Techno-economic analysis of ethanol production from lignocellulosic biomass-a comparison of fermentation, thermo catalytic, and chemocatalytic technologies.

Bioethanol produced from 2nd generation biomass comprising of agricultural residues and forest wastes is a viable alternate fuel. Besides fermentation and biomass gasification to syngas and its further conversion to ethanol, a direct chemocatalytic conversion of lignocellulosic biomass into ethanol is being investigated as a viable route which avoids the emission of greenhouse gases. In this work, a detailed configuration of chemocatalytic route is simulated and optimized for minimizing the cost of ethanol production. The economic feasibility of ethanol production through the chemocatalytic pathway is analyzed. The techno-economic analysis is conducted in terms of ethanol selectivity and ethanol production cost. The obtained results show that biomass feedstock and catalyst have major contributions to the production cost. The proposed route is found to be giving a lower ethanol selling price as compared to the well-researched routes of biomass fermentation to ethanol and biomass gasification followed by syngas conversion to ethanol.

Downstream processing of lignin derived feedstock into end products.

Despite the enormous research efforts in recent years regarding lignin depolymerisation and functionalisation, few commercial products are available. This review provides a summary and viewpoint of extensive research in the lignin-to-product valorisation chain, with an emphasis on downstream processing of lignin derived feedstock into end products. It starts with an introduction of available platform chemicals and polymeric derivatives generated from lignin via existing depolymerisation and functionalisation technologies. Following that, detailed analyses of various strategies for the downstream processing of lignin derived platform chemicals and materials into fuels, valued-added chemicals and functional polymers are provided. A concise techno-economic analysis of various downstream processes is conducted based on the market demand of the end product, economic potential and technological readiness, enabling the identification of processes that are potentially both economically competitive and commercially feasible, and shedding light on processes which deserve further technological development. We wish this review will stimulate further advances in the sustainable production of value-added products from lignin to integrate this invaluable "bio-waste" into the chemical/materials supply chain.

Lignocellulosic biomass: Hurdles and challenges in its valorization.

Lignocellulosic biomass (LCB) is globally available and sustainable feedstock containing sugar-rich platform that can be converted to biofuels and specialty products through appropriate processing. This review focuses on the efforts required for the development of sustainable and economically viable lignocellulosic biorefinery to produce carbon neutral biofuels along with the specialty chemicals. Sustainable biomass processing is a global challenge that requires the fulfillment of fundamental demands concerning economic efficiency, environmental compatibility, and social responsibility. The key technical challenges in continuous biomass supply and the biological routes for its saccharification with high yields of sugar sources have not been addressed in research programs dealing with biomass processing. Though many R&D endeavors have directed towards biomass valorization over several decades, the integrated production of biofuels and chemicals still needs optimization from both technical and economical perspectives. None of the current pretreatment methods has advantages over others since their outcomes depend on the type of feedstock, downstream process configuration, and many other factors. Consolidated bio-processing (CBP) involves the use of single or consortium of microbes to deconstruct biomass without pretreatment. The use of new genetic engineering tools for natively cellulolytic microbes would make the CBP process low cost and ecologically friendly. Issues arising with chemical characteristics and rigidity of the biomass structure can be a setback for its viability for biofuel conversion. Integration of functional genomics and system biology with synthetic biology and metabolic engineering undoubtedly led to generation of efficient microbial systems, albeit with limited commercial potential. These efficient microbial systems with new metabolic routes can be exploited for production of commodity chemicals from all the three components of biomass. This paper provides an overview of the challenges that are faced by the processes converting LCB to commodity chemicals with special reference to biofuels.

Industrial lignin from 2G biorefineries - Assessment of availability and pricing strategies.

