By Kim Ghattas
BBC News, New York
It is mid-afternoon in an airy, lower-Manhattan flat, on the ninth floor of a posh-looking building with a doorman.
The Beavan family compost their food waste with worms
It is a bit dark and there are no lights on. There is a strange quiet feel to the flat, perhaps due to the lack of any appliances - no fridge humming, no TV interference, even no air conditioning, though it is hot and humid outside.
Walk into the bathroom, and you will notice that there is no toilet paper, no bottles of shampoo or toiletries.
In the kitchen, berries and cheese are laid out on the counter and there are candles on the dining table.
This is the home of No-Impact Man, aka Colin Beavan, who describes himself on his blog as a "guilty liberal who finally snaps, swears off plastic... turns off his power... and while living in NYC turns into a tree-hugging lunatic who tries to save the polar bears".
He has dragged his wife, Michelle, and young daughter Isabella, along for the ride.
"The concept is that we should have no net environmental impact, which is, of course, technically not feasible," says Colin.
"So the idea is that we would reduce our negative impact and increase our positive impact."
Cutting the trash
The 43-year-old writer says he is not manically trying to offset everything, but he tries to get involved in environmentally friendly or sustainable projects around the city.
The first stage of the one-year experiment was to reduce rubbish. The family buys only second-hand goods and takes a hamper to the market.
Colin uses a glass jar he picked up from the trash as a reusable cup when he orders take-out coffee or juice.
Baking soda, vinegar and borax are used as cleaning products
Food is bought every other day from the nearby farmers' market on Union Square, and put in the hamper without wrapping.
The family then stopped using all carbon-producing transport, so they now walk or cycle.
They then shut down electricity in the flat - no more dishwasher, fridge or washing machine.
Now they are trying to reduce the amount of water they use, from the 80-100 gallons (303-379 litres) a day used by the average American, down to seven.
The more the experiment advances, the more drastic the changes become.
"I was a typical American consumer - I shopped a lot, I ate most of my meals in take-out containers, I took cabs everywhere," said Michelle, a journalist with a weekly business magazine.
Although she still goes to the office every day (on her bike), uses the elevator to get to the 43rd floor, turns on her computer and uses a mobile phone, she has had to redesign her whole life.
"It has been a shock to the system."
Michelle admits there were times when she regretted agreeing to the no-impact experiment, but says it has been one of the best adventures of her adult life.
"In essence, the project has really slowed down time, which is pretty amazing considering how fast time has become, and especially with us living in New York - you come home to a quiet, soothing cocoon."
For news from the outside world, there is the solar-powered crank-up radio, although the family rarely uses it.
A solar panel on the roof provides power for a laptop and one light.
From the kitchen, Colin brings out a wooden box with air holes on the sides. He opens the lid and scoops up a handful of dark brown matter that looks and smells like earth. In fact, it's a combination of fruit and vegetable peels and worms.
"This is the compost box, the worms take the food scraps and they turn it into compost," explains Colin.
The Beavans make sure they carry on recycling outside the home
What happens in the toilet, where there's no toilet paper?
"What I'll tell you, is this: There are many places all over the world that don't use toilet paper," is all he will say at first.
He then adds that because people wash, it is a lot more hygienic.
For detergents, laundry, body soap and toothpaste, they use a combination of vegetable oil, baking soda, vinegar and borax.
The Beavans realise that not everybody can afford to embark on a similar radical experiment or live like that long-term.
They also make clear that it is an experiment, and they have had their doubts about what works and what really makes a difference.
They insist they do not want to force their ideas on anyone else, but they feel happy about the difference it has made to their own lives.
Their life is now centred around the kitchen table, as well as activities such as riding bikes together.
"While there are a lot of people who think that we're freaks, our friends have been really supportive, and they do come over and play Scrabble with us in the dark," Michelle says.
But is it really possible to have no impact on the environment while living in a city where any resident is inevitably part of the system?
"There's no question that this city has an infrastructure and some of the impact of the city itself should get credited to us," said Colin.
"But the fact is that it is actually easier to live an efficient life in this city, and this is well documented. Here in New York, we emit about a third of the carbon per member of the population of the rest of the country, and it's because of the efficiencies of scale of this city."
The Beavans say that when the experiment is over, they will not simply revert to their old way of living.
"We're not going to bring the air-conditioner back. We're going to continue to ride our bikes everywhere. The fridge will come back, but will be used minimally," says Colin.
Michelle cannot wait to turn on the washing machine again. Hand-washing clothes has been the toughest change and a chore that has meant laundry is often not done, though Isabella enjoys stomping the clothes in the bathtub.
Colin is planning to write a book about his year as No-Impact Man - his publishers are looking at sustainable ways of publishing.
It may be a worthwhile experiment in the eyes of some, or a total waste of time by a tree hugger for others. But whatever you think of the Beavans, somehow when you leave their flat it feels like there is only one option - to walk down the nine flights of stairs.