Biofuel Production Systems Research Articles

System-level energy consumption modeling and optimization for cellulosic biofuel production

As a promising alternative to fossil fuels, cellulosic biofuel has obtained considerable interest due to its potential for mitigating global climate change and enhancing energy security. However, the widespread adoption of cellulosic biofuel is taking place in a slower pace than expected. One major challenge is that the cellulosic biofuel production is still highly energy-intensive. In fact, the energy contained in cellulosic biofuel is less than the energy required for its production. To address this issue, in this paper, an analytical system-level energy model is proposed to characterize the fundamental relationships between total energy consumption and biofuel production parameters in cellulosic biofuel production systems. Furthermore, an optimization strategy based on Particle Swarm Optimization (PSO) is adopted to minimize the energy consumption of cellulosic biofuel production while maintaining the desired biofuel yield. A baseline case is implemented for analyzing energy consumption, and the results show that pretreatment consumes most energy among all processes and the water/biomass ratio is the most significant energy driver. In addition, the optimal solution results in a 21.09% reduction in the total energy consumption compared to the baseline case.

Whole genome sequence analysis of Geitlerinema sp. FC II unveils competitive edge of the strain in marine cultivation system for biofuel production

A filamentous cyanobacteria, Geitlerinema sp. FC II, was isolated from marine algae culture pond at Reliance Industries Limited (RIL), India. The 6.7 Mb draft genome of FC II encodes for 6697 protein coding genes. Analysis of the whole genome sequence revealed presence of nif gene cluster, supporting its capability to fix atmospheric nitrogen. FC II genome contains two variants of sulfide:quinone oxidoreductases (SQR), which is a crucial elector donor in cyanobacterial metabolic processes. FC II is characterized by the presence of multiple CRISPR- Cas (Clustered Regularly Interspaced Short Palindrome Repeats – CRISPR associated proteins) clusters, multiple variants of genes encoding photosystem reaction centres, biosynthetic gene clusters of alkane, polyketides and non-ribosomal peptides. Presence of these pathways will help FC II in gaining an ecological advantage over other strains for biomass production in large scale cultivation system. Hence, FC II may be used for production of biofuel and other industrially important metabolites.

The relative importance of the bacterial pathway and soil inorganic nitrogen increase across an extreme wood‐ash application gradient

AbstractAsh from combustion of biofuels, for example wood chips, is often deposited as waste, but due to its high content of essential plant nutrients and alkalinity, it has been proposed to recycle ash as a fertilizer and liming agent in biofuel production forest. However, current legislation sets rather strict limitations for wood‐ash application in biofuel production systems. The soil microfood web, that is microorganisms and their microfaunal grazers, protozoa and nematodes, is pivotal for essential ecosystem processes such as decomposition and plant nutrient release. Therefore, a thorough assessment of the impacts on microfood web structure and functioning must precede actions towards raising the currently allowed application rates. In a Danish Norway spruce plantation, we evaluate the impact of wood ash applied at dosages from 0 to the extreme case of 90 t ash ha−1 on the microfood web, the bacterial community structure, soil content of inorganic nitrogen, organic matter, dissolved organic carbon and nitrogen. Using structural equation modelling (SEM), we disentangled the direct effect of the disturbance imposed by ash per se, the associated pH increase and changes in prey abundance on individual organism groups in the microfood web. The SEM showed that the pH rise was the main driver of increasing abundances of culturable heterotrophic bacteria with increasing ash doses, and via trophical transfer, this also manifested as higher abundances of bacterial grazers. Fungal‐feeding nematodes were unaffected by ash, whereas carnivorous/omnivorous nematodes decreased due to the direct effect of ash. Increasing ash doses enhanced the difference between bacterial communities of control plots and ash‐amended plots. The ash‐induced stimulation of culturable heterotrophic bacteria and bacterial grazers increased inorganic nitrogen availability at ash doses of 9 t ha−1 and above. Hence, raised limits for ash application may potentially benefit tree growth via enhanced N mineralization activity of the soil food web.

