Cost Of Biofuel Production Research Articles

Diversifying bio-petro fuel sources for future energy sustainability and its challenges

Petroleum has been important in the energy industry since 19th century when the refining of paraffin from crude oil began. The industry recently appears to be in a downtown and fragile moment despite the price of oil is slowly rising. Renewable alternatives such as biofuels have gained increasing traction while petroleum fuel seemingly concedes to bio-fuels due to the rising public concern on the environment and stricter emission regulations. To be a strategic fuel in the energy security matrix, both fossil and bio-fuels options should be considered. However, the use of bio-fuels to achieve a degree of carbon neutrality is not without challenges. Among the challenges are land development and socio-political issue, carbon neutrality due to ILUC, high 2G bio-fuel feedstock and production cost, competing technology from electric vehicles and the impending fourth industrial revolution, NOx emissions and variation in biodiesel quality. This paper briefly reviews the potential of fuels source diversification and the challenges and how they can raise up to the challenges in order to be sustainable and attractive. In order to achieve this objective, first carbon credit through carbon trading needs to continue to stabilize the energy price. Second, 1G bio-fuel needs to forgo the use of natural, peat forest, rubber estate since these are an effective carbon sink and oxygen source. Third, advanced bio-fuels with high yield, process economics and sustainability need to be innovated. Fourth, the quality and standard bio-fuel that reduces NOx emission need to be improved. Finally and most importantly, carbon capture technology needs to be deployed immediately in fossil fuel power plants.

Challenges of Downstream Processing for the Production of Biodiesel from Microalgae

The continuous reliance on fossil fuels is unsustainable, due to the depletion of global reserves and the greenhouse gas emissions associated with their use. Therefore, there are vigorous research initiatives intended to develop renewable alternatives. Microalgae are a promising alternative for biodiesel production and have received increasing attention during the last few decades. However, is not yet sufficiently cost-effective to compete with petroleum-based conventional fuels. This happens essentially because of downstream processing – harvesting microalgae biomass and extraction of lipids are two of the most expensive processes from the overall process. Harvesting, drying, cell disruption, oil extraction and transesterification (into biodiesel) are highlighted processes in this review article. The techniques associated with each process present advantages and handicaps that are here discussed. Improvements that will directly affect the final production costs of microalgal biomass-based biofuels are also proposed.

Effects of Coproduct Uses on Environmental and Economic Sustainability of Hydrocarbon Biofuel from One- and Two-Step Pyrolysis of Poplar

This study investigated the environmental and economic sustainability of liquid hydrocarbon biofuel production via fast pyrolysis of poplar biomass through two pathways: a one-step pathway that converted poplar via fast pyrolysis only, and a two-step pathway that includes a torrefaction step prior to fast pyrolysis. Optimization of these fast pyrolysis-based biofuel processes were investigated through heat integration and alternative uses of the coproduct biochar, which can be sold as an energy source to displace coal, soil amendment or processed into activated carbon. The impacts of optimization on the cost of hydrocarbon biofuel production as well as the environmental impacts were investigated through a technoeconomic analysis (TEA) and life cycle assessment (LCA), respectively, with two-step and one-step processing compared to fossil fuels. The TEA indicates that a one-step heat integrated pathway with the production of activated carbon has a minimum selling price of $3.23/gallon compared to $5.16/gallon for a two-step heat integrated process with burning of the coproduct biochar to displace coal. The LCA indicates that using the displacement analysis approach, a two-step heat integrated pathway had a global warming potential of −102 g CO2 equivalent/MJ biofuel compared to 16 CO2 equivalent/MJ biofuel for the heat integrated one-step pathway.

