Booking my ticket to Hastings to visit Craig Sams, I notice a link on the train operator's website that allows me to check the carbon footprint of my trip. It's a fitting start to a journey to meet one of the foremost pioneers of the green movement – not least because the latest endeavour of the man who brought the macrobiotic diet to Britain and made organic chocolate one of the most fashionable foodstuffs of the past decade is an ambitious global carbon-capturing initiative that may hold part of the answer to climate change.
Sams, now 65, decamped to the Sussex town from west London full-time with his journalist wife Josephine Fairley, 52, eight years ago, as they were slowly disentangling themselves from Green & Black's, the enormously successful organic, Fair Trade chocolate brand they founded together in 1991. In the time that Sams and Fairley owned the company, they managed to change the taste of a nation, convincing consumers weaned on insipid milk chocolate that the bittersweet delights of their rich, cocoa-heavy offering were a more sophisticated, not to mention ethical and healthy, choice.
For some, the multi-million-pound sale might have been the beginning of a comfortable retirement, but neither is the sort to rest on their laurels. Long before the deal was completed, the pair was already knee-deep in a new project, Judges, an organic bakery in Hastings Old Town, which was soon followed by the Wellington Square wellness centre, turning the seaside town into something of a healthy-living destination.
"I still think that introducing the macrobiotic diet with my brother through our shop and restaurant and Seed – a journal of organic living – was the most important thing I ever did," Sams says of his wide-ranging influence. "But ultimately we haven't been anywhere near as successful as McDonald's. And that's depressing. Mind you, nobody ever subsidised brown rice and vegetables, yet the organic market keeps on growing, because people really do care about these issues." '
Home is a three-storey Georgian town house, a few hundred yards up the winding street on which Judges sits. Its gorgeously imperfect interior is stuffed with objects and furniture that suggest a life well lived. It is not, however, the kind of place one would necessarily expect Britain's premier green couple to inhabit. Colourful and cluttered, there is none of the austerity that one might imagine to be the reality of saintly eco-living.
But then, a large part of the success Sams and Fairley have had might be attributed to the combination of exactly this brand of bohemian glamour with an area that sometimes risks being perceived as worthily dry.
Nebraska-born Sams' groovy, counter-culture credentials go back to the 1960s, when he and his brother Gregory opened Seed, the UK's first macrobiotic restaurant and shop, on London's Portobello Road, attracting a mixed crowd of hippies and wealthy Holland Park denizens.
Around the same time, Sams imported a few hundred Afghan coats that he had spotted on his travels in Asia to sell on Chelsea's King's Road. Among the first takers were the Beatles, and the rest is fashion history. His gift for anticipating, if not creating, the zeitgeist is almost preternatural.
Later he would bring organic peanut butter and baked beans to the consumer market with his Whole Earth Foods range, and transform the British Soil Association from a sleepy, minor charity into the UK's leading organic organisation in his exceptional three-term tenure as chairman.
Fairley has also led what might be considered a pretty extraordinary life. Made Britain's youngest magazine editor at 23 (at Look Now, a women's title), she has carved out a career as a highly respected beauty journalist and author in an area of the industry not known for its candour or integrity.
She also happens to have been best friends with the late Paula Yates, and remains close to Fifi Trixibelle, Peaches and Pixie – Yates' three daughters with Bob Geldof – and Tiger Lily, whose father was the singer Michael Hutchence.
On the morning I visit, the Sams-Fairley household is a hive of activity, although I get the impression that this is just an average day by their standards. As Sams makes tea for us in their cosy kitchen ("soya or non-homogenised cow's milk?"), two willowy young girls and an even willowier young man swirl through the kitchen, making breakfast and proffering almond croissants from Judges. One of the girls is Fairley's assistant – the couple both work from home – and the other two, it transpires, are Peaches Geldof's flatmates, over from New York.
Sams takes it all in his stride. Handsome, tall and tanned in an unconsidered, outdoorsy way, if you didn't know who he was you might take a stab with Hollywood actor or a former rock star – although he has aged far better than the excesses associated with either career would have allowed.
On the contrary, he is a flesh-and-blood advertisement for macrobiotic living. He swims in the sea daily in all but the coldest months and tells me he hasn't seen a doctor since 1965 – the year some friends converted him to the macrobiotic principle of eating less and from lower down the food chain.
He is charismatic in an unselfconscious way, but his laid-back manner belies a fierce intellect and an ability to range engagingly across lofty ideas and practical minutiae, which become apparent when we sit down in Sams' back garden to discuss the latest commercial venture firing his imagination, Carbon Gold.
