What is a carbon footprint?

A carbon footprint is a way of measuring how much carbon a person, a group of people or type of process produces by burning fossil fuels. It is thought that there is a link between carbon dioxide emissions and global warming.  (see  main article by Dr. R. Roseff on the home page for more detailed information)

Global Warming and the Greenhouse Effect

The sun’s high energy radiation heats up the earth. The earth absorbs the heat and gives off low energy infrared rays. Many of these rays don’t make it back to space but are trapped in the atmosphere which surrounds the earth by greenhouses gases (the Greenhouse Effect). This heats the atmosphere which in turn heats the earth. If the concentration of these gases (primarily carbon dioxide and methane) is too high, the earth warms up too much. This is called Global Warming.

Scientists have warned that climate change is linked to the Greenhouse Effect and Global Warming. The level of carbon dioxide in the atmosphere is currently the highest for over 160,000 years, having risen by 10% in the last 30 years and it keeps on increasing due to human activity. Until recently a balance was maintained by the seas and forests which absorb large amounts of carbon dioxide.

However, the rainforests which have in the past converted much of the carbon dioxide into oxygen are gradually being felled to make way for farmland. The deforestation of the Amazon region in South America is particularly tragic as not only do less trees mean less photosynthesis (see below) but much of the wood is simply burned and this also gives off additional CO2.

Some other human activities which contribute to an increase in carbon dioxide levels:

·         breathing

·         rearing animals

·         burning wood and fossil fuels to make electricity for light, heating and air conditioners

·         burning fossil fuels to make petrol and diesel for transportation

·         felling forests

·         electricity for industrial processes to create consumer goods

Despite some scientists arguing that there is no proven connection between our increased production of carbon dioxide and global warming, the weight of evidence points to a link between human activity, such as our burning of fossil fuels and climate change.

The Carbon Cycle

The carbon cycle describes the process whereby carbon dioxide is removed from the atmosphere and returned to it. The carbon dioxide content of air is only 0.035% by volume.

Two processes dominate the carbon cycle:

1. Photosynthesis: plants take CO₂ from the atmosphere and convert it into oxygen.

2. Respiration: humans and animals breathe in air and exhale CO₂

glucose + oxygen          converts into        carbon dioxide + water + energy

Although other gases, such as methane, also are involved in the greenhouse effect,  carbon dioxide is the main contributor and therefore now used as an environmental measure, carbon footprints.

Carbon Footprints

It is now possible to calculate your own carbon footprint, a measure to what extent you personally are contributing to Global Warming. The Kyoto Protocol encourages countries to reduce their greenhouse gas emissions by 5.2% less than in 1990 by the year 2012. However, many countries did not agree to do this as they were afraid it would cost too much. Environmentalists say that even if we were to reduce to the recommended levels, it would be too little.

If you are interesting in doing a simple test, try these links:

www.carbonfootprint.com

www.mycarbonfootprint.en/

Why has our output of CO2 increased so much in recent times, 10% in the past 30 years alone? A comparison of the cider making process then and now sheds light on this question.

What is the carbon footprint of apple orcharding?

Dr. Rebecca Roseff calculated CO₂ emissions for activities surrounding the making of apple cider. She has written the article, “What is the carbon footprint of cider?” which you can access from the homepage. All the details of the calculations are given in her article.

 Before Industrialization:

Dr. Roseff states that before industrialization the production of cider would not have left much of a carbon footprint:

“In the past producing cider would have had virtually no carbon footprint at all, because it was done using manual labour which gets its energy from plants which take as much CO₂ from the atmosphere as they give off (photosynthesis). It used no fossil fuels (coal, oil, gas, etc.) The crushing was done by horses or people pushing a big stone around a stone trough (called a mill) and the energy for this was obtained by food grown ultimately from plants. The cider was produced in wooden barrels produced from trees that are a renewable resource. The only non renewable resource in the process would have been the coal used to smelt and forge the iron that created the axes and other iron tools. Before the 19^th century this would have been smelted with charcoal, so even this would have been a renewable resource.”

To summarize: Manual labour, people eat food primarily originating from plants, even cows and chickens etc. eat plants People walked to work or rode a horse The pressing process was carried out by people and horses The barrels were made from renewable sources Only the iron tools were made of non renewable resources No chemically produced fertilizers or pesticides were used The cider would have been pressed and made near the orchard

Since Industrialization:

There are two processes in making cider: orcharding (growing and picking the apples) and cider making (pressing, fermenting, blending, bottling etc.)