With a view to boost practical implementation of lignin conversion technologies, this paper assesses the availability of industrial lignin and evaluates pricing strategies applicable to multi-product biorefineries. The biorefineries, producing either denatured ethanol or sugar hydrolysate as a main product, can yield 43% and 61% of lignin residue (LR) comprising 33% and 23% of lignin by mass, respectively, without sacrificing the output of the main product and before electricity import has become indispensable. Analysis of the pricing strategies reveals that LR must be treated as a low-value by-product, and its minimum selling price (MSP) is driven mainly by the prevailing electricity price. Under the biorefinery net zero energy balance, and taking into account the LR market price adequacy, as well as the main probabilistic conditions, the upper range for the MSP is calculated at $43-70 and $18-37 per ton for biorefineries producing ethanol and hydrolysate, respectively.

Mushroom cultivation in the circular economy.

Commercial mushrooms are produced on lignocellulose such as straw, saw dust, and wood chips. As such, mushroom-forming fungi convert low-quality waste streams into high-quality food. Spent mushroom substrate (SMS) is usually considered a waste product. This review discusses the applications of SMS to promote the transition to a circular economy. SMS can be used as compost, as a substrate for other mushroom-forming fungi, as animal feed, to promote health of animals, and to produce packaging and construction materials, biofuels, and enzymes. This range of applications can make agricultural production more sustainable and efficient, especially if the CO2 emission and heat from mushroom cultivation can be used to promote plant growth in greenhouses.

Effect of different lignocellulosic wastes on Hericium americanum yield and nutritional characteristics.

BACKGROUND: The aim of this study was to investigate the possibility of using cottonseed hulls (CSH) and olive press cake (OPC) as new supplement materials for substrate preparation in Hericium americanum cultivation. Some chemical properties of the substrates prepared by mixtures of oak sawdust (OS) with wheat bran (WB), CSH and OPC in different ratios were determined. In addition, the effect of mixtures of OS:CSH and OS:OPC on spawn run time, yield and biological efficiency (BE), average mushroom weight and nutrition content of the fruiting body were compared with the control substrate (8OS:2WB). RESULTS: The yield, BE and average mushroom weight of substrates containing CSH and OPC were higher than the control substrate and increased with an increase in the rate of CSH and OPC in the mixtures. Hericium americanum showed (on a dry weight basis) 8.5-23.7% protein, 9.9-21.2 g kg-1 P, 26.6-35.8 g kg-1 K, 0.63 - 1.33 g kg-1 Mg, 0.19 - 0.23 g kg-1 Ca, 1.34-1.78 g kg-1 Na, 49.5-72.2 mg kg-1 Fe, 6.22-10.11 mg kg-1 Mn, 32.8-82.8 mg kg-1 Zn and 8.6-11.2 mg kg-1 Cu on different growing substrates. The nutritional value of mushrooms was greatly affected by the growing media. CONCLUSION: The results revealed that CSH and OPC could be used as new supplement materials for substrate preparation in H. americanum cultivation. © 2016 Society of Chemical Industry.

Techno-economic comparison of biojet fuel production from lignocellulose, vegetable oil and sugar cane juice.

In this study, a techno-economic comparison was performed considering three processes (thermochemical, biochemical and hybrid) for production of jet fuel from lignocellulosic biomass (2G) versus two processes from first generation (1G) feedstocks, including vegetable oil and sugar cane juice. Mass and energy balances were constructed for energy self-sufficient versions of these processes, not utilising any fossil energy sources, using ASPEN Plus® simulations. All of the investigated processes obtained base minimum jet selling prices (MJSP) that is substantially higher than the market jet fuel price (2-4 fold). The 1G process which converts vegetable oil, obtained the lowest MJSPs of $2.22/kg jet fuel while the two most promising 2G processes- the thermochemical (gasification and Fischer-Tropsch synthesis) and hybrid (gasification and biochemical upgrading) processes- reached MJSPs of $2.44/kg and $2.50/kg jet fuel, respectively. According to the economic sensitivity analysis, the feedstock cost and fixed capital investment have the most influence on the MJSP.

Comparison of lignin extraction processes: Economic and environmental assessment.

