231 research outputs found
Photobiological hydrogen production and artificial photosynthesis for clean energy: from bio to nanotechnologies
No full textGlobal energy demand is increasing rapidly and
due to intensive consumption of different forms of fuels,
there are increasing concerns over the reduction in readily
available conventional energy resources. Because of the
deleterious atmospheric effects of fossil fuels and the
uncertainties of future energy supplies, there is a surge of
interest to find environmentally friendly alternative energy
sources. Hydrogen (H2) has attracted worldwide attention
as a secondary energy carrier, since it is the lightest carbonneutral
fuel rich in energy per unit mass and easy to store.
Several methods and technologies have been developed for
H2 production, but none of them are able to replace the
traditional combustion fuel used in automobiles so far.
Extensively modified and renovated methods and technologies
are required to introduce H2 as an alternative efficient,
clean, and cost-effective future fuel. Among several
emerging renewable energy technologies, photobiological
H2 production by oxygenic photosynthetic microbes such
as green algae and cyanobacteria or by artificial photosynthesis
has attracted significant interest. In this short
review, we summarize the recent progress and challenges
in H2-based energy production by means of biological and
artificial photosynthesis routes.112151sciescopu
World oil price and biofuels : a general equilibrium analysis
No full textThe price of oil could play a significant role in influencing the expansion of biofuels. However, this issue has not been fully investigated yet in the literature. Using a global computable general equilibrium model, this study analyzes the impact of oil price on biofuel expansion, and subsequently, on food supply. The study shows that a 65 percent increase in oil price in 2020 from the 2009 level would increase the global biofuel penetration to 5.4 percent in 2020 from 2.4 percent in 2009. A doubling of oil price in 2020 from its baseline level, or a 230 percent increase from the 2009 level, would increase the global biofuel penetration in 2020 to 12.6 percent. The penetration of biofuels is highly sensitive to the substitution possibility between biofuels and their fossil fuel counterparts. The study also shows that aggregate agricultural output drops due to an oil price increase, but the drop is small in major biofuel producing countries as the expansion of biofuels would partially offset the negative impacts of the oil price increase on agricultural outputs. An increase in oil price would reduce global food supply through direct impacts as well as through diversion of food commodities and cropland toward the production of biofuels.Energy Production and Transportation,Climate Change Economics,Markets and Market Access,Renewable Energy,Food&Beverage Industry
Impacts of policy instruments to reduce congestion and emissions from urban transportation : the case of Sao Paulo, Brazil
No full textThis study examines impacts on net social benefits or economic welfare of alternative policy instruments for reducing traffic congestion and atmospheric emissions in São Paulo, Brazil. The study shows that expanding road networks, subsidizing public transit, and improving automobile fuel economy may not be as effective as suggested by economic theories because these policies could cause significant rebound effects. Although pricing instruments such as congestion tolls and fuel taxes would certainly reduce congestion and emissions, the optimal level of these instruments would steeply increase the monetary cost of travel per trip and are therefore politically difficult to implement. However, a noticeable finding is that even smaller tolls, which are more likely to be politically acceptable, have substantial benefits in terms of reducing congestion and emissions. Among the various policy instruments examined in the study, the most socially preferable policy option for São Paulo would be to introduce a mix of congestion toll and fuel taxes on automobiles and use the revenues to improve public transit systems.Transport Economics Policy&Planning,Climate Change Economics,Roads&Highways,Climate Change Mitigation and Green House Gases,Transport and Environment
Lock-in effects of road expansion on CO2 emissions : results from a core-periphery model of Beijing
No full textIn the urban planning literature, it is frequently explicitly asserted or strongly implied that ongoing urban sprawl and decentralization can lead to development patterns that are unsustainable in the long run. One manifestation of such an outcome is that if extensive road investments occur, urban sprawl and decentralization are advanced and locked-in, making subsequent investments in public transit less effective in reducing vehicle kilometers traveled by car, gasoline use and carbon dioxide emissions. Using a simple core-periphery model of Beijing, the authors numerically assess this effect. The analysis confirms that improving the transit travel time in Beijing’s core would reduce the city’s overall carbon dioxide emissions, whereas the opposite would be the case if peripheral road capacity were expanded. This effect is robust to perturbations in the model’s calibrated parameters. In particular, the effect persists for a wide range of assumptions about how location choice depends on travel time and a wide range of assumptions about other aspects of consumer preferences.Transport Economics Policy&Planning,Roads&Highways,Energy and Environment,Environment and Energy Efficiency,Economic Theory&Research,Urban Transport
