Green Biorefinery Research Articles

Application of lactic acid bacteria in green biorefineries.

Lactic acid bacteria (LAB) have extensive industrial applications as producers of lactic acid, as probiotics, as biocontrol agents and as biopreservatives. LAB play a large role in food fermentation and in silage processes, where crops such as grass, legumes, cereals or corn are fermented into high-moisture feed that is storable and can be used to feed cattle, sheep or other ruminants. LAB also have great applications within green biorefineries, with simultaneous production of protein-rich feed for monogastric animals, silage or feed pellets for ruminants and production of lactic acid or specific amino acids. In green biorefineries, fresh or ensiled wet biomass is mechanically fractionated into green juice and solid residues (press cake), where the plant juice, for example, can be used for production of lactic acid using LAB. In a process named 'ENLAC', recovery of protein and chlorophyll from silage by simultaneous lactic acid fermentation and enzyme hydrolysis has been developed. Furthermore, a process for protein recovery was recently developed by applying a specific LAB starter culture to green juice from freshly harvested crops. This paper focuses on reviewing LAB for their applications within biorefining of 'green' crops such as clover, alfalfa, grasses and other green plant materials.

Green biorefinery technologies based on waste biomass

This themed issue includes a collection of articles on green biorefinery technologies based on waste biomass.

Valorization of Lignin–Carbohydrate Complexes from Hydrolysates of Norway Spruce: Efficient Separation, Structural Characterization, and Antioxidant Activity

Hot-water extraction has shown great potential in a green biorefinery; however, efficient separation of lignin and carbohydrates is still a big challenge, especially to lignin–carbohydrate complexes (LCCs). The aim of the present study was to develop a facile approach for efficiently fractionating LCCs from hot-water extraction liquor of spruce wood to understand their comprehensive structure and thus to achieve the valorization of fractions. Approximately 93% of the hemicelluloses were first recovered by a selective adsorptive resin from hot-water hydrolysates. The lignin-rich fractions obtained from desorption of the adsorbed compounds were further subjected to a gradient dialysis procedure toward functional fractionation. Linear relationship between lignin and uronic acids as well as xylose contents in graded fractions of all hydrolysates was observed. Further characterization of LCCs by two-dimensional nuclear magnetic resonance and pyrolysis-gas chromatography-mass spectrometry showed the large diffe...

Demonstration‐scale protein recovery by lactic acid fermentation from grass clover – a single case of the production of protein concentrate and press cake silage for animal feeding trials

AbstractThere is an increasing interest in green biorefineries for the utilization of green biomass to provide a variety of valuable products. Proteins can be extracted from green biomasses such as alfalfa, clover, or grass and separated into protein‐rich concentrates suitable for feeding to monogastric animals. Press cake suitable for feeding ruminant animals is also produced. Full implementation of such a green biorefinery requires knowledge and experience of production at demonstration scale. Moreover, product evaluation in animal‐feeding trials requires a large amount of product. There has been collaboration in Denmark between several partners from industry and academia to assess the practicality and scalability of a green biorefining plant producing protein concentrate and press cake silage from organic grass clover at the scale of ca. 10 tons per hour fresh biomass input. Lactic acid fermentation of the pressed green juice was successfully performed to precipitate proteins and stabilize the juice. Despite minor difficulties, the demonstration‐scale biorefining plant was operative for four days, processed 444 tons of grass clover, and resulted in the overall production of 1 ton of dried protein concentrate, 7 tons of protein paste, and 223 tons of press cake silage. The protein concentrate was rich in essential amino acids and was tested in feeding trials with poultry; the press cake silage, rich in processed fibers and fiber‐associated proteins, was tested in feeding trials with dairy cows. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd

Catalytic peroxide fractionation processes for the green biorefinery of wood

A kinetic study and optimization of pine wood peroxide fractionation in the medium acetic acid–water over TiO2 catalyst were accomplished for the first time. Kinetic regularities and the product composition of green processes of catalytic peroxide fractionation of softwood (pine, abies, larch) and hardwood (aspen, birch) over 1 wt% TiO2 catalyst in the acetic acid–water medium were compared at the temperature range 70–100 °C. For all type of wood, the processes of peroxide delignification are described by the first order equations and their activation energies are varied at the range 76–94 kJ/mol. According to FTIR, XRD, SEM, NMR data, the cellulosic products of peroxide delignification have a structure similar to microcrystalline cellulose regardless of the nature of wood. Soluble products are presented by organic acid and monosaccharides. The scheme of green biorefinery of pine wood based on extractive-catalytic fractionation of wood biomass on microcrystalline cellulose, hemicelluloses, aromatic and aliphatic acids, monosaccharides, turpentine and rosin was developed. Green and non-toxic reagents and solid catalyst are used in the developed scheme of biorefinery.

