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Are electric cycles greener than ordinary cycles?

Discussion in 'Earth and Environmental Science' started by Yellow Fang, 21 Jul 2011.

  1. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    I was going to post this to resurrect an old thread in the Politics and Life forum of CycleChat with the intent of winding up Jonesy a little bit. However, just as I was about to post it, Shaun deleted the forum, so I decided to post it here.

    I am reading Electric Bicycles by David Henshaw and Richard Peace (which I think Arch reviewed for Velo Vision). It says an electric bike consumes 1kWh per 100 passenger km, which is a tenth of what a passenger on a half full train or electric scooter would use, a fortieth of a car driver with a passenger, and a fiftieth of a jumbo jet passenger. It says that an electric cycle can produce even less carbon emissions than an ordinary cycling because:

    "When riding a non-electric bicycle you are still, of course, expending energy, but in this case the energy has to come from food (and after using energy cycling, you will eat a quantifiable amount of extra food). Growing, transporting, processing and cooking that food has a surprisingly high energy cost. So, the amount of carbon that can be attributed to a conventional cycle ride depends on your diet. Similarly, with electric-assist cycling much will depend on the source of electricity."

    It then gives a few examples:
    • conventional bike plus imported food = 18.5 g CO
    • electric bike charged by gas power station and imported food = 13.65 g CO
    • conventional bike plus UK grown food = 10.5 g CO
    • electric bike charged by renewable energy and imported food = 9.81 g CO
    • electric bike charged by gas power station and UK grown food = 9.65 g CO
    • electric bike charged by renewable energy and UK grown food = 5.81 g CO
     
  2. amusicsite

    amusicsite dn ʎɐʍ sᴉɥ┴ Staff Member

    Location:
    UK
    I don't know if I agree with your logic.

    If I go and do some exercise, cycling or otherwise, I may eat a little bit more food but not that much.
    How are you calculating the extra food? By calories, extra meal, chocolate/high energy bar?
    How are you calculating the g CO for the food? Would it be 0 if I just ate an apple off a tree in my garden?
    What are the carbon footprints of manufacturing the bikes?
    What are the carbon footprints of recycling the bikes (and battery)?
    What are the maintenance costs and reliability of both. I bet the battery won't last as long as a push bike.

    Appart from the fact you are basing all your figures on very flexible averages, If I cycle on flat ground for 10 mins a day it's vastly different to cycling for 6 hours over the hills. Short easy rides may not even see an increase in food consumption.

    Please show your working in more detail if you are going to get anywhere near convincing me. :p:
     
  3. beanz

    beanz Staff Member Staff Member

    I think the number of variables means it's how the bike is used that decides its ongoing footprint, regardless of whether it's electric or conventional.

    This is just looking at the bikes in isolation though. I'd have thought, if we're pushing the boundaries of this logic, that the benefits of being healthier due to using a conventional bike rather than a more sedentary electric one needed factoring in to the 'cost' of owning each type of bike too. But then - does a healthier person have a more active life and does that mean they have a bigger carbon footprint as a result?

    The main point is surely that bikes are less impactful than other forms of transport, whether they are electric or conventional.
     
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  4. amusicsite

    amusicsite dn ʎɐʍ sᴉɥ┴ Staff Member

    Location:
    UK
    Bikes are most certainly very efficient although walking is still the most efficient.

    I'm not sure on the cost of extra food due to exercise though. It would be interesting if you could dig up some figures on the extra food consumed by active people compared to lazy people. It could almost be the opposite as the fat lazy couch potatoes seem to eat shed loads of food. Where as someone fit may eat a reasonable amount.

    Then you have the type of food you eat. Is it local meat, produce and in season things or do you eat fruit from the other side of the world or heavily processed food with ingredients from all over.

    Mapping humans impact on the environment is an incredibly complex task.
     
    beanz likes this.
  5. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    Is it though? The same number of food calories will get you farther on a bike than by foot.

    Actually, in the book they used an inappropriate symbol for imported food: the banana. Bananas are good because they're transported by boat and don't require heating in greenhouses. Meat is bad, local or not, because (a) they generate methane, and (b) because you only get a tenth of the calories out of them that goes into them in the form of animal feed. OTOH, the food you get out of them is higher quality, being largely 1st protein instead of carbohydrates. Protein is to carbohydrates what electricity is to heat.
     
  6. Shaun

    Shaun Über Geek

    It looks to me like marketing blurb to justify buying an electric bike ... :thumbsup:

    I've never eaten more because of my cycling (I ate more when I wasn't cycling!!!), and in my experience other cyclists don't generally eat proportionally more food than their non-cycling counterparts.

    The cost of the electricity seems to conveniently exclude costs of building and maintaining power stations - delivery of the gas TO the power station - etc. etc.
     
  7. rusky

    rusky Staff Member

    I fail to see how an electric bike can have a smaller CO2 footprint than a conventional bike.

    Even if you exclude the issue of charging it. What about the manufacture if the drivetrain & the costs of transporting it in component & final product form due to the extra weight.
     
    Shaun likes this.
  8. Shaun

    Shaun Über Geek

    Oh oh oh ... and don't forget the cost of disposing of the battery in an environmentally safe way too ... it's not stacking up for me.
     
  9. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    The batteries can be recycled at the end of their useful life.

    It's only the extra manufacture of the battery, motor and associated electronics which is over and above that for a normal cycle.
     
    Shaun likes this.
  10. Shaun

    Shaun Über Geek

    Ah, okay, well that's good to know. :)
     
  11. amusicsite

    amusicsite dn ʎɐʍ sᴉɥ┴ Staff Member

    Location:
    UK
    So I guess the questions are..

