In the context of climate change and the depletion of fossil fuels, there is a great need for alternatives to petroleum in the transport sector. This review provides an overview of the production of second generation bioethanol, which is distinguished from the first generation and subsequent generations of biofuels by its use of lignocellulosic biomass as raw material. The structural components of the lignocellulosic biomass such as cellulose, hemicellulose and lignin, are presented along with technological unit steps including pretreatment, enzymatic hydrolysis, fermentation, distillation and dehydration. The purpose of the pretreatment step is to increase the surface area of carbohydrate available for enzymatic saccharification, while minimizing the content of inhibitors. Performing the enzymatic hydrolysis releases fermentable sugars, which are converted by microbial catalysts into ethanol. The hydrolysates obtained after the pretreatment and enzymatic hydrolysis contain a wide spectrum of sugars, predominantly glucose and xylose. Genetically engineered microorganisms are therefore needed to carry out co-fermentation. The excess of harmful inhibitors in the hydrolysate, such as weak organic acids, furan derivatives and phenol components, can be removed by detoxification before fermentation. Effective saccharification further requires using exogenous hemicellulases and cellulolytic enzymes. Conventional species of distiller's yeast are unable to ferment pentoses into ethanol, and only a very few natural microorganisms, including yeast species like Candida shehatae, Pichia (Scheffersomyces) stipitis, and Pachysolen tannophilus, metabolize xylose to ethanol. Enzymatic hydrolysis and fermentation can be performed in a number of ways: by separate saccharification and fermentation, simultaneous saccharification and fermentation or consolidated bioprocessing. Pentose-fermenting microorganisms can be obtained through genetic engineering, by introducing xylose-encoding genes into metabolism of a selected microorganism to optimize its use of xylose accumulated in the hydrolysate.

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Review of Second Generation Bioethanol Production from Residual Biomass

Prioritizing and overcoming biomass energy barriers: Application of AHP and G-TOPSIS approaches

Cheese whey constitutes one of the most polluting by-products of the food industry, due to its high organic load. Thus, in order to mitigate the environmental concerns, a large number of valorization approaches have been reported; mainly targeting the recovery of whey proteins and whey lactose from cheese whey for further exploitation as renewable resources. Most studies are predominantly focused on the separate implementation, either of whey protein or lactose, to configure processes that will formulate value-added products. Likewise, approaches for cheese whey valorization, so far, do not exploit the full potential of cheese whey, particularly with respect to food applications. Nonetheless, within the concept of integrated biorefinery design and the transition to circular economy, it is imperative to develop consolidated bioprocesses that will foster a holistic exploitation of cheese whey. Therefore, the aim of this article is to elaborate on the recent advances regarding the conversion of whey to high value-added products, focusing on food applications. Moreover, novel integrated biorefining concepts are proposed, to inaugurate the complete exploitation of cheese whey to formulate novel products with diversified end applications. Within the context of circular economy, it is envisaged that high value-added products will be reintroduced in the food supply chain, thereby enhancing sustainability and creating “zero waste” processes.

https://www.mdpi.com/2304-8158/8/8/347/pdf

Cheese Whey Processing: Integrated Biorefinery Concepts and Emerging Food Applications.

Biofuels journey in Europe: Currently the way to low carbon economy sustainability is still a challenge

Background Soy whey is a by-product generated from both tofu and soy protein isolate production. This by-product contains a substantial amount of nutrients consisting of proteins, simple sugars, oligosaccharides, minerals, and soy isoflavones. Soy whey is commonly disposed of into the sewage after it is generated, and this pollutes water bodies. Scope and approach Researchers from various countries have explored the valorization of soy whey for value-add or value creation in addition to mitigate the environmental pollution. This review article aims to evaluate the current status of soy whey valorization research and the learning points that can be adapted from the dairy whey valorization research which are more extensively studied than soy whey valorization research. Various methods of soy whey utilization are discussed, which can be broadly classified into two categories: physical and microbiological/enzymatic. Physical methods include the recovery of the nutrients (eg. isoflavone, protein and minerals) and the production of various functional ingredients (eg. emulsifiers), whereas microbiological/enzymatic methods include the production of functional ingredients using microorganisms and enzymes (eg. prebiotic and citric acid), propagation of microorganisms (eg. probiotics) as well as biofuel production. Key findings and conclusions Even though there have been various efforts in valorizing soy whey, most of these studies still generate a significant amount of waste at the end of the processes. Therefore, there is a need to find an efficient method to significantly valorize soy whey without significant residual waste or generation of new waste and dairy whey valorization technologies may serve as a template for efficient soy whey valorization.