This paper presents the technical-economic and environmental assessment of four lignin extraction processes from two different raw materials (sugarcane bagasse and rice husks). The processes are divided into two categories, the first processes evaluates lignin extraction with prior acid hydrolysis step, while in the second case the extraction processes are evaluated standalone for a total analysis of 16 scenarios. Profitability indicators as the net present value (NPV) and environmental indicators as the potential environmental impact (PEI) are used through a process engineering approach to understand and select the best lignin extraction process. The results show that both economically and environmentally process with sulfites and soda from rice husk presents the best results; however the quality of lignin obtained with sulfites is not suitable for high value-added products. Then, the soda is an interesting option for the extraction of lignin if high quality lignin is required for high value-added products at low costs.

Optimizing the enzyme loading and incubation time in enzymatic hydrolysis of lignocellulosic substrates.

A mathematical model for costing enzymatic hydrolysis of lignocellulosics is presented. This model is based on three variable parameters describing substrate characteristics and three unit costs for substrate, enzymes and incubation. The model is used to minimize the cost of fermentable sugars, as intermediate products on the route to ethanol or other biorefinery products, by calculating optimized values of enzyme loading and incubation time. This approach allows comparisons between substrates, with processing conditions optimized independently for each substrate. Steam-exploded pine wood was hydrolyzed in order to test the theoretical relationship between sugar yield and processing conditions.

Broad bean and pea by-products as sources of fibre-rich ingredients: potential antioxidant activity measured in vitro.

BACKGROUND: By-products generated during the processing of plant food can be considered a promising source of dietary fibre as a functional compound. The dietary fibre composition, soluble sugars and antioxidant activity of the extractable polyphenols of pea and broad bean by-products have been analysed in this study. RESULTS: Total dietary fibre using AOAC methods plus hydrolysis (broad bean pod: 337.3 g kg⁻¹; pea pod: 472.6 g kg⁻¹) is higher (P < 0.05) in both by-products than with the Englyst method (broad bean pod: 309.7 g kg⁻¹; pea pod: 434.6 g kg⁻¹). The main monomers are uronic acids, glucose, arabinose and galactose in broad bean pods. However, pea pods are very rich in glucose and xylose. The soluble sugars analysed by high-performance liquid chromatography in both by-products have glucose as the most important component, followed by sucrose and fructose. The ferric reducing antioxidant power (broad bean pod: 406.4 µmol Trolox equivalents g⁻¹; pea pod: 25.9 µmol Trolox equivalents g⁻¹) and scavenging effect on 2,2-diphenyl-1-picrylhydrazyl radical (EC50 of broad bean pod: 0.4 mg mL⁻¹; EC50 of pea pod: 16.0 mg mL⁻¹) were also measured. CONCLUSIONS: Broad bean and pea by-products are very rich in dietary fibre, particularly insoluble dietary fibre and their extractable polyphenols demonstrate antioxidant activity. Therefore they might be regarded as functional ingredients.

The challenge of enzyme cost in the production of lignocellulosic biofuels.

With the aim of understanding the contribution of enzymes to the cost of lignocellulosic biofuels, we constructed a techno-economic model for the production of fungal cellulases. We found that the cost of producing enzymes was much higher than that commonly assumed in the literature. For example, the cost contribution of enzymes to ethanol produced by the conversion of corn stover was found to be $0.68/gal if the sugars in the biomass could be converted at maximum theoretical yields, and $1.47/gal if the yields were based on saccharification and fermentation yields that have been previously reported in the scientific literature. We performed a sensitivity analysis to study the effect of feedstock prices and fermentation times on the cost contribution of enzymes to ethanol price. We conclude that a significant effort is still required to lower the contribution of enzymes to biofuel production costs.

Industrial wastes as low-cost potential adsorbents for the treatment of wastewater laden with heavy metals.

