Environmental aspects of the electric car

The Tesla Model S (left) and the Tesla Mode (right)

electric cars have several benefits over conventional internal combustion engine automobiles, they are still subject to environmental regulation due to heavy reliance of rare-earth elements such as neodymium, most of which are from China. However, several key environmental benefits includes a significant reduction of local air pollution, especially in cities, as they do not emit harmful tailpipe pollutants such as particulates (soot), volatile organic compounds, hydrocarbons, carbon monoxide, ozone, lead, and various oxides of nitrogen.^[1][2][3] The amount of carbon dioxide emitted depends on the emission intensity of the power sources used to charge the vehicle, the efficiency of the said vehicle and the energy wasted in the charging process. For mains electricity the emission intensity varies significantly per country and within a particular country, and on the demand, the availability of renewable sources and the efficiency of the fossil fuel-based generation used at a given time.^[4][5][6]

Electricity generation for electric cars

A solar energy charging station in North America

Electric cars usually also show significantly reduced greenhouse gas emissions, depending on the method used for electricity generation to charge the batteries.^[7][8] For example, some battery electric vehicles do not produce CO₂ emissions at all, but only if their energy is obtained from sources such as solar, wind, nuclear, or hydropower.^[9]

Even when the power is generated using fossil fuels, electric vehicles usually, compared to gasoline vehicles, show significant reductions in overall well-wheel global carbon emissions due to the highly carbon-intensive production in mining, pumping, refining, transportation and the efficiencies obtained with gasoline.^[10] Researchers in Germany have claimed that while there is some technical superiority of electric propulsion compared with conventional technology that in many countries the effect of electrification of vehicles' fleet emissions will predominantly be due to regulation rather than technology.^[11] Indeed, electricity production is submitted to emission quotas, while vehicles' fuel propulsion is not, thus electrification shifts demand from a non-capped sector to a capped sector. This means that the emissions of electrical grids can be expected to improve over time as more wind and solar generation is deployed.

Many countries are introducing CO₂ average emissions targets across all cars sold by a manufacturer, with financial penalties on manufacturers that fail to meet these targets. This has created an incentive for manufacturers, especially those selling many heavy or high-performance cars, to introduce electric cars as a means of reducing average fleet CO₂ emissions.^[12]

Air pollution and carbon emissions

Electric cars have several benefits over conventional internal combustion engine automobiles, including a significant reduction of local air pollution, especially in cities, as they do not emit harmful tailpipe pollutants such as particulates (soot), volatile organic compounds, hydrocarbons, carbon monoxide, ozone, lead, and various oxides of nitrogen.^[1][2][3] The clean air benefit may only be local because, depending on the source of the electricity used to recharge the batteries, air pollutant emissions may be shifted to the location of the generation plants.^[7] This is referred to as the long tailpipe of electric vehicles. The amount of carbon dioxide emitted depends on the emission intensity of the power sources used to charge the vehicle, the efficiency of the said vehicle and the energy wasted in the charging process. For mains electricity the emission intensity varies significantly per country and within a particular country, and on the demand, the availability of renewable sources and the efficiency of the fossil fuel-based generation used at a given time.^[4][5][6]

Charging a vehicle using renewable energy (e.g., wind power or solar panels) yields very low carbon footprint-only that to produce and install the generation system (see Energy Returned On Energy Invested.) Even on a fossil-fueled grid, it's quite feasible for a household with a solar panel to produce enough energy to account for their electric car usage, thus (on average) cancelling out the emissions of charging the vehicle, whether or not the panel directly charges it.^[13] Even when using exclusively grid electricity, introducing EVs comes with a major environmental benefits in most (EU) countries, except those relying on old coal fired power plants.^[5] So for example the part of electricity, which is produced with renewable energy is (2014) in Norway 99 percent and in Germany 30 percent.

United States

Net electricity generation by energy source.^[14] Coal is no longer the predominate source of electricity in the U.S.   Chart does not take into account roof top solar.