 Orcharding carbon footprint: A sample orchard of 100 acres (51 ha) near Leominster in Herefordshire was used for calculating the relevant figures.

• Employees travelling to work: an average of 1,117 journeys a year, an average of 55 miles using 4 cars.
• The apples are taken by lorry to a factory in Ireland. This involves 63 lorry trips travelling 371 miles by land and 100 miles by sea for a one way journey.
• Fertilizers and pesticides: even though most apple growers are trying to reduce fertilizers and pesticides, some has to be used by commercial growers to sustain quality and yield. Producing fertilizers takes a large amount of fuel.
• Machinery is used in the orchard.

Even though the machinery was not included in the calculations, the total amount of carbon produced by this orchard per year is about: 119.4 tonnes or 435.6 tonnes of CO₂.

This number must be offset by the amount of carbon dioxide that gets absorbed by orchards:

• In 25 years one apple tree will absorb about 1 tonne of carbon dioxide. Modern bush orchards have a life of 50 – 80 years and are planted at 120 – 180 trees per acre. If you calculate an average of 150 trees per acre the carbon dioxide absorbed per year would be 600 tonnes or 164 tonnes of carbon.

CO₂ per year produced by orcharding process: 435.6 tonnes

CO₂ per year absorbed by same orchard:            600 tonnes

In effect, even modern commercial orcharding does not leave a big footprint, however, when the trees die, they rot and give off further CO₂, which was not taken into account in the calculations. But what these calculations do show is the importance of trees to the carbon cycle, and ultimately global warming and climate change.  Also keep in mind that the cider making process itself will leave a carbon footprint, because nowadays cider making is industrialised and mechanised, from the pressing to the bottling process.

Sources of Information

Here Dr. Roseff explains how she gathered her information:

“To find how much carbon is used in growing apples I asked an orcharder (John Moss, of Kimbolton) to give me a summary of the pesticides, herbicides, fertilisers and fuel used, and the amount of apples produced.  Orcharders are required to keep records of what they spray and when, and they keep forms, filling in how much is used.  The amount of fertiliser and fuels used is also kept, the orcharder needs this to balance the annual accounts. 

The amount of apples produced is found from the amount sold.  The apples are sold by the lorry load and the orcharder is paid per lorry load, so s/he keeps good accounts.

Travel to work fuel is judged from the number of employees, the distance they travel and the number of days they work.

How to calculate the carbon emissions of car journeys:

Different cars use different amounts of fuel.  The amount they use can be found yourself, by filling a car tank to the top, noting how much fuel is put in and the mileage on the car dash board.  The next time the car is filled, make sure it is filled to the top, note how much is put in and the mileage on the car dash board.  Then take one figure away from another and see how far the car has gone for how much fuel.

Petrol produces 2.9kg of carbon per gallon (there are 4.55 litres in a gallon).  Another way of expressing this is 2.5kg of CO₂ per litre of fuel.  Work out how far the car went for one litre of petrol and then how much per one km. 

Example  Your car went 40 miles on  one gallon 40 x 1.60934 is 63 km (convert into km) One gallon is 4.55 litres 63 divided by 4.55 is 13.8 km for one litre, this is 2500 grams CO2 per 13.8 km Divide 2500 by 13.8 km gives 181gm 2500 grams CO2 per 1km, well over the EC guidelines (of 130g/km travelled). Another way of finding the CO2 output of your car is to look it up on the website www.vcacarfueldata.org.uk.

Sources of Information:

Cider: The information about the amount of cider produced per year comes from the National Association of Cider Makers website www.cideruk

Other websites dealing with carbon footprints:

• www.carbonfootprint.com

• www.carbonconversation.co.uk

• www.carbontrust.co.uk

• www.carboncalculator.co.uk

• www.resurgence.org/carboncalculato

Books:

Chemistry of the Environment (A level Chemistry), E.N. Ramsden, Stanley Thornes (publ.) ltd., 1996.

The Usborne Internet -linked Introduction to Weather & Climate Change, ed. Kirsteen Rogers, 2004

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