Fourth Generation Biofuel Research Articles

Biofuels an alternative to traditional fossil fuels: A comprehensive review

Biofuels are fossil fuel alternatives produced from agricultural biomass or other organic matter; considered sustainable, eco-friendly, and bioeconomic biofuels have come up as a topic of discussion for over a decade. Their practical use depends on the production methods, low cost-technology implementation, and substrate used. This review gives an insight into different generations of biofuels with their applications and implications. First-generation biofuels are produced from edible biomass, but even in highly efficient processes, their yield isn't enough to cast them as a better alternative to conventional fuels. The second-generation biofuels are produced from non-edible biomass, where the substrate is eco-friendly and provides a sustainable use of solid waste, but the pretreatment is overpriced and sophisticated technology is needed to carry out the process. Third-generation biofuels are produced from substrates like seaweed or microalgae for which no specific area or separate cultivation process is required. Biofuels such as biohydrogen produced through microbial dark fermentation, bio-syngas generated via gasification, and biodiesel obtained through transesterification, have emerged as promising and environmentally friendly alternatives to conventional fuels. These biofuels have the potential to pave the way for a bioeconomic system of fuel production, offering economic viability and efficiency. However, extensive research conducted in the field of bioenergy, several challenges persist, hindering their commercialization prospects. To overcome the problems of first, second and third-generation biofuels, fourth-generation biofuels are under development using techniques like co-culturing, nanotechnology, and genetically modified organisms. Future generations of biofuels would set a system for a circular bioeconomic pathway for sustainable development in the fuel industry.

A semi-continuous algal-bacterial wastewater treatment process coupled with bioethanol production

Harnessing the biomass energy potential through biofuel production offers new outlets for a circular economy. In this study an integrated system which combine brewery wastewater treatment using algal-bacterial aggregates instead of activated sludge was developed. The use of algal-bacterial aggregates can eliminate the aeration requirements and significantly reduce the high biomass harvesting costs associated with algal monocultures. A sequencing batch reactor (SBR) setup operating with and without biomass recirculation was used to investigate pollutant removal rates, aggregation capacity and microbial community characteristics under a range of hydraulic retention times (HRTs) and solid retention times (SRTs). It was observed that biomass recirculation strategy significantly enhanced aggregation and pollutant removal (i.e., 78.7%, 94.2% and 75.2% for d-COD, TKN, and PO43--P, respectively). The microbial community established was highly diverse consisting of 161 Bacterial Operational Taxonomic Units (B-OTUs) and 16 unicellular Eukaryotic OTUs (E-OTUs). Escalation the optimal conditions (i.e., HRT = 4 d, SRT = 10 d) at pilot-scale resulted in nutrient starvation leading to 38–44% w/w carbohydrate accumulation. The harvested biomass was converted to bioethanol after acid hydrolysis followed by fermentation with Saccharomyces cerevisiae achieving a bioethanol production yield of 0.076 g bioethanol/g biomass. These data suggest that bioethanol production coupled with high-performance wastewater treatment using algal-bacterial aggregates is feasible, albeit less productive concerning bioethanol yields than systems exclusively designed for third and fourth-generation biofuel production.

Three Pillars of Advanced Biofuels’ Sustainability

Today, reducing GHG emissions is an important goal worldwide. Initially, first-generation biofuels were considered as a solution; however, they created a conflict between food and fuel. Advanced biofuels, which use non-edible materials, have emerged and are becoming more widespread, thus resolving this conflict. The paper aimed to investigate the three pillars of advanced biofuels’ sustainability (economic, environmental, and social). In the frame of a systematic literature review, 41 out of the initially screened 3407 articles were analyzed in depth. The economic aspect of sustainability was the most frequently occurring topic, followed by the environmental aspect, while the number of articles related to the social aspect was limited. From the economic point of view, all the analyzed articles agreed that advanced biofuels are far from commercialization at this stage; however, there are promising options related to different feedstocks or production technologies. Advanced biofuels perform unequivocally better environmentally than even conventional biofuels. For third-generation biofuels, negative net GHG emissions can even be possible, while fourth-generation biofuels can theoretically be produced from CO2. With respect to the social pillar, job creation was the core element of the articles analyzed. This can be experienced at the farm, production, and research levels. Although the commercialization of advanced biofuel production will take time, humanity must turn to them in order to avoid the food versus fuel problem, as well as to successfully fight against climate change and global warming.

