How to Calculate Carbon Emissions from Waste

Step-by-step guide to calculating waste carbon emissions

To develop your carbon emissions calculation, follow these steps:

1. Identify the different types of waste (e.g., paper, food, plastic) within the total waste mass.
2. Find the weight of each type of waste.
3. Use the relevant governmental or authoritative conversion factors to determine the emissions associated with treating and disposing of each type of waste. These factors may vary by country or region, so using the ones applicable to your area is essential.
4. Multiply the weight of each waste type by its corresponding conversion factor to get the emissions for that type.
5. Sum up the emissions from all waste types to get the total carbon emissions from waste.

Understanding waste emissions

Scopes 1, 2 and 3

When calculating carbon emissions, it's essential to identify the primary sources that contribute to greenhouse gas emissions. 

We can categorise them into three primary scopes.

1. Direct emissions (Scope 1) often come from the combustion of fossil fuels in vehicles, heating systems, and cooking appliances. 
2. Indirect emissions (Scope 2) stemming from the production of energy we purchase. A typical example of this is electricity consumption, as energy usage emits greenhouse gases even if they aren't released directly from our homes or vehicles.
3. Other indirect emissions (Scope 3) can be found in the supply chain and goods and services consumed. These include emissions from the extraction, production, transportation, and disposal of products—from food packaging to electronic devices.

Waste emissions are typically measured in CO2e, or "carbon equivalents," and fall under Scope 3 emissions based on the above classification. 

Waste categories

Firstly, it's crucial to differentiate between different types of waste, as their composition affects the emissions they produce. 

Waste can be categorised as organic, plastic, glass, metal, and others. They play a role in the climate emergency in varying ways. 

• For example, organic waste, such as food scraps and yard waste, emits methane when it decomposes in landfills
• while plastic waste generates carbon dioxide when incinerated.

It's also essential to consider the transportation of waste materials, as this process also contributes to carbon emissions. 

Include the following to understand the overall emissions caused by waste management activities. 

• Distance travelled by waste collection vehicles
• Fuel efficiency
• Type of fuel

How disposal methods affect emissions

Landfill

Landfilling involves burying waste material, which decomposes anaerobically, producing greenhouse gases such as methane and carbon dioxide. 

It is important to note that methane has a higher global warming potential than carbon dioxide.

To calculate carbon emissions from landfilling, one must consider the amount of organic waste, the rate of decomposition, and the methane capture rate, often achieved through landfill gas collection systems.

Incineration

Combustion refers to waste incineration, wherein waste materials are burned to convert them into heat, ash, and flue gases, including carbon dioxide. 

Estimating carbon emissions from combustion involves accounting for the waste's carbon content, combustion efficiency, and energy recovery methods.

Organic waste management

Organic waste management comprises processes such as composting and anaerobic digestion. 

Composting, an aerobic process, generates carbon dioxide, while anaerobic digestion produces biogas, a mixture of methane and carbon dioxide. 

To determine carbon emissions in organic waste management, one should evaluate the waste's composition, the efficiency of the decomposition process, and any emissions offset achieved through energy recovery or compost utilisation.

Estimating waste volume or weight

Estimating waste volume or weight can be performed using various methods and tools.

1. Conducting a physical waste audit by collecting and sorting waste to measure its volume and weight. This hands-on method provides accurate data, but it's time-consuming and might not be practical on a larger scale.
2. Using data from waste collection companies. They often track the weight of waste they collect, which can give you a reasonable estimate of waste volume and weight over time.
3. Use standard waste generation factors from governmental or industry sources. These factors estimate waste production based on the type of operation, number of employees, or other factors and can be helpful for initial estimations.
4. Perform a Material Flow Analysis (MFA). This method analyses the flow of materials within a system to estimate waste generation. It may require specific expertise or software tools.
5. Software, like WASTELINQ or Waste Accountant, is designed to track and manage waste, including estimating volumes and weights. Some software packages can also estimate carbon emissions directly based on the type and amount of waste.
6. A more comprehensive method is a Life Cycle Assessment (LCA). An LCA will estimate waste and the associated carbon emissions throughout the life cycle of products or processes.

Applying emission factors

Emission factors are crucial for estimating the amount of greenhouse gases (GHGs) released into the atmosphere from various sources, including waste. 

They are expressed as the amount of emissions produced per unit of activity, such as the amount of carbon dioxide emitted per tonne of waste disposed. 

Here's a detailed breakdown of how emission factors are used in measuring waste emissions:

• Different types of waste (e.g., organic waste, plastic, metal, glass) have different emission factors due to their varying composition and disposal methods.
• The amount of each waste type must be measured to determine the total emissions from waste disposal.
• The emission factors, which government agencies or international organisations usually provide, are then applied to each waste type. For example, if the emission factor for organic waste is 0.5 tonnes of CO2 per tonne of waste, and you have 10 tonnes of organic waste, the emissions would be 5 tonnes of CO2.
• The method of waste disposal (e.g., landfill, incineration, recycling) also impacts the emission factor. For instance, methane is generated when organic waste decomposes anaerobically in a landfill, while carbon dioxide is primarily emitted during incineration.
• The emissions from each waste type are summed to get the total emissions from waste disposal.
• Emission factors may vary from one region to another based on local regulations, technologies, and practices. Therefore, it's crucial to use region-specific emission factors for accurate measurements.
• As technologies and waste management practices evolve, emission factors may change. Continuous monitoring and updating of these factors are necessary for accurate emissions estimation.

This process helps individuals, businesses, and policymakers to understand, monitor, and manage the emissions generated from waste, contributing to broader emissions reduction goals and climate change mitigation efforts.

Emissions factors vary by location

As factors vary, your calculation methods will depend on your national recommendations. 

Here are links to a few documents on national emissions factors.

• UK Government's Conversion Factors for Company Reporting provides the conversion factors used to report greenhouse gas emissions.
• EPA's Emission Factors Hub is a compilation of emissions factors used in the USA.
• Emission Factors and Reference Values for Canada.ca.
• National Greenhouse Accounts Factors in Australia.

Carbon calculators & tools

Thankfully, several tools are available to make carbon footprint calculations.

One such tool is the Environmental Benefits Calculator from the US Environmental Protection Agency (EPA). This helpful calculator converts reduced solid waste into greenhouse gas equivalencies, which is useful for understanding reduced waste production's environmental impact.

The Waste Reduction Model (WARM) estimates potential greenhouse gas emissions reductions, energy savings, and economic impacts from different waste management practices.

The EPA also provide a Simplified GHG Emissions Calculator, an excellent choice. Designed for small businesses and low-emitter organisations, it provides an easy-to-use platform for estimating and inventorying annual greenhouse gas emissions.

The bottom line

To calculate carbon emissions from waste, first identify and weigh the different types of waste, such as paper, food, and plastic. 

Then, apply the respective governmental or authoritative conversion factors relevant to your region to determine the emissions tied to the treatment and disposal of each waste type. 

Finally, multiply the weight of each waste type by its conversion factor and sum these values to obtain the total carbon emissions from waste.

Achieving net-zero emissions requires a collective effort, and companies and individuals must proactively reduce their carbon footprint.