Life Cycle Carbon Dioxide Emissions Research Articles

Making sense of life cycle assessment results of electrified vehicles

Battery electric vehicles and plug-in hybrid electric vehicles can have life-cycle carbon dioxide emissions that can be close, within 5 % of each other, or very different depending on the efficiencies of the powertrain, relative contributions of battery and combustion engine to the traction power, and source of electricity. Life cycle assessments can provide insight into the variability in carbon dioxide emissions, but they are time consuming. In this work a simplified model that can explain the carbon dioxide emissions during the well-to-wheels portion of the life cycle is developed. The robustness of the simplified model is evaluated by varying parameters and comparing its results with those from the life cycle assessment. Assumptions must be made to conduct the assessment. The assumptions include the efficiencies of the internal combustion engine, the battery, the drivetrain, and regenerative braking, and the relative contribution of the battery to traction power in the plug-in hybrid electric vehicle. Renewable and non-renewable sources of generating electricity are considered. It is concluded that a plug-in hybrid electric vehicle with the same parameters as the battery electric vehicle can potentially be lower emitting only when the emissions factor of the electricity generation and the internal combustion engine efficiency are high. For low carbon intensity electricity generation, the plug-in vehicle emits more carbon dioxide than the battery electric vehicle for the range of internal combustion engine efficiencies considered.

Analysing carbon impacts of green roof at Hilton Watford: life-cycle assessment approach

This paper investigates the environmental aspects and energy impacts of implementing a green roof system at the Hilton Watford hotel, utilising building information modelling software (Revit) for three-dimensional modelling and Insight for energy simulation. Following EN 15804:2012+A2:2019, the study employs life-cycle assessment methodology, focusing on embodied and operational carbon. Environmental Product Declarations, Inventory of Carbon and Energy database and the Royal Institution of Chartered Surveyors guideline inform embodied carbon calculations. The results show the green roof system releases 263 839.56 kgCO2e as embodied carbon, while its sedum layer sequesters 211 468.12 kgCO2e over a 50 year lifespan. Energy efficiency analysis indicates a 3.3 kWh/(m2/year) reduction in energy consumption, leading to a 112 130.31 kgCO2e reduction in operational carbon dioxide emissions, highlighting the environmental benefits of green roof adoption. The findings suggest a 0.35% mitigation of whole life-cycle carbon dioxide emissions, with greater impact in situations of lower insulation effectiveness, showcasing the potential of green roofs in reducing carbon dioxide emissions. Additionally, the green roof incurs a minimal financial burden, constituting only 0.51% of the overall project cost.

Trade drives leakage of life-cycle carbon dioxide emissions from plastics in China over 2010–2021

Trade drives increased life-cycle carbon dioxide (CO2) emissions and carbon leakage from plastics, increasing the environmental burden on the supply chain. Therefore, assessing the characteristics and drivers of plastic carbon emissions will help develop emission reduction strategies from a supply chain perspective. In this study, we present a model framework for life-cycle assessment, optimized input-output analysis, and structural decomposition analysis. Specifically, for the first time, we assess the life-cycle CO2 emissions of plastics in China, the world's largest producer and consumer, and consider the input, production, consumption, and income stages of the plastic supply chain. China's plastic CO2 emissions increased by 38.07% from 2010 to 2021 and, under a business-as-usual path, will consume 4.2–5.4% of the global carbon budget by 2050. From a supply chain perspective, each economic sector assumes different responsibilities for emissions at different stages. Despite increasing emissions, China's economic structure has potentially improved the embodied carbon leakage from the intersectoral and international trade in plastics. Furthermore, regarding socioeconomic factors, the levels of final demand (63%) and primary input (61%) dominated the increase in plastic CO2 emissions from 2012 to 2020, and the intensity of emissions was the key to reducing emissions. The novelty of this study is that the model we proposed can solve the data limitations of the global plastics supply chain and focuses for the first time on the input and income stages and their drivers.

