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The Carbon Cycle
As stated on page 1, there is an added problem with using fossil fuels as sources of energy - they generate carbon dioxide, CO2 , and this gas leads to global warming. Most people will be well aware of the carbon cycle and that plants require CO2 for photosynthesis. This is taken from the atmosphere and oxygen is given out. For animals it is the reverse; oxygen is inhaled and CO2 is exhaled. Probably less well known is the fact that there is a CO2 cycle between the oceans and the atmosphere and both cycles are shown in the following diagram:-
The numbers in the diagram are in Giga tonnes of carbon and the numbers in the white boxes represent reservoirs of carbon with the ones next to arrows showing the yearly flow of carbon.
Each year, deforestation amounts to approximately 2 Gt of carbon and global use of fossil fuel contributes about 7Gt of carbon. These two figures may appear quite small compared to the two main cycles which convey about 100 Gt, annually between the atmosphere and either the land or the oceans. (It must also be noticed that the oceans are presently absorbing 3 Gt which is not being cycled.)
Despite the seemingly small values of 2 Gt and 7 Gt as man-made contributions to the CO2 cycle, very measurable effects are occuring on earth. Firstly, there is increasing amounts of CO2 in the atmosphere which causes global warming and, secondly, there is increasing acidification in the oceans which will have potentially damaging consequences for marine life. The latter has been highlighted in a recent Royal Society report http://royalsociety.org . For convenience the report is placed on https://sth-se.diino.com/f.thompson/migrated_data/EandH . The conclusions from this report are given in section 8.2 and it is suggested that the additional total amount of emissions should be significantly less then 900 Gt otherwise damage to the oceans will occur.
Measurements of CO2 in the atmosphere are carried out at Mauna Loa observatory in Hawaii and these are shown below:-
Seasonal changes from changes in plant respiration are an obvious feature in the graph and the units on the y-axis are in parts per million of CO2 by volume. An upward trend is also evident and many people agree that this trend is too large to be explained by natural fluctuations.
A short digression to see how ppm units convert to Gt of carbon
Say we have 385 ppm by volume of CO2 in the atmosphere. Now since CO2 has a molecular mass of 44 whereas the averge mass of an "air" molecule is about 29 the mass concentration is 584 ppm. Taking the total mass of the atmosphere as 5 million Gt, there will be 2920 Gt of CO2 in the atmosphere. It is customary to quote only the carbon mass in a cycle diagram and we see a rounded off figure of 790 Gt given in the upper diagram. The atom carbon has a mass of 12 so 2920 x 12/ 44 = 796 Gt which is in reasonable accord with the figure given. It must be noted that for many centuries in the past the CO2 level remained at 280 ppm ( ie about 590 Gt of carbon in the atmosphere ) so recent years have deposited at least 200 Gt into the atmosphere. Many analysts think that the human population may have emitted more like 500Gt into the atmosphere and that the main cycles will have re-balanced to accomodate this large emission.
Global warming
Recently, a publication in Nature ( nature080919 on https://sth-se.diino.com/f.thompson/migrated_data/EandH ) has reported that humanity's carbon budget for emissions into the atmosphere should be set at one trillion tonnes of carbon (3.67 trillion tonnes of carbon dioxide gas) inorder to keep global warming to acceptable levels. Since, in the above paragraph, we see estimates suggesting that 500 Gt have already been emitted we only have a further 500 Gt left until the limit is reached. Putting a break on carbon emission (and fossil fuel use) is therefore essential and such cuts would mean that only one-quarter of our present fossil fuels should be used.
Recent data, 20 May 2009, given by Professor Ronald Prinn, of Massachussetts Institute of Technology suggests that, even with the above emissions, a temperature rise of 7.4 °C may be expected:
The red curves, mean and upper and lower 5% error curves replace the blue dotted curves. Clearly, anything above 500 ppm of carbon dioxide in the atmosphere would be catastrophic and this is due to happen in less than a life-time. Why not look at a few ideas given in Mouthpeace http://www.jp-shrewsburydiocese.org.uk , page 6, in issue 65, Spring 2009 - Eight ways to live gently on the Earth.
Perhaps carbon capture will have to be adopted with all haste. Steve Furnival has described a preliminary storage operation in the Sleipner gas field in Norway (see Physics World, page 24, September 2006).
Of course, nuclear power could heavily supplement oil, coal and gas power stations for the generation of electricity and this form of energy produces no CO2 .
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SE-HA lists five scenarios for the UK but, of course, Global Warming needs to be tackled on a Global scale.
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One activity that we must all join in with is
***conserving energy and hence cutting the carbon***
There are countless carbon calculators on the internet that we can calculate our carbon footprint for every moment of the day.
Low-carbon family
To see what savings can be made in a home the BBC (2007) followed the progress of the Hawksworth family, Castle Donington, Leicestershire, in their attempt to use less energy and hence reduce their carbon footprint. Lots of ideas were explored and their annual holiday was taken in Devon rather than Spain. The report below looks at fuel efficient cars and is only one report out of many included in the BBC Breakfast program.
