Monday, February 21, 2011

Are Bicycles Good For the Environment?

An Inspired Cradle to Grave Analysis specific to the US.

I want to emphasize that I bicycle because it is fun, pure and simple.  I still get that same burst of excited energy and amazement that I remember feeling at the age of 8, whooshing down the street, feeling the wind, surprised by the sense of freedom, a rush of sights and sounds and feelings, and just plain happy action.

On top of that I get the challenge and entertainment of a complex but graspable tool, a tool that inspires me to tinker and ask questions.

So, are Bicycles actually good for the environment?  Unfortunately, my calculation reaches a very provisional Yes and No.

Mind you, with most of these types of comparison essays, the author has an agenda: a war on cars, a war on bicyclers, a war on wasted energy, a war on meat eating, a war on disambigous agendas, and etcetera.  I hope to avoid having an underlying agenda, and get at a practical observation that inspires the reader to pause and perhaps step out of any agenda.

Compared to What?
A good simplification:
Compare a bicycle to a car and presume the bicycle is used to supplant the car for transportation:
        The two gizmos use very similar resources: iron, aluminum, rubber, plastics, and etcetera.  These resources are used in similar ways and proportions and require similar mining, and manufacturing processes.  These resources have the same recycle potential.  It seems reasonable to make a pound for pound per functional benefit comparison between the two uses of the same resources: car miles per pound compared with bicycle miles per pound.
        Here is a basic comparison: my current car weighs about 100 times as much as a bike that I have ridden 10,000 miles.  My wife and I average 2 people per trip with that car and most of my use of that bike is for errands, work, and activities that replace the option of using a car.  So, to get an equivalent number of passenger miles per pound of resource, we would need to drive the car 50 times farther than the bike miles, which would be a half million miles.
        This initial comparison makes the bicycle use of resources seem good when compared to using those same resources to make a car, but I must admit that further analysis is called for.
A slightly more refined simplification:
        A good environmental investigation should try to fathom cradle-to-grave costs.  One should investigate impacts of associated resources.  So, I have added weights for gasoline, tires, etc.  (I did not include food weight on the bike, because the extra calories I burn by riding simply counteracts the effects of the excess food I eat anyway, and so the energy on the bike is a net improvement of my already wasteful and waist-full eating habits.  In other words: if I do not ride the bicycle I still eat the same amount of food, I just get even more over weight.)  This accounting process led to the expanded list below, which compares two bikes I have owned with two cars I have owned.
        After looking at the list, one might conclude that if car 2 were to be driven only 20 times farther than bicycle 2 has been ridden, it would equal the bike in providing comparable passenger miles per pound of resource consumed, but actually when you include the weight of gasoline, one can never equal the bike, and in fact if car 2 is driven even farther, the passenger miles per pound of resource will get smaller.  It is surprising how the weight of gasoline completely overrides the original weight of the vehicle, even in the case of the bus cited in the notes.  Increasing the number of passengers in the car is about the only way to make a significant improvement in the car’s use of resources.

Further Investigation:     
        So far it seems my calculations are indicating that just a small increase in bicycle use could be helpful for the environment, but subtle realities about our real world driving habits make this improvement more difficult to achieve than expected. 
        For a really surprising extended thought and calculation, go one step further and assume that on car 1 I added a bike roof rack that stays there all the time and subsequently reduces the gas mileage on car 1. If I use the bike as I have used bike 2 and also have a roof mounted bike rack, the bicycle has actually worsened my overall environmental impact.  It would have been better to have not had the bike and to have just driven the car without the roof rack.
        How many cars do you see running around with empty bike racks on the roof?  I know that less than 1% of car drivers, or people in general nation wide, use a bike for regular commuting and shopping and other car supplanting activities.  By shear weight of numbers I suspect that bike racks on car roofs are more than outweighing any environmental benefit from bicycles, and therefore if bicycles encourage a small percentage of drivers to put roof racks on their cars, bicycles are a net waste of resource use.   If all bicycles are lumped together, then the serious bike commuters would need to go 750 miles a year just to balance out all the environmental waste of sum total bike users and their roof racks.
        One might also examine the miles driven with bikes on the roof of a car in order to do non-utilitarian sport bicycling.  But in that case, it is very likely that those same people would be driving somewhere to play anyway, so the net loss due to the bike is only the extra loss in fuel efficiency and that amount can probably just melt in to my previous assumptions and averages.

