The effect of calcium additives on the fast pyrolysis of switchgrass was studied by continuously pyrolyzing physical mixtures of the biomass with Ca(OH)2, CaO, and Ca(COOH)2 in a laboratory scale ...fluidized bed reactor. Initial tests were performed by cofeeding 220 g/h of switchgrass with Ca(OH)2 at ratios of 0.4/1 and 0.8/1 Ca(OH)2/biomass, running at reactor temperatures of 500, 550, and 600 °C, and using nitrogen or recycled pyrolysis gas as the carrier gas. In comparison with control experiments (Ca-free, biomass only), cofeeding Ca(OH)2 led to a decrease in the yield of both organic phase bio-oil and organic compounds solubilized in the aqueous phase, while noncondensable gas yields were increased. The bio-oils exhibited a reduced oxygen content, a lower concentration of highly oxygenated compounds such as acetic acid and levoglucosan, and a small increase in the concentration of phenols and hydrocarbons. When higher Ca/biomass ratios or higher temperatures were tested, bio-oil yields were further reduced while the bio-oil deoxygenation rate was only slightly higher. The input calcium salts were converted to CaCO3 because of a net trapping of CO2, promoting deoxygenation. Experiments with both N2 and recycled pyrolysis gases as the carrier gas were performed to observe the effect of the changing atmosphere. The use of recycled pyrolysis gases led to increased bio-oil yields at temperatures of 500 and 550 °C, but a lower bio-oil yield at 600 °C for processing with Ca(OH)2. Organic phase bio-oil carbon yields were 10.4, 17.4, 15.2, and 22.8% from biomass for Ca(OH)2, CaO, Ca(COOH)2, and the Ca-free control experiment, respectively, with oxygen contents of 21, 20, 19, and 29.7 wt % at 550 °C (600 °C for Ca-free control). The conversion of the input calcium salt to CaCO3 followed the pattern of Ca(OH)2 > Ca(COOH)2 > CaO, suggesting that bio-oil deoxygenation might not be only related to net CO2 trapping as CaCO3, but also to the catalytic activity of Ca2+.
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•Microalgae biomass is a promising source of third-generation of biofuels.•Versatility of microalgae carbohydrates for biotechnological applications.•Microalgal carbohydrate ...metabolism can be shifted to increase carbohydrate content.•Integration of processes will led microalgae-based carbohydrates to be feasible.
Microalgae contribute significantly to the global carbon cycle through photosynthesis. Given their ability to efficiently convert solar energy and atmospheric carbon dioxide into chemical compounds, such as carbohydrates, and generate oxygen during the process, microalgae represent an excellent and feasible carbohydrate bioresource. Microalgae-based biofuels are technically viable and, delineate a green and innovative field of opportunity for bioenergy exploitation. Microalgal polysaccharides are one of the most versatile groups for biotechnological applications and its content can be increased by manipulating cultivation conditions. Microalgal carbohydrates can be used to produce a variety of biofuels, including bioethanol, biobutanol, biomethane, and biohydrogen. This review provides an overview of microalgal carbohydrates, focusing on their use as feedstock for biofuel production, highlighting the carbohydrate metabolism and approaches for their enhancement. Moreover, biofuels produced from microalgal carbohydrate are showed, in addition to a new bibliometric study of current literature on microalgal carbohydrates and their use.
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•Present status on generation of different forms of bioenergy.•Bioenergy policy initiatives undertaken by various federal agencies of countries.•Feedstock utilization, blending ...targets, and policy assistance schemes assessed.•Current bioenergy market scenario analysis.
Over the last few decades, the globe has much relied on fossil fuels; however, environmental concerns forced the World to look at biofuel as an alternative for stable economic development. Biofuel also facilitates national energy security maintenance and reduces environmental complications. The present study is focused on an in-depth analysis of bioenergy policy measures undertaken by various federal agencies of different countries in order to shed light on the bottlenecks that impede biofuel's growth as a sustainable and alternative fuel. An in-depth assessment of feedstock utilization, blending targets, and policy assistance schemes have been thoroughly reviewed. In addition, the potential of commercial firms for the production of bioenergy is highlighted in order to grasp the current bioenergy market scenario better. Finally, the article is concluded with the viewpoints of the authors to address the standing issues of global bioenergy generation.