The following table compares tailpipe and upstream CO₂ emissions estimated by the U.S. Environmental Protection Agency for all series production model year 2014 all-electric passenger vehicles available in the U.S. market. Since all-electric cars do not produce tailpipe emissions, for comparison purposes the two most fuel efficient plug-in hybrids and the typical gasoline-powered car are included in the table. Total emissions include the emissions associated with the production and distribution of electricity used to charge the vehicle, and for plug-in hybrid electric vehicles, it also includes emissions associated with tailpipe emissions produced from the internal combustion engine. These figures were published by the EPA in October in its 2014 report "Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends."^[15]

To account for the upstream CO₂ emissions associated with the production and distribution of electricity, and since electricity production in the United States varies significantly from region to region, the EPA considered three scenarios/ranges with the low end scenario corresponding to the California powerplant emissions factor, the middle of the range represented by the national average powerplant emissions factor, and the upper end of the range corresponding to the powerplant emissions factor for the Rocky Mountains. The EPA estimates that the electricity GHG emission factors for various regions of the country vary from 346 g CO₂/kWh in California to 986 g CO₂/kWh in the Rockies, with a national average of 648 g CO₂/kWh.^[15] In the case of plug-in hybrids, and since their all-electric range depends on the size of the battery pack, the analysis introduced a utility factor as a projection of the share of miles that will be driven using electricity by an average driver.^[15]

The Union of Concerned Scientists (UCS) published in 2012, a report with an assessment of average greenhouse gas emissions resulting from charging plug-in car batteries considering the full life-cycle (well-to-wheel analysis) and the fuel used to generate electric power by region in the U.S. The study used the Nissan Leaf all-electric car to establish the analysis's baseline. The UCS study expressed the results in terms of miles per gallon instead of the conventional unit of grams of carbon dioxide emissions per year. The study found that in areas where electricity is generated from natural gas, nuclear, or renewable resources such as hydroelectric, the potential of plug-in electric cars to reduce greenhouse emissions is significant. On the other hand, in regions where a high proportion of power is generated from coal, hybrid electric cars produce less CO₂ emissions than plug-in electric cars, and the best fuel efficient gasoline-powered subcompact car produces slightly less emissions than a plug-in car. In the worst-case scenario, the study estimated that for a region where all energy is generated from coal, a plug-in electric car would emit greenhouse gas emissions equivalent to a gasoline car rated at a combined city/highway fuel economy of 30 mpg_‑US (7.8 L/100 km; 36 mpg_‑imp). In contrast, in a region that is completely reliant on natural gas, the plug-in would be equivalent to a gasoline-powered car rated at 50 mpg_‑US (4.7 L/100 km; 60 mpg_‑imp) combined.^[17][18]

The study found that for 45% of the U.S. population, a plug-in electric car will generate lower CO₂ emissions than a gasoline-powered car capable of a combined fuel economy of 50 mpg_‑US (4.7 L/100 km; 60 mpg_‑imp), such as the Toyota Prius. Cities in this group included Portland, Oregon, San Francisco, Los Angeles, New York City, and Salt Lake City, and the cleanest cities achieved well-to-wheel emissions equivalent to a fuel economy of 79 mpg_‑US (3.0 L/100 km; 95 mpg_‑imp). The study also found that for 37% of the population, the electric car emissions will fall in the range of a gasoline-powered car rated at a combined fuel economy between 41 to 50 mpg_‑US (5.7 to 4.7 L/100 km; 49 to 60 mpg_‑imp), such as the Honda Civic Hybrid and the Lexus CT200h. Cities in this group include Phoenix, Arizona, Houston, Miami, Columbus, Ohio and Atlanta, Georgia. An 18% of the population lives in areas where the power supply is more dependent on burning carbon, and emissions will be equivalent to a car rated at a combined fuel economy between 31 to 40 mpg_‑US (7.6 to 5.9 L/100 km; 37 to 48 mpg_‑imp), such as the Chevrolet Cruze and Ford Focus. This group includes Denver, Minneapolis, Saint Louis, Missouri, Detroit, and Oklahoma City.^[18][19][20] The study found that there are no regions in the U.S. where plug-in electric cars will have higher greenhouse gas emissions than the average new compact gasoline engine automobile, and the area with the dirtiest power supply produces CO₂ emissions equivalent to a gasoline-powered car rated 33 mpg_‑US (7.1 L/100 km; 40 mpg_‑imp).^[17]

In September 2014, the UCS published an updated analysis of its 2012 report. The 2014 analysis found that 60% of Americans, up from 45% in 2009, live in regions where an all-electric car produce fewer CO₂ equivalent emissions per mile than the most efficient hybrid. The UCS study found two reasons for the improvement. First, electric utilities have adopted cleaner sources of electricity to their mix between the two analysis. Second, electric vehicles have become more efficient, as the average 2013 all-electric vehicle used 0.33 kWh per mile (0.21 kWh/km), representing a 5% improvement over 2011 models. Also, some new models are cleaner than the average, such as the BMW i3, which is rated at 0.27 kWh by the EPA. In states with a cleaner mix generation, the gains were larger. The average all-electric car in California went up to 95 mpg_‑US (2.5 L/100 km) equivalent from 78 mpg_‑US (3.0 L/100 km) in the 2012 study. States with dirtier generation that rely heavily on coal still lag, such as Colorado, where the average BEV only achieves the same emissions as a 34 mpg_‑US (6.9 L/100 km; 41 mpg_‑imp) gasoline-powered car. The author of the 2014 analysis noted that the benefits are not distributed evenly across the U.S. because electric car adoptions is concentrated in the states with cleaner power.^[21][22]

