Journal of Scientific & Industrial Research

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Hemicellulose biorefineries: a review on biomass pretreatments

Florbela Carvalheiro, Lus C Duarte & Francisco M Grio

Biomass pretreatment (BP) plays a crucial role in a lignocellulose feedstock-based biorefinery (LCFBR) for processing of three major output streams (cellulose, hemicelluloses and lignin) into chemicals and biofuels. BP includes processing of lignocellulosic material (LCM) under aqueous, dilute acid or alkaline media to obtain a cellulosic fraction, which is then fermented to produce bioethanol. This review provides BPs assuming that hemicellulose stream should be integrated in LCFBR as a primary fraction for converting into value-added compounds other than bioethanol. Different LCM treatments are analyzed foreseeing bio-based products possible to obtain from hemicellulose path.


Recent developments of key technologies on cellulosic ethanol production

Jin-Suk Lee, Binod Parameswaran,
Joon-Pyo Lee & Soon-Chul Park

Conversion of lignocellulosic biomass to fuel ethanol involves pretreatment process followed by enzyme-catalyzed hydrolysis to make fermentable sugars. Efficient pretreatment method can significantly enhance hydrolysis of biomass and hence can reduce ethanol cost. Optimization of enzyme loading and selection of suitable fermentation technique based on biomass will further improve ethanol yield. Present review focuses on various pretreatment techniques based on composition of lignocellulosic biomass and also discuss simultaneous saccharification and co-fermentation and co-immobilization for cellulosic ethanol production.


Realistic approach for full-scale bioethanol production from lignocellulose: a review

E Toms-Pej, J M Oliva & M Ballesteros

This paper reviews current status of bioethanol production including substrates, fermenting microorganisms and technology for a full-scale process development. Considering main drawbacks, several parameters (high substrate loadings, sugar recovery after pretreatment, tolerance to inhibitory compounds and xylose fermentation by yeast) must be optimized for a successful industrial process for bioethanol production from lignocellulose.



Energy and greenhouse gas balances of biofuels: biases induced by LCA modelling choices

E Gnansounou, A Dauriat, L Panichelli &
J Villegas

Estimating greenhouse gas (GHG) balances of biofuels is subject to significant biases stemming from modelling choices about system definition and boundaries, functional unit, reference systems and allocation methods. This paper investigates extent to which these choices influence the results. After performing a comparison and constructive criticism of various modelling choices, life cycle assessment (LCA) of wheat-to-bioethanol was used as an illustrative case where bioethanol was blended with gasoline at various percentages (E5, E10 and E85). A large difference was observed in reduction of GHG emissions with a high sensitivity to method used to allocate impacts between co-products, type of reference systems, choice of functional unit and type of blend.


Progress in research on fungal cellulases for lignocellulose degradation

Gincy Marina Mathew, Rajeev K Sukumaran, Reeta Rani Singhania & Ashok Pandey

Fungal cellulases offer advantages of a secreted enzyme complex and relative easiness and economy of producing enzyme. Considerable amount of work has been done on fungal cellulases, especially with resurgence of interest in biomass-ethanol and concept of bio-refineries. Significant information has also been gained on basic biology of organisms producing cellulases, and in process development for enzyme production and biomass saccharification. This review addresses developments in the field of fungal cellulases for lignocellulose degradation.


Lignocellulosics-to-bioethanol in the context of Germany: Modelling life cycle implications of policy options

Witold-Roger Poganietz, Tim Reinhardt & Christian Bauer

This paper compares lignocellulosic based bioethanol to traditional bioethanol regarding environmental impact focussing on greenhouse gases, considering manifold opportunities to use biomass and competitive stance to fossil energy carriers. Using a market processes simulating technique-based process chain model, it is observed that environmental impact of ligno-bioethanol depends crucially on market conditions, although relevance of market constraints varies.


Brazilian potential for biomass ethanol: Challenge of using hexose and pentose co-fermenting yeast strains

Boris U Stambuk, Elis C A Eleutherio,
Luz Marina Florez-Pardo,
Ana Maria Souto-Maior & Elba P S Bon

This paper reviews Brazilian scenario and efforts for deployment of technology to produce bioethanol vis--vis recent international advances in the area, including possible use of hexose and pentose co-fermenting yeast strains.



Techno-economic and environmental evaluation of lignocellulosic biochemical refineries: need for a modular platform for integrated assessment (MPIA)

Juan David Villegas & Edgard Gnansounou

A promising general model for a lignocellulosic biochemical refineries (LCBR) is based on sugar-lignin platform, in which 5-carbon (C5) and 6-carbon (C6) sugars, resulting from lignocellulosic matrix fractionation, are converted into fuels and building block chemicals by biotechnological or chemical pathways. In this context, comprehensive, flexible and dynamic modelling approaches are needed to solve a problem with multiple optimization criteria (economic and environmental), high levels of uncertainty and dynamic behaviour. Process simulators and comprehensive databases of production processes can help to determine rigorous and thermodynamically consistent material and energy balances permitting robust scale-up and reducing uncertainty in economical and environmental impact evaluation in a dynamic context. This paper discusses the need for developing a modular platform for process synthesis aiming at selection of technically, economically and environmentally sound pathways for lignocellulosic biorefineries.



