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Author Topic: How efficient is the human body compared to a combustion engine?  (Read 17778 times)

Offline John Chapman

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How efficient is the human body compared to a combustion engine? How much work could I do if I drank a gallon of biodiesel compared to my car?
 


 

Offline Chemistry4me

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I would think a lot lot more efficient.
 

Variola

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I would think a lot lot more efficient.

Hmmmm I have no idea about the workings of a combustion engine, or how much energy is wasted. However it does occur that the car does not have an immediate store for energy, that it can use if the tank is empty. We do in the form of glycogen and our bodies plan for the future by glycolysis and the storing of fat in adipose tissue (unfortunately for my bottom!) We also get 4 moles of ATP per mole of glucose used, but we use up 2 to make it, but we are still coming out on top.
Im guessing we beat the biocar.
 

Offline John Chapman

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Well, I'm thinking that on a gallon of fuel my car will take me and four friends (and the weight of the car) about 35 miles. If I drank the fuel, got out of the car and started pushing would I get 35 miles before I started dipping into my own fuel reserves? I suspect not.

Btw, the only reason I suggested biodiesel is because it's non toxic for humans to consume. Other than that it was arbitrary.
 
 

Offline Chemistry4me

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Have a fiddle around with this. I think it's quite good.
 

Variola

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Have a fiddle around with this. I think it's quite good.

27 cartons of Ben& Jerrys or one gallon of fuel... not a difficult choice!!

I wonder what the physiological affects of drinking a gallon of biofule would be..it may not be toxic but I cant imagine it would stay down for very long.
 

Offline John Chapman

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Have a fiddle around with this. I think it's quite good.

That's really good.

It says that 1 gallon of gasoline has the same calories as 150 pints of Guinness (my favourite tipple). So if, instead of drinking a gallon of fuel, I just had the pints could I still push the car? I think there can only be one answer:

Who cares? Lets just stay here and drink the beer!

Seriously though, while your link compare the calorific value of food and fuel it doesn't compare the efficiency of the car and the human, which is what this question is all about.
 
 

Offline Chemistry4me

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you will find that a person riding a bicycle at 15 miles per hour (24 km per hour) burns 0.049 calories per pound per minute. So a 175-pound (77-kg) person burns 515 calories in an hour, or about 34 calories per mile (about 21 calories per km).

A gallon of gasoline (about 4 liters) contains about 31,000 calories. If a person could drink gasoline, then a person could ride about 912 miles on a gallon of gas (about 360 km per liter). Considering that a normal car gets about 30 miles per gallon, that's pretty impressive!


http://auto.howstuffworks.com/question527.htm
 

Offline Chemistry4me

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Howzat? :)
 

Offline John Chapman

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Hi Chem

That's better but it's still not a direct comparison because the person is carrying less weight. I suppose what we really need to know is how many miles to the gallon the cyclist could get if he was towing the car.

If anyone can find a link for that, you can!
 

Variola

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Hi Chem

That's better but it's still not a direct comparison because the person is carrying less weight. I suppose what we really need to know is how many miles to the gallon the cyclist could get if he was towing the car.

If anyone can find a link for that, you can!

I think there are too many variables, some people are better at lowering energy consumption than others, some people weight more or less, more energy is used whie running than while walking ect. Same applies to cars with weight and energy consumption.
The mechanisms for the car to carry its weight is different to that of the cyclist, we rely on muscle weight that is attuned only to carry our weight plus a reasonably defined maximum. Therefore our energy consumption is set at the same rate needed. To tow a car would therefore set the rate much higher, and not what we were built for, so its an unfair comparison. Unless you get the car to tow a lorry. 
 

Offline John Chapman

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I wonder what the physiological affects of drinking a gallon of biofuel would be..it may not be toxic but I cant imagine it would stay down for very long.

I know the answer to this point.

I actually make biodiesel from used cooking oil. When it's finished, if the quality is good it should be crystal clear and look a bit like apple juice. One of the final quality control tests is to put a jamjar of bio in the fridge overnight and if it's still clear in the morning that shows it contains no moisture.

I have a teenage son who is at that age where he is a bit cocky, especially in front of his mates.

Anyway, one day I dared him to drink one of the jars of bio if I drank a different one first. All his mates were there egging him on and he just couldn't refuse without losing face. So I took one from the fridge, drank it down enthusiastically and banged the empty jar on the table with a loud smack of the lips and a satisfied "aaaaah". Having seen how easy it was he picked up his jar and, smirking, began to drink. His expression soon changed first to distaste then to disgust and eventually to horror when he realised he still had three quarters of the jar to go. Encouraged by his mates he bravely battled through about two thirds of the contents before giving up.

