It started, as so many things do these days, with a YouTube video: one shot on a phone camera by two marine biologists who were undertaking a routine operation. A sea turtle has something – "A hook worm? A tape worm?" – stuck up its nose and, pliers in one hand, phone in the other, the pair are attempting to wrestle it out.

The turtle starts sneezing. It's adorable and cute, and for a moment you think it's just going to be all Vets in Practice – but this time with sea creatures!

Then the turtle starts bleeding. The blockage proves longer and longer, and what the biologists thought would be a quick and easy worming turns into the extraction a 10cm plastic straw.

Yes, a straw. One of those things you casually stick in your G&T or in the top of a Coke bottle because your teeth are a bit sensitive.

I'll spare you the gory details – you might be eating – but suffice to say that by the end of it, the air was blue with the curses of the biologists, and the counter ran red with blood. Within days, the clip had gone viral, sparking much sadness and anger at the reckless way in which the restaurant and bar industry uses and dispose of these small, destructive and – let's face it – essentially pretty unnecessary pieces of plastic. Yet while many restaurant groups turned a blind eye and carried on sucking, the Hertfordshire-based pub chain Oakman Inns saw it as a call to arms.

"Overnight, they decided to ban their use of them," says Tom Tanner of the Sustainable Restaurant Association: a small but influential player in what is, slowly, becoming an enlightened industry.

Oakman wasn't the only one to pull the plug on plastic straws – The Breakfast Club, Hawksmoor, MEATliquor and others have followed suit – but they were the most cutthroat: immediately cancelling all future orders, and creating a sculpture out of the melted-down remainder of their supply. These days, it's par for the course for restaurants to make a song and dance about the free-range, organic and homegrown credentials of their food, if they have them.

The scandal of the straws is a prime example of the less 'sexy' aspects of sustainability going largely unnoticed: not because customers don't care, but because without furrowing about in the deep end of a restaurant's website, it is surprisingly difficult to distinguish how sustainable your meal is beyond what you see on the menu and the chalk writing on the wall.

Of course, as the very existence of the Sustainable Restaurant Association indicates, there is more to sustainability than sourcing.

Established in 2010, it has an extensive framework that covers issues of society and the environment, as well as produce. Each month the Association focuses on a different aspect, from community engagement to healthy eating, treatment of staff to waste.

It's not as tasty as talking about pole and line caught tuna seared and served on a bed of homegrown cucumber relish, true: but there is a growing sense that to worry about your tuna while pumping out copious carbon dioxide is, to some extent, fiddling while the world burns.

"We need to look at the industry as a whole," reiterates Tanner, citing Wahaca as a prime example of a place whose comprehensive action (which includes smart kitchen equipment, recycled materials, carbon offsetting and recycling) has become a model of sustainability. In March last year, Wahaca was the first restaurant group in the UK to become carbon-neutral. For so-called chains, whose eco-credentials have historically been found wanting, Wahaca's co-founder Mark Selby is considered very much a pioneer.

"They are a double act," Tanner says of Selby and Wahaca's better-known other half, chef Thomasina Miers. "Thomasina's the foodie side, whereas Mark is passionate about what happens behind the scenes."

We don't want to shove our sustainability down people's throats

When I catch Selby early one morning in a week choc-full of meetings and site visits, this passion is tangible – more tangible, in fact, than it is in the restaurants themselves. "We have info on our website," he says, "and there's a bit on our menus – but there are only so many messages you can send out to people. We don't want to shove our sustainability down people's throats."

Wahaca is not Pret, whose posters shout loudly and proudly about the various ways they go about reducing their environmental impact. "It's a different atmosphere. Customers are not grabbing a sandwich: they come to spend time here, for great food and a great vibe."

The motives behind Wahaca's methods – the LED lighting, paint that's low in particulate pollutants, the recycling of heat from the back of the fridges and freezers into heating water – come more from inside the company than outside it. "Principally, we do it because we believe in it. We have always cared about our impact on the planet." Some customers are very interested; many aren't, he continues – "but whatever we do at Wahaca, we have to do it with integrity, because we really care."

