Imagine a factory on an industrial estate ten miles outside Antwerp, churning out 120,000 household cleaning pro-ducts every day. Sounds grim, doesn’t it? Well, the Ecover HQ would surprise you. The building that houses the UK’s favourite green cleaning company is made from several tonnes of sustainable wood and recycled bricks. Its crowning glory is a 5,600 square metre green roof; a living, breathing meadow of vegetation.

Where most of us have bricks and mortar, here there are cacti and flowering plants, including a 30cm layer of soil acting as insulation. Once combined with south-facing positioning and a ceiling studded with skylights, it allows the building to run without central heating or air-conditioning, and with little artificial light.

When I visit on a chilly March day, light floods through the roof and gas heaters hang unused from the ceiling. Outside, eco-friendly Toyota Prius cars line up: company cars for the management team. The rest of the 80 staff members are financially rewarded for taking public transport, cycling or joining car-share schemes. Not normal behaviour for a factory, but this one has high standards. It has the title of the world’s most ecological factory to maintain.

The building is central to Ecover’s approach to the environment, says the managing director, Mick Bremans. “There’s no point telling our customers to refill or recycle Ecover bottles if we’re not doing the same here. We think about the life cycle of the product, not just the ingredients, but the energy involved in its manufacture and disposal too,” he says, showing me a stash of cardboard delivery boxes, all with several layers of address labels. “Each box is used on average 15 times, saving us money, too.”

Sometimes, however, its eco-commitment goes beyond the call of duty. Take the case of the falcon chicks. Halfway through my tour, Bremans wants to show me something. My guess is that we’re heading upstairs to the lab, where new ingredients, such as coconut oil and other plant-based starches, are researched and developed as an alternative to the petrochemicals used in most cleaning products.

Instead, I am herded outside, past rows of whizzing washing machines testing new Ecover products, and manned by a team of bouncy young workers (“The green image attracts younger people,” he says), past a room with vast mixing tanks feeding liquid in overhead pipes and depositing it into recycled plastic containers, even past Bruno, a low-energy robot busily boxing up products with minimum movements.

We reach a standstill outside the factory, right next to a whiffy water purification system that recycles waste water. Bremans is pointing to a spot under one of the enormous wooden beams. “Can you see our falcon chicks? They come here every year so we built them a wooden bird box,” he says. Like I said, this is no ordinary factory.

Ecover has a history of standing alone. Set up in 1980, it started life on the shelves of health food shops, chosen only by hardcore green enthusiasts. Back then, its aim was the same: to make cleaning products from plant and mineral-based substances that biodegrade easily.

Twenty-six years later, after considerable product improvement, Ecover jostles for space in most leading supermarkets. Sales were up 30 per cent last year; it sells to 22 countries (it’s the No 2 green cleaner in the States).

As it encroaches on the territory of the big players, Unilever and Procter & Gamble, a significant proportion of us are taking notice. According to a recent survey by the Energy Saving Trust, 34 per cent of us use green cleaning products daily.

By far the greatest compliment is that Ecover’s business model has led the way for others. (see test panel, far right) Although Ecover claims 90 per cent of the UK green cleaning market, there is also a range called Bio D, which has biodegradability as its key focus, as well as Naturally Inspired, the Marks & Spencer line of eco-cleaners. Fresh from the States, a company called Method has launched over here with the catchline “people against dirty”, meaning nasty chemicals rather than general grubbiness.

So what’s brought about this sudden mistrust of bleach? Bremans thinks the rise of the “conscious consumer” has played a large part. “We are getting better at questioning our consumer choices and how they will affect the environment,” he says. In these days of growing green awareness, it’s difficult to keep a cupboard full of bottles with ingredients that you can barely pronounce let alone vouch for their eco-status.

Another selling point is what Ecover calls “skin compatibility”. Plant-based products are popular with people who have sensitive skin or respiratory problems such as asthma. But beware, this leads to an inconclusive debate about whether the chemicals we use in our homes could be harming our health, a topic quick to catch the attention of the consumer but not easy to verify. EU regulations are rigorous, reminding us that if there was a known effect on health, the product would not be on the market; environmental groups, on the other hand, take issue with what is “known” and call for further long-term research (see panel, below right).