Cost Of Biofuel Production Research Articles

Carbon Sources for Polyhydroxyalkanoates and an Integrated Biorefinery

Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs’ biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels’ production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs.

Stimulatory effect of auxins on the growth and lipid productivity of Chlorella pyrenoidosa and Scenedesmus quadricauda

This study investigated the impact of various auxins on microalgal growth and cellular composition. Two freshwater algae, i.e., Chlorella pyrenoidosa and Scenedesmus quadricauda were used. Results were analyzed using principal component analysis (PCA) and canonical correspondence analysis (CCA). The stimulatory effect of auxins on lipid content and lipid production was found to be as follows: indole-3-propionic acid (IPA)>indole-3-acetic acid (IAA)>indole-3-butyric acid (IBA)>naphthalene acetic acid (NAA). This is the first report of an increased stimulatory effect of IPA on microalgae that differs from previous study. A concentration of 60mgL−1 IPA caused the maximum growth rate, which increased 3 fold compared to the control. Lipid productivity in the samples treated with auxins was generally higher than the controls, and reached 4 fold higher with the addition of IPA. Using PCA, this study provided evidence that IBA and NAA show similar stimulatory effects on cellular composition. The increase in biomass and lipid productivity demonstrates the potential application of plant hormones for improving microalgae growth in commercial-scale cultivation and thus reducing the cost of biofuel production.

Simultaneous saccharification and fermentation of cactus pear biomass—evaluation of using different pretreatments

Lignocellulosic biomasses of two species of cactus pear (Opuntia ficus indica and Nopalea cochenillifera) were tested for the production of ethanol. Their ability to grow in water-stressed regions makes them eligible for reducing the production cost of biofuels in drought regions. The biomass was pretreated using three different strategies: alkaline hydrogen peroxide, alkaline using NaOH, and acid using H2SO4 followed by alkaline delignification with NaOH. Analyses of the composition, crystallinity, and enzymatic hydrolysis were performed on the material before and after pretreatment. An experimental design was used to evaluate the influence of temperature and initial cellulose concentration on the process of simultaneous saccharification and fermentation (SSF) using the pretreated material, which showed the best performance in previous tests, and two strains of Saccharomyces cerevisiae (PE-2 and LNF CA-11). Biomass characterization showed a content of 31.55% cellulose, 17.12% hemicelluloses, and 10.25% lignins for N. cochenillifera and 34.86% cellulose, 19.97% hemicelluloses, and 15.72% lignins for O. ficus indica. The alkaline pretreatment provided the best enzymatic saccharification yields. The SSF experiments resulted in the greatest cellulose-to-ethanol yields using strain PE-2 with the pretreated N. cochenillifera (93.81%) at 40°C and an initial cellulose concentration of 4%. N. cochenillifera showed better yields than O. ficus indica, and the PE-2 strain performed better than CA-11. These results suggest a good potential for cactus pear cladodes in the production of cellulosic ethanol.

Effect of bacterial amylase pretreatment on alcohol production from starch-based solid waste

ABSTRACTA number of different pretreatments involving biological, chemical, physical, and thermal approaches have been investigated over the years to reduce the cost of biofuel production. This study investigates the effect of bacterial amylase pretreatment on bioethanol production from different kinds of starch-based solid waste. We have isolated one strain (Xenorhabdus japonica) of amylase-producing bacteria from municipal waste dumping site's soil. Maximum ethanol yield was obtained after bacterial amylase pretreatment from wheat bread and rice (132 g/L), while the minimum was obtained from potato (99 g/L). Bacterial amylase pretreatment shows the best results as compared to the acid pretreatment.

초음파를 이용한 미세조류 응집에 관한 수치해석 연구

Abstract - In spite of various merit of algae as biofuel, the production cost of algae is a considerable obstacle for commercialization. The concurrent development of essential technologies is needed for the cultivating, harvesting, extracting and energy transformation. The production cost of algae biofuel has still higher than that of the other commercial biofuel. The major research activity has been focused on the cultivating and the research of other processes has been done with relatively lower activity. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae with the hybrid technology using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources.The present research is investigated for the effective separation of algae from water with the ultrasonics wave. The aim of the present research is focused on the establishment of optimal design of algae agg-lomeration system. For this purpose, the computational fluid dynamic analysis has been conducted in the flow field with ultrasonic wave and algae flow to clarify the mechanism of algae separation by ultrasonic wave.

