Opportunities, recent trends and challenges of integrated biorefinery: Part II

Availability of cost-competitive biomass conversion technologies plays crucial role for successful realization of biorefinery for sustainable production of fuels and organic chemicals from biomass. The present article provides an outline of opportunities and socio-techno-economic challenges of various biomass processing technologies. The biomass processing technologies were classified into three broad categories: thermochemical, chemical and biochemical. This review article presents an overview of two potential thermochemical conversion processes, gasification and fast pyrolysis, for direct conversion of lignocellulosic biomass. The article further provides a brief review of chemical conversion of triglycerides by transesterification with methanol for production of biodiesel. The highly productive microalgae as an abundant source of triglycerides for biodiesel and various other fuels products were also reviewed. The present article also provides an outline of various steps involved in biochemical conversion of carbohydrates to alcoholic bio-fuels, bio-ethanol and bio-butanols and conversion of nature׳s most abundant aromatic polymer, lignin, to value-added fuels and chemicals. Furthermore, an overview of production of hydrocarbon fuels through various biomass processing technologies such as hydrodeoxygenation of triglycerides, biosynthetic pathways and aqueous phase catalysis in hydrocarbon biorefinery were highlighted. The present article additionally provides economic comparisons of various biomass conversion technologies

Opportunities, Recent Trends and Challenges of Integrated Biorefinery: Part I

Sustainable production of energy, fuels, organic chemicals and polymers from biomass in an integrated biorefinery is extremely important to reduce enslavement on limited fossil fuels. In the present article, the biomass was classified into four general types based on their origin: energy crops, agricultural residues and waste, forestry waste and residues and industrial and municipal wastes. The article further elucidates the chemistry of various types of biomass used in the biorefinery. The biorefinery was classified into three broad categories based on the chemistry of biomass: triglyceride, sugar and starchy and lignocellulosic. The article further presents a comprehensive outlines of opportunities and recent trends of each type of biorefinery. A brief overview of original and revised list of platform chemicals, their sources from biomass and derivative potentials were also articulated. The article also provides comparisons of different types of biorefinery, broad challenges and availability of biomass. Furthermore, the article provides an overview of hydrocarbon biorefinery for production of hydrocarbon fuels and building block chemicals from biomass

Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology

Lactic acid (LA) is a vital platform chemical with diverse applications, especially for biodegradable polylactic acid. Bread waste (BW) is sugar-rich waste biomass generated in large quantities in residential and commercial operations. Recently, we evaluated the potential of BW for LA production by Bacillus coagulans under non-sterile conditions. This work presents a techno-economic and profitability analysis for valorizing 100 metric tons of BW per day to alleviate environmental pollution with concurrent production of LA and biomethane. We compared two fermentation approaches: acid-neutral (Scenario I) and low pH (Scenario II). Traditional esterification with methanol, followed by hydrolysis of methyl lactate, was employed for downstream separation to obtain polymer-grade LA. High-pressure steam was generated from solid debris via anaerobic digestion to complement energy demands partly. Energy consumption was further attenuated by process integration using pinch technology, with around 15% and 11% utility cost savings for Scenario I and II, respectively. These processes were capital-intensive, with 42-46% of LA production cost stemming from direct and indirect costs. Utilities were the major cost-contributing factor (19-21%) due to energy-intensive water evaporation from dilute fermentation broth. Due to additional processing steps, capital investment and operating costs were slightly higher in Scenario I than in Scenario II. LA manufacturing cost was thus more for Scenario I ($2.07 per kg) than Scenario II ($1.82 per kg). The minimum LA selling price for Scenario I and II were $3.52 and$3.22 per kg, respectively, with five-year payback periods and 8.5% internal rates of return. LA was slightly more expensive for decentralized BW processing than the market price

Life Cycle Assessment of Microbial 2,3-Butanediol Production from Brewer’s Spent Grain Modeled on Pinch Technology

