Efficiency Efficacy


With so much talk now of efficient personal transportation, it is an issue that remains on my mind throughout most of the day. Regarding personal transportation, I think most often of cars vs. bicycles. In past posts I’ve praised bicycles for being the most efficient means of transportation as well as the least expensive. However, I wanted to investigate this claim further.

I am calling an energy efficiency duel: an automobile vs. a human powered bicycle.

Fueling the Fire

Cars burn gas. Humans burn food. Seems simple enough, however there is an interesting ratio that seldom is discussed when talking about energy efficiency; the net energy value.

This is a hot and interesting topic for energy producing companies and ties directly into this discussion.

NEV: Gasoline

Gasoline is a distillate of crude petroleum oil. With every gallon produced there is an energy expenditure. The energy contained in the gallon of gas minus the energy expended producing it is the NEV. It can be written as:

Eproduction – Egas = NEV

-or more simply-

Ein- Eout = NEV

Now this is a very complex calculation when one takes all variables into account.

Energy Expenditures

  • Drilling
  • Crude transport
  • Production
  • Employee Transport
  • Employee food
  • Product transport and delivery
  • Product use

It becomes apparent that the energy use to bring the product to a state of utilization is a non-linear complex web of energy expenditures in which the calculation is not a hard value, but rather a range. Another interesting aspect of the NEV of gasoline is the steadily increasing price of production, which in turn lowers the NEV. This is a result in part of depleting oil fields and more difficult extraction of raw material.

There are several studies that investigate the NEV of gasoline, many of them compare the NEV of gasoline to biomass based liquid fuels (ethanol, biodiesel, etc.).

A conclusive study indicates the NEV ratio (in/out) of gasoline to be 1.23/1.00. This value is worsening all the time as petroleum fuel and electricity generation becomes more expensive and oil fields are being depleted, a compounding problem resulting from an interesting positive feedback loop.

NEV: Food

Calculating the NEV of gasoline is a very complex issue involving many variables. Food NEV is even more complex being a commodity with a broad range of possible forms. In order to simplify this daunting task, I will take into account a familiar food to all of us; the great Big Mac. I am very familiar with the energy composition of a Big Mac as discussed in a previous post using The Incredible Hulk as the consumer. If you hate math, you should scroll down to the Energy Efficacy section.

Big Mackin’

The Big Mac with cheese contains 704 kcals or 3 MJ of energy. In order to account for the NEV of a complex hybrid meal, we must break the burger down to its constituent sub systems:

Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun

Break it down:

  1. Beef patties – 180 kcal
  2. Cheese – 120 kcal
  3. Buns – 255 kcal
  4. All the rest – 149 kcal

Look here for a complete list of nutrition facts from McDonald’s

Let’s focus on the funnest, most energy intensive element of the Big Mac for some simple calcs; the BEEF.

Beef Patties

According to Michael Pollan in Omnivore’s Dilemma, the conversion rate for cow’s digestive system is 7:1. That is, 7 pounds of grain for every 1 pound of meat.

Now this becomes complicated to figure out the energy input of raising cattle because of the complex interactions from growing, processing and transporting the animal feed. Then transporting cows, slaughtering, processing and transporting meat. So I will use Michael Pollan’s numbers to speed up the process.

On page 83-84, Michael Pollan explains that his cow, number 534, will consume the corn equivalent to 35 gallons of oil during his lifetime.

Then on page 45 he states ”between a quarter and a third gallon of oil to produce a bushel of corn”

A bushel of corn weighs 56 lbs

A kilogram of oil contains 45 MJ of energy

For your two beef patties, at 1/4 lb total, took about 2 lbs of corn (based on conversion rate of cow).

Let’s calculate:

2 lbs corn = 0.0357 bushels

1/3 gal oil = 12 kCal

[oil denisty - .9 kg/L]  [3.73 L/gal] [crude oil energy content - 45 MJ/kg] [.239 J/cal] = 36.1 Mcal/gal oil = 36.1 kCal/gal

Big Mac beef takes – 12 kCal * 0.0357 bushel/burger = 430 Cal of oil to grow

It takes 430 Cal of oil to grow the corn necessary to grow the meat necessary for a Big Mac.

