steam. The thermal energy recovery system can cover around 83% of the total thermal demand. Finally, a cradle-to-gate simplified environmental assessment was conducted in order to evaluate the environmental impact of the process in terms of carbon footprint. The carbon footprint value calculated for the entire production process of BDO was 2.82 kgCO2eq/kgBDO. The cultivation phase accounted for 1.94 kgCO2eq/kgBDO, the transport had very little impact, only for 0.067 kgCO2eq/kgBDO, while the biorefinery phase contributes for 0.813 kgCO2eq/kgBDO.

Single cell oil (SCO) represents an outstanding alternative to both fossil sources and vegetable oils from food crops waste. In this work, an innovative two-step process for the conversion of cellulosic paper mill waste into SCO was proposed and optimised. Hydrolysates containing glucose and xylose were produced by enzymatic hydrolysis of the untreated waste. Under the optimised reaction conditions (Cellic® CTec2 25 FPU/g glucan, 48 h, biomass loading 20 g/L), glucose and xylose yields of 95 mol% were reached. The undetoxified hydrolysate was adopted as substrate for a batch-mode fermentation by the oleaginous yeast Lipomyces starkeyi. Lipid yield, content for single cell, production and maximum oil productivity were 20.2 wt%, 37 wt%, 3.7 g/L and 2.0 g/L/d respectively. This new generation oil, obtained from a negative value industrial waste, represents a promising platform chemical for the production of biodiesel, biosurfactants, animal feed and biobased plastics.

The present investigation aims at exploring the application of low-cost catalysts based on smectitic clays to the hydrodeoxygenation (HDO) of Cynara cardunculus derived lignin. Two types of clay minerals, montmorillonite and saponite, are pillared and decorated with suitable metals by means of an optimized process and characterized by X-ray powder diffraction (XRPD), porosity, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), UV–vis–NIR, Raman, and thermogravimetric analysis (TGA). Alkaline lignin is obtained from steam-treated cardoon. Lignin depolymerization is conducted in a bench-scale apparatus under subcritical conditions, at relatively low temperature (320 °C), for 3 h, under 5-6 MPa of total pressure. Four catalysts are tested, namely, Fe/Al-pillared montmorillonite (FAMO) and saponite (FASA), and Ni-exchanged Ni/Al-pillared montmorillonite (Ni–Ni/AMO) and saponite (Ni–Ni/ASA). Results indicate that mineral clay–based catalysts result effectively in the hydrogenolysis of lignin, producing several low molecular weight aromatics and other species, with overall conversions in the range 60–70%. Montmorillonite-based catalysts yield the highest substrate conversion, with a prevalence of phenols and substituted phenols, whereas only Ni–Ni/ASA generates a higher abundance of aliphatic hydrocarbons. Overall, data indicate that smectitic clays are promising catalyst supports for products-oriented HDO of lignin.

Biomass-derived sugars are platform molecules that can be converted into a variety of final products. Non-food, lignocellulosic feedstocks, such as agroforest residues and low inputs, high yield crops, are attractive bioresources for the production of second-generation sugars. Biorefining schemes based on the use of versatile technologies that operate at mild conditions contribute to the sustainability of the bio-based products. The present work describes the conversion of giant reed (Arundo donax), a non-food crop, to ethanol and furfural (FA). A sulphuric-acid-catalyzed steam explosion was used for the biomass pretreatment and fractionation. A hybrid process was optimized for the hydrolysis and fermentation (HSSF) of C6 sugars at high gravity conditions consisting of a biomass pre-liquefaction followed by simultaneous saccharification and fermentation with a step-wise temperature program and multiple inoculations. Hemicellulose derived xylose was dehydrated to furfural on the solid acid catalyst in biphasic media irradiated by microwave energy. The results indicate that the optimized HSSF process produced ethanol titers in the range 43&ndash, 51 g/L depending on the enzymatic dosage, about 13&ndash, 21 g/L higher than unoptimized conditions. An optimal liquefaction time before saccharification and fermentation tests (SSF) was 10 h by using 34 filter paper unit (FPU)/g glucan of Cellic&reg, CTec3. C5 streams yielded 33.5% FA of the theoretical value after 10 min of microwave heating at 157 &deg, C and a catalyst concentration of 14 meq per g of xylose.