Comprehensive techno-economic analysis of wastewater-based algal biofuel production: A case study

Combining algae cultivation and wastewater treatment for biofuel production is considered the feasible way for resource utilization. An updated comprehensive techno-economic analysis method that integrates resources availability into techno-economic analysis was employed to evaluate the wastewater-based algal biofuel production with the consideration of wastewater treatment improvement, greenhouse gases emissions, biofuel production costs, and coproduct utilization. An innovative approach consisting of microalgae cultivation on centrate wastewater, microalgae harvest through flocculation, solar drying of biomass, pyrolysis of biomass to bio-oil, and utilization of co-products, was analyzed and shown to yield profound positive results in comparison with others. The estimated break even selling price of biofuel ($2.23/gallon) is very close to the acceptable level. The approach would have better overall benefits and the internal rate of return would increase up to 18.7% if three critical components, namely cultivation, harvest, and downstream conversion could achieve breakthroughs.

Enhancement of nutrient recovery from microalgae in hydrothermal liquefaction using activated carbon

For large-scale biofuel production from microalgae, the following outcomes are needed to reduce environmental impact and biofuel production cost 1) extraction of a large amount of lipid (bio-oil), 2) recovery of almost all nutrients and their reuse for cultivation, and 3) effective utilization of solid residue (char). We investigated the possibility of using activated carbon to enhance recovery of bio-oil and nutrients in hydrothermal liquefaction (HTL). Microalga Fistulifera solaris was reacted at 573K and 10MPa for 0–60min with or without commercial activated carbon (0.5–5.0wt.% of microalgae) in an autoclave reactor. Results show 0.5wt.% activated carbon can substantially promote total nitrogen recovery in the aqueous phase, probably because of catalytic effect of activated carbon on the decarboxylation reactions to produce amines. Larger amount of activated carbon (>1.0wt.%) decreasd bio-oil recovery due to adsorption. A kinetic study of nitrogen recovery in the aqueous phase showed the apparent reaction order was 3 and the reaction rates were 1.1×10−7s−1 and 5.6×10−8s−1 with and without activated carbon, respectively. 0.5wt.% of activated carbon has an insignificant influence on bio-oil and phosphorus recovery.

Techno-economic analysis of solar integrated hydrothermal liquefaction of microalgae

Integration of Hydrothermal Liquefaction (HTL) of microalgae biomass with concentrated solar power thermal processing (CSP) for bio-oil production is a potential processing pathway for energy efficient generation of renewable biofuels. Solar HTL infrastructure avoids additional bolt-on components of conventional solar parabolic trough systems used for electricity production including heat transfer fluids, counter current heat exchangers, fluid transfer interconnectivity and electrical power control systems. The absence of such capital intensive additional equipment considerably reduces the production costs of solar HTL biofuels compared to electricity generation from conventional CSP power systems. An economic and market appraisal of variance and system economic resilience is presented. It is hypothesised that the combination of nutrient recycling with HTL/CSP unification has the potential for economically sustainable microalgae bio-oil production. A microalgae biofuel minimum fuel sales price of $1.23/kg has been modelled. Further experimental work would be able to validate this integrated model.

Continuous-flow sorting of microalgae cells based on lipid content by high frequency dielectrophoresis

This paper presents a continuous-flow cell screening device to isolate and separate microalgae cells (Chlamydomonas reinhardtii) based on lipid content using high frequency (50 MHz) dielectrophoresis. This device enables screening of microalgae due to the balance between lateral DEP forces relative to hydrodynamic forces. Positive DEP force along with amplitude-modulated electric field exerted on the cells flowing over the planar interdigitated electrodes, manipulated low-lipid cell trajectories in a zigzag pattern. Theoretical modelling confirmed cell trajectories during sorting. Separation quantification and sensitivity analysis were conducted with time-course experiments and collected samples were analysed by flow cytometry. Experimental testing with nitrogen starved dw15-1 (high-lipid, HL) and pgd1 mutant (low-lipid, LL) strains were carried out at different time periods, and clear separation of the two populations was achieved. Experimental results demonstrated that three populations were produced during nitrogen starvation: HL, LL and low-chlorophyll (LC) populations. Presence of the LC population can affect the binary separation performance. The continuous-flow micro-separator can separate 74% of the HL and 75% of the LL out of the starting sample using a 50 MHz, 30 voltages peak-to-peak AC electric field at Day 6 of the nitrogen starvation. The separation occurred between LL (low-lipid: 86.1% at Outlet # 1) and LC (88.8% at Outlet # 2) at Day 9 of the nitrogen starvation. This device can be used for onsite monitoring; therefore, it has the potential to reduce biofuel production costs

