Sirius Minerals announced that its fertilizer project in North Yorkshire, Britain, could cost as much as £2.5billion for an initial first phase and that it could take five years to build the mine, the largest mining project in Britain.

Costs for the project could rise to £3.7 billion to get the project to its intended capacity. Before then the project could be earning £1 billion a year, The Financial Times reported.

The figures are revealed in Sirius’ most detailed study of the project, which sets out the detailed financial case for proceeding with one of Britain’s most ambitious industrial investments.

Sirius said the mine could start in 2021 and reach capacity for its first phase in 2023.

The mine would create thousands of jobs and lift United Kingdom exports while the mineral deposit under the North Yorks Moors could be mined for at least 50 years, according to the company.

Sirius now needs to raise £1.1 billion in debt and equity to start the first phase of construction of the mine near Whitby.

Chris Fraser, chief executive of Sirius, said the business would “sit as a world leader in the fertilizer industry based here in the UK. It is expected to have a low operating cost structure, high margins and a very long asset life in one of the most business friendly, stable and dynamic economies in the world.”

The York Potash project would “create thousands of jobs in North Yorkshire and Teesside, deliver billions of pounds of investment to the UK and put the country at the forefront of the multi-nutrient fertiliser industry”, he said.

Sirius also said it hoped to be able to lift production at the mine beyond the level so far approved by planning authorities.

The definitive feasibility study for the mine is the first since the company won planning permission for the project in July after years of arguments over whether it should be allowed in one of the UK’s most protected landscapes, the North Yorks Moors national park.

So far Sirius has based its promotion of the project on a less detailed study done in 2012 and amended in 2014. Previous estimates have put the cost of the project at about £1.7 billion to £2 billion.

Hundreds of Yorkshire residents have already become Sirius shareholders while local landowners have been promised royalties when the mine starts production.

The mine is the largest project to be put forward in the UK since the development of the Selby coalfield, also in North Yorkshire, was started in the 1970s.

Sirius’ mine will be underground, exploiting a seam of polyhalite — a mineral that can be used as a fertilizer — 1,500 m below the national park. The seam is an average of 25 m thick, the company’s study said.