By Clare Davidson
Business reporter, BBC News, Leicester
Water pressure alone is pushing hundreds of potatoes from the back of a 28-tonne lorry towards what look like oversized funnels.
But it won't take long until these humble spuds are transformed, at what is the world's largest crisp factory, just outside Leicester.
Eleven minutes later, these rosetta potatoes will be Walkers crisps - flavoured, packed in bags and ready for distribution.
"Spuds are just like us," says Pete Flanaghan, sustainability manager of Pepsico UK and Ireland, the parent firm of Walkers.
"Every time they hit something, they bruise," he says over the din, gesturing by bringing his two fists together.
One after another, the spuds come tumbling down hydro-cyclones - which wash off any excess mud.
Bruising breaks the cells, which means less nutrition. The water helps softens the blow, he explains.
In fact, water is a crucial ingredient throughout the factory, from cleaning and rinsing to processing.
Every year, this plant uses 700,000 cubic metres of water.
Approximately 42% of water used is recycled.
But a growing awareness of a need for water efficiency has prompted Pepsico to set itself a bold target.
Within 10 years, it wants to achieve zero water intake at the Walkers' sites, starting with the Leicester location, eliminating the need to bring mains water onto the site.
But knowing where to cut down water requires knowing exactly how much is used and where. If you don't measure it, you can't change it, says Mr Flanaghan, between greeting everyone on the floor personally.
He uses one seemingly insignificant step in the crisp making process to illustrate his point.
"You see that dish?" he says, pointing to the small surface inside a cylinder. Water hits the dish before spraying evenly on to sliced potatoes to remove excess starch.
"That used to be a teaspoon shape. But what happens when you run a tap onto a teaspoon?" he asks rhetorically. "It flies off in all directions, unevenly."
By changing that one design, water is saved, he says.
Changing attitudes internally is also crucial to reduce water wastage, adds Mr Flanaghan.
"We've had leak busters," he says.
Training sessions were held with staff to raise awareness of the need to cut water wastage. It involved identifying leaks and quickly taking action to rectify them.
It sounds naff," he confides, "but it has worked."
Elsewhere, a trip to farmer James Daw in Staffordshire, a long-time supplier to Walkers, reveals an increasing awareness of water usage in the growing phase.
"The thing about potatoes is the detail," says Mr Daw, as we visit a recently-harvested potato field.
If water has to be added - to supplement rainwater - sensors in the ground relay exactly how much to avoid unnecessary drenching.
"It all boils down to more crop per drop," explains Martyn Seal, sustainability director for Pepsico International's European region.
And yet there seems to be an inherent paradox in potatoes.
||Litres per unit
||Size of unit
||Litres per kg
|Sheet of paper
||A4 sheet of 80gsm
|Cup of tea
|Cup of coffee
|Bottle of beer
|Slice of bread
|Packet of sugar
|Chunk of cheese
|Packet of rice
|Pair of jeans
While 75% of a spud is water, turning them into crisps is basically about removing the water, says Mr Seal, lowering his spectacles.
What goes in at the growing stage has to be taken out at the processing stage.
"Potatoes are a very thirsty crop," explains David Wilson, an agro-manager for Pepsico UK and Ireland, who co-ordinates farmers including Mr Daw.
"A challenge is how to reduce the water content," says Mr Daw knowingly, pointing to muddy potatoes as they rumble along a conveyor belt on the farm.
Walkers is involved in a pilot scheme, involving academics from Nottingham University, to capture water extracted from potatoes during slicing and frying, treat it and reuse it, says Pepsico's Mr Seal.
When asked what would make the optimal spud, Mr Seal looks almost dreamy.
It must be reliable to process, of a high standard and good for crisps, he says.
If a potato could contain less water, this could have other benefits.
Less energy would be needed to dry and fry the potatoes, which would lower emissions and costs.
Pepsico UK and Ireland is also working with the Scottish Crop Research Institute to investigate new potato varieties that would contain less water.
The firm is also investing in research into irrigation, to compare the effectiveness of different systems and conserve water.
Climate change affects seasons and rainfall, so more drought-resistant crops will be needed. But Mr Seal is quick to add that developing new varieties of potatoes can take years.
Such concerns seem a long way off as the moist earth squelches underfoot in the farm, testimony to another wet week.
But multinational firms such as Pepsico are having to assess operations globally, and there is growing stakeholder pressure to do so.
James Daw applauds this. "It is right we should think more about water. We, after all, are the custodians of the land."