GHG Protocol vs ISO 14064, Which One Does Your Company Actually Need?

A student asked me last week, "Ma'am, should we follow GHG Protocol or ISO 14064?" I told her she was asking the wrong question.

It is one of the most common confusions I see in ESG work. Two names keep showing up in every job description, every client RFP, every sustainability report. People treat them like two competing brands, pick one, and hope for the best. They are not competitors at all. One tells you how to count your emissions. The other is how you prove your count can be trusted. Let me explain the way I explain it in class.

What the GHG Protocol actually is

The GHG Protocol Corporate Accounting and Reporting Standard is the world's most widely used framework for building a company-level emissions inventory. It gives us the language everyone now speaks - Scope 1 for your direct emissions, Scope 2 for purchased electricity, steam, heat and cooling, and Scope 3 for everything else in your value chain. It covers the seven greenhouse gases under the Kyoto Protocol, from CO2 and methane to HFCs and SF6.

Think of the GHG Protocol as the accounting method. It tells you what to count, where the boundaries sit, and how to report it honestly. When you hear that CDP questionnaires or science-based targets (SBTi) expect an emissions inventory, the inventory they mean is built the GHG Protocol way. If your company is starting from zero, this is where you start.

What ISO 14064 actually is

ISO 14064 is a family of international standards from the International Organization for Standardization, and it comes in three parts.

ISO 14064-1:2018 - the organisation-level part. It specifies principles and requirements for quantifying and reporting your GHG emissions and removals. The 2018 edition organises emissions into six categories - direct emissions, indirect emissions from imported energy, and four more categories covering the rest of your indirect emissions.

ISO 14064-2:2019 - the project-level part, for quantifying the emission reductions of a specific project, say a solar installation or an efficiency upgrade.

ISO 14064-3:2019 - the verification part, how an independent verifier checks and validates a greenhouse gas statement.

Here is the key thing. ISO 14064 is built so that a third party can audit your numbers. When a verification body finishes its work, it issues a verification statement - an independent professional judgment on whether your inventory follows the stated rules and is fairly presented. That is what banks, large buyers and regulators increasingly ask for.

The difference, in one line each

GHG Protocol answers - "How do I measure and report my emissions properly?"

ISO 14064 answers - "How do I get my emissions measured and reported in a way that survives an audit?"

So which one do you need?

Just starting out, or reporting to CDP, BRSR or similar frameworks? Learn the GHG Protocol first. It is the foundation everything else sits on, and most disclosure frameworks are built on its scope structure.

A client, investor or regulator wants verified numbers? You need ISO 14064-1 for the inventory and ISO 14064-3 for the verification. This is the audit-ready route, and with assurance requirements tightening under regimes like CSRD, more companies are being pushed here every year.

Running a specific reduction project and want the cuts recognised? That is ISO 14064-2 territory.

And here is the part that makes students smile - in real work, you often use both together. Companies build their inventory the GHG Protocol way and then have it verified against ISO 14064. The two are not rivals. They are two halves of one job - count it right, then prove you counted it right.

My honest advice

Do not choose between them like you are picking a phone brand. Learn the GHG Protocol until scopes and boundaries feel like second nature, because you will use that language every single day of your ESG career. Then learn ISO 14064 so that the day a client says "we need this verified", you do not panic - you smile, because you know exactly what happens next.

That is also why our GHG Accounting Bootcamp at Sustainability 101 teaches both together, starting from the GHG Protocol and ISO 14064 basics and going all the way to Scope 1, 2 and 3 calculations and value chain accounting. If you want to build this skill properly, step by step, you can find the bootcamp here - https://www.sustainability101.in/ghg-bootcamp

The question was never GHG Protocol or ISO 14064. The real question is whether you want to just report your numbers - or report them and prove them.