Introduction to Discover

Each page describes an individual category - a collection of items representing energy consuming or other activities which share a common way to calculate their associated greenhouse gas emissions. categories contain, for example, different types of car or train transport, types of fuel or country-specific grid electricity, electrical appliances, and agricultural or industrial processes.

Since Discover provides all of the data and models necessary for calculating emissions in each of these cases (and more!), you only need to choose the data item of interest (this might represent a car, a building, a flight or an electrical appliance), then use this as the blueprint for creating a profile item in which you can set profile item values to store usage information (e.g. the number of km travelled, or litres of fuel used).

So, in summary, by selecting a category, making drill down choices and setting profile item values, you can use Discover to store and process almost any form of activity that is associated with greenhouse gas emission. Discover describes in detail all of the categories available within the platform, and lists all drill down choices and profile item values which can or must be specified.

Important Discover concepts

Algorithms

Algorithms describe how data items and profile items in a category are used together to produce an emissions calculation.

Most algorithms involve multiplying a user supplied value, e.g. km travelled, by a data item value, e.g. kgCO₂ per km. However, some algorithms are more complex and can reference other data items.

Categories

A category in Discover is a collection of items representing energy consuming or other activities which share a common way to calculate their associated greenhouse gas emissions. categories contain, for example, different types of car or train transport, types of fuel or country-specific grid electricity, electrical appliances, and agricultural or industrial processes.

Categories are organised in a tree-like structure based around the primary parent categories business, home, embodied, metadata, planet and transport. When interacting with Discover, the full path is used to specify the use of a particular category (e.g. /business/energy/stationaryCombustion).

Where similar data exists, perhaps from different sources or representative of different geographic contexts, alternative categories are available for the same type of emissions activity.

Every category within Discover is individually documented. This documentation describes the functionality of each category, the source of any data or calculating methodologies, relationships with other categories, and provides instructions for how to use the category to store relevant data and make emissions calculations.

Data items

Data items are the fundamental unit of data organisation and emissions calculations in Discover. Data items are organised into categories and represent distinct types of activity, such as consumption of a particular type of fuel, a short-haul flight, or the use of an electrical appliance.

Data items contain two types of information: drill down choices are used for uniquely specifying a particular item, and data item values are used to store emissions factors and other information relevant to that item.

When developing an application that uses Discover, you will usually only need to work with profile items. However, it is useful to look at data items if you want to understand what the data means, what assumptions lie behind it and what you need to ask your user.

Drill down

Drill down choices represent unique identifiers for individual data items. Drill down choices are used together with category paths to specify the individual data items with which users wish to work. The process of making such a choice is termed a 'drill down'.

Emissions factor

Emissions factors are conversion factors used to convert specific quantities of some activity into associated greenhouse gas emissions. Emissions factors may be formulated in a number of ways depending on the requirements of the calculation, and may, for example, calculate emissions on the basis of an amount of fuel burned, a distance travelled, or a quantity of manufactured goods processed. Each emissions factor incorporates specific information regarding the activity it describes, such as fuel properties (e.g. carbon contents), vehicle fuel efficiency, or occupancy of passenger vehicles (e.g. buses, planes, trains)

Item definition

Every category contains an item definition which defines all the data and profile item values and algorithm required to make an emissions calculation for the associated activity. An item definition comprises a list of item value definitions which define the nature and role of each item value.

Each page corresponds to a single category, and provides a breakdown of the associated item definition in tabular form.

Item value definition

An item value definition is a description of the name, nature and role of individual components within an item definition. For example, the item value definition defines whether a particular component is a drill down choice, a data item value or a profile item value, and specifies the name, units and default values with which it is to be associated.

Profile items

A profile item is always based on a particular data item. A profile item contains information on a particular aspect of usage or ownership which can be stored and used to calculate the associated greenhouse gas emissions. Once a profile item is created in this way, you can retrieve the kg CO₂ (or CO₂e) value at any time in the future. You can also retrieve the choices and values stored in the profile item - which represent a record of consumption - so you can display this information to your user when they return to the page at some time in the future.

Profile item values

Profile item values are user-supplied consumption on usage or ownership which is stored in Discover and used for emissions calculations. For example, a profile item value may represent the distance driven in in a single journey, or the electricity used in one year.

Discover allows you to track the history of a profile item. So, for example, one month a user might tell you they drove 1000 km, then after being alarmed/ashamed/embarrassed at that month's profile, they might take the bus more next month and so tell you that they only drove 300 km. The profile history lets you display this information back to the user, along with consequent reductions (or increases) in carbon dioxide emission.

Units

Discover allows the user to use any dimensionally compatible units when specifying quantities such as profile item values. For example, when specifying a volume, users may choose between litres, cubic metres, US gallons, etc., or switch between metres, kilometres or miles if describing a distance. Discover performs all necessary unit conversions in order to return the correct value for emissions of greenhouse gases.