The role of revenue recycling schemes in environmental tax selection : a general equilibrium analysis
No full textThis study examines the roles of revenue recycling schemes for the selection of alternative tax instruments (i.e., carbon-, sulphur-, energy- and output-tax) to reduce CO2 emissions to a specified level in Thailand. A static, single period, multi-sectoral computable general equilibrium (CGE) model of the Thai economy has been developed for this purpose. This study finds that the selection of a tax instrument to reduce CO2 emissions would be significantly influenced by the scheme to recycle the tax revenue to the economy. If the tax revenue is recycled to finance cuts in the existing labour or indirect tax rates, carbon tax would be more efficient than the sulphur-, energy- and output-taxes to reduce CO2 emissions. On the other hand, if the tax revenue is recycled to households through a lump-sum transfer, sulphur and carbon taxes would be more efficient than energy and output taxes. The ranking between the sulphur and carbon taxes under the lump sum transfer scheme depends on substitution possibility of fossil fuels. Sulphur tax is found superior over carbon tax at the higher substitution possibility between fossil fuels; the reverse is found true at the lower substitution possibility. In all schemes of revenue recycling considered, the output tax is found to be the most costly (i.e., in welfare terms) despite the fact that it generates two to three times higher revenue than the other tax instruments.Environmental Economics&Policies,Taxation&Subsidies,Transport Economics Policy&Planning,Energy Production and Transportation,Debt Markets
Under what conditions does a carbon tax on fossil fuels stimulate biofuels ?
No full textA carbon tax is an efficient economic instrument to reduce emissions of carbon dioxide released from fossil fuel burning. Its impacts on production of renewable energy depend on how it is designed -- particularly in the context of the penetration of biofuels into the energy supply mix for road transportation. Using a multi-sector, multi-country computable general equilibrium model, this study shows first that a carbon tax with the entire tax revenue recycled to households through a lump-sum transfer does not stimulate biofuel production significantly, even at relatively high tax rates. This reflects the high cost of carbon dioxide abatement through biofuels substitution, relative to other energy substitution alternatives; in addition, the carbon tax will have negative economy-wide consequences that reduce total demand for all fuels. A combined carbon tax and biofuel subsidy policy, where part of the carbon tax revenue is used to finance a biofuel subsidy, would significantly stimulate market penetration of biofuels. Although the carbon tax and biofuel subsidy policy would cause higher loss in global economic output compared with the carbon tax with lump sum revenue redistribution, the incremental output loss is relatively small.Climate Change Mitigation and Green House Gases,Transport Economics Policy&Planning,Taxation&Subsidies,Environment and Energy Efficiency,Energy and Environment
Advanced biofuel technologies : status and barriers
No full textLarge-scale production of crop based (first generation) biofuels may not be feasible without adversely affecting global food supply or encroaching on other important land uses. Because alternatives to liquid fossil fuels are important to develop in order to address greenhouse gas mitigation and other energy policy objectives, the potential for increased use of advanced (non-crop, second generation) biofuel production technologies has significant policy relevance. This study reviews the current status ofseveral advanced biofuel technologies. Technically, it would be possible to produce a large portion of transportation fuels using advanced biofuel technologies, specifically those that can be grown using a small portion of the world's land area (for example, microalgae), or those grown on arable lands without affecting food supply (for example, agricultural residues). However, serious technical barriers limit the near-term commercial application of advanced biofuels technologies. Key technical barriers include low conversion efficiency from biomass to fuel, limits on supply of key enzymes used in conversion, large energy requirements for operation, and dependence in many cases on commercially unproven technology. Despite a large future potential, large-scale expansion of advanced biofuels technologies is unlikely unless and until further research and development lead to lowering these barriers.Energy Production and Transportation,Climate Change Mitigation and Green House Gases,Renewable Energy,Crops&Crop Management Systems,Sanitation and Sewerage
