Carbon Methodology

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:

  1. the information we can collect from you in order to predict your environmental impact; and

  2. 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

Drive Less, Bike More


The impact of each check-in is calculated by comparing the emissions generated from travelling on a bicycle to the user's main method of transport set during onboarding. We assume that the length of the trip is the average commute length set by the user in the onboarding quiz. For example, if a user generally travels 10km a day for work in a petrol car, and decides to switch to a bicycle for three of those trips next week, the carbon savings would be: [ 30km x emissions per KM in a petrol car (180 grams) ] - [ 30km x emissions per KM on a bicycle (5 grams) ] for a total carbon reduction of 5.25 Kg CO2e for that check in.




Compost my Food Waste


The impact of a successful check-in is calculated from the annual Australian average for compostable food waste emissions generated in landfill (~240kg CO2e / year). Composting food waste is known to effectively reduce methane emissions caused by anaerobic decomposition to 0, so we take this sum and divide by 52 to get the estimated CO2e saved by a week of composting. Someone who reported as ‘sometimes’ composting their food waste in the on-boarding quiz will have a lower check-in impact because they were already composting about 50% of their compostable food waste. Compostable food = food that can be composted. So for wasted food that isn’t typically compostable - e.g most meat and dairy - this is not included in the assumed impact (we assume this is still going in the bin). This habit, once mastered, assumes that of the compostable food you were previously putting in the bin, you are now composting all of it.




Eat a Vegan / Vegetarian Meal


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. Using this data, we can calculate the impact of substituting each individual meal for the user's diet type set during onboarding for a vegan or vegetarian alternative. For example, if a user with a mainly pescatarian diet who also avoids dairy decided to switch to 4 vegan meals in the next week, we would calculate the savings to be: [ 4 x emissions per pescetarian meal ( excluding dairy, 1303 grams ) ] - [ 4 x emissions per vegan meal ( 963 grams ) ] for a total emissions reduction for that week of 1.36 Kg CO2e .




Hang Dry my Clothes


The impact of this habit is calculated using energy consumption statistics of typical Australian washers & dryers. We assume that larger households use larger appliances (8kg standard electric capacity for large households, & 5kg standard electric capacity for small households). From this we estimate the energy consumption per washing load logged in the habit tracker to be: 1.6KWH Per load of washing dried in a small electric dryer 3.2KWH Per load of washing dried in a large electric dryer We then multiply the total energy usage of a cycle by the CO2e per KWH equivalence for the state the user lives in and scale it down if the user has a renewable energy source at home.




Cold Wash my Clothes


The impact of this habit is calculated using energy consumption statistics of typical Australian washers & dryers. We assume that larger households use larger appliances (8kg standard electric capacity for large households, & 5kg standard electric capacity for small households). From this we estimate the energy consumption per washing load to be: 1.45KWH Per warm wash load in a small washing machine (9.1Mj for gas water heating) 2.95KWH Per warm wash load in a large washing machine (15.3Mj for gas water heating) We then multiply the total energy usage of a cycle by the CO2e per KWH equivalence of the state the user lives in and scale it down if the user has a renewable energy source at home (CO2e per Mj if the user has gas water heating).





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 built0in 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


We have set a default assumption that if the user completes this program, they eat an additional 16 vegan meals in total. That equates to roughly two vegan meals per week for 8 weeks (from a total of 168 meals over 8 weeks). These 16 meals cause 15.4kg CO2e. So the impact from this program comes from taking the user’s existing CO2e footprint for 16 meals based on their current diet (as reported in the quiz) and then subtracting the emissions caused by the 16 vegan meals to arrive at the assumed program impact figure.

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.
Caveat: We may have under-estimated or overestimated emissions impact from this program, depending on how much more plant-rich food the user starts eating during and after the program. We’ll be introducing a feature that allows users to track their plant rich meals through a habit tracker, which will remove the need to estimate meals and allow the user to report this figure themselves. This will significantly improve the accuracy of this program’s calculated impact.




Food, Not Waste


This program, once completed, assumes that of the compostable food you were previously putting in the bin, you are now composting 80% of it. Someone who reported as ‘sometimes’ composting their food waste in the on-boarding quiz will have a lower program impact because they were already composting about 50% of their compostable food waste. Compostable food = food that can be composted. So for wasted food that isn’t typically compostable - e.g most meat and dairy - this is not included in the assumed impact (we assume this is still going in the bin).




