Bertha was his £22,000 learning curve. These days she mostly sits there humming. In the two years since Douglas McMaster captured the restaurant world’s imagination with his zero-waste idea, the chef has outgrown Bertha, his monster composter, and is looking to London for his next project.

“When we opened, I thought it was like a spinning top. This could go in any direction,” McMaster says sitting on a chair in an interview room in Galway after his talk at this year’s Food on the Edge.

In the end it went big. A media storm broke over Silo in Brighton, and it took off with “people from all over the world flying over and being part of it. It was amazing,” he says.

Isn’t that ironic for a restaurant whose heart beats deep green? McMaster laughs. “There are lots of ironies in my little world.”

The biggest of those is Bertha: “It’s all-singing, all-dancing, hugely innovative and it’s the way in which zero waste is possible . . . in an urban environment. That’s such a brilliant, special thing. The irony is we don’t really use it.”

McMaster isn’t quietly landfilling food waste. Instead, he thinks in circles about every ingredient so that virtually everything ends up on the plate. And not everyone is thrilled about it.

Recently they served wild chickens from a park where longhorn cattle, Tamworth pigs, deer and chickens are left to roam and forage for themselves.

“We had a dish of different alliums, roasted red onions and chives and roast garlic, and had a chicken skin crumble, a really simple, small, delicious dish. And then for the next dish we made a Bolognese out of the leg meat, confited and chopped with loads of lemon thyme and served it with a very savoury quince and lovage,” McMaster says.

“The third dish was poached breast, so we had three different dishes from one animal that is super environmentally sound. If this was a traditional restaurant, they would be getting three different dead animals to do three different meat dishes.”

Omnivorous dishes

Silo throws a spanner in the machine of people’s expectations of a restaurant, he says.

“Commercially it’s not fun. There are people who get it. They come in knowing what it’s about and that they’ll get chicken on three omnivorous dishes. And then there are customers that don’t and come in and give us one star on TripAdvisor,” he says.

McMaster definitely wants to take a zero-waste restaurant to London but it won’t be like Silo, with its upcycled chic.

“I don’t have the money for it yet. I’ve only really started thinking about it. I’m really fascinated with ‘built to last’. Everything, or 99 per cent of everything, is built to die, not to last, and I’m really interested in designers who are building things to last, whether it be chairs, phones, lightbulbs, whatever,” he says.

“I would like to have a restaurant where every single material choice was thought out in a way that it was almost going to last forever. And if it doesn’t last forever, then it’s good for the Earth somehow.”

The food in any London venture will also be high end. “I spent 14 years in some of the best restaurants in the world, [Fergus Henderson’s St John and Noma in Copenhagen among them] just working my arse off, so that’s what I’m good at. Some of the more extreme ideas going on is where I want to push it.”

That means tapping into food resources that are untapped, McMaster says, things such as “Japanese knotweed and cray fish and tilapia that no one else commercially demands, looking at the big organic productions and seeing what is waste”. This would include the 80 per cent of cacao discarded in a bean-to-bar chocolate operation or the whey from a raw cheese-maker.

What does he think of the extreme examples of waste in restaurants, such as the Fat Duck binning plates ready to go to a table if they sit for longer than 90 seconds?

“Unfortunately it’s that word ‘perfection’. We have unrealistic delusions of perfection. There’s no such thing as perfection and there never will be. I like to work to a different standard. My standard is brilliant,” McMaster says.

“That idea of perfection is so unnatural and it breeds unnatural behaviour, how the media projects perfection and how it makes everyone so sad inside. It’s unnatural, that whole idea of pure perfection. So brilliant is enough.”

And brilliance means making puritanism pleasurable, he says. “Taking that idea and blowing it up into a beautiful tasting menu, blowing people away with what’s possible if you use your imagination. So, yeah, that’s what I would like the next restaurant to be: a proper, world-class tour de force in zero waste.”