If you have ever opened the GHG Protocol and thought, “This all makes sense in theory, but where do I actually get the numbers?” you are not alone.
When people are new to greenhouse gas accounting, emission factors are often the most confusing part of the process. There are hundreds of databases, many overlapping, some global, some regional, some highly specific, and others frustratingly high level. Choosing the wrong source can quietly undermine data quality and credibility. Choosing the right one can save weeks of work and make future audits far easier.
This article is a comprehensive, practitioner focused guide to the most widely used publicly available GHG emission factor databases used for corporate GHG inventories. It is organized by Scope 1, Scope 2, and Scope 3, with additional breakdowns by emission category so you can quickly identify what to use and when.
This is the guide I always wish I had when I was starting out.
Before diving into specific databases, it is important to understand one foundational concept.
Not all emission factors are equal.
In general, emission factors follow a quality hierarchy:
Public databases typically fall into categories two through four. They are essential, but they are also approximations. Understanding their limitations and documenting why they were chosen is part of good carbon accounting.
If you are just getting started, one of the fastest ways to understand how emission factors actually get applied in practice is to run a simple calculation yourself. North Star offers a free carbon calculator at https://northstarcarbon.com/free-carbon-calculator that shows how real Scope 1, 2, and 3 activity data connects to specific emission factor sources. It is a helpful bridge between theory and practice.
Scope 1 emissions include direct emissions from sources a company owns or controls. These are often the most straightforward to calculate, assuming you have solid activity data.
Common Scope 1 sources include:
For US based companies, this is the most commonly used and widely accepted source for Scope 1 emission factors.
It includes:
This database is frequently updated and is commonly accepted by auditors and third party verifiers.
Often referred to as DEFRA factors, this dataset is one of the most comprehensive publicly available resources globally.
It is especially useful when:
The IPCC provides default emission factors and methodological guidance, particularly useful where national data is unavailable. These are typically higher level but methodologically robust.
Scope 2 emissions are conceptually simple but methodologically nuanced. Emission factor selection depends on whether you are reporting location based, market based, or both.
eGRID is the backbone of Scope 2 location based reporting in the United States.
It provides:
If your electricity consumption is in the US, eGRID is almost always the correct starting point.
The IEA publishes country level electricity emission factors used widely for international reporting.
These are best used when:
While not a database itself, this guidance defines how emission factors should be applied for market based reporting, including renewable energy instruments and residual mix factors. Many Scope 2 errors stem from misapplication of this guidance rather than the wrong emission factor.
Scope 3 is where emission factor databases become both essential and overwhelming. There are 15 Scope 3 categories, and no single database covers them all well.
Scope 3 is also where teams often feel stuck. Not because the data does not exist, but because it is hard to know which emission factor source is appropriate for each category. Tools like North Star’s free carbon calculator at https://northstarcarbon.com/free-carbon-calculator can help teams sanity check early assumptions, especially when starting with spend based or activity based data before moving toward supplier specific emissions.
Below is a practical breakdown of the most common Scope 3 categories and the databases typically used.
This is often the largest Scope 3 category and the most challenging to quantify accurately.
These spend based emission factors link economic activity to emissions by sector. They are commonly used when only financial spend data is available and are often the starting point for first year inventories.
EXIOBASE is a publicly available multi regional input output database that provides greater geographic resolution for global supply chains.
Ecoinvent provides detailed activity based emission factors for materials and products. While not always fully free, it is widely used through LCA tools and academic access.
These categories typically rely on a mix of combustion, transportation, and waste emission factors.
DEFRA is one of the most versatile Scope 3 resources available and is commonly used for:
The Waste Reduction Model is widely used for Scope 3 Category 5 and includes landfill, recycling, composting, and waste to energy pathways.
These categories often rely on assumptions about customer behavior and product lifecycles.
Both EPA and DEFRA databases provide emission factors for:
In many cases, transparent assumptions matter more than marginal differences between emission factors.
Traditional corporate databases often fall short for land based emissions.
This guidance introduces methods for land use change, soil carbon, and biogenic carbon accounting.
The IPCC remains the foundational source for agricultural and land sector emissions globally.
One of the biggest challenges practitioners face is not finding emission factors. It is managing them over time.
Good carbon accounting requires:
North Star Carbon and Impact is designed to store emission factors directly alongside activity data and calculations so teams can clearly show where every number came from and why it was used.
If you want a practical way to test these databases, understand how emission factors roll up into totals, and build confidence before committing to a full inventory, you can start with North Star’s free carbon calculator at https://northstarcarbon.com/free-carbon-calculator.
Emission factors are the backbone of every GHG inventory and one of the easiest places to make mistakes that quietly undermine data quality.
You do not need the perfect emission factor in year one. You do need a defensible one, applied consistently, and clearly documented.
Start with reputable public databases. Understand their strengths and limitations. Improve over time as better data becomes available.
If this guide saves you even a few hours of searching, confusion, or second guessing, it has done its job.
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