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


For the ‘Big Switch Off’ challenge, we assume the user eliminates 3% of their energy usage for the year. This assumes they continue with the practice of switching most appliances off at the power point when not in use and switching off lights when not in use. This 3% reduction in total home energy consumption is taken from the Australian Federal Government’s AusHome.Gov figures. For the ‘Let There be LED Light’ challenge, we assume that if you have completed this challenge then the carbon footprint associated with your lighting (based on the energy that your lights consume) is reduced by 80% as a result of switching to LEDs. This 80% reduction in energy consumption for LED lights compared to standard lights is based on figures from the Australian Federal Government’s Aushome.Gov site. For the ‘Natural Heating Hacks’ challenge, we have assumed that the energy usage associated with climate control of your home (that is, the energy that goes into heating and cooling your home) has been reduced by 10% through better insulation of windows (ours is a conservative assumption). We have taken this percentage change in climate control-related energy usage reductions due to better window insulation from the Aushome.Gov website. For the ‘Draughts: Seek and Destroy’ challenge, we have assumed that the energy usage associated with climate control of your home (that is, the energy that goes into heating and cooling your home) has been reduced by 7.5% through better insulation of windows and doors through draft proofing (this is a conservative assumption). We have taken this percentage change in climate control-related energy usage due to better insulation through draught proofing from the Aushome.Gov website. For the ‘Switch to carbon neutral’ challenge’ we have assumed a 82% reduction in the emissions associated with the user’s home energy usage. For the Invest in GreenPower challenge, we have not assigned any impact to the user switching to GreenPower since this step is 1) optional and 2) we do not know the percentage of GreenPower the user is now buying month-to-month to effectively offset their electricity-related emissions.




Green Finance


We assume that by marking the challenges in this program as completed, that you have switched your banking over to a fossil fuel-free bank and you have switched your superannuation over to a fossil fuel free superannuation fund. By surveying you about your average income in the on-boarding quiz, and using ABS data on income quintiles, we generate an estimate for your assumed financial savings (based on the typical amount of money saved for someone with your household income), and apply a carbon emission factor (based on Tomorrow Co. emissions intensity figures for financial services and localised data) to this dollar amount to create the initial carbon footprint for your money in the bank. At present, we assume that if you switch to a green bank, your money has 80% less emissions intensity associated with it than in a regular bank. For banks such as Beyond Bank, this would in reality involve a 100% reduction in emissions associated with your bank account money, because it is a fully carbon neutral bank. CAVEAT: Benchmarking emissions associated with financial services, specifically, the average emissions intensity of your savings account dollars and super balance, is difficult. It is also hard to estimate the difference in embodied emissions on average when you switch to a green bank or super fund. We are working hard to improve the accuracy of our assumptions here through additional research over the next few months.




Sustainability at Home


A lot of the challenges in the Sustainability at Home program teach foundational skills to support a more sustainable lifestyle, particularly with regard to habits that significantly reduce food waste. We’ve assumed for the food-related challenges, that users will continue the behaviours they learn in each challenge for the remainder of the year, cooking stock from time to time, picking some veggies occasionally and sometimes making jams. We have assumed a 15% reduction in food waste if the user learns how to make stock and continues to do so through the ‘Stock up’ challenge, which equips the user to make stock from vegetable scraps and meat scraps that would otherwise go in the bin, and with the ‘Pickled Tink’ challenge to pickle vegetables rather than throwing them in the bin, we assume a 5% reduction in total food waste. We have assumed that from the ‘We’re Jammin’’ challenge to make your own jam, and the ‘Growing from scrap’ challenge to grow vegetables from food scraps, that users achieve an overall reduction in the carbon intensity of their meals of 1% for each of these challenges that are completed. Similarly, we assume you continue to use your beeswax wraps and no longer purchase clingwrap, which leads to a 10% reduction in plastic waste (and therefore a 10% reduction in the emissions associated with your plastic waste), and that from the mending activities performed in the Clothes Mending challenge (we assume mending roughly 3-4 T-shirts or sweaters on average), you avoid replacing those items and extend their lifetime.




