The Selfsufficient-ish Bible [Hardcover]

There are plenty more tips on how to cope with pests that munch your homegrown produce on selfsufficientish.com, the website that Andy and his identical twin, Dave, have been running since 2004. They call it a guide to "almost self-sufficiency". And now there's a book, which is what we are here to discuss. The brothers have spent the past year compiling The Self-Sufficient-Ish Bible: An Eco-Living Guide for the 21st Century. It is, they say, the book they wish someone had written for them when they started growing their own food and living more ethically.

How two blokes with a couple of allotments in a city came to write a self-sufficiency book comes down to the concept behind "self-sufficient-ish", a word as laid-back as the brothers themselves.The idea is that there is a middle path for people who are limited by time, space or money, which is most of us really. They say that anyone can take a few small steps to self-sufficiency, wherever you live. Their approach is tolerant and flexible. You do what you can and don't worry too much about the rest.

With matching ponytails, spectacles and a quirky sense of humour, Andy and Dave, 33, belong to a gentle breed of green-living enthusiasts, softly spoken yet firm in their beliefs.Having spent most of their time since university dabbling in part-time jobs - which they still do to make ends meet - they are experts at simple, home-made living. They don't have mortgages or cars, cycling everywhere around their rented homes in Bristol. They believe in making do with what they've got rather than "working all day just so you can buy new things".

From mending clothes to hay-box cookers

The book is pleasantly devoid of stuff to buy. Many green living guides are full of websites promoting luxury green products but the Hamiltons are dubious of ethical consumerism. There are lots of things in the book that might seem better suited to dark greens, even though it is fascinating to read about them.

Creating a reed bed sewerage system in the garden, for example, which uses plants to purify waste water, is one of their wilder suggestions, which they haven't tried themselves. But there are also seasonal recipes, energy-saving tips and advice on mending clothes, as well as ideas such as making a hay-box cooker, which can keep a casserole cooking without power (once you've brought it to the boil on a hob) for 20 hours. "It's mostly stuff everyone used to know, but now we're beginning to lose it," Andy says.

Like the book, their website contains masses of practical information on how to grow your own food, but it distinguishes itself from other gardening websites by including information on using wild foods to make natural remedies and home-brewed beer, as well as advice on general aspects of green living. Andy has already been out collecting dandelion heads this morning to make cough syrup (the recipe's simple, you boil them up with sugar and water).

The most popular bit of the website, Dave tells me as he passes me a tangy sorrel leaf to chew on, is the forum where people can discuss anything from eco-parenting to what to do when badgers damage your beetroot patch.

Looking around the allotment, it seems that March is not a good time of year to be self-sufficient. Although there's a rhubarb patch, a few rows of leeks and some spinach that has survived the winter, as well as a giant cabbage plant lording it over the plot, I wouldn't want to survive on this lot. Undeterred, Dave finds some purple sprouting broccoli and bundles it into a bag for me to take home.

He says there's not enough land in the UK for everyone to be totally self-sufficient so it's a good thing that there are lots of people like them only half-doing it. In the summer months, they briefly achieve total self-reliance; the rest of the time they manage to put something homegrown on the table every day.

Growing up in suburban Northamptonshire, their semi had a big garden with apple trees and a fruit patch. They both remember making nettle soup, aged 8, with their parents. It was Dave who became interested in organic food while studying nutrition and food science at Oxford Brookes University. "I couldn't afford to buy it so I convinced my landlord to let me plant up the entire garden with veg," he says.

It's refreshing that in spite of their horticultural interests, Andy and Dave are far from rural- living evangelists. They are proof that you don't have to pack up your urban lifestyle and take off to the far corners of rural Britain to live a green lifestyle. "There are lots of things that are easier to do in a town, like getting around without a car," says Dave; neither of them has a driving licence. They enjoy the trappings of the city, going to gigs and cinemas, and Andy especially likes anonymous urban pubs.

The art of getting something for nothing

A large part of the pleasure they take from their lifestyle is its cheapness. They have perfected the art of getting something for nothing, whether it's a sofa found in a skip or a voucher from a rail company obtained after complaining about a cancelled train. Both brothers have lived on a shoestring for years and doubt they'd change much if they had more money. "Before we buy anything, we think, can we get it secondhand, can we find it ourselves or can we make do with something we've already got?"

Although they know they spend more time together than most married couples, they seem to get on absurdly well. I prod for tensions. Who's greener? "Probably Andy," Dave says, diplomatically. "I live in a shared house so I have to compromise more." He prefers to buy organic milk and shop in smaller stores but, when his housemates do the communal shop, they sometimes go to Asda. Groans all round.

Half an hour's cycle ride away from Dave's student-style home in Montpelier, North Bristol, Andy faces his own challenges living with his girlfriend. "We argue about stuff, and I'm probably an arse to live with," he chuckles. "She likes the heating on more than me and I find myself going through the bin and demanding why certain things have been thrown away."

When it comes to their guilty green secrets, this, at last, provides some healthy sibling conflict. Andy teases Dave for flying because he has given it up and is even prepared to go overland to a friend's wedding next year in South Korea. It will involve ten days of travelling, a stint on the Trans-Siberian Express and £1,000, but as Andy points out, it will be a lifetime experience.

A strict vegetarian, Dave says that Andy shouldn't eat meat because of the energy involved in production and transportation.

When I ask what they think about the theory promoted by the scientist James Lovelock that climate change has taken hold already and anything we do now is too little, too late, their response is united: "It's a happy lifestyle even if it is too late to prevent the planet from warming. Rather than doing nothing and accepting our fate, we might as well enjoy ourselves."