The Zero Carbon bill aims to tackle climate change by setting a net-zero target for almost all greenhouse gas emissions by 2050.
Methane from animals will carry more lax requirements, which allows some leeway to farmers who bring in much of the country’s foreign income.
Prime minister Jacinda Ardern said she sometimes despairs at the pace at which other countries are making changes to fight global warming and vowed that New Zealand would be a leader.
“We’re here because our world is warming. Undeniably it is warming,” she said. “And so therefore the question for all of us is what side of history will we choose to sit on.”
Net zero, the new goal for most greenhouse gases, is where the amount of emissions produced is equivalent to the amount absorbed by the atmosphere.
Methane emissions would be reduced by 10 per cent by 2030 and by between about a quarter and a half by 2050 under the bill.
The New Zealand government has also promised to plant a billion trees over 10 years and ensure the electricity grid runs entirely from renewable energy by 2035.
The bill establishes a Climate Change Commission which will advise the government on how to reach its targets.
The law was spearheaded by the liberal government but in the end was supported by the main conservative opposition party, which nevertheless promised changes if it wins the next election.
Climate change minister James Shaw said the new law would help ensure a safer planet for everybody’s children and grandchildren.
“We’ve led the world before in nuclear disarmament and in votes for women, now we are leading again,” he said.
Agriculture is key to the economy of New Zealand, which is home to just under five million people but more than 10 million cows and 28 million sheep.
Those animals emit methane, resulting in an unusual greenhouse gas emission profile for the country. Almost half of total emissions come from agriculture.
The bill says the lower targets for methane reduction reflect that it stays in the atmosphere for a much shorter time than carbon dioxide, although scientists point out that methane is far more potent while there.
It also aims to fulfil New Zealand’s obligations under the landmark 2015 Paris climate agreement to keep in check rising global temperatures.
The UK passed a net-zero emissions law this June, as pledged by Theresa May before she left office.
However, the government has been criticised for not doing enough to fulfil its promise, with MPs warning the target will be missed with “dire consequences” without new climate policies.
In September, environment experts said money pledged to help the UK reach its net-zero goal is 0.1 per cent of what is needed.
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