Impact of carbon emissions in a sustainable supply chain management for a second generation biofuel

Abstract Global warming due to excessive use of fossil fuels has driven researchers to focus on sustainable energy sources for the future. For clean production systems, biofuel is expanding the domain of renewable and sustainable energy supplies. An efficient and sustainable supply chain plays a pivotal role in ensuring this supply. In this research, crop residuals in different agricultural zones, transportation for shipment of residual biomass as well as biofuel, multiple biorefineries, and multiple market centers are considered. The expense of the resources, the yield of residual biomass in agricultural zones, and the demand of market centers are represented by fuzzy numbers as they are assumed to be uncertain. The carbon emissions cost at all stages of the supply chain was also incorporated into this model. This objective of this study is to develop a supply chain model that minimizes the total cost of a second generation biofuel supply chain and location-allocation for agricultural zones and biorefineries to meet the uncertain demand for market centers. Two numerical examples are analyzed, and the results proves that the cost of biofuel production in biorefineries contributed 52.16%, which is a major proportion of the total cost. In the entire supply chain, the transportation sector is the foremost source of carbon emissions in an environment with 88.50% of the total carbon emissions. The results confirms that the proposed model is viable for designing second generation biofuel supply chains under uncertainty. Significant managerial insights of this research are also described to better express the efficiency of the model.

MEASURING THE ECONOMIC AND ENVIRONMENTAL REVENUES TO ENLARGE IN THE PRODUCTION OF NON EDIBLE VEGETABLE OILS TO PRODUCE BIO-FUELS IN EGYPT

The study aimed at measuring the economic and environmental revenue for the expansion of the production of non-edible vegetable oils for the purpose of producing biofuels. Research and studies are in Egypt to produce bio-fuel as an alternative to diesel and gasoline but have not yet been produced for commercial purposes. Energy is a key element for economic development, however, the traditional form of energy is fossil fuel energy. There are several reasons to search for alternative sources of traditional energy: (Economic objective); concern about climate change (environmental goal); low cost of renewable energies (economic target), and support for agricultural producers (agricultural and economic objective). As a result of many reasons, the most important of which is the expected oil depletion by the end of the 21st century, the rise in oil prices and the negative effects of toxic emissions from fossil fuels on the environment and climate. Therefore, it was necessary to search for alternative renewable sources such as solar, wind and bioenergy. The production of biofuels is related to the agricultural sector. In order to benefit from the enormous potential that it enjoys in terms of abundance of untapped desert lands and desolate land and water resources for the production of biofuel as a source of renewable energy has been studying the energy crops suitable for the production of biofuel Three plants were selected to be suitable for agriculture in the Egyptian environment and suitable for agriculture in desert and desert lands and sewage water. This is because there is no conflict between food and energy. The environmental impact of energy crops and the effect of biofuel production on energy crops on both land use change, On water, on agricultural soils, on biological diversity, study of the economic impact and production costs of biofuels (biogasoline and biodiesel) in the two ways of cracking and the method of extraction from the cost of growing energy crops until the stage of obtaining biogasoline and biodiesel. The study reached several results: Biofuel production is not a priority for the government and the government must establish a sound legislative framework and strict procedures to support its production in a sustainable manner. Egypt has abundant sources of bio-fuel production represented in land, water, labor and qualified cadres. Lack of accurate data on the assessment of the agricultural, environmental, social and economic impacts of bio-fuels produced from both Jojoba, Jatropha and Al-Kharoua. There are no success stories on the production of bio-fuels from the non edible vegetable oils of Jojoba, Jatropha and castor plants. Therefore, the government should interact with stakeholders and companies to disseminate the right information to make good decisions.