Set up in partnership with the former music promoter and Sams' fellow eco-entrepreneur Dan Morrell, Carbon Gold is a company with a bold plan to get farmers around the world transforming their agricultural waste – which would otherwise be burned or left to rot, releasing carbon dioxide into the atmosphere – into a type of charcoal known as "biochar". Produced by heating plant matter in the absence of oxygen, biochar is essentially a stable form of raw carbon, which can be used to fertilise soil.
Simply as a low-cost, organic means of regenerating degraded farmland, it represents an exciting development. But it is its potential as a means of sequestering carbon, reducing carbon-dioxide emissions and slowing climate change that could have the greatest impact on the future of the planet.
The project is the crystallisation of something that has been on Sams' mind, both consciously and subconsciously, for many years: "I was born on a farm," he explains. "When my great-grandfather first ploughed that land in Nebraska, there were 40 to 50 tonnes of carbon per hectare; there are now five. When I went back there to visit at 12 years old, I remember being appalled to see these huge gullies where hills had been eroded – gaping holes where there had been soil. Back then I didn't understand what soil was, but soil is carbon. And all that carbon was just being ploughed away."
Sams' eureka moment arrived decades later, around the time of the Green & Black's sale, when he read about an ancient technique used by pre-Columbian native Americans to enrich the poor soils of the rainforest in Charles ' C Mann's 1491, a history of the Americas before the arrival of the Italian explorers. That practice was the production and burial of biochar, and its legacy can still be witnessed today in the Amazon basin in the form of swathes of fertile, black earth known as terra preta.
"Suddenly, I thought, 'Golly!'" recounts Sams, full of renewed enthusiasm at the memory. "Instead of organic farmers putting 10 tonnes of compost onto an acre and 90 per cent of that going back into the atmosphere as CO2 in five years' time, and the remaining 10 per cent being gradually lost with every ploughing, here is a way that you can take 10 tonnes of biomass [plant material], reduce it to carbon, put that in the soil and most of it will stay there for an indefinite period.
"I had already got into the idea of re-carbonisation of soil in the mid-1990s when I took Whole Earth organic corn flakes carbon-neutral by planting trees, which was primitive but genuine, and we discovered that the carbon footprint of our corn flakes was much lower simply by virtue of them being organic. We found that the carbon content of the soil they were farmed on increased incrementally every year, whereas the carbon content of non-organically farmed soil decreases incrementally.
"Then I read the book and it knitted it all together and I suddenly saw that this was a very elegant way to draw together all these threads. It ramped up the potential not just for organic farming, but for all agriculture to reverse the loss of carbon from soils."
The beauty of the scheme, as Sams sees it, is that it could turn the futuristic concept of carbon capture and storage into a low-tech, low-cost reality that can be rolled out to every corner of the earth. "Our view is that small is beautiful and lots of small-scale processing of biomass is the way forward," he says. "We've looked at all the technologies out there and we found that actually you can get a biochar yield of up to 35 per cent of your biomass with very simple, cheap technologies that you can put all over the place – so it would be fine for cocoa farmers or olive growers, for example.
"It's not big, shiny steel stuff – the units cost a few thousand pounds or less, and it's lower-temperature technology that is cleaner and much easier for a farmer to operate. You don't need a degree in engineering to keep it from exploding or catching fire. So that's why we've chosen this route."
Later in the day I see the rough-and-ready reality for myself at the kiln that Sams and Morrell have built in a clearing near the former's smallholding on the outskirts of Hastings. An unprepossessing brick structure chugging out steam, it certainly doesn't look like the future of Earth might depend upon it, but it's here that two of Sams' employees have been gathering data and perfecting the efficiency of the technique.
We return reeking of smoke and I can see why Fairley has chosen not to get involved in Carbon Gold, concentrating instead on her latest books – a re-edition of The Green Beauty Bible and a new title called Beauty Steals.
"It's man make fire," she laughs. "I think it is a brilliant idea, it's genius, and it is weird having Craig do something that I am not involved in, but in this case I really don't think I bring anything to the party. Except maybe a damp rag."
Sams has no such reservations as he proudly scoops up handfuls of the fine black powder for me to inspect. The previous weekend his charcoal even took centre stage at a dinner party as the special ingredient – replacing squid ink in a risotto nero.
Sams and Morrell are now pinning their hopes on December's UN climate talks in Copenhagen, which will determine whether biochar is officially recognised as a way of cutting carbon emissions under the Kyoto protocol's Clean Development Mechanism. If so, it will eventually lead to its qualification for carbon credits, as part of a global carbon-trading scheme that allows countries such as the UK to sponsor carbon-reduction schemes to offset their own emissions.
Although Sams is confident that the Carbon Gold business model stands up on its agricultural value as a fertiliser alone, biochar's inclusion in the carbon- trading scheme would be a huge economic incentive for farmers around the globe to adopt it along with other organic practices. It's a move that Sams considers essential in battling climate change. "The biggest single cost of industrial farming is its contribution to global warming, and up until 1980, half of all greenhouse-gas emissions came from agriculture. Since then they have gone up; it's just that industrial emissions have gone up faster [which is why the focus of the world's media has been there]."
