Monday, July 7, 2008

Cost of biking in terms of milk

I was recently challenged to figure out the "mileage" a friend of mine gets on his bicycle as a function of gallons of milk ingested. More succinctly, how many miles does he get per gallon of milk when riding his bike. Of course this depends on the type of fuel (Whole milk, 2%, or skim), the speed at which you are riding, body weight, percent body fat, basal metabolic rate, etc. For the purpose of these calculations we will assume a normal adult male of about 160 lbs. Of course we are also assuming that you ingest nothing but milk...

To wit - you can expect the following mileage:

Pretty efficient really - or is it? Just how much energy does it take to get a gallon of milk from the cow to you? How much energy does it take to grow the cow?

For now, let's assume that the cost of milk is roughly equal to the cost of regular gasoline and look at a direct cost analysis/mileage. Both my Prius and my scooter beat the milk as fuel alternative for my bike. (I drink only skim milk). Whole milk is the best fuel - and riding slow gives me a bigger bang for my buck - but the three hour commute each way would make getting my job done a difficult trick. For now I will stick with my motorized vehicles for commuting and my bike for shorter trips, and for fun.


::athada:: said...

I've heard the same when comparing milk-powered walking vs. driving (with driving the victor).

Studies like these are great - they show that our easy "green" fixes aren't as black-and-white as we'd like them to be. But one blog post (by nature) still isn't enough to make an informed decision. What about a vegetarian diet with one glass of milk per day? What about the energy that went into creating the bike vs. the car, as well as repairs and maintenence? What about local, grass-fed milk vs. trucked-in grain fed milk? How do you value the extra time used to bike vs. taking the car? What is the value of your exercise?

The moral of the story (according to this study at WorldChanging is that cutting out or cutting back beef and dairy products will give you the most GHG-reduction bang for your eating buck.

Education, discovery, and open-mindedness is the answer, I hope, not despair or oversimplification.

Burton Webb said...

Too true Adam! I hope I hinted at that. It's a question of source, scale, distance, and value. And, those pesky cows make a lot of methane.

This was just a question of miles per gallon of milk. I think its genesis was in the fact that they cost about the same thing.

Burton Webb said...

Oh - one more thing. Cows and almost all biological entities recycle recent carbon, thereby not contributing directly to the GHG. It is in the input of old carbon (Ancient carbon, fuel, that has been trapped for millennia) that we add to the current GHG. The relative amounts of ancient carbon invested in getting the milk to market is significant - and should be considered.

You extract the same number of calories from a vegan diet as you do from a glass of milk. Calorie extraction from food is directly proportional to the number of CO2 molecules we make when metabolizing. Remember the Kreb's cycle?

Keith Drury said...

OK thanks for that calculation....

For the speed I usually bike I get 47 MPG of milk...(which costs about the same per gallon as gas)... so fairly good mileage per dollar but maybe not so great per carbon footprint?

If Adam is suggesting that a gal of milk contributes as much to my carbon footprint as a gallon of gas...then maybe I should power my bike by eating radishes and tomatoes from my garden.

::athada:: said...

Burt -

But aren't cows converting each molecule of CO2 (or -C- in plant tissue) into methane (CH4), which is 23 times more potent as a GHG?

Also, ancient carbon is tied up in the production of the cattle inputs. Roughly 10 pounds of grain per pound of beef, vs. 1:1 vegan. This grain has ancient carbon attached to it in ways that are a bit less conspicuous than a reefer truck (tractor fuel, processing, fertilizer, irrigation, as well as land use change from field/forest to farm).

Thanks for opening this up!