Rising demand for energy resources alongside climate emergency concerns has attracted the urgent attention of researchers towards the preparation and utilization of biofuels. This review will ...investigate the different generations of biofuels and more particularly, the developmental and production processes for creating liquid biofuels. Initially, the first-generation biofuel was dependent on edible resources, which has caused controversy and arguments on whether to fulfil the “food or fuel requirement” for civilization. Second-generation biofuels employed inedible resources, however, the cost of production at a commercial scale has restricted its expansion. Recently, third and fourth-generation use microorganisms and genetically modified microorganisms, respectively, to produce biofuels and create an efficient synthetic fuel switch route. Although the last two generations are still in the developmental phase, thorough research is required before commercial-scale production. In conclusion, this review has found that first- and second-generation biofuel production approaches will soon be inadequate to satisfy the exponentially rising demand for biofuels. Therefore, substantial research efforts currently and in the future should focus on the production of third and fourth-generation biofuels, especially on engineered microorganisms. Ultimately, the structure of this review is to outline the current state of the art research regarding biofuels, their production processes and limitations/challenges. This was done through critically reviewing the most up-to-date literature and utilizing bibliometric analysis tools to put forward the guidelines for the future routes of the four generations of biofuels.
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•Biofuels have a significant responsibility in meeting the global energy requirements.•Fourth generations still need developmental before its commercial-scale production.•Large-scale biofuel production is urgent and entirely achievable to meet energy needs.•Thermochemical conversion processes heavily outweigh physical one to produce biofuel.
The ancient phylum
Actinobacteria
is composed of phylogenetically and physiologically diverse bacteria that help Earth's ecosystems function. As free-living organisms and symbionts of herbivorous ...animals,
Actinobacteria
contribute to the global carbon cycle through the breakdown of plant biomass. In addition, they mediate community dynamics as producers of small molecules with diverse biological activities. Together, the evolution of high cellulolytic ability and diverse chemistry, shaped by their ecological roles in nature, make
Actinobacteria
a promising group for the bioenergy industry. Specifically, their enzymes can contribute to industrial-scale breakdown of cellulosic plant biomass into simple sugars that can then be converted into biofuels. Furthermore, harnessing their ability to biosynthesize a range of small molecules has potential for the production of specialty biofuels.
•Improvement of biochemical components using combined abiotic stress.•Microalgae and their properties vis-à-vis biofuel production.•Transformation of all potential biochemical components into ...biofuels.
Microalgal biomass has received much attention as feedstock for biofuel production due to its capacity to accumulate a substantial amount of biocomponents (including lipid, carbohydrate, and protein), high growth rate, and environmental benefit. However, commercial realization of microalgal biofuel is a challenge due to its low biomass production and insufficient technology for complete utilization of biomass. Recently, advanced strategies have been explored to overcome the challenges of conventional approaches and to achieve maximum possible outcomes in terms of growth. These strategies include a combination of stress factors; co-culturing with other microorganisms; and addition of salts, flue gases, and phytohormones. This review summarizes the recent progress in the application of single and combined abiotic stress conditions to stimulate microalgal growth and its biocomponents. An innovative schematic model is presented of the biomass-energy conversion pathway that proposes the transformation of all potential biocomponents of microalgae into biofuels.
Land Availability for Biofuel Production Cai, Ximing; Zhang, Xiao; Wang, Dingbao
Environmental science & technology,
01/2011, Volume:
45, Issue:
1
Journal Article
Peer reviewed
Marginal agricultural land is estimated for biofuel production in Africa, China, Europe, India, South America, and the continental United States, which have major agricultural production capacities. ...These countries/regions can have 320−702 million hectares of land available if only abandoned and degraded cropland and mixed crop and vegetation land, which are usually of low quality, are accounted. If grassland, savanna, and shrubland with marginal productivity are considered for planting low-input high-diversity (LIHD) mixtures of native perennials as energy crops, the total land availability can increase from 1107−1411 million hectares, depending on if the pasture land is discounted. Planting the second generation of biofuel feedstocks on abandoned and degraded cropland and LIHD perennials on grassland with marginal productivity may fulfill 26−55% of the current world liquid fuel consumption, without affecting the use of land with regular productivity for conventional crops and without affecting the current pasture land. Under the various land use scenarios, Africa may have more than one-third, and Africa and Brazil, together, may have more than half of the total land available for biofuel production. These estimations are based on physical conditions such as soil productivity, land slope, and climate.