Processivity and enzymatic mechanism of a multifunctional family 5 endoglucanase from Bacillus subtilis BS-5 with potential applications in the saccharification of cellulosic substrates

BackgroundPresently, enzymes still constitute a major part of the cost of biofuel production from lignocellulosic biomass. Processive endoglucanases, which possess both endoglucanase and exoglucanase activity, have the potential to reduce the costs of biomass saccharification when used together with commercial cellulases. Therefore, the exploration of new processive endoglucanases has attracted much attention with a view to accelerating the industrialization of biofuels and biochemicals.ResultsThe endoglucanase EG5C and its truncated form EG5C-1 from Bacillus subtilis BS-5 were expressed and characterized. EG5C was a typical endoglucanase, comprised of a family 5 catalytic domain and family 3 carbohydrate-binding domain, and which had high activity toward soluble cellulosic substrates, but low activity toward insoluble cellulosic substrates. Importantly, the truncated form EG5C-1 was a processive endoglucanase that hydrolyzed not only carboxymethyl cellulose (CMC), but also insoluble cellulosic substrates. The hydrolytic activities of EG5C-1 towards CMC, phosphoric acid-swollen cellulose (PASC), p-nitrophenyl-β-d-cellobioside, filter paper and Avicel are 4170, 700, 2550, 405 and 320 U/μmol, respectively. These data demonstrated that EG5C-1 had higher activity ratio of exoglucanase to endoglucanase than other known processive endoglucanases. When PASC was degraded by EG5C-1, the ratio of soluble to insoluble reducing sugars was about 3.7 after 3 h of incubation with cellobiose and cellotriose as the main products. Importantly, EG5C-1 alone was able to hydrolyze filter paper and PASC. At 5% substrate concentration and 10 FPU/g PASC enzyme loading, the saccharification yield was 76.5% after 60 h of incubation. Replacement of a phenylalanine residue (F238) by an alanine at the entrance/exit of the substrate binding cleft significantly reduces the ability of EG5C-1 to degrade filter paper and Avicel, but this mutation has little impact on CMCase activity. The processivity of this mutant was also greatly reduced while its cellulose binding ability was markedly enhanced.ConclusionsThe processive endoglucanase EG5C-1 from B. subtilis BS-5 exhibits excellent properties that render it a suitable candidate for use in biofuel and biochemical production from lignocellulosic biomass. In addition, our studies also provide useful information for research on enzyme processivity at the molecular level.

Design of biorefinery systems for conversion of corn stover into biofuels using a biorefinery engineering framework

Unlocking the potential and value of lignocellulosic residues is an important step in making biorefineries economically and environmentally promising. This calls for a holistic and systematic approach in designing sustainable industrial systems. In this work, biorefinery systems via biochemical route (acetone–butanol–ethanol or ABE system) and thermochemical route (gasification and mixed alcohols or GMA system) for converting corn stover into biofuels have been designed using a Sustainable Engineering Framework. The framework involves eight main steps: (1) design problem definition, (2) data collection, (3) process synthesis and simulation, (4) process integration, (5) resource recovery from residues, (6) utility system design, (7) economic and environmental modelling and (8) economic value and environmental impact margin analysis for decision making. Consideration of resource recovery from biorefinery waste streams has proven to be the key in making biorefineries self-sustaining and with low environmental impacts. Simultaneous economic and environmental feasibility assessment at the early stage of process design is highly envisaged. The cost of biofuel production in the ABE system has been found to be 49.2 US$/GJ and 69.9 US$/GJ in the GMA system. The greenhouse gas emissions are 46.2 g CO2-eq/GJ for ABE and 19.0 g CO2-eq/GJ for GMA, lower than gasoline (85 g CO2-eq/GJ). The GMA system is not economically compelling though with high environmental benefit, while the ABE system has shown to be both economically and environmentally feasible.

Ammonium, nitrate, and urea play different roles for lipid accumulation in the nervonic acid—producing microalgae Mychonastes afer HSO-3-1

