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One Tonne Life
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Tag: Carbon dioxide emissions

Chalmers offers tips to the family

The “Robinson” phase of One Tonne Life means that the family is making a huge effort to get close to the target of one tonne of carbon dioxide per person per year. Fredrik Hedenus and Anna Björk from the Chalmers University of Technology, who have been calculating the family’s carbon dioxide footprint from the very outset, put their heads together and wrote an open letter to the family and included a number of tips and suggestions – and we know that the family have already adopted several of the two experts’ suggestions:

“Hi Alicja, Nils, Hannah and Jonathan!

Today, eating out accounts for a relatively large proportion of emissions in the “food” category. If everyone in the family chooses vegetarian meals at work and at school, emissions from this category can be reduced to 0.3 tonnes of CO2 equivalent per person and year. Previous weeks with mixed dishes for lunch have put greenhouse gas emissions between 0.6 and 0.8 tonnes CO2 equivalent per person and year. Taking a lunch box from home is one way of further cutting emissions; just how much you reduce emissions depends on what your lunch box contains. Both Fredrik and ICA have offered suggestions for healthy and nutritious vegetarian meals on Onetonnelife.se.

Meat and dairy products currently also account for a large proportion of your total emissions. If you abstain entirely from meat, you can reduce your emissions by 0.2-0.8 tonnes CO2 equivalent per person and year, which corresponds to the emissions from previous weeks. By replacing dairy products with oats and soya-based alternatives, emissions can be cut still further. For instance, one litre of regular dairy milk produces emissions corresponding to 1.5 kg CO2 equivalent compared with one litre of oats-based grain milk which only produces 0.3 kg CO2 equivalent.

Driving an electric car or cycling instead of taking the bus is a good alternative since the bus currently accounts for about 0.05 tonnes CO2 equivalent per person and year out of the approximately 0.2 tonnes of greenhouse gases for the travel category. If instead this distance were to be covered by bicycle, emissions would be zero and if driven in the electric car, there will only be a small increase since the car is recharged with electricity produced from hydropower. The metro is still a good alternative since it produces low emissions, 0.7 grams CO2 equivalent/person km compared with the bus which gives 27 grams/person km.

Emissions from furniture production are shown in the “Other” category, as part of the “rucksack”. You can choose to do without certain items of furniture, and emissions will decrease proportionately with the amount of furniture the family can do without. At present, emissions for the household’s total complement of furniture are 0.3 tonnes per person and year. If you can do without one-fifth of the furniture in your home, emissions can be cut by about 0.05 tonnes.
Recreational activities currently account for 0.1 tonnes CO2 equivalent per person and year. In order to get rid of emissions from this category, you will have to decline indoor activities.

Good luck!

Anna Björk & Fredrik Hedenus”

Aviation’s climate impact

Aviation is often seen as a major source of greenhouse gas emissions. And it is true that as a private individual, flying is the single most climate-impacting activity you can undertake (if we disregard space travel). Having said that, we don’t fly all that often, and most people in the world never fly at all. From the global perspective, aviation accounts for only about 2% of total carbon dioxide emissions.

Last week an estimate was made of how much carbon dioxide the family saved by not flying to Switzerland for a skiing holiday. However, the real difference is actually less than the figures given in last week’s presentation. That’s because it is rather difficult to calculate exactly how much climate impact a flight causes. The amount of energy needed to fly one person over a distance of one kilometre depends to a considerable extent on the total length of the flight. Flying from Göteborg to Stockholm requires almost twice as much fuel per kilometre than flying to Beijing, for instance. And of course another vital parameter is how full the aircraft is.

The calculation only takes into account the CO2 emitted during the flight itself, but producing the fuel also requires energy. To this should be added the fact that airports and their various peripheral activities also cause emissions, but these emissions are seldom taken into account when calculating aviation’s total climate impact.

What is most complicated with aviation, however, is the warming caused by aviation apart from the carbon dioxide effect. For one thing, aircraft produce nitric oxide emissions. Nitric oxides have both a warming and a cooling effect on the climate. Warming comes from the fact that they help create ozone. When we talk about ozone we usually refer to the ozone layer in the stratosphere that prevents the sun’s ultraviolet (UV) light from penetrating through to the earth’s surface. However, ozone that is formed at lower altitudes in the atmosphere functions as a greenhouse gas. Furthermore, nitric oxides are also part of a process that breaks down methane, which is a greenhouse gas. If we take all these effects into account over a hundred-year perspective, nitric oxides from aviation will have a slight overall warming effect.

Aviation also causes contrails (also known as vapour trails, seen as white streaks in the sky). The density of these contrailsvaries with factors such as the aircraft’s altitude and ambient temperature. Just how much warming effect this has depends on whether you are flying at night or during the day, and whether the ground below is dark or light.

If we add together the effects of nitrogen oxides and vapour trails, we find that aviation causes an overall warming effect that is about 30% higher than that caused solely by carbon dioxide over a hundred-year period. This time perspective is important: carbon dioxide remains in the atmosphere for a very long time. Ozone remains for weeks, while contrails disappear after a few hours. However, while they are present, they have a significant warming effect. If we were to examine this comparison on a shorter time frame, we would have to increase aviation’s emissions by more than 30%.

To this should be added that contrails can later turn into more long-lasting cirrus clouds high up in the atmosphere. These clouds cause a rise in temperature down on the surface of the earth, although there is some uncertainty as to the extent to which these clouds are caused by aviation. If we also take these clouds into account, the warming effect of aviation is about 70% higher than that caused solely by carbon dioxide. But there are large uncertainties present.

If we now try to calculate the family’s trip to Geneva, the journey is 1680 km long, and flights of that length require about 0.40 kWh fuel per person-km. If we examine aviation fuel from a lifecycle perspective but disregard emissions from airport operations, we end up with 410 kg CO2/person for a return trip. If we now add in the effect of nitric oxides and contrails, the final figure is between 530 kg CO2 eq/person and 700 kg CO2 eq/person.

Emissions per km for the flight are about 158 g CO2 eq/km, which is comparable with doing the trip alone in a large car.

Fredrik Hedenus, Chalmers

What are the emissions from various types of produce?

After the surveys carried out of the Lindell family’s carbon dioxide emissions, it is becoming increasingly clear that food will be one of the big challenges. The produce they choose will be crucial in determining how close they get to 1 tonne of carbon dioxide emissions. So just how much carbon dioxide is created in the production of 1 kg of everyday foods such as meat, fish, shellfish, cheese, fruit, potatoes? When the experts at Chalmers do their calculations, they use the table below.

LCA data was used to create the table. This means that a life cycle analysis was undertaken for every item of food, encompassing emissions from production and processing as well as distribution.

The worst offender from the climate viewpoint is meat from animals that chew the cud (beef, lamb) at 26 kg, followed by mixed minced meat at 16 kg. Imported fruit is 11 kg, cheese 9.3 kg and pork 6.1 kg. This is followed by relatively low emissions for other produce, with potatoes and root vegetables at the very bottom of the table with extremely low emissions.

Read more
How CO2 is calculated One Tonne Life

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