Sectoral trends in global energy use and greenhouse gas emissions

Integrated assessment models have been used to project both baseline and mitigation greenhouse gas emissions scenarios. Results of these scenarios are typically presented for a number of world regions and end-use sectors, such as industry, transport, and buildings. Analysts interested in particular technologies and policies, however, require more detailed information to understand specific mitigation options in relation to business-as-usual trends. This paper presents sectoral trend for two of the scenarios produced by the Intergovernmental Panel on Climate Change's Special Report on Emissions Scenarios. Global and regional historical trends in energy use and carbon dioxide emissions over the past 30 years are examined and contrasted with projections over the next 30 years. Macro-activity indicators are analyzed as well as trends in sectoral energy and carbon demand. This paper also describes a methodology to calculate primary energy and carbon dioxide emissions at the sector level, accounting for the full energy and emissions due to sectoral activities.     

Policies for improving the efficiency of the Brazilian light-duty vehicle fleet and their implications for fuel use,greenhouse gas emissions and land use

The increase in greenhouse gas concentrations in the atmosphere, energy security issues and competition for land use are putting pressure on governments and policymakers. However, these three subjects are not usually treated in integrated form. This paper shows that the implementation of energy efficiency policies combined with policies to encourage use of biofuels can help reduce greenhouse gases emissions while easing land use competition from sugarcane ethanol in Brazil. By adapting the ADVISOR (Advanced Vehicle Simulator) software to evaluate vehicle efficiency, and by estimating the Brazilian light-duty vehicle market share based on historical data, this paper estimates the possible levels of GHG emissions and area planted with sugarcane in 2030 in the country. The findings indicate that reductions from 8% to 20% in greenhouse gas emissions and 0.9–1.8 million ha in sugarcane planted area are possible with no significant technological breakthroughs over the horizon to 2030 in comparison with a baseline scenario.     

Life-cycle greenhouse gas emissions and energy balances of sugarcane ethanol production in Mexico

The purpose of this work was to estimate GHG emissions and energy balances for the future expansion of sugarcane ethanol fuel production in Mexico with one current and four possible future modalities. We used the life cycle methodology that is recommended by the European Renewable Energy Directive (RED), which distinguished the following five system phases: direct Land Use Change (LUC); crop production; biomass transport to industry; industrial processing; and ethanol transport to admixture plants. Key variables affecting total GHG emissions and fossil energy used in ethanol production were LUC emissions, crop fertilization rates, the proportion of sugarcane areas that are burned to facilitate harvest, fossil fuels used in the industrial phase, and the method for allocation of emissions to co-products. The lower emissions and higher energy ratios that were observed in the present Brazilian case were mainly due to the lesser amount of fertilizers applied, also were due to the shorter distance of sugarcane transport, and to the smaller proportion of sugarcane areas that were burned to facilitate manual harvest. The resulting modality with the lowest emissions of equivalent carbon dioxide (CO_2e) was ethanol produced from direct juice and generating surplus electricity with 36.8 kgCO_2e/GJ_ethanol. This was achieved using bagasse as the only fuel source to satisfy industrial phase needs for electricity and steam. Mexican emissions were higher than those calculated for Brazil (27.5 kgCO_2e/GJ_ethanol) among all modalities. The Mexican modality with the highest ratio of renewable/fossil energy was also ethanol from sugarcane juice generating surplus electricity with 4.8 GJ_ethanol/GJ_fossil.     

An energy development strategy for the USSR Minimizing greenhouse gas emissions

The second largest national consumer of commercial energy in the world, the USSR also emits large quantities of energy-related CO₂. This study uses four long-term scenarios of energy use and related emissions to investigate opportunities for reducing the USSR's greenhouse gas emissions over the next 30 years. This paper shows that if no measures are taken to control these emissions, CO₂ and methane will increase by 1.5 to 2 times the 1990 level by the year 2020. However, this growth can be restrained dramatically through structural changes in the Soviet economy, improved energy efficiency and interfuel substitutions. Abating emissions of carbon in the USSR would entail the widespread implementation of energy policies and, for more substantial reductions, higher investments from the Soviet economy. Achieving these goals would also require broad support from the international community.     

The impact of fuel cell vehicle deployment on road transport greenhouse gas emissions: The China case

Considerable attention has been paid to energy security and climate problems caused by road vehicle fleets. Fuel cell vehicles provide a new solution for reducing energy consumption and greenhouse gas emissions, especially those from heavy-duty trucks. Although cost may become the key issue in fuel cell vehicle development, with technological improvements and cleaner pathways for hydrogen production, fuel cell vehicles will exhibit great potential of cost reduction. In accordance with the industrial plan in China, this study introduces five scenarios to evaluate the impact of fuel cell vehicles on the road vehicle fleet greenhouse gas emissions in China. Under the most optimistic scenario, greenhouse gas emissions generated by the whole fleet will decrease by 13.9% compared with the emissions in a scenario with no fuel cell vehicles, and heavy-duty truck greenhouse gas emissions will decrease by nearly one-fifth. Greenhouse gas emissions intensity of hydrogen production will play an essential role when fuel cell vehicles' fuel cycle greenhouse gas emissions are calculated; therefore, hydrogen production pathways will be critical in the future.     

Long-term greenhouse gas emission and petroleum reduction goals: Evolutionary pathways for the light-duty vehicle sector

To meet long-term environmental and energy security goals, the United States must reduce petroleum use in the light-duty vehicle fleet by 70% and greenhouse gas emissions by a factor of ten compared to business-as-usual growth projections for the year 2050. A wedge-based approach was used to quantify the scope of the problem in real terms, and to develop options for meeting mid-century targets. Four mitigation mechanisms were considered: (1) improvements in near-term vehicle technologies; (2) emphasis on low-carbon biofuels; (3) de-carbonization of the electric grid; and (4) demand-side travel-reduction initiatives. Projections from previous studies were used to characterize the potential of individual mitigation mechanisms, which were then integrated into a light-duty vehicle fleet model; particular emphasis was given to systemic constraints on scale and rates of change.     

Energy intensities and greenhouse gas emission mitigation in global agriculture

Energy efficiency and greenhouse gas emissions are closely linked. This paper reviews agricultural options to reduce energy intensities and their impacts, discusses important accounting issues related to system boundaries, land scarcity, and measurement units and compares agricultural energy intensities and improvement potentials on an international level. Agricultural development in recent decades, while increasing yields, has led to lower average energy efficiencies when comparing the 1960s and the mid 1980s. In the two decades thereafter, energy intensities in developed countries increased, but with little impact on greenhouse gas emissions. Efficiency differences across countries in the year 2000 suggest a maximum improvement potential of 500 million tons of CO₂ annually. If only below average countries would increase their energy efficiency to average levels of the year 2000, the resulting emission reductions would be below 200 million tons of CO₂ annually.

Weekly greenhouse gas emissions of municipalities: Methods and comparisons

Local authorities need timely information on their greenhouse gas (GHG) emissions and their causes, comparison with other municipalities and tools for dissemination of information to the citizens. This paper presents a weekly GHG emission calculation system, CO₂-report, which provides such data for citizens and local decision-makers in a timely manner, in contrast to the official emissions statistics, which are available on an annual basis 1–2 years afterwards. In this paper, we present the methodology and three main outputs of CO₂-report: (1) weekly GHG emissions; (2) advance annual emissions; and (3) final annual emissions for 2009 with comparison of 64 municipalities in Finland. We explain the reasons for the large variability of annual emissions, from 5 to 13 t CO₂-eq/capita, discuss the accuracy of advance and final emission estimates at local level, and show the weekly variability of emissions for three example municipalities with different emission profiles.     