Producing valuable coproducts from oleaginous microalgae is an option to reduce the total cost of biofuel production. Here, the influence of nitrogen sources on biomass yield and lipid accumulation of a newly identified oleaginous green microalgal strain, Mychonastes afer HSO-3-1, was evaluated. Carbon assimilation and the following lipid biosynthesis of M. afer were inhibited to some extent under weak acidic conditions (6 < pH < 7) and any of the tested nitrogen source. The highest lipid productivity of 50.7 mg L−1 day−1 was achieved with a 17.6 mM nitrogen supplement in the form of urea. The cell polar lipid content was significantly higher than triacylglycerol (TAG), and saturated palmitic acid (C16:0) occupied a dominant position in the fatty acid profiles while culturing M. afer in acidic medium with NH4 + as the nitrogen source. Under neutral conditions, the lipid productivities of M. afer cultivated in media containing 17.6 mM of NaNO3, NH4Cl, and NH4NO3 were 76.2, 77.5, and 79.0 mg L−1 day−1, respectively. The greatest TAG content (58.56%) of total lipids was obtained when NaNO3 was used as the nitrogen source. There was no significant difference in the fatty acid composition of M. afer cells when they were cultivated in neutral media supplemented with NaNO3, urea, NH4Cl, and NH4NO3. Therefore, NH4 + was not a suitable nitrogen source for M. afer cultivation due to the additional labor, working procedures, and alkali required to adjust the medium pH. Considering that using urea as nitrogen source could reduce the cost of nutrient salts substantially and urea can be taken up and utilized by most microalgae, it is a preferred nitrogen source. The major properties of biodiesel derived from M. afer HSO-3-1 met biodiesel quality, and nervonic acid concentrations remained at approximately 3.0% of total fatty acids.

The TcEG1 beetle (Tribolium castaneum) cellulase produced in transgenic switchgrass is active at alkaline pH and auto-hydrolyzes biomass for increased cellobiose release

BackgroundGenetically engineered biofuel crops, such as switchgrass (Panicum virgatum L.), that produce their own cell wall-digesting cellulase enzymes would reduce costs of cellulosic biofuel production. To date, non-bioenergy plant models have been used in nearly all studies assessing the synthesis and activity of plant-produced fungal and bacterial cellulases. One potential source for cellulolytic enzyme genes is herbivorous insects adapted to digest plant cell walls. Here we examine the potential of transgenic switchgrass-produced TcEG1 cellulase from Tribolium castaneum (red flour beetle). This enzyme, when overproduced in Escherichia coli and Saccharomyces cerevisiae, efficiently digests cellulose at optima of 50 °C and pH 12.0.ResultsTcEG1 that was produced in green transgenic switchgrass tissue had a range of endoglucanase activity of 0.16–0.05 units (µM glucose release/min/mg) at 50 °C and pH 12.0. TcEG1 activity from air-dried leaves was unchanged from that from green tissue, but when tissue was dried in a desiccant oven (46 °C), specific enzyme activity decreased by 60%. When transgenic biomass was “dropped-in” into an alkaline buffer (pH 12.0) and allowed to incubate at 50 °C, cellobiose release was increased up to 77% over non-transgenic biomass. Saccharification was increased in one transgenic event by 28%, which had a concurrent decrease in lignin content of 9%. Histological analysis revealed an increase in cell wall thickness with no change to cell area or perimeter. Transgenic plants produced more, albeit narrower, tillers with equivalent dry biomass as the control.ConclusionsThis work describes the first study in which an insect cellulase has been produced in transgenic plants; in this case, the dedicated bioenergy crop switchgrass. Switchgrass overexpressing the TcEG1 gene appeared to be morphologically similar to its non-transgenic control and produced equivalent dry biomass. Therefore, we propose TcEG1 transgenics could be bred with other transgenic germplasm (e.g., low-lignin lines) to yield new switchgrass with synergistically reduced recalcitrance to biofuel production. In addition, transgenes for other cell wall degrading enzymes may be stacked with TcEG1 in switchgrass to yield complementary cell wall digestion features and complete auto-hydrolysis.