Affordability assessment of passive retrofitting measures for residential buildings using life cycle assessment

Climate change impacts have been increasingly noticeable worldwide, especially as energy concerns have increased. Because buildings consume significant amounts of energy, sustainably retrofitting existing buildings has become essential. However, several countries are pretty concerned about the affordability of retrofitting and energy conservation measures. Therefore, this research assesses the affordability of selected passive heating and cooling retrofitting strategies using the residual approach methodology. Specifically, this work studies the effects and efficiency of retrofitting the residential buildings in Irbid, Jordan, through life cycle analysis, where dynamic thermal simulation (IES-VE) is employed. This strategy determines the required heating and cooling loads, the life cycle carbon dioxide emissions, and the economic feasibility of retrofitting using the Net Present Value methodology. The results show that passive building retrofitting can generate considerable economic and environmental benefits. Additionally, the affordability assessment reveals that retrofitting measures are affordable for 73–78% of Jordanian households. Furthermore, retrofitting makes the energy required for building conditioning affordable for 82.8–85.8% of households. This affordability assessment proved that the initial investment cost of retrofitting is the major obstacle to implementing it, especially for low-income households, despite the long-term economic and environmental benefits of this process. Thus, governmental financial support for the retrofitting projects would support achieving the sustainable development goals and mitigating climate change impacts.

Energy, economic and environmental (3E) analysis for the renewable jet fuel production process

Blending conventional petroleum jet fuel with renewable fuel obtained from hydro-processing of cooking oil wastes can significantly reduce the carbon footprint of the aviation sector. Renewable jet fuel (RJF) remains for the most part more expensive than conventional jet fuel and the life-cycle emissions reduction depends on the feedstock. For promoting mass production of used cooking oil (UCO) based jet fuel, a 3E (energy/exergy, environmental and economic) analysis of a simulated processing plant is carried out. Hydrogen is the main component in the two-step process: hydro-processing and hydro-cracking/isomerization. Hydrogen production and exergy destruction in the process significantly influence the life-cycle emissions of the RJF. The low exergy efficiency of the process units where significant heat transfer occurs generates an increase in the price of the products. Results show a life-cycle carbon dioxide emissions reduction from 41 % to 81 % when combusting the hydro-processed jet fuel instead of conventional jet fuel. The minimum fuel selling price could be very close to conventional jet fuel (about 18 % more expensive) if an effective cooking oil wastes collection system is in place. Moreover, when implementing a carbon tax above $37/tCO 2 the price becomes equal to conventional jet fuel. UCO is the most sustainable feedstock as there is no competition with the food market and the environmental benefits justify government spending for promoting mass production.

Road life-cycle carbon dioxide emissions and emission reduction technologies: A review

Carbon dioxide (CO 2 ) emissions from the road sector have attracted increasing attention in current years. This paper attempted to provide a systematic review of the existing research efforts on road life-cycle CO 2 emissions by analyzing the system's boundary division, identifying the CO 2 emission contributions of each life-cycle phase, listing major emission contributors, exploring related emission reduction technologies, and giving directions for future development. The research showed that the road life cycle is usually divided into five phases: material production, construction, use, maintenance and end-of-life (EOL) phases. The use phase and the initial construction stage (including material production and construction phases) contributed the most CO 2 emissions during the road life cycle. In detail, the production of cement, asphalt and steel were the three main emission contributors in the material production phase. The pavement roughness, albedo, and concrete carbonation were the main factors affecting emissions in the use phase. In addition, emission reduction technologies such as using recycled materials and recycling techniques, lowering mixing temperature, and equipment energy substitution were commonly used to reduce emissions from material production and construction phases. The application of emerging technologies such as carbon capture and storage, carbon sink, and the use of hydrogen, solar and photovoltaic in the road sector may have emission reduction potentials and should be highlighted more in future studies. • The CO 2 emission contributions and major contributors of each road phase are identified. • The commonly-used CO 2 emission reduction technologies for major emission contributors are summarized. • Recycled materials, advanced recycling and mixing techniques, and energy substitution are commonly used to reduce emissions. • Emerging technologies such as carbon sink have emission reduction potentials in the road sector but need further studies.

The Renewable Hydrogen–Methane (RHYME) Transportation Fuel: A Practical First Step in the Realization of the Hydrogen Economy

The permanent introduction of green hydrogen into the energy economy would require that a discriminating selection be made of its use in the sectors where its value is optimal in terms of relative cost and life cycle reduction in carbon dioxide emissions. Consequently, hydrogen can be used as an energy storage medium when intermittent wind and solar power exceed certain penetration in the grid, likely above 40%, and in road transportation right away, to begin displacing gasoline and diesel fuels. To this end, the proposed approach is to utilize current technologies represented by PHEV in light-duty and HEV in heavy-duty vehicles, where a high-performance internal combustion engine is used with a fuel comprised of 15–20% green hydrogen and 85–89% green methane depending on vehicle type. This fuel, designated as RHYME, takes advantage of the best attributes of hydrogen and methane, results in lower life cycle carbon dioxide emissions than BEVs or FCEVs and offers a cost-effective and pragmatic approach, both locally as well as globally, in establishing hydrogen as part of the energy economy over the next ten to thirty years.