Isolation of microalgae with growth restriction and nutrient removal from alkaline wastewater

In order to isolate a well-tolerated microalgae strain and study its capability of wastewater treatment, a newly microalgae strain was isolated and identified from fresh water. The phylogenetic analysis indicates that this strain has a close relationship with Desmodesmus sp., named as EJ 9-2. The effects of temperature, pH value and NaCl concentration on growth of Desmondesmus sp. were investigated; the capability of nutrient removal from alkaline wastewater was also observed. Desmodesmus sp. EJ 9-2 had a wide pH adaptation range (3-12) and could remove nitrogen, phosphorus and COD which might substantially decrease the cost of biofuel production. The research can provide evidence for outdoor large-scale cultivation of microalgae. Keywords: microalgae, isolation, growth restriction, alkaline wastewater, nutrient removal, algae-based fuel, wastewater treatment DOI: 10.3965/j.ijabe.20150806.2164 Citation: Ji F, Wang Y K, Li G, Zhou Y G, Dong R J. Isolation of microalgae with growth restriction and nutrient removal from alkaline wastewater. Int J Agric & Biol Eng, 2015; 8(6): 62－68.

Insights into the plant polysaccharide degradation potential of the xylanolytic yeast Pseudozyma brasiliensis.

In second-generation (2G) bioethanol production, plant cell-wall polysaccharides are broken down to release fermentable sugars. The enzymes of this process are classified as carbohydrate-active enzymes (CAZymes) and contribute substantially to the cost of biofuel production. A novel basidiomycete yeast species, Pseudozyma brasiliensis, was recently discovered. It produces an endo-β-1,4-xylanase with a higher specific activity than other xylanases. This enzyme is essential for the hydrolysis of biomass-derived xylan and has an important role in 2G bioethanol production. In spite of the P. brasiliensis biotechnological potential, there is no information about how it breaks down polysaccharides. For the first time, we characterized the secretome of P. brasiliensis grown on different carbon sources (xylose, xylan, cellobiose and glucose) and also under starvation conditions. The growth and consumption of each carbohydrate and the activity of the CAZymes of culture supernatants were analyzed. The CAZymes found in its secretomes, validated by enzymatic assays, have the potential to hydrolyze xylan, mannan, cellobiose and other polysaccharides. The data show that this yeast is a potential source of hydrolases, which can be used for biomass saccharification.

The Fall of Oil Prices and the Effects on Biofuels

This analysis is focused on the effect of the abrupt decline of oil prices on biofuels, particularly second-generation ethanol. The efforts to decrease the production costs of biofuels, especially cellulosic ethanol (CE), will be greatly threatened if current oil prices remain low, especially since production is not slowing. Only huge state subsidies could alleviate this threat, but the challenge is to persuade citizens that this sacrifice is worthwhile.

Biomass transport cost from field to conversion facility when biomass yield density and road network vary with transport radius

Biomass transport cost from field to a conversion facility is a major component of biofuel production cost. Several studies have provided a general framework, independent of location, for maximising cost competitiveness of bioenergy plants. The majority of these studies assume uniform spatial distribution of biomass and road network, independent of the size of the biorefinery. Although this assumption simplifies the theoretical derivation, it may not be suitable for practical cases. We develop a more generic biomass transport model that allows biomass yield density and road network vary with transport radius, and then derive a formula for determining biomass transport cost, which more accurately represents changes in biomass transport cost with conversion plant capacity. The formula can be used to evaluate locations and investment opportunities in large scale biofuel production.

Bacterial production and secretion of water-insoluble fuel compounds from cellulose without the supplementation of cellulases.

Achieving economic biofuel production from cellulosic biomass will require significant cost reductions. Enzymatic degradation of cellulosic biomass and distillation of water-soluble fuel compounds substantially increase the cost of biofuel production. Consolidated bioprocessing is a strategy to circumvent expensive biofuel production steps. Clostridium thermocellum is a promising bacterium for consolidated bioprocessing because it does not require the supplementation of lignocellulose-degrading enzymes. To produce water-insoluble fuel compounds, C. thermocellum was engineered to express a fatty acyl-acyl carrier protein reductase and an aldehyde-deformylating oxygenase from Synechococcus elongatus PCC 7942. Expression of the aldehyde-deformylating oxygenase gene was clearly detected, whereas only slight expression of the fatty acyl-acyl carrier protein reductase gene was detected. Cells expressing the fatty acyl-acyl carrier protein reductase and the aldehyde-deformylating oxygenase accumulated fatty aldehydes (higher alcohol precursors). After cultivation with cellulose, the higher alcohols, decanol and dodecanol, were detected in the organic solvent phase of the culture broth, indicating that the strain secreted the higher alcohols. These results suggest that the engineered C. thermocellum strain, expressing fatty acyl-acyl carrier protein reductase and aldehyde-deformylating oxygenase genes, directly produces and secretes higher alcohols from cellulose without the supplementation of cellulases. The higher alcohols can be collected by phase separation.

