How is your carbon footprint calculated?

My home, of two adults, a little boy and two cats, occupies a confusing position in the world: we are climate villains or conscious citizens and focused on sustainability.

On average, we create an annual equivalent of 22 tons of carbon dioxide (t / CO₂e, a figure that incorporates a variety of greenhouse gases, from carbon to methane to nitrous oxide), according to 10 different carbon calculators. That’s a very respectable 7 t / CO₂e per year each, considering that the national per capita average is 19 t / CO₂e (a problematic figure, but more on that later).

We get there by inputting a variety of data including total annual electricity usage or kilowatt hours used ($ 1,323 or 4121 KWh), our estimated car use (11,569 km in 2021), an estimate of how often we eat meat. (three, four times a week? Do we include nursery lunches?), number of flights and various other movements.

We are climate villains or citizens who are conscious and focused on sustainability.

Each took between five and 20 minutes. Some calculators were extremely vague in detail, such as the Global Footprint calculator, which consisted of guessing where we sat on a line from ‘never’ to ‘very often’, while others required forensic analysis of electricity bills and one-year water and some mental arithmetic, such as Carbon Neutral’s request for container size, collection frequency, and fill level at collection.

My household average combines a wide range of readings from a low of 8.6 t / CO₂e to 42 t / CO₂e per year.

So, are we as much a part of the problem as our Boomer parents who own mansions, mansion owners, and love travel abroad? Or can we remain in the safety of complacency because we are actually quite amazing?

The answer lies, of course, somewhere in the middle. Welcome to the world of carbon calculators – an important but opaque set of websites that draw on a variety of methods and data sources used to calculate your personal footprint and, for some calculator creators, an incentive to make that number be so big and scary. looking as possible.

How simple is too simple?

Carbon calculators return the carbon footprint of a person or company, which is an estimate of the total carbon emissions generated by that person or entity during a specific period of time.

Cosmos measured nine carbon calculators designed just for people that were either made in Australia or produced a number specific to Australia.

Calculator Annual emissions of Williamson households, (t / CO₂e and t / CO₂ *) Options offered by the calculator owner to reduce the carbon footprint
Carbon Positive Australia 22 t / CO₂e carbon offsets
Carbon neutral 41.72 t / CO₂e carbon offsets
Global Footprint Network 10.2 t / CO₂
Super active 40.3 t / CO₂e Offer to switch to your retirement fund
Tree Project 16.6 t / CO₂e
Trail 15.6 t / CO₂e carbon offsets
Carbon click 23.7 t / CO₂e carbon offsets
WWF 16.9 t / CO₂
Climate Hero 8.6 t / CO₂e carbon offsets

* Most calculators use CO₂e, which covers a specific range of gases, but some focus only on carbon dioxide (CO₂).

Carbon calculators are simple by necessity.

Most people won’t know exactly how many miles they drive or fly in a year, nor will they mind adding up their precise electricity use per kilowatt hour. But with simplicity comes inaccuracy, as the level of detail fails to capture the full scope of a person’s lifestyle and thus their carbon cost.

The Australian Greenhouse Calculator (AGC) was, when it was still working, the most comprehensive piece of personal carbon accounting software. It was backed by a 99-page outline of how each part of the calculator worked and, according to its creator, asked for extensive and detailed information.

Carbon calculators are simple by necessity.

“That’s the problem: most of them are very simple,” says Alan Pears, industry principal investigator at RMIT and creator of AGC.

Let’s say I’m about to renovate my house. What should I do? Or how should I review the types of food that I should eat? Most of them are too simplistic.

“If you look at the wine industry, emissions per bottle of wine can vary by a factor of 10, because high-volume winemakers are very efficient compared to a boutique one.”

Winemaking is just one industry where bottle weight and electric tractors are part of a drive to go green, and it means that a number of questions are becoming increasingly difficult to measure.

An example is if you eat meat, because Australian sheep meat was carbon neutral by a measure in 2020 and the livestock industry as a whole is aiming to reach net zero by 2030.