Roads and Infrastructure:
        The cradle-to-grave concept should at least touch on the cost of roads and infrastructure.  As much as I read rants about bicycles getting in the way of traffic and that bicycles need to pay for the cost of bike lanes (some paint and signs) and so on, all the research I can find for highway expenses in cities and towns (not to mention interstate federal highway costs where bicycles are not allowed) the percentage of infrastructure money used and worn out by bicycles is considerably less than 1 percent, so at least compared to a car, the infrastructure bicycle cost is very small.  It is both figuratively and literally a boundary line expense.  Since bicycles are not really wearing out these structures, the structural investment is long lasting, but defies an easy cost/benefit environmental accounting.  Bicycle specific structures are rare, but in any event, a pound for pound comparison with car infrastructure costs would be reasonable, and since the process and materials are similar, a dollar per dollar comparison would be reasonable too.  In that event, the passenger miles per dollar of budget is about the same for cars and bicycles, perhaps slightly favoring the car as the total yearly miles for bicycles is in the range of two-thousandths of the miles for cars while the transportation budget for bicycles is in the range of six-thousandths of the budget for cars.
        What about other environmental costs: land use, air pollution, water pollution, what else?  I posit that the net affect of the bicycle on these things is neither good nor bad, and basically has no effect.  The reality is that people are the movers and choosers, and bicycles are not changing the way people in the United States move and choose, except in very rare and isolated particulars.  Bicycle owners are the same people who are car drivers, landowners, commuters, consumers, even vegetarians and yogameisters (that is not a word).  And bicycles are not really changing any of that, up or down, sideways or aroundways.
        In summary, a bicycle in the particular case can be a very efficient and environmentally responsible transport, if one uses it in optimal ways. But the bicycle in the general case as used in the United States may not be so good in terms of efficiency of resource use.  This is especially the case when one acknowledges that most bicycles just sit in storage and thus represent a total waste of resource use, and that many owners drive with an unnecessary bike rack on the roof of their car wasting extra fuel.  I have tried to find data to fill in for this “average” bike, but the sources I find readily admit that estimates of miles ridden per year on all bikes is unreliable, so the “average bike” in the graph above has a range of error that puts it exactly in the same realm as the average car.

Calculations and data:(prices are inflation adjusted to 2011 and are included only for curiosity sake.  I am using 7 pounds as simplified round weight for 1 gallon of gasoline.)
(The graph above uses several wildly deceptive strategies such as a logarithmic scale which nobody knows what the heck that means and is included purely for artistic conceit and because the same “nobody: will probably not want to look at a bunch of unsupported data anyway.)

Bike 1: 1972 Gitane lightweight bike: 22 pounds, $1300
                                Price per pound  $59
                                Ridden 40,000 miles (then given away still usable)
                                Assume 18 pounds of tires and tubes and brake pads etc.
                                Passenger miles per pound of resource: 1000
                                Adjusted for permanent bike rack on car:
                                            Extra pounds of fuel used by car 1: 2186
                                            Adjusted passenger miles per pound of resource: 18

Bike 2: 1997 Mongoose 18 speed Mountain Bike: 30 pounds, $500
                                Price per pound $16.7
                                Ridden 10,000 miles (then stolen)
                                Assume 30 pounds of tires and tubes and brake pads etc.
                                Passenger miles per pound of resource: 167
                                Adjusted for permanent bike rack on car:
                                            Extra pounds of fuel used by car 1: 2186
                                            Adjusted passenger miles per pound of resource: 4.45

Car 1: 1978 Chevette, 2300 pounds, $13000
                                Price per pound $5.7
                                Driven 280,000 miles (then given away still running)
                                Estimated average passenger load: 1.3 (plus dog)
                                Mpg 30 => 65400 pounds of gasoline
                                Tires, batteries, etc: 500 pounds
                                Passenger miles per pound of resource:  5.6

Car 2: 1993 Toyota PU, 2740 pounds, $20,000
                                Price per pound $7.3
                                Driven 180,000 (and still going)
                                Estimated average passenger load: 2
                                Mpg 28 => 45000 pounds of gasoline used so far
                                Tires, Batteries, etc: 250
                                Passenger miles per pound of resource: 8

Roof rack exception:
        US drivers: 190 million
        Average yearly driving miles: 14,500
        Average mpg: 20
        Assume 0.5% of all drivers add a roof rack and reduce gas mileage ½ mpg
        Pounds of extra fuel consumed per year: 123,500,000
        Number of people who regularly use a bike as alternative to car use: 750,000 (high estimate)
        Miles in one year average bike rider must forego cars in favor of the bike to compensate: 706

Bus: Average School Bus, 14000 pounds
Driven 300000 miles answers.comSchool Bus
                                Estimated average passenger load: 25 - 9
                                Mpg 6 => 350,000 pounds of fuel
                                Tires, Batteries, etc: 2000
                                Passenger miles per pound of resource: 20.5 –7.4

Prius:                      2930 pounds, $24000
Price per pound $8.2
                                Driven 300,000 miles
                                Estimated average passenger load: 1.57 (wikipedia)
                                Mpg 46 => 45650 pounds of gasoline
                                Tires, batteries, etc: 300 pounds (battery estimate here is a big controversy)
                                Passenger miles per pound of resource:  9.6

Infrastructure cost, one example:
Oregon total highway budget 2009: 5.2 Billion
Special uses: Special Programs — $185 million: funds programs for salmon, watersheds, scenic byways, pedestrians and bicycles, winter recreation parking and more.  If allocated proportionally that would be 30 million for bicycles, or 6/10 of one percent of
the budget.

Average Bike: 30 pounds.  Assume bicycle has a 20 year life span, and 200 million bikes are in US and (from Bicycle Universe Info) 6.2 Billion miles are ridden per year in the US.
                                Ridden 600 miles
                                Assume 5 pounds of tires and tubes and brake pads etc.
                                Pounds of fuel added due to average car for roof rack use: 12
                                Passenger miles per pound of resource: 12.8

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