Results and Conclusions

Energy Consumption

We will begin our discussion of our findings by looking at the energy consumed by each type of system over it's lifetime.  This is an important point to consider because it looks at the total volume of energy, in millions of Btus, which allows us to quantify the situation.  Much like how we will consider the emissions with SEC, the energy consumption values of each system will be considered.  Unlike SEC however, these values will be taken for exactly what they are, and will not be weighted in any fashion.

Table 1 - Energy consumption values in mmBtu for gasoline.

Above in Table 1, are the energy consumptions of the various automotive life cycles.  All of the values are from the GREET model and represent all of the various tasks included in a vehicle's operation.  This table also shows the values for multiple years, for the purpose of illustrating the trends which will most likely be observed.  As we can see, gasoline is following a promising trend which conveys a decrease in energy exerted to make, fuel, and operate a vehicle.  To get a better idea of how all of these numbers fit together, and to compare them to those of the other systems, please take a look at Figure 1 below.

Figure 1 - The trends of the energy consumption of each of the test systems.  These values represent the summation of all of the processes involved in the vehicle's life cycle.

From Figure 1 we can get a much better understanding of the nature of these energy consumption values.  Looking at a hydrogen fuel cell vehicle in 2007, we can see how the efficiency was comparable to a gasoline powered vehicle.  This does not mean that the two systems had the same mile per gallon rating as one another, but that both of them consumed the same amount of energy being built and operated in that year.  Moving forward three years, hydrogen jumped below all of the other systems as it's efficiency increased.  From the breakdown of hydrogen's consumption, this jump is attributed to the sudden decrease in the amount of energy required to render hydrogen gas.  In 2007, hydrogen spent 2261 Btu/mile which was cut down to 1428 Btu/mile three years later.  This is an excellent example of how any one of these systems could be changed by technological advancement to the point where it could drastically improve the plausibility of that system's integration into the market.

SEC Analysis

Table 1 - GREET results for the emissions of a gasoline vehicle in 2010

We will begin our discussion of our findings by looking at the results of SEC.  As previously discussed, SEC is the calculator which we created to better interpret the scale of a vehicle's emissions.  Below in Table 1 we can see some of the emission values provided by GREET for a gasoline vehicle.  All of the values in the table represent the emissions in grams per mile of vehicle operation.  For example, the Fuel column represents the grams of each emission that are created by the rendering of the fuel, for every mile that a gasoline powered vehicle will travel.  In SEC, we multiplied this value by 100,000 miles to get the total mass of each emission over the entire assumed life of this car.  For those who are worried about it, these values are for 2010, and represent the typical fuel economy of a car for that year.  We will be looking at extrapolations to consider these values in the future later in this discussion.

Looking now at Figure 1, we will see the final SEC calculation for the same vehicle in 2010.  In the calculator the numbers from Table 1 are weighted by their emission multiplier, to emphasize the more potent chemicals.  The value of most importance from the Figure is the Total Vehicle Emission Score.  For gasoline, the value in 2010 was equal to 438.8.  With this value in hand, the other systems were also considered in the same fashion, giving us a scale from which to compare them all by.  The other SEC windows for 2010 are provided in the Appendix.

Figure 1 - SEC calculation for the gasoline system in 2010

The results of SEC are provided in Table 2 below.  The values in the table were all derived in the exact same fashion as the gasoline system above.  Using these scores as representation of the system's emission impact, the influence that each type of fuel source plays on the emissions of the automotive industry collectively, becomes a bit more clear.  It is important to mention that each of these systems do not hold the same percentage of the automotive market, and cannot be treated equally as culprits in emission generation.  With that said, knowing that the vast majority of the cars on the road today are powered by gasoline, we can begin to see why the demand for alternatives is on the rise.

Table 2 - The 2010 SEC results

Table 2 brings up another interesting revelation about the state of the industry:  Why is an electric car the fourth worst fuel system for an automobile?  Looking at the SEC calculation for the electric system (Appendix), we can see that electric cars match hydrogen powered ones perfectly for system usage emissions.  The problem arises when it comes time to recharge the system, and it is plugged into the electric power grid.  While the system itself generates almost nothing, the process by which the electricity is generated expels enough waste into the air to ruin it's score.  This issue is dealt with in a hybrid vehicle by keeping all electric generation self-contained, making it almost completely independent of the power grid.  While a hybrid still spews out emissions, it's improved fuel economy and virtual independence from outlets gives it the lead over the electric car.

So, with that startling news behind us, let's take a look at the breakdown of each system.  Figure 2 shows the SEC score contributions of each of the processes evaluated.  This graph plainly illustrates the massive influence that the fuel rendering stage has on an electric car's score.  Perhaps even more interesting than that, is the graph of the bio-fuel system which is clearly worse than all of the others.  The trick to the bio-fuel's success is that E85, ethanol which is primarily derived from corn, consumes so much carbon dioxide during the Feedstock stage.  The feedstock stage for E85 includes the harvest of the corn, but more importantly, the entire duration of the growth of the crop.

Figure 2 - Composite graph of the SEC scores for 2010

So our SEC results leave us with some interesting conclusions.  In 2010, the most "green" system was  hydrogen, and all of the others were fairly close behind.  Perhaps, more importantly than that, was the fact that the systems that we had thought were fantastic for the environment, proved not to be.  In this era of changing things for the better, we as consumers have been mislead from the truth about our standards.  At this point, electric vehicles are no longer the image of the perfect and final solution to the automotive problem, and our results prove that.  However, the most significant point of SEC was to bring these truths to the forefront of the discussion.  Now, instead of looking at the fuel economy of a car, people should really be considering the impact of the network which supports its' operation.  If a consumer purchases a electric car to try and achieve some righteous ideal that they have, they should be made aware of what is going on behind the scenes.  So, the new goal of the automotive industry is to improve their vehicles' impact from cradle to it's grave.