Biofuel Processing Research Articles

Superhydrophobic and superhydrophilic surface-enhanced separation performance of porous inorganic membranes for biomass-to-biofuel conversion applications

ABSTRACTA new class of porous membranes is introduced to provide unique separation mechanisms by surface interactions and capillary condensation. High-performance architectural surface selective (HiPAS) membranes were designed for high perm-selective flux and high-temperature tolerance for hot vapor processing and liquid processing. Due to surface-enhanced selectivity, larger-fluxes were achieved by utilizing larger pore sizes (~8 nm for vapor phase and micron-sized pores for liquid phase separations). This article describes a membrane-based separation concept for biomass conversion pathways and demonstrates the initial data for selective permeation of toluene–water and toluene–phenol–water relevant to biofuel processing.

Application of Electroporation Technique in Biofuel Processing

Biofuels production is mostly oriented with fermentation process, which requires fermentable sugar as nutrient for microbial growth. Lignocellulosic biomass (LCB) represents the most attractive, low-cost feedstock for biofuel production, it is now arousing great interest. The cellulose that is embedded in the lignin matrix has an insoluble, highly-crystalline structure, so it is difficult to hydrolyze into fermentable sugar or cell protein. On the other hand, microbial lipid has been studying as substitute of plant oils or animal fat to produce biodiesel. It is still a great challenge to extract maximum lipid from microbial cells (yeast, fungi, algae) investing minimum energy. Electroporation (EP) of LCB results a significant increase in cell conductivity and permeability caused due to the application of an external electric field. EP is required to alter the size and structure of the biomass, to reduce the cellulose crystallinity, and increase their porosity as well as chemical composition, so that the hydrolysis of the carbohydrate fraction to monomeric sugars can be achieved rapidly and with greater yields. Furthermore, EP has a great potential to disrupt the microbial cell walls within few seconds to bring out the intracellular materials (lipid) to the solution. Therefore, this study aims to describe the challenges and prospect of application of EP technique in biofuels processing.

Biocombustibles y agua. La transformación del espacio en Piura, Perú

The arrival of biofuels companies in the Chira Valley, Piura, Peru, in order to produce ethanol on sugarcane cultivation, intensified the agricultural use of land and water in the mid-2000s. This article analyzes the ecological, political and social transformations that biofuels production brought about in the valley. For that purpose the paper describes the role of the state in promoting biofuels and the concomitant land and water-grabbing processes in the valley. It also explores the consequences it had for local communities and medium-sized and small farmers. Ethanol production in the Chira valley produced a profound space transformation because land and water-grabbing processes for biofuels reinforced social inequalities. Information for this article was gathered from primary and secondarysources. This is a qualitative research. Eighteen interviews were conducted in Piura and Lima.

Effect of Biofuel Production on Sustainability of Agriculture

The article investigates the influence of energy efficiency achieved in biofuel production on the potential fulfilment of agricultural energy demand, and consequently on the sustainability of agricultural processes. The mathematical model of energy efficiency in biofuel production is extended to a more general form aiming to describe the effects of exclusion of a fraction of crops from food production towards satisfaction of the industrial demands.The derived model gives quantitative relations between energy efficiency of “energetic plantations”, energetic efficiency of industrial biofuel processing plants, and energy demand for other types of agricultural production.

Biomass Conversion to Produce Hydrocarbon Liquid Fuel Via Hot-vapor Filtered Fast Pyrolysis and Catalytic Hydrotreating.