Wheat straw is an abundant source of lignocellulosic biomass that is generally not utilized for biofuel production, nor for other uses. Recent EU renewable energy directive fosters bioethanol production through lignocellulosic sugars fermentation, but the cost of this process is an issue that often depends on biomass characteristics. Lignin is a class of three-dimensional polymers providing structural integrity of plant tissues. Its complex structure, together with hemicelluloses and uronic acids content, could affect the ability of hydrolyzing biomass to fermentable sugars. To get insights into this variation, a set of 10 durum wheat genotypes was analyzed to determine variation of straw digestibility to fermentable sugars. The results showed that the lignin content was the major factor determining the recalcitrance to enzymatic process. The analysis of Spearman’s correlation indicated that the sugar released after enzymatic hydrolysis had a negative connection with the lignin content, while it was positively correlated with the culm length. The possible role of other cell wall components, such as arabinose and uronic acids, was also discussed. This work aimed at analyzing the diversity of lignocellulosic digestibility to fermentable sugars of wheat straw in a small germplasm collection. Some of the selected genotypes were characterized by high sugars digestibility and high grain yield, characteristics that could make biorefining of wheat straw profitable.

The use of low-cost substrates represents one key issue to make single cell oil production sustainable. Among low-input crops

The lignocellulosic biomass can be used as a raw material for power plants, biorefineries, biogas plants (co-fermentation). The environmental benefits can derive mostly from the use of biomass in systems for the production of bio-based products (e.g., biofuels). Another essential environmental aspect is the supply of the biomass without high emissions to transport the raw material from the collection place to plants place. Technical and environmental assessment analyzes are necessary to identify the best benefits of the technologies (usually suitable for large plant sizes) and of optimized local supply systems (usually convenient for small plant sizes with short transportation supply chain). In this work, an optimization methodology based on process simulation and supply chain analysis is proposed for the bio-based system of the Basilicata Region. The Basilicata Region is rich in residual biomass (straw) which is currently not valorized. Process simulation software Aspen Plus was used to build a process simulation model to evaluate the technical feasibility of using straw in two biorefinery systems: lignocellulosic biorefinery producing bioethanol and co-feeding to existing biogas plants to produce biomethane. A model based on p-median problem solver included in the ArcGis 10 Network Analyst extension was used to evaluate the optimal position of a lignocellulosic biorefinery or the optimal quantities of straw to be transported to biogas plants to produce biomethane. Main results show he bioethanol production leads to high CO2 emission savings thanks to higher CO2 absorption by lignocellulosic biomass and the green electricity coproduction. The co-digestion of pretreated lignocellulosic biomass feedstocks leads to high-density fuels production, but globally to lower CO2-equivalent savings for GJ produced.

The production of seed oils from Cynara cardunculus generates huge amounts of lignocellulosic residues which can be exploited according to a cascade approach. In this paper, residual cardoon biomass (RCB) was tested as a growth substrate for the solid-state production of cellulolytic cocktails by species known to produce glucose-tolerant β-glucosidase isoenzymes. Best productions were obtained with 10-d-old Aspergillus tubingensis cultures on RCB supplemented with wheat bran (200 g kg−1) yielding β-glucosidase and endo-β-1,4-glucanase activities as high as (25 and 4) IU g−1, respectively, and 4 FPU g−1. The saccharification performance of the obtained cocktail tested on acid-catalysed steam-exploded RCB at low solid loading (25 g dm−3) was around 53% at 20 FPU g−1 cellulose. These performance were significantly enhanced by adding the xylanase-rich NS 22083 commercial formulation, reaching glucose yields higher than 80% after 72 h incubation. The use of the catalytic additive was optimized by a statistical approach, based on factorial analysis. A comparison of the performance of the A. tubingensis reinforced cocktail with the Cellic®CTec2 taken as benchmark formulation was done at the same enzyme load and performed at industrially relevant solid loadings, namely at (100 and 200) g dm−3. This comparison showed that Cellic®CTec2 led to only slightly higher glucose yields while an opposite outcome was observed for xylose yields, irrespective of the solid loading conditions. Thus, this study shows that an in-house enzyme production, based on the solid-state conversion of an industrial byproduct, able of yielding cellulolytic cocktails with substantial saccharification performance is feasible.