Greenhouse gas and energy balance of Jatropha biofuel production systems of Burkina Faso

Jatropha curcas has been introduced as a low-cost energy crop in Burkina Faso for the production of straight vegetable oil (SVO) and biodiesel. It is cultivated in different plantation systems including smallholder inter-plantings with annual crops, large-scale monoculture, afforestation on marginal land, in traditional hedge systems along contour stone walls, and in living fences. We performed Life Cycle Assessment of these Jatropha systems using empirical data on yields and carbon stocks, and accounting for changes in agro-ecosystem provisioning and regulating services that occurred after the land conversion to Jatropha. The study found that all J. curcas production pathways substantially reduced greenhouse gas emission (68–89%) and saved energy (65–90%) compared to diesel fuel. Highest values are achievable under the assumption that by-products (husks, seed cake, glycerin) are used for energy generation. The decentralized production of SVO supplied by feedstocks from intercropping and hedgerow systems seems to be most promising option. However, very low land-use efficiency (6.5–9.5 GJ ha−1 production) characterized Jatropha intercropping and monoculture plantations, rendering the plant a competitor to food crops and increasing the risk of conversion of savanna land to Jatropha cultivation. Jatropha plantings on marginal lands largely failed. High labor requirements constrain integration of Jatropha plantation systems within small farmholdings. Currently, the traditional hedge systems show the lowest land-use replacement potential and labor needs while providing multiple ecosystem services, but alone cannot satisfy rural energy needs. In order to reach energy supply targets without claiming more land and compromising other ecosystem services, the J. curcas plantation systems in Burkina Faso need to be made more efficient through plant breeding and improved agronomic management.

Emergy analysis for transportation fuels produced from corn stover in China

In order to provide more useful information for the decision makers in China to implement sustainable energy policies and to identify which region in China is most suitable to build the biofuel production plants for fast pyrolysis and hydroprocessing of corn stover, the present study has evaluated the production efficiency and sustainability of large-scale transportation fuel production via fast pyrolysis and hydroprocessing of corn stover in China using emergy analysis approach. Both the hydrogen production scenario (i.e. oil hydroprocessing using the hydrogen derived from bio-oil reforming) and the hydrogen purchase scenario (i.e. oil hydroprocessing using the hydrogen purchased from market) in three regions of China (Northeast China Plain (NECP), North China Plain (NCP) and Shaanxi Province (SXP)) have been investigated. The results have shown that maize production, and fast pyrolysis and hydroprocessing are the two biggest emergy input stages of the biofuel production system. The comparison of the emergy indices of all of the six cases investigated indicates that the hydrogen purchase scenario in NCP is the best biofuel production case due to its second best sustainability and the second highest production efficiency. In comparison to bioethanol from cassava chips and wheat and biodiesel from jatropha curcas L, the hydrogen purchase scenario in NCP is also the most sustainable plan for a biofuel production plant in China. As water, fertilizer and hydrogen are the three biggest emergy inputs in this case, improvements on the water management, fertilizer management and hydrogen production technology have been discussed. In order to further increase the efficiency and sustainability of the hydrogen purchase scenario in NCP, some of the necessary efforts required from the relevant sectors have also been put forward based on the results of the emergy analysis.

An environmentally sustainable process for remediation of phenol polluted wastewater and simultaneous clean energy generation as by-product