It is not, therefore, a marketing ploy. Nor is it a money-spinner – though there are energy savings to be made through LED lighting and motion sensors on lights and fans. "With each new site we complete a 'Ska Retail environmental assessment'" – a framework where they identify reusable materials, specify materials with high recycled content, install energy-efficient equipment and water-efficient taps – "and use builders and designers who are trained in environmental quality," says Selby. It costs more and it's complicated, "but that is no excuse if you believe in it."

One of my favourite Wahacas, in Soho, is in a former dance studio, and the gleaming wooden strips on the wall are repurposed from the floor. My assumption – one which many readers will share – is that restaurant chains sell out on things like sustainability and wages in the quest for expansion. Selby's mission is to prove to customers and to his fellow restaurant group owners that this doesn't have to be the case.

Of course, small restaurants are more agile. In a bid to curb his carbon footprint and support British craftsmanship, Mathew Carver sourced cutlery from Sheffield, furniture from Canterbury, and crockery from Stoke-on-Trent for his Cheese Bar in Camden.

While the scale of Wahaca's demand renders such reliance on small-scale suppliers unfeasible, for Carver it was a no brainer: "We source artisanal British cheese. Why not put the same consideration into furniture and tablewear?"

At Long Arm Pub, a new boozer and brewery in Shoreditch, they have completely removed the packaging process so beers are fresh from the tanks in the room to the glass.

"You don't find Tank Fresh beer everywhere because the majority of brewers don't have the scientific knowledge to carry the process through and scientists don't have the brewing background," says creator Guillarmo, third generation brewer and chemical engineer. It's the 'booze-on-tap' concept – an idea popularised by Sourced Market and Vinoteca, and extremely effective at cutting down packaging – taken to the next level: plans are also afoot for an aquaponics farm at Long Arm, whereby the fish are fed with the spent grains from the brewing process.

Size matters when it comes to sustainability: Switzerland can recycle as much it likes, but it's the States we really need on the bandwagon – yet there is a ferment, if you'll excuse the pun, among the little guys who are coming up with imaginative solutions to waste and inefficiency.

Hawksmoor cannot possibly commit to composting all their waste on site – "each restaurant would require an entire floor," says Emmy van Beek, the group's sustainability manager. But they are full of admiration for those restaurateurs – Doug McMaster in Brighton, Tom Hunt in Bristol – who are.

Ultimately some things need size. Smart technology, and the sort of big pay packets and in-house career progression that encourages staff retention are features only money can buy, and that invariably means restaurant groups. Wahaca and Hawksmoor take pride in their smart fans and fridges, and in the wages and training their employees receive.

"We pay vocational wages: on a level of a teacher if you're a head waiter, on the level of a headmaster if you're a head chef," says the co-founder of Hawksmoor, Will Beckett. "From the first hour of the first day of your induction, we're talking about how you can work your way up – or if you don't want to work up, about how you can be the best waiter or chef de partie."

Treating staff fairly is a key part of sustainable business

He's made it his mission to ensure that his staff stay at Hawksmoor – and if they leave, that they leave loving Hawksmoor. "It's well known as one of the best places to work in the industry," comments Tanner, who believes treating – and paying – staff fairly is a key part of being a sustainable business. "Before we opened Hawksmoor, we had the same problems everyone else complains of in the restaurants we started: a high turnover, staff treating their jobs as a stopgap and so on. With this we approached things differently," Beckett explains. "I actually started as a waitress, at the Guildhall branch seven years ago!" van Beek proudly tells me.

"They are our biggest concerns: our food, and our people," agrees Selby. "We've three head chefs now who we trained from nothing, who couldn't speak English. Now each one's in charge of a multi-million-pound restaurant." Small independents can't do that, he points out – yet as the Three Stags in Kennington demonstrates, you don't have to be big to make a difference.

Landlord Richard Bell is no chief executive officer: he's a yogi who spent almost a year living in Bali, and who, last year, made the news for installing the faces of the Republican presidential candidates in the toilets. Yet within a year of signing up for membership of the Sustainable Restaurant Association, he'd won three stars – their highest rating – for revamping his sourcing, recycling and energy supply.

