An entrepreneur who made his pile in plastic bottles is ploughing it ba ck into the environmental cause. David Bowen talked to him
Tony Marmont is the very model of a modern environmentalist - almost. He has endowed two chairs in sustainable energy. Above his farm, high on a Leicestershire hillside, wind turbines pump power into the National Grid. The house is independent of mains services: heat is taken from the lake, power comes from solar panels. An electric car sits on the drive, not far from the hangar where his helicopter is parked.

His helicopter? Yes, Mr Marmont says with a touch of embarrassment, and it does only eight miles to the gallon. He presses a button, the doors of the hangar slide back, and the £750,000 Aerospatiale Squirrel rolls out serenely on its own trolley. When hecomes in to land, he touches another button and the trolley glides out to meet him. This is Thunderbirds, East Midlands style.

Mr Marmont, 65, is a man who can afford to combine idealism with a bit of fun. Two years ago he sold his family company, Carters Gold Medal Soft Drinks, to the Swiss company Hero. He will not say how much he was paid - but Carters was making a £6.5m annual profit, so it is fair to multiply that a few times. He is also in the process of selling Carter Wind Turbines, which built the generators in his back yard. That will leave him with his farm, the chairmanship of Crystal Polymers, a company he set up then sold to Shell, and the certainty that his bank manager will never trouble him again.

He has dedicated the rest of his life, and much of his money, to changing people's perceptions about energy. "I've made a lot of money in my lifetime," he says. "I want when I die to have used that money to good purpose." But, his wife Angela says, he isstill a little boy at heart. He has had his own aircraft for 35 years, and ideology is not going to ground him now. "I'm selfish, I like my toys," he admits.

He puts his conversion to the environmental cause down to his habit of flying everywhere. From his aircraft, he would watch the smoke from the giant Drax power station in Yorkshire floating across the sky. "As far as Cambridgeshire it was a thick black sludge. From the ground you would look straight through it, but I could see it because I was at the same level." He used to watch this with little more than detached interest. Then,12 years ago, he decided he should do something about it.

He has given £750,000 to establish the Sustainable Energy Technology Centre, with its own professor, at Leicester's De Montfort University, and has given Loughborough University £1m for a similar unit.

He also wants to lead by example. Schoolchildren come from all over the Midlands to see his farm, and he is keen to encourage other farmers to set up wind turbines. Farmers already sell sun, he says, because they convert light into crops: they should be prepared to sell wind- power too.

As a businessman he is, however, pragmatic about self-sufficiency. Although he will never recoup the quarter of a million pounds he has spent on energy-saving and generating equipment, he does not spend money for the sake of dogma. The wind turbines do not provide electricity for the house, because it is more profitable to sell it to the National Grid. Only 25 per cent of the turbines' income comes from selling the power. The rest comes from the Non-Fossil Fuel Obligation, a subsidy paid by the Government to alternative power providers (including nuclear stations). That means that in winter, when solar panels are weak, he uses the mains to recharge the 55 batteries that provide his house with electricity.

This pragmatism is reflected in his personality: He and his family come across as thoroughly normal folk. He does not proselytise, although the electric car is well-known locally as a buzzing billboard for his beliefs. It would be difficult to guess either that Marmont was a man with a mission, or that he had the money to have a good go at fulfilling it.

Tony Marmont's life has two parts: the conventional bit, where he made his money, and the green bit, where he spent it. The first bit is not uninteresting.

His father bought Carters in 1920, and ran it as a regional soft- drink operation, selling returnable bottles. When Tony joined as a driver in 1946 - aged 16 - the company had 12 employees.

In 1960 he bought his first aircraft, because he wanted one. But he soon discovered how useful it was, and found he could jam many more selling trips into a day than his competitors (at one time, he even carried a fold-up bicycle to travel from airfield to office). He also discovered it was handy for whipping customers over to Leicestershire to look at his factory, and to take engineers and salesmen over to the Continent and back in a day. The plane, bought as a toy, became part of his business life, and in the early 1980s he handed most of the flying over to a professional pilot.

Two developments, both starting in the late 1960s, propelled the company into the big time. First Marmont - who had taken over from his father - pestered the fast-expanding supermarket chains to take his product. Second, the restrictive practices of glassmakers caused bottle shortages, and forced him to look for other supplies.

Initially he imported bottles from Poland, with limited success. "Ten per cent of the bottles arrived broken, and I had to fly over there to teach them quality control," he says. Then he heard about an American plastic called PET, which could be used to make bottles. He went to investigate, and decided to set up the Scunthorpe factory to manufacture PET.

This both freed him from dependence on unreliable or greedy suppliers, and allowed him to design a completely new type of soft-drinks bottle. He was the first manufacturer in Britain to sell the now-ubiquitous two-litre bottle. He convinced the supermarkets it had advantages over traditional glass, and Carters started growing rapidly.

By 1980 the company was employing 200 people, and Marmont decided to invest £6m in a new factory at Kegworth. His fascination with boys' toys naturally pushed him towards high technology, and he built the most advanced soft-drinks plant in Europe. Where 28 worked on the production line in the old factory, now three did. Automated guided vehicles stacked the drinks as tightly as possible - but a computer remembered where each type was, so they could be retrieved easily. And when hot weather pushed demandthrough the roof, output could be reprogrammed at the touch of a button.

By bringing hi-tech to a traditionally low-tech sector, Marmont gave Carters a big lead. He did not, however, believe in keeping his secrets to himself. Weekly visits were arranged for locals, schoolchildren and even rivals. "Pepsi-Cola hired Concorde every Wednesday for six weeks to show their people round," he says proudly. He believes this unwonted openness paid off. "I gained more than I lost," he points out, "because other companies would then invite me round their factories."

By ploughing cash back into the operation at the rate of £6m to £9m a year, Kegworth reinforced its lead. By the time Marmont sold out to Hero, it had 20 per cent of the UK soft drinks market and employed 650.

Meanwhile, he was becoming more involved in sustainable energy. His first energy-saving device, to extract heat from the lake, was installed more because he found it intriguing than because he was seeking to save the world. It can take heat out even whenthe lake is freezing.

Gradually, however, he became more convinced by the environmental arguments and started converting his farmhouse into a green showcase. From the outside it looks unremarkable, but in the basement a range of devices generates electricity and heat in the most efficient way possible, and makes sure as little as possible is wasted. The whole system is monitored by a computer installed by Loughborough University.

He installed his first two wind turbines in 1990, then in 1992 travelled to Texas to view a new design made by a company called, coincidentally, Carter Wind Turbines. He liked it so much he bought the company, and transferred it to England. As well as making turbines, it owns a large wind farm in Cumbria, and has won big orders in China and India. Now, however, Marmont has decided it is time to move into semi-retirement, and he is in the process of selling the company.

But this is not the end of Tony Marmont the businessman. He is building a new office in a field close to the house, from where he will organise his affairs. The roof, naturally, will be made of solar panels.