Microbial production of 2,3-butanediol (BDO) has received considerable attention as a promising alternate to fossil-derived BDO. In our previous work, BDO concentration >100 g/L was accumulated using brewer’s spent grain (BSG) via microbial routes which was followed by techno-economic analysis of the bioprocess. In the present work, a life cycle assessment (LCA) was conducted for BDO production from the fermentation of BSG to identify the associated environmental impacts. The LCA was based on an industrial-scale biorefinery processing of 100 metric tons BSG per day modeled using ASPEN plus integrated with pinch technology, a tool for achieving maximum thermal efficiency and heat recovery from the process. For the cradle-to-gate LCA, the functional unit of 1 kg of BDO production was selected. One-hundred-year global warming potential of 7.25 kg CO2/kg BDO was estimated while including biogenic carbon emission. The pretreatment stage followed by the cultivation and fermentation contributed to the maximum adverse impacts. Sensitivity analysis revealed that a reduction in electricity consumption and transportation and an increase in BDO yield could reduce the adverse impacts associated with microbial BDO production

Techno-Economic Analysis of 2,3-Butanediol Production from Sugarcane Bagasse

Sugarcane bagasse (SCB) is a significant agricultural residue generated by sugar mills based on sugarcane crop. Valorizing carbohydrate-rich SCB provides an opportunity to improve the profitability of sugar mills with simultaneous production of value-added chemicals, such as 2,3-butanediol (BDO). BDO is a prospective platform chemical with multitude of applications and huge derivative potential. This work presents the techno-economic and profitability analysis for fermentative production of BDO utilizing 96 MT of SCB per day. The study considers plant operation in five scenarios representing the biorefinery annexed to a sugar mill, centralized and decentralized units, and conversion of only xylose or total carbohydrates of SCB. Based on the analysis, the net unit production cost of BDO in the different scenarios ranged from 1.13 to 2.28 US$/kg, while the minimum selling price varied from 1.86 to 3.99 US$/kg. Use of the hemicellulose fraction alone was shown to result in an economically viable plant; however, this was dependent on the condition that the plant would be annexed to a sugar mill which could supply utilities and the feedstock free of cost. A standalone facility where the feedstock and utilities were procured was predicted to be economically feasible with a net present value of about 72 million US$, when both hemicellulose and cellulose fractions of SCB were utilized for BDO production. Sensitivity analysis was also conducted to highlight some key parameters affecting plant economics

Correlation of solubility of single gases/hydrocarbons in polyethylene using PC-SAFT

The knowledge of solubility of gases and hydrocarbons in polymer has enormous importance in the design and development of reactor, polymer foaming, and membrane separation processes. In this work, the solubility of gases and hydrocarbons in polyethylene was correlated using a thermodynamic model based on perturbed-chain statistical associating fluid theory (PC-SAFT). The experimental solubility data of various gases such as ethylene, carbon dioxide, nitrogen, methane, and hydrocarbons of up to chain length of seven in both molten and semicrystalline polyethylene has been reviewed and the suitability of the developed model based on PC-SAFT was then tested using the available solubility data in literatures for various gases and hydrocarbons. Furthermore, the optimum values of adjustable solvents-solute binary interaction parameters (Kij) of PC-SAFT at different temperatures have been estimated by regression of the PC-SAFT model using experimental solubility isotherms. A suitable correlation of Kij with temperature was then developed using the estimated Kij at different temperatures. The solubility calculated from the developed model using the estimated Kij was then compared to the experimental results and a reasonably good correlation was observe

Steam reforming of isobutanol for the production of synthesis gas over Ni/g-Al2O3 catalysts

