Low-cost Biofuel Research Articles

Potential of Microalgae Cultivation in Dairy Wastewater as a Step in Low-Cost Biofuel Production

The present study addresses adopting the organic and nutritious materials in dairy wastewater as media for cultivation of microalgae, which represent an important source of renewable energy. This study was carried out through cultivation of three types of microalgae; Chlorella sp., Synechococcus, and Anabaena. The results shows the success the cultivation of the Synechococcus and Chlorella Sp, while the Anabaena microalgae were in low-growth level. The highest growth was in the Synechococcus farm, followed by Chlorella and Anabaena. However, the growth of Synechococcus required 10 days to achieve this increase that represents a negative indicator of the adoption of this type of microalgae in this media to meet the desired aims. While Chlorella needs less than two days to start growing. Moreover, the data obtained from the experiment show that removal of chemical oxygen demand in Chlorella cultures was (72%) more than that obtained from cultivation of other microalgae. Thus this microalgae is more efficient in wastewater treatment than other types.

A new source of resistance to 2-furaldehyde from Scheffersomyces (Pichia) stipitis for sustainable lignocellulose-to-biofuel conversion

Aldehyde inhibitory compounds derived from lignocellulosic biomass pretreatment have been identified as a major class of toxic chemicals that interfere with microbial growth and subsequent fermentation for advanced biofuel production. Development of robust next-generation biocatalyst is a key for a low-cost biofuel production industry. Scheffersomyces (Pichia) stipitis is a naturally occurring C-5 sugar utilization yeast; however, little is known about the genetic background underlying its potential tolerance to biomass conversion inhibitors. We investigated and identified five uncharacterized putative aryl-alcohol dehydrogenase genes (SsAADs) from this yeast as a new source of resistance against biomass fermentation inhibitor 2-furaldehyde (furfural) by gene expression, gene cloning, and direct enzyme assay analysis using partially purified proteins. All five proteins from S. stipitis showed furfural reduction using cofactor NADH. An optimum active temperature was observed at 40°C for SsAad1p; 30°C for SsAad3p, SsAad4p, and SsAad5p; and 20°C for SsAad2p. SsAad2p, SsAad3p, and SsAad4p showed tolerance to a wide range of pH from 4.5 to 8, but SsAad1p and SsAad5p were sensitive to pH changes beyond 7. Genes SsAAD2, SsAAD3, and SsAAD4 displayed significantly enhanced higher levels of expression in response to the challenge of furfural. Their encoding proteins also showed higher levels of specific activity toward furfural and were suggested as core functional enzymes contributing aldehyde resistance in S. stipitis.

Aspects of carbon dioxide mitigation in a closed microalgae photo-bioreactor supplied with flue gas

The aim of the present study is to investigate the potential of flue gases to be efficiently and economically applied in production of algal biomass in a photobioreactor (PBR). Various microalgae strains (Chlorella sorokiniana 211-234, Bracteacoccus minor 61.80, Radiosphaera negevensis 87.80, Chlorosarcinopsis negevensis 67.80 and Chlorococcum novae-angliae 5.85) had been tested for CO2 mitigation, growth and tolerance to high CO2 levels. The flue gas and CO2 bubbling induced a significant algal mass growth compared to control (ambient air). Removal of CO2 and NO by the studied microalgae strains was found to be 44% and 33% along daily intervals, respectively. A growth rate of ~0.4g L−1 d−1 was obtained for all algal species tested. Growth conditions for tested algae can be optimised through PBR technology in order to obtain highest biomass yield for production of valuable biochemicals (i.e., low-cost biofuel).

Aspects of carbon dioxide mitigation in a closed microalgae photo-bioreactor supplied with flue gas

The aim of the present study is to investigate the potential of flue gases to be efficiently and economically applied in production of algal biomass in a photobioreactor (PBR). Various microalgae strains (Chlorella sorokiniana 211-234, Bracteacoccus minor 61.80, Radiosphaera negevensis 87.80, Chlorosarcinopsis negevensis 67.80 and Chlorococcum novae-angliae 5.85) had been tested for CO2 mitigation, growth and tolerance to high CO2 levels. The flue gas and CO2 bubbling induced a significant algal mass growth compared to control (ambient air). Removal of CO2 and NO by the studied microalgae strains was found to be 44% and 33% along daily intervals, respectively. A growth rate of ~0.4g L−1 d−1 was obtained for all algal species tested. Growth conditions for tested algae can be optimised through PBR technology in order to obtain highest biomass yield for production of valuable biochemicals (i.e., low-cost biofuel).

