Originally published in GreenSWord Feb'06

The Numbers Game - How big is a Tonne of CO2

CO2 is a gas at room temperature and atmospheric pressure. The numbers get a bit confusing when talking about the proportion of CO2 in the air (volume in cubic metres – cu m) and the weight (in grammes, kg, or tonnes) of CO2 that burning a gallon or litre (volume again) of fossil fuel generates, and how much a ‘personal carbon allowance’ (back to weights) might be per year.

A kilogram of CO2 occupies about half a cubic meter (actually 509.1 litres) at normal atmospheric pressure and temp. That is about the volume of a double kitchen unit filled with pure CO2 gas.

The current level of CO2 in the atmosphere is around 380 parts per million by volume – in a million cubic metres of air there are about 380 cubic meters of CO2. The rest is mostly nitrogen (78.9%), and oxygen (20.9%).

So 1kg of CO2 would be distributed through about 1316 cubic metres of air – that is about the volume of a three story block of 12 one-bedroom flats.
If half a cubic metre is about the size of a kitchen unit, a cubic metre is about the size of a single wardrobe, and two cubic metres a large double wardrobe (but not in Narnia !)

A medium sized supermarket floor is about 20,000 sq ft and the ceiling is usually at least 10 ft high – so the volume of a supermarket is about 200,000 cubic feet, which is about 5,600 cubic meters. The CO2 gas from all the air in a typical supermarket could be fitted into a double wardrobe and would weigh about 4kg.

As a gas, all the CO2 in a typical three-bed semi would occupy about the volume of a 21” TV (tube, not an LCD).
If we go back to the Ford Focus 1.6 that last time we showed was equivalent in energy terms to a sedan chair carried by two slaves, we find that it generates 160 grammes of CO2 per kilometre. In other words every 4 miles (3.9 actually) it is spewing out another kilogram of CO2 (a kitchen unit full).
Scientist agree that anything over 450 ppmv of CO2 equivalent would be highly dangerous to the planet (and many put the desirable figure much lower).

Here we introduce another confusion – there are other gases contributing to the greenhouse effect, and for simplicity their effect is calculated in terms of the volume of CO2 that would produce the same effect. So when you see the term CO2 equivalent (or ppme) it is including all the other greenhouse gasses.

The latest consensus seems to be that we can only afford another 20ppmv of pure CO2 – so at best we can only add another 112 litres (about a tv set full) of CO2 to the air in that supermarket – 220 grammes in weight

So if you drive your car just 1 mile to the supermarket you have effectively tipped the air inside the supermarket over the danger point – and so has every one of the other 1000 people who drive to that supermarket each day. Imagine 1000 supermarkets stacked up in a pile.
Most people probably drive more than 1 mile to the shop and back, so treble that pile – it is now 30,000 feet high and a bit of a hazard to airplanes. Now imagine another 30,000 foot high supermarket alongside the first one – and another one every day…that is the rate at which just driving to the shop is destroying the planet.

If your personal carbon allowance (for example under a tradeable quota scheme) was set at 2 tonnes of CO2 equivalent per year then that is about 1000 cubic metres of pure CO2 gas, and you will use your entire annual allowance driving your Ford Focus 7,800 miles – leaving nothing for heating, lighting, or the carbon content of any goods or foodstuffs you buy.

A further area of confusion is that the carbon content in the air can be given either in terms of CO2 (as above) or as just the carbon weight ignoring the O2 bit – this will give a lower mass (12/44ths or a bit less than a third). The advantage of this method is that burning a tonne of coal (which is more or less pure carbon) will produce a tonne of atmospheric carbon. Normally this is expressed in units called TC (tonnes of carbon) or MTC (million tonnes of carbon) – some unscrupulous polluters may quote the lower pure carbon figure without being clear about the units to make their activity sound less harmful.

I hope this helps give a bit of a feel for the numbers, and how close we are to catastrophic change. Business as usual is really no longer viable and individual actions to change behaviour can help.

Next time numbers in transport.

Originally published in GreenSWord Oct'05 

New Nuclear Generation – back on the Agenda?    

This is an issue that is not going to go away  – Blair seems set on fast-tracking a new generation of nuclear power stations to replace the ageing ones which are closing in the next few years (about 16% of our electricity supply) and then to take over from the gas turbine stations as the gas supply peaks around 2020 (a further 30% of UK electricity)

As Richard Lawson wrote to The Independent back in June:

Sir: The chairman of the Nuclear Industry Association wants the G8 to stop "denying the part that new nuclear generation can play in helping to mitigate the effects of climate change".  
If it does, it is a bit part.
New nuclear generation could supply our civilisation with approximately three years' worth of electricity, at a CO2 cost roughly equivalent to that of gas.  After those three short years, the planet's uranium reserves would be sorely depleted, as also would be the public finances.
Not to mention our slender chance of preventing the spread of nuclear weapon to yet more unstable and/or deluded world leaders.
Richard Lawson www.greenhealth.org.uk Green Party, Congresbury, North Somerset

The reference for that astounding figure that nuclear could only supply the world’s electricity needs for three years before the uranium runs out comes from a report by Jan Willem Storm van Leeuwen and Philip Smith titled ‘Nuclear Power: The Energy Balance’ first published in 2002. The nuclear industry criticized the report, and van Leeuwen & Smith published a detailed rebuttal of the criticisms in 2003. The report has been further updated in August 2005 and can be found at www.oprit.rug.nl/deenen/  

Nuclear fuel is a finite (non-renewable) resource just like fossil fuels, and its extraction and preparation for use depends on fossil fuels and generates significant CO2.

The report shows that if all the world's current electricity consumption was supplied from nuclear, then the available rich Uranium ores would be used up within three years, and thereafter it would require more energy to extract usable uranium (U235) than would be generated by burning it (as the authors put it effectively turning Nuclear plants into incredibly inefficient fossil fuel burning plants with radioactive by-products!).

So even if only 20% of the world's current energy needs was supplied by nuclear, their fuel would run out before the end of their design life.
And this is without considering the waste problem (notwithstanding Bob Hawke, ex Austrialian PM’s recent kind offer to use Australia as the world’s nuclear dump)

Nuclear is quite simply not a viable long term power source on a planetary scale - end of debate. Its problems, however, are irredeemably long-term, and eventual costs and consequences unknown. 

Unfortunately this is unlikely to be the end of the debate as the Government seems hell bent on ignoring the potential of large scale micro-generation and taking the nuclear road.

There could be some tough decisions and campaigns ahead for the Green movement.