Horses vs. Cars
After reading about switchgrass I realized that there was another form of transportation that also runs on grass: horses. Which made me wonder how horses would compare with cars in "fuel efficiency".
Caveat: Everything I know about horses is courtesy of a 5 minute Google search that gave me this site and this pdf. So these numbers could be way off.
A standard horse weighs about 1,000 lbs and eats 2% of its body weight in dry feed a day or 20 lbs. The Pony Express horses worked 25 miles a day. Assuming that a horse can average 25 miles a day every day, that works out to a horse going 1.25 mile/pound of feed.
To give the cars their best chance I will go with the Prius and its 50 mpg fuel economy. From the switch grass post we know that 1 ton of switch grass can create 33 gallons of gasoline or 1 gallon is created from 2,000 lbs / 33 = 60 lbs of switchgrass. 50 mpg / 60lbs per pound = A Prius goes .83 miles/pound of switchgrass.
So the horse comes in 50% more efficient than the Prius. I am really surprised that the car is even that close. Of course you have to feed the horse for the entire day and only a small portion of that energy goes to transporting humans vs. the car that only uses energy when running, so that works out to the car's benefit. If you were to have 2 people in the Prius vs. 2 people on two horses, the Prius would actually take the lead. And there are other issues in this comparison as a horse can only go 25 miles a day, and only at 9mph which wouldn't really cut it for modern transportation.
Now lets look at this it terms of how much land would be required to support the energy, the transportation "footprint". For the horse 20 lbs * 365 = 3.65 tons a year. At 5 dry tons per acre yield of switchgrass (see previous post) that works out to .73 acres/year footprint for a horse.
For the Prius, lets assume you drive 12,000 miles a year at 50mpg = 240 gallons. At 165 gallons per acre, this comes to 1.45 acres/year footprint for a Prius. So the footprint for a Prius is just about double that of a horse.
Interestingly, I was watching a Modern Marvels (still the best show on television) a while back and they stated that tractors allowed farmers to get rid of approximately 23 million draft animals. To feed them took 80 million acres of pasture and 80 million acres of crop land. I am not quite sure the date on this but I believe it would have to be early 1900s. 160/23 = 7 acres per animal, which is 10 times what I estimated for my horse. I am not sure how to reconcile the order of magnitude difference. This Modern Marvels also said that fertilizer allowed crop yields to triple, so maybe that is part of it. It is also interesting that we used to set aside 160 million acres for draft animals, and now some are proposing using 140 million acres for switchgrass to create biofuel for our vehicles. The more things change the more they stay the same.
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11 comments:
Very interesting, indeed! I believe vegetarians use a similar rational for reducing meat consumption: lesser footprint.
Ref: 101 reasons to be Vegetarian
Thanks for this article. The parts in bold match my own (10 minutes with google) research.
I am also wondering about the cost of maintaining the road. I guess an electric car requires an asphalt road, whereas a horse can run on asphalt/dirt/grass.
Anon,
Good point on the road, as concrete and asphalt take a bit of energy to produce (and emit large amounts of CO2). I don't know how large though.
my friend sent me a link to your blog, and I responded via email. Thought I would share that email here:
ok, the blog does not address that a car is the equivalent of the power of many horses and even though he addresses the issues of multiple riders, he does not really take it into account in his equation. but let's face it, the car does both go faster and has a greater carrying capacity without increasing (too much) the amount of fuel it is using or decreasing (too much) it's fuel efficiency. (even though you do loose efficiency as load increases in a car, compare that loss with the loss a horse would experience if you put four full-grown adults on its back....). Consider this: a 2009 Honda Accord has 268-HORSE POWER and gets 29miles/gallon. The blog does not take horse power into consideration, and I speculate that taken into account that you are getting the power of 268 horses with each mile, the fact that it uses more switchgrass per mile than just one horse is almost negligible. Also, the horse goes 25 miles/day and if you put more miles than that on it, it would degrade rapidly in terms of health and longevity. A car is limited more by the ability of the driver in terms of how many miles it can go in a day, and as that daily mileage increases, it does not decrease in output ability or efficiency (as a horse would). Now, these factors combined (difference in power, difference in carrying capacity, difference in daily mileage) I think dramatically alter the equation.
He also mentions the inefficiency of the horse as it requires fuel to function 24 hours/day even though only a small percentage of that functioning results in productive output (i.e. transportation). This is the same problem with cattle. You put fuel into animals in order to receive a certain output (transportation or food) but they use the fuel in a million other ways that are not related at all to your desired output because they are living organizims and operate as an incredibly loose system (i.e. you put fuel into them, they then use and release that energy in the form of heat, daily movements, and the occasional productive use when you do use them for transportation). The car, however, is a closed system in which you put the fuel in, and that fuel is used directly for transportation and nothing else. It doesn't go running around in the driveway or galloping up and down the city streets when you aren't using it, and it doesnt need to heat itself up (thermoregulate) when the temperatures drop. Oh! Not to mention that you are also spending more calories YOURSELF when you feed a horse compared to when you put gas in a car and you have to do it much more frequently, thus further increasing the amount of energy required to fuel the animals.