Life Cycle Carbon Dioxide Emissions Assessment in the Design Phase: A Case of a Green Building in Vietnam

Life Cycle Carbon Dioxide Emissions Assessment in the Design Phase: A Case of a Green Building in Vietnam

Hybrid techno-economic and environmental assessment of adiabatic compressed air energy storage system in China-Situation

Adiabatic compressed air energy storage technology is found to reliably stabilize the power load and support renewable energy generation. Comprehensive life cycle techno-economic and environmental optimization analysis for this technology are of great importance to improve system performance. In this study, we first proposed an integrated hybrid life cycle optimization framework to understand trade-offs between the techno-economic and environmental performance of adiabatic compressed air energy storage plant in China, by combining integrated hybrid life cycle analysis with multi-objective optimization. The results show that solutions with investment cost, carbon dioxide emission, water and energy consumption of 1.47 k$/kW, 1.48 kg/kWh, 0.097 m3/kWh and 2.08 × 104 kJ/kWh, respectively, are promising for a practical adiabatic compressed air energy storage system design in China. An analysis of the materials and energy contribution towards the environmental impact at selected optimum points are carried out in detail to elucidate means for reducing the life-cycle emission of the plant; besides, an impact comparison for plant installation in different provinces was performed to provide guidance for policymakers in site selection. As a result, the life-cycle carbon dioxide emission, water and energy consumption of the plant were found to be large in the provinces with a high proportion of thermal power generation — for example, Shandong and Jiangsu — yet the most environmental benefit is achieved in these provinces if the system is combined with the local power grid.

Life cycle carbon dioxide emissions of bike sharing in China: Production, operation, and recycling

Recent global environmental initiatives designed to achieve a more sustainable society include the United Nations’ sustainable development goals (SDGs) and the Paris Agreement. While the shared economic model has long been linked to the creation of the sustainable use of resources, one problem encountered by the bike sharing is whether the current management model can maintain the focus on sustainability in China. Based on the amount of resources consumed during bike production, operation, and recycling, this paper aims to use life cycle carbon emission assessment to calculate an emission reduction threshold for bike-sharing industry. The research obtained energy consumption data from the OFO Curve bike, which is the most commonly used type of bike sharing in China. Calculating the average distance traveled and number of times each bike was used per day via the Baidu Map Application Program Interface, we found that the average number of times each bike was used per day was 4.552, and the average riding distance was 0.356 km. Additionally, the overall utilization of shared bikes averages about 50%. Further results show that the whole life cycle carbon footprint of one bike is 34.56 kg CO2. The power generation by incineration produces 1.9916 kg CO2 in less than a landfill. If a bike is deposited directly in a landfill, it will take 31 years to degrade. The final calculations show that based on the current number of bikes, each used at least 686 days to achieve a net positive reduction in emissions. This paper provides a basis for capacity management and operation management of shared bikes from the perspective of pro-environment and provides a new angle for the research on environmental impact of sharing economy.

Planning an Energy–Water–Environment Nexus System in Coal-Dependent Regions under Uncertainties

