Ireland's network of disused mushroom houses could be the ideal infrastructure to develop a hydroponic farm system which could in turn reduce our dependence on imports of herbs, salads and small greens.

Hydroponic farming uses water rather than soil to grow plants.

It uses much less water than conventional growing, a tiny amount of space and is immune from adverse weather conditions because it is indoors.

One farm in Tipperary has started the transition. Near Ballyporeen, one of eight mushroom tunnels is now converted into a vertical farm.

Brian O’Reilly had been growing mushrooms for almost two decades, but tight margins and an anxiety over the potential impact of Brexit made him change course.

"The risks were too high so we decided to step back. Tighter margins were number one and Brexit was the number two reason, and labour was a problem too," he said.

Now, he has turned to basil. His first crop will be harvested in the coming days and will be sold into the catering industry.

Mr O'Reilly said the process of growing herbs and small greens is similar to mushrooms. There is a cycle and within 32 days from planting a seed, the basil is finished.

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It is grown in tiny pods on shelves with the roots stretching down to nutrient-rich water. Bright LED lights encourage the growth, as does hot air blowing into the tunnel.

A wind turbine nearby generates the electricity and a hot humid house means the plant thrive. But the lights are also powered down for hours in order to let the plants sleep.

It looks a million miles from any conventional farm. The tunnel is filled with rows of white plastic shelves, with tiny holes through which the plants appear. Water is circulating under the shelves and overhead there are strips of lighting; white, red and blue.

It is bright and humid with the constant hum of air being pumped in and there is a gentle trickle of water flowing through the system.

Farmony, an Irish technology company, has developed the technology being used in Ballyporeen.

It has built farms in several countries and said the system could make Ireland self-sufficient in herbs and small greens within a few years.

Farmony's John Paul Prior said the range of plants that can be grown is vast and goes way beyond herbs.

He said: "In Ireland, we grow between May and September/October. Imagine if you could recreate that perfect summer's day all-year round.

"That is what we are doing with controlled environment farming, so we could come close to self-sufficient with all your leafy greens, all your microgreens and all your herbs."

Ireland imports the vast bulk of those products and the development offers a huge opportunity to expand the horticulture sector in Ireland.

It is environmentally positive too. If mushrooms houses are used, it is utilising something that has limited suitability for anything else. Farmony claims that the system uses 90% less water than conventional farming methods and is pesticide free too.

The tunnel in Ballyporeen is part funded by the Department of Agriculture as a pilot project and Mr O'Reilly is already testing crops other than basil.

"We are growing microgreens, peashoots and coriander at the moment. We are experimenting with them, we can change our model at any time and grow to what the customer wants," he said.

"When you think of it, this basil which we are growing would normally be imported, sometimes from thousands of miles away, from Morocco, Kenya, Israel, Spain or the UK. We are replacing that. The food miles are being dramatically reduced and we can do it without worrying about the weather outside."

Abandoned mushroom farms are dotted all over the country. There were more than 400 growers at one point, now there are just a few dozen. It is a tight margin business, which is dominated by a few companies and is almost entirely export dependent.

Last year, Ireland exported €102m worth of mushrooms. Up to September this year, we exported more than €82m worth of mushrooms.

Any delays at ports after Brexit could have a huge impact on delivering fresh product to supermarkets in the UK. The possible imposition of tariffs is also an issue.

The Government wants to expand Ireland's horticultural offering. It is lower emitting than sectors such as beef and dairy and there is huge scope for expansion.

Often, our climate is an issue. We have a shorter growing season than other countries and they can also offer scale and a cheaper cost base.

There are some areas of Ireland which grow high quality vegetables, but it is a sector in decline over recent years.

The dominance of the big multiples as the primary buyers has tightened margins and many growers complain that the sector is controlled by too few buyers. Up to September this year, Ireland imported €146m worth of vegetables alone.

Its dependence on UK imports of potatoes and other vegetables could be a problem after Brexit, but it is something which the sector is aware of.

Farmony hopes that developing a network of vertical farms could dramatically reduce our food miles, reduce a reliance on imports and also create jobs and revitalise a declining sector.