Of course, horses look way cooler and definitely get a million more points for style, but in terms of their "green" points, I'm hardly convinced. I don't want to rain on anybody's parade, but if you really want to be green and efficient and use fuel wisely, I don't think horses are the way to go. Not to say that cars are either, but this man's comparison is highly incomplete.
NOW BIKING IS A DIFFERENT STORY!
Anon,
Good points.
On the horse power, you are right that a standard car can haul 4+ people and lots of goods from the store, which would require extra horses to do the same. On the other hand, probably 90% of the time all that extra horse power is put to waste as a car is just used to transport 1 person from location A to B.
I agree with you that a horse can only go so far each day while a car can go much further.
The other thing to point out if we wanted to return to using horses for transportation is how much manure they create. New York City was a mess with all the horse crap on the streets. Cars don't have that issue.
The point of this post wasn't to make the case to returning to riding horses as much as it was just trying to compare how much land was needed to run car on biofuel compared with how much land was needed to feed a horse.
And I am with you on the biking. From an environmental perspective, that is the best form of transportation.
From an environmental perspective, the bike loses as it requires a factory to produce it. Where do you think aluminum and rubber comes from? The cost of maintaining the factory requires way more land and energy than it takes to feed a horse. Horses can be used with 100 percent natural materials which is not the case for the bike or the car. Horses were here thousands of years before the car and the bicycle, and they will be here thousands of years after the last car and bicycle bites the dust.
I have been considering the change back to hores myself. it is not really a viable option in my present state, as i live in a rather large city and have a large faimly, but in the case of someone living in a country town, where they are on their own and travel less then 5 miles each day to work, it is a very good option.
Also there are other benifits from owning a horse, firstly they would help as an effective lawn mower, where the cut lawn would have been wasted any how. Secondly they would provide healthy manure, this could be put on the garden or even sold on, i personally get my manure fresh from my friends farm.
Finally if we think about what it takes to care for the faimly pets(dogs, cats and birds) a horse is just an extension of this.
Hi,
Some important factors which may have been forgotten
- considering the amount of energy required to make a car vs horse(old enough to ride after 2yrs).
- avg. kms of car per day per person per lifetime of the car
- production footprint of prius cars is greater than some 70s model fuel guzzler (so you could drive 70s model v8 from 1970 till now n still produce less pollution then it requires to make a prius- i haven´t seen any figure on that but have been told a number of times)
hey, Very interesting blog. I realize its from 5 years ago but still very relevant.
I actually went to New Zealand where Grass Based dairy farming is a huge sector of their economy. Pasture is the essential food source for their cows. From what I learned their the stocking rates which would be how many cows per acre or hectare would be anywhere from 2-4 cows per hectare(or roughly 1-2 per acre). Farmers their will look at their pasture and say "Looks like that paddock has 2800kg(per hectare)". The know grass in and out. Grass growth rates vary seasonally from 5kgs/day/ha in the winter to 70 or 80kg/day/ha in peak in NZ.
Its very important to understand that to achieve those stocking rates and growth rates requires division of pastures and periods of rest for grass regrowth.
Generally the farms I visited handled hundreds of cow so they were sitting on hundreds of hectares of land. But the principles that determine grass growth are still the same and can be scaled down.
Its also important to note seasonal variation on how grass growth speeds and slows and how there can be lots of waste if not managed well. 7 acres per animal does seem very high but after seeing how the stocking rates were achieved in NZ and seeing how we abuse our pastures here in Northern Indiana(even many Amish with their horses) i don't find it surprising. Also winters here make farmers under utilize the potential of their grass pastures because they get used to feeding grains and other feeds during the winter and tend to house animals inside.
Horses provide an opportunity to have a much higher Return on Investment than to cars as they can reproduce. The best you can get when cars bang each other is a fender bender and having to spend some cash on repairs...
The 20 lbs per day is pretty much for a grazing horse. A horse running 25 miles would probably need at least twice that much. A horse just keeping warm in the winter can need 30-40lbs.
I bike is way more ecological. My wife hauls her horse around with a trailer and a pickup with a 5+ liter engine and she insists that if only the Chinese went to horses instead of bikes they would be way better off. This is crazy talk. The hoses would give off green house gases and require way more maintenance and acreage then a bike.
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