Introduction to climate calculation methodology for Ducky API

See how climate footprint calculations are made in Ducky's API, what research and methodology is used.

Our focus is on footprint, not just direct emissions, so all of our multipliers are based on life cycle assessment where possible and include upstream emissions. This means that e.g. the footprint of driving a car includes not only the tailpipe emissions from using gasoline, but also a component of the emissions caused by manufacturing the car and, eventually, recycling it. Through the endpoints, the term “multiplier” is used to describe a number that we multiply with some other quantity to get footprint in kg CO2e. 

General notes on modeling choices

Choice of input-output database

An input-output database is a table of how money moves through different sectors of the economy, thereby modeling how different sectors of the economy depend on each other. This can in turn be tied to environmental indicators like greenhouse gas emissions, allowing us to trace their flow through the economy. We use this method - environmentally extended input-output assessment - to determine the overall climate footprint of a household from the top down perspective, which again can be used to confirm that the bottom-up calculations using life cycle assessment factors are yielding correct results. One modeling choice we have to make is which database to use. Different databases collect economic and environmental data with different resolutions (in different sectors of the economy) and with different frequency (yearly or as infrequently as every 5 years).

EXIOBASE is the most detailed MRIO database available, but has been found to be more accurate for large economies. Furthermore, the data is only updated every 5 years compared to yearly for the European Eurostat database. Currently, EXIOBASE is used for the UK datasource, while the Norway datasource uses data from Eurostat in a custom model made by Asplan Viak. 

The rebound effect 

In conservation and energy economics, the rebound effect is the reduction in expected gains from new technologies that increase the efficiency of resource use, because of behavioural or other systemic responses. In environmental footprinting, the rebound effect is when measures taken to reduce environmental impact backfire or have unintended consequences (see for example Hertwich (2008)). 

The rebound effect is easiest understand using an example; say that a person installsinstals a heat pump in their house to reduce their energy use. The reduced energy use lowers their electricity bill, so they have saved money. Two types of rebound are possible in this case. 

In the case of direct rebound, the person decides that, since their electricity bill is so much cheaper, they can afford to turn up the thermostat and keep the house warmer. Therefore they continue to use the same amount of electricity as before, despite installing this efficient appliance. 

In the case of indirect rebound, the person spends the money they saved on electricity on something else. If they choose, for instance, to save for plane tickets, the footprint of that spending may actually be larger than if it was spent on electricity.

Both of these effects are a consequence of the unpredictability of human behaviour and part of the challenge of footprint modelling. Ducky’s calculations encompass many behavioural changes that save money as well as reducing climate footprint. Therefore, we have implemented a simple model for the rebound effect, where we assume a degree of environmentally friendly respending of savings.

Generally, money spent on services is less carbon intensive than money spent on physical goods. Statistically, most people save very little money over time; most is spent at some point. Where a behavioural change saves money, we redistribute this money in services categories, instead of assuming that the saved money is never spent. This means that depending on the individual’s choices, the savings that we calculate could be larger or smaller than estimated. If you give away the money you saved to charity, your footprint savings would be larger than our estimate. If you spend your savings on a plane ticket, your savings would be smaller than our estimate.

Currently, we only account for rebound effects in the Goods & services category of our calculations but we plan to integrate this respending pattern into our other categories over time.

Overview per endpoint

Click links below to read more about methodology per API endpoint: