In the wilderness of the dusty, gently undulating hills in Oaxaca, Mexico, rows and rows of blue-green agave plants appear to march militantly into the horizon, their spikes stretching up towards the bright sun like grasping fingers. Here, in a field just outside Santiago Matatlan – a village about an hour's drive from the brightly painted buildings of Oaxaca City – I'm seeing the incredible plants that are used to make mezcal, the mysterious Mexican spirit that's currently driving drinks aficionados to the point of obsession.

En route, I whizzed down the highway, past hundreds of signs offering mezcal tours and the chance to try, in situ, mezcal made at one of the roadside palenques. Mezcal tourism in Oaxaca is booming and I've become one of its tourists, determined to uncover the spirit's secrets. And, I learn, it all starts with the agave.

"Before it's used to make mezcal, the agave plant matures for around seven years, depending on the species," mezcal producer, or palenquero, Carlos Mendez Blas tells me.

Like most palenqueros, Blas and his family have been producing mezcal for generations, with few adjustments to the process. Once mature, the agaves are harvested by hand, the spikes (pencas) cut off to leave just the pineapple-shaped heart, or piña, which is then taken to the palenque (distillery) to be turned into mezcal.

mezcal is a mysterious mexican spirit made from the agave plant

Visiting the palenque during the harvest, I see piñas cooking in an enormous rock-lined oven in the ground – which takes from three days, depending on the palenque's recipe – before being chopped by hand with machetes (with the result that many mezcaleros are missing a finger), then being crushed under a one-tonne rock called a tahona that's pulled around by a horse, donkey, bull or tractor.

After eight hours of crushing, the mashed agave hearts and the juices are transferred to a wooden fermenting tank, ambient-temperature water is added, and the mixture is fermented for about five days, depending on the time of year, and then the liquid goes through an alembic still.

Botanicals can be added; some traditional mezcals are distilled with turkey breasts. The fermentation and distillation vessels vary from palenque to palenque, too – distillation can take place in anything from copper to clay, while some producers even ferment their agave in cow hide.

This process is where mezcal differs to tequila. Confusingly, the term 'mezcal' can broadly be used to refer to any agave spirit, so it covers tequila, mezcal and more – and mezcal sits in its own category under the same name, just to make things complicated.

While both tequila and mezcal are made with agave, tequila is made solely using the blue Weber agave, is now largely industrially made, and the agave hearts are cooked in diffusers and pressure cookers (although a select few still use brick ovens).

Quiquiriqui mezcal and espadin agave

Agave fields outside Santiago Matatalan
Quiquiriqui's mezcal

In contrast, mezcal is made from any agave wild or cultivated, it's 100% agave (whereas tequila regulations allow the spirit to be made with only 51% agave, which means 'tequila' can be stated on the label of a bottle that's made from up to 49% different sugars, although they will be marked as 'mixto'.)

As far as processes go, the production of mezcal in Oaxaca is mostly as traditional as it comes. For now. As the consumer appetite for this magical spirit increases, the industry in its current form is under threat, and many mezcal acolytes fear it could go down the route of tequila.

Take, for example, the ordered lines of the agave field: many mezcaleros are still making their mezcal with wild agave that they find in Oaxaca's arid landscapes; in the history of mezcal, the cultivation of agave – and all the associated sustainability issues – is relatively recent.

A bluffer’s guide to mezcal

Five varieties of the agave plant

Oaxaca is one of the most biodiverse regions in the world. This means it's also home to hundreds of species of agave, which is why it's become known as the home of mezcal.

Espadin

The agave most commonly used to make mezcal. It matures in eight years and gives the highest yield.

Tepaztate

This agave takes a mere 30 years to mature – resulting in an intensely flavourful, aromatic mezcal and making it understandably popular.

Tobaziche

Often harvested wild, Tobaziche gives mezcal a herbaceous, savoury flavour.

Tobala

This tricky-to-grow wild agave produces a highly coveted mezcal that has a complex, fruity flavour.

Arroqueno

Taking 20 years or more to mature, Arroqueno yields mezcal with a slightly bitter, almost chocolatey taste.

Most mezcaleros are producing tiny batch, non-certified mezcals with unique characters and flavours that they just sell in their villages using the same processes as their family has for hundreds of years. It's these traditionally made mezcals that are enchanting bartenders and drinkers in London and beyond.