A Worm Farm for Any Space


For this program we start with the Australian average for compostable food waste emissions generated in landfill. Composting food waste is known to effectively reduce methane emissions caused by anaerobic decomposition to 0. We assume that completion of this program results in a week of composting their food waste, so we take this sum and divide by 52 to get the estimated CO2e saved. Someone who reported as ‘sometimes’ composting their food waste in the on-boarding quiz will have a lower impact because they were already composting about 50% of their compostable food waste. Compostable food = food that can be composted. So for wasted food that isn’t typically compostable - e.g most meat and dairy - this is not included in the assumed impact (we assume this is still going in the bin). We recommend using our habit tracking tool on completion of this program, which will allow you to incrementally track the impact of composting beyond that first week.




Green your Laundry


The impact of this program is calculated using energy consumption statistics of typical Australian washers & dryers. We assume that larger households use larger appliances (8kg standard electric capacity for large households, & 5kg standard electric capacity for small households). From this we estimate the energy consumption per washing load to be: 1.45KWH Per warm wash load in a small washing machine (9.1Mj for gas water heating) 2.95KWH Per warm wash load in a large washing machine (15.3Mj for gas water heating) & 1.6KWH Per load of washing dried in a small electric dryer 3.2KWH Per load of washing dried in a large electric dryer We assume that as a result of completing this program, the user has cold washed and air dried three loads of washing, so we multiply the total energy usage of three cycles by the CO2e per KWH equivalence of the state the user lives in (CO2e per Mj if the user has gas water heating). We recommend using our habit tracking tool on completion of this program, which will allow you to incrementally track the impact of cold washing and air drying your laundry after those first three washes.





Habit Impact Assumptions

Drive Less, Bike More


The impact of each check-in is calculated by comparing the emissions generated from travelling on a bicycle to the user's main method of transport set during onboarding. We assume that the length of the trip is the average commute length set by the user in the onboarding quiz. For example, if a user generally travels 10km a day for work in a petrol car, and decides to switch to a bicycle for three of those trips next week, the carbon savings would be: [ 30km x emissions per KM in a petrol car (180 grams) ] - [ 30km x emissions per KM on a bicycle (5 grams) ] for a total carbon reduction of 5.25 Kg CO2e for that check in.




Compost my Food Waste


The impact of a successful check-in is calculated from the annual Australian average for compostable food waste emissions generated in landfill (~240kg CO2e / year). Composting food waste is known to effectively reduce methane emissions caused by anaerobic decomposition to 0, so we take this sum and divide by 52 to get the estimated CO2e saved by a week of composting. Someone who reported as ‘sometimes’ composting their food waste in the on-boarding quiz will have a lower check-in impact because they were already composting about 50% of their compostable food waste. Compostable food = food that can be composted. So for wasted food that isn’t typically compostable - e.g most meat and dairy - this is not included in the assumed impact (we assume this is still going in the bin). This habit, once mastered, assumes that of the compostable food you were previously putting in the bin, you are now composting all of it.




Eat a Vegan / Vegetarian Meal


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. Using this data, we can calculate the impact of substituting each individual meal for the user's diet type set during onboarding for a vegan or vegetarian alternative. For example, if a user with a mainly pescatarian diet who also avoids dairy decided to switch to 4 vegan meals in the next week, we would calculate the savings to be: [ 4 x emissions per pescetarian meal ( excluding dairy, 1303 grams ) ] - [ 4 x emissions per vegan meal ( 963 grams ) ] for a total emissions reduction for that week of 1.36 Kg CO2e .




Hang Dry my Clothes


The impact of this habit is calculated using energy consumption statistics of typical Australian washers & dryers. We assume that larger households use larger appliances (8kg standard electric capacity for large households, & 5kg standard electric capacity for small households). From this we estimate the energy consumption per washing load logged in the habit tracker to be: 1.6KWH Per load of washing dried in a small electric dryer 3.2KWH Per load of washing dried in a large electric dryer We then multiply the total energy usage of a cycle by the CO2e per KWH equivalence for the state the user lives in and scale it down if the user has a renewable energy source at home.




Cold Wash my Clothes


The impact of this habit is calculated using energy consumption statistics of typical Australian washers & dryers. We assume that larger households use larger appliances (8kg standard electric capacity for large households, & 5kg standard electric capacity for small households). From this we estimate the energy consumption per washing load to be: 1.45KWH Per warm wash load in a small washing machine (9.1Mj for gas water heating) 2.95KWH Per warm wash load in a large washing machine (15.3Mj for gas water heating) We then multiply the total energy usage of a cycle by the CO2e per KWH equivalence of the state the user lives in and scale it down if the user has a renewable energy source at home (CO2e per Mj if the user has gas water heating).





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