Biochar is not without its critics, however. Nick Rau, an energy campaigner at Friends of the Earth, tells me that "although there is potential there, we are advising an approach of absolute caution in the face of what might be another fake solution, of the sort we've seen with biofuels".
The two main problems as Rau sees it are a lack of long-term research into the area and, as in the case of biofuels, the possibility that commercial interests might lead to vast areas of land being given over to cultivating dedicated crops for the production of biochar, threatening food production and access for indigenous peoples.
Sams, who has long been staunchly opposed to bio- fuels, rules out the possibility of dedicated biomass cultivation. "The potential to do that is there, but we're nervous about it," he says. "If you start driving people off the land to produce super-fast-growing bamboo for biochar, it all becomes very counter-productive. And our crunching of the numbers shows that at that sort of scale you need a disproportionately high capital investment."
He admits that research is still in its early stages, but points out that from Iowa to New South Wales, "any university that has an agriculture department is now working within its area on applications of biochar for agriculture". Carbon Gold itself already has two projects under way – one at Sams' kiln and the other in Belize – and two weeks ago 12 PhD students began work on biochar-related subjects at the University of Edinburgh's UK Biochar Research Centre.
Of course, a little controversy should hold no fear for a man whose attempts to popularise healthy, sustainable eating were initially met with a Reader's Digest cover that screamed, "The Hippie Diet That's Killing Our Kids".
"Everything I have ever done has had an element of controversy about it," reflects Sams sanguinely. "You weather that kind of criticism. Gandhi said that when you come up with a new idea first they ignore you, then they laugh at you, then they abuse you, and then they do what you are doing."
In 2005 Sams sold Green & Black's, somewhat controversially, to confectionery giant Cadbury for a reported £20m. I ask whether the decision to sell the company felt contentious in a slightly different way, since it was a move perceived by some as a surrender to the status quo rather than a break away from it – and whether he feels that his credibility has since suffered as a result.
"Oh, I'm sure it did. You know, capitalist, sold-out, millionaire – I have had the word 'millionaire' used as an epithet now a couple of times. It's as relevant as blonde or dyslexic, but it is somehow acceptable.
"When we sold to Cadbury, the happiest people were our cocoa farmers because they'd had this relationship with a company who they knew had had shaky times and now they were in bed with the world's biggest confectionery company, who had agreed to honour all our agreements and could do so in a much more precise, professional way.
"That was my emotional satisfaction if you like, not the fact that we were an upstart company kicking Cadbury in the shins – although I guess there was an element of that. You engage with the world, and if you don't, you marginalise yourself, which satisfies the people who want to see you marginalised."
It is the same philosophy which underpins Sams' belief that the popularisation – for which he is partly responsible – of organic and Fair Trade products as a kind of trendy, bourgeois lifestyle accessory is a positive development rather than a frivolous distraction from a serious issue.
"If somebody buys a bar of Green & Black's because it tastes good or because they want to flash it at a dinner party, that's fine. At the end of the day, as long as the product is authentic, the benefits find their way through to the producers and the environment. Lots of things that are groovy are also extravagant and unnecessary, and I would rather people got their self-esteem from shopping at Daylesford and Whole Foods than buying a Ferrari.
"Softly softly, catchee monkey. Every little incremental lifestyle change makes a difference. It's like the idea of meat-free Mondays – you can't exhort people to make a complete lifestyle change over night, but once they realise, 'Hey, it's Tuesday and I'm still alive,' it's not such a challenge after all."
The small changes make a big difference for Sams, but with Carbon Gold, the possibility of solving the planet's greatest problems begins on an infinitesimal scale. Listening to him wax lyrical about the evolution of soil funghi and bacteria that he has been learning about in his biochar research, it's as gripping as if he were imparting the secrets of the universe. Probably because that is exactly how he sees it.
"Kenneth Williams once played a gardener in a radio comedy series whose response to everything was, 'The answer lies in the soil.' But if you really drill into it and ask 'The answer to what question?', then that question is, 'What is the meaning of life?' It's not like people haven't understood bits of it already, but now that I am into it, it's as exciting to me as discovering the new world was for Christopher Columbus."
In the excitement stakes, charcoal and soil might not be up there with chocolate, afghan coats or even brown rice, but if Craig Sams finds them thrilling now, it might not be too long before the rest of us discover a similar fascination.
'The Story of Green & Blacks: How Two Entrepreneurs Turned an Ethical Idea into a Business Success', by Craig Sams and Josephine Fairley, is published by Random House at £8.99