BBC Breakfast Programme
Low carbon family: "Green" cars
So far we have looked at the pros and cons of travelling by road compared with rail. We've helped them in their search for a more environmentally friendly fridge. And we've helped make their home greener with new loft insulation and filling their wall cavities. Our experts have worked out how much they contribute to global warming and in our latest report, the Hawksworth family test drive some environmentally friendly cars. You can see all of our previous reports from the links to the right of this page - look for the 'see also' section
June's report:
In this month's report, Declan Curry takes motoring journalist Quentin Wilson to meet the Hawksworths at the Donington Park racing museum. They have been looking at greener cars, including hybrid vehicles that use a conventional petrol or diesel engine but also run on battery power generated by the car. There are many types of environmentally friendly car including electric, hybrids, bio-fuels and of course diesels. But simply buying a smaller, lighter car which needs less energy to power it can also help the environment. Buying a green car
You can find out more about buying a green car from Green Car Guide, a specialist website which has some useful advice on how to save money and help the environment. Declan Curry looked at five different types of green car in his report (watch again from the link to the right):
The Toyota Prius , was the car driven by Quentin Wilson in our item. It combines a petrol engine with an electric motor which charges its batteries. It qualifies for lower car tax (unlike a diesel) and is also exempt from the London congestion charge.
The second green car featured was an efficient diesel: the Citroen C4 which can be more economical, and as good as the best hybrid.Peugeot is planning to launch the first diesel electric hybrid.
The Ford Focus we featured was a bio-fuel five door car. Biofuels, biodiesel or ethanol, are more environmentally friendly than petrol or diesel because they come from renewable sources. But that in turn can still lead to damage to the environment in processing the fuel.
The fourth example was a G-Wizz electric vehicle which is the most environmentally friendly or carbon neutral green vehicle type. Of course its usefulness depends on being able to access a re-charging unit which can take between two and a half to eight hours.
Finally, Declan Curry looked at the BMW Hydrogen 7 - its only emission is water vapour but the technology for this type of green car is still being developed and currently, there are no models on sale.
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BBC Breakfast programme 2007
The Hawksworth family live in a 4 bedroomed detached house in Castle Donnington. They have five children, two cars and an enormous electricity bill!
In December 2006 BBC Breakfast launched an appeal for volunteers for a new Breakfast experiment, to see how easy it is to go green. They were looking for a typical family who were prepared to make some tough choices, to reduce their carbon footprint. After sifting through hundreds of volunteers the Hawksworth family was finally chosen.
The Challenge
For twelve months the BBC cameras followed the Hawksworths attempts to reduce their carbon footprint. Each month looked at a different 'green' aspect that could be utilised to decrease the family's carbon footprint.
The Solution
Mark Group became involved in the project when they were contacted by local Energy Efficiency Advice Centre to help the Hawksworths with their challenge. In the first of the programmes back in April of last year Bill Rumble, Mark Group Commercial Director, explained live on air that loft and cavity wall insulation would be the best first steps to reducing the Hawksworth's carbon footprint, and subsequently talked viewers and presenter Declan Curry through the process of installation.
Later in the year the Hawksworths moved closer to a full 'whole house' energy efficiency solution with the installation of a Solar Hot Water system through the Mark Group.
All of these measures combined to make a significant reduction in the Hawksworth's energy usage and their energy bills.
Before Insulation & Solar Hot Water After Insulation & Solar Hot Water
Gas usage 836 units (cubic metres) p.a. 498 units (cubic metres) p.a
( Gas usage in kWh) 8945 kilowatt hours p.a. 5328 kilowatt hours p.a.
Electricity usage 11,240 kilowatt hours p.a 6,821 kilowatts hours p.a
Monthly bill £125 £77
A total saving of £48 per month and a reduction of almost 40% in both gas and electricity.
Paul Hawksworth, commenting on the savings made, said: "Having these energy efficiency measures installed in the house has made a significant contribution to reducing our energy usage and the cost of our gas and electricity bills.
"The insulation seems to have made the biggest difference and we noticed almost immediately how much warmer the house was following the installation of the cavity wall and loft insulation.
"I would recommend to anyone to take these measures up as it's a complete win-win situation.
"You can massively reduce your energy bills while at the same doing your bit for the planet."
The Hawksworth's next green leap forward is to install an energy efficient condenser boiler as they set their sights on going from being the Low Carbon family to ultimately the Zero Carbon family.
And so to the good News
The family were aiming at a 25% reduction in their carbon footprint -- the reduction turned out to be 40 % . If this kind of saving could be translated thoughout the whole nation then our energy problems would be greatly reduced.
A similar story has been reported in USA. The National Geographical magazine ( March 2009 ) has an article by Peter Miller where he shows that his annual (per capita) carbon emission has been reduced from 24.6 tonnes to 11.5 tonnes. He, too, is now aiming for Zero Carbon. Details given in https://sth-se.diino.com/f.thompson/migrated_data/EandH .
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