Suitability of Biofuels Production on Commercial Scale from Various Feedstocks: A Critical Review

AbstractThe growing demand for energy resources and the increase in greenhouse gas (GHG) emissions has given biofuels a lot of attention. Liquid biofuels can be a significant alternative for the transport sector. Generally, biofuels are categorized into four generations based on the feedstock. This review reports the availability, economic feasibility, and potential of biofuel feedstock in global scenario. Feedstock for first‐generation biofuel comprises edible resources impacting the food supply. Second generation biofuels are based on different residual materials and nonedible fuel crops. Cost and technological limitations for commercialization hinders this option. Microalgae are the feedstock for third generation biofuels providing the highest yield compared to the other two generations. A scale‐up to commercial level is not possible as this requires further development. Genetically modified microorganisms are used as a feedstock for fourth generation biofuel production with the highest possible yield. Third and fourth generation biofuels have potential to replace fossil fuels. This review recommends certain suggestions for sustainable biofuel production.

Recent evolutionary trends in the production of biofuels

Substitutes for fossil fuels or petroleum-based diesel have comparable addresses to monoalkyl fatty acid esters or methyl ethyl esters (biodiesel) and might lessen carbon footprint and greenhouse gas emissions. Biodiesel may be made from renewable and sustainable ingredients consisting of vegetable oils and non-poisonous to the ecosystem. The manufacturing of biodiesel with renewable feedstocks and enzymes as catalysts can be supported commercially; however, studies into enhancing performance may be beneficial. Biodiesel gives a sustainable possibility to address the socio-economic and sustainable fuel problems. For competitive biodiesel, massive studies have been focused on growing new and sustainable biodiesel manufacturing technology to enhance productivity. Recently, fourth-generation biofuels (FGBs), genetically modified (GM) algae biomass, have attracted much interest from educational and business communities. However, changing FGBs with mineral assets stays fraught with many demanding situations. In particular, the technical elements of genetic engineering features want to be specified. However, little or no interest has been paid to GM algae biomass. Algal Genetics has a restricted quantity of development views and demanding situations dealing with FGBs. The fourth-generation biofuel concentrates on improving the microorganisms genetically. Although, in the primitive grade, the last two generations of biofuel require genetic change for the more like-suited in yielding a high-quality amount of green diesel. The aim is to define four generations with the most recent developments. This paper consists of the current production strategies of biofuel and the improvement efforts significant for third and fourth generations, mainly a genetic exchange of algae or bacterial strains and co-cultivation of several microorganisms.

An overview of biofuel power generation on policies and finance environment, applied biofuels, device and performance

The prices of fossil fuels, the gap between energy supply and demand, energy security, environmental issues, and the reduction of greenhouse gas emissions commonly promote the development of biomass power generation in China. Compared to direct biomass combustion power generation and biogas power generation, liquid biofuel power generation has better application potential. Policies and finance environment of countries and organizations have promoted the extensive application of biofuel power generation in recent years, especially in China. Evaluation of internal combustion engine, gas turbine and fuel cell on the stationary power station and mobile generation shows that gas turbine is the main generator-set, the fuel cell is the fastest-growing and future generator-set, while the engine is the first choice in transport and low power generation field. As the second, third and fourth generation biofuels, biomethanol, bioethanol, biodiesel and others have been researched and widely used in power generation. In addition, power generation performance and emissions have been improved to some extent after biofuels supplying. For the future, combined heat and power (CHP) generation and integrated gasification combined cycle (IGCC) is imperative development trends of power generation for higher energy and exergy efficiency. CHP based on the various generating facilities will be the next choice and direction of energy use trends for transport.

A critical perspective on the scope of interdisciplinary approaches used in fourth-generation biofuel production

The use of algae in biofuel production is more sustainable as compared to crop-based resources as it doesn't compromise food security, rainforests, or arable land. Furthermore, the utilization of molecular biology methods such as CRISPR/Cas9 with guided RNA for genetic modification in algae has opened up new avenues to meet the future energy demand. Recently, a progressive shift in the paradigm of algal growth from an open system (raceways) to a closed system (e.g.; PBRs) has been observed because the latter is more efficient in biofuel production as it provides optimized growth conditions. Several algal species have been genetically engineered and characterized for different parameters, especially their ability to grow in a closed system. Since the advent of the closed system viz. fermenters for industrial applications, several advancements have been made in its design and functions to optimize the growth of industrially used microbial strains and the yield of their bio-products. Genetically engineered algae have diverse growth condition requirements varying even at strain levels, consequently, an enormous amount of significant information or data is available on the optimization of algal growth conditions in PBRs. In conjunction with different computational biological approaches, the high throughput analysis of data becomes fast, enabling to predict the scale-up production process and capital cost and investment requirements. Systematic and planned, altogether applications of genetic engineering, PBRs, and computational approaches should not only help to make the production of fourth-generation biofuels more convenient but also pave the way of different interdisciplinary approaches to be used in algal biofuel production processes in near future.