A hybrid system based on lignocellulosic biomass gasification and syngas fermentation represents a second-generation biorefinery approach that is currently in the development phase. Lignocellulosic biomass can be gasified to produce syngas, which is a gas mixture consisting mainly of H2, CO, and CO2. The major challenge of biomass gasification is the syngas’s final quality. Consequently, the development of effective syngas clean-up technologies has gained increased interest in recent years. Furthermore, the bioconversion of syngas components has been intensively studied using acetogenic bacteria and their Wood–Ljungdahl pathway to produce, among others, acetate, ethanol, butyrate, butanol, caproate, hexanol, 2,3-butanediol, and lactate. Nowadays, syngas fermentation appears to be a promising alternative for producing commodity chemicals in comparison to fossil-based processes. Research studies on syngas fermentation have been focused on process design and optimization, investigating the medium composition, operating parameters, and bioreactor design. Moreover, metabolic engineering efforts have been made to develop genetically modified strains with improved production. In 2018, for the first time, a syngas fermentation pilot plant from biomass gasification was built by LanzaTech Inc. in cooperation with Aemetis, Inc. Future research will focus on coupling syngas fermentation with additional bioprocesses and/or on identifying new non-acetogenic microorganisms to produce high-value chemicals beyond acetate and ethanol.

A two-step exploitation of the giant reed cellulose to glucose and levulinic acid, after the complete removal of the hemicellulose fraction, was investigated using FeCl3 as catalyst. In the first step, the microwave-assisted hydrolysis of cellulose to glucose was optimised by response surface methodology analysis, considering the effect of temperature, reaction time and catalyst amount. Under the optimised reaction conditions, the glucose yield was 39.9 mol%. The cellulose-rich residue was also converted by enzymatic hydrolysis, achieving the glucose yield of 39.8 mol%. The exhausted residue deriving from the chemical hydrolysis was further converted to levulinic acid by microwave treatment at harsher reaction conditions. The maximum levulinic acid yield was 64.3 mol%. On the whole, this cascade approach ensured an extensive and sustainable exploitation of the C6 carbohydrates to glucose and levulinic acid, corresponding to about 70 mol% of glucan converted to these valuable bioproducts in the two steps.

Lignocellulosic biomass represents one of the most important feedstocks for future biorefineries, being a precursor of valuable bio-products, obtainable through both chemical and biological conversion routes. Lignocellulosic biomass has a complex matrix, which requires the careful development of multi-step approaches for its complete exploitation to value-added compounds. Based on this perspective, the present work focuses on the valorization of hemicellulose and cellulose fractionsof giant reed (Arundo donax L.) to give second-generation sugars, minimizing the formation of reaction by-products. The conversion of hemicellulose to xylose was undertaken in the presence of the heterogeneous acid catalyst Amberlyst-70 under microwave irradiation. The effect of the main reaction parameters, such as temperature, reaction time, catalyst, and biomass loadings on sugars yield was studied, developing a high gravity approach. Under the optimised reaction conditions (17 wt% Arundo donax L. loading, 160 &deg, C, Amberlyst-70/Arundo donax L. weight ratio 0.2 wt/wt), the xylose yield was 96.3 mol%. In the second step, the cellulose-rich solid residue was exploited through the chemical or enzymatic route, obtaining glucose yields of32.5 and56.2 mol%, respectively. This work proves the efficiency of this innovative combination of chemical and biological catalytic approaches, for the selective conversion of hemicellulose and cellulose fractions of Arundo donax L. to versatile platform products.

