New Zealand has announced its biggest emissions-cutting project in history, switching from coal to renewable electricity at the country’s major steelworks in a move the government says is equivalent to taking 300,000 cars off the road.

The government will spend $140 million to halve the coal used at the Glenbrook steelworks to recycle scrap steel, replacing the generating power with an electric furnace. The facility will contribute $160 million to the project’s cost.

Currently, the steel company accounts for 2% of New Zealand’s total emissions, through intensive burning of coal to melt down iron-rich sand into steel products. The new project will install a $300 million electric arc furnace to melt down scrap steel instead. That electricity will be provided by renewable energy via New Zealand’s national grid, which is primarily powered by wind, hydro and geothermal energy.

Premier Chris Hipkins said the project “dwarfs anything we’ve done so far”.

“This size of this project shows how serious the Government is about reducing New Zealand’s emissions as quickly as possible,” he said. “That alone will eliminate 1% of the country’s total annual emissions.”

The government says the plan will reduce New Zealand’s emissions by 800,000 tonnes annually. That’s the equivalent of taking the entire fleet of cars in Christchurch, one of New Zealand’s largest cities, off the road.

“To understand the scale of this project, it cuts more emissions on its own than all of the other 66 (government-funded emissions reduction) projects that we’ve approved so far,” Energy and Resources Minister Megan Woods said. The electric oven should be operational in 2026-2027.

Climate change expert Prof James Renwick, of Victoria University, told the Guardian the project was “very significant” and “big news” for the country’s emissions targets. “It will be the largest single reduction in national emissions when it comes to gaming,” he said. Still, Renwick added, there was “more to do.”

“1% of national emissions is good, but we need to reduce by 100%,” he said. “We need to do a lot more work.”

The plan “will put New Zealand in a much better position to reach its climate target of net zero carbon dioxide by 2050,” Climate Minister James Shaw said.

The plan marks a significant step in New Zealand actually reducing its greenhouse gas emissions – as opposed to buying tree-planting offsets to reach net zero.

In April, The Climate Commission warned that the country’s heavy reliance on planting trees to offset carbon pollution threatened to torpedo its ambitious plans to reach net zero emissions by 2050. Achieving a net reduction in emissions primarily through planting trees is unsustainable in the long term, experts have warned, as forests can be destroyed by fire or extreme weather and do not store carbon forever.

While New Zealand’s total contribution to global emissions is small, its gross per capita emissions are high. According to 2018 data, New Zealanders produce greenhouse gases equivalent to the warming effect of 16.9 tonnes of carbon dioxide – more than twice as much per capita as in the UK. The country has also been among the world’s worst performing emissions increases.

“We cannot plant our way out of the problem of climate change,” Renwick said. “We need to focus on gross emissions reductions rather than net.”

Shaw said the agreement was expected to contribute 5.3% of emissions reductions needed under New Zealand’s second emissions budget, covering the period 2026-2030, and 3.4% within the third emissions budget, 2031-2035.