Amidst all the scientific studies, academic research and political rhetoric, the debate continues on how much effect converting to electric cars – powered from our existing electrical grid – will have on the emissions of greenhouse gasses – CO2. With the proliferation of these studies, some tracing CO2 contributions all the way back to the first exhalation of breath from the dinosaurs, it can be hard for the average rocket scientist, let alone mere mortal, to come to a conclusion. Therefore, I have decided to shun the scientific calculator, eliminate the variables, and do a simple, empirical analysis of their direct impact. |
First, the Coal burning Power Plants.
We are fortunate here in that someone, most likely math challenged, actually had the good sense to measure the CO2 output of power plants. It has been measured and confirmed many times since. Ends up the average Coal burning power plant emits 2.17 pounds of CO2 for every kilowatt-hour it produces. (EIA) Now, coal makes up only 48% of our electrical generation. Natural Gas produces 20% and it also emits CO2 (1.4 pounds per kWh). But, 30% comes from nuclear and renewable sources. So, taken together, our national electrical supply generates, on the high side, 1.51 pounds of CO2 per kWh.
Now for the Cars.
Basic Chemistry tells us that burning 1 gallon of gasoline emits 19.4 pounds of CO2. It also tells us, based on BTU content, there are 36 kWh of energy in that gallon of gas.
One place where all the research gets bogged down is trying to account for the varying efficiencies of our automotive contraptions. Automotive IC (Internal Combustion) engines are anywhere from 15 to 28% efficient in average driving. Well, for our worst case, empirical study, I am going to assume the most efficient – 28%. The most efficient means it is the most work we get for every globule of CO2 emitted. Indeed, the meaning is that 28% of the BTUs in that gallon of gas will get turned into useful, mechanical work. All the rest are wasted as heat. There are 124,000 BTU’s, give or take, in a gallon of gas, so at 28% efficiency 34,720 of them or 10.16 kWh, are actually used for something productive. Yet, we still created 19.4 pounds of CO2 burning that gasoline. A little math, and the emissions result for our car is 1.90 pounds of CO2 per kWh of work produced. Note that at the other end of the scale – at 15% efficiency - those numbers would be 5.4 kWh of useful work, and 3.59 pounds of CO2 per kWh.
Although this article is not about CO2 per mile (remember, simple), for the sake of reference, both the Chevy Volt, and my Chevy Malibu use approximately .240 kWh for each mile at a </i>steady<i> 60 Miles Per Hour. The Tesla Roadster claims to use .217. The Prius is about .220. Your dumptruck, I don't know. However, we do not need to factor in the relative mileage of different vehicles to determine the absolute CO2 emissions potential. Replacing a similar gasoline vehicle, with a similar electric vehicle will still result in similar energy needs.
The answer please!
The results show that burning gasoline in an ICE powered car creates anywhere from 21% to 58% more CO2 than getting the same amount of energy from our electric grid for the same size and shape car. And, that point is important.
The other way many of these studies tend to confuse the issue is trying to relate everything to mileage – like pounds per mile. That is truly putting oranges in an apple barrel. The matter of mileage is irrelevant when comparing similar size and shape vehicles where the only difference is the source of power. They will both use the same amount of energy, which here is expressed in Kilowatt-hours. Regardless of whether they are powered by electricity, gasoline, or soda pop. The difference lies in the source of the power.
Now granted, if you replace your dump truck with a compact car, you will be emitting less CO2, but that is true of either power source, because your small car uses less energy than a dump truck. The reverse would also be true, although good luck finding an electrically powered dump truck.
It should be clear by now that by replacing a gasoline powered ICE vehicle with an electric one, for the same amount of power at the wheels, we would reduce CO2 GHG emissions by anywhere from 21% to 58% - even with our existing electrical supply. And, in fact, those who have bothered to reduce some of the complex, often politically motivated and artistically spun, studies down to their basic conclusions have found exactly the same thing.
Our Natural Gas supply – The numbers game.
It does not take long to realize that there are more varied predictions on how much Natural Gas this country has, than there are flavors in your local store’s Ice Cream freezer. And, unlike that Ice-Cream, many of the natural gas numbers leave a sour taste in the mouth. Which numbers are correct, which are biased towards an agenda, and which are just plain old pie in the sky – (a-la-mode)?
Now, I am not a geologist so I cannot offer my own independent conclusions, although that does not seem to inhibit many others. What I can do, is to look at those numbers, compare them, and attempt to derive some sensible compromises based on reality, technical awareness, and just plain common sense.