Market implementation of integrated biorefinery requires reliable and advanced processing units combined with eco-friendly and economically profitable production chains. Future developments of integrated biorefinery systems should include either crop cultivation with selected genotypes that maximize full chain performances either the increasing use of disposable or/and underused biomass. The aim of this paper was to review the main biorefining opportunities related to agro-bioenergy co-products and agroindustrial residues potentially available on the World (as biofuel co/by-products, agricultural residues, agricultural by-products and agro-wastes), paying a special attention to high-value added products associated to some emerging markets. The current status and future perspectives of conversion from agro-bioenergy residual biomass into high-value bio-based products by innovative biorefineries have been considered. After a brief recognition on the nature and origin of the main categories of organic residuals derived from the biofuel chains and agricultural, forestry, food processing and animal activities within definitions given by the European Union, this paper has firstly focused its choice on the high-value added products associated to some chemical basic-platforms (succinic acid, cellulose, glycerin, proteins, peptides, enzymes, etc.). A special attention has also been done to high-value added bio-based products and commodities related to sustainable and renewable farming systems (soil amendment, phytosanitary drug, plant biostimulant and biofertilizer) and bio-based industries in producing innovative biomaterials (bioplastic, lignin and alginate). Finally, this paper has addressed own concern on the perspectives of integrated biorefining from organic residuals drawing particular attention to the European and Italian contexts giving and discussing some new opportunities for big players and stakeholders. © 2018 Elsevier Ltd

The economic sustainability of lignocellulosic biorefineries can be significantly improved by co-producing added value chemicals together with common biofuels like ethanol. In this work a techno-economic analysis of a multiproduct biorefinery was carried out by means of process simulations, cost and profitability analysis. Alternative process flowsheets including the co-production of xylitol or furfural from C5 sugars deriving from biomass hydrolysis were assessed and compared with the ethanol base case. A comparison between the purchase of enzymes and the on-site production of enzymes was also addressed. The lowest Payback Selling Price of ethanol was obtained for the case of xylitol co-production thanks to its higher added value.

Background: Some lignocellulosic biomass feedstocks occur in Mediterranean Countries. They are still largely unexploited and cause considerable problems due to the lack of cost-effective harvesting, storage and disposal technologies. Recent studies found that some basidiomycetous yeasts are able to accumulate high amount of intracellular lipids for biorefinery processes (i.e., biofuels and biochemicals). Accordingly, the above biomass feedstocks could be used as carbon sources (after their pre-treatment and hydrolysis) for lipid accumulation by oleaginous yeasts. Results: Cardoon stalks, stranded driftwood and olive tree pruning residues were pre-treated with steam-explosion and enzymatic hydrolysis for releasing free mono- and oligosaccharides. Lipid accumulation tests were performed at two temperatures (20 and 25 °C) using Leucosporidium creatinivorum DBVPG 4794, Naganishia adeliensis DBVPG 5195 and Solicoccozyma terricola DBVPG 5870. S. terricola grown on cardoon stalks at 20 °C exhibited the highest lipid production (13.20 g/l), a lipid yield (28.95%) close to the maximum theoretical value and a lipid composition similar to that found in palm oil. On the contrary, N. adeliensis grown on stranded driftwood and olive tree pruning residues exhibited a lipid composition similar to those of olive and almonds oils. A predictive evaluation of the physical properties of the potential biodiesel obtainable by lipids produced by tested yeast strains has been reported and discussed. Conclusions: Lipids produced by some basidiomycetous yeasts grown on Mediterranean lignocellulosic biomass feedstocks could be used as supplementary sources of oils for producing biofuels and biochemicals. © 2018 The Author(s).

