It matters how the electricity is made

Broadly speaking, most electric cars sold today tend to produce significantly fewer planet-warming emissions than most cars fueled with gasoline. But a lot depends on how much coal is being burned to charge up those plug-in vehicles. And electric grids still need to get much, much cleaner before electric vehicles are truly emissions free.

One way to compare the climate impacts of different vehicle models is with this interactive online tool by researchers at the Massachusetts Institute of Technology, who tried to incorporate all the relevant factors: the emissions involved in manufacturing the cars and in producing gasoline and diesel fuel, how much gasoline conventional cars burn, and where the electricity to charge electric vehicles comes from.

If you assume electric vehicles are drawing their power from the average grid in the United States, which typically includes a mix of fossil fuel and renewable power plants, then they’re almost always much greener than conventional cars. Even though electric vehicles are more emissions-intensive to make because of their batteries, their electric motors are more efficient than traditional internal combustion engines that burn fossil fuels.

Natural gas vehicles (NGVs) can offer an array of economic and environmental benefits to California residents. These may include the economic benefits of a low-cost, domestic fuel, developing a market for green jobs, improving regional air quality, reducing greenhouse gas emissions, reducing our dependence on petroleum and providing a pathway to a hydrogen economy.

Environmental Benefits

Natural gas vehicles can have an immediate and positive impact on the issues of air quality, U.S. energy security and public health. Here are some key benefits of using natural gas as a transportation fuel.

NGVs are Clean

NGVs are some of the cleanest vehicles in commercial production today, and produce only 5-10 percent of the emissions allowable, even by today's most stringent standards. NGVs produce 20-30 percent less greenhouse gases than gasoline- or diesel-powered vehicles.

Overall, natural gas is one of the cleanest burning alternative fuels available today. NGVs can reduce nitrogen oxide (NOx) emissions and reactive hydrocarbons which form ground-level ozone, the principal ingredient of smog, by as much as 95 percent. NGVs can also reduce emissions of carbon dioxide by as much as 30 percent, carbon monoxide (CO) by 85 percent and carcinogenic particulate emissions by 99 percent.

Reducing Greenhouse Gas Emissions

The use of compressed natural gas (CNG) in place of gasoline or diesel can help reduce greenhouse gases.

A 2008 "well to wheels" analysis conducted by TIAX, LLC concludes that natural gas offers up to a 30 percent reduction in greenhouse gas (GHG) emissions for light-duty vehicles, and as much as a 23 percent reduction for medium- to heavy-duty vehicles, when compared with gasoline and diesel. The chart below shows the amount of C02 that has been displaced since 1999 by SoCalGas? customers using vehicles powered by CNG instead of diesel. In 2008 alone, that number was almost 229,000 metric tons of CO2!

Clearly, NGVs present one of the cleanest choices for today and tomorrow.

LNG is a natural gas (predominantly methane, CH4) that has been converted to liquid form for ease of storage or transport. After being liquefied, it takes up about 1/600 the volume of natural gas in the gaseous state and about 45% the weight of water in equal volume. As a cleaner energy, natural gas is increasingly favored. LNG is proposed to be the prior choice of alternative fuels in many countries, for example, United States, Canada, Europe, and China. As a result, the ratio of natural gas in energy supply increases rapidly. While compressed natural gas (CNG) is just suitable for light-duty vehicles, LNG can be used in road transport, such as heavy-duty trucks and buses. In China, CNG buses and LNG buses were introduced into the bus fleet in Beijing in 1999 and 2012, respectively. After that, more and more cities in China have swift some diesel buses to LNG buses, for example, Guangzhou, Xiamen, and Shenzhen. Heavy-duty vehicle, whose total mass is 14 tons or more, is the main object of promoting LNG vehicles in Shenzhen road freight. Different from light-duty vehicle using diverse fuel (e.g. gasoline, diesel, CNG, and electric), heavy-duty vehicle uses diesel or LNG because the fuel’s energy density must be high enough to meet its power requirement. There are three main types of LNG heavy-duty vehicles in Shenzhen, namely, container tractors, engineering dump trucks, and engineering mixers.

Due to the raising economy development of Shenzhen, environmental problems brought by road transport have become more serious. Promoting liquefied natural gas vehicle in the road freight is a key to reduce emissions, change the direction for road freight development, and build a resource-saving society. This article studies the application of liquefied natural gas vehicle in Shenzhen in-depth through official data sets, field investigation, expert consultation, and so on. Economic benefit analysis shows that liquefied natural gas vehicle has the advantage of saving considerable fuel costs for enterprises. Moreover, the Monte-Carlo method is used to evaluate the economic benefits considering a lot of factors. The economic analysis shows that the liquefied natural gas vehicle is more affordable than the diesel vehicle. Finally, the current issues of liquefied natural gas vehicles on the promotion are discussed and some advices are proposed to improve air quality and reduce emissions.