Lignocellulosic biomass conversion to produce biofuels has received significant attention because of the quest for a replacement for fossil fuels. Among the various thermochemical and biochemical routes, fast pyrolysis followed by catalytic hydrotreating is considered to be a promising near-term opportunity. This paper reports on experimental methods used 1) at the National Renewable Energy Laboratory (NREL) for fast pyrolysis of lignocellulosic biomass to produce bio-oils in a fluidized-bed reactor and 2) at Pacific Northwest National Laboratory (PNNL) for catalytic hydrotreating of bio-oils in a two-stage, fixed-bed, continuous-flow catalytic reactor. The configurations of the reactor systems, the operating procedures, and the processing and analysis of feedstocks, bio-oils, and biofuels are described in detail in this paper. We also demonstrate hot-vapor filtration during fast pyrolysis to remove fine char particles and inorganic contaminants from bio-oil. Representative results showed successful conversion of biomass feedstocks to fuel-range hydrocarbon biofuels and, specifically, the effect of hot-vapor filtration on bio-oil production and upgrading. The protocols provided in this report could help to generate rigorous and reliable data for biomass pyrolysis and bio-oil hydrotreating research.

Biomass Conversion to Produce Hydrocarbon Liquid Fuel Via Hot-vapor Filtered Fast Pyrolysis and Catalytic Hydrotreating

Lignocellulosic biomass conversion to produce biofuels has received significant attention because of the quest for a replacement for fossil fuels. Among the various thermochemical and biochemical routes, fast pyrolysis followed by catalytic hydrotreating is considered to be a promising near-term opportunity. This paper reports on experimental methods used 1) at the National Renewable Energy Laboratory (NREL) for fast pyrolysis of lignocellulosic biomass to produce bio-oils in a fluidized-bed reactor and 2) at Pacific Northwest National Laboratory (PNNL) for catalytic hydrotreating of bio-oils in a two-stage, fixed-bed, continuous-flow catalytic reactor. The configurations of the reactor systems, the operating procedures, and the processing and analysis of feedstocks, bio-oils, and biofuels are described in detail in this paper. We also demonstrate hot-vapor filtration during fast pyrolysis to remove fine char particles and inorganic contaminants from bio-oil. Representative results showed successful conversion of biomass feedstocks to fuel-range hydrocarbon biofuels and, specifically, the effect of hot-vapor filtration on bio-oil production and upgrading. The protocols provided in this report could help to generate rigorous and reliable data for biomass pyrolysis and bio-oil hydrotreating research.

A Sustainable Partnership for Algal Biofuel Production and Waste Treatment for Cogeneration of Energy and Co-products

Background: Algal biofuel production can be made sustainable in partnership with dairy farms, industries and municipal systems for nutrient management requiring waste treatment. Waste streams contain unmined nutrients such as nitrogen, phosphorus, and carbon. The nutrients runoff especially nitrogen and phosphorus pollution can impair water quality of natural water bodies posing environmental threat due to undesirable algae blooms affecting natural aquatic communities. Anaerobic biodigesters can efficiently take care of biochemical oxygen demand to improve water quality but leave behind excess nutrients in the effluent. The excess nutrients can be potentially used for selected algal biomass growth for fuel and co-products. Methods: This paper reviews the algal biofuel systems that can integrate with biodigesters for sustainable cogeneration of renewable energy forms (liquid biofuels, electricity, and heat) so that the waste effluent from dairy farms, municipal and industrial anaerobic digesters, food and beverage and other industries can be combined with the algal biofuel process to produce additional valued co-products including feedstock for biogas, organic fertilizer, and animal feed for generating additional revenues. Conclusion: A successful implementation of a system as described will have multifold higher oil yield from non-food algae biomass compared to food sources (e.g. soybean and corn oil) for biofuel; benefit environment by capturing nitrogen and phosphorus from effluents to reduce environmentally harmful runoff affecting the health of natural water bodies, reduce in the fuel emissions especially the oxides of nitrogen in contrast to both diesel and conventional biodiesel, meet environmental protection regulations with reductions in particulate matter and total hydrocarbons; and bring economic benefits from marketable products across the complete supply chain involved at the sites that implement bolt on algal system with waste management systems for cogeneration of energy. Keywords: Algae, wastewater, nutrients, biofuel, cogeneration, digester, renewable diesel, fertilizer, animal feed, co-products.

Expanding the Knowledge on Lignocellulolytic and Redox Enzymes of Worker and Soldier Castes from the Lower Termite Coptotermes gestroi.