An integrated green biorefinery approach towards simultaneous recovery of pectin and polyphenols coupled with bioethanol production from waste pomegranate peels

An integrated biorefinery, incorporating hydrothermal processing of waste pomegranate peels (WPP), was proposed for the acid and organic solvent-free simultaneous recovery of pectin and phenolics with bioethanol production. The hydrothermal treatment (HT) was optimized using Box-Behnken design and the maximum recovery of pectin (18.8–20.9%) and phenolics (10.6–11.8%) were obtained by hydrothermal treatment at 115 °C for 40 min with a liquid-solid ratio of 10. The WPP pectin was characterized by IR, 1H NMR, and TGA which showed close similarity to commercial pectin. Depending on WPP cultivar type the degree of esterification, galacturonic acid content and molecular weight of pectin were in the range of 68–74%, 71–72%, and 131,137–141,538 Da, respectively. The recovered phenolics contained 57–60% punicalagin. Enzyme digestibility of WPP improved using HT with 177 g glucose produced per kg dry mass which was fermented to obtain 80 g ethanol with 88% of theoretical yield.

Green biorefinery of larch wood biomass to obtain the bioactive compounds, functional polymers and nanoporous materials

The first green biorefinery of larch wood based on the fractionation of biomass into dihydroquercetin (DHQ), arabinogalactan (AG), microcrystalline cellulose (MCC) and soluble lignin (SL) is reported. The new green method of one-step isolation of DHQ and AG from larch wood by ethanol–water solution was developed. The first results of kinetic studies and optimization of the process of extracted larch wood peroxide fractionation into MCC and SL in acetic acid–water medium in the presence of green TiO2 catalyst are described. The products obtained from larch wood were characterized by FTIR, NMR, XRD, AFM and chemical methods. The scheme of larch wood biorefinery is suggested which integrates the developed processes of woody biomass fractionation into DHQ, AG, MCC and SL. All developed methods use non-toxic and less-toxic reagents, such as water, ethanol, hydrogen peroxide and acetic acid.

Techno-environmental assessment of the green biorefinery concept: Combining process simulation and life cycle assessment at an early design stage

The Green biorefinery (GBR) is a biorefinery concept that converts fresh biomass into value-added products. The present study combines a Process Flowsheet Simulation (PFS) and Life Cycle Assessment (LCA) to evaluate the technical and environmental performance of different GBR configurations and the cascading utilization of the GBR output. The GBR configurations considered in this study, test alternatives in the three main steps of green-biorefining: fractionation, precipitation, and protein separation. The different cascade utilization alternatives analyse different options for press-pulp utilization, and the LCA results show that the environmental profile of the GBR is highly affected by the utilization of the press-pulp and thus by the choice of conventional product replaced by the press-pulp. Furthermore, scenario analysis of different GBR configurations shows that higher benefits can be achieved by increasing product yields rather than lowering energy consumption. Green biorefining is shown to be an interesting biorefining concept, especially in a Danish context. Biorefining of green biomass is technically feasible and can bring environmental savings, when compared to conventional production methods. However, the savings will be determined by the processing involved in each conversion stage and on the cascade utilization of the different platform products.

Environmental screening of potential biomass for green biorefinery conversion

Abstract Green biorefinery (GBR) is a new biorefinery technology for the conversion of fresh biomass to value added products. In the present study, we combined a Process Flowsheet Simulation (PFS) and Life Cycle Assessment (LCA) of a small scale decentralized GBR to screen environmental impact profiles for potential biomass feedstocks for GBR conversion. Furthermore, we carried out hotspot and sensitivity analysis to identify where the largest impacts arise in the biorefining stage in order to provide recommendations and focus points for GBR technology developers. The GBR considered in this study produces a protein-rich feed for monogastric animals and an energy-rich feed from the press pulp and biogas from the GBR residues. The included biomass feedstocks are: alfalfa, grass-clover, festulolium and ryegrass. These biomasses were selected to accommodate variations in central biomass characteristics like: crop yields, rate of fertilizer application, chemical biomass compositions and related potential environmental implications. Among the studied crops, alfalfa provides the best overall environmental performance due to its high yield and low agricultural input demands. Results of the hotspot analysis further identified the coagulation and the drying as the processes that induce most of the environmental impacts in the biorefining stage. Conversion of green biomass for the production of feed and energy could provide environmental benefits compared to the production of conventional feed. However, the GBR technology have still room for optimization in order to further reduce the environmental impacts, across all impact categories, by decreasing energy consumption and increasing conversion efficiency.