Potential of five different isolated colonial algal species for wastewater treatment and biomass energy production

Wastewater treatment high rate algal pond (WWT HRAP) performance and the potential for low-cost biofuel production from its biomass are affected by the composition of the algal community. While several unicellular algal species have been evaluated extensively for their wastewater treatment and biofuel production potential, there has been little focus on the colonial species that typically predominate in high rate algal ponds and which have the benefit of being easily harvested by cost-effective, simple gravity settling. This study investigates the wastewater treatment performance of five wastewater colonial algal species that are common in high rate algal ponds: Mucidosphaerium pulchellum, Micractinium pusillum, Coleastrum sp., Desmodesmus sp. and Pediastrum boryanum and their potential value for biofuel production in terms of their biochemical composition and biomass energy yield. The algae were isolated from pilot-scale WWT HRAPs and used in batch monoculture experiments with pre-frozen and pre-filtered primary settled sewage that were conducted over 10days under simulated New Zealand summer and winter conditions. Under summer conditions, all species showed similar efficient nutrient removal (>95% of NH4+-N and >85% of PO43−-P within 4days) whereas, under winter conditions, only the Mucidosphaerium pulchellum and Micractinium pusillum cultures showed efficient nutrient removal by the end of the experiment. Algal biomass yield, lipid and energy content varied with species and were higher in summer than winter (respectively 991–1700mg/L, 14.4–48.2wt% and 19.1–25kJ/g in summer, and 158.7–584mg/l, 15.1–31.4wt% and 17.7–21.1kJ/g in winter). The Mucidosphaerium pulchellum and Micractinium pusillum cultures had the highest biomass yield, lipid and energy content under both summer and winter conditions. However the settleability of Micractinium pusillum is much better than Mucidosphaerium pulchellum suggesting that of the colonial algal species tested, Micractinium pusillum has the greatest potential for both wastewater treatment and low-cost energy production in WWT HRAP.

Public perception of bioenergy in North Carolina and Tennessee

The goal of the study is to examine the general public’s understanding and perceptions of bioenergy and biofuels in North Carolina (NC) and Tennessee (TN). The study focuses on the public concerns, support and risk evaluations of alternative bioenergy feedstocks and biofuels, and includes an assessment of the economic, environmental, social, and policy impacts of bioenergy production and use. A sample of consumers in NC and TN were surveyed in the fall of 2013 and spring of 2014 for their perceptions about bioenergy and specifically, biofuels for transportation. Five hundred eighty-six consumers completed the questionnaire electronically (376 in NC and 210 in TN). Respondents reported that the price and vehicle compatibility with biomass-based transportation fuels were the most important factors in their choice of biofuels over gasoline at a pump. Results show that the acceptance of bioenergy depends on the extent of knowledge and available information to consumers about the energy source. A principal component analysis (PCA) indicated seven distinct dimensions of consumer’s perception about bioenergy. The key dimensions are the following: how bioenergy benefits the society, risks of bioenergy use, government support for bioenergy, increase in food cost, conditional use of trees, support for low-cost biofuel alternative to current energy, and market attributes of bioenergy purchase. The findings from this study reflect the need for communicating the benefits and risks from the use of bioenergy to the general public through trustworthy channels of communication and targeted policy, market, and institutional support.

Diverse roles of glycine-rich RNA-binding protein 7 in the response of camelina (Camelina sativa) to abiotic stress

Camelina sativa L. is an oilseed crop used as a potential low-cost biofuel resource. Despite the economic and agricultural benefits of this crop, studies demonstrating the physiological and genetic response of camelina to changing environmental conditions are limited. In this study, three stress-responsive glycine-rich RNA-binding proteins (GRPs) in camelina—named CsGRP7a, CsGRP7b, and CsGRP7c—were isolated, and their functional roles in stress responses were characterized. The three CsGRP7 genes had similar nucleotide and deduced amino acid sequences, and contained an N-terminal RNA-recognition motif and a C-terminal glycine-rich region. The CsGRP7 genes were ubiquitously expressed in all plant tissues, and CsGRP7 proteins were localized to both the cytoplasm and the nucleus. The expression of CsGRP7 genes was markedly upregulated by cold stress, whereas their expression was only slightly affected by salt or dehydration stress. Analysis of CsGRP7a-expressing transgenic Arabidopsis thaliana and camelina plants revealed that CsGRP7a plays a positive role in cold stress tolerance, but a negative role in salt or drought stress tolerance. All three CsGRP7s harbored RNA chaperone activity. Collectively, these data indicate that the stress-responsive CsGRP7s harbor RNA chaperone activity and play different roles in the plant response to abiotic stresses.