Monte Carlo analysis of life cycle energy consumption and greenhouse gas (GHG) emission for biodiesel production from trap grease

Trap grease is an environmental burden and its management has been costly and ineffective. Utilizing trap grease as a feedstock for biodiesel has the potential to reduce the cost of waste removal and biofuel production. This study presents a life cycle analysis to evaluate the energy consumption and greenhouse gas (GHG) emission from the trap grease-to-biodiesel production process. It was shown that utilizing the solids in the trap grease for anaerobic digestion (AD) was crucial in reducing both energy consumption and GHG emissions. Monte Carlo simulation revealed significant variation in both the life cycle energy consumption and GHG emission, which was caused by the uncertainties within several key variables. The result of the sensitivity analysis indicated that trap grease has the potential to be a more energy efficient and low-GHG-emission feedstock under certain conditions, as compared with the current common feedstocks (e.g. soybean and algae).

Consolidated bioprocessing of cellulose to isobutanol using Clostridium thermocellum

Consolidated bioprocessing (CBP) has the potential to reduce biofuel or biochemical production costs by processing cellulose hydrolysis and fermentation simultaneously without the addition of pre-manufactured cellulases. In particular, Clostridium thermocellum is a promising thermophilic CBP host because of its high cellulose decomposition rate. Here we report the engineering of C. thermocellum to produce isobutanol. Metabolic engineering for isobutanol production in C. thermocellum is hampered by enzyme toxicity during cloning, time-consuming pathway engineering procedures, and slow turnaround in production tests. In this work, we first cloned essential isobutanol pathway genes under different promoters to create various plasmid constructs in Escherichia coli. Then, these constructs were transformed and tested in C. thermocellum. Among these engineered strains, the best isobutanol producer was selected and the production conditions were optimized. We confirmed the expression of the overexpressed genes by their mRNA quantities. We also determined that both the native ketoisovalerate oxidoreductase (KOR) and the heterologous ketoisovalerate decarboxylase (KIVD) expressed were responsible for isobutanol production. We further found that the plasmid was integrated into the chromosome by single crossover. The resulting strain was stable without antibiotic selection pressure. This strain produced 5.4g/L of isobutanol from cellulose in minimal medium at 50oC within 75h, corresponding to 41% of theoretical yield.

Cell Wall Engineering by Heterologous Expression of Cell Wall-Degrading Enzymes for Better Conversion of Lignocellulosic Biomass into Biofuels

Huge energy demand with increasing population is addressing renewable and sustainable energy sources. A solution to energy demand problem is to replace our current fossil fuel-based economy with alternative strategies that do not emit carbon dioxide. Plant biomass is one of the best candidates for this issue. Plants use solar power to convert carbon dioxide and water into sugars, which can be used in fermentation reactions to produce both energy and materials. However, the desired sugars are trapped in the highly recalcitrant cell wall as building blocks of cellulose chains. Moreover, the complexity of the plant cell wall structure hinders the hydrolysis of cellulose into fermentable sugar monomers. Although pretreatments are used to change the physical and chemical properties of the lignocellulosic biomass and improve hydrolysis rates, these pretreatments often use harsh and polluting chemicals and severely increase the cost of biofuel production. The goal of the review is to summarize recent researches, which describe generating plants with a modified cell wall and improve hydrolysis of cellulose without applying any or less pretreatment methods. Since pretreatment of lignocellulosic biomass is the most cost effective step in biofuel production, generating autodigestible plants could reduce the production cost of biofuels and bio-based biomaterials. One of the strategies to improve biomass conversion efficiency is the modification of the cell wall by heterologous expression of cell wall-modifying proteins. These cell wall-modifying proteins could alter the cell wall structure and reduce cell wall recalcitrance. The use of such transgenic technologies would consume less energy and chemicals when cellulose is more accessible for enzymatic hydrolysis.