First, lets look at the numbers reported by what are considered by most to be credible and reliable sources. Unlike some, these sources also have facts and figures to back up their analysis.
The United States Geological Survey in their latest report ( Dec 2008) says we have 742 Trillion cubic feet of proved conventional reserves, 378 Trillion Cubic feet of Unproved reserves, and 743 Trillion Cubic Feet of technically recoverable Unconventional resources (Shale and tight gas).
Ref: http://certmapper.cr.usgs.gov/data/noga00/natl/tabular/2008/summary_08.pdf
The Energy Information Administration in Jan 2007 puts US total recoverable conventional reserves at 211 proved and 373 unproved, and technically recoverable unconventional reserves (Proved and unproved) at 1,366 Trillion Cubic feet. Ref: http://www.eia.doe.gov/oiaf/aeo/assumption/pdf/oil_gas.pdf
Already we have some serious disagreement, although both sources agree on Unproved Conventional gas. The difference in the unconventional reserves likely centers around the definition of “Technically recoverable”.
The big difference comes in the proven reserves. For some reason the EIA comes up with a very low figure for this, (I did the math 3 times). Yet, both sources add up to roughly the same total of 1,800 Trillion Cubic feet of reserves.Now, lets turn to the Natural Gas Association. First of all, they agree with me that there is a wide disparity in these assessments. I feel so good! They base their own assessment on EIA data as above with total proven reserves at 211 Trillion Cubic Feet, and a total of 1,536 Trillion Cubic feet of unproven reserves.
http://www.naturalgas.org/overview/resources.asp (Very useful page!).
OK. The above references, ignoring what they consider to be technically recoverable, all predicate that we have a total of about 1,800 Trillion Cubic Feet of Natural gas reserves in the US. Now, I could fill a few pages with references to other reports that “grow” this estimate in leaps and bounds. It all culminated for me in a purported report from JP Morgan Chase that our reserves are NOW 8,000 Trillion Cubic Feet. I have not been able to find the actual report, only references to it. It does strike me that many of these inflated numbers are coming, not from geologists, or even energy companies, but from institutions with a financial stake in the trading of Natural Gas. Hmmmm.
I would like to point out also, that there is wide disparity on how much of that gas can be recovered. Certainly not all. According to the Natural Gas association, about 10% of the unconventional. Many sources put it closer to 30 percent. So far shale gas production in the Barnett shale has not lived up to expectations, and they are recovering about maybe 35% of what they thought they would. http://www.aspousa.org/index.php/2009/08/lessons-from-the-barnett-shale-suggest-caution-in-other-shale-plays/
One final issue I would like to address. A common talking point is how many years this supply of Natural Gas will last us. First some baseline numbers. We used 22 Trillion Cubic Feet of Natural Gas last year. That is 1.8 TCF per month, or 60 Billion Cubic Feet a Day! In the same month we will use about 11 Billion gallons of gasoline, 5 billion gallons of diesel fuel and 342 Million-Megawatt hours of electricity.
Well, if we change nothing, and manage to recover all 1,800 TCF of our natural gas, we are good for 81 years. If we manage to only recover 35%, then about 28 years worth.
But, what if we try to replace our gasoline use with natural gas? That 11 Billion Gallons of gasoline a month is about 1,364 trillion BTUs. Equivalent to 1.3 trillion Cubic Feet of Natural Gas, increasing our consumption by 72%. If we add in the diesel, that would equal .65 Trillion more Cubic feet. So replacing our transportation fuel would more than double our consumption of Natural Gas, and reduce our remaining supply to 14 or 40 years, depending on your optimism level. http://www.theoildrum.com/node/5615.
Let’s replace electricity from coal instead. Coal supplies 48% of our electricity, or 164 Million-Megawatt hours a month. Each one has 3.414 BTUs of energy. So, that is 560 Trillion BTU’s. (I checked the decimal point). It would require .6 trillion Cubic Feet of Natural gas to replace our coal. About a 33% increase, assuming the power plant efficiency is the same – it is close. That would make our natural gas last anywhere from 19 years to 54 years, again depending on how much natural gas we can actually recover.
Finally, I would recommend reading this report on The Oil Drum. It addresses some of these points, and also makes the point that the whole natural gas reserves picture is steeped in unfounded numbers and hype.
http://www.theoildrum.com/node/5676
As for me, I think I will have some Ice Cream.
Posted at 09:47 PM in Commentary, Natural Gas, Technicalities, Transportation | Permalink | Comments (18)
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