Hydrotreating and hydrothermal treatment of alkaline lignin as technological valorization options for future biorefinery concepts: a review

Lignin has the potential to be a sustainable resource for producing biobased chemicals (e.g. phenols, aromatic hydrocarbons, vanillin) for multiple applications. However, given its heterogeneous and rigid structure, its efficient conversion to value‐added products remains one of the most important limiting factors for the successful viability of the biobased economy. Hydrotreating and hydrothermal treatment (including liquefaction, gasification and wet oxidation) are promising technologies that can convert lignin into biobased products. This review article provides a literature overview of how key process parameters of hydrotreating and hydrothermal treatment (operating conditions, catalysts, solvents, type of starting lignin) may influence the conversion of alkaline lignin into valuable chemical products. It was observed that low selectivity to products (and subsequent required separation and purification) and char formation are the main hurdles for effective conversion of alkaline lignin. However, experimental work in alternative catalytic systems, solvents and hydrogen sources has shown that promising opportunities exist to overcome these drawbacks. Certain catalysts (e.g. Ru/Al₂O₃) have been found to improve selectivity and the use of alcohol solvents (especially methanol or ethanol) as a hydrogen source has been found to improve product yields and reduce char formation at lower working temperatures and pressures. © 2016 Society of Chemical Industry     

Food waste as a source of value‐added chemicals and materials: a biorefinery perspective

As the availability of fossil‐based resources declines, there is an impending necessity of finding alternative feedstock able to secure the production of fuels and chemicals. Exploitation of biomass as renewable source of chemicals is an attractive possibility, in particular the one derived from food waste (FW). Every year, large amounts of waste are generated within or at the end of the food supply chain at the consumers use stage and hence its valorisation attracts great attention. FW has proven a valuable feedstock for its exploitation to produce a wide array of intermediates and products with promising applications in industry, owing to their similar performance with respect to established products. These include organic acids and furans (generally used as platform chemicals to further products); polymers like bacterial cellulose, polyhydroxyalkanoates or chitin; biosurfactants; biolubricants; or nanoparticles. This overview covers the latest trends in chemical, enzymatic and biotechnological processes reported in literature on the production of these chemicals and materials, with a focus on the use of FW as raw material.     

Sequential hydrogen and methane production using the residual biocatalyst of biodiesel synthesis as raw material

Residual Fermented Solid (RFS) is the used biocatalyst obtained after enzymatic biodiesel production carried out applying the fermented solid (FS) with lipase activity. Approximately 350 g of RFS are generated for each liter of biodiesel produced from palm residues fermented solid. In this study, this residue was used for the first time as a raw material for biological hydrogen production through dark fermentation and sequential application of the hydrogen production liquid waste (HPLW) for methane obtainment via anaerobic digestion. The RFS was composed mostly of oils and fats (60% wt.%), and carbohydrates, such as mannose, glucose, and xylose. Hydrogen yield reached 239 ± 44 mL H₂/L after 24 h of fermentation using 31 g_RFS/L at the beginning of the process. Additionally, 204 ± 13 mL CH₄/g COD were produced through the anaerobic digestion of HPLW, which represented 61% of efficiency.     

Stabilization of Polysaccharides During Alkaline Pre-Treatment of Wood Combined with Enzyme-Supported Extractions in a Biorefinery

Specific enzymes have demonstrated an ability to increase the possibilities for extracting wood polymers. Enzymatic treatment requires an open wood structure, which was achieved by extended impregnation of the wood. However, lignin and some of the hemicelluloses, primarily glucomannan, were lost during the impregnation. To improve the carbohydrate yield, three glucomannan modification agents—sodium borohydride, polysulphide, and anthraquinone—were used, which increased the yields of the impregnated materials from 76.6% to 89.6%, 80.0%, and 81.3%, respectively. Through the use of additives, most of the glucomannan could be retained in the wood while still allowing the enzymes to penetrate the wood and attack the polymers. The additives also increased the extraction yield from 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14%. Of the three stabilizing agents, sodium borohydride was the most efficient, providing the highest extraction yields.     

