How big is this carbon footprint, and what would offset it?

The working figure used throughout this calculator is 22 kg a year, which is a common planning assumption for a young tree in active growth. Mature trees absorb more, seedlings much less, and a tree only counts as an offset if it survives for decades — which is exactly why offset quality is so contested.

They make different choices: whether to count only CO₂ or all greenhouse gases, whether to apply a radiative-forcing multiplier for contrails, what load factor and aircraft type to assume, and how to split emissions between cabin classes and between passengers and freight. Each of those is defensible, and together they can move the result by a factor of three.

Because the emissions are divided by the number of passengers the aircraft carries, and a business seat occupies roughly three times the floor area of an economy seat. Fly first class and you are responsible for a proportionally larger slice of the same fuel burn. Nothing about the seat itself emits more.

Much less than headlines once suggested. Early estimates were revised down dramatically once researchers separated network transmission — which is remarkably efficient per gigabyte — from the power drawn by the screen you are watching on. The device is usually the dominant term, so watching on a phone rather than a 65-inch TV changes far more than the resolution setting does.

It roughly halves the data-related portion, and the relative comparison is the reliable part of any streaming estimate. Whether that matters depends on your context: for someone streaming several hours a day on a large screen it is a measurable annual saving, and for occasional viewing it is noise next to a single car trip.

Their diet does, because meat production is carbon-intensive. But the estimates published for pets vary by an order of magnitude, largely over one question: whether pet food made from slaughter by-products should carry a footprint at all, given that the material would otherwise be waste. Treat any pet figure, including this one, as an upper-bound style estimate.

Where you hold it. Guest travel typically dwarfs catering, flowers, venue power and everything else combined, so a venue most guests can drive to beats every other sustainability decision on the list. After that, the catering menu — specifically how much beef and lamb is on it — is the next largest term.

Offsets are a supplement, never a substitute, and their quality varies enormously. The hard questions are additionality — would the reduction have happened anyway — and permanence, since a forest that burns in fifteen years releases everything it stored. If you buy them, prefer verified removal projects over avoided-emissions credits, and treat the purchase as additional to reducing, not as permission.

Commonly quoted as 450 years and upward, but the framing is misleading: most plastics do not biodegrade, they photodegrade into ever-smaller fragments. The bottle stops being a bottle long before the polymer stops existing, and the microplastics that result are their own environmental problem.

No. Modern sanitary landfills are engineered to exclude air and water, which is what decomposition needs. Newspapers have been excavated still legible after decades. These figures describe an open environment — compost heap, roadside, ocean — not a sealed landfill cell.

For most people in high-income countries it is, in rough order: flying less, driving less or switching to an electric vehicle on a clean grid, home heating, and diet — particularly beef and lamb. Recycling and unplugging chargers matter, but they are one to two orders of magnitude smaller, and treating them as equivalent is how people end up feeling busy without moving the number.