Environmental aspects of biofuels in road transportation

Energy is a vital and growing need for human activities such as transport, agriculture and industry. The transport and agriculture sectors are major consumers of fossil fuel. However, availability of fossil fuels is limited. The use of fossil fuels is of increasing environmental concerns because it produces toxic airborne particulates and greenhouse gases such as CO₂. The increasing industrialization and motorization of the world led to a steep rise for the demand of petroleum-based fuels. Hence, it is necessary to seek alternative fuels, which can be produced from resources available locally within the country such as alcohol, biodiesel and vegetable oils. Biodiesel is defined as the mono alkyl esters of vegetable oils or animal fats. Biodiesel is the best candidate for diesel fuels in the diesel engines. The advantage of biodiesel over gasoline and petroleum/diesel is its eco-friendly nature. This article reviews the production, characterization and current status of biofuels mainly biodiesel along with the environmental impacts of particulate matter, greenhouse gas emissions originated from biodiesel.     

Cobalt-based catalysts for hydrogen production by thermochemical valorization of glycerol: a review

Environmental Chemistry Letters - Rising energy needs and the exhaustion of fossil fuels are calling for renewable fuels such as dihydrogen (H2), commonly named 'hydrogen.' Biomass...     

Is there really a green paradox?

In the absence of a CO₂ tax, the anticipation of a cheaper renewable backstop increases current emissions of CO₂. Since the date at which renewables are phased in is brought forward and more generally future emissions of CO₂ will decrease, the effect on global warming is unclear. Green welfare falls if the backstop is relatively expensive and full exhaustion of fossil fuels is optimal, but may increase if the backstop is sufficiently cheap relative to the cost of extracting the last drop of fossil fuels plus marginal global warming damages as then it is attractive to leave more fossil fuels unexploited and thus limit CO₂ emissions. We establish these results by analyzing depletion of non-renewable fossil fuels followed by a switch to a clean renewable backstop, paying attention to timing of the switch and the amount of fossil fuels remaining unexploited. We also discuss the potential for limit pricing when the non-renewable resource is owned by a monopolist. Finally, we show that if backstops are already used and more backstops become economically viable as the price of fossil fuels rises, a lower cost of the backstop will either postpone fossil fuel exhaustion or leave more fossil fuel in situ, thus boosting green welfare. However, if a market economy does not internalize global warming externalities and renewables have not kicked in yet, full exhaustion of fossil fuel will occur in finite time and a backstop subsidy always curbs green welfare.     

Is there really a green paradox?

In the absence of a CO₂ tax, the anticipation of a cheaper renewable backstop increases current emissions of CO₂. Since the date at which renewables are phased in is brought forward and more generally future emissions of CO₂ will decrease, the effect on global warming is unclear. Green welfare falls if the backstop is relatively expensive and full exhaustion of fossil fuels is optimal, but may increase if the backstop is sufficiently cheap relative to the cost of extracting the last drop of fossil fuels plus marginal global warming damages as then it is attractive to leave more fossil fuels unexploited and thus limit CO₂ emissions. We establish these results by analyzing depletion of non-renewable fossil fuels followed by a switch to a clean renewable backstop, paying attention to timing of the switch and the amount of fossil fuels remaining unexploited. We also discuss the potential for limit pricing when the non-renewable resource is owned by a monopolist. Finally, we show that if backstops are already used and more backstops become economically viable as the price of fossil fuels rises, a lower cost of the backstop will either postpone fossil fuel exhaustion or leave more fossil fuel in situ, thus boosting green welfare. However, if a market economy does not internalize global warming externalities and renewables have not kicked in yet, full exhaustion of fossil fuel will occur in finite time and a backstop subsidy always curbs green welfare.     

Auf der Suche nach den Treibstoffen der Zukunft

The climatically-relevant emission of CO₂ which results from motor vehicle traffic offers a challenge for the automobile industry to produce highly efficient and economical motor vehicles. Furthermore, the production of fuels from regenerative energies may provide a more significant contribution over the long-term to make our mobility more compatible to the climate and to reduce our dependence on crude oil importation. Substantial reductions in emissions can be achieved through the application of regenerative fuels, especially in combination with more energy-efficient hybrid or fuel-cell vehicles, or through the addition of biogenic components to conventional fuels. Coordinated efforts between the automobile industry, the energy industries and the responsible politicians are mandatory in order to achieve ecologically-tolerable motor vehicle traffic.     

Substitution between biofuels and fossil fuels: Is there a green paradox?