Agricultural by-products such as corn stover are considered strategic raw materials for the production of second-generation bioethanol from renewable and non-food sources. This paper describes the conversion of steam-pretreated corn stover to ethanol utilising a multi-step process including enzymatic hydrolysis, isomerisation, and fermentation of mixed hydrolysates with native Saccharomyces cerevisiae. An immobilised isomerase enzyme was used for the xylose isomerisation along with high concentrations of S. cerevisiae. The objective was to assess the extent of simultaneity of the various conversion steps, through a detailed analysis of process time courses, and to test this process scheme for the conversion of lignocellulosic hydrolysates containing several inhibitors of the isomerase enzyme (e.g. metal ions, xylitol and glycerol).The process was tested on two types of hydrolysate after acid-catalysed steam pretreatment: (a) the water soluble fraction (WSF) in which xylose was the largest carbon source and (b) the entire slurry, containing both cellulose and hemicellulose carbohydrates, in which glucose predominated.The results indicated that the ethanol concentration rose when the inoculum concentration was increased in the range 10-75g/L. However, when xylose was the largest carbon source, the metabolic yields were higher than 0.51gethanol/gconsumed sugars probably due to the use of yeast internal cellular resources. This phenomenon was not observed in the fermentation of mixed hydrolysates obtained from the entire pretreated product and in which glucose was the largest carbon source. The ethanol yield from biomass suspensions with dry matter (DM) concentrations of 11-12% (w/v) was 70% based on total sugars (glucose, xylose, galactose). The results suggest that xylulose uptake was more effective in mixed hydrolysates containing glucose levels similar to, or higher than, xylose.Analysis of the factors that limit isomerase activity in lignocellulosic hydrolysates excluded any inhibition due to residual calcium ions after the detoxification of the hemicellulose hydrolysates with Ca(OH)2. By contrast, most of the enzyme activity ceased during the fermentation of the entire slurry after steam explosion, probably due to synergistic inhibition effects of various fermentation co-products. © 2014 Elsevier B.V.

The pretreatment step has a key role in the enzymatic conversion of lignocellulosic biomass to bioethanol. Steam pulping of biomass has long been recognized as being effective in producing high biomass fractionation. In this step, the preliminary impregnation of biomass with acid catalysts, including SO2, has been shown to further improve the hydrolytic effect and increase the digestibility of the fibers by enzymes. This work focused on developing an experimental setup for the SO2 impregnation, enabling accurate control of the process variables. The final purpose was the assessment of a method to minimize the quantity of SO2 used, and that could be applicable to continuous operations. Aspen chips were impregnated with the acid catalyst at room temperature in a stainless steel batch reactor, and the influence of the biomass humidity and contact time on SO2 uptake was explored. After the catalyst adsorption, biomass was fed into the steam explosion batch reactor and steamed at 205 °C for 3 and 10 min to obt...

The IEA Bioenergy Task 42 “Biorefining” with its 11 member countries (A, AUS, CA, DK, G, I, IR, J, NL, NZ, USA) has the following definition on biorefining: “Biorefining is the sustainable processing of biomass into a spectrum of bio-based products (food, feed, chemicals, and materials) and bioenergy (biofuels, power and/or heat)”. Wood as a renewable and sustainable resource offers great opportunities for a comprehensive product portfolio to satisfy the different needs in a future BioEconomy. Worldwide many different wood based biorefining concepts are investigated and realised, of which the development status and the perspectives for implementation are quite different. Task 42 developed a “Biorefinery Fact Sheet” for the uniform and compact description of the main characteristics of these biorefineries and their whole value chain. The “Biorefinery Fact Sheets” are initially applied for a first selection of 15 interesting biorefinery systems identified by IEA Bioenergy Task 42, of which 6 are based on wood. Based on these fact sheets an easy and uniform comparison of the different wood based biorefinery concepts is possible. The “Biorefinery Fact Sheet” assists various stakeholders in finding their position on wood based biorefining in a future BioEconomy.

We investigated ethanol production from mixed sugar syrups. Hydrolysates were prepared from enzymatic saccharification of steam-pretreated aspen chips. Syrups containing 45 g/L of glucose and 12 g/L of xylose were detoxified through two ion-exchange resins and then fermented with Pichia stipitis and Saccharomyces cerevisiae immobilized in Ca-alginate gel beads. Combinations of different gel fractions in the fermentation volume, amount of yeast cells, and ratios of P. stipitis vs S. cerevisiae within each bead were compared. In the best conditions, by using a total beads volume corresponding to 25% of the working volume, we obtained a yield of 0.39 g(ethanol)/g(initial sugars). This amount of gel entrapped an initial cell concentration of 6 x 1012cells/L with ratio of S. cerevisiae/P. stipitis of 0.25 g/g. Modified stirred-tank reactors were obtained either by adding marbles or by inserting a perforated metal cylinder, which reduced considerably the rupture of beads while visibly improving oxygenation of the medium.