► Cyanobacteria/microalgae are non-food based feedstock resources. ► Cyanobacteria/microalgae can use non-productive land and water sources. ► Cyanobacterial/microalgal biofuels do not lead to loss ...of ecosystems. ► Biofuel research must find economically sound use of co-products. ► Modifications in cyanobacteria can lead to higher biofuel production.
Biofuel–bioenergy production has generated intensive interest due to increased concern regarding limited petroleum-based fuel supplies and their contribution to atmospheric CO2 levels. Biofuel research is not just a matter of finding the right type of biomass and converting it to fuel, but it must also be economically sustainable on large-scale. Several aspects of cyanobacteria and microalgae such as oxygenic photosynthesis, high per-acre productivity, non-food based feedstock, growth on non-productive and non-arable land, utilization of wide variety of water sources (fresh, brackish, seawater and wastewater) and production of valuable co-products along with biofuels have combined to capture the interest of researchers and entrepreneurs. Currently, worldwide biofuels mainly in focus include biohydrogen, bioethanol, biodiesel and biogas. This review focuses on cultivation and harvesting of cyanobacteria and microalgae, possible biofuels and co-products, challenges for cyanobacterial and microalgal biofuels and the approaches of genetic engineering and modifications to increase biofuel production.
Maternal exposure to particulate matter derived from diesel exhaust has been shown to cause metabolic dysregulation, neurological problems, and increased susceptibility to diabetes in the offspring. ...Diesel exhaust is a major source of air pollution and the use of biodiesel (BD) and its blends have been progressively increasing throughout the world; however, studies on the health impact of BD vs. petrodiesel combustion-generated exhaust have been controversial in part, due to differences in the chemical and physical nature of the associated particulate matter (PM). To explore the long-term impact of prenatal exposure, pregnant mice were exposed to PM generated by combustion of petrodiesel (B0) and a 20% soy BD blend (B20) by intratracheal instillation during embryonic days 9-17 and allowed to deliver. Offspring were then followed for 52 weeks. We found that mother's exposure to B0 and B20 PM manifested in striking sex-specific phenotypes with respect to metabolic adaptation, maintenance of glucose homeostasis, and medial hypothalamic glial cell makeup in the offspring. The data suggest PM exposure limited to a narrower critical developmental window may be compensated for by the mother and/or the fetus by altered metabolic programming in a marked sex-specific and fuel-derived PM-specific manner, leading to sex-specific risk for diseases related to environmental exposure later in life.
•Microalgal biomass solubilisation was enhanced by low temperature pretreatment.•Pretreatment at 55–95°C for 10h improved the methane production rate and yield.•The energy balance of the pretreatment ...step showed the need for microalgae thickening.
The aim of this study was to investigate the effect of low temperature pretreatment on the anaerobic digestion of microalgal biomass grown in wastewater. To this end, microalgae were pretreated at low temperatures (55, 75 and 95°C) for 5, 10 and 15h. Biomass solubilisation was enhanced with the pretreatment temperature and exposure time up to 10h. The methane yield was improved by 14%, 53% and 62% at 55, 75 and 95°C, respectively; and was correlated with the solubilisation increase. The pretreatment at 95°C for 10h increased VS solubilisation by 1188%, the initial methane production rate by 90% and final methane yield by 60% compared to untreated microalgae. With diluted biomass (∼1% VS) positive energy balance was not likely to be attained. However, with concentrated biomass (>2% VS) energy requirements may be covered and even surplus energy generated.
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