"Every single bottle of mezcal is different and totally unique, which I think is one of the reasons I find it so amazing," says Thea Cumming, who owns Dangerous Don coffee mezcal and, along with fellow mezcal brand owner and lover Melanie Symonds, is behind London Mezcal Week, which takes place this year from 10-16 September at TT Liquor on Kingsland Road.

"Unlike other spirits, the aging process happens when the plant is growing [that said, mezcal can be aged in oak barrels – reposado has been rested for between two months and a year, and anejo is matured for one to three years – but purists prefer to drink it joven, or young]. Most agave plants are ready after around eight years – you're drinking something which has matured and has personality and a story to tell."

"Mezcal is more than just another drink," says Jon Darby, founder of mezcal bar Sin Gusano, which also runs a mezcal masterclass under the name Mas (Mezcal Appreciation Society, but also, handily, the Spanish word for more)."There are so many elements associated with its production; it's a window into a different society."

Currently in residence at Curio Cabal on Kingsland Road, Sin Gusano is part business, part passion project, part social enterprise. Darby wants to teach people about good mezcal, and focuses on buying small amounts of traditionally made mezcals at local prices, importing tiny batches. The project has committed 5% of profits from this trading activity to sustainable growth programs and charitable causes in Oaxaca.

But, aside from flavour, perhaps mezcal's most entrancing quality is the chance to build an industry that's sustainable for both the local communities and the environment.

Big brands have been coming to Oaxaca, buying land and building industrial mezcal plants, or taking over smaller palenques and asking them to change practises to meet demand. And, unsurprisingly in such a poor region, many mezcaleros take them up on the offer in order to make money to feed their families. When palenques convert to these industrial processes, much of the tradition is lost.

"Traditional mezcal production is sustainable – more out of economic necessity and ingenuity than by design," says Alvin Starkman, who runs Mezcal Educational Tours. Starkman, a former litigator in Toronto, initially discovered mezcal in the 1990s, eventually moving to Oaxaca and setting up his tour business. Since then, he's developed relationships with 80 or 90 mezcal producers, and what he doesn't know about the spirit isn't worth knowing.

He offers several reasons why traditionally made mezcal is as sustainable an industry as they come: "Mezcal made with wild agave is the most highly coveted, which has sparked concerns that in a few decades there'll be none left. Some brand owners run an annual program in which small agave are planted and left to mature, and some communities only permit residents to harvest wild agave from communal land if the palenquero agrees to plant two small agave for every mature one harvested."

Elsewhere, weeding isn't necessary as infestations are rare. Sometimes agave will have something called 'the worm' or the gusano, which is a larvae that lives in the plant. But even that has its uses: it can be used to make worm salt, which is often used as a chaser; it can be put in the mezcal bottle as a marketing tool; and dried and salted gusanos are also often eaten as a snack.

Even the unused parts of the agave continue to play a crucial role in the lives of many Mexicans. When piñas are harvested to be transformed into mezcal, the leaves are typically left in the field, and are harvested once they begin to dry, usually by residents of nearby villages to use as firewood, to fuel pottery kilns and to cook a broad array of foodstuffs. The tall flower stalk (quiote) that shoots up at maturity is also used for firewood, in addition to being employed as a building material, and the fibrous agave leaves are used to make rope, clothing, grain sacks, horse bridles, and thread.

Mezcal made with wild agave is the most coveted

"Those making mezcal in an artisanal way adhere to the ethos of 'permaculture' as much as you'll find in Mexico," says Starkman. "For me, permaculture is the weaving together of what nature can provide in a microclimate, with material goods and human needs and aspirations, in an ethical manner that sustains the complete system."

There are, of course, other issues associated with the production of the spirit: "The overuse of wood [a precious resource in Oaxaca], harmful waste products and water waste can make the process unsustainable," says Cumming. "But if these processes are addressed and brand owners work with their producers towards more responsible methods of practice, there's a way to make the process more sustainable."

"We only use wood that is diseased or has fallen in our palenque and plant a higher ratio of agave than we use," says Symonds, who produces Quiquiriqui mezcal with Blas and several other small producers whose palenque and agave fields I visit.

"We also dispose of our waste responsibly. We're lucky to be able to do these things to reduce our impact on the environment. And by employing local people in the palenque, we also feel we're working as sustainably or responsibly as we can while protecting traditional production methods – which, ultimately, we think makes a better mezcal."

Inside a traditional palenque – in pictures:

It's preserving the traditions that is of utmost importance for responsible producers and importers. "What larger companies don't do is support small producers or work towards the preservation of traditional methods, but what they're much better at doing is dealing with issues like waste management because they have the money and the resource to do so," continues Cumming.