Production of the versatile cellulase for cellulose bioconversion and cellulase inducer synthesis by genetic improvement of Trichoderma reesei

BackgroundThe enzymes for efficient hydrolysis of lignocellulosic biomass are a major factor in the development of an economically feasible cellulose bioconversion process. Up to now, low hydrolysis efficiency and high production cost of cellulases remain the significant hurdles in this process. The aim of the present study was to develop a versatile cellulase system with the enhanced hydrolytic efficiency and the ability to synthesize powerful inducers by genetically engineering Trichoderma reesei.ResultsIn our study, we employed a systematic genetic strategy to construct the carbon catabolite-derepressed strain T. reesei SCB18 to produce the cellulase complex that exhibited a strong cellulolytic capacity for biomass saccharification and an extraordinary high β-glucosidase (BGL) activity for cellulase-inducing disaccharides synthesis. We first identified the hypercellulolytic and uracil auxotrophic strain T. reesei SP4 as carbon catabolite repressed, and then deleted the carbon catabolite repressor gene cre1 in the genome. We found that the deletion of cre1 with the selectable marker pyrG led to a 72.6% increase in total cellulase activity, but a slight reduction in saccharification efficiency. To facilitate the following genetic modification, the marker pyrG was successfully removed by homologous recombination based on resistance to 5-FOA. Furthermore, the Aspergillus niger BGLA-encoding gene bglA was overexpressed, and the generated strain T. reesei SCB18 exhibited a 29.8% increase in total cellulase activity and a 51.3-fold enhancement in BGL activity (up to 103.9 IU/mL). We observed that the cellulase system of SCB18 showed significantly higher saccharification efficiency toward differently pretreated corncob residues than the control strains SDC11 and SP4. Moreover, the crude enzyme preparation from SCB18 with high BGL activity possessed strong transglycosylation ability to synthesize β-disaccharides from glucose. The transglycosylation product was finally utilized as the inducer for cellulase production, which provided a 63.0% increase in total cellulase activity compared to the frequently used soluble inducer, lactose.ConclusionsIn summary, we constructed a versatile cellulase system in T. reesei for efficient biomass saccharification and powerful cellulase inducer synthesis by combinational genetic manipulation of three distinct types of genes to achieve the customized cellulase production, thus providing a viable strategy for further strain improvement to reduce the cost of biomass-based biofuel production.

Effect of land use change for bioenergy production on feedstock cost and water quality

Producing renewable fuel from dedicated energy crops, such as switchgrass, has the potential to generate localized environmental benefits. This study uses high-resolution spatial data for west Tennessee to quantify the effects of producing switchgrass for cellulosic ethanol on the grey water footprint (GWF), or the amount of freshwater needed to dilute nitrate leachate to a safe level, relative to existing agricultural production. In addition, the estimated cost and GWF are incorporated in a mixed-integer multi-objective optimization model to derive the efficient frontier of the feedstock supply chain and determine a switchgrass supply chain that achieves the greatest reduction in GWF at the lowest cost. Results suggest that background nitrate concentration in ambient water and the types of agricultural land converted to switchgrass production influence the extent of the GWF. The average GWF of switchgrass in the study area ranges between 131.8LL−1 and 145.9LL−1 of ethanol, which falls into the range of estimated GWF of other lignocellulosic biomass feedstock in the literature. Also, the average cost of reducing GWF from the feedstock supply chain identified by the compromise solution method is $0.94m−3 in the region. A tradeoff between biofuel production costs and reduced nitrate loading in groundwater is driven by differences in the agricultural land converted to feedstock production. Our findings illustrate the energy-water-food nexus in the development of a local bioenergy sector and provide a management strategy associated with land use choices for the supply of energy crops. However, the water quality improvements associated with displacing crop with feedstock production in one region could be offset by expanded or more intensive agricultural production in other regions.