Shipping

Big Mac beef patties don’t sprout from the earth in burger land, like some may have thought. That’s why we’re having this discussion, to learn stuff. No, the cows are slaughtered, the meat is processed and the meat is shipped which brings about an interesting fact. McDonald’s, being the international icon that it is, sells a commodity throughout a land of vast expanse. However, that commodity is made from a material that can severely vary from locale to locale, cow. Since the same quality is demanded in “Boston and San Diego”, “McDonald’s cut back from using about 175 different meat suppliers to using only five” states Eric Schlosser from his Fast Food Nation. This makes it easy to speculate where your Big Mac meat is coming from (it also accounts for massive beef recalls), which is likely from Dakota Dunes, South Dakota from Tyson Fresh Meats Inc. I live in the Boston area, so lets do some calcs!

Big Mac Truck

Big Mac Truck

Your average pallet of frozen meat products weighs about 800 lbs. The normal length for a commercial trailer is 53′, like many of the delivery trucks services McDonald’s. In this size trailer, if the distribution facility is operating at peak efficiency, the trailer will be filled with 26 pallets, weighing in at 20,800 lbs. With an average size load, these tractor-trailers average about 5-7 miles per gallon.

For the purposes of this discussion, lets say the Micky D’s truck picks up its 26 pallets of frozen patties from Dakota Dunes and drives directly to the heart of the Bean (Town, that is).

The entire trip is 1501 miles. If our driver doesn’t let his truck idle over night, he should average about 6 MPG. Once in Boston, our driver has burned 250 gallons of (low sulfur) diesel fuel.

If our diesel has a Higher Heating Value (HHV) of about 38.6 MJ/L or  33,300 kcal/gal, then our driver consumed 8.25 Million kcal on his drive over.

So, the calorie content of the beef in his trailer is about 24 Million kcal. A 4:1 transport energy to food energy ratio, pretty efficient I’d say, especially since 24 is the highest number.

The figure we really want is the calories of fuel input per Big Mac beef content.

20,800 pounds of meat is 83,200 Big Macs worth of meat. At 8.25 million diesel calories, each Big Mac needs about 100 diesel fuel calories for transport.

Keepin’ it cool

Our little beef patties need to stay cold. At frozen temperatures, the reefer trailer (industry jargon from refrigerated trailer, not weed) is burning about 1 gal an hour to keep it real nice and fresh. Say our driver makes the drive in great time of 24 hours and stops for 6 to sleep and shower. In 30 hours, we’ve burned an additional 30 gallons of diesel to keep it cool.

That’s another 1 Million diesel kcal, about another 13 kcal per big mac.

Other Fun Energy Uses

In addition to growing, transporting and processing raw materials, there are several other areas in which there are significant energy expenditures. About 1/5 of the petroleum products consumed in the US is for our food (pg. 83). A significant amount of oil is imported from the middle east and “therefore defended by the US military, another never-counted cost of cheap food” (pg. 83).

Thank you, Michael Pollan

It is interesting to run through these calculations, but I’m not trying to reinvent the wheel so I will use some calcs already published by Michael Pollan in his Omnivore’s Dilemma. Because afterall, it is taking a significant amount of energy for me to write this, even if I am on a semi-new macbook pro and eat predominately vegetarian.

In chapter 7: The Meal, Michael, his wife and his son, consume a meal from Micky D’s. Michael orders a classic cheeseburger, large fries, and a large Coke (1110 calories). His son orders chicken nuggets, a double thick shake and an order of large fries (2170 calories). His wife orders a Cobb Salad. The meal totals 4510 calories and $14. He states, though doesn’t directly calculate, that the meal itself consumed at least 10 times that amount of calories in oil, about 1.3 gallons.

NEV: Micky D’s

On a good day, we can say that the NEV of Micky D’s is 10:1.