Anaerobic digestion of residual liquid effluent (brown juice) from a green biorefinery

This work studied the anaerobic digestion of brown juice, a liquid residual stream generated from biomass fractionation in a green biorefinery. Biomethane potential batch tests and inhibition studies of brown juice were performed during continuous processing in an upflow anaerobic sludge blanket reactor. Prolongation of the lag phase in the batch tests with increasing substrate/inoculum ratio suggested initial inhibition, which was, however, overcome by adaptation. This was indicated by high final methane yields, which were close to the theoretical maximum of up to 500 L-CH4 kg-VS−1, achieved after 15 days for most of the set-ups. Reactor operation at the organic loading rate of 13.9 g-COD L−1 day−1 and hydraulic retention time of 3 days revealed methane yields of 202 L-CH4 kg-COD−1 (307 L-CH4 kg-VS−1). Particle size analysis of the granules used in the reactor showed disintegration of the larger granules.

Green Biorefinery of Giant Miscanthus for Growing Microalgae and Biofuel Production

In this study, an innovative green biorefinery system was successfully developed to process the green biomass into multiple biofuels and bioproducts. In particular, fresh giant miscanthus was separated into a solid stream (press cake) and a liquid stream (press juice) using a screw press. The juice was used to cultivate microalga Chlorella vulgaris, which was further thermochemically converted via thermogravimetry analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis, resulting in an approximately 80% conversion. In addition, the solid cake of miscanthus was pretreated with dilute sulfuric acid and used as the feedstock for bioethanol production. The results showed that the miscanthus juice could be a highly nutritious source for microalgae that are a promising feedstock for biofuels. The highest cell density was observed in the 15% juice medium. Sugars released from the miscanthus cake were efficiently fermented to ethanol using Saccharomyces cerevisiae through a simultaneous saccharification and fermentation (SSF) process, with 88.4% of the theoretical yield.

Green catalytic processing of native and organosolv lignins

Two ways of catalytic depolymerization of native and isolated wood lignins are described: the peroxide delignification of hardwood (aspen, birch) and softwood (abies) in the medium of acetic acid – water over TiO2 catalyst and the thermal dissolution of organosolv lignins (ethanol-lignin and acetone-lignin) in supercritical alcohols (ethanol and butanol) over solid Ni-containing catalysts.The catalyst TiO2 in rutile modification has the higher activity in wood peroxide delignification at 100 °C as compared to TiO2 in anatase modification. The results of kinetic studies and optimization of the processes of peroxide depolymerization of hardwood (aspen, birch) and softwood (abies) lignins in the medium of acetic acid – water over catalyst TiO2 (rutile) at mild conditions (≤100 °C, atmospheric pressure) are compared. The catalyst TiO2 initiates the formation of OH and OOH radicals from H2O2 which promote the oxidative fragmentation of wood lignin. In this case, the peroxide depolymerization of softwood lignin, constructed from phenylpropane units of guaiacyl-type proceeds more difficult than the hardwood lignins, mainly containing syringyl-type units.The solid and soluble products of peroxide catalytic delignification of wood under the optimized conditions were studied by FTIR, XRD, GC–MS and chemical methods. Regardless of the nature of wood the cellulosic products have a structure similar to microcrystalline cellulose. The soluble products mainly consist of monosaccharides and organic acids. Aromatic compounds are present only in a low amount which indicates the oxidative degradation of aromatic rings of lignin phenylpropane units under the used conditions of wood catalytic delignification.The processes of thermal dissolution of acetone-lignin and ethanol-lignin from aspen-wood in supercritical ethanol and butanol over Ni-containing catalyst (NiCu/SiO2, NiCuMo/SiO2) are compared. The composition, structure and thermal properties of organosolv lignins were studied with the use of FTIR, GPC, 1H – 13C HSQC NMR, DTA and elemental analysis.The influence of a composition of Ni-containing catalyst on the thermal conversion in supercritical butanol and ethanol of ethanol-lignin and acetone-lignin was established. The highest conversion of lignins (to 93% wt.) in supercritical alcohols and the highest yield of liquid products (to 90% wt.) were achieved at 300 °C in the presence of catalyst NiCuMo/SiO2.Scheme of green biorefinery of wood based on the use of non-toxic and low-toxic reagents (H2O2, H2O, acetic acid, ethanol, butanol) and solid catalysts (TiO2, NiCuMo/SiO2) is suggested.