"The dream scenario is that traditional methods are preserved, producers are supported, treated fairly and paid properly; brands consider ways to integrate into the local communities; and more responsible production methods as well as agave regrowth programmes are put into place."

Sadly this isn't always the case. "There's choice of industrialising to meet demand – having stainless steel column stills, machinery to crush and adding chemicals to speed up fermentation. Some brands go in that direction; they industrialise and lose quality," says Starkman. "I have a friend whose family has been in the business since the 1800s. When we became friends 25 years ago, he produced great mezcal. He started producing for an export brand, it became successful, and the quality of his mezcal suffered."

Many ardent supporters of mezcal are adamant that industrially produced product isn't really mezcal. "That's not the way of mezcal," León Lory Langle, bartender and long-time supporter of traditional mezcal producers, tells me over the boom of live music in Oaxaca City's Txalaparta Bar. "Right now, I feel like we're losing the unique production. Importers only care about how many litres of mezcal they need to supply the world. They have a different vision."

Our five favourite responsibly produced mezcals

Quiquiriqui

Quiquiriqui's mezcals are all single estate – or palenque – handmade in Mexico. Brand owner Melanie Symonds partners with families who have been producing mezcal in their communities for generations, creating small-batch mezcals with locally grown agaves. The brand's wild tobola mezcal has a limited run to protect the wild agave population.

From £36.34; masterofmalt.com

Dangerous Don

Mexico is known for, amongst other things, mezcal and coffee, which is why this serve makes perfect sense. The NaomQuie coffee used to make the spirit is grown using natural methods and the mezcal itself is distilled using traditional techniques. Drink it on its own... Or in a kick-ass espresso martini.

£51; masterofmalt.com

Papadiablo

Made with espadin and three wild agaves – madrecuishe, bicuishe and mezicano – Papadiablo (which means Pope Devil) is a complex, traditionally made mezcal. All the ingredients are organic, no chemicals are added and the brand also distill to proof – which means no water is added to adjust the ABV. 

£73.95; thewhiskyexchange.com

Estancia Raicilla

Raicilla means 'small root', and is another spirit distilled from the agave plant, with a more fragrant and fruity taste than tequila and mezcal. Estancia's raicilla is distilled to the highest standards in the highlands of the Sierra Madre Occidental mountain range.

£64.20; amathusdrinks.com

Vago

Mezcal Vago specialises in seeking out small-batch mezcaleros in the Oaxacan hills, and helping them to preserve and develop their craft. The brand respects each mezcalero's traditions, and never asks them to change their production methods in order to expand. 

mezcalvago.com

"There are a lot of businessmen in mezcal right now, because it's an opportunity to make fast money. But they're destroying the tradition," Leon continues passionately. Back in London, at one of Sin Gusano's Mas nights, Darby agrees. "Mezcal production can't grow at an exponential rate and maintain interest."

That said, Starkman suggests importers do have alternative options to meet demand. "A brand called Vago started less than five years ago and became very successful. They had two people producing for them. Eventually they couldn't meet demand, and had the choice of industrialising production; hiring more people from outside their family to help them produce this mezcal; or, the route they went down, finding two more producers in other villages who were making mezcal with the nuances and quality they like. That's the way to maintain the quality of product."

Everyone I speak to – Mexican or UK-based; bartender, producer, importer or tour guide – is utterly in love with the stuff. They're passionate about preserving mezcal's traditions and safeguarding local communities, as well as using production methods that treat the environment with respect.

"Right now, we've still got a real chance to influence the industry by guiding consumers to make the right decisions," says Darby, which is one of the reasons he ended up setting up Sin Gusano and the Mas evenings.

"Tequila became dominated by a few huge brands producing industrial, substandard products, and doing it so cheaply that buyers' heads were turned," says Quiquiriqui's Symonds.

"The mezcal industry has changed dramatically in the seven years since I started, and you just need to look at tequila to see where we're currently headed."

With this in mind, what should you be looking for when buying mezcal? Labels should provide as much information as possible – style of distillation, village it's from, name of the mezcalero, species of agave – and it should always say 'artesenal' or 'ancestral', which indicates the spirit will be more traditionally produced and you'll be supporting a smaller mezcalero. If it just reads mezcal it might not be produced in a traditional method and be blended with unknown agaves from unknown regions.

By following these guidelines, says Dangerous Don's Cumming, you're much more likely to find a "true representation of the magic of mezcal" – just don't blame us if you fall under its spell.

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