Greenhouse gas emissions and energy balances of jatropha biodiesel as an alternative fuel in Tanzania

This paper evaluates GHG emissions and energy balances (i.e. net energy value (NEV), net renewable energy value (NREV) and net energy ratio (NER)) of jatropha biodiesel as an alternative fuel in Tanzania by using life cycle assessment (LCA) approach. The functional unit (FU) was defined as 1 tonne (t) of combusted jatropha biodiesel. The findings of the study prove wrong the notion that biofuels are carbon neutral, thus can mitigate climate change. A net GHG equivalent emission of about 848 kg t⁻¹ was observed. The processes which account significantly to GHG emissions are the end use of biodiesel (about 82%) followed by farming of jatropha for about 13%. Sensitivity analysis indicates that replacing diesel with biodiesel in irrigation of jatropha farms decreases the net GHG emissions by 7.7% while avoiding irrigation may reduce net GHG emissions by 12%. About 22.0 GJ of energy is consumed to produce 1 t of biodiesel. Biodiesel conversion found to be a major energy consuming process (about 64.7%) followed by jatropha farming for about 30.4% of total energy. The NEV is 19.2 GJ t⁻¹, indicating significant energy gain of jatropha biodiesel. The NREV is 23.1 GJ t⁻¹ while NER is 2.3; the two values indicate that large amount of fossil energy is used to produce biodiesel. The results of the study are meant to inform stakeholders and policy makers in the bioenergy sector.     

Sustainable energy development and greenhouse gas emissions in an island power system

The objective of this paper was to investigate the options for the sustainable development of the Northern Ireland energy supply system, reducing greenhouse gas emissions. Particular factors which must be considered centre around the isolation of the system, the prospect of a new gaspipeline and electrical interconnector to the rest of the U.K., and the re‐establishment of an electrical interconnector to the Republic of Ireland. The study has relevance for all similar isolated or island systems, which have particular problems because they tend to be relatively small in size, and their isolation means that inter‐connection with their neighbours is either weak or non‐existent. Because of this, they have to carry greater spare capacity than would normally be the case, with consequent efficiency and cost penalties. Copyright © 2000 John Wiley & Sons, Ltd.     

China's transportation energy consumption and CO2 emissions from a global perspective

Rapidly growing energy demand from China's transportation sector in the last two decades have raised concerns over national energy security, local air pollution, and carbon dioxide (CO₂) emissions, and there is broad consensus that China's transportation sector will continue to grow in the coming decades. This paper explores the future development of China's transportation sector in terms of service demands, final energy consumption, and CO₂ emissions, and their interactions with global climate policy. This study develops a detailed China transportation energy model that is nested in an integrated assessment model—Global Change Assessment Model (GCAM)—to evaluate the long-term energy consumption and CO₂ emissions of China's transportation sector from a global perspective. The analysis suggests that, without major policy intervention, future transportation energy consumption and CO₂ emissions will continue to rapidly increase and the transportation sector will remain heavily reliant on fossil fuels. Although carbon price policies may significantly reduce the sector's energy consumption and CO₂ emissions, the associated changes in service demands and modal split will be modest, particularly in the passenger transport sector. The analysis also suggests that it is more difficult to decarbonize the transportation sector than other sectors of the economy, primarily owing to its heavy reliance on petroleum products.     

Life-cycle analysis of greenhouse gas emissions from hydrogen delivery: A cost-guided analysis

The cost of hydrogen delivery for transportation accounts for most of the current H₂ selling price; delivery also requires substantial amounts of energy. We developed harmonized techno-economic and life-cycle emissions models of current and future H₂ production and delivery pathways. Our techno-economic analysis of dispensed H₂ costs guided our selection of pathways for the life-cycle analysis. In this paper, we present the results of market expansion scenarios using existing capabilities (for example, those that use H₂ from steam methane reforming, chlor-alkali, and natural gas liquid cracker plants), as well as results for future electrolysis plants that use nuclear, solar, and hydroelectric power. Reductions in greenhouse gas emissions for fuel cell electric vehicles compared to conventional gasoline pathways vary from 40% reduction for fossil-derived H₂ to 20-fold for clean H₂. Supplemental tables with greenhouse gas emissions data for each step in the H₂ pathways enable readers to evaluate additional scenarios.     