Energy, water, and environment are inextricably interwoven in the complex social and economic networks. This study proposes an optimization model for planning the energy–water–environment nexus system (EWENS) through incorporating the linear autoregressive integrated moving average model prediction model (ARIMA), Monte Carlo simulation, chance-constrained programming (CCP), and type-2 fuzzy programming (T2FP) into one general framework. This method effectively tackles type-2 fuzzy set and stochastic uncertainties. The proposed model can quantitatively explore the interconnections between water, energy, and environment systems and generate an optimized solution for EWENS. The proposed model was applied to a coal-dominated region of China, i.e., Inner Mongolia. Several findings and policy implications were obtained. First, the total water supply for energy-generating activities will range from 1368.10 × 106 m3 to 1370.62 × 106 m3, at the end of planning periods. Second, the electricity for water supply will range from 2164.07 × 106 kWh to 2167.65 × 106 kWh at the end of the planning periods, with a growth rate of 46.06–48.72%. Thirdly, lifecycle carbon dioxide emission (LCDE) is projected to range from 931.85 × 106 tons to 947.00 × 106 tons at the end of the planning periods. Wastewater and SO2, NOx, and particulate matter (PM) emissions are projected to be 42.72 × 103–43.45 × 103 tons, 183.07 × 103–186.23 × 103 tons, 712.38 × 103–724.73 × 103 tons, and 38.14 × 103–38.80 × 103 tons at the end of the planning periods. Fourthly, as the largest electricity-exporting city of China, Inner Mongolia’s electricity outflows will export 1435.78 × 106 m3 of virtual water to other regions, implying that Inner Mongolia is pumping its important water resource to support other regions’ electricity demands. Finally, high carbon mitigation levels can effectively optimize the electricity power mix, reduce consumption amounts of water and coal, and mitigate air pollutants, wastewater, and LCDE. The obtained results provide useful information for managers to develop a sustainability plan for the EWENS.

Considering uncertainty in life-cycle carbon dioxide emissions of fly ash concrete

Concrete, the most widely used construction material in the world, consumes a large amount of resources and emits significant greenhouse gases during production. Previous studies have adopted a deterministic method to confirm that substituting fly ash for cement in concrete can reduce carbon dioxide emissions. However, the life-cycle assessment involves a lot of assumptions and associated uncertainties. This paper reports on an investigation to consider those uncertainties. Two types of uncertainty – parameter uncertainty and uncertainty due to the choice of functional units – were investigated using the Monte Carlo simulation method and scenario analysis method, respectively. The results indicated that results varied significantly with the preset functional units. When considering volume and strength, although the addition of fly ash in concrete can reduce emissions, compressive strength is also decreased resulting in a zero net change in emissions performance. When adopting other functional units, the addition of fly ash has emission-reduction potential. By considering parameter uncertainty, although average emissions decrease with addition of fly ash, the standard deviation increases with addition, indicating an increasing discreteness. It is concluded that considering the uncertainty in the life-cycle emission analysis of fly ash concrete leads to more rational decision-making for concrete selection.

Briefing: Life-cycle carbon assessment of prefabricated buildings: challenges and solutions

Buildings contribute to significant carbon dioxide emissions over their life cycle. The prefabrication approach has been promoted and increasingly integrated into building engineering and construction, which has attracted increasing research into the life-cycle carbon assessment (LCCA) of prefabricated buildings. However, there exist challenges. This paper examines the challenges and, through rethinking their theoretical fundamentals, proposes solutions with the aim to enhance the reliability and validity of research into the LCCA of prefabricated buildings. The challenges are found to be implicit system boundaries of prefabrication and LCCA: inconsistent methods, models and units of analysis of estimating buildings’ life-cycle carbon dioxide emissions and LCCA being a labour-intensive process with limited accountability. The proposed solutions are a regression model of relating buildings’ LCCA to 12 system boundaries, expressed by the system boundaries’ inconsistency ratio (I R), which shows the level of difference between any two system boundaries; a five-level framework of units of analysis consisting of material, component, assembly, flat and building; and a smart-technology-integrated approach for automatic LCCA. The solutions are important and timely to help reduce buildings’ life-cycle carbon dioxide emissions effectively for achieving long-term sustainability of society.

A new approach to determine insulation material and thickness from a life-cycle perspective

Energy-efficient retrofitting of buildings is an important topic for the future world. Adding thermal insulation to the building envelope is the most common and well-known measure, but existing strategies for energy-efficient retrofits do not consider the life-cycle energy consumption and carbon dioxide (CO2) emissions of the insulation materials. This paper introduces a new approach for selecting the optimum insulation material and thickness based on life-cycle energy consumption and carbon dioxide emissions. The approach was applied to a multi-storey residential building located in İzmir, Turkey, which has a Mediterranean climate, and the results are compared with the same building in Erzurum, Turkey, which has a cold climate. The comparison reveals the effect of thermal insulation on energy consumption and carbon dioxide emissions. The results show that increasing thermal insulation thickness provides less energy efficiency in the Mediterranean climate than in the cold climate. In addition, if the thickness is not optimised according to the insulation material, the life-cycle carbon dioxide emissions and energy consumption may increase contrary to expectations. Extruded polystyrene insulation with 3 cm thickness for the Mediterranean climate and rock wool insulation with 9 cm thickness in cold climate have the optimum life-cycle energy and carbon dioxide emission performance for the case-study building.