Toward a sustainable bioeconomy in West Africa: A focus on biorefining

AbstractConsidering its size and expanding population, Africa needs to play a more active role in preventing global warming. The economy of most West African countries is driven by agriculture and the export of processed wood resulting in the generation of tons of wood and agricultural waste. The waste is usually disposed of by burning, which releases harmful greenhouse gases (GHGs) into the environment. Wood and agricultural wastes are valuable biomass feedstocks for second‐generation biofuels and chemicals. The availability of diverse feedstocks makes the West African sub‐region suitable for setting up biorefineries. However, the limiting factors for establishing biorefineries such as appropriate technology, infrastructure and forward‐looking policies have to be addressed. The currently high cost of biofuel production and competitive crude oil prices also make it seem unfeasible for West African countries and other developing economies to invest in this industry. Therefore, we present an idea for developing a multipurpose modular biorefinery model to meet the energy needs of the region with an added advantage of creating new markets and jobs. We also discuss what new energy policies should be focused on in order to fast‐track the development of the bioenergy sector. © 2017 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Engineering biorefinery residues from loblolly pine for supercapacitor applications

Recycling agricultural waste biomass into high-value-added products is of great importance to offset the cost of biofuel production. Here, we make biochar-based activated carbons (BACs) from loblolly pine chips via different carbonization recipes and chemical activations. BACs were then assembled into electrochemical double-layer capacitors (EDLCs) as electrode materials. Surprisingly, pyrolysis at lower temperatures (300 °C and 350 °C) rendered better electrochemical performance of BACs than those done at higher temperatures (500 °C and 700 °C). This is mainly due to the large surface area and high pore volume generated at the lower temperatures. Among all the pyrolysis recipes, flash pyrolysis at 300 °C produced the BAC with the highest specific capacitance (74 F g−1 at 20 mV s−1), exceeding the specific capacitance of commercial activated carbon (NORIT®) by 45%. This report demonstrates the great potential of our refinery recipe to engineer BACs from the sustainable, affordable, and abundant natural wastes for energy-storage applications, which opens the door for a group of biorefinery residues for value-added applications.

Cost optimization of biofuel production – The impact of scale, integration, transport and supply chain configurations

This study uses a geographically-explicit cost optimization model to analyze the impact of and interrelation between four cost reduction strategies for biofuel production: economies of scale, intermodal transport, integration with existing industries, and distributed supply chain configurations (i.e. supply chains with an intermediate pre-treatment step to reduce biomass transport cost). The model assessed biofuel production levels ranging from 1 to 150PJa−1 in the context of the existing Swedish forest industry. Biofuel was produced from forestry biomass using hydrothermal liquefaction and hydroprocessing. Simultaneous implementation of all cost reduction strategies yielded minimum biofuel production costs of 18.1–18.2 € GJ−1 at biofuel production levels between 10 and 75PJa−1. Limiting the economies of scale was shown to cause the largest cost increase (+0–12%, increasing with biofuel production level), followed by disabling integration benefits (+1–10%, decreasing with biofuel production level) and allowing unimodal truck transport only (+0–6%, increasing with biofuel production level). Distributed supply chain configurations were introduced once biomass supply became increasingly dispersed, but did not provide a significant cost benefit (<1%). Disabling the benefits of integration favors large-scale centralized production, while intermodal transport networks positively affect the benefits of economies of scale. As biofuel production costs still exceeds the price of fossil transport fuels in Sweden after implementation of all cost reduction strategies, policy support and stimulation of further technological learning remains essential to achieve cost parity with fossil fuels for this feedstock/technology combination in this spatiotemporal context.

Cross-study analysis of factors affecting algae cultivation in recycled medium for biofuel production

Current high costs of commercial-scale algal biofuel production prevent the widespread use of this renewable fuel source. One cost-saving approach is the reuse of algae cultivation water after biomass harvesting, which reduces water pumping and treatment costs. However, dissolved compounds, cell debris, and microorganisms remaining in the water could affect subsequent algae generations. Previous studies demonstrate a variety of effects of recycled medium on algae growth, yet their results have not been collectively analyzed. Here we integrate data across 86 studies to determine the relative importance of different factors influencing algae growth in recycled medium. We found that algae taxa can have the greatest influence, while the harvesting method is less influential on growth outcomes. This meta-analysis identifies favorable taxa and thus provides a tool for algae cultivation decision-making when medium reuse is an important driver. Results can also aid in estimating relative algae yield and growth rates for technoeconomic assessments that incorporate water recycling.