"I reckon you need a drink of apple juice to take away the taste" I said, getting out a carton of juice and filling my empty jar. It looked identical to the jars of biodiesel and I noticed him looking at it quizzically. I gave him a "cheers" gesture and drank it down quickly, smacking my lips and banging down the empty jay with a loud "aaaaah", deliberately mimicking the first time round. I could actually see the penny dropping and he stared at me silently for about 20 seconds before running to the bathroom shouting "bastard" as he left the room.

So in reply to your comment "I cant imagine it would stay down for very long" the answer is about four minutes. [xx(]
 

Offline Chemistry4me

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Hi Chem

That's better but it's still not a direct comparison because the person is carrying less weight. I suppose what we really need to know is how many miles to the gallon the cyclist could get if he was towing the car.

If anyone can find a link for that, you can!
Oh, I didn't realise that was what you were asking.
 

Offline Chemistry4me

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I'll try and find something when I've got the time John Chapman.
 

Variola

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So in reply to your comment "I cant imagine it would stay down for very long" the answer is about four minutes. dead

Thats had me in stitches!!!!!! One up for the parents I think!!!  ;D
 

Offline John Chapman

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I'll try and find something when I've got the time John Chapman.


Nobody's addressed me by my full name since my Mum caught me tying up the girl next door. Mind you I was 36 at the time!

Have I been told off? I didn't mean to sound ungrateful or demanding. Both of your external links have been excellent. You do have a knack for finding good external links.  :)
 
 

Offline Chemistry4me

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Haven't you noticed that I address everyone by their full names? :)

And you thought you were special, ohhhh...
 

Offline John Chapman

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So where's this bloody link, then.
 

Offline Chemistry4me

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Nobody's addressed me by my full name since my Mum caught me tying up the girl next door. Mind you I was 36 at the time!
What do you call this then? :)

Errr... that was John Chapman. :)

Oh please John Chapman, don't you start! ;)

But you must have noticed the smell of cooked cabbage or brussel sprouts? There's some sort of chemical reaction going on here such as some volatile compound which is being created as the vegetables are being cooked. Any ideas?
I've noticed this John Chapman! :)

--------
Although I am not sure about it smelling like cat poo!  [xx(]

Thanks Brad John Chapman. ;)
Now I'll just see what other people have to say, if they decide to say it that is. :)
 

Offline Chemistry4me

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So where's this bloody link, then.
Sorry, too busy search for your name on Google. :)
 

Offline Chemistry4me

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Offline John Chapman

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Wow, that really is amazing. So we use more gasoline eating extra food to get the calories to walk somewhere than we would driving there in a car. I have heard this before but it's the first time I've seen the figures. If you add up all the gasoline used by agriculture and industry to produce food then the food has a higher fuel footprint than your car:

Quote from: http://ideas.4brad.com/holy-cow-walking-consumes-more-gasoline-driving

If you eat a lot of beef or other livestock, and want to consider your incremental food as having come from beef, itís around 10 miles per gallon. A Hummer does better!


There's so much significant stuff in that article that I'm going to have to print it off and read it a few times and consider it further.

It seems that it doesn't matter what you do you've got to contend with guilt. I suppose I'd better just get my spade out and grow my own food!
 
 

Offline mattyelle1

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Most efficient scooter: Yamaha Vino Classic, 1.5 L/100km    ( newbielink:http://www.totalmotorcycle.com/MotorcycleFuelEconomyGuide/best-scooter-MPG.htm [nonactive])

Human on Bicycle, 0.32 L/100km ( newbielink:http://en.wikipedia.org/wiki/Energy_efficiency_in_transportation [nonactive])

Mechanism for motion is the same (gears/transmission to wheels). Purpose is the same (move one human on flat surface).

Efficiency ratio: 1.5/0.32 = 4.7

Therefore, the human body is 4.7 times more efficient than a gasoline engine. Obviously many assumptions were made, but should be a fair ballpark figure.
 

Offline cheryl j

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It might depend on whether you consider heat wasted energy. It does serve a purpose in the body, but less so in an engine.

Here's an interesting fact I just read in a book about the brain by David Eagleman: When chess champion Gary Kasparov played against the computer called Deep Blue, Kasparov's brain's energy usage was about 20 watts compared to the computer's thousands of watts. Kasparov played the game at normal body temperature while Deep Blue was burning hot to the touch and required a large collection of fans to dissipate heat.

Of course that was a long time ago, but the brain is nevertheless remarkably energy efficient.

 

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