Integration of next-generation biofuel production in the Swedish forest industry – A geographically explicit approach

The geographic locations of biofuel production facilities should be strategically chosen in order to minimise the total cost of using biofuels. Proximity to biomass resources, possibilities for integration, and distance to biofuel users are aspects that need to be considered. In this paper, the geographically explicit optimisation model BeWhere Sweden was used to investigate the future production of next-generation biofuels from forest biomass in Sweden. A focus was placed on the integration of biofuel production with the existing forest industry, as well as on how different parameters affect biofuel production costs, the choice of technologies and biofuels, and the localisation of new biofuel plants. Six examples of different biofuel routes were considered. A methodology was developed considering detailed, site-specific conditions for potential host industries. The results show that the cost of biomass and the biofuel plant capital cost generally dominate the biofuel cost, but the cost for biomass transportation and biofuel distribution can also have a significant impact. DME produced via black liquor gasification (naturally integrated with chemical pulp mills) and SNG produced via solid biomass gasification (mainly integrated with sawmills), dominate the solutions. The distribution of these technology cases varies depending on a number of parameters, including criteria for sizing biofuel plants, the electricity price, the biofuel distribution cost and the cost of biomass, and is sensitive to changes in these parameters. Generally, plants with low specific investment costs (i.e., high biofuel production) and/or plants with low specific biomass transportation costs occur most frequently in the solutions. Because these properties often vary significantly among biofuel production facilities at different host industry sites of the same type, the results show the advantage of including site-specific data in this type of model. (C) 2015 Elsevier Ltd. All rights reserved.

Modeling the Effect of pH and Temperature for Cellulases Immobilized on Enzymogel Nanoparticles.

Production costs of cellulosic biofuels can be lowered if cellulases are recovered and reused using particulate carriers that can be extracted after biomass hydrolysis. Such enzyme recovery was recently demonstrated using enzymogel nanoparticles with grafted polymer brushes loaded with cellulases. In this work, cellulase (NS50013) and β-glucosidase (Novozyme 188) were immobilized on enzymogels made of poly(acrylic acid) polymer brushes grafted to the surface of silica nanoparticles. Response surface methodology was used to model effects of pH and temperature on hydrolysis and recovery of free and attached enzymes. Hydrolysis yields using both enzymogels and free cellulase and β-glucosidase were highest at the maximum temperature tested, 50°C. The optimal pH for cellulase enzymogels and free enzyme was 5.0 and 4.4, respectively, while both free β-glucosidase and enzymogels had an optimal pH near 4.4. Highest hydrolysis sugar concentrations with cellulase and β-glucosidase enzymogels were 69 and 53% of those with free enzymes, respectively. Enzyme recovery using enzymogels decreased with increasing pH, but cellulase recovery remained greater than 88% throughout the operating range of pH values less than 5.0 and was greater than 95% at pH values below 4.3. Recovery of β-glucosidase enzymogels was not affected by temperature and had little impact on cellulase recovery.

Biomass feedstock preprocessing and long‐distance transportation logistics

AbstractBiomass‐based biofuels have gained attention because they are renewable energy sources that could facilitate energy independence and improve rural economic development. As biomass supply and biofuel demand areas are generally not geographically contiguous, the design of an efficient and effective biomass supply chain from biomass provision to biofuel distribution is critical to facilitate large‐scale biofuel development. This study compared the costs of supplying biomass using three alternative biomass preprocessing and densification technologies (pelletizing, briquetting, and grinding) and two alternative transportation modes (trucking and rail) for the design of a four‐stage biomass–biofuel supply chain in which biomass produced in Illinois is used to meet biofuel demands in either California or Illinois. The BioScope optimization model was applied to evaluate a four‐stage biomass–biofuel supply chain that includes biomass supply, centralized storage and preprocessing (CSP), biorefinery, and ethanol distribution. We examined the cost of 15 scenarios that included a combination of three biomass preprocessing technologies and five supply chain configurations. The findings suggested that the transportation costs for biomass would generally follow the pattern of coal transportation. Converting biomass to ethanol locally and shipping ethanol over long distances is most economical, similar to the existing grain‐based biofuel system. For the Illinois–California supply chain, moving ethanol is $0.24 gal−1 less costly than moving biomass even in densified form over long distances. The use of biomass pellets leads to lower overall costs of biofuel production for long‐distance transportation but to higher costs if used for short‐distance movement due to its high capital and processing costs. Supported by the supply chain optimization modeling, the cellulosic‐ethanol production and distribution costs of using Illinois feedstock to meet California demand are $0.08 gal−1 higher than that for meeting local Illinois demand.