Managing variability in algal biomass production through drying and stabilization of feedstock blends

The uncertainty and variability of algal biomass production presents several challenges to the nascent algal biofuel industry, including equipment scaling and feedstock supply. Ideally, on-site processing equipment will be scaled to minimize overall biofuel production costs, which means at times biomass production could exceed down-stream processing capacity due to seasonal variation. Biomass produced in excess of conversion capacity during summer months must be stabilized by some method, such as drying, until needed later in the year. Because of algae's high moisture content and its cohesive nature, drying is challenging. Blending algae with terrestrial biomass may provide a cost-effective method to enable drying and stabilization of algae by reducing moisture content and improving rheological (i.e. flowability) properties. To test the technical feasibility of this approach, bench-scale rotary drum dyers were constructed and tested with blends of algae (Scenedesmus sp.), ground pine (2mm grind), sorghum, corn stover (6mm), sieved sand, and dried algae. In these studies, blends up to 40% algae exhibited drying behavior similar to that of pine alone, and reached dryness (2% moisture) in half of the time it took to dry algae alone. Thermogravimetric analyses performed on blends and neat blend materials provided drying curves consistent with the bench-scale dryers. Preliminary logistics analysis for production-scale operations were performed to determine cost and availability of feedstock materials for blending as compared to drying algae directly. This analysis indicates that revenue lost due to idle processing capacity had a significant impact on the per gallon gasoline equivalent feedstock cost. The blending approach, described herein, reduced feedstock-related costs, including procurement, drying, and storage by 35% relative to drying algae directly. Our results indicate that blending algae with terrestrial biomass enables the use of rotary dryers and has the potential to improve overall algal biofuel economics.

Ternary ionic liquid\u2013water pretreatment systems of an agave bagasse and municipal solid waste blend

BackgroundPretreatment is necessary to reduce biomass recalcitrance and enhance the efficiency of enzymatic saccharification for biofuel production. Ionic liquid (IL) pretreatment has gained a significant interest as a pretreatment process that can reduce cellulose crystallinity and remove lignin, key factors that govern enzyme accessibility. There are several challenges that need to be addressed for IL pretreatment to become viable for commercialization, including IL cost and recyclability. In addition, it is unclear whether ILs can maintain process performance when utilizing low-cost, low-quality biomass feedstocks such as the paper fraction of municipal solid waste (MSW), which are readily available in high quantities. One approach to potentially reduce IL cost is to use a blend of ILs at different concentrations in aqueous mixtures. Herein, we describe 14 IL-water systems with mixtures of 1-ethyl-3-ethylimidazolium acetate ([C2C1Im][OAc]), 1-butyl-3-ethylimidazolium acetate ([C4C1Im][OAc]), and water that were used to pretreat MSW blended with agave bagasse (AGB). The detailed analysis of IL recycling in terms of sugar yields of pretreated biomass and IL stability was examined.ResultsBoth biomass types (AGB and MSW) were efficiently disrupted by IL pretreatment. The pretreatment efficiency of [C2C1Im][OAc] and [C4C1Im][OAc] decreased when mixed with water above 40%. The AGB/MSW (1:1) blend demonstrated a glucan conversion of 94.1 and 83.0% using IL systems with ~10 and ~40% water content, respectively. Chemical structures of fresh ILs and recycle ILs presented strong similarities observed by FTIR and 1H-NMR spectroscopy. The glucan and xylan hydrolysis yields obtained from recycled IL exhibited a slight decrease in pretreatment efficiency (less than 10% in terms of hydrolysis yields compared to that of fresh IL), and a decrease in cellulose crystallinity was observed.ConclusionsOur results demonstrated that mixing ILs such as [C2C1Im][OAc] and [C4C1Im][OAc] and blending the paper fraction of MSW with agricultural residues, such as AGB, may contribute to lower the production costs while maintaining high sugar yields. Recycled IL-water mixtures provided comparable results to that of fresh ILs. Both of these results offer the potential of reducing the production costs of sugars and biofuels at biorefineries as compared to more conventional IL conversion technologies.Graphical abstractSchematic of ionic liquid (IL) pretreatment of agave bagasse (AB) and paper-rich fraction of municipal solid waste (MSW)