We show that (i) subsidies for renewable energy policies with the intention of encouraging substitution away from fossil fuels may accentuate climate change damages by hastening fossil fuel extraction, and that (ii) the opposite result holds under some specified conditions. We focus on the case of subsidies for renewable resources produced under increasing marginal costs, and assume that both the renewable resources and the fossil fuels are currently in use. Such subsidies have a direct effect and an indirect effect working in opposite directions. The direct effect is the reduction in demand for fossil fuels at any given price. The indirect effect is the reduction in the current equilibrium price for fossil fuels, which tends to increase the amount of fossil fuels demanded. Whether the sum of the two effects will actually result in an earlier or later date of exhaustion of the stock of fossil fuels depends on the curvature of the demand curve for energy and of the supply curve for the renewable substitute.     

Substitution between biofuels and fossil fuels: Is there a green paradox?

We show that (i) subsidies for renewable energy policies with the intention of encouraging substitution away from fossil fuels may accentuate climate change damages by hastening fossil fuel extraction, and that (ii) the opposite result holds under some specified conditions. We focus on the case of subsidies for renewable resources produced under increasing marginal costs, and assume that both the renewable resources and the fossil fuels are currently in use. Such subsidies have a direct effect and an indirect effect working in opposite directions. The direct effect is the reduction in demand for fossil fuels at any given price. The indirect effect is the reduction in the current equilibrium price for fossil fuels, which tends to increase the amount of fossil fuels demanded. Whether the sum of the two effects will actually result in an earlier or later date of exhaustion of the stock of fossil fuels depends on the curvature of the demand curve for energy and of the supply curve for the renewable substitute.     

美国汽车清洁燃料研究发展

本文简要介绍了美国汽车清洁燃料和汽油替代燃料的研究和发展状况，内容涉及美国政府对发展汽车清洁燃料的战略、政策、立法和有关发展计划，清洁燃料的类型和种类及应用情况，以及存在的主要问题和未来的发展方向。     

Does pyrogenicity protect burning plants?

Pyrogenic plants dominate many fire-prone ecosystems. Their prevalence suggests some advantage to their enhanced flammability, but researchers have had difficulty tying pyrogenicity to individual-level advantages. Based on our review, we propose that enhanced flammability in fire-prone ecosystems should protect the belowground organs and nearby propagules of certain individual plants during fires. We base this hypothesis on five points: (1) organs and propagules by which many fire-adapted plants survive fires are vulnerable to elevated soil temperatures during fires; (2) the degree to which burning plant fuels heat the soil depends mainly on residence times of fires and on fuel location relative to the soil; (3) fires and fire effects are locally heterogeneous, meaning that individual plants can affect local soil heating via their fuels; (4) how a plant burns can thus affect its fitness; and (5) in many cases, natural selection in fire-prone habitats should therefore favor plants that burn rapidly and retain fuels off the ground. We predict an advantage of enhanced flammability for plants whose fuels influence local fire characteristics and whose regenerative tissues or propagules are affected by local variation in fires. Our "pyrogenicity as protection" hypothesis has the potential to apply to a range of life histories. We discuss implications for ecological and evolutionary theory and suggest considerations for testing the hypothesis.     

The solar transformity of petroleum fuels

Petroleum fuels are the primary energy basis for transportation and industry. They are almost always an important input to the economic and social activities of humanity. Emergy analyses require accurate estimates with specified uncertainty for the transformities of major energy and material inputs to economic and environmental systems. In this study, the oil refining processes in Italy and the United States were examined to estimate the transformity and specific emergy of petroleum derivatives. Based on our assumptions that petroleum derivatives are splits of a complex hydrocarbon mixture and that the emergy is split based on the fraction of energy in a product, we estimated that the transformity of petroleum derivatives is 65,826 sej/J ± 1.4% relative to the 9.26E+24 sej/year planetary baseline. Estimates of the specific emergies of the various liquid fuels from Italian and U.S. refineries are within 2% of one another and the relationship of particular values varies with the refinery design. Our average transformity is only 1.7% larger than the current estimate for petroleum fuels determined by back calculation, confirming the accuracy of this transformity in existing emergy analyses. The model uncertainty between using energy or mass to determine how emergy is split was less that 2% in the estimate of both the transformity and specific emergy of liquid fuels, but larger for solid and gaseous products. This study is a contribution to strengthen the emergy methodology, providing data that can be useful in the analysis of many human activities.     