Can farmers mitigate environmental impacts through combined production of food, fuel and feed? A consequential life cycle assessment of integrated mixed crop-livestock system with a green biorefinery

This study evaluates environmental impacts of an integrated mixed crop-livestock system with a green biorefinery (GBR). System integration included production of feed crops and green biomasses (Sys-I) to meet the demand of a livestock system (Sys-III) and to process green biomasses in a GBR system (Sys-II). Processing of grass-clover to produce feed protein was considered in Sys-II, particularly to substitute the imported soybean meal. Waste generated from the livestock and GBR systems were considered for the conversion to biomethane (Sys-IV). Digestate produced therefrom was assumed to be recirculated back to the farmers' field (Sys-I). A consequential approach of Life Cycle Assessment (LCA) method was used to evaluate the environmental impacts of a combined production of suckler cow calves (SCC) and Pigs, calculated in terms of their live weight (LW). The functional unit (FU) was a basket of two products “1kgLW-SCC+1kgLW-Pigs”, produced at the farm gate. Results obtained per FU were: 19.6kg CO2 eq for carbon footprint; 0.11kg PO4 eq for eutrophication potential, −129MJ eq for non-renewable energy use and −3.9 comparative toxicity units (CTUe) for potential freshwater ecotoxicity. Environmental impact, e.g. greenhouse gas (GHG) emission was primarily due to (i) N2O emission and diesel consumption within Sys-I, (ii) energy input to Sys-II, III and IV, and (iii) methane emission from Sys-III and Sys-IV. Specifically, integrating GBR with the mixed crop-livestock system contributed 4% of the GHG emissions, whilst its products credited 7% of the total impact. Synergies among the different sub-systems showed positive environmental gains for the selected main products. The main effects of the system integration were in the reductions of GHG emissions, fossil fuel consumption, eutrophication potential and freshwater ecotoxicity, compared to a conventional mixed crop-livestock system, without the biogas conversion facility and the GBR.

Where to implement local biotech innovations? A framework for multi-scale socio-economic and environmental impact assessment of Green Bio-Refineries

Green Bio-Refineries (GBRs) have economic and environmental potentials through changing land use from cereals to grass production and provision of grass-based protein feed for livestock production and other valuable byproducts. However, the potentials are dependent on local conditions of the GBRs, such as land productivity, environmental sensitivity and transport distances for feedstock as well as the regional economy which GBRs are a part of. In this paper, we compare the total (direct, indirect and induced) effects of different location choices of GBRs in Denmark at different (municipal, regional, national) scales − a key step for decisions about development of GBRs from both investors' and authorities' perspectives. We integrate a local life-cycle assessment (LCA), a geographic information system (GIS) analysis and an economic-environmental input-output (EEIO) based model (LINE) into a common framework (GIS-LCA-EEIO). We show that locating GBRs in Western Denmark, where the soils are primarily sandy and livestock densities are high, generates higher socio-economic gains than in Eastern Denmark, where the soils are primarily loamy and the concentrations of livestock are lower. We conclude by sketching out priority areas for developing GBRs and discuss the policy implications of the results within the context of development of a bio-based economy.

Green catalytic valorization of hardwood biomass into valuable chemicals with the use of solid catalysts

Results of the study on green valorization of hardwood biomass into valuable chemicals with the use of solid catalysts were described. The heterogeneous catalytic processes of hemicelluloses and cellulose hydrolysis, wood oxidative fractionation and lignin depolymerization in supercritical spirits are suggested to employ for the green biorefinery of hardwood to xylose, pure cellulose, glucose, alcohols and liquid hydrocarbons.

Biogas potential of green biomass after protein extraction in an organic biorefinery concept for feed, fuel and fertilizer production

The biogas potential of the residual fractions of four organically grown green crops after protein extraction was studied. The protein extraction method involved screw pressing of freshly harvested biomass to obtain a plant juice, followed by precipitation of the proteins. After protein extraction, 95% of organic matter was still present in the residual press cake and juice. Methane yields in the range of 219–375 and 429–539 ml-CH4 g-VS−1 were obtained for the mono-digestion of press cake and the residual juice, respectively, and up to 81% of the methane potential of the fresh crops was recovered in the two residual fractions when evaluated separately. Co-digestion of the press cake and the residual juice at the organic matter ratio at which those fractions leave the biorefinery, resulted in a methane yield of 400 ml-CH4 g-VS−1 according to the regression model equation developed for red clover. Consequently, 65% of the methane potential from fresh red clover could be recovered by co-digestion of the residual fractions from the green biorefinery after extraction of proteins.