Bio-isobutanol has received widespread attention as a bio-fuel and a source of chemicals and synthesis gas as part of an integrated biorefinery approach. The production of synthesis gas by steam reforming (SR) of isobutanol was investigated in a down-flow stainless steel fixed-bed reactor (FBR) over Ni/g-Al2O3 catalysts in the temperature range of 723–923 K. The NiO/g-Al2O3 catalysts were prepared by the wet impregnation method and reduced in the FBR prior to the reaction. The surface area, metal dispersion, crystalline phase, and reducibility of the prepared catalysts were determined using BET, chemisorption, XRD and TPR, respectively. From the TPR studies, the maximum hydrogen consumption was observed in the temperature range of 748–823 K for all the catalysts. The presence of nickel species was confirmed through the characterization of the catalysts using powder XRD. The time-on-stream (TOS) studies showed that the catalysts remained fairly stable for more than 10 h of TOS. The conversion of carbon to gaseous products (CCGP) was increased by increasing the nickel loading on g-Al2O3 and the temperature and by decreasing the weight hourly space velocity (WHSV). The hydrogen yield was increased by increasing the nickel loading on g-Al2O3, the WHSV, the steam-to-carbon mole ratio (SCMR), and the temperature. The selectivity to methane decreased at high reaction temperatures and SCMRs. The selectivity to CO decreased with increasing SCMRs and decreasing temperatures. The work was further extended to the thermodynamic equilibrium analysis of the SR of isobutanol under experimental conditions using Aspen Plus, and the equilibrium results were then compared to the experimental results. A reasonably good agreement was observed between the trends in the equilibrium and the experimental results

Roles of supports (γ-Al2O3, SiO2, ZrO2) and performance of metals (Ni, Co, Mo) in steam reforming of isobutanol

The production of synthesis gas from bio-isobutanol in an integrated biorefinery is a novel approach for its downstream conversion to hydrocarbon fuels and organic chemicals. The present article provides a systematic examination of the structure–activity correlation of various supported transition metal catalysts, xMS (x mmol metal, M (Ni, Co, and Mo) supported on S (Al, Si, and Zr for γ-Al2O3, SiO2, and ZrO2 respectively)) for steam reforming (SR) of bio-isobutanol. The activity of the catalyst was strongly influenced by metal-support interaction as reflected by metal dispersion, metal crystallite size, and extent of bulk metal/metal oxide. The catalytic activity increased in the order of 4.3NiZr < 4.3NiSi < 4.3NiAl and 4.3MoAl < 4.3CoAl < 4.3NiAl. 7.3CoAl exhibited consistent catalytic activity up to 12 h of time-on-stream. The hydrogen yield was boosted with rise of temperature and steam-to-carbon mole ratio (SCMR) with concurrent drop of selectivity to methane. The selectivity to CO reduced with increasing SCMR and decreasing temperature. Furthermore, spent catalysts were characterized to elucidate the effect of metal and support on the nature of coke formed and chemical transformation of the catalyst during SR

Kinetics of hydrodeoxygenation of octanol over supported nickel catalysts: a mechanistic study

The hydrodeoxygenation (HDO) of 1-octanol as a model aliphatic alcohol of bio-oil was investigated in a continuous down-flow fixed-bed reactor over γ-Al2O3, SiO2, and HZSM-5 supported nickel catalysts in the temperature range of 488–533 K. The supported nickel catalysts were prepared by incipient wetness impregnation method and characterized by BET, XRD, TPR, TPD, H2 pulse chemisorption, and UV-vis spectroscopy. Characterization of supported nickel (or nickel oxide) catalysts revealed existence of dispersed as well as bulk nickel (or nickel oxide) depending on the extent of nickel loading and the nature of the support. The acidity of γ-Al2O3 supported nickel catalysts decreased with increasing the nickel loading on γ-Al2O3. n-Heptane, n-octane, di-n-octyl ether, 1-octanal, isomers of heptene and octene, tetradecane, and hexadecane were identified as products of HDO of 1-octanol. The C7 hydrocarbons were observed as primary products for catalysts with active metal sites such as γ-Al2O3 and SiO2 supported nickel catalysts. However, C8 hydrocarbons were primarily formed over acidic catalysts such as pure HZSM-5 and HZSM-5 supported nickel catalyst. The 1-octanol conversion increased with increasing nickel loading on γ-Al2O3, and temperature and decreasing pressure and WHSV. The selectivity to products was strongly influenced by temperature, nickel loading on γ-Al2O3, pressure, and types of carrier gases (nitrogen and hydrogen). The selectivity to C7 hydrocarbons was favoured over catalysts with increased nickel loading on γ-Al2O3 at elevated temperature and lower pressure. A comprehensive reaction mechanism of HDO of 1-octanol was delineated based on product distribution under various process conditions over different catalysts