Scope 3 & GHG Emissions Calculator

Scope 1 covers emissions from sources you own or control directly, such as fuel burned in company vehicles, boilers or furnaces. Scope 2 covers the emissions produced elsewhere to generate the electricity, steam, heating or cooling you purchase. Scope 3 covers everything else in your value chain, both upstream and downstream, from the goods you buy through to how customers use and eventually dispose of what you sell.

No. The GHG Protocol asks you to assess all fifteen for relevance, then report the ones that are material to your organisation. A software company has almost no emissions from processing of sold products, and a retailer may have none from franchises. What matters is that you screen each category, report the relevant ones, and disclose which you excluded along with the reason. Silently omitting a category is the problem, not excluding one with a stated justification.

Because it captures the whole value chain rather than just your own premises. For most organisations outside heavy industry, the emissions from purchased goods and services alone exceed everything burned on site. That is also why Scope 3 is where an inventory has the most influence and the most uncertainty at the same time.

Spend-based estimation multiplies how much money you spent in a category by an emission factor per unit of currency. It is quick and works from accounting data you already have, but it cannot tell an efficient supplier from an inefficient one, and inflation distorts it over time. Activity-based data uses physical quantities such as kilograms of steel, kilowatt-hours or passenger-kilometres, and is considerably more accurate. Most organisations start spend-based and replace the material categories with activity data as they mature.

Location-based uses the average emissions intensity of the grid you draw power from. Market-based reflects the electricity you have contractually purchased, including renewable energy certificates or a green tariff. The two can differ substantially, which is why the GHG Protocol asks for both to be disclosed rather than letting you pick the flattering one.

Across different organisations, yes, and that is intentional. Your supplier's Scope 1 is part of your Scope 3, so the same tonne appears in two separate inventories. Double counting is only a problem within a single inventory, which is why the fifteen categories are defined to avoid overlapping each other.

Treat it as a screening exercise. It will show you which categories are material and roughly how large your footprint is, which is exactly what you need before committing to a full inventory. A figure you intend to publish, submit to CDP, or use for a science-based target needs primary supplier data, documented methodology and usually third-party verification.