The study reports a novel algal system for biofuel production coupled to phenol remediation. High-performance liquid chromatography analysis shows phenol-acclimatized Chlorella pyrenoidosa completely degrades high phenol concentrations of 50–1200 mg/l. The ability of C. pyrenoidosa to efficiently grow on high phenol concentrations was endorsed by its high growth kinetic parameters of Ks (400.54 mg/l) and KI (800.41 mg/l). An enhanced growth rate of 0.072 h−1 was obtained by utilizing optimized physical parameters of biomass concentration (200 mg/l), photoperiodicity (14 h light: 10 h dark) and pH 7. Preadaptation of C. pyrenoidosa to target phenol concentration before actual application for phenol treatment is proposed as a strategy for eliminating lag phase and thus faster growth (0.078 h−1) and degradation (0.561 h−1) rates. Preadaptation further increases µmax (0.22 h−1), Ks (500.54 mg/l) and KI (900.41 mg/l) enhancing efficiency for growth on high phenol concentrations. The practical applicability of C. pyrenoidosa for phenol contaminated wastewater remediation was proved by its ability to completely degrade 10 and 250 mg/l phenol in petroleum refinery wastewater. Phenol stress induced total and neutral lipid production in algal biomass qualifying the spent biomass as a promising source for biodiesel production. Additionally, the residual biomass after lipid extraction served as substrate for bioethanol fermentation adding to efficiency of the process for biofuel applications. These findings suggest an environmentally sustainable process for treatment of phenol pollution and clean energy production which is the need of the hour. The developed process has been covered by an applied patent.

Perspectives on Investment Cost Estimates for Gasification-based Biofuel Production Systems

This study presents investment cost estimates for three different gasification based biofuel production systems producing synthetic natural gas (SNG), methanol and Fischer-Tropsch (FT) fuels. A comparison of cost estimates for similar systems presented in the scientific literature and technical reports was also made. The comparison is made on a common basis for a gasifier capacity of 480 MWth LHV biomass input. Results show that for all three fuels most of the compared estimates fall within the similar to 30 % uncertainty range of a study estimate. The Chemical Plant Cost Index (CEPCI) was used for updating cost estimates to the money value in 2012. An analysis of the impact of using alternative cost escalating indices showed that two of the most commonly used cost escalating indices, the CEPCI and CERA DCCI (downstream capital cost index), gave differences in total plant investment of as much as 30 % for long or specific updating periods. For short updating periods the difference was small. These results underline the importance of sensitivity analysis for investment costs in the analysis of profitability for 2nd generation biofuel plants.

Life Cycle Optimization for Sustainable Algal Biofuel Production Using Integrated Nutrient Recycling Technology

In this study, a multi-objective optimization of sustainable integration of algal biofuel production using nutrient recycling technology, such as anaerobic digestion and hydrothermal liquefaction, is considered. Gross annual profitability and global warming potential (GWP) are the criteria chosen for the design of the algal biofuel production system. Three scenarios, such as full-scale (baseline), pilot-scale (conservative), and lab-scale (nominal), are chosen based on the expected maturity levels and nutrient demand. The results of the optimization produce Pareto sets of optimal solutions for acknowledging the trade-off between the economic and the environmental criteria of the integrated system. It is found that the anaerobic digestion (AD) technology shows better performance in terms of an environmental perspective, displacing the excessive fertilizer requirements due to its maturity in comparison with the hydrothermal liquefaction (HTL) process. However, HTL is a new, evolving, promising nutrient recy...

3-3-1 微細藻類由来バイオ燃料生産システムの最適化に向けた細胞破砕プロセスの実験的検討(Session 3-3 藻類)

3-3-1 微細藻類由来バイオ燃料生産システムの最適化に向けた細胞破砕プロセスの実験的検討(Session 3-3 藻類)

Energy life-cycle analysis of soybean biodiesel: Effects of tillage and water management

The purpose of this paper is to carry out an updated energy Life-Cycle Assessment of soybean biodiesel produced in the Pampean region of Argentina and to analyze the influence of different tillage systems on the Energy Return on Investment (EROI). It aims to identify the processes, materials and methodological aspects that significantly affect biofuel EROI. The procedure considers the main processes and operations of both the agriculture and industrial stages of biofuel production system, but the main novelty of this study is linking EROI with farming and conservation practices and not in the chemical processing of the oil. The results obtained represent the current average energetic performance of soy-based biodiesel produced in the considered region. The EROI values are very encouraging, demonstrating that this biodiesel provides a net energy gain. The results also show that conservation agriculture and the implementation of practices that improve crop yield do not always determine better energetic performance. Sensitivity analysis confirms that EROI values of soybean biodiesel are more responsive to methodological choices such as the system's boundary definition and the choice of the allocation method rather than to the physical aspects of the productive system such as tillage and water management practices.

