A plan to build a huge potash mine in the North York Moors National Park was approved this week by the narrowest possible majority.

Following more than eight hours of discussions and presentations, a special planning meeting voted by eight votes to seven to allow the York Potash Project to build the mine just south of Whitby - against the advice of the national park's own director of planning.

York Potash - part of the Sirius Minerals group - says the scheme will generate more than 1,000 jobs. The plan has the backing of local Labour and Conservative MPs, and there were cheers from scores of supporters who gathered for the planning meeting at Sneaton Castle in Whitby to hear the decision.

But the park authority's own director of planning, Chris France, made clear in his report to the meeting that he felt the mine should not be approved - and that the economic benefits did not, in his view, outweigh the potential impact on the national park.

There were also objections by a consortium of 29 campaign groups, including the Campaign for National parks, the National Trust and the Campaign to Protect Rural England (CPRE).

But what is potash? How will it be mined? Is there a risk of environmental damage to the national park? And what benefits might the mine bring to the region?

Here, we try to answer these and other questions...

What is potash?

Potash is a vital ingredient in fertiliser. Farmers use it to replace potassium in the soil to maintain good crop yields. The York Potash Project aims to extract a form of potash known as polyhalite, which combines four of the six essential nutrients plants need - potassium, magnesium, sulphur and calcium. The York Potash Project says the growth in the world's population, combined with the increase in biofuel technology which means less land is available for growing food crops, has led to a big rise in demand for potash, and in particular polyhalite. The mine would be the first new potash mine in the UK for 40 years.

Where will the mine be based?

The proposed site for the mine head is at Dove's Nest Farm and the Haxby Plantation next to the B1416 about 2.5 miles south of Whitby - inside the national park and close to the Coast-to-Coast long distance footpath.

Why does the mine need to be in the national park?

The richest polyhalite ore reserve in the world - more than 2.6 billion tonnes of it - lies beneath the national park in the area being targeted by York Potash. This is between Whitby and Scarborough, extending 16km inland from the coast and up to 14 km offshore. "We can only mine where the minerals are," says Matt Parsons of York Potash.

How will the potash be extracted?

A deep shaft mine will be sunk to a depth of up to 1,500 metres. Rotating cutting tools will be used to dig the potash out of the rock. It will then be lifted to a depth of 360 metres, where it will be transferred to an underground mineral transport system without ever reaching the surface in the national park. This system will convey the potash through a tunnel to a proposed new processing plant at Wilton on Teesside, which has already been granted planning approval by Redcar and Cleveland Borough Council. After processing, the potash will be transported via conveyor to a new quay at Brown Sands port on Teesside, from where most will be exported.

Initially, the mine is expected to produce 6.5 millions tones of potash a year, rising to 13 million tonnes a year at peak production. It would be the largest producing potash mine in the world.

What would be the impact on the national park, and what would York Potash do to minimise this?

The mine will not produce waste pollutants, and will not damage the water table, York Potash says. There are no toxic wastes produced, because every part of the polyhalite mined will be processed for use. That processing will take place in Teesside, not in the national park.

There will be winding gear and two shaft buildings at the mine head, together with admin buildings and a car park. The mine head will be sited away from protected moorland, York Potash says. As much as possible of the mine head plant, winding gear and other equipment will be sunk below ground level. Material excavated during construction of the mine shaft will be spread around the mine buildings in mounds and bunds to screen them from view. The processing plant will be at Teesside, and the mined potash will be transported there by a tunnel.

Despite these assurances, in his report to the planning meeting, the North York Moors National Park Authority's director of planning, Chris France, warned that the mine would have "a wide range of significant environmental effects, especially in terms of visual, landscape and traffic impacts which will be significant ...during the prolonged construction period and beyond before restoration proposals take effect". During construction of the mine, Mr France said, the impact would "inevitably cause harm to the tourism industry." There would also be "ongoing and permanent harm to the special qualities of the National Park in terms of loss of tranquillity, loss of the park’s landforms, and its sense of wildness and remoteness which cannot be replaced."

York Press:

Artist's impression of the proposed new potash quay at Teesside

What will be the benefits to the local community?

York Potash says the mine will generate more than 1,000 direct jobs at full production and thousands of indirect jobs in the support and supply industries. It will also generate up to 1,700 jobs during the construction period.

The permanent jobs at the mine will include engineers, miners, electricians and support workers. At least 80 per cent of the jobs will be given to local people, from the Teesside, Scarborough and Ryedale area, York Potash's Matt Parsons said.

At peak operation, the mine will add more than £1 billion to the UK's GDP, the company says - increasing the size of the North Yorkshire economy by 10 per cent, and reducing the UK's trade deficit by up to 4 per cent.

The annual salary bill once the mine is in operation is expected to be about £35 million - money that will make its way into the local economy.

The company has also pledged to make local payments of £48 million a year. Of that, £29 million a year will go to local mineral rights holders, including residents of the national park, while £6 million a year will go to the York Potash Foundation to pay for local community projects.

In addition to the annual payments, the company has agreed to pay £175 million, under a Section 106 planning agreement, to mitigate the impact of the mine on the national park. This will include £30 million towards tourism promotion, a £56 million contribution to the national park's management, and £75 million for tree planting. This money would be paid out over 100 years, but much will be disbursed during the initial five-year mine construction period, Mr Parsons said.

What is the timescale for building the mine?

York Potash says it expects the mine construction to take five years. The extent of the potash reserves beneath the moors suggest the mine could be in operation for more than 100 years, Mr Parsons said.

Do opponents have any further chances to overturn the decision?

Opponents of the mine, including the Campaign for National Parks, have called for a public inquiry. The Department for Communities and Local Government is understood to be considering whether to call the proposal in. "They have asked for more details on why it was approved," confirmed Chris France, the director of planning at the North York Moors National Park Authority.

Short of a public enquiry, the only other means opponents now have of preventing the mine from going ahead would be to mount a legal challenge. Such a challenge could only look at the process by which planning approval had been granted, however - not at the details of the application itself.


What they say: opposing views on the proposed potash mine

Sirius Minerals chief executive Chris Fraser, speaking after the meeting: "We're obviously very happy but the hard work only begins now. We'll go and celebrate but then we'll get on with the real job of building a mine."

Local MPs Robert Goodwill (Con, Scarborough and Whitby), Anna Turley (Labour, Redcar) and Kevin Hollinrake (Con, Thirsk and Malton) in open letter supporting the mine: "The York Potash project... will bring enormous social and economic benefits to the area by creating jobs, improving training and education opportunities for young people, providing community facilities and by generating more wealth in the economy."

Barry Dodd, chairman of the York and North Yorkshire Local Enterprise Partnership: the mine was the biggest single investment in the north of England "by a billion miles".

Chris France, director of planning at the North York Moors National Parks Authority, in a report to the planning meeting: "It is ... considered that the economic benefits and extent of the mitigation/ compensation offered through planning obligations do not outweigh the extent of the harm."

Ruth Bradshaw, campaigns manager of the Campaign for National Parks: "This project is completely incompatible with national park purposes ...the promised economic benefits could never justify the huge damage that it would do to the area's landscape and wildlife and to the local tourism economy."

Harry Bowell, director of the National Trust's north region: "To have a development of this scale going ahead within a protected landscape sets a worrying precedent for the future of all our National Parks... The full cumulative impact of the proposal needs to be fully understood, which can only be properly achieved through a public inquiry. We will continue to ask for the Secretary of State to call in this application.”