Industrial wastes, such as, fly ash, blast furnace slag and sludge, black liquor lignin, red mud, and waste slurry, etc. are currently being investigated as potential adsorbents for the removal of the heavy metals from wastewater. It was found that modified industrial wastes showed higher adsorption capacity. The application of low-cost adsorbents obtained from the industrial wastes as a replacement for costly conventional methods of removing heavy metal ions from wastewater has been reviewed. The adsorption mechanism, influencing factors, favorable conditions, and competitive ions etc. on the adsorption of heavy metals have also been discussed in this article. From the review, it is evident that certain industrial waste materials have demonstrated high removal capacities for the heavy metals laden with wastewater. However, it is to be mentioned that adsorption capacities of the adsorbents vary depending on the characteristics of the adsorbents, the extent of chemical modification and the concentration of adsorbates. There are also few issues and drawbacks on the utilization of industrial wastes as low-cost adsorbents that have been addressed. In order to find out the practical utilization of industrial waste as low-cost adsorbents on the commercial scale, more research should be conducted in this direction.

Removal and recovery of cobalt from aqueous solutions by adsorption using low cost lignocellulosic biomass--coir pith.

The applicability of low-cost lignocellulosic biosorbent-coir pith, for removal of cobalt (II) from aqueous solutions using batch adsorption studies has been explored herein. Adsorption characteristics of coir pith were investigated systematically by varying the experimental parameters such as, solution pH, initial metal ion concentration, contact time, adsorbent dose and temperature. The studies revealed that optimum adsorption of cobalt onto coir pith occurred in the pH range of 4.0 - 7.0. Sorption kinetics of cobalt was found to be quite rapid under ambient conditions and the process followed second-order kinetics. The experimental data have been analyzed using non-linearized forms of Langmuir, Freundlich and Redlich-Peterson adsorption isotherms for mathematical description of the process. Desorption studies showed that the quantitative recovery of Co (II) from the spent coir pith was achieved by using 0.5 N HCl. The suitability of this adsorbent for real situation has been observed, when complete removal of cobalt from nuclear power plant coolant water was obtained. The present studies successfully demonstrated the use of coir pith as an efficient adsorbent material for removal of cobalt from aqueous solutions.

Reviving the carbohydrate economy via multi-product lignocellulose biorefineries.

Before the industrial revolution, the global economy was largely based on living carbon from plants. Now the economy is mainly dependent on fossil fuels (dead carbon). Biomass is the only sustainable bioresource that can provide sufficient transportation fuels and renewable materials at the same time. Cellulosic ethanol production from less costly and most abundant lignocellulose is confronted with three main obstacles: (1) high processing costs (dollars /gallon of ethanol), (2) huge capital investment (dollars approximately 4-10/gallon of annual ethanol production capacity), and (3) a narrow margin between feedstock and product prices. Both lignocellulose fractionation technology and effective co-utilization of acetic acid, lignin and hemicellulose will be vital to the realization of profitable lignocellulose biorefineries, since co-product revenues would increase the margin up to 6.2-fold, where all purified lignocellulose co-components have higher selling prices (> approximately 1.0/kg) than ethanol ( approximately 0.5/kg of ethanol). Isolation of large amounts of lignocellulose components through lignocellulose fractionation would stimulate R&D in lignin and hemicellulose applications, as well as promote new markets for lignin- and hemicellulose-derivative products. Lignocellulose resource would be sufficient to replace significant fractionations (e.g., 30%) of transportation fuels through liquid biofuels, internal combustion engines in the short term, and would provide 100% transportation fuels by sugar-hydrogen-fuel cell systems in the long term.

Process engineering economics of bioethanol production.

This work presents a review of studies on the process economics of ethanol production from lignocellulosic materials published since 1996. Our objective was to identify the most costly process steps and the impact of various parameters on the final production cost, e.g. plant capacity, raw material cost, and overall product yield, as well as process configuration. The variation in estimated ethanol production cost is considerable, ranging from about 0.13 to 0.81 US$ per liter ethanol. This can be explained to a large extent by actual process differences and variations in the assumptions underlying the techno-economic evaluations. The most important parameters for the economic outcome are the feedstock cost, which varied between 30 and 90 US$ per metric ton in the papers studied, and the plant capacity, which influences the capital cost. To reduce the ethanol production cost it is necessary to reach high ethanol yields, as well as a high ethanol concentration during fermentation, to be able to decrease the energy required for distillation and other downstream process steps. Improved pretreatment methods, enhanced enzymatic hydrolysis with cheaper and more effective enzymes, as well as improved fermentation systems present major research challenges if we are to make lignocellulose-based ethanol production competitive with sugar- and starch-based ethanol. Process integration, either internally or externally with other types of plants, e.g. heat and power plants, also offers a way of reducing the final ethanol production cost.

