New challenges for syngas fermentation: towards production of biopolymers

Organic wastes are a suitable feedstock for the production of value‐added products that have been insufficiently exploited due to their complexity, which challenges their transformation by conventional procedures. Gasification and pyrolysis of organic wastes can reduce this complexity by producing syngas (CO plus H₂ and other C1 gases), which can be used as a valuable commodity by catalytic conversion into chemicals. However, the high cost and susceptibility to poisoning of chemical catalysts have encouraged research on biocatalysts that convert C1 components of syngas into different multi‐carbon compounds. Nowadays, research on syngas fermentation is receiving much attention in order to enhance the productivity of microorganisms by remodeling their metabolism and by optimizing the bioreactor operational conditions. This review highlights the new technical achievements of pyrolysis as well as the new biotechnological uses of syngas for the production of bulk chemicals and biopolymers, discussing the major bottlenecks that challenge syngas fermentation. © 2015 Society of Chemical Industry     

A review of the potential of pretreated solids to improve gas biofuels production in the context of an OFMSW biorefinery

The organic fraction of municipal solid waste (OFMSW), mainly composed of lignocellulosic polymers, is extremely complex. Therefore, it is necessary to apply pretreatments to remove the lignin content and decrease the cellulose crystallinity in order to use the OFMSW for gas biofuels production in the context of biorefineries from waste. This work focused on critically reviewing the conventional pretreatments applied to OFMSW, with the goal of improving the H₂ production, as well as other biofuels in modern biorefineries. There are a wide variety of pretreatments that have successfully been used, mainly alkaline, milling and dilute acid. In addition, some research has focused on the recovery and reutilization of the alkali, acid or solvents after the pretreatment, to be incorporated into new cycles of production, minimizing the environmental impacts. Moreover, it would be necessary to incorporate analytical tools, in order to determine the sustainability of the biorefinery project. It is concluded that waste pretreatments could significantly contribute to increased yields of biogas fuels in organic waste‐based biorefineries. Therefore, establishing preliminary stages for conditioning biomass or wastes is essential to improve the degradation of wastes and bio‐product generation. © 2016 Society of Chemical Industry     

糠醛制备工艺的研究进展

糠醛是一种天然的呋喃基化学品前体。然而,目前糠醛的工业生产依赖于比较陈旧、低效的生产工艺,导致容量小、产率低下。本文对过去和现在的糠醛生产工艺进行论述,以期提高由木质纤维素生物质生产糠醛的产量。首先,对糠醛催化转化制得的下游产品进行了概述。然后,本文探讨了由戊聚糖制备糠醛的形成和损失过程,以期能更好的提高糠醛的产量。最后,对一些据报道能提高糠醛产量的商业或学术生产工艺进行了讨论。     

Dark fermentation effectiveness as a key step for waste biomass refineries: influence of organic matter macromolecular composition and bioavailability

In next generation bio‐based refineries, hydrolysis and primary (or extractive) fermentations by undefined microbial cultures (UMC) are precursors of secondary bio‐transformations, in which H₂, CO₂ and mixed carboxylates are used as substrate for achieving added‐value target products (e.g. bio‐based chemicals, bio‐plastics and pigments). Dark fermentation (DF) is the most simple UMC‐driven hydrolysis and primary fermentations to extract gaseous and soluble mixtures of compounds from raw biomass. Which solid fractions (types of macro‐molecules) of mixed raw organic matter (OM) are efficiently hydrolyzed + fermented during DF is an aspect that was rarely considered in depth. Here, a first attempt was made to propose a new approach for understanding the effects of DF on different fractions of biomass. A set of seven different biomasses underwent optimized DF tests and, for simplicity, only the gaseous main product, i.e. bio‐hydrogen potential (BHP) production, was used as parameter to assess DF efficacy. BHP was studied in relation with OM characteristics: on one side, chemical composition (macro‐molecular fractions) and, on the other side, bioavailability to UMC attack (using two different biological assays). BHP was found significantly correlated (Pearson's test for p < 0.05, n = 7) only to acid detergent lignin (negatively), soluble sugars and sugars + starch (positively). Bioavailability was negatively correlated with fibrous fractions and to fat‐like fractions, but correlations with BHP were poorer (p > 0.05, n = 7). A statistical model (partial least square regression) was proposed for predicting BHP from OM characteristics, with interesting predictability. In the next future, the proposed approach should be widened to better understand the DF effectiveness not only referred to its gaseous products, but especially focusing on the wide range of soluble products (carboxylates), thought as substrates for secondary biorefinery. Copyright © 2015 John Wiley & Sons, Ltd.     

Hydrothermal Pretreatment of Lignocellulosic Materials for Improving Bioethanol Production

With the continued depletion of non-renewable energy resources,it is essential to seek new methods of harnessing clean and renewable energy.In this regard,second-generation bioethanol derived from lignocellulosic biomass has attracted increasing attention in recent years.The choice of the pretreatment method of lignocellulose is critical to the subsequent bioconversion processes.Compared with other conventional chemical pretreatment methods,hydrothermal pretreatment is a simple,low-cost,and economically feasible process that requires water as the only reagent.This paper reviews the research efforts that have been made toward hydrothermal pretreatment of lignocellulosic biomass and focuses on the transformations involving cellulose,hemicellulose,and lignin during this process.     

Implementation of a Forest Biomass-Based Biofuel Industry： A Canadian Experience

The forest biomass is an abundant renewable resource from which biofuels can be derived. In the Kraft process, the cellulose is extracted from the wood to form the paper pulp while the other organic components, primarily hemicelluloses and lignin, are burnt to produce steam. It is possible to divert part of the hemicelluloses or lignin to produce fuels on site, a mode of operation referred to as the integrated forest biorefinery. Hemicelluloses can be hydrolysed into sugars which in turn are converted into ethanol or butanol, while lignin can be extracted from a residual process stream, the black liquor, by acid precipitation, de-ionized, dried and directly used as a fuel or further processed into value added chemicals. Biorefinery processes have been proposed and analysed by simulation on Aspen Plus. Intensive integration of thermal energy, water and material systems is of paramount importance to the sustainability of the global site; the increased energy load on the utility systems could cause rising dependency of the global site on fossil fuels. To avoid this consequence, a new original energy efficiency analysis and enhancement methodology has been developed and validated on actual Canadian Kraft mills before being applied to the integrated biorefinery and, has produced remarkable results far superior to the current engineering practice. This has led to the concept of the GIFBR （green integrated forest biorefinery）, i.e., an industrial site with zero fossil fuel consumption and reduced GHG （greenhouse gases） emissions vs. the Kraft process and biorefinery plant alone. The GIFBR incorporates a woody biomass gasifier producing syngas as a fuel for the integrated biorefinery and for steam production or sale. It can also include a CHP （combined heat and power） unit driven by steam made available by liberated production capacity from the installed power plant.