How does the One Small Step Carbon Footprint Calculator work?
Our carbon accounting system is a work in progress. While we’ve put a lot of work and thought into the current model, its accuracy is constrained by:
the information we can collect from you in order to predict your environmental impact; and
the reliance we have presently on self-reporting by users without access to real-world data on things like your energy usage, car usage or kgs of waste you create each week.
That said, we think the model we’ve built is promising and is only going to get better with time, especially as we look to partner with organisations where we can collate observed data. For example, with your consent, integrating your energy usage numbers through a partnership with your energy provider, or asking questions that help us figure out exactly how often you’re driving your car and it’s fuel efficiency.
We’ve outlined the methodology we’ve used below to calculate your quiz results in the One Small Step app, and the default assumptions we’ve used to figure out the environmental impact you can achieve by completing the current programs in the One Small Step app.
We are continuously improving this calculator, and we will update this page with changes to our model as we augment it.
Calculating your carbon footprint: methodology and assumptions
We combine the information you provide in your answers to the on-boarding quiz and Australian Bureau of Statistics (ABS) census reports on Australian income, expenditure, water & electricity usage to get a highly detailed breakdown of what your consumer habits are likely to be. These figures are influenced by what state you live in, how many people you live with, and what income bracket your household applies to.
We then run these energy, water, gas, fuel, food & spending figures through a consumption-based accounting model provided by Tomorrow co. to create an annual carbon dioxide equivalent (CO2e) footprint score in each category. This model is used globally and provides localised conversion factors for many countries, including Australia. We then take care to improve accuracy by using recent, Australian-specific data in place of global averages.
The CO2e footprint data we use is based on ‘full life-cycle analysis’, meaning it takes into account the CO2e produced during material processing, manufacturing, distribution, use, recycling & final disposal of the things you consume. This paints a more complete picture of the effort and consequences behind consumer goods & services, allowing for more impactful decision-making when trying to reduce our carbon footprint.
Carbon Footprint Quiz Methodology
We use information about your household type, number of residents, occupancy status, income and location to determine which of five electricity usage groups, detailed in the ABS residential electricity usage survey, you would most likely belong to. Your annual usage, (measured in KiloWatt hours, or KWH) is then adjusted to account for any gas water heating, carbon offsetting & sustainable energy sources.
We calculate carbon intensity on a per meal basis, using the diet information you have provided. Each diet type has its own adjusted carbon intensity value provided by Tomorrow co., which takes into account age and sex in calculating an average daily intake. The values are further adjusted depending on whether you eat beef and/or dairy and if the food is sustainably sourced. We then calculate the carbon intensity of alcoholic & non alcoholic beverages using the same method as detailed in the purchases category, and add that to get the final score.
We start with the Australian household food & plastic waste averages, add in any disposables from the purchases category (e.g. paper towels, toilet paper etc) and then calculate the carbon intensity using the figures provided by the Tomorrow co. products database. We use adjusted life cycle stats for each waste material type, including average recycling rates. Your final score is then offset by the percentage of your food that is unpackaged & whether you compost your food waste.
The Bureau Of Meteorology estimates the carbon footprint of supplying Australian homes with water in each major district in the urban national report for water utilities. We take the mean of all major districts in each state to get a state average. This does not include the intensity of heating the water, so we have subtracted the total intensity of water heating (gas or electric) from the energy category and added it here for a more accurate look. We then distribute the score using yourhome.gov estimates to determine what percentage can be attributed to outdoor use, showers, toilet, laundry etc.
What is CO2e?
Why do you use a consumption-based accounting model?
What is the end goal?
Calculating the estimated impact of One Small Step programs & habits
We have made a series of assumptions about the impact of our existing carbon footprint reduction programs & habits. These are outlined here. All data sources listed are publicly accessible. We think the assumptions we’ve made to calculate program impacts are reasonable and also relatively conservative.
However we’ll be able to rapidly improve the accuracy of our assumptions with regard to program impacts when we introduce a feature that provides our users with more granular control over their personal carbon profile. Until then, wherever the onboarding profile lacks detail, we use built-in default assumptions about user behaviour and how often users carry out specific pro-environmental behaviour as a result of completing One Small Step programs & habits.
Impacts scale to fit your existing carbon footprint profile
For different users, actions will have different impacts. This is because One Small Step users have different carbon footprint profiles that affect the potential impact of different programs & habits.
Here’s an example of how this works:
Mike uses the One Small Step app. When he does the quiz, he reports that he is a regular meat eater. When Mike completes the ‘Discover Plant-based Food’ challenges and starts switching to vegan alternatives, we assume he commits to eating two vegan meals per month for 2 months. By calculating the difference in intensity of those vegan meals as compared to his current diet we are able to estimate his impact.
When Chrissy does the quiz, she reports that she is a vegetarian. By using her current diet in the calculation, we get a lower, but more accurate, potential impact for Chrissy than for Mike.
This convention is used wherever possible to help keep the total impact of completing programs consistent with who you are, and the sustainable habits you already have committed to prior to coming into the app.
Program Impact Assumptions
Discover Plant-Based Food
If the user is already vegetarian or pescatarian, then their total CO2e impact is lower from this program, because the emissions associated with their existing meals were lower than for a user who regularly eats meat and dairy.
Food, Not Waste
On Yer Bike
We have assumed for this program that the user, after completing the program, starts riding one day a week. We calculate the impact of this weekly ride based on the user’s reported commuting distance and their usual mode of transportation (as reported in the on-boarding quiz). So if the user ordinarily commutes 5-10km each day in their car, we take the assumed carbon footprint from that single car trip and remove it - since now the user is using their bike to make that trip instead of driving, just once a week. If the user is usually catching public transport, the impact of this program footprint will be lower, but only because they already had lower transport-related emissions due to their use of public transport instead of using a single-passenger vehicle. If the user reports that they ordinarily walk as their main mode of transportation, then the impact from this program is slightly negative (since you generate zero emissions from walking and a tiny amount of emissions from cycling due to the embodied emissions in the purchase of the bicycle).
Caveat: We may have under-estimated or overestimated emissions impact from this program, depending on how much more frequently the user starts cycling during and after the program. We’ll be introducing a feature that allows users to track the frequency of their cycling and walking trips through a habit tracker, which will remove the need to estimate rides for the year, and allow the user to report this figure themselves. This will significantly improve the accuracy of this program’s calculated impact.
Energy Saving at Home
Sustainability at Home
A Worm Farm for Any Space
Green your Laundry
Habit Impact Assumptions
Drive Less, Bike More
Compost my Food Waste
Eat a Vegan / Vegetarian Meal
Hang Dry my Clothes