But it occurred to me – there’s an assumption frequently made that riding a bike is for free.  And it’s not.  You have to power the bike, it’s human power but that’s not free – we need food to do work.

The rates at which we burn calories and therefore food are pretty well established for various activities – resting, walking, running for example – as are the carbon impacts of food and therefore of the calories we use.

Typical daily calorie requirements are also well established.   And if you up your activity level you up your need to eat – it’s that simple.

Easy enough then to take a closer look at just how many more calories it takes to ride a bike, and what additional carbon impact comes from that – compared to the calorie intake required to drive a wind powered car instead.

It might not be surprising to find that driving a wind powered car is actually better in terms of CO₂ impact than riding a bike – after all wind power is zero carbon (the embedded energy in a windmill is repaid in about six months of operation – after that it’s all carbon free) – the assumption though has been that biking is zero carbon too, but it ain’t.

Biking requires 40 additional calories per mile – or 400 additional calories for a ten mile trip.

Using some typical food carbon footprints and assuming ten miles a day for a year you get a total annual impact of 333kg CO₂ – from riding the bike.

This is over and above the normal food impact – which, based on a mixed diet of 2,400 calories a day (for example) would be responsible for 2 tonnes of CO₂ a year – veggies and vegans will do better than that of course.

Driving a wind powered car on the other hand requires 100 calories an hour (to power the driver), which is roughly 4 calories per mile (assuming average 30 mph) this produces 76g of CO₂ for a ten mile stint and a total of 28kg of CO₂ for that 10 miles a day for a year.

The difference is 0.3 tonnes CO₂ per year.  The wind car is one third of a tonne of CO₂ better than the bike…!

Like I say not surprising that wind cars win if you accept that wind power is zero carbon and biking requires more food than not biking.

But the big surprise in all of this, and perhaps the bit that makes it worth sharing – is that an electric car powered by the grid as it is, actually emits only ever so slightly more carbon a year than biking the equivalent distance.

A grid powered electric car travelling 5000 miles per MWh of electricity will produce 94g CO₂ per mile (including the drivers contribution), that’s 342kg per year of CO₂ for the 10 mile a day trip.   Only 9kg of CO₂ per year more than cycling.  And what’s 9kg out of one third of a tonne?

This is counter intuitive I think.

Biking isn’t so obviously squeaky green as it’s assumed to be – it has a carbon footprint virtually equal to grid powered electric cars – that’s a shock to me.  The reason for that is probably that the human body is not the most efficient user of fuel, whereas electric motors hit the high 90 percents.  And even the grid manages around 50% fuel efficiency.

No embedded carbon in the car or bike (or food chain) has been taken into account here of course – just straight use of each.

It might be interesting to look at embedded levels of CO₂ in cars and bikes and calculate how many years it would take for a wind powered car to……

Any volunteers?

Cheers.

PS – A petrol car doing the same 10 miles a day would emit over 1.2Tonnes of CO₂ in a year – about four times that of the grid EV or Bike – and 45 times that of the Wind EV.

Simon – you make a couple of good points there. The idea of sitting around for 20 minutes while your car charges will be a bit of a challenge for some people, and it could require large numbers of ‘pumps’ or parking spaces. On the other hand we’ll all have ‘petrol stations’ at home, since we can plug our cars in every night and so the number of us using on street ‘petrol stations’ will drop perhaps massively. It would really only be when travelling more than 150 to 200 miles at a time – I don’t know what proportion of car journeys that is, but it would make interesting reading. And when so many of us have electric cars it’s easy enough to imagine fast charging facilities springing up in Supermarket car parks – I mean for how long will Tesco be willing to sit this one out? Even public car parks could have fast charging bays, and slow ones – for short and long stay parking. It’s quite possible that habits will change significantly and trips to the ‘garage’ disappear altogether.

Loads on the local grid are another good point, there’s definitely an issue to look at there. Electric cars shift the current petroleum load (in terms of energy) onto the grid anyway – and that’s a really big shift. Easier to strengthen that infrastructure though than build a new (hydrogen) one.

I don’t personally believe that swappable batteries are something that will work. It would require an incredible degree of co operation between car makers, and similarity of car design. Right now it would be nice if there was a common small appliance charging standard, for mobile phones and cameras etc – but instead we have a vast array of different ones. Bringing all car makers together would be far harder.

And then there’s the question of weight, these batteries aren’t light, it’s not likely to be easy to swap such a thing yourself.

Swappable batteries would be very unlikely to work in retrofit electric cars. And retrofit offers huge potential to reuse what we already have.

And finally one of the big advantages of the latest battery technology is you can shape the battery and distribute and fit it into parts of the car where it can assist to optimise weight distribution and centre of gravity – swappable batteries would negate all of that.

I doubt very much that the idea will succeed. It sounds good in principle though.
Cheers.

Transport is one of the really big issues we have to face up to – how are we all going to get around, post oil and post carbon?

I think the answer is electric cars, cars charged using wind energy – in fact I prefer to think of them as wind powered cars.

We’re building one right now – a car to smash the stereotype of looking like something Noddy would drive. An out and out sports car. Capable of 0 to 60 faster than a V12 Ferrari, able to top 100 mph for sure – and do 150 miles on one ‘tank’. All with zero emissions. Cake and eat it. Petrol head meets zerocarbonista.

We’re making this car with technology available in the world today. Throwing down the gauntlet to the big car companies. If we can do it – why (the hell) can’t you?

Work is underway, I expect this car on the road for the summer.

We’re keeping a film record as we go, hoping we might make this into a film for TV, if not definitely for our web site.

Watch this space! And Clarkson beware, or maybe not. I’ve a feeling he might like it…

e2a: check out the little clip of the video intro