Energy giant Woodside will forge ahead on the Scarborough gas project off Western Australia’s northwest coast after it gave the project final approval. The $16.2bn Scarborough project is a joint venture between Woodside and BHP and the announcement posted to the ASX on Monday afternoon also confirms the two companies have agreed to a $40b merger of their petroleum businesses, creating one of the world’s biggest fossil fuel companies. The oil and gas field will be one of the biggest fossil fuel projects in Australia in the last decade and has been labelled a “disaster” by environmentalists. The field lies 375km off the Western Australian coast and will consist of eight wells drilled in the initial phase, with 30 to be drilled over its lifetime. A 430km pipeline will link it to the mainland, and the Pluto LNG processing facility near Karratha will be expanded to handle the increased capacity as production is slated to begin in 2026. Woodside chief executive, Meg O’Neill, said the project would mark a “transformative” moment for the company and insisted it would be a source of low-carbon gas. “The Scarborough reservoir contains only around 0.1% carbon dioxide, and Scarborough gas processed through the efficient and expanded Pluto LNG facility supports the decarbonisation goals of our customers in Asia,” O’Neill said. “Developing Scarborough delivers value for Woodside shareholders and significant long-term benefits locally and nationally, including thousands of jobs, taxation revenue and the supply of gas to export and domestic markets for decades to come.” Sign up to receive an email with the top stories from Guardian Australia every morning BHP chief executive, Mike Henry, said the merger would provide value for the resources giant’s shareholders. “Scarborough will provide a reliable source of LNG for global customers and secure gas supply for the domestic market, as well as ongoing employment in Western Australia,” he said. A report by the Conservation Council of Western Australia and the Australia Institute released in June found the project would release 1.6bn tonnes of greenhouse gases across its lifetime – or the equivalent of 15 coal-fired power plants. Under the company’s carbon abatement plan, Woodside will be allowed to increase its emissions of greenhouse gas over the next decade before attempting to reach net zero by 2050. The development has been fiercely opposed by environmental groups such as the Conservation Council of WA, which launched an 11th-hour legal action against the project last week. They say it represents the most polluting fossil fuel development in recent memory. The International Energy Agency said in May that limiting global heating to 1.5C, a goal set out in the Paris agreement, meant exploration and exploitation of new fossil fuel basins had to stop this year. Greenpeace Australia Pacific CEO David Ritter said that Woodside was “treating Australian’s with contempt” by forging ahead on the project. “Public outrage at what Woodside has planned - the threats to whales, the marine environment, the WA coastline and the climate - will continue to grow,” Ritter said. “For so long as the company persists on this course, the corporate name of Woodside will become synonymous with the destruction of everything that Australians hold dear.” Director of climate and environment with the Australasian Centre for Corporate Responsibility, Dan Gocher, described the company’s decision as a “desperate” attempt to escape its financial woes. “Woodside doesn’t seem to care about climate. It didn’t talk about climate or emissions in its release,” Gocher said. “It’s a disaster all round, to be honest.”