Design of bioreactors for biohydrogen production

K Y Show
, Z P Zhang & D J Lee

Using dark fermentation, hydrogen can be generated from renewable organics including waste materials. Key to successful application of anaerobic fermentation is to uncouple liquid and biomass retention times in reactor system. This paper reviews reactor configurations (fixed-bed, fluidized-bed, upflow anaerobic sludge blanket and continuous stirred tank reactors) and operating processes (batch, semi-continuous and continuous). Immobilized- and suspended- cell systems are compared based on biomass growth in forms of granular, biofilm, gel-entrapped bioparticle and flocs.


Fermentative hydrogen production with simultaneous wastewater treatment: influence of pretreatment and system operating conditions

S Venkata Mohan

H2 is a sustainable and viable form of green/alternative energy source. This study reviews the work on H2 production from wastewater treatment pertaining to inoculum pretreatment and system operating conditions. Process was evaluated and discussed based on pretreatment procedures applied on mixed parent anaerobic culture to selectively enrich acidogenic culture, operating pH and retention time (HRT) in concurrence with wastewater type as substrate.



Outlook of biohydrogen production from lignocellulosic feedstock using dark fermentation a review

Ganesh D. Saratale, Shing-Der Chen,
Yung-Chung Lo, Rijuta G Saratale, &
Jo-Shu Chang

The main challenges are the low hydrogen yield arising from poor efficiency on direct microbial assimilation of cellulosic materials. Development of novel and effective cellulase enzymes, optimization and improvement of cellulase system, as well as engineering approaches on cellulose pretreatment and saccharification are gaining increasing interest. Information from genomics and molecular genetics combined with improved genetic engineering offer a wide range of possibilities for enhancing performance of cellulose feedstock utilization and biohydrogen production. This study reviews key technologies and variables to be considered during biohydrogen production from lignocellulosic feedstock.


Status of Biological hydrogen production

Uttam Sen, Manish Shakdwipee &
Rangan Banerjee

This paper analyzes yields, reaction rates and reactor designs, and compares effectiveness of different substrate- microorganism combinations. Net energy analysis of processes reveals directions for viability and screening of options. Techniques like metabolic flux analysis can be used to establish targets for increased yields. Factors influencing production and possibility of using genetic engineering to increase production rates are discussed. The paper identifies gaps and possible directions for future development of biological hydrogen production.


Biohydrogen production: molecular aspects

Lemi Trker, Seluk Gmş & Alper Tapan

This study reviews biohydrogen systems, molecular and genetic aspects of hydrogen production and technologies of biohydrogen production. An enormous investment is needed to understand hydrogen-producing mechanisms better in cells of microorganisms at molecular level on evolution of artificial organisms, which could produce abundant, at least satisfactory, quantities of hydrogen with a suitable rate of production.



Estimating greenhouse gas emissions from indirect land-use change in biofuels production: concepts and exploratory analysis for soybean-based biodiesel production

Luis Panichelli & Edgard Gnansounou

Due to changes in carbon stock of soil and biomass, indirect land-use change (ILUC) has consequences on green house gas (GHG) balance of a biofuel that are not presently considered in evaluation of environmental merits of biofuels. Significant changes in land-use are expected to occur in biofuel producing countries and their consequences may affect global markets. This paper aims to: 1) Review state-of- art of accounting for indirect effects in biofuels production and their influence on GHG balance of a biofuel pathway; 2) Present a model to estimate and optimize GHG emissions from LUC; and 3) Estimate potential GHG emissions for the case of soybean-based biodiesel production. ILUC concepts and a classification of ILUC sources are proposed. Using a system-wide approach and a non-linear programming (NLP) model, GHG emissions are evaluated in terms of carbon pay back time and optimized based on soybean supply strategy to produce biodiesel.


PAH and other emissions from coconut oil blended fuels

M A Kalam, M G Saifullah, H H Masjuki,
M Husnawan & T M I Mahlia

This paper presents results of a multi-cylinder diesel engine operated on blends of ordinary coconut oil (COCO; 10%, 20%, 30%, 40%, 50%) with ordinary diesel oil (OD). Methyl esters from cooking oil are less encouraging to be used as biofuel because this affects food-fuel crisis. However, biofuel obtained from waste cooking oil is more appreciated due to energy savings and environmental issues. Test results indicated that COCO blended fuels (10-30 %) produced similar brake power and net heat release rate as OD. Increasing coconut oil in blend decreases exhaust emissions. Carbon deposited on injector nozzles was observed where no hard carbon was found on injector tip when engine run on COCO blends.

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