Petersham Nurseries, meanwhile, send their used coffee grains to Biobean, who convert them to biofuel. "This high-performance winter fuel burns hotter and longer than wood and is proudly stocked in Petersham Nurseries' Garden Shop," says executive chef Damien Clisby. "They are sold to our customers and our recycled waste coffee grounds are given a useful second life."

As both Selby and Beckett are at pains to acknowledge, the sustainability of a restaurant largely boils down to the people involved, not their pockets.

"It was the bartenders who felt funny about their using plastic straws to taste cocktails: the chefs who wanted to cut down on refined sugars [unrefined sugar can be entirely produced where it's grown, meaning the value remains in the country of origin, with the communities that grow it, not a refinery]," says Beckett.

It's the last person to leave who, at the end of the evening, must remember to switch off all the electrics. There are ways to make sustainability easier for staff: van Beek introduces me to a last man out switch which turns off everything: "lights, computers, equipment – everything that doesn't need to be on, like the booking server" she says. "When you're leaving at 2am after a long shift the last thing you want to do is have to go round checking that the lights are off." Clearly labelling different recycling boxes (Wahaca has seven) and teaching kitchen staff how to minimize food waste gives meaning to the mantra 'every little helps.'

These practices aren't going to make the papers. No one will Instagram your compost bin. "There are those who will put what they do on their menus, I guess because it adds perceived value," says Carver – "but the reason I wanted to buy British furniture and crockery was for my own peace of mind."

The very nature of sustainability is that it is backstage

Even if customers care about the planet (and one hopes they do), they don't necessarily want to be force-fed all the various ways that a restaurant is being sustainable. "A lot of people when they go out to eat like to know these things are being taken care of. They don't necessarily want to tuck into sustainability measures with a knife and fork," says Tanner. There are ways to subtly indicate to customers that you're sustainable: straws are one, as is offering a doggy bag, having wines on tap and avoiding plastic bottles – but the very nature of sustainability is that it is backstage.

Perhaps that is a good thing. Last night I visited Cinnamon Soho's summer festival terrace, the brainchild of Vivek Singh and celebrated bartender Ryan Chetiyawardana, also known as Mr Lyan. "The sustainable al fresco terrace will feature a range of Mr Lyan 'Upcycled & Recycled' cocktails alongside a selection of Vivek's signature street food that will be served in recycled dishes to ensure that nothing goes to waste" proclaimed the press release.

"Re-using or upcycling an ingredient, or showcasing a nose-to-tail approach to processing something, opens up creativity and gives a delicious example of how we don't need to simply focus on 'prime cuts'. However, it's even better to go beyond this, and look at all the materials possible to reduce our impact while still having something wonderful," Mr Lyan tells me.

The place is utterly charming: a stretch of turf scattered with mismatching furniture, it's vintage style is so on trend, I forget it's about more than aesthetics. "Did you know this was an eco terrace?" I say to my companion. "Ah," he replies. "I wondered what the 'Watermelon Rind Tonic' was about." We order two. Of course, they arrive in milk bottles, but beyond that there's nothing odd about them. They taste – well, simply lovely.

"You wouldn't know," we remarked to each other, as we admired the coffee-jars-turned-flower-vases and repurposed bicycle wheels, and ordered a collins created with cordial made from discarded mint stems.

Compared with the sought-after Michelin star, one from the Sustainable Restaurant Association is unlikely ever to hold much cache – but you shouldn't have to shout about sustainability. It shouldn't have to be different or difficult. It's just what you do – or should do, in an ideal world – and proving that is what the finer parts of the food industry do best. I'm glad Wahaca sends its biological waste to an anaerobic digester for energy. I'm thrilled the Cinnamon restaurants are using filtered still and sparkling water systems to avoid using plastic bottles.

But I'm also glad I didn't know about it: that it's possible to eat at these restaurants without knowing that, and find them enjoyable. Because, ultimately, the more normal, easy and palatable that sustainability looks and feels on the outside, the more people are likely to adopt it themsevles – and the fewer bleeding, plastic-ridden sea creatures will end up suffering needlessly for our mass consumerism.

Discover more restaurants, cafés and bars using food for good.