Energy Efficiency of a Biofuel Production System

Abstract Manufacturing engineering is supposed to provide analyses related to various aspects of manufacturing and production in order to maximise technological, energy, and economic gains in relevant production processes. The present paper gives a recapitulation of several publications by present authors, presenting considerations of the energy efficiency of biofuel production. The energy efficiency is understood as the ratio of energy obtained from biofuels produced basing on crops from a particular area to the energy required to satisfy needs of all subsidiary processes assuring correct functioning of the production system, starting from operations aimed to obtain agricultural crops, and ending with the conversion of the crops onto biofuels. Derived by the present authors, the mathematical model of energy efficiency of biofuel production is extended to a more general form, and applied to the analysis of quantitative relations between energy efficiency of sc. “energy plantations”, and further elements of biofuel production system converting harvested biomass into biofuel. Investigations are aimed towards the determination of the role of biomass as a source of energy.

Computer modelling of the influences of a subsystems’ interaction on energetic efficiency of biofuel production systems

Energetic efficiency of biofuel production systems, as well as that of other fuels production systems, can be evaluated on the basis of modified EROEI indicator. In earlier papers, a new definition of the EROEI indicator was introduced. This approach enables the determination of this indicator separately for individual subsystems of a chosen production system, and therefore enables the studies of the influence of every subsystem on the energetic efficiency of the system as a whole. The method has been applied to the analysis of interactions between agricultural, internal transport subsystems, as well as preliminary studies of the effect of industrial subsystem.

Nutrient resource requirements for large-scale microalgae biofuel production: Multi-pathway evaluation

Growing demand for energy worldwide has increased interest in the production of renewable fuels, with microalgae representing a promising third generation feedstock. This study presents the use of a modular engineering process model, informed through literature, to evaluate the nitrogen and phosphorus resource demand of five microalgae to biofuels production systems. The baseline scenario, representative of an economically viable large-scale production system, includes sub-process models for growth, dewater, lipid extraction, anaerobic digestion, and biofuel conversion. Baseline modeling results combined with current US resource availability from fertilizer and wastewater show nitrogen and phosphorus requirements represent a potential barrier to the large-scale development of microalgae based biofuels. Baseline results show municipal wastewater sources can provide sufficient nutrients to produce 3.8billion gallons of fuel per year, corresponding to 6% of the DOE goal of 60billion gallons per year. Results from modeling of alternative production scenarios shows hydrothermal liquefaction to be a promising technology in terms of resource consumption. The use of lipid extracted algae as a value-added co-product is shown to be limitting due to nutrient recovery requirements for scalability. Optimistic and conservative process scenarios are simulated to bound the total resource demand and represent practical best and worst case scenarios.

Multi-objective exergy-based optimization of a continuous photobioreactor applied to produce hydrogen using a novel combination of soft computing techniques

This work was aimed at proposing a flexible and reliable framework based on combination of three soft computing techniques, i.e., artificial neural network, genetic algorithm, and fuzzy systems for multi-objective exergetic optimization of continuous photobiohydrogen production process from syngas by Rhodospirillum rubrum bacterium. To this end, artificial neural network (ANN) coupled with fuzzy clustering method (FCM) to model exergetic outputs on the basis of input variables. The outputs of modeling system were then fed into a novel optimization approach developed by hybridizing additive linear interdependent fuzzy multi-objective optimization (ALIFMO) and the elitist non-dominated sorting genetic algorithm (NSGA-II). The optimization was carried out to minimize the normalized exergy destruction and maximize the rational and process exergetic efficiencies, simultaneously. The solutions of the proposed approach were also compared with conventional fuzzy multi-objective optimization procedure with independent objectives. Overall, the modeling system predicted the exergetic parameters of photobioreactor with a coefficient of determination higher than 0.90. Furthermore, the optimization approach suggested syngas flow rate of 13.35 mL/min and agitation speed of 383.34 rpm as the best operational condition by considering the preferences of process exergy efficiency, rational exergy efficiency, and normalized exergy destruction, respectively. This condition could yield the normalized exergy destruction of 1.56, process exergetic efficiency of 21.66%, and rational exergetic efficiency of 85.65%. The obtained results showed the superiority of the proposed approach over the conventional fuzzy method in optimizing the complex biofuel production systems.