I would say I wasn’t too far off with my calcs. For the beef alone, my ultra-conservative estimate brought us to 543 kcal of oil for 180 kcal of food.

Recall this does not include:

  • CAFO operations
  • processing
  • steer transport
  • employee transport
  • employee room and board
  • any of the other Big Mac ingredients (like cheese and bread)

and we are already at a 3:1 calorie in/out ratio.

Efficiency Efficacy

Now that we trudged through those boring calcs, we can finally make the comparison:

is a bike really more efficient than a car?

We must set up a test scenario for this comparison.

Let’s say you’re commuting to work. Work is 5 miles away along a dead flat grade and there are no traffic lights and there’s minimal traffic. The motor vehicle speed limit is 35 mph and the temperature is a nice 70 degrees Fahrenheit and you’re ballin’ out and driving an Audi A4 1.8t.

Let’s get some important numbers straight:

2002 Audi A4 1.8t

1977 Nishiki Prestige – Refurbished and Converted to Fixed Gear

  • Fuel Type: Human
  • Rated Efficiency: ~95%

1985 Semi-Fit Guy

Effective Efficiency Competition

Let’s calculate how much energy is actually consumed by these two modes of transportation!

The Audi

I know from experience that one can achieve 30 mpg (this vehicle is equipped with a MPG calculator in the display) if one is easy on the accelerator pedal in this car, especially on a flat road with little stops and starts at low speeds. Let’s say today we’re feeling particularly bad for the earth and taking it easy on her. We definitely don’t want to break the law so we set the cruise control at exactly 35 mph.

If we achieve 30 miles per gallon over the 5 miles traveled, we have burned 1/6 gallon. Gasoline contains 45-48.3 MJ/kg which translates to about 32 MJ/L or 29000 kcal/gal.

1/6 gallon is 4833 kcal worth of gasoline and will cost $0.47.

However, in reality we now know that the NEV of gasoline is 1.23, so our trip really expended 5945 kcal.

In order to account for all energy expenses, we should account for the energy burned by the driver, who is also semi-fit.

This trip will take 10 minutes. At 73 kcal/hr, thats 12 kcal.

Audi: 5957 Cal (light foot) – $0.47

What if we’re heavy on the pedal?

Speeding around in the 3550 pound A4 like a frat boy with his face on fire will consume about 1 gallon per 20 miles (20 mpg), even more if you’re really goosin’ it.

Our trip will consume approximately 50% more fuel.

Audi: 8929 Cal (heavy foot) – $0.71

The Semi-Fit Guy

Our semi-fit guy has been biking for little bit now, so he’s in decent shape and can maintain 16 mph for the entire ride to work, not bad on a fixie. He is fully fueled from the Big Mac and large Coke he had earlier (1014 kcal, ~$5).

So, our man is on the road for 19 minutes. Using several (287) different (243) calorie (248) calculators we come up with an average of 259 kcal expended to propel him to his destination.

Our Japanese two-wheeled transport system transfers only 95% of semi-fit’s leg power to the road, so it will actually take 5% more than 259 kcal. 259 kcal / .95 = 273 kcal

Now, semi-fit guy is only operating at a 20% thermal efficiency. This means that only 20% of his consumed calories are converted to motion, the rest is expended as heat or remains undigested. Semi-fit must eat 5 times what he burned for propulsion. 273*5 = 1365 kcal

In 19 minutes, he has also burned about 24 kcal for his necessary bodily functions. Thats 1389 kcal that semi-fit needs to eat due to his ride.

1389 Big Mac calories in reality have expended 10 times this for 13890 kcal

Semi-Fit: 13890 Cal – ~$6.80

What does this all mean?

The Audi is more efficient than the bike of course! Save the world and drive one!

Not exactly,

but I can make a few interesting points and disclaimers.

Due to the immensely complex and vast industrial food network, a biker fueled by a Big Mac consumes more energy than an Audi A4 based on the transportation conditions discussed in the previous section. Even though the biker expended a fraction of the calories to move himself (1300 compared to 5000-8000 for the car; also, it should be noted that the vast majority of these calories are expended to move air out of the way), the  energy expenditures to produce and deliver the bike fuel far exceeds that of gasoline.