Reduce energy use and greenhouse gas emissions from global dairy processing facilities

Global butter, concentrated milk, and milk powder products use approximately 15% of annual raw milk production. Similar to cheese and fluid milk, dairy processing of these products can be energy intensive. In this paper, we analyzed production and energy data compiled through extensive literature reviews on butter, concentrated milk, milk and whey powder processing across various countries and plants. Magnitudes of national final and primary specific energy consumption (SEC) exhibited large variations across dairy products; in addition, the final SEC of individual plants and products exhibited significant variations within a country and between countries. Furthermore, we quantified national energy intensity indicators (EIIs) accounting for dairy product mixes and technological advancement. The significant variations of SEC and EII values indicate a high degree of likelihood that there is significant potential for energy savings in the global dairy processing industry. Based upon the study samples, we estimate potential energy savings for dairy processing industry in selected countries, and estimates annual reduction of 9–14 million metric-ton carbon-equivalent¹ could be achieved if measures are implemented to lower SEC values by 50–80% in half of global dairy plants. The paper calls for publication of more energy data from the dairy processing industry.     

Determining marginal electricity for near-term plug-in and fuel cell vehicle demands in California: Impacts on vehicle greenhouse gas emissions

California has taken steps to reduce greenhouse gas emissions from the transportation sector. One example is the recent adoption of the Low Carbon Fuel Standard, which aims to reduce the carbon intensity of transportation fuels. To effectively implement this and similar policies, it is necessary to understand well-to-wheels emissions associated with distinct vehicle and fuel platforms, including those using electricity. This analysis uses an hourly electricity dispatch model to simulate and investigate operation of the current California grid and its response to added vehicle and fuel-related electricity demands in the near term. The model identifies the “marginal electricity mix” - the mix of power plants that is used to supply the incremental electricity demand from vehicles and fuels - and calculates greenhouse gas emissions from those plants. It also quantifies the contribution from electricity to well-to-wheels greenhouse gas emissions from battery-electric, plug-in hybrid, and fuel cell vehicles and explores sensitivities of electricity supply and emissions to hydro-power availability, timing of electricity demand (including vehicle recharging), and demand location within the state. The results suggest that the near-term marginal electricity mix for vehicles and fuels in California will come from natural gas-fired power plants, including a significant fraction (likely as much as 40%) from relatively inefficient steam- and combustion-turbine plants. The marginal electricity emissions rate will be higher than the average rate from all generation - likely to exceed 600 gCO₂ equiv. kWh⁻¹ during most hours of the day and months of the year - and will likely be more than 60% higher than the value estimated in the Low Carbon Fuel Standard. But despite the relatively high fuel carbon intensity of marginal electricity in California, alternative vehicle and fuel platforms still reduce emissions compared to conventional gasoline vehicles and hybrids, through improved vehicle efficiency.     

Light duty vehicle transportation and global climate policy: The importance of electric drive vehicles

With a focus on the interaction between long-term climate targets and personal transport we review the electrification of light duty vehicles (LDVs) within a model that utilizes a learning-by-researching structure. By modeling the demand of vehicles, the use of fuels and emissions implied, the model solves for the optimum RD&D investments that decrease the cost of hybrid, plug-in hybrid and electric vehicles. A range of technology and climate policy scenarios provide long term projections of vehicle use that highlight the potential synergies between innovation in the transportation sector and the energy sector. We find that even when the capital cost of electric drive vehicles (EDVs) remains higher than that of traditional combustion engine alternatives, EDVs are likely to play a key role in the decarbonisation implied by stringent climate policy. Limited innovation in batteries results in notable increases in policy costs consistent with a two degree climate policy target.     

