Carbon footprint: a simple overview

A persons’ contribution to climate change can be measured and expressed with numbers. There are a lot of tools and a lot of data available on the internet. Although most of these figures include a lot of uncertainty, they can help find ways to reduce your carbon footprint by shifting from one activity to another. In this article, we want to help you understand the carbon footprint concept, so you can do whatever you decide to do with more knowledge.

The carbon footprint is a simple concept, it represents a measure of the full climate change impact of something, e.g. a country, an activity, a particular meal or a thing. But the name of the concept is rather confusing because carbon footprint usually is expressed in CO2e (where ‘e’ stands for an equivalent), which means it represents not only CO2 but all greenhouse gases (GHG). Just imagine how confusing it would be to compare bananas and apples if we took into account various greenhouse gases (and their quantities) that are emitted during their production. In CO2e, all greenhouse gases are converted into CO2 and it allows to compare various things easily. That is why, you should always pay attention to the carbon footprint notation when you are looking for information. Consider this: the amount of CO2 emitted per capita in New Zealand in 2012 was ~7 tons, it is almost as much as in the UK, in contrast, the amount of CO2e is almost twice as high as in the UK (see graphs on the right).

How did this happen? Due to the high level of agricultural production in New Zealand (most of it for export) our emissions profile is quite different from other developed countries. In New Zealand, methane and nitrous oxide (largely from agriculture) comprise over half of total national emissions (~55 percent), while the remaining emissions consist largely of CO2 (~43 percent; further 2% consists of synthetic GHG).

In order to control emission levels, New Zealand, like other developed countries, has set emissions reduction targets. New Zealand has a long-term target to cut emissions to be 50 per cent below the 1990 greenhouse gas emissions levels by 2050. It means that emissions have to be reduced from 81 million tons (2013 emission rate) to 30 million tons during next 35 years (in 1990 per capita GHG emission was 66.7 Mt CO2e). Given that around 65 percent of New Zealand’s emissions comes from transport and agriculture, let’s consider here two main ways to reduce your carbon footprint.

Movement. How you move around the city, country, or even around the world influences your carbon footprint hugely. Different means of transport emit a different amount of GHG, but that is not all that counts. Consider this: your cycle footprint depends on what you eat to restore energy lost due to exercise stress; your bus and car trip footprint depends on how many people share them with you; your electric car trip footprint depends on what source of energy is used to produce electricity.

The most efficient way of traveling is cycling. Assuming that we burn around 50 calories per mile, cycling a mile powered by bananas will cost you 65g CO2e and this figure will be even less if you are powered by apples from your garden. In contrast, if your energy comes from cheeseburgers, the emissions per mile are about the same as two people driving an efficient car.

Although electric cars seem like an attractive alternative to petrol cars, their carbon footprint is not straightforward: driving an electric car in New Zealand is not the same as driving it in Australia (see the map at the top). In countries where the proportion of renewable energy consumption is high, the carbon footprint of an electric car will be low. Consider for example Norway, the percentage of renewable energy consumption is ~ 60% and, as a result, a carbon footprint of electric cars is one of the lowest in the world – 74 g CO2e per km (or 118g CO2e per mile).

FYI: More than 850 Electric Vehicles (EV) registered in NZ;
142 public charging locations in NZ, one in Palmerston North;
7 different EV models available:
Nissan Leaf, Outlander SUV, Holden Volt, Toyota Prius,
Audi A3 e-tron, Tesla Model S and BMW i3;
1138 Tonnes of CO2 emissions saved this year.

Food is another big component of our carbon footprint. Food from overseas has a higher carbon footprint than locally grown because it includes emissions from transportation. However, meat (especially beef and lamb) and dairy products have the biggest carbon footprint, even though they are grown in New Zealand. Just compare 18 kg CO2e per kg of local beef with 0.069 kg CO2e per kilogram of local apples. Beef is climate unfriendly food: methane is produced by cows’

vital activities, nitrous oxide is released when fertilizer is applied to grass, CO2 is caused by tractors and other machinery. When choosing your meal it is also important to consider the ratio of g CO2e to kcal (see the graph on the right). For example the amount of energy obtained from rice and wheat is fairly similar, however, on average, the carbon footprint of rice is twice as high as that of wheat.

A precise estimate of our carbon footprint can be very complicated, but more important is that each of us can drop most of it. It does not mean that you need to immediately sell your car and move to a village to grow your own veggie garden. Knowing what constitutes your carbon footprint and how it is estimated might help you to develop a strategy that will be suitable for you. For example, if you cannot cycle to work, share your car with your colleagues – the more people, the more fun the trip, and the lower your footprint. If you are a meat lover and life without it seems miserable to you, switch from beef to chicken, as chickens carbon footprint is more than three times less than beef. These actions are clearly not a simple decision, but we need to be creative, to ensure a sustainable and at the same time enjoyable life. It is possible!
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