Soy whey: More than just wastewater from tofu and soy protein isolate industry

Nowadays, biomass is considered as one of the main sources of energy for both developed and developing countries. With the reduction of global oil reserves, developing renewable energy has become an important issue for each country. Biomass power is an important kind of clean energy, as it has abundant resource and is environmentally friendly. Utilization of biomass for bioenergy production is a beneficial alternative to meet the increasing energy demands, reduce the carbon dioxide emission, global warming and climate change. In the past few years, the biomass power industry has developed rapidly, accompanied with some problems. They are currently making small profits or suffering losses, and the entire biomass supply chain does not function well, which not only poses a challenge for the stable operation of enterprises but also may impact the smooth development of the biomass power industry. Lack of optimization biomass residue makes the countries still low in utilization of biomass therefore most of industries are not aware this benefit and they are reluctant to take the risk on utilization of biomass for power generation. This paper summarized the bioenergy production potential of various categories of biomass used and their conversion processes adopted in different part of the world; specifically in Asian and European countries. A brief description of the processes for conversion of identified biomass feedstock to energy and fuels has also been included. In addition, the sustainability issues related to supply chain management concerning operational, economic and social aspects of the utilization of biomass have been addressed based on the secondary data from available literature. Finally, this paper offered several recommendations for future development on the relevant fields, such as cost, strategic planning, and policy implication. This project has specific importance and very few studies have been done which reviews the biomass supply chain of Asian and European countries.

Biomass Supply Chain in Asian and European Countries

Whey, a major byproduct of the cheese and dairy industry, has valuable nutritional constituents but poses a major environmental risk, if disposed off without prior treatment. Whey has a high organic content, its major constituent being lactose (4.5-5% w/v). With a very high BOD and COD load (30,000 – 50,000 ppm and 60.000 – 80,000 ppm respectively) and annual production of over 160 million tonnes, with an estimated growth rate of 1–2% yearly, fermentation of whey to bioethanol has proved to be a lucrative option, both for bioremediation of whey and production of ethanol from waste sources; reducing the costs incurred in otherwise advanced effluent treatment processes required for its disposal. Moreover, with increasing global demand for bioethanol as an alternative to scarce fossil fuels and advocacy by governmental institutions, due to its non-polluting nature aiding in reduced environmental pollution and global warming; conversion of whey to ethanol is progressively more desirable. The aim of this review is to discuss the supply chain involved in the production of ethanol from whey. The study will involve literature survey, experimentation and developing a model. This study looks at the supply chain involved in the production and subsequent distribution of whey, for the purpose of valorization and extraction of valuable constituents, as well as its utilization in production of bioethanol. Based on existing studies, it has been seen that an initial lactose concentration of 200 gL -1 in the whey permeate, provides the maximum yield for ethanol. Under such conditions, maximum ethanol obtained from fermentation of whey was found to be 80.95 kg m -3 , proving the economic viability of the process. However, the supply chain of whey for bioethanol production is not well defined, making effectiveness and implementation of ethanol production from whey constricted. Thus, although the environmental risk posed by the vast production of whey, is mitigated by its conversion to ethanol, providing adequate bioremediation of its polluting components, this process is yet to be industrialized widely.

Supply Chain of Bioethanol Production from Whey: A Review

Microbial fuel cells (MFCs) have attracted widespread interest due to their capability to generate power while treating wastewater. In the present investigation, rice mill wastewater (RMW) was treated in a dual-chamber MFC with a biological cathode (MFCB), in which anaerobic treatment was provided in the anode compartment, and aerobic treatment was enployed in the cathode compartment. The performance was compared with an identical MFC with an abiotic cathode (MFCA). During continuous operation, the hydraulic retention time (HRT) of the anode compartments of both MFCs was kept at 12 h. The maximum volumetric power density obtained in MFCB (379.53 mW/m3) was lower than MFCA (791.72 mW/m3). Similarly, the maximum open-circuit voltage (OCV) and operating voltages were 0.519 V and 0.170 V for MFCB, while for the MFCA, they were 0.774 V and 0.251 V, respectively. The internal resistance of MFCA was 372.34 Ω while the MFCB showed a higher internal resistance of 533.89 Ω. The linear sweep voltammetry and cyclic voltammetry also demonstrated high electrochemical activity in MFCA compared to MFCB. However, MFCB has shown a higher chemical oxygen demand (COD) removal efficiency (96.8%) than MFCA (88.4%) under steady-state conditions. Both anaerobic and aerobic degradation of organic substrates significantly reduced the COD of RMW. Furthermore, the absence of an expensive catalyst in the cathode substantially reduces the cost of the system. The electrical performance of the system can be enhanced by employing novel cathode material with surface modification.

Aryama Raychaudhuri

Papers

Biomass Supply Chain in Asian and European Countries

Supply Chain of Bioethanol Production from Whey: A Review

Sequential anaerobic-aerobic treatment of rice mill wastewater and simultaneous power generation in microbial fuel cell.

Biodegradation and power production kinetics in microbial fuel cell during rice mill wastewater treatment

Effect of operating parameters on rice mill wastewater treatment in an acidogenic chamber and MFC coupled system