Biofuels and Biodiversity: Principles for Creating Better Policies for Biofuel Production

Abstract:  Biofuels are a new priority in efforts to reduce dependence on fossil fuels; nevertheless, the rapid increase in production of biofuel feedstock may threaten biodiversity. There are general principles that should be used in developing guidelines for certifying biodiversity-friendly biofuels. First, biofuel feedstocks should be grown with environmentally safe and biodiversity-friendly agricultural practices. The sustainability of any biofuel feedstock depends on good growing practices and sound environmental practices throughout the fuel-production life cycle. Second, the ecological footprint of a biofuel, in terms of the land area needed to grow sufficient quantities of the feedstock, should be minimized. The best alternatives appear to be fuels of the future, especially fuels derived from microalgae. Third, biofuels that can sequester carbon or that have a negative or zero carbon balance when viewed over the entire production life cycle should be given high priority. Corn-based ethanol is the worst among the alternatives that are available at present, although this is the biofuel that is most advanced for commercial production in the United States. We urge aggressive pursuit of alternatives to corn as a biofuel feedstock. Conservation biologists can significantly broaden and deepen efforts to develop sustainable fuels by playing active roles in pursuing research on biodiversity-friendly biofuel production practices and by helping define biodiversity-friendly biofuel certification standards.     

Chlorinated dioxins and furans as trace products of combustion: Some theoretical aspects

Recent advances in combustion theories are reviewed, especially the detailed mechanisms of hydrocarbon oxidation, formation of polynuclear aromatic hydrocarbon from aliphatic fuels, and the behavior of halogens in flames. Experimental observations of polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/F) formation in combustion of aliphatic fuels such as acetylene, ethylene and methane in the presence of hydrogen chloride are summarized. Then, from combustion chemistry considerations a reaction mechanism for T₄CDD/F formation in the CH₄/ HCl/O₂ system is developed. This mechanism consists of elementary reactions describing the main oxidation steps, formation of chlorinated C₁‐ to C₄‐species, formation of the first aromatic ring, and T₄CDD/F formation. The mechanism may be extended to other hydrocarbon fuels and higher PCDD/F homologues. Possible relevance of the mechanism to the “trace chemistries of fire hypothesis”; is discussed.     

Tiefentschwefelte Kraftstoffe

In recent years, much attention has been given to the desulphurization of fuels like diesel oil and gasoline, since exhaust gases containing SOx cause air pollution and acid rain. Moreover, a lower sulphur content of fuels would allow the use of new engines and catalytic systems for the reduction of CO, particle and NOx-emissions, and a more efficient fuel consumption. The S-level in fuels is presently limited in Germany for gasoline and diesel oll to 150 ppm and 350 ppm, respectively. In 2005 the level will be decreased Europe-wide for all vehicle-fuels down to 50 ppm; in some countries, fuels are or will be on the market with even less sulphur. The current technology of hydrodesulphurization (heterogeneous, catalyzed hydrorreating of organic sulphur compounds) can desulphurize quite adequately down to today’s S-level. The process, however, is limited for the production of ultra-low sulphur fuels, and the expenses (pressure, reactor size, investment costs, energy consumption, specific active catalysts) are high to meet future requirements. alternative processes, which are not limited to hydrotreating, are therefore desirable. Beside an overview about hydrotreating, this paper presents two quite different alternatives: Extraction of sulphur compounds by ionic liquids and the synthetic production of S-free fuels from natural gas by Fischer-Tropsch-synthesis. Ionic liquids (ILs) are low melting (<100°C) salts which represent a new class of non-molecular, ionic solvents. In the experiments presented, extraction of model diesel oils (dibenzothiophene and dodecanthiol in n-dodecane) as well as of a real predesulphurized diesel oil (with about 400 ppm S) were investigated. The results show the excellent and selective extraction properties of ILs for organic sulphur compounds, especially with regard to those compounds which are very difficult to remove by common hydrodesulphurization. As expected, the desulphurization by extraction is much more complicated in case of real diesel oil (compared to a model oil) due to its complex chemical composition including many different sulphur compounds and other impurities like organic nitrogen and metal-compounds. Nevertheless, the results with pre-desulphurized diesel oil are also very promising. So, extraction of sulphur components by ILs is a new approach for deep desulphurization of diesel oil. The application of very mild process conditions (low pressure and temperature) in comparison to traditional hydrotreating is an additional advantage of this new concept. An alternative to today’s fuels based on crude oil is the production of gasoline and diesel oil from natural gas (or other fossil fuels like coal) by Fischer-Tropsch-synthesis (FTS). The products like diesel oil are completely free of sulphur and other impurities like nitrogen and metal compounds. Although several FTS-processes have been investigated and developed, and some processes are already running on a technical scale, a real breakthrough was not obtained up to now. The production costs of these capital-intensive processes are probably above the breakeven point, at least at today’s oil price. In this paper, a ‘lowcost’ process is discussed, which is based on nitrogen-rich syngas. In contrast to classical FTS-processes with nitrogen-free syngas, the investment costs are probably lower: The syngas is produced by partial oxidation with ait, which eliminates the need of an air separation plant, while a process with nitrogen-rich syngas does not utilize a recycle loop and a recycle compressor.     