A bio-economic analysis of a sustainable agricultural transition using green biorefinery

Traditional pig production often relies on cereal-based feed, which has adverse environmental effects, e.g. nitrogen leaching and greenhouse gas (GHG) emissions. Alternative production systems are therefore sought to improve the sustainability of pig production. A promising alternative is to use proteinaceous feed from grass, produced in a green bio-refinery (GBR), to substitute part of the cereals in the feed. Cultivation of grass on arable land can reduce nitrogen leaching and pesticide application, and increase carbon storage. The GBR using grass as feedstock also produces valuable byproducts, e.g. fibre and biogas. In this study we combine a life-cycle analysis (LCA) and a cost-benefit analysis to compare the economic and environmental effects of producing the pig feed to produce 1ton of pork using two feeding systems. We apply this approach to the intensive Danish pork production as a case study. The results show that compared with traditional cereal-based feeding system for producing a ton of pork, using proteinaceous concentrate from small-scale GBR will (1) decrease the average feed cost by 5.01%; (2) produce a profit of 96€ before tax in the GBR; and (3) decrease the nitrogen leaching (NO3-N) by 28.2%. However, in most of the scenarios (except for G2), the nitrogen emissions into the air (N2O-N) will also increase because of the increased N fertilizer application compared to a cereal-based system. In most of the scenarios (except for S1 and G1), the energy and land use will also be saved. However, some important factors, e.g. the soil characteristics, pressed juice fraction in fresh biomass and scale of GBR, could subvert the conclusion about energy and land use saving in the alternative feeding system.

Green Biorefinery - Production of Amino Acids from Grass Silage Juice using an Ion Exchanger Device at Pilot Scale

The use of grass biomass in biorefineries offers sustainable routes to gain bulk and fine chemicals, such as amino acids from biobased resources. In 2008, the Green Biorefinery Upper Austria has been established to extract amino acids and lactic acid from grass silage at pilot scale. After pressing the grass and pre-treating the grass silage juice by different state of the art membrane technologies, the amino acids were purified and separated using an ion exchanger device. To guarantee higher loadings and through puts per batch run at the ion exchanger device, a displacement chromatography was applied. Using the present device 6 to 10 kg amino acids per batch run were yielded. By monitoring the displacement step, the separation into three different amino acid product fractions was implemented. Additionally, different process parameters, such as flow rates or different amino acid concentrations in the feed were investigated to find out possible correlations and to increase the yield per batch run. Considering the investigated process conditions, it was found out that the ratio between amino acids and inorganic cations in the feed influences the yield per batch run.

Green biorefinery – Industrial implementation

Oil refineries currently generate a multitude of products for almost every sphere of life at very high efficiency. However, fossil raw materials are just available in limited quantities. The development of comparable BIOREFINERIES is necessary to make a variety of competitive biological products regarding their equivalent products based on fossil raw materials. The product range of a biorefinery comprises products that can be manufactured on the basis of crude oil, as well as such products that cannot be produced on the basis of crude oil (Kamm, Gruber, & Kamm, 2011). GREEN BIOREFINERIES [GBR’s] are complex systems of sustainable, environment- and resource-friendly technologies for a comprehensive material and energy use or recovery of renewable raw materials in form of green and waste biomasses from a sustainable land use as target (Kamm et al., 2009; Digman, Runge, Shinners, & Hatfield, 2013).

Characterization of a new aryl-alcohol oxidase secreted by the phytopathogenic fungus Ustilago maydis.

The discovery of novel fungal lignocellulolytic enzymes is essential to improve the breakdown of plant biomass for the production of second-generation biofuels or biobased materials in green biorefineries. We previously reported that Ustilago maydis grown on maize secreted a diverse set of lignocellulose-acting enzymes including hemicellulases and putative oxidoreductases. One of the most abundant proteins of the secretome was a putative glucose-methanol-choline (GMC) oxidoreductase. The phylogenetic prediction of its function was hampered by the few characterized members within its clade. Therefore, we cloned the gene and produced the recombinant protein to high yield in Pichia pastoris. Functional screening using a library of substrates revealed that this enzyme was able to oxidize several aromatic alcohols. Of the tested aryl-alcohols, the highest oxidation rate was obtained with 4-anisyl alcohol. Oxygen, 1,4-benzoquinone, and 2,6-dichloroindophenol can serve as electron acceptors. This GMC oxidoreductase displays the characteristics of an aryl-alcohol oxidase (E.C.1.1.3.7), which is suggested to act on the lignin fraction in biomass.