Comparison of the technical potential for hydrogen,battery electric,and conventional light-duty vehicles to reduce greenhouse gas emissions and petroleum consumption in the United States

Light-duty vehicles (LDV) are responsible for a large fraction of petroleum use and are a significant source of greenhouse gas (GHG) emissions in the United States. Improving conventional gasoline-powered vehicle efficiency can reduce petroleum demand, however efficiency alone cannot reach deep GHG reduction targets, such as 80% below the 1990 LDV GHG emissions level. Because the cost and availability of low-GHG fuels will impose limits on their use, significant reductions in GHG emissions will require combinations of fuel and vehicle technologies that both increase efficiency and reduce the emissions from fuel production and use. This paper examines bounding cases for the adoption of individual technologies and then explores combinations of advanced vehicle and fuel technologies. Limits on domestic biofuel production—even combined with significant conventional combustion engine vehicle improvements—mean that hydrogen fuel cell electric or battery electric vehicles fueled by low-GHG sources will be necessary. Complete electrification of the LDV fleet is not required to achieve significant GHG reduction, as replacing 40% of the LDV fleet with zero-emission hydrogen vehicles while achieving optimistic biofuel production and conventional vehicle improvements can allow attainment of a low GHG emission target. Our results show that the long time scale for vehicle turnover will ensure significant emissions from the LDV sector, even when lower emission vehicles and fuels are widely available within 15 years. Reducing petroleum consumption is comparatively less difficult, and significant savings can be achieved using efficient conventional gasoline-powered vehicles.     

Incorporating uncertainty analysis into life cycle estimates of greenhouse gas emissions from biomass production

Before further investments are made in utilizing biomass as a source of renewable energy, both policy makers and the energy industry need estimates of the net greenhouse gas (GHG) reductions expected from substituting biobased fuels for fossil fuels. Such GHG reductions depend greatly on how the biomass is cultivated, transported, processed, and converted into fuel or electricity. Any policy aiming to reduce GHGs with biomass-based energy must account for uncertainties in emissions at each stage of production, or else it risks yielding marginal reductions, if any, while potentially imposing great costs.This paper provides a framework for incorporating uncertainty analysis specifically into estimates of the life cycle GHG emissions from the production of biomass. We outline the sources of uncertainty, discuss the implications of uncertainty and variability on the limits of life cycle assessment (LCA) models, and provide a guide for practitioners to best practices in modeling these uncertainties. The suite of techniques described herein can be used to improve the understanding and the representation of the uncertainties associated with emissions estimates, thus enabling improved decision making with respect to the use of biomass for energy and fuel production.     

Energy balance and greenhouse gas emissions from the production and sequestration of charcoal from agricultural residues

Agricultural residues (wheat/barley/oat straw) can be used to produce charcoal, which can then be either landfilled off-site or spread on the agricultural field as a means for sequestering carbon. One centralized and five portable charcoal production technologies were explored in this paper. The centralized system produced 747.95 kg-CO₂eq/tonne-straw and sequestered 0.204 t-C/t-straw. The portable systems sequestered carbon at 0.141–0.217 t-C/t-straw. The net energy ratio (NER) of the portable systems was higher than the centralized one at 10.29–16.26 compared to 6.04. For the centralized system, the carbon sequestration and the cumulative energy demand were most sensitive to the charcoal yield. Converting straw residues into charcoal can reduce GHG emissions by 80% after approximately 8.5 years relative to the baseline of in-field decomposition, showing these systems are effective carbon sequestration methods.     

In search of a sustainable hydrogen economy: How a large-scale transition to hydrogen may affect the primary energy demand and greenhouse gas emissions

This paper reveals assessments made by a pan-European strategic project entitled HySociety (2003–2005), in which political, societal and technical challenges for developing a European hydrogen economy were addressed [Hetland J/SINTEF, editor, Task 2.3 D17. Set of actions to be taken at European level for the hydrogen society infrastructure. HySociety. Scientific report to be published on 〈$〈$www.hysociety.net〉$〉$, 2005]. From this work it has become evident that fossil fuels represent the most competitive option for hydrogen supply over the foreseeable future. Therefore it is mandatory to manage the reserves in a most sustainable way. The continued dependency of fossil fuels raises geopolitical issues of growing concern. Strategic questions pertaining to hydrogen energy are the prerequisites for supply versus the primary energy demand, greenhouse gas emissions and cost expectation in which hydrogen and fuel cells should be looked at in a broader context.