Improving on the UCS analysis and several others, an analysis by economists affiliated with the National Bureau of Economic Research (NBER), published in November 2014, estimated marginal emissions of electricity demand that vary by location and time of day across the United States.^[23][24] The marginal analysis, applied to plug-in electric vehicles, found that the emissions of charging PEVs vary by region and hours of the day. In some regions, such as the Western U.S. and Texas, CO₂ emissions per mile from driving PEVs are less than those from driving a hybrid car. However, in other regions, such as the Upper Midwest, charging during the recommended hours of midnight to 4 a.m. implies that PEVs generate more emissions per mile than the average car currently on the road.

Change from 2009 to 2012 of the percentage of Americans that live in regions where powering an electric vehicle on the regional electricity grid produces lower global warming emissions than a gasoline car expressed in terms of combined cith/highway fuel economy rating. Source: Union of Concerned Scientists.^[25]

The results show a tension between electricity load management and environmental goals as the hours when electricity is the least expensive to produce tend to be the hours with the greatest emissions. This occurs because coal-fired plants, which have higher emission rates, are most commonly used to meet base-level and off-peak electricity demand; while natural gas plants, which have relatively low emissions rates, are often brought online to meet peak demand.^[24]

In November 2015, the Union of Concerned Scientists published a new report comparing two battery electric vehicles (BEVs) with similar gasoline vehicles by examining their global warming emissions over their full life-cycle, craddle-to-grave analysis. The two BEVs modeled, midsize and full-size, are based on the two most popular BEV models sold in the United States in 2015, the Nissan LEAF and the Tesla Model S. The study found that all-electric cars representative of those sold today, on average produce less than half the global warming emissions of comparable gasoline-powered vehicles, despite higher emissions of manufacture. Considering the regions where the two most popular electric cars are being sold, excess manufacturing emissions are offset within 6 to 16 months of average driving. The study also concluded that driving an average EV results in lower global warming emissions than driving a gasoline car that gets 50 mpg_‑US (4.7 L/100 km) in regions covering two-thirds of the U.S. population, up from 45% in 2009. Based on where EVs are sold in the U.S. in 2015, the average EV produces global warming emissions equal to a gasoline vehicle with a 68 mpg_‑US (3.5 L/100 km) fuel economy rating. The authors identified two main reasons for this reduction since the 2012 study. Electricity generation has become cleaner, as coal-fired generation has declined while lower-carbon alternatives have increased. In addition, electric cars are becoming more efficient. For example, the Nissan Leaf and the Chevrolet Volt, have undergone efficiency improvements to the original 2010 models, and other, more efficient BEV models, such as the most lightweight and efficient BMW i3, have entered the market.^[25][26]

United Kingdom

A study made in the UK in 2008, concluded that electric vehicles had the potential to reduce carbon dioxide and greenhouse gas emissions by at least 40%, even taking into account the emissions due to current electricity generation in the UK and emissions relating to the production and disposal of electric vehicles.^[27] The savings are questionable relative to hybrid or diesel cars. (According to official British government testing, the most efficient European market cars are well below 115 grams of CO₂ per kilometer driven, although a study in Scotland gave 149.5 gCO₂/km as the average for new cars in the UK.^[28]) But because UK consumers can select their energy suppliers, it also depends on how 'green' their chosen supplier is in providing energy into the grid. Unlike other countries, in the UK a stable proportion of the electricity is produced by nuclear, coal and gas plants. Therefore, there are only minor differences in the environmental impact over the year.^[5]

Germany

In a worst-case scenario where incremental electricity demand would be met exclusively with coal, a 2009 study conducted by the World Wide Fund for Nature and IZES found that a mid-size EV would emit roughly 200 g(CO₂)/km (11 oz(CO₂)/mi), compared with an average of 170 g(CO₂)/km (9.7 oz(CO₂)/mi) for a gasoline-powered compact car.^[29] This study concluded that introducing 1 million EV cars to Germany would, in the best-case scenario, only reduce CO₂ emissions by 0.1%, if nothing is done to upgrade the electricity infrastructure or manage demand.^[29] A more reasonable estimate, relaxing the coal assumption, was provided by Massiani and Weinmann taking into account that the source of energy used for electricity generation would be determined based on the temporal pattern of the additional electricity demand (in other words an increase in electricity consumption at peak hour will activate the marginal technology, while an off peak increase would typically activate other technologies). Their conclusion is that natural gas will provide most of the energy used to reload EV, while renewable energy will not represent more than a few percent of the energy used.^[30]