Developing fourth-generation biofuels secreting microbial cell factories for enhanced productivity and efficient product recovery; a review

Fourth generation (4G) biofuels have been found compatible with engines, storage systems, and transport facilities. Due to advances in synthetic biology and genetic engineering tools, considerable progress has been made in producing 4G biofuels including high-carbon alcohols, long-chain hydrocarbons, terpenoids-based, and/or fatty-acid derived biofuels using Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, Yarrowia lypolytica, and Zymomonas mobilis as microbial cellular factories. However, these microbial platforms face various challenges including low product titers, low product yields, difficult product recovery incurring intensive energy consumption, and discharge of large amounts of wastewater. All these issues make the production and recovery of these biofuels expensive and commercially non-competitive. However, various genetic manipulation approaches including overexpression of heat-shock proteins, enhanced production of precursor molecules, regulating redox-balance, and membrane engineering have been employed to cope with these challenges. This review discusses the progress made in the molecular approaches for the enhanced biosynthesis and easier recovery of these biofuels through employing the secreting microbial cell factories. Besides, based on the data published on membrane transporters in previous fifteen years, selected fungal and bacterial membrane efflux pumps are studied to evaluate their biofuel secretion potential as future targets to be employed in the biofuel secreting microbial cell factories to achieve commercial robustness in the future.

Biodiesel and green diesel generation: an overview

First, second, third, and fourth-generation biofuels are continuously evolving as a promising substitute to petrodiesel catalyzed by energy depletion, economic and environmental considerations. Bio-diesel can be synthesized from various biomass sources, which are commonly divided into FAME and renewable biodiesel. FAME biodiesel is generally produced by the transesterification of vegetable oils and fats while renewable diesel is produced by hydro-deoxygenation of vegetable and waste oils and fats. The different generation, processing technologies and standards for FAME and renewable biodiesel are reviewed. Finally, the life cycle analysis and production cost of conventional and renewable biodiesel are described.

Cyanobacteria as an eco-friendly resource for biofuel production: A critical review.

Cyanobacteria are photosynthetic microorganisms which can be found in various environmental habitats. These photosynthetic bacteria are considered as promising feedstock for the production of the third- and the fourth-generation biofuels. The main subject of this review is highlighting the significant aspects of the biofuel production from cyanobacteria. The most recent investigations about the extraction or separation of the bio-oil from cyanobacteria are also adduced in the present review. Moreover, the genetic engineering of cyanobacteria for improving biofuel production and the impact of bioinformatics studies on the designing better-engineered strains are mentioned. The large-scale biofuel production is challenging, so the economic considerations to provide inexpensive biofuels are also cited. It seems that the future of biofuels is strongly dependent to the following items; understanding the metabolic pathways of the cyanobacterial species, progression in the construction of the engineered cyanobacteria, and inexpensive large-scale cultivation of them.

BIOLOGICAL ASPECTS OF ANAEROBIC DIGESTION AND ITS KINETICS: AN OVERVIEW

Anaerobic digestion is an anoxic microbiological process occurring in natural environments. Though, the process is considered to be the oldest, its concept relies on the fourth generation biofuel for direct sequestration of carbon-di-oxide into methane. However, the process is successful in natural environments in the efficiency of methane yield with compared to pilot or industrial scale. An overview of an anaerobic digestion and its kinetics is detailed in this review for the successful digestion process, which includes microbiological process, methanogenic interactions, operational conditions of the digester, substrate requirements and its limitation, substrate enhancement by pretreatment and co-digestion process and other rate limiting parameters affecting the process in order to increase the efficiency of methane production.

Incidence of using chickenfat basedbiodiesel on the performance of a 13.5kW compression ignition piston enginefor power generation

New alternatives and feedstocks have been identified to overcome the impact caused by combustion of fossil fuels; some of them point on the promotion of second, third and fourth generation biofuels resulting from non-edible crops and other raw materials. The lack of information about the performance of engines used for power generation encumbers the use of chicken fat biodiesel in gensets in rural areas or other applications in which power generation is the main purpose. Therefore, this work aims to identify the incidence of using chicken fat biodiesel on the performance of a 13.45kWe internal combustion engine employed for power generation. The biodiesel was synthesized in lab conditions and afterwards fueled in the engine. Parameters such as the total electrical efficiency, heat rate, fuel consumption and the exhaust gas emissions are analyzed. A Lister TR2 diesel engine fixed to a Leroy Soner LSA 38 M/J electrical generator was employed. The chicken fat biodiesel was successfully produced in a lab-scale facility and afterward employed as biofuel blended with commercial biodiesel BPa7. The efficiency of the genset increases up to 38.79% with B22.5 higher than the 35.08% obtained for B0. As a consequence of the fuel reduction and addition of a sustainable biofuel such as chicken-fat biodiesel the carbon footprint was also decreased; the CO2 released decreases about 2.9 kgCO2h-1 when the genset was operating at full capacity fueled with B22.5

Overexpression of NAC gene from Lepidium latifolium L. enhances biomass, shortens life cycle and induces cold stress tolerance in tobacco: potential for engineering fourth generation biofuel crops.

