The vast majority of New Zealand's methane comes from agriculture - 89 per cent - and just under 10 per cent from waste, while in many other countries the bulk comes from fossil fuel industries.
In Australia, which has not signed up to the global pledge, research has found methane leaking from coal mines equals about a quarter of its total CO2 emissions.
These fossil fuel emissions are regarded as easier to plug and reduce than those from agriculture, and hence the global agreement accounts for countries to make different domestic pledges based on their emissions profiles.
The majority of the cuts are expected to come from such methane leaks from fossil fuel industries.
The commitment was led by the United States and European Union, and involved 15 major emitters including Brazil, Nigeria and Canada.
China, Russia and India have not signed the pledge.
The head of the Greenpeace delegation, Juan Pablo Osornio, said the pledge needed to be the "start and not the finish of the ambition on cutting this potent greenhouse gas".
"The IPCC says we need to cut all emissions in half by 2030 if we hope to keep global temperature rises within 1.5C. If we drastically slash fossil fuels we'd cut methane and carbon emissions at the same time, and have a much better chance of meeting that goal.
"And by not including meat reduction or pledges to change people's diets in this commitment, governments are giving a free pass to Big Agriculture."
As a result, he said, "this announcement dodges what's needed".
Earlier, New Zealand was one of 114 leaders to commit to halt and reverse forest loss and land degradation by 2030 under the Glasgow Leaders' Declaration on Forest and Land Use.
The pledge was backed by US$12bn in public and US$7.2bn in private funding.
Together, they support 85 per cent of the world's forests, an area of over 13 million square miles which absorbs around one third of global CO2 released from burning fossil fuels each year.
More to come.
