At the headquarters of Energy Control in Barcelona, Northern Spain, a nondescript envelope arrives. Hidden inside, between layers of cardboard and tape, are two fluorescent pink pills purchased from one of many eBay-style marketplaces on the dark web.

For €50-worth of bitcoin, the non-profit provides anyone in the world with a breakdown of the substances contained in their drugs – and the quantity – no questions asked.

Energy Control has been carrying out drug checking in raves and at its labs since 1998. Its dark web service, introduced in April 2014, operates under the same premise: to reduce harm among users by arming them with facts.

The idea for the project can be traced back to a family physician named Fernando Caudevilla, commonly known as Dr X. Following his first post to the Silk Road forum in April 2013, six months before the market's FBI shutdown, he became a trusted source of guidance on drug safety across many dark markets.

Up until this point, Energy Control, which is over 90% government funded, had only offered services inside Spain. However, Caudevilla – who has worked with the organisation since 2000 – saw the potential for a drug checking service for the dark web – completely anonymous, of course.

Mireia Ventura, Energy Control's drug checking co-ordinator, who took over the project now Caudevilla has moved up the ranks of the organisation, explained:

While there are other harm reduction projects, such as Wedinos in Wales and DanceSafe's DIY testing kits, nothing matches the scale and speed of Energy Control – which aims to return users' results in seven to ten days.

Ventura says her lab receives between five and 10 deliveries a week from drug users as far afield as Australia, China and the US.

The service doesn't come cheap. Ventura's lab was gifted its first machine – a liquid chromatograph – by a donor. However, it is still paying off the high-spec gas chromatograph it bought specifically for its international testing. Ventura estimates this may take up to six years.

Timing is also crucial. While samples may only take 30 minutes to process on average, there is often a large backlog – with the machine running non-stop Monday evening to Sunday evening.

"Depending on the substance, you need to do further analysis. For example, for LSD it is necessary to use liquid chromatography to quantify the exact amount of LSD," Ventura said.

The backlog is also due to the rising number of new substances the lab is seeing, last year 266 samples it processed were found to be new psychoactive substances, also known as 'legal highs'.

Delays also mean people are more likely to take risks, which is an added problem with the influx of new adulterants, such as the anaesthetic metoxetamine, and entirely new substances – such as 'date rape' drug Scopolamine – the lab is seeing.

Energy Control does accept funds via bank transfer and PayPal, however national coordinator Núria Calzada said bitcoin – the de facto currency of the dark web – is by far the most popular payment method for its privacy-conscious users.

Since its inception in April 2014, the project's bitcoin proceeds haven't moved from the Blockchain wallet owned by Energy Control.

The notoriously volatile currency that it is, bitcoin has halved in value within that time.

It's not that Energy Control doesn't want to access the funds, Calzada said, but the regulatory uncertainty around bitcoin is a "headache" for its parent organisation, ABD, which values transparency above all else.

Calzada said Energy Control was likely the first NGO is Spain to use the cryptocurrency, with another "to do with kids and clowns" also in the mix.

Spain has issued little official guidance on cyptocurrencies such as bitcoin to date, which means handling the cryptocurrency in a business capacity requires a lot of guesswork on issues such as VAT.

Despite bitcoin's grey area, Ventura said the project has strong ties with the government, acting as eyes on the ground for the Ministry of Health and further up the chain in Europe.

"The thing is that we have their respect and we are really very important for them for identifying all the new substances and all the new trends," she said.

The service is vital to check not only the kinds of adulterants present in the sample but also the dosage of the drugs.

Just as strains of marijuana have been getting progressively stronger, the EMCDDA and Europol have issued an alert warning of health risks linked to the consumption of very high-purity MDMA products.

In Energy Control's 2014 annual report, released this month, the organisation revealed the three most common street drugs, MDMA, speed and cocaine, were at their highest purity in the last five years.

In fact, 84% of the MDMA samples the lab received were pure crystal. This, Calzada told a press conference, could be a result of the eBay-style seller ratings on the Deep Web, where sellers face public scores on their quality and service.

Ventura said:

"In the street level there are a lot of hands moving that cocaine so it's easier to polute and add other substances," she added.

Professor Fiona Measham, an expert in UK drug trends, told the Guardian last year she had witnessed nine MDMA-related cardiac arrests at one festival alone due to the strength of the drug.

Due to the small sample size Energy Control takes – between 30 and 100mg – it is not always possible to detect all substances that might be present in the larger batch that particular sample came from. Ventura said:

"We advise that this is a validation of this sample and not the validation of the dealer that sells this sample. We certificate sample to sample, not a batch or vendor," she added.

But are sellers using this purity rating as a stamp of approval from the lab? Nathan Jessop, an analyst at Elliptic who specialises in dark markets, said in his experience this isn't a standard practise:

Alongside feedback ratings, sellers are far more likely to promote their products via reviews on the so-called 'clearnet' via forums such as Reddit, he said.

Affiliate marketing – a term to describe customer referral schemes – and banner ads are also in play on sites like Grams, the 'Google' of the dark net.

"If vendors are using our service ... they are not in our target group but we think that there is a type of risk reduction. But we don't want them to use our name as validation," Ventura said.

Since Silk Road, the dark web – accessible via anonymous browser Tor – has been populated by marketplaces offering a smorgasbord of drugs in exchange for bitcoin. Statistics suggest they are both bigger and bolder since Silk Road's demise.

Academics

have made the case that, by reducing the amount of face-to-face interaction down the supply chain, dark web marketplaces have reduced drug-related violence, for example territorial disputes between low-level dealers.

The judge in Ross Ulbricht’s trial, Katherine Forrest, dismissed this as an argument of privilege, describing the site and Caudevilla's role in it as "breathtakingly irresponsible".

Families of two young men who died after ingesting substances from the marketplace, including Australian Preston Bridge, testified to Forrest that Ulbricht should be held responsible for their deaths.

"Ulbricht’s plan was not simply a plot to disintermediate local drug dealers. It was Ross Ulbricht’s plan to rapidly expand the market for illicit drugs, and in the process, dramatically enrich himself without any regard for the lives of others," wrote the father of ‘Brian B’, a 25-year-old who died after overdosing on Silk Road heroin.

Forrest would later hand down a sentence of life in prison.

While some argue the best way of avoiding the fate of Bridge and Brian B is to steer clear of drugs altogether, the people behind Energy Control realise not everyone will do so. There will always be people who want to take drugs, and Energy Control seeks to make it that little bit safer for those who do.

All images © Alex Verdaguer/Energy Control