Direct Production of Butanol and Ethanol from Cane Sugar Factory Wastewater and Cellulosic Ethanol Pilot Plant Wastewater by Clostridium Beijerinckii CG1

The ability of Clostridium beijerinckii CG1 to utilize sugar from cane sugar factory wastewater (CSFW) and cellulosic ethanol pilot plant wastewater (CEPW) as a renewable carbon source and complete fermentation medium to produce acetone-butanol-ethanol (ABE) was investigated. CSFW and CEPW were used as the unsupplemented culture media (50mL) for ABE production by C. beijerenckii CG1 fermentation in 100-mL serum bottles. No acetone was produced from fermentation of either CEPW or CSFW, in contrast to the small amount (20g L-1) produced from glucose in the last 24h of a 120h fermentation. The average ethanol, butanol and butyric acid production from CEPW (butanol 0.6g L-1, ethanol 0.4g L-1 and butyric acid 2.5g L-1) was higher than that from CSFW (butanol 0.3g L-1, ethanol 0.3g L-1 and butyric acid 0.9g L-1), but still less than that from glucose (butanol 1.87g L-1, ethanol 0.86g L-1 and butyric acid 6.47g L-1). However, the productivity rate in this 50-mL fermentation was three-fold higher with CSFW (0.06g L-1 h-1) than with CEPW (0.02g L-1 h-1). These results suggest that CSFW and CEPW can be applied as appropriate substrates to produce solvents by C. beijerinckii CG1 at a reasonable concentration without the need for additional exogenous nutrient supplements or pretreatment. The idea then being to consolidate the bioprocess for low-cost biofuel production.

Lignin-enriched Fermentation Residues from Bioethanol Production of Fast-growing Poplar and Forage Sorghum

The current challenges in developing a cost-effective bioethanol industry include the production of not only high-volume, low cost biofuels but also high-value products with minimal downstream waste. The up-grading of side-stream lignins from bioethanol production plants to novel high-value products will improve the profitability of the bioethanol industry; to do that, a precise understanding of lignin is required. In the present study, lignin-enriched fermentation residues from bioethanol production (steam explosion pretreatment, saccharification, and fermentation) of fast-growing poplar and forage sorghum were characterized. In addition to the purity and composition, lignin structure (syringyl/guaiacyl (S/G) ratio, inter-unit linkages) was also analyzed with spectroscopy techniques such as Fourier transform infrared and two-dimensional nuclear magnetic resonance. Bioethanol processing and feedstock origins seemed to be the main factors determining the purity, composition, and structure of lignins. Residual lignins from poplar and forage sorghum contained significant amounts of sugar and protein impurities. Poplar lignin showed a very high S/G ratio associated with p-hydroxybenzoate. A lower S/G ratio together with H lignin units and p-hydroxycinnamates (p-coumarate and ferulate) was observed for forage sorghum lignin. The main inter-unit linkages present in both lignins were β-O-4´ aryl ether followed by resinols and phenylcoumarans.

Capability of different microalgae species for phytoremediation processes: Wastewater tertiary treatment, CO2 bio-fixation and low cost biofuels production

Scenedesmus obliquus, Chlorella vulgaris, Chlorella kessleri and a natural Bloom were cultivated in batch experiments, under controlled conditions, in urban wastewater (WW) and synthetic wastewater (SW) under 5% CO2 in air, with the object of estimating their capacity for nutrient removal, carbon dioxide biofixation, and generation of valuable biomass. In both culture media, the Bloom (Bl) and Scenedesmus (Sc) showed higher final biomass concentration (dried weight, dw) than the other species; the maximum yield obtained was 1950 ± 243 mg L−1 for Bl and the minimum 821 ± 88 mg L−1 for Cv, both in synthetic wastewater. Maximum specific growth rate values do not show significant differences between any of the 4 strains tested (p ≤ 0.05), nor between the 2 culture media. A new homogeneous method of calculating productivities has been proposed. Nitrogen removal in all the reactors was higher than 90%, except for BlSW (79%), and for phosphorus, the removal was higher than 98% in all trials. Maximum CO2 consumption rates reached were 424.4 and 436.7 mg L−1 d−1 for ScSW and ScWW respectively.