Why have CO2 emissions increased in the transport sector in Asia ? underlying factors and policy options
No full textRapidly increasing emissions of carbon dioxide from the transport sector, particularly in urban areas, is a major challenge to sustainable development in developing countries. This study analyzes the factors responsible for transport sector CO2 emissions growth in selected developing Asian countries during 1980-2005. The analysis splits the annual emissions growth into components representing economic development; population growth; shifts in transportation modes; and changes in fuel mix, emission coefficients, and transportation energy intensity. The study also reviews existing government policies to limit CO2 emissions growth, particularly various fiscal and regulatory policy instruments. The study finds that of the six factors considered, three - economic development, population growth, and transportation energy intensity - are responsible for driving up transport sector CO2 emissions in Bangladesh, the Philippines, and Vietnam. In contrast, only economic development and population growth are responsible in the case of China, India, Indonesia, Republic of Korea, Malaysia, Pakistan, Sri Lanka, and Thailand. CO2 emissions exhibit a downward trend in Mongolia due to decreasing transportation energy intensity. The study also finds that some existing policy instruments help reduce transport sector CO2 emissions, although they were not necessarily targeted for this purpose when introduced.Transport Economics Policy&Planning,Climate Change Mitigation and Green House Gases,Energy Production and Transportation,Climate Change Economics,Transport and Environment
The growth of transport cector CO2 emissions and underlying factors in Latin America and the Caribbean
No full textThis study examines the factors responsible for the growth of transport sector carbon dioxide emissions in 20 Latin American and Caribbean countries during 1980-2005 by decomposing the emissions growth into components associated with changes in fuel mix, modal shift, and economic growth, as well as changes in emission coefficients and transportation energy intensity. The key finding of the study is that economic growth and the changes in transportation energy intensity are the main factors driving transport sector carbon dioxide emissions growth in the countries considered. The results imply that fiscal policy instruments - such as subsidies to clean fuels and clean vehicles - would be more effective in reducing emissions in countries where the economic activity effect is the primary driver for transport sector carbon dioxide emissions growth. By contrast, regulatory policy instruments - such as vehicle efficiency standards and vehicle occupancy standards - would be more effective in countries where the transportation energy intensity effect is the main driver of carbon dioxide emissions growth. Both fiscal and regulatory policy instruments would be useful in countries where both economic activity and transportation energy intensity effects are responsible for driving transport sector carbon dioxide emissions growth.Transport Economics Policy&Planning,Energy Production and Transportation,Oil Refining&Gas Industry,Environment and Energy Efficiency,Energy and Environment
Urban Road Transportation Externalities: Costs and Choice of Policy Instruments
No full textUrban transportation externalities are a key development challenge. Based on the existing literature, the authors illustrate the magnitudes of various external costs, review response policies, and measure and discuss their selection, particularly focusing on the context of developing countries. They find that regulatory policy instruments aimed at reducing local air pollution have been introduced in most countries in the world. On the other hand, fiscal policy instruments aimed at reducing congestion or greenhouse gas emissions are limited mainly to industrialized economies. Although traditional fiscal instruments, such as fuel taxes and subsidies, are normally introduced for other purposes, they can also help to reduce externalities. Land-use or urban planning, and infrastructure investment, could also contribute to reducing externalities; but they are expensive and play a small role in already developed megacities. The main factors that influence the choice of policy instruments include economic efficiency, equity, country or city specific priority, and institutional capacity for implementation. Multiple policy options need to be used simultaneously to reduce effectively the different externalities arising from urban road transportation because most policy options are not mutually exclusive. Copyright The Author 2010. Published by Oxford University Press on behalf of the International Bank for Reconstruction and Development / <sc>the world bank</sc>. All rights reserved. For permissions, please e-mail: [email protected], Oxford University Press.
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