Socio-economic impact of Biofuel Agroforestry Systems on Smallholder and Large-holder Farmers in Karnataka, India

Biofuel production systems used hitherto have often been marred by controversies such as food versus fuel and the failure of Jatropha plantations. Biofuel Agroforestry Systems have the potential to address these concerns. This paper analyses the tree borne non-edible oilseed production benefits, generated by planting number multipurpose trees grown on the bunds and borders of agricultural fields including marginal and degraded lands known as Smallholder Biofuel Agroforestry System. It considers two different strategies (strategy 1 and 2) for both Smallholder and Large-holder Farmers for analysis. In each case, the two strategies differ in terms of the magnitude of investment required; the operational practices required and the net incremental benefit potential at the farm level. The tree species being used are Pongamia (Millettia pinnata), Simarouba (Simarouba glauca), Rubber (Hevea brasiliensis) and Neem (Azadirachta indica). The aim of this study is to understand and analyse the socio-economic impact of Karnataka State Bioenergy Development Board’s (KSBDB) Programme on Biofuel Agroforestry System on Smallholder and Large-holder Farmers. Field interviews and corresponding economic modelling analysis shows that the Programme has potential to deliver a small incremental income to Smallholder Farmers, especially during the ‘lean’ non-harvesting period of the year. The sensitivity analysis around the seed and end-product prices shows that Biofuel Agroforestry System has a potential to boost income levels of Smallholder Farmers by a significant amount—up to 60% over starting income in a time period of 25 years.

Soil water infiltration affected by topsoil thickness in row crop and switchgrass production systems

Conversion of annual grain crop systems to biofuel production systems can restore soil hydrologic function; however, information on these effects is limited. Hence, the objective of this study was to evaluate the influence of topsoil thickness on water infiltration in claypan soils for grain and switchgrass (Panicum virgatum L.) production systems. The experiment was performed at the University of Missouri South Farm (38°54′N, 92°16′W) on a Mexico silt loam (Vertic Luvisols) soil. Since 2009, plots were planted with either switchgrass or a corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation. Infiltration rates were measured using ponded infiltrometers during two years (2014 and 2015) under switchgrass and grain crop management each with two levels of topsoil thickness (0 and 37.5cm). Physically-based Parlange and Green-Ampt infiltration models were used to estimate saturated hydraulic conductivity (Ks) and sorptivity (S) parameters. Switchgrass planted on degraded soil (shallow topsoil treatment) resulted in greater Ks, S, qs (quasi-steady infiltration rate) and Kfs (field-saturated hydraulic conductivity) values than with row crop management for both 2014 and 2015 measurement years. Results for selected 24-hour mean frequency (11.8, 14.2, and 16.2cm) storms showed that switchgrass production systems enhanced estimated water infiltration, reduced estimated runoff, and decreased estimated time from water ponding to end of ponding compared with row crop management. Switchgrass is recommended to be planted on degraded soils especially in claypan landscapes for improved water use.

Zymomonas mobilis as a model system for production of biofuels and biochemicals.

Summary Zymomonas mobilis is a natural ethanologen with many desirable industrial biocatalyst characteristics. In this review, we will discuss work to develop Z. mobilis as a model system for biofuel production from the perspectives of substrate utilization, development for industrial robustness, potential product spectrum, strain evaluation and fermentation strategies. This review also encompasses perspectives related to classical genetic tools and emerging technologies in this context.

