What are Greenhouse gas emissions?
Greenhouse gases (GHGs) are a group of gases that trap heat when they reach the atmosphere, and cause an increase in the Earth's temperature.
There is a natural level of GHGs in the atmosphere, however as human activity has increased over the past 300 years, the amount of GHGs has increased. This is causing changes such as an increase in the Earth's temperature, changing weather patterns (such as storms, droughts, rainfall), and changing natural features such as glaciers and ice caps.
GHGs reach the atmosphere from human activities such as the burning of fossil fuels e.g., oil and gas, transportation, manufacturing, and farming.
How do we calculate greenhouse gas emissions?
The most widespread GHG is carbon dioxide (CO2), and this is used as a standard measure for GHG emissions by converting all other GHGs to the equivalent mass of CO2. This unit is referred to as a tonne of carbon dioxide equivalent, tCO2e.
The GHG emissions arising from human activities can be calculated by using conversion factors, known as emission factors. These are expressed in terms of kgCO2e per unit of activity. The denominator for the emission factor will depend on the activity type.
This can be carried out for many industrial activities such as burning of natural gas, disposal of waste etc. A company can perform this for all activities at its site that contribute to the emission of GHGs to determine their total emissions. This is often known as a carbon footprint.
What are Scope 1, 2 and 3 emissions?
A carbon footprint consists of three scopes of emissions; Scopes 1, 2, and 3 as defined by the GHG protocol which is the world’s most widely used GHG accounting standard. These scopes include different emissions sources and are a way of looking at the level of influence that a company has over different aspects of its emissions.
Scope 1
Scope 1 covers emissions that occur directly from assets owned and/ or operated by the company such as burning natural gas in boilers, running refrigeration units, and using petrol in company vehicles.
Scope 1 emissions are those over which the company has the most control and is able to make direct changes to impact.
Scope 2
Scope 2 covers emissions from the generation of purchased energy outside the boundaries of the site, that is then consumed by the site.
The purchased energy can be electricity, heat, steam, or cooling purchased from a third party.
Sites can make efforts to reduce emissions in this category through energy efficiency initiatives such as switching to low energy lighting and choosing to purchase from low-carbon energy providers.
Scope 3
Scope 3 emissions often represent the largest part of the carbon footprint.
These emissions are a consequence of a company's activities but occur from sources it does not own or control.
For example, employee business travel and commuting, and supply chain activities.
Scope 3 emissions are broken down into 15 categories but not all 15 categories will apply to all companies. Where they apply to a company, they may not be applicable to all sites. Some of the most common are:
Business travel - calculated from the distance and modes of transport used by company staff on work related trips.
Purchased goods and services - calculated from the emissions associated with the production of raw materials or services (e.g., pest control) used by a company as part of their activity.
Waste generated in operations - calculated from the amount of waste produced by a company at its sites and the chosen methods of treatment.
Employee commuting - calculated from the distance and modes of transport used by company staff travelling to and from work.
What is Net Zero?
Net zero is considered an important goal in the fight against climate change, as it is seen as a way to limit the increase in global temperature to within 1.5°C above pre-industrial levels, the target set by the Paris Agreement on climate change. Many countries, organisations, and individuals around the world have pledged to reach net zero emissions by a specific date.
In 2019, the UK government set a target to reduce greenhouse gas emissions by 100% from 1990 levels by 2050, this is commonly referred to as net zero. More information can be found here.