Life cycle carbon dioxide emissions for fill dams

The construction industry including infrastructure construction, affects the environment due to the use of a considerable amount of resources and energy. The management of the environmental effect of dams for agricultural reservoirs is especially important in South Korea because of their large scale and nationwide distribution. The objective of this study is to propose an assessment method for evaluating life cycle carbon dioxide emissions associated with fill dams and to characterize carbon dioxide emissions to use in effectively addressing the environmental concerns for infrastructures. A total of four dams were selected for the research, and the material production, use of equipment and transportation were considered as the causes of carbon dioxide emissions at the dams. The effective life cycle of a fill dam was assumed to be 100 years. The results of the research indicated that the total amount of carbon dioxide emissions were different for each dam according to their characteristics, and the results showed that the dam size is the primary cause. In addition, the carbon dioxide emissions increased as the period of use increased, and a rapid increase was indicated in 40–50 years interval of the dams’ use periods because the repair activities were concentrated in those years. Materials were the biggest contributor in the amount of total carbon dioxide emissions at all four sites and the ratio of carbon dioxide emissions caused by materials was higher than any other factors in most processes. There was little difference in the proportion of carbon dioxide emissions for each process in the total carbon dioxide emissions for the four sites. Most carbon dioxide was emitted during repair activities at the two largest dams. Activities associated with the construction process was the major source of carbon dioxide emissions at the two other dams. This difference in process carbon dioxide emissions was the result of the difference in the construction scale for the embankment elevation. The assessment method that has been proposed in this study reflects the characteristics of fill dams, and the result of estimating carbon dioxide emissions indicates that we are able to reduce carbon dioxide emissions in the life cycle of fill dams by selecting the construction materials and the repair methods with a low carbon dioxide emissions.

Is the optimal decarbonization pathway influenced by indirect emissions? Incorporating indirect life-cycle carbon dioxide emissions into a European TIMES model

Energy system optimization models (ESOMs) such as MARKAL/TIMES are used to support energy policy analysis worldwide. ESOMs cover the full life-cycle of fuels from extraction to end-use, including the associated direct emissions. Nevertheless, the life-cycle emissions of energy equipment and infrastructure are not modelled explicitly. This prevents analysis of questions relating to the relative importance of emissions associated with the build-up of infrastructure and other equipment required for decarbonization.We have soft-linked an environmentally-extended input-output (EEIO) model to a European TIMES Model (ETM-UCL) with the aim of addressing the following questions:-In what ways does the inclusion of indirect emissions change the optimal technology pathway for decarbonizing the European energy system?-How much does the present value of key low-carbon technologies change when indirect emissions are accounted for in a decarbonization scenario for Europe?We show that, although indirect emissions are a relatively small portion of overall power sector emissions (<10% in 2050), including them in the model leads to changes in the optimal power sector portfolio. Renewable energy technologies become relatively less attractive once indirect emissions are included within the optimization framework, and we quantify this effect, showing that it is not large. Changes to the relative attractiveness of specific renewable energy technologies are more pronounced than the reduction in attractiveness of renewable energy as a whole: in our main scenarios wind energy saw increased relative deployment in 2050 when indirect emissions are accounted for, since it displaced other technologies with higher life-cycle emissions (notably solar PV). Optimal cumulative installed capacity of PV in the EU 2050 is at least 7% lower when indirect emissions are included. We conclude that policy advice derived from ESOMs that focuses on the roles of specific technologies should ensure that it is robust to the possible effects of indirect emissions.