Termites are considered one of the most efficient decomposers of lignocelluloses on Earth due to their ability to produce, along with its microbial symbionts, a repertoire of carbohydrate-active enzymes (CAZymes). Recently, a set of Pro-oxidant, Antioxidant, and Detoxification enzymes (PAD) were also correlated with the metabolism of carbohydrates and lignin in termites. The lower termite Coptotermes gestroi is considered the main urban pest in Brazil, causing damage to wood constructions. Recently, analysis of the enzymatic repertoire of C. gestroi unveiled the presence of different CAZymes. Because the gene profile of CAZy/PAD enzymes endogenously synthesized by C. gestroi and also by their symbiotic protists remains unclear, the aim of this study was to explore the eukaryotic repertoire of these enzymes in worker and soldier castes of C. gestroi. Our findings showed that worker and soldier castes present similar repertoires of CAZy/PAD enzymes, and also confirmed that endo-glucanases (GH9) and beta-glucosidases (GH1) were the most important glycoside hydrolase families related to lignocellulose degradation in both castes. Classical cellulases such as exo-glucanases (GH7) and endo-glucanases (GH5 and GH45), as well as classical xylanases (GH10 and GH11), were found in both castes only taxonomically related to protists, highlighting the importance of symbiosis in C. gestroi. Moreover, our analysis revealed the presence of Auxiliary Activity enzyme families (AAs), which could be related to lignin modifications in termite digestomes. In conclusion, this report expanded the knowledge on genes and proteins related to CAZy/PAD enzymes from worker and soldier castes of lower termites, revealing new potential enzyme candidates for second-generation biofuel processes.

Microalgae biofuels: A comparative study on techno-economic analysis & life-cycle assessment

This work analyses the sustainability of microalgae-derived biofuel production by performing an extensive comparison of conversion pathways, one studied at the University of Aveiro (UA), Portugal and the other studied at the National Renewable Energy Laboratory (NREL), Golden, Colorado, USA. The objective of this comparison is to address each of these processing technologies from beginning to end by way of a life-cycle assessment and an economic feasibility analysis aimed at large-scale application. An integrated algal biofuel production model was established through the development of separate data inventories supporting both the UA and NREL scenarios. Among the processing technologies evaluated were solvent extraction, trans-esterification and product purification for biodiesel (UA), fermentation, distillation, and hydrodeoxygenation for renewable diesel (NREL). The computed minimum fuel selling prices (in 2011-year dollars) were $10.55/GGE (gasoline gallon equivalent) and $4.35/GGE for the UA-Portugal pathway and the NREL-USA case, respectively. The work shows that the valorization of co-products is particularly significant since it adds revenue which may be used to improve the final fuel selling price. Analysis of the NREL pathway shows that the algae biomass cultivation step contributes significantly (~50%) to total emissions, which emphasizes the decisive role the ‘microalgae growth phase’ plays in such a process. The life-cycle analysis, conducted with SimaPro software, shows that the biofuel processing technology adopted by UA, albeit simpler, requires upgrading in order to achieve optimum results: the lipid extraction process is extremely problematic because it contributes significantly to greenhouse gas (GHG) emissions and fossil energy consumption. Increasing the recovery of solvent (hexane) used during the process can play a major role in reducing total GHG emissions.

A geographical assessment of vegetation carbon stocks and greenhouse gas emissions on potential microalgae-based biofuel facilities in the United States

The microalgae biofuels life cycle assessments (LCA) present in the literature have excluded the effects of direct land use change (DLUC) from facility construction under the assumption that DLUC effects are negligible. This study seeks to model the greenhouse gas (GHG) emissions of microalgae biofuels including DLUC by quantifying the CO2 equivalence of carbon released to the atmosphere through the construction of microalgae facilities. The locations and types of biomass and Soil Organic Carbon that are disturbed through microalgae cultivation facility construction are quantified using geographical models of microalgae productivity potential including consideration of land availability. The results of this study demonstrate that previous LCA of microalgae to biofuel processes have overestimated GHG benefits of microalgae-based biofuels production by failing to include the effect of DLUC. Previous estimations of microalgae biofuel production potential have correspondingly overestimated the volume of biofuels that can be produced in compliance with U.S. environmental goals.