Multi-objective exergetic optimization of continuous photo-biohydrogen production process using a novel hybrid fuzzy clustering-ranking approach coupled with Radial Basis Function (RBF) neural network

This work was focused on the development of a novel hybrid fuzzy clustering-ranking approach coupled with radial basis function (RBF) neural network for the optimization of the key operational parameters for hydrogen production from photo-fermentation. The bioconversion of syngas to hydrogen via water-gas shift (WGS) reaction was carried out using the light-dependent microorganism Rhodospirillum rubrum and acetate as the sole carbon source. The RBF neural network was used to correlate exergetic outputs (normalized exergy destruction as well as rational and process exergetic efficiencies) to two exogenous input variables (culture agitation speed and syngas flow rate). The developed RBF model was interfaced with the proposed hybrid fuzzy clustering-ranking algorithm to simultaneously maximize the rational and process exergetic efficiencies and minimize the normalized exergy destruction. Moreover, the conventional fuzzy optimization algorithm was applied in order to assess the capability of the proposed approach over the existing methods for multi-objective optimization of complex biofuel production systems such as a continuous photobioreactor with respect to the sustainability and productivity issues. Once the development of the objective functions were carried out using RBF Neural Networks, the proposed algorithm was able to identify the optimum exergetically-sustainable operational parameters of carbon monoxide fermentation to biohydrogen with 20 clusters. This corresponded to the syngas flow rate of 13.68 mL/min and culture agitation speed of 348.62 rpm yielding the process exergetic efficiency of 16.46%, rational exergetic efficiency of 91.59%, and normalized exergy destruction of 2.14. The predicted optimum values by the proposed algorithm in this study were more suitable compared with the conventional fuzzy method. Therefore, the novel algorithm developed in this study may be a promising approach for navigation of the most cost-effective and environmental friendly operational parameters for fermentative hydrogen production from pilot and large scale photobioreactors.

Techno-economic and Monte Carlo probabilistic analysis of microalgae biofuel production system

This study focuses on the characterization of the technical and economic feasibility of an enclosed photobioreactor microalgae system with annual production of 37.85 million liters (10 million gallons) of biofuel. The analysis characterizes and breaks down the capital investment and operating costs and the production cost of unit of algal diesel. The economic modelling shows total cost of production of algal raw oil and diesel of $3.46 and $3.69 per liter, respectively. Additionally, the effects of co-products’ credit and their impact in the economic performance of algal-to-biofuel system are discussed. The Monte Carlo methodology is used to address price and cost projections and to simulate scenarios with probabilities of financial performance and profits of the analyzed model. Different markets for allocation of co-products have shown significant shifts for economic viability of algal biofuel system.

Life cycle assessments, carbon footprints and carbon visions: Analysing environmental systems analyses of transportation biofuels in Sweden

To ensure the sustainable production and consumption of biofuels, an increasing body of scientific literature has become available in recent years focusing on the environmental impacts of biofuels. Whilst the climate change mitigation is perhaps the primary driver behind the promotion of biofuels, climate change is not the only crucial impact associated with biofuel production and consumption systems. This study aims at analysing the extent of the dominant focus on climate impacts in Swedish research applying environmental systems analysis (ESA) tools to investigate the environmental impacts of biofuels, and why this may exist. A systematic literature review of Swedish research applying ESA tools in the study of transportation biofuels between 2000 and 2015 was conducted; identifying 64 studies. The results indicate that studies using life cycle assessment include a range of impact categories in addition to climate impacts, e.g. acidification and eutrophication. However, when also considering environmental footprints (i.e., carbon and water footprints) and material flow analyses, the dominance of carbon footprints leads to an overly dominant focus on climate impacts at the expense of other impact categories. The consideration of environmental impacts other than those related to climate impacts is discussed in terms of the influence of the dominant science-policy framework in Sweden and study dependent variables, such as data uncertainty and methodological limitations. Whilst biofuel production is inextricably linked to climate policy, the environmental impacts of Swedish biofuel production and consumption should also consider the broader context of the Swedish National Environmental Objectives.