Valorization of byproducts from tropical fruits: Extraction methodologies,applications, environmental,and economic assessment: A review (Part 1: General overview of the byproducts,traditional biorefinery practices,and possible applications)

Tropical fruits represent one of the most important crops in the world. The continuously growing global market for the main tropical fruits is currently estimated at 84 million tons, of which approximately half is lost or wasted throughout the whole processing chain. Developing novel processes for the conversion of these byproducts into value‐added products could provide a viable way to manage this waste problem, aiming at the same time to create a sustainable economic growth within a bio‐economy perspective. Given the ever‐increasing concern about sustainability, complete valorization through a bio‐refinery approach, that is, zero waste concept, as well as the use of green techniques is therefore of utmost importance. This paper aims to report the status on the valorization of tropical fruit byproducts within a bio‐refinery frame, via the application of traditional methodologies, and with specific attention to the extraction of phenolics and carotenoids as bioactive compounds. The different types of byproducts, and their content of bioactives is reviewed, with a special emphasis on the lesser‐known tropical fruits. Moreover, the bioactivity of the different types of extracts and their possible application as a resource for different sectors (food, pharmaceutical, and environmental sciences) is discussed. Consequently, this review presents the concepts of tropical fruit biorefineries, and the potential applications of the isolated fractions.     

生物质精炼过程糖类分析方法研究进展

林基生物质精炼将更多的木材组分加以利用,转化为更多的化学制品和能量载体,实现林基生物质资源高效的工业化利用。其中关键技术在于传统造纸行业未充分利用的半纤维素。近年来国内外的科研机构和学者着力于半纤维素水解糖液的分析研究,其中基于现代仪器的分析方法为理论研究提供了更好的分析手段。本文作者根据文献调研总结了可服务于该新兴领域的分析方法,以期为研究者提供综合参考。     

A hybrid optimisation model for the synthesis of sustainable gasification-based integrated biorefinery

Depletion of fossil fuels and increasing public awareness of environmental issues has stimulated the search for alternative energy sources. Biofuels are recognised as one of the most promising alternatives to fossil fuels, as they can be produced from various types of feedstock. The efficiency and sustainability of biomass-based production can be maximised by producing biofuels along with other valuable coproducts in a “biorefinery”. This concept was proposed to make the production of biofuels and biochemicals more economically viable by taking advantage of opportunities for process integration and waste recovery. In this work, a novel hybrid optimisation model that combines superstructure-based optimisation approach and insight-based automated targeting for the synthesis of a sustainable integrated biorefinery is presented. In addition, fuzzy optimisation is also adapted to synthesize such integrated facility with the simultaneous consideration of both economic and environmental performance. Note that the proposed approach is a generic synthesis strategy that can be applied even without detailed modelling of individual processes.     

Synthesis of sustainable integrated biorefinery via reaction pathway synthesis: Economic,incremental enviromental burden and energy assessment with multiobjective optimization

With the increasing attention toward sustainable development, biomass has been identified as one of the most promising sources of renewable energy. To convert biomass into value‐added products and energy, an integrated processing facility, known as an integrated biorefinery is needed. To date, various biomass conversion systems such as gasification, pyrolysis, anaerobic digestion and fermentation are well established. Due to a large number of technologies available, systematic synthesis of a sustainable integrated biorefinery which simultaneously considers economic performance, environmental impact, and energy requirement is a challenging task. To address this issue, multiobjective optimization approaches are used in this work to synthesize a sustainable integrated biorefinery. In addition, a novel approach (incremental environmental burden) to assess the environmental impact for an integrated biorefinery is presented. To illustrate the proposed approach, a palm‐based biomass case study is solved. © 2014 American Institute of Chemical Engineers AIChE J, 61: 132–146, 2015