Dynamic flux balance modeling to increase the production of high-value compounds in green microalgae.

BackgroundPhotosynthetic organisms can be used for renewable and sustainable production of fuels and high-value compounds from natural resources. Costs for design and operation of large-scale algae cultivation systems can be reduced if data from laboratory scale cultivations are combined with detailed mathematical models to evaluate and optimize the process.ResultsIn this work we present a flexible modeling formulation for accumulation of high-value storage molecules in microalgae that provides quantitative predictions under various light and nutrient conditions. The modeling approach is based on dynamic flux balance analysis (DFBA) and includes regulatory models to predict the accumulation of pigment molecules. The accuracy of the model predictions is validated through independent experimental data followed by a subsequent model-based fed-batch optimization. In our experimentally validated fed-batch optimization study we increase biomass and upbeta-carotene density by factors of about 2.5 and 2.1, respectively.ConclusionsThe analysis shows that a model-based approach can be used to develop and significantly improve biotechnological processes for biofuels and pigments.

Empty Fruit Bunch from Date Palm Industries—A Sustainable Resource for Producing Biofuels and Industrial Solvents

Abstract Date palm empty fruit bunch (EFB) is a reliable and underutilized agriculture residue generated by the date industry. EFB contains polymeric sugars that can be converted to biofuel when subjected to pretreatment, enzymatic hydrolysis, and microbial fermentation. Optimized biofuel processing conditions produced 119 kg ethanol per dry metric ton EFB. The highest sugar conversions from enzymatic hydrolysis were found with Ammonia Fiber Expansion (AFEX™, MBI International, Lansing, MI) pretreatment conditions of 2:1 ammonia-to-biomass ratio, 80% moisture content, and a temperature of 120°C, for 30 min residence time. These conditions produced 52.5 g/L and 34.8 g/L of fermentable glucose and xylose, respectively. This hydrolysate was inoculated with a glucose- and xylose-consuming recombinant yeast strain producing 35.8 g/L and 31.8 g/L ethanol with and without nutrient supplementation, respectively. A complete mass balance for EFB pretreatment, enzymatic hydrolysis, and microbial fermentation is pres...

Predictive evaluation of phase equilibria in biofuel systems using molecular thermodynamic models

In this work an analysis of the predictive capacity of two molecular models was evaluated on phase equilibrium of systems involved in the biofuel processing. Group Contribution- Polar Perturbed- Chain Statistical Associating Fluid Theory (GC-PPC-SAFT) and Monte Carlo simulation were used. Predictive multiphase equilibria at low and high pressures were computed for alcohol+ethyl or methyl esters, alcohol+glycerol, water+glycerol and ethanol+water. An analysis of different association schemes of glycerol was performed. Heat of mixing was also used to assess the behavior of some systems. The predictions showed to be consistent with VLE data, with deviations<5% for alcohols+esters and alcohols+glycerol, water+glycerol; and 5.4% for ethanol+water. Studies using heats of mixing predicted by GC-PPC-SAFT and structural information provided by molecular simulation indicated the Scheme 4C is the most appropriate to describe the glycerol molecule.

Co-production of gasification based biofuels in existing combined heat and power plants – Analysis of production capacity and integration potential

Solid fuel fired fluidized bed (FB) boilers are common in combined heat and power (CHP) plants in district heating- and process industry. In this study, utilization of such FB boilers for production of syngas in dual fluidized bed gasifiers and subsequent catalytic biofuel production to substitute natural gas (SNG), methanol (MeOH) and Fischer-Tropsch fuel (FT) has been examined. Based on the hypothesis that waste-heat and tail gas from the biofuel processes can be utilized in the CHP plant, process configurations aiming for operationally robustness and low investment cost rather than maximum stand-alone efficiency have been explored and implemented in actual industrial cases and over the full operating range of the boilers. The results of the study show that significant improvements of overall efficiency can be achieved by integration of the biofuel processes in the CHP plants and that a relatively high biofuel production capacity can be achieved. SNG showed the highest obtainable efficiency and production capacity of the studied biofuels, whereas the FT process showed largest increase in terms of efficiency when integrated in the CHP plant, compared to its stand-alone efficiency.