A bit anecdotal, but we should consider the price for the trip. The biker seems to be spending significantly more, that is until one considers the price of the automobile

Of course, this is only one scenario out of infinity possible combinations. Driving habits, driving environment (city or highway) and automobile upkeep all factor into the car’s efficiency. One could consider a hybrid or electric vehicle because let’s face it, the Audi is not the most fuel efficient vehicle on the road.

The efficiency of the biker is drastically effected by the fuel he/she eats. Eating local, organic, vegetarian and buying in bulk all reduce energy expenditures.

Hopefully, it becomes clear how expensive cheap food really is.

Food for Thought

We all know that the bike is more efficient than the car and I’m not attempting to discourage anyone from commuting via bicycle.

For added shock value, I deliberately excluded some important energy sinks in the previous calculation, especially pertaining to the audi: stop and go traffic, manufacturing and shipping costs of the car**, maintenance of the car, etc.. Not to mention that these large machines are loud, take up more space, are a detriment to the immediate environmental air quality and ironically most drivers are fueled by super-portable fast food (like Big Macs) anyway.

Plus, bikes keep you physically fit (at least semi-fit), yield higher alertness with increased bloodflow, less stress due to heavy automobile traffic and are definitely fun.

My point is, beating a dying horse, to think about the actual impact of the choices you make every day. Digging under the marketeers sickly sweet façade and demanding to know the true cost and value of the stuff you do and buy.

Don’t get me wrong, I still love bikes and admire them for all the benefits that I’ve verbalized in the past, and I also love driving…fast.

If I could pass any advice I would say “Eat a local organic apple and go for a bike ride you lazy bum”

**

I thought it would be interesting to touch upon the issue of the manufacturing costs of cars and why I didn’t include it in my post. Some astute readers may have heard of the a certain report that covers this topic. The marketing research firm CNW released a comprehensive report investigating the actual efficiency of most of the automobiles on the US market called The Dust to Dust Energy Report. The report basically delivers a single figure, $/mile, indicating the energy cost for the lifetime of the car including: manufacture, shipping, operation and disposal. The report made an impact across the country with their claim that “Hummer H3 SUV has a lower life-cycle energy cost than a Toyota Prius hybrid”.

Recently, this non-peer-reviewed report has come under scrutiny, especially (go figure) in the community of scientists supporting progressive sustainable development technologies. There has yet to be a comprehensive scientific investigation into the true cost of the vehicles we drive. However, I can say one certainly appears to be more environmentally conscious driving a Prius rather than a Hummer.

  1. #1 by Godo Stoyke on 12/15/2009 - 3:27 pm

    Hello Robinson,
    Thank you for your effort in comparing bike fuel to car fuel.
    One aspect I often find missing in this comparison is that we are all supposed to exercise anyway. So we really need to compare those people who bike to work to those who drive to work, THEN drive to the workout spa, THEN eat the Mac for their workout, and THEN drive home. And I think it is fairly obvious who comes ahead there (plus, if you buy locally grown organically produced produce, you can actually have a net carbon reduction due to increased soil carbon storage from organic farming practices). Cheers! godo

  2. #2 by Bill on 02/24/2010 - 10:23 pm

    Godo,

    Thanks very much for your input, and yes you’re absolutely right, this comparison is a bit limited in scope, leaving out driving and eating habits in addition to our commute. I also simplified the test scenario to create the results I wanted. My point is this: I really just wanted to make a comedic comparison between the two options to illuminate the energy costs of fast food. Add a bit of shock value that catches people off guard, “Wow, Big Macs use more energy than my car?”.

    By no means were my intents to discourage commuting via bike. I hope this article encourages people to reconsider what they eat and provide some other transportation options.

    I think I said it in the article…’If I could pass any advice I would say “Eat a local organic apple and go for a bike ride you lazy bum”’

  3. #3 by Godo Stoyke on 10/06/2010 - 5:36 pm

    :-)

(will not be published)