Carbon Savings Calculation Methodology
Carbon Wallet aims to make green lifestyle count. It empowers users to track their Carbon Savings based on their green actions in three areas namely recycling, green dining and plant milk.
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To ensure robustness, an independent consultant, RESET Carbon, has been appointed to develop the calculation methodology of Carbon Savings based on scientific research studies and their professional expertise.
1. Definition of Carbon Savings
Carbon Savings represent carbon emissions avoided by practising a green action when compared with its baseline action (e.g. consume a vegetarian meal vs a non-vegetarian meal, recycle a plastic bottle vs disposal at landfill).
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Carbon Savings are calculated by comparing carbon emissions of a green action with its respective baseline action:
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Carbon Savings = Carbon Emissions Baseline - Carbon Emissions Green Actions
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2. Calculation Methodology
2.1 Overview
The following table presents the Green and Baseline Actions for respective area based on which Carbon Savings are calculated.
2.2 Recycling
Carbon Savings are calculated by comparing the emissions associated with the green action of recycling an item against the baseline action of disposing of it at landfill. The emission factors of both actions per item are determined with reference to different studies and databases, which includes lifecycle assessment (LCA) results published in a European Study of liquid containers and an evaluation of emission reductions associated with recycling.
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Carbon Savings for recycling are calculated on a per-unit basis. A standard volume has been selected as the “representative volume” for each item for the calculation. For personal care plastic bottle, the representative volume and weight are estimated based on sampling of Carbon Wallet users’ submissions. As for other recyclables, the selection is based on reviewing local usage statistics and research.
2.3 Green Dining
Carbon Savings are calculated by comparing the carbon emissions associated with the green action of having a vegetarian meal to the baseline action of having an average non-vegetarian meal. The calculation follows an ingredient composition defined by a study conducted by The University of Hong Kong.
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Carbon emissions of different meals are derived from the summation of carbon emissions of all ingredients according to the composition of the respective meal types. For a vegetarian meal, meat is replaced by other ingredients such as grains, vegetables and fruits.
2.4 Plant Milk
The emission factors of both green action and baseline action are referenced from agribalyse, a French LCA database developed by The French Agency for Ecological Transition (ADEME) for the agriculture and food sector. The average milk content per coffee is determined as 149mL based on the global typical milk portion of 5 common milk coffee (i.e., latte, cappuccino, flat white, mocha & dirty). The emission difference between using dairy milk and plant milk (i.e., soy and oat milk) at this volume is then the carbon savings per coffee.
3. Carbon Savings Equivalencies
On the homepage of the Carbon Wallet App, users’ Carbon Savings are illustrated by linking with different activities (or “equivalencies”) to help them easily understand their contribution to reducing their carbon footprint. The table below presents the carbon emissions associated with these equivalencies.