The lignol approach to biorefining of woody biomass to produce ethanol and chemicals.

Processes that produce only ethanol from lignocellulosics display poor economics. This is generally overcome by constructing large facilities having satisfactory economies of scale, thus making financing onerous and hindering the development of suitable technologies. Lignol Innovations has developed a biorefining technology that employs an ethanol-based organosolv step to separate lignin, hemicellulose components, and extractives from the cellulosic fraction of woody biomass. The resultant cellulosic fraction is highly susceptible to enzymatic hydrolysis, generating very high yields of glucose (>90% in 12-24 h) with typical enzyme loadings of 10-20 FPU (filter paper units)/g. This glucose is readily converted to ethanol, or possibly other sugar platform chemicals, either by sequential or simultaneous saccharification and fermentation. The liquor from the organosolv step is processed by well-established unit operations to recover lignin, furfural, xylose, acetic acid, and a lipophylic extractives fraction. The process ethanol is recovered and recycled back to the process. The resulting recycled process water is of a very high quality, low BOD5, and suitable for overall system process closure. Significant benefits can be attained in greenhouse gas (GHG) emission reductions, as per the Kyoto Protocol. Revenues from the multiple products, particularly the lignin, ethanol and xylose fractions, ensure excellent economics for the process even in plants as small as 100 mtpd (metric tonnes per day) dry woody biomass input a scale suitable for processing wood residues produced by a single large sawmill.

Use of analytical microscopy to analyze the speciation of copper and chromium ions onto a low-cost biomaterial.

In this paper, we present our study of the speciation of copper and hexavalent chromium sorbed onto a lignocellulosic substrate, using analytical microscopy. The lignocellulosic substrate constitutes a low-cost biomaterial that can be used in wastewater treatment. Transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDXS) was used to determine the speciation of the two metal ions on the constitutive moieties of the lignocellulosic substrate. The use of a staining agent sensitive to carbon unsaturation allowed us to differentiate between the microstructures rich in lignin entities and those rich in cellulose entities. The EDX analysis showed that metal ions are preferentially sorbed onto microstructures rich in lignin moieties. The energy electron loss spectroscopy (EELS) was used to determine the oxidation states of chromium in association with lignocellulosic moieties. We showed that the sorption process of hexavalent chromium requires the reduction of Cr(VI) into Cr(III) and the probable oxidation of lignin moieties.

Potential synergies and challenges in refining cellulosic biomass to fuels, chemicals, and power.

Lignocellulosic biomass such as agricultural and forestry residues and dedicated crops provides a low-cost and uniquely sustainable resource for production of many organic fuels and chemicals that can reduce greenhouse gas emissions, enhance energy security, improve the economy, dispose of problematic solid wastes, and improve air quality. A technoeconomic analysis of biologically processing lignocellulosics to ethanol is adapted to project the cost of making sugar intermediates for producing a range of such products, and sugar costs are predicted to drop with plant size as a result of economies of scale that outweigh increased biomass transport costs for facilities processing less than about 10,000 dry tons per day. Criteria are then reviewed for identifying promising chemicals in addition to fuel ethanol to make from these low cost cellulosic sugars. It is found that the large market for ethanol makes it possible to achieve economies of scale that reduce sugar costs, and coproducing chemicals promises greater profit margins or lower production costs for a given return on investment. Additionally, power can be sold at low prices without a significant impact on the selling price of sugars. However, manufacture of multiple products introduces additional technical, marketing, risk, scale-up, and other challenges that must be considered in refining of lignocellulosics.