Inside the black box

Different calculators use different data and make different assumptions, based on national averages that are unlikely to reflect an individual’s lifestyle.

The average emissions attributable to each individual Australian in 2020 were 19.4 t / CO₂e, as total national emissions reached 499 million tonnes of CO₂e for a population of 25.69 million. The World Bank estimate was 15.5 t / CO₂e in 2018.

All carbon calculator comparisons fall between these two figures. But this figure is not an accurate benchmark for measuring your personal emissions, because it includes ‘country emissions’ in which you did not participate.

The average emissions attributable to each individual Australian in 2020 were 19.4 t / CO₂e

Carbon Click is a calculator that incorporates these emissions into personal footprints, including emissions from sources such as utilities, infrastructure, and exports.

“These ‘country emissions’ are included in your results and can make your footprint appear higher than you would expect from your own activities,” he says. “However, it is imperative to include them to get a true measure of a citizen’s footprint.”

Another problem is calculators that don’t open the black box at all. Carbon Positive has a detailed list of where it takes its data from, while Carbon Neutral asks its users to review the National Greenhouse Account Factors to find out what assumptions it uses. Global Calculator Trace only claims that it uses “GHG protocol guidelines” and “emission factors and reference data from public sources”.

the data problem

In a world awash in information, finding data that is granular enough to paint an accurate picture is becoming increasingly difficult.

“To be honest, that’s the biggest challenge with carbon calculators – finding reliable data sources,” says Jess Fitzgerald, carbon project coordinator at Carbon Positive and architect of their calculator.

Fitzgerald used government data, such as national greenhouse accounts factors, to rely on a verified number specific to Australia.

Much household-level data is no longer available, because major surveys like the Census or others conducted by the Australian Bureau of Statistics (ABS) no longer look at the fine print of how households function. The ABS 4602 category covers environmental issues and used to include a survey of how many refrigerators and washing machines Australians owned and how often they were used weekly; Today, Monash University researcher Yolande Strengers and Energy Consumers Australia collect such data in a more limited way. .

“To be honest, that’s the biggest difficulty with carbon calculators: finding reliable data sources.”

Jess Fitzgerald, Carbon Positive

“Spending on groceries and spending on clothing and consumables would be very helpful, and it seems like that data used to exist, especially around spending on groceries, but I couldn’t find it,” says Fitzgerald.

“In the future, I’m not sure how we will manage [reduced public household data]. “

There are two approaches to collecting the type of data required for a sufficiently accurate carbon footprint calculator: The vast majority of number processors use top-down data like Carbon Positive, which spits out a number of emissions, but not what activities contribute to the result. .

Pears’ calculator used a bottom-up model, which was made possible by his existing knowledge of the use of micro-energy from household appliances such as refrigerators and televisions.

“No other calculator allows you to see a washing machine’s cycles or how often I use it, or essentially many of the options or factors that I can change,” he says.

“Most of the methodologies are bottom-up models. So for example, if you put a refrigerator in a small space, the model will calculate the additional heat generated in that space and [how much power is lost by] opening the door. Things that people are really interested in. “

Conflicts of interest

Once you have your carbon footprint calculation, many Cosmos-tested carbon calculators will give you the option to offset that figure or, in the case of Active Super, switch to your retirement product.

This is useful, since you don’t need to search the internet to find a way to mitigate the damage you’re supposedly doing to the Earth, and a huge conflict of interest – those companies have an incentive to make their mark. they seem more alarming, if not higher as a total, than they could be otherwise.

“That’s why it’s important that more calculators are very transparent in the way they calculate,” says Fitzgerald.

Without delving into where your underwear was made and what emissions are attributable to tonight’s rotisserie chicken, a ballpark number is the best and most useful piece of information most people need to make lifestyle changes.

But before you open the black box and find out for yourself why the emissions from your trips are so much higher than expected (it was those flights to the Sunshine Coast that you didn’t offset), a ballpark number is the best you can hope for.



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