Volkswagen conducted a life-cycle assessment of its electric vehicles certified by an independent inspection agency. The study found that CO₂ emissions during the use phase of its all-electric VW e-Golf are 99% lower than those of the Golf 1.2 TSI when powers comes from exclusively hydroelectricity generated in Germany, Austria and Switzerland. Accounting for the electric car entire life-cycle, the e-Golf reduces emissions by 61%. When the actual EU-27 electricity mix is considered, the e-Golf emissions are still 26% lower than those of the conventional Golf 1.2 TSI.^[31] In 2014 in Germany, 28 percent of whole electricity was renewable energy produced in Germany.

France and Belgium

In France and Belgium, which have many nuclear power plants, CO₂ emissions from electric car use would be about 12 g/km (19.3 g/mi).^[32] Because of the stable nuclear production, the timing of charging electric cars has almost no impact on their environmental footprint.^[5]

Emissions during production

Several reports have found that hybrid electric vehicles, plug-in hybrids and all-electric cars generate more carbon emissions during their production than current conventional vehicles. Study of electric car production in Malaysia estimated a compact electric car production release 5,791 kg CO₂ per unit against conventional vehicles 4,166 kg CO₂,^[33] but still have a lower overall carbon footprint over the full life cycle. The initial higher carbon footprint is due mainly to battery production.^[5] As an example, the Ricardo study estimated that 43% of production emissions for a mid-size electric car are from the battery production.^[34]

Environmental impact of manufacturing

Electric cars are not completely environmentally friendly, and have impacts arising from manufacturing the vehicle.^[35][36] Since battery packs are heavy, manufacturers work to lighten the rest of the vehicle. As a result, electric car components contain many lightweight materials that require a lot of energy to produce and process, such as aluminium and carbon-fiber-reinforced polymers. Electric motors and batteries add to the energy of electric-car manufacture.^[37] Also, the magnets in the motors of many electric vehicles contain rare-earth metals. In a study released in 2012, a group of MIT researchers calculated that global mining of two rare-earth metals, neodymium and dysprosium, would need to increase 700% and 2600%, respectively, over the next 25 years to keep pace with various green-tech plans.^[38] Substitute strategies introduce trade-offs in efficiency and cost.^[37] The same MIT study noted that the materials used in batteries are harmful to the environment.^[39] Mining and processing of metals such as lithium, copper, and nickel uses energy and can release toxic compounds. In regions with poor legislature, mineral exploitation can increase risks further. The local population may be exposed to toxic substances through air and groundwater contamination.^[37]

A paper published in the Journal of Industrial Ecology named "Comparative environmental life cycle assessment of conventional and electric vehicles" begins by stating that it is important to address concerns of problem-shifting.^[40] The study highlighted in particular the toxicity of the electric car's manufacturing process compared to conventional petrol/diesel cars. It concludes that the global warming potential of the process used to make electric cars is twice that of conventional cars. The study also finds that electric cars do not make sense if the electricity they consume is produced predominately by coal-fired power plants.^[41] However, the study was later corrected by the authors due to overstating the environmental damage of electric vehicles; many of the electric vehicle components had been incorrectly modelled, and the European power grids were cleaner in many respects than the paper had assumed.^[42]

In February 2014, the Automotive Science Group (ASG) published the result of a study conducted to assess the life-cycle of over 1,300 automobiles across nine categories sold in North America. The study found that among advanced automotive technologies, the Nissan Leaf holds the smallest life-cycle environmental footprint of any model year 2014 automobile available in the North American market with at least four-person occupancy. The study concluded that the increased environmental impacts of manufacturing the battery electric technology is more than offset with increased environmental performance during operational life. For the assessment, the study used the average electricity mix of the U.S. grid in 2014.^[43][44]

References

External links

• Dissected, Dan Roupe, September 2015.
• Shade's of Green - Electric Car's Carbon Emissions Around the Globe, Shrink that Footprint, February 2013.
• NOW on PBS investigates if electric cars will bring a new global climate change plan
• Transport Action Plan: Urban Electric Mobility Initiative, United Nations, Climate Summit 2014, September 2014