Engineering Escherichia coli for Biodiesel Production Utilizing a Bacterial Fatty Acid Methyltransferase

The production of low-cost biofuels in engineered microorganisms is of great interest due to the continual increase in the world's energy demands. Biodiesel is a renewable fuel that can potentially be produced in microbes cost-effectively. Fatty acid methyl esters (FAMEs) are a common component of biodiesel and can be synthesized from either triacylglycerol or free fatty acids (FFAs). Here we report the identification of a novel bacterial fatty acid methyltransferase (FAMT) that catalyzes the formation of FAMEs and 3-hydroxyl fatty acid methyl esters (3-OH-FAMEs) from the respective free acids and S-adenosylmethionine (AdoMet). FAMT exhibits a higher specificity toward 3-hydroxy free fatty acids (3-OH-FFAs) than FFAs, synthesizing 3-hydroxy fatty acid methyl esters (3-OH-FAMEs) in vivo. We have also identified bacterial members of the fatty acyl-acyl carrier protein (ACP) thioesterase (FAT) enzyme family with distinct acyl chain specificities. These bacterial FATs exhibit increased specificity toward 3-hydroxyacyl-ACP, generating 3-OH-FFAs, which can subsequently be utilized by FAMTs to produce 3-OH-FAMEs. PhaG (3-hydroxyacyl ACP:coenzyme A [CoA] transacylase) constitutes an alternative route to 3-OH-FFA synthesis; the coexpression of PhaG with FAMT led to the highest level of accumulation of 3-OH-FAMEs and FAMEs. The availability of AdoMet, the second substrate for FAMT, is an important factor regulating the amount of methyl esters produced by bacterial cells. Our results indicate that the deletion of the global methionine regulator metJ and the overexpression of methionine adenosyltransferase result in increased methyl ester synthesis.

Simpler Is Better: High-Yield and Potential Low-Cost Biofuels Production through Cell-Free Synthetic Pathway Biotransformation (SyPaB)

The production of biofuels from renewable sugars isolated from plants or produced through artificial photosynthesis would provide a sustainable transportation fuel alternative for decreasing reliance on crude oil, mitigating greenhouse gas emissions, creating new manufacturing jobs, and enhancing national energy security. Since sugar costs usually account for at least 50% of biofuels’ selling prices, it is vital to produce desired biofuels with high product yields and at low production costs. Here I suggest high-product yield and potentially low-cost biofuels production through cell-free synthetic enzymatic pathway biotransformation (SyPaB) by in vitro assembly of stable enzymes and (biomimetic) coenzymes. SyPaB can achieve high product yields or high energy efficiencies that living entities cannot achieve. Great potentials of SyPaB, from chiral compounds, biodegradable sugar batteries, sulfur-free jet fuel, hydrogen, sugar hydrogen fuel cell vehicles, high-density electricity storage, to synthetic starch...

Generation of transgenic plants of a potential oilseed crop Camelina sativa by Agrobacterium-mediated transformation

Camelina sativa is an alternative oilseed crop that can be used as a potential low-cost biofuel crop or a source of health promoting omega-3 fatty acids. Currently, the fatty acid composition of camelina does not uniquely fit any particular uses, thus limit its commercial value and large-scale production. In order to improve oil quality and other agronomic characters, we have developed an efficient and simple in planta method to generate transgenic camelina plants. The method included Agrobacterium-mediated inoculation of plants at early flowering stage along with a vacuum infiltration procedure. We used a fluorescent protein (DsRed) as a visual selection marker, which allowed us to conveniently screen mature transgenic seeds from a large number of untransformed seeds. Using this method, over 1% of transgenic seeds can be obtained. Genetic analysis revealed that most of transgenic plants contain a single copy of transgene. In addition, we also demonstrated that transgenic camelina seeds produced novel hydroxy fatty acids by transforming a castor fatty acid hydroxylase. In conclusion, our results provide a rapid means to genetically improve agronomic characters of camelina, including fatty acid profiles of its seed oils. Camelina may serve as a potential industrial crop to produce novel biotechnology products.

Implementing the climate change convention: taxes or tradable abatement obligations equals coercion or negotiation

Technological change external to the energy supply industry – sink enhancement and demand side efficiency improvements – is key to a least–cost greenhouse gas response strategy. The potential for a low cost global forestry and biofuel based response is noted. Enlisting energy supply firms' expertise to manage such technology change entails the use of policy instruments congenial to managerial involvement. Tradable abatement obligations (equivalent to uniform voluntary agreements and to a dedicated carbon tax) provide a greater incentive to external technological change than do conventional economic instruments (carbon taxes and tradable emissions permits). A process of negotiated transition from voluntary agreements to tradable abatement obligations is described and aspects of the long run policy regime discussed.