Carbon capture and storage across fuels and sectors in energy system transformation pathways

Carbon capture and storage (CCS) is broadly understood to be a key mitigation technology, yet modeling analyses provide different results regarding the applications in which it might be used most effectively. Here we use the Global Change Assessment Model (GCAM) to explore the sensitivity of CCS deployment across sectors and fuels to future technology cost assumptions. We find that CCS is deployed preferentially in electricity generation or in liquid fuels production, depending on CCS and biofuels production cost assumptions. We consistently find significant deployment across both sectors in all of the scenarios considered here, with bioenergy with CCS (BECCS) often the dominant application. As such, this study challenges the view that CCS will primarily be coupled with power plants and used mainly in conjunction with fossil fuels, and suggests greater focus on practical implications of significant CCS and BECCS deployment to inform energy system transformation scenarios over the 21st century.

Impact of drying-grinding sequence on loblolly pine chips preprocessing effectiveness

The high amount of energy consumed during the processing of biomass inflates the production cost of bio-fuels and bio-products. This study was therefore carried out to evaluate the influence of drying and grinding sequence on biomass energy consumption and properties (specific grinding energy requirement, specific drying energy requirement, particle size distribution, bulk density, tap density, aspect ratio, and flow index of grinds). Among the six drying-grinding sequences (12-S, 30-S, 50-S, 30-L-12-S, 50-L-12-S, and 50-L-30-S), sequence 50–S had the lowest geometric mean diameter and sequence 30–S had the highest geometric mean diameter. Drying-grinding sequence significantly affected the bulk density and tap density of grinds. The bulk density of grinds varied from 267.1kg/m3 (sequence 12-S) to 98.0kg/m3 (sequence 50-S) while the tap density ranged from 342.6kg/m3 (sequence 12-S) to 153.7kg/m3 (sequence 50-S). This variation in the densities followed the changes the particle morphology and aspect ratio distribution. A trade-off was noted between specific grinding energy requirement and specific drying energy requirement. The grinding of samples at higher moisture content consumed higher grinding energy than the grinding of samples at lower moisture content. Moisture loss during grinding however increased as the moisture content of woodchips increased, hence resulted in lower drying energy requirements. The least specific drying energy consumption was (1581kJ/kg d.b.) for sequence 50-S and the highest specific drying energy consumption was (3933kJ/kg d.b.) for sequence 12-S.

Supply and demand of biofuels in the fuel market of Thailand: Two stage least square and three least square approaches

In recent years, Thailand Government has made ambitious targets for biofuels and the demand for biofuels has increased. This study estimates the long-term factors that affect the supply and demand for biofuels (bioethanol and biodiesel) in Thailand by developing a theoretical model based on simultaneous equations, using Two stage least square and Three stage least square approaches. Quarterly data were collected for the years 2007–2013:2. Amongst many factors, we found three major factors affecting the long-term demand for biofuels: the price of biofuels, the real gross domestic product and the number of vehicles. On the other hand, the long-run supply of biodiesel and bioethanol was influenced by the gross domestic product, the cost of substitution using biofuel (i.e., price of gasoline 95 compared to blended gasoline) and the price of biodiesel. These findings have important policy implications to the government plans for biofuel development, suggesting that maintaining the price difference between gasoline and gasohol (blended gasoline) and a greater penetration of biofuel vehicles in fleet would be important policies for biofuel consumption. On biofuel supply side, results indicate that policies to compensate the biofuel producers for prices and reducing cost of bio-fuel production are important.