Impact of biochemical composition on susceptibility of algal biomass to acid-catalyzed pretreatment for sugar and lipid recovery

One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We focus on the impact of compositional characteristics of biomass on the susceptibility to pretreatment in order to maximize the valorization of algal biomass conversion for biofuels and bioproducts. The release of monomeric carbohydrates in the aqueous phase and extractability of the lipid fraction was measured based a response surface methodology to find significant explanatory variables and interaction terms. We studied the effect of harvest timing on the conversion yields, using three algal strains; Chlorella vulgaris and Scenedesmus acutus and Nannochloropsis granulata representing three different nutritional metabolic phases. Four cultivation conditions of high (≥90 gallon gasoline equivalent/ton biomass) value for a combined sugar- and lipid-based biofuels process were identified. These four conditions represent either mid or late stage harvest cultivation regimes. The results indicate that acid pretreatment has potential to be applicable for a vast range of biomass samples to obtain high energy yields, but that the exact conditions and optima are dependent on the strain and likely the starting composition of the biomass.

Profits versus jobs: Evaluating alternative biofuel value-chains in Tanzania

Biomass production for bioenergy use may contribute to rural development by increasing household incomes, local employment and energy supply, especially in developing countries. This paper presents a value-chain approach to evaluating the profitability and competitiveness of producing biodiesel or ethanol. We apply a ‘rapid appraisal’ accounting framework to the case of Tanzania, which is a data scarce setting and therefore well-suited to the proposed approach. The framework also estimates the number of jobs created in the biofuel sector under different production arrangements and related demand for land resource. We evaluate the potential trade-offs between different scales of biofuel production (both the scale of feedstock production and biofuel processing). We find that only sunflower-biodiesel is profitable, especially if produced in large-scale estate farming systems. Estate farming is the best option for profits and competitiveness, even if domestic biofuel production is never competitive on the international market for energy. We also find that the number of jobs depends crucially on the involvement of smallholders. Establishing out-grower schemes (or similar arrangements), rather than estate farms, should be a key policy objective if biofuels production is going to improve rural economy. However social benefits may be gained at a cost of reduced international competitiveness and increased land exploitation.

Co-production of acetone and ethanol with molar ratio control enables production of improved gasoline or jet fuel blends.

The fermentation of simple sugars to ethanol has been the most successful biofuel process to displace fossil fuel consumption worldwide thus far. However, the physical properties of ethanol and automotive components limit its application in most cases to 10-15 vol% blends with conventional gasoline. Fermentative co-production of ethanol and acetone coupled with a catalytic alkylation reaction could enable the production of gasoline blendstocks enriched in higher-chain oxygenates. Here we demonstrate a synthetic pathway for the production of acetone through the mevalonate precursor hydroxymethylglutaryl-CoA. Expression of this pathway in various strains of Escherichia coli resulted in the co-production of acetone and ethanol. Metabolic engineering and control of the environmental conditions for microbial growth resulted in controllable acetone and ethanol production with ethanol:acetone molar ratios ranging from 0.7:1 to 10.0:1. Specifically, use of gluconic acid as a substrate increased production of acetone and balanced the redox state of the system, predictively reducing the molar ethanol:acetone ratio. Increases in ethanol production and the molar ethanol:acetone ratio were achieved by co-expression of the aldehyde/alcohol dehydrogenase (AdhE) from E. coli MG1655 and by co-expression of pyruvate decarboxylase (Pdc) and alcohol dehydrogenase (AdhB) from Z. mobilis. Controlling the fermentation aeration rate and pH in a bioreactor raised the acetone titer to 5.1 g L(-1) , similar to that obtained with wild-type Clostridium acetobutylicum. Optimizing the metabolic pathway, the selection of host strain, and the physiological conditions employed for host growth together improved acetone titers over 35-fold (0.14-5.1 g/L). Finally, chemical catalysis was used to upgrade the co-produced ethanol and acetone at both low and high molar ratios to higher-chain oxygenates for gasoline and jet fuel applications. Biotechnol. Bioeng. 2016;113: 2079-2087. © 2016 Wiley Periodicals, Inc.

