"It's a constant concern for us, but we're required to do a job, and that requires air travel. My carbon debt will never be repaid, and I certainly can't repay it with money.
"I have to repay it in my time and commitment to the green kaupapa."
The Parliamentary Service uses expense forms to tell the MPs how many kilometres they've travelled on ground or in the air.
The MPs then use carbon measuring schemes - such as CarboNZero - to work out their carbon footprints and make arrangements through various schemes to pay them off.
This usually involves paying $25 a tonne of carbon dioxide to companies that have made an emissions reduction.
CarboNZero, which is owned by Landcare, estimated that the trip by Ms Turei and fellow MP Kennedy Graham to Senegal caused around 16.22 tonnes of emissions, which meant a total bill of $425.
CarboNZero said international flights were not significantly more carbon-heavy than domestic travel, because a huge proportion of the emissions occurred during takeoff and landing.
The company calculated air travel emissions by taking into account the number of passengers, the distance travelled, and whether the travel was domestic or long-haul.
Green Party communications director Andrew Campbell said it was not mandatory for Green MPs to pay a carbon bill, but it was a "no-brainer" for them to sign up.
Most MPs were paid between $140,000 and $180,000 a year, so a carbon bill of $1500 was around 1 per cent of their income.
The Greens have approached Parliamentary Services to encourage an offsetting scheme for all MPs, but it hasn't been adopted. The National and Labour whips didn't know whether their MPs offset their emissions.
Bus trips and other public transport were not included in the MPs' carbon footprints, partly because the amount was small, but also because it was harder to measure.