Strategy in Reducing the Pace of the Greenhouse Gas Emission from the Electricity Sector in Southeast Sulawesi

Climate change in Indonesia is receiving a lot of concern as the nation is the top ten world largest emitter of the greenhouse gases. To relieve the concern, Indonesia had proposed to cut the gas emissions by 26 percent by 2020 from business-as-usual (BAU) levels and proposed a 41 percent emission reduction below BAU target conditional to international support for Nationally Appropriate Mitigation Actions (NAMAs). This study deals with the strategy in reducing the acceleration of the greenhouse gas emission from the power sector in Southeast Sulawesi, a developing province in Indonesia with its high electricity demand in recent years. It calculates of the annual greenhouse emission from the electricity generation mix in this province, using the projected annual electricity generation and projected power plants installed under the power supply business plan (RPUTL) of the state electricity company (PLN Indonesia) and the lifecycle carbon dioxide emission equivalent. Some scenarios are proposed, by varying the power generation mix in the case of inclusion and exclusion the projected clean renewable powers in the year of 2020 and 2022. The result shows that in 2020, by the inclusion of the projected clean renewable powers in the power generation mix (around 5 percent), it can reduce the annual greenhouse gas emission almost 6 percent. In 2022, by maintaining the amount of the power generation from fossil sources as those in 2020 and maximizing the use of the clean powers in the electricity generation mix (around 20 percent), under the power provision plan, it can reduce the emission by 26 percent.

Life cycle carbon dioxide emissions simulation and environmental cost analysis for building construction

The construction industry causes a number of complex environmental effects, particularly carbon dioxide emissions. In the past decade, decision makers in the construction industry have focused on economic costs rather than environmental habitat concerns. However, in recent years, companies have slowly realized the importance of the environmental effects of building life cycles, in addition to maximizing profit. Therefore, this study developed a carbon dioxide emissions evaluation system and an environmental cost calculation method. The simulations considered the consumption of fossil fuel, electricity, and water. A systematic approach was proposed for optimizing the balance of the carbon dioxide emissions and environmental cost during building life cycle. Particularly, this study demonstrated a simplified metric for converting carbon dioxide emissions into environmental costs. The proposed method can guide engineers and architects in evaluating the primary environmental risk for a building life cycle and selecting an appropriate construction method.

Economical approach for sizing a battery in plug-in hybrid electric vehicles considering statistical user behaviour and power demand for climatisation

This paper presents a novel analytic method for determining the optimal battery capacity for plug-in hybrid electric vehicles (PHEVs) from an economical point of view. Owing to its analytic structure, this generic approach allows a fast parametrisation and evaluation of different influences on the optimal battery capacity. It is shown how this approach can be parametrised and the sensitivity of the optimal battery capacity to different influences is evaluated (battery and energy prices, battery degradation, cabin climatisation, engine efficiency and usable waste heat). The results and the presented adaption of this approach to an ecological optimisation of the battery capacity in terms of life cycle carbon dioxide emissions illustrate the potential of this novel approach.

An Experimental Investigation of Reactivity-Controlled Compression Ignition Combustion in a Single-Cylinder Diesel Engine Using Hydrous Ethanol

Dual-fuel reactivity-controlled compression ignition (RCCI) combustion using port injection of a less reactive fuel and early-cycle direct injection (DI) of a more reactive fuel has been shown to yield both high thermal efficiency and low NOX and soot emissions over a wide engine operating range. Conventional and alternative fuels such as gasoline, natural gas, and E85 as the lower reactivity fuel in RCCI have been studied by many researchers; however, published experimental investigations of hydrous ethanol use in RCCI are scarce. Making greater use of hydrous ethanol in internal combustion engines has the potential to dramatically improve the economics and life cycle carbon dioxide emissions of using bioethanol. In this work, an experimental investigation was conducted using 150 proof hydrous ethanol as the low reactivity fuel and commercially available diesel as the high reactivity fuel in an RCCI combustion mode at various load conditions. A modified single-cylinder diesel engine was used for the experiments. Based on previous studies on RCCI combustion by other researchers, early-cycle split-injection strategy of diesel fuel was used to create an in-cylinder fuel reactivity distribution to maintain high thermal efficiency and low NOX and soot emissions. At each load condition, timing and mass fraction of the first diesel injection was held constant, while timing of the second diesel injection was swept over a range where stable combustion could be maintained. Since hydrous ethanol is highly resistant to auto-ignition and has large heat of vaporization, intake air heating was needed to obtain stable operations of the engine. The study shows that 150 proof hydrous ethanol can be used as the low reactivity fuel in RCCI through 8.6 bar indicated mean effective pressure (IMEP) and with ethanol energy fraction up to 75% while achieving simultaneously low levels of NOX and soot emissions. With increasing engine load, less intake heating is needed and exhaust gas recirculation (EGR) is required to maintain low NOX emissions.