So you want to offset your emissions? Read this first

A quick guide to how offsetting works best

"Offsetting" is when an individual or organization compensates for their greenhouse gas emissions by supporting certified projects that reduce global carbon dioxide levels. Imso Gabriel, Unsplash
26 July 2022
26 July 2022

You’ve likely seen the check-box upon booking a flight or train trip. Offset my emissions? It seems so simple; a no-brainer for any eco-minded citizen with a couple of extra bucks to spare.

But is it really that easy?

Offsetting projects and opportunities are proliferating around the globe, and many organizations and communities speak highly of their role in providing income streams to support eco-friendly actions such as planting trees and leaving existing forests standing. Meanwhile, the likes of Greta Thunberg and Greenpeace are criticizing the entire industry as “greenwashing” and “a scam”.

So, should you buy them?

“Yes, but selectively,” says science writer Brian Palmer in a recent explainer on the topic for the Natural Resources Defense Council. There’s a wide range in ‘quality’ of offsets – that is, their actual emission reduction potential – and if you choose to offset, it’s important to keep several principles front-of-mind. We spoke to Tani Colbert-Sangree, a senior program officer at the Greenhouse Gas Management Institute (GHGMI), to find out more.

1. Avoid before offsetting

It might seem like the least-fun option, but avoiding emissions in the first place is a much better option than paying someone else to avoid or sequester for you. Can that meeting be an email? Could you attend the conference virtually? Do you really need a tropical holiday, or will a trip to the local hot springs hit the spot?

Aviation accounts for about 2.5 percent of all global carbon dioxide emissions. Patrick Tomasso, Unsplash
Aviation accounts for about 2.5 percent of all global carbon dioxide emissions. Patrick Tomasso, Unsplash

2. Choose quality

To get a sense of the ‘environmental integrity’ of a given emission reduction project – that is, whether or not it’s actually having an impact on the levels of greenhouse gas emissions that are in the atmosphere, keep your eyes on the following five principles, which are outlined and explored in-depth in the GHGMI and Stockholm Environment Institute (SEI)’s Carbon Offset Guide.


‘Additionality’ is a word you’ll hear a lot in the offset world. It’s the notion that a particular greenhouse gas reduction would not have occurred if there was no market for offset credits. If those reductions would have happened anyway, then purchasing credits for them won’t actually offset your own emissions.

For example, would a forest be felled if local communities weren’t getting paid via the carbon market to keep it intact? If no, then there’s no additionality, and the offset isn’t worth your while.

While it’s critically important, determining additionality is something of a gray area, as there are a lot of aspects that are difficult to foresee, and things like policy change will impact what ‘happens anyway’ – such as if a government outlaws the felling of native forest in a particular region.


The amount of emission reduction prompted by a particular project can be overestimated, particularly when baseline and actual emissions are not calculated and monitored sufficiently carefully. “So we need to consider, are the quantification methodologies in line with the best scientific knowledge that we have at our disposal, and do they conservatively estimate emissions?” says Colbert-Sangree.

‘Leakage’, where a project prompts increases in emissions outside of its boundaries – e.g. logging is avoided in the project site but instead takes place elsewhere to address livelihood needs – must be taken into account as part of this monitoring process. Generally speaking, complex land-based projects like nature-based solutions are challenging and expensive to accurately evaluate and monitor. For more contained projects like industrial gas destruction, it’s relatively simple and cheap to get those figures.

Attention given to livelihood benefits is a crucial part of offsetting responsibly. Vitor Monthay, Unsplash
Attention given to livelihood benefits is a crucial part of offsetting responsibly. Vitor Monthay, Unsplash


Permanence refers to whether or not the emissions are avoided on a long-term basis (which most programs define as at least a century). Some projects, such as reforestation, run higher risks than others of releasing the ‘avoided’ emissions into the atmosphere at a later date: “if fire, disease or pests come along, a forest could be destroyed, and it would not be the fault of the project proponent,” says Colbert-Sangree. “But those ways of storing carbon are just inherently impermanent.”

Many programs address this challenge by using a kind of insurance mechanism or buffer pool, which receives around 5 to 15 percent of the credits from each project and then goes to support those that suffer such a loss.

-Exclusive claim to greenhouse gas reductions

This principle speaks to avoiding ‘double counting’, where more than one entity takes credit for a particular suite of greenhouse reductions – for example, if both a producer and a consumer of biofuel claim reductions from using the same units of fuel. This is less of an issue than it has been historically, because greenhouse gas registries, which track offset projects and issue credits, are publicly accessible and, “generally speaking, do a really good job of ensuring that credits are used once and only once,” says Colbert-Sangree. 

-Avoiding social and environmental harms

Many offsetting projects benefit the communities and ecosystems in which they take place. But offsetting projects can also cause social and/or environmental damage: for instance, the Alto Maipo hydropower scheme near Santiago, Chile, is registered to sell carbon credits, despite the deleterious impacts on local communities and ecosystems from its diversion of a critical water source. “Even if a project ticks all the other boxes, if it then also damages an ecosystem and displaces a community, that would be a really low-quality, low–environmental integrity project because of that social and environmental harm,” says Colbert-Sangree.

Take some time to consider your own values.“Very few projects are going to be perfect on all of those criteria, so it’s also about what’s most important to you as a buyer,” says Colbert-Sangree. “It’s going to be a subjective decision – and that’s the real challenge that buyers face when purchasing carbon credits.”

If you’re an individual who’s just about to jump on a domestic flight, however, weighing up those values and going deep into the fine print of every project might be beyond your capacity. Instead, lean on the work of others. The assessment tool offered by the Carbon Credit Quality Initiative might be helpful with this task.

3. DIY carbon sequestration

Back home? Take a look at your lifestyle and see where you could be stashing carbon. Start a compost – according to modeling by Project Drawdown, worldwide adoption of composting could reduce emissions by 2.3 billion tons over the next 30 years. Turn your backyard into a carbon sink. Choose wood over concrete and plastic for building and furniture. The options are abundant. Where will you begin?

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