Week 6

 CV vs EV - CO₂ Emissions

Introduction: 

The largest battle waged between automobiles is that of the conventional gas-powered vehicles (CV) and the newly established electric vehicle (EV) market.  Unlike hybrids, EVs do not burn any gasoline and therefore have zero operating emissions.  The drawback of this is a limited range and a required charge time once the batteries are empty.  Many people like to think that EVs are truly zero emission vehicles, however that is not the case.  EV buyers must take into consideration where the electricity for charging their car is coming from and the associated greenhouse gas emissions with that process.  

1. What goes into CV emissions?

Before the vehicle is used, the fuel must be pulled out of the earth and turned into gasoline.  The steps of this process are broken up below.

• Recovery of crude oil -- 1,862 grams per mmBtu
• Transportation to oil refineries -- 1,689 grams per mmBtu
• Gasoline Refining: Feed Inputs -- 3,664 grams per mmBtu
• Gasoline Refining: Intermediate Combustion -- 7,722 grams per mmBtu
• Transportation and Distribution -- 521 grams per mmBtu
• Total: 15,458 grams per mmBtu

Additional information is needed to fully represent the emissions of the vehicle. When comparing CVs and EVs, we are assuming that all production processes other than those involving the battery are generally the same.  

• Production of Lead Acid Battery -- 4,392 grams per battery (assumption of 36 lb battery)
• We assume the average fuel efficiency to be 27 miles per gallon (MPG) which is a US average figure that includes newly produced vehicles as well as vehicles that have been on the roads for several years (the average for all new vehicles would be much higher)
• We assume the average lifetime mileage of cars to be about 200,000 miles
• Energy of one gallon of gasoline -- 125,000 Btu
• We assume the average carbon dioxide emissions per mile to be 368.4 grams (EPA)

Finally, we can calculate the total carbon dioxide emissions for CVs using the bold figures above.

(1 gallon / 27 miles) * (200,000 miles / 1 lifetime) * (125,000 Btu / 1 gallon) *

(15,458 grams / 1 mmBtu) * (1 mmBtu / 1,000,000 Btu) = 14,312,176 grams / lifetime

(368.4 grams / 1 mile) * (200,000 miles / 1 lifetime) = 73,680,000 grams / lifetime

Total CV Emissions: 14,312,176 grams + 73,680,000 grams + 4,392 grams = 87,996,568 grams 

2. What goes into EV emissions?

Before you can charge your electric vehicle at your home or at a public charging station, the electricity must first be created.  Information regarding the process of calculating EV emissions is below.  The same assumptions we made about the general production of a car that we made above are made here.

• Electricity provided to consumer -- 558 grams per kWh
• Production of lithium ion battery -- 53,635 grams per battery
• We assume the average EV-efficiency to be about 33 kWh per 100 miles of use
• Once again, we assume a total accumulated mileage of 200,000 miles over the car's lifetime 
• We do not consider the replacement of battery cells over time as their deterioration varies from user to user and from car to car (improving technology also reduces the necessity of this)

With those values, we can calculate the total carbon dioxide emissions from EVs.  

(33 kWh / 100 miles) * (558 grams / 1 kWh) * (200,000 miles / 1 lifetime) = 36,828,000 grams

Total EV Emissions: 36,828,000 grams + 53,635 grams = 36,881, 635 grams

Conclusions:

While these calculations have debunked the idea that EVs are zero emissions vehicles, it has proven that EVs are a cleaner choice of automobile provided your budget can handle the high cost of the technology and your daily commute is short enough to accommodate the limited range.  As EVs see more investment in research and development, it is very possible these values will change and the EV will become a practical and environmentally friendly choice for everyone.  

References:

Location of researched emissions value per mile driven
https://www3.epa.gov/otaq/consumer/420f08024.pdf

Average US vehicle efficiency
http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_04_23.html

Information on EV efficiency
http://www.greencarreports.com/news/1082737_electric-car-efficiency-forget-mpge-it-should-be-miles-kwh

Common mileage information for today's automobiles
http://business.time.com/2012/03/20/what-you-only-have-100k-miles-on-your-car-thats-nothing/



- Alexander Hall

  abh53@drexel.edu