    What are the minimun and maximun variations on the amount of calories you would burn for each bike. Taking into account things like a) Going downhill without needing to peddle is probably the same for both, b) how efficient are the motors going up hill, do the offset the extra weight of the motor and battery c) performance on a nice flat area.

    Then all you need to know is the average incline/decline and flat parts of your route, how long it is. Then you can work out how many calories you have saved.

    Once you have that you just have to work out much how extra food someone is likely to consume using up that many extra calories.

    Now you can try and calculate the environmental impact on consuming that quantity of food and see if it is more or less than the environmental impact of making the motor, battery and power for the bike.

    Once you have all that in your stats engine then change the variables of the route, food sources and types of energy and see if the results stay consistant or if they only stand up under certain conditions....

    ...Or you say sod it, I reckon it's greener :p:
     
  12. beanz

    beanz Staff Member Staff Member

    It is. For example... when I first started studying Economics, we had some guest lecturers who did an afternoon on 'cost-benefit analysis'; one of their examples was someone who dies in an accident. We spent a gruesome time considering what were the 'costs' (economic and otherwise) to society of their death compared to the 'benefits' that would accrue - in terms of resources saved, decisions not made, adverse developments avoided - by them having died rather than having carried on living. Really awful stuff to try to quantify, but it certainly brought home how complex the effects of human impact on the environment are, especially as you travel further down the time line.
     
  13. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    The sources the book got its data from are www.travelfootprint.org and a paper about electric two-wheelers in China (link). I saw some other study that said for a domestic household, transport accounted for 9% of carbon emissions, and food and preparation, 15%. Considering how much less energy is consumed by a cycle than a car, then the embedded carbon in the electricity may turn out to be less than the extra 5% of food you may eat.

    According to travelfootprint website, the CO2 emissions of my old daily, 4.9 mile commute to work was 144.5 grams. Walking would have been 189.5 grams CO2. A bus, 647.8 grams. A car, 1565 grams. The first two figures are for average diet. For a diet of locally produced, organic food, the cycle ride would emit 59.4 grams of CO2.

    That site doesn't do electric bicycles unfortunately. According to Cherry, Weinert & Xinmao (2010), the CO2 emissions on an electric two-wheeler in China is about 22 grams per km, which works out as about 172 grams CO2 on my old commute. Mind you, China's electricity is pretty dirty compared to ours, and they tend to use heavier, lead acid batteries.
     
  14. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    Actually it may have been a different paper the authors of Electric Bicycles were referring to. I think possibly titled, "Comparative environmental impacts of electric bikes in China."
     
  15. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    Interestingly, the www.travelfootprint.org site doesn't compare the emissions of electric bicycles, but it does electric motorcycles. It suggests there is very little difference between using a bicycle and an electric moped for CO2 emissions. If you fuel your cycling with locally grown, organic food, the footprint is similar to charging your electric moped with green tariff electricity. I don't know how it comes to its figures, but it's interesting.

    It's got me thinking now. I don't have a car and some places I want to get to are difficult to get to by train or bicycle. In particular, when I want to get to a cross-country race on Sunday morning, I am often dependent on lifts. The problem is that I want something I can lift up the stairs, or cycle when the battery's flat like an electric bicycle, but something that is a bit quicker and has longer range like an electric scooter. It's also odd, that some motor scooters and electric scooters are rather cheaper than electric bicycles. The other hassle is that once an electric bicycle can go over 25kph, it's rated as a moped meaning insurance, helmets and MOT, but not road tax. It's better in America where you can install more powerful electric motors on cycles.

    I've also been looking at some tiny, two-stroke engines that you can install on your bike. The website says they're easy to fit yourself. What it doesn't tell you about are all the legal hoops you have to jump throught to be allowed to drive it on the road.
     
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  16. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    I see the Brompton website has a CO2 emissions calculator. You can travel 1554 km by motor scooter before tail pipe emissions equal the CO2 emissions associated with manufacturing a Brompton. By supermini, you could only drive 586km.

    http://www.brompton.co.uk/cc/index.asp
     
  17. amusicsite

    amusicsite dn ʎɐʍ sᴉɥ┴ Staff Member

    Location:
    UK
  18. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    That's interesting, especially as I live in Reading. I'll have to cycle down there and have a look. That wind turbine rarely seems to generate much electricity, according to display. Actually the last time I went to check on it, the display was switched off, but normally it was only generating about 50 kW. The most I've ever seen it generate is about 650 kW, but that was a very windy day. It's rated at 2 MW. We were once told by some guy from Green Park or Ecotricity that the display was under-reporting, but he didn't say by how much or why.

    I can't see that other micro wind car charging idea taking off. Micro wind just isn't very effective in built up areas, sadly.
     
  19. amusicsite

    amusicsite dn ʎɐʍ sᴉɥ┴ Staff Member

    Location:
    UK
    So how much charge does it take to refill a car or bike and what is the highest charge rate?
     
  20. Yellow Fang

    Yellow Fang Veteran Geek

    Location:
    Reading
    I don't know about cars. 'Electric Bikes' says electric bike battery storage is usually given in Ah (amp hours), but that this value is not helpful in telling you how much work the bike can do. It says you also need to know the voltage. A battery storage of 10Ah is common, and a Li-ion battery often consists of ten cells, each of 3.7 volts, totalling 37 volts. Therefore, total charge is 370 Wh. This is only about 5p worth of electricity, or maybe more like 10p because the charging won't be 100% efficient. Recharge time seems to be about three hours.