Lignin and polylactic acid for the production of bioplastics and valuable chemicals

Environmental Chemistry Letters - Global warming and plastic pollution result from the massive use of fossil fuels, calling for the development of&nbsp;sustainable&nbsp;bioplastics derived...     

Brown backstops versus the green paradox

Anticipated climate policies are ineffective when fossil fuel owners respond by shifting supply intertemporally (the green paradox). This mechanism relies crucially on the exhaustibility of fossil fuels. We analyze the effect of anticipated climate policies on emissions in a simple model with two fossil fuels: one scarce and dirty (e.g. oil), the other abundant and dirtier (e.g. coal). We derive conditions for a ‘green orthodox’: anticipated climate policies may reduce current emissions. The model can also be used to analyze spatial carbon leakage. Calibrations suggest that intertemporal carbon leakage (from 0% to 8%) is a relatively minor concern.     

Photoelectrochemical technology for solar fuel generation,from single photoelectrodes to unassisted cells: a review

Environmental Chemistry Letters - Photoelectrochemical solar fuel generation requires a highly integrated technology for converting solar energy into chemical fuels. Dihydrogen (H2)&nbsp;and...     

汽车燃料和排放物的快速气相色谱分析

1　IntroductionGaschromatographyisthemostfrequentlyusedmethodsforthespeciationandquantificationoforganiccompoundsingasphaseandliquidphase .Thechemicalanalysisoforganiccompoundsintheautomotivefuelsandexhaustspeciesisanextremelyimportantandcomplexprocedure …     

Conversion of plant materials into hydroxymethylfurfural using ionic liquids

The use of fossil fuels now induces two major issues. First, fossil fuel burning is increasing atmospheric carbon dioxide (CO₂) concentrations and, in turn, global warming. Second, fossil fuel resources are limited and will thus decrease in the long run. As a potential solution, there is a need for ecological manufacturing processes that convert raw plant materials into chemical products. For instance, raw plants can be directly converted into hydroxymethylfurfural, which is a versatile intermediate for the synthesis of valuable biofuels such as dimethylfuran and 5-ethoxymethyl-2-furfural. This technology has two benefits for chemical sustainability. First, the pretreatment step is eliminated, thus contributing to reduction of CO₂ emissions. Second, plants are sustainable resources versus fossil fuels, which are limited. Here, we review current sustainable technologies for the production of biobased products and hydroxymethylfurfural from plants, using in particular ionic liquids. Plant sources include poplar, switchgrass, miscanthus, weed plants, and agave species.     

Assessing geobiosphere work of generating global reserves of coal, crude oil, and natural gas

A teacher of ours used to say, “Like ice in a fire, something for nothing you will never acquire”, which is a poetic equivalent of “there is no such a thing as a free lunch”. Human economies are dependent on high quality fossil fuels and will likely continue depending on them for some time to come. Value of a resource is not only what one pays for it, or what can be extracted from it, but also value can be attributed to the “effort” required in its production. In this analysis we apply the emergy synthesis method to evaluate the work invested by the geobiosphere to generate the global storages of fossil energy resources. The upgrading of raw resources to secondary fuels is also evaluated. The analysis relies on published estimates of historic, global net primary production (NPP) on land and oceans, published preservation and conversion factors of organic matter, and assessments of the present total global storages of coal, petroleum, and natural gas. Results show that the production of coal resources over geologic time required between 6.63E4 (±0.51E4) seJ/J and 9.71E4 (±0.79E4) seJ/J, while, oil and natural gas resources required about 1.48E5 (±0.07 E5) seJ/J and 1.70E5 (±0.06E5) seJ/J, respectively. These values are between 1.5 and 2.5 times larger than previous estimates and acknowledge a far greater power of fossil fuels in driving and shaping modern society.