Transportation fuel production from gasified biomass integrated with a pulp and paper mill - Part B: Analysis of economic performance and greenhouse gas emissions

This paper presents a comparison between four gasification-based biorefineries integrated with a pulp and paper mill. It is a continuation of 'Transportation fuel production from gasified biomass integrated with a pulp and paper mill - Part A: Heat integration and system performance'. Synthesis into methanol, Fischer-Tropsch crude or synthetic natural gas, or electricity generation in a gas turbine combined cycle, were evaluated. The concepts were assessed in terms of GHG (greenhouse gas) emissions and economic performance. Net annual profits were positive for all biofuel cases for an annuity factor of 0.1 in the year 2030; however, the results are sensitive to biofuel selling prices and CO2,eq charge. Additionally, GHG emissions from grid electricity are highly influential on the results since all biofuel processes require external power. Credits for stored CO2 might be necessary for processes to be competitive, i.e. storage of separated CO2 from the syngas conditioning has an important role to play. Without CO2 storage, the gas turbine case is better than, or equal to, biofuels regarding GHG emissions. Efficiency measures at the host mill prior to heat integration of a gasification process are beneficial from the perspective of GHG emissions, while having a negative impact on the economy.

Sulfolane pretreatment of shrub willow to improve enzymatic saccharification

Pretreatment has been regarded as the most efficient strategy for conversion of lignocellulosic biomass to fermentable sugars. In this work, sulfolane pretreatment was performed to break the intricate structure of shrub willow for inhabitation of the enzymatic accessibility to holocellulose. The effects of varying pretreatment parameters on enzymatic hydrolysis of shrub willow were investigated. It was found that sulfolane was more compatible with lignin instead of carbohydrate, and the loss of carbohydrate could be attributed to water and acid generated from sulfolane. The optimum conditions leading to maximal sugar recovery from enzymatic saccharification were confirmed. After pretreatment of shrub willow powder in sulfolane at 170 °C for 1.5 h with mass ratio of sulfolane to substrate of 5, the sugar release could reach 555 mg/g raw materials (352 mg glucose, 203 mg xylose) when combining 20 FPU cellulase, 20 CBU β-glucosidase, and 1.5 FXU xylanase, representing 78.2 % of glucose and 56.6 % of xylose in shrub willow. This enhanced enzymatic saccharification was due to delignification and removal of a proportion of hemicelluloses, as confirmed by X-ray diffraction analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, gas chromatography, and ionic chromatography. Thus, these studies prove sulfolane pretreatment to be an effective and promising approach for biomass to biofuel processing.

Process simulator-based optimization of biorefinery downstream processes under the Generalized Disjunctive Programming framework

Downstream processing of biofuels and bio-based chemicals represents a challenging problem for process synthesis and optimization, due to the intrinsic nonideal thermodynamics of the liquid mixtures derived from the (bio) chemical conversion of biomass. In this work, we propose a new interface between the process simulator PRO/II (SimSci, Schneider-Electric) and the optimization environment of GAMS for the structural and parameter optimization of this type of flowsheets with rigorous and detailed models. The optimization problem is formulated within the Generalized Disjunctive Programming (GDP) framework and the solution of the reformulated MINLP problem is approached with a decomposition strategy based on the Outer-Approximation algorithm, where NLP subproblems are solved with the derivative free optimizer belonging to the BzzMath library, and MILP master problems are solved with CPLEX/GAMS. Several validation examples are proposed spanning from the economic optimization of two different distillation columns, the dewatering task of diluted bio-mixtures, up to the distillation sequencing with simultaneous mixed-integer design of each distillation column for a quaternary mixture in the presence of azeotropes.