We report elevated biomass and altered growth characteristics of tobacco plants up on transformation with a NAC (NAM, ATAF1/2,CUC2) gene (GenBank Accession FJ754254) isolated from Lepidium latifolium L. (LlaNAC). Transgenic plants showed significant differences in fresh weight, midrib length of longest leaf, leaf area, height of the plant, root and shoot weights, etc. during vegetative phase. On 100th day after sowing (DAS), plants of transgenic lines were 2-3 times taller than the wild type plants, though no significant difference was recorded in moisture contents of any of the plant tissues. Over-expression of NAC gene up to 2,000 fold was recorded in leaves of transgenic plants on 100th DAS. Interestingly, transgenic plants showed significantly shortened (P(t)=0.02-0.04) life cycle, as they showed a completely altered growth behaviour. Transgenic plants entered reproductive phase earlier by 60days, with lines NC2 and NC7b entering first, followed by line NC10. However, the time period spent in the reproductive phase by the plant was nearly twice in case of transgenic lines NC2, NC7b and NC10, as compared to the wild type plants. Despite that, these lines completed their life cycle in 45-60days lesser than the time taken by wild-type tobacco plants. No difference was recorded in fruit and seed yield of transgenic or wild type plants. To the best of our knowledge, this is the first report on over-expression of NAC gene causing altered growth and biomass patterns. We expect this study to become an important reference towards future engineering of plants for fuel and fodder purposes.

Biofuels and CO2 neutrality: an opportunity

CO2-neutral bioprocesses are of immanent concern and can be coupled by using integrated bioprocess and biofuel production systems. Existing biofuel generations are, therefore, reclassified according to the current possible bioprocessing routes. Only the first biofuel generation has been successfully carried into a commercial scale, while the second is still being improved at laboratory scale or in pilot-scale processes. Biodiesel and biohydrogen, as third- and fourth-generation biofuels, respectively, are also being studied at the laboratory scale. Here, we introduce the fifth biofuel generation, which is based on biological CH4 production from gaseous raw materials. The integration of bioprocess systems and the coupling between different biofuel generations under CO2 neutrality is analyzed and presented to be of great interest for industry and science. Value-added production (i.e., recombinant proteins) can be coupled to CO2-neutral integrated biofuel production systems and, hence, integration of different biofuel generations within a biorefinery concept could be translated into a reality.

Formate Formation and Formate Conversion in Biological Fuels Production

Biomethanation is a mature technology for fuel production. Fourth generation biofuels research will focus on sequestering CO2 and providing carbon-neutral or carbon-negative strategies to cope with dwindling fossil fuel supplies and environmental impact. Formate is an important intermediate in the methanogenic breakdown of complex organic material and serves as an important precursor for biological fuels production in the form of methane, hydrogen, and potentially methanol. Formate is produced by either CoA-dependent cleavage of pyruvate or enzymatic reduction of CO2 in an NADH- or ferredoxin-dependent manner. Formate is consumed through oxidation to CO2 and H2 or can be further reduced via the Wood-Ljungdahl pathway for carbon fixation or industrially for the production of methanol. Here, we review the enzymes involved in the interconversion of formate and discuss potential applications for biofuels production.

Metabolic engineering of algae for fourth generation biofuels production

The ecological footprint and economic performance of the current suite of biofuel production methods make them insufficient to displace fossil fuels and reduce their impact on the inventory of Green House Gas (GHG) in the global atmosphere. Algae metabolic engineering forms the basis for 4th generation biofuel production which can meet this need. The first generation biofuels are known to be made from agricultural products such as corn or sugarcane. The second generation biofuels use all forms of (lingo)cellulosic biomass. The third and fourth generation of biofuel production involves “algae-to-biofuels” technology: the former is basically processing of algae biomass for biofuel production, while the latter is about metabolic engineering of algae for producing biofuels from oxygenic photosynthetic microorganisms. Our review focuses on the research achievement of metabolic engineering of algae for biofuel production. It is concluded that 4th generation biofuel production has introduced the “cell factory” concept in this field, and shifted the research paradigm. There still exists several technical bottlenecks in algae biofuel research and development, which can only be solved by the use of post-genome tools on these photosynthetic organisms.