EU Drug Market: Cannabis — Production

Producing cannabis and cannabis consumer products

This section provides an overview of cannabis cultivation and the production processes of the main consumer products that can be derived from the cannabis plant (see Figure Cannabis: Taxonomy of products traditional and modern), as well as some emerging semi-synthetic products (see Box Emergence of semi-synthetic cannabinoids: delta-8-THC, HHC and HHC-O)(¹).

Cannabis cultivation settings

In Europe and at the global level, illicit cannabis cultivation is performed in a variety of indoor and outdoor settings at different scales. Both indoor and outdoor illicit cannabis-growing operations range from, for example, a few plants cultivated at home for personal use to sites with thousands of plants controlled by criminal networks (see Box Indoor cannabis cultivation sites). The cannabis crop, typically the flowering tops of the plant, is then used to manufacture a range of consumer products (see Section Trends in European cannabis retail markets). In Europe, the most commonly available products have been herbal cannabis (interquartile range of national means: 7-13 % THC), cannabis resin (12-29 % THC) and to a lesser extent cannabis oil (10-60 % THC) (see Figure Cannabis: Taxonomy of products traditional and modern).

The potency and contents of cannabis products depend on the cannabis plants from which they are derived. For instance, the THC/CBD content of cannabis products is determined by the levels of these compounds found in the cannabis plants used to make them. In turn, the composition and levels of cannabinoids found in the cannabis plant depend on many factors. Factors include light exposure (natural or artificial), the type of seeds, and whether cuttings or clones are used. Furthermore, the method of cultivation, the number of plants per square metre, water supply and soil pH (which affects the availability of nutrients) may influence the yield of the cultivation site.

Outdoor cultivation can produce up to three harvests a year depending on the weather, the amount of light and the strain of cannabis used (EMCDDA and Europol, 2019). When growing cannabis outdoors, systems to control environmental conditions (e.g. lighting and heat sources) are typically not used. However, automatic watering systems or curtains for shading may occasionally be used, as is the case with certain homemade or portable greenhouse kits.

Indoor cultivation sites run by criminal networks operate in a variety of locations (see Box Indoor cannabis cultivation sites) and can be used to grow cannabis throughout the year, resulting in up to four to six full harvests annually (Vanhove et al., 2012a, 2012b) (see Figure Factors determining yield of indoor cannabis cultivation). Cultivation techniques used for indoor cultivation sites may differ significantly, which in turn influences yields and the number of harvests (Vanhove et al., 2023). Indoor cultivation sites run a lower risk of detection and generally produce higher yields and experience less spoilage due to adverse weather or pest infestation. Some high-potency strains can only be successfully cultivated indoors. However, the energy consumption of indoor cultivation sites is significantly higher than that of outdoor growing operations (see Box Criminal network steals EUR 1.5 million worth of electricity for industrial-scale cannabis cultivation in Spain). There is also an increased risk of fire, for instance due to defective electrical wiring, as well as other potential hazards related to exposure to mould and chemicals (see Section Environmental impact and hazards of cannabis cultivation).

 

Source: Vanhove et al., 2023

Cannabis biochemistry

Within the cannabis plant, complex biochemical processes lead to the production of a range of phytocannabinoids. A key process is the conversion of cannabigerolic acid (CBGA) to THC-acid (THCA) and CBD-acid (CBDA). On the US drug market, THCA is known as ‘crystal THC’, and it can be added to increase the potency of herbal cannabis (Cuadari et al., 2019). Some products available in Europe may also contain added THCA.

THCA in itself is not a psychoactive substance. However, it may be converted to delta-9-THC, the most commonly consumed psychoactive cannabinoid, or its isomer delta-8-THC (which can be oxidized to form cannabinol (CBN)). It can also be converted to cannabinolic acid (CBNA), which converts to CBN (see Figure Biosynthesis of selected cannabinoids in the cannabis plant). When natural cannabis products are smoked, the total amount of THC consumed is a combination of the THC and the THCA present in the plant since THCA is converted to THC when heated (the same situation arises with CBDA and CBD).

For consumption methods that do not involve heating, a further step in the process is introduced, known as ‘decarboxylation’, to increase the potency of the product.

Source: Desaulniers Brousseau et al. (2021).

Extracting resin from cannabis plants

The production of cannabis resin, or hashish, involves dislodging the glandular trichomes (which contain resinous secretions) that form mostly on the flowering tops (buds) of the cannabis plant, but also on the leaves. This results in a fine powder that is high in THC, which is subsequently compressed to form cannabis resin. Traditional methods of resin production include rubbing and sieving (EMCDDA, 2016). While the plant’s leaves are often discarded when producing herbal cannabis, they may be used for resin production. However, using just the flowers produces a higher potency end-product. In addition to traditional methods of resin production, commercial equipment is also used (for example, ‘Pollinators’). Certain techniques can be introduced to increase the potency of the final product, such as using ice water or dry ice which allows the trichomes to be removed more easily (EMCDDA, 2019a).

The removal of resinous secretions from the trichomes can also be performed more efficiently through other methods. These techniques have developed over the last decade, particularly in regions with licit cannabis markets, and can produce resin-derived products with extremely high concentrations of THC or CBD, reaching between 70 % and 90 % (Caulkins, et al., 2018) (see Figure Cannabis: Taxonomy of products traditional and modern).

Some of these processes, especially those using flammable gases such as butane or propane, are known to be hazardous and have led to accidental explosions in several European countries (EMCDDA and Europol, 2019). Various products can be manufactured, depending on the method and solvents used – such as: butane hash oil (BHO), a viscous liquid; ‘shatter’, which is hard and brittle’; ‘wax’, which resembles a soft wax; and ‘crumble’, which is soft and flaky. ‘Rosin’ is another extract made by heating and applying pressure. The aforementioned cannabis extract concentrates, which contain a very high proportion of THC (more than 90 % for some products), have appeared relatively recently on the European market and are frequently used in vaping and other devices (Meehan-Atrash and Rahman, 2021) (see Figure Cannabis: Taxonomy of products traditional and modern).

Herbal cannabis production outside the EU

Herbal cannabis is produced globally. Some of the herbal cannabis produced in the Americas, south-west Asia and West Africa is trafficked to Europe (EMCDDA and Europol, 2019). However, in recent years EU Member States have reported few large seizures of herbal cannabis shipments from these regions, and they are no longer reported as major source countries. Herbal cannabis is also trafficked to the EU from Canada and to some extent, the United States, and there are recent signals that these regions might become more prominent. While most cases involved small amounts in parcels, more recently, several shipments ranging from several hundred kilograms to a tonne, were seized at European ports arriving in containers coming from Canada (Openbaar Ministerie, 2023). It should also be noted that Morocco, the major source of cannabis resin available on the European market, has also recently been mentioned as a source of herbal cannabis by several EU Member States.

Meanwhile, the Western Balkan region has long been important in the supply of herbal cannabis to the EU market. Cannabis is cultivated both indoors and outdoors throughout the region. However, the period 2017-2021 was characterised by a sharp decrease in seizures of herbal cannabis. While more than 84 tonnes was seized at regional level in 2017, mostly in Albania, this amount decreased significantly to around 19.5 tonnes in 2019 and 14 tonnes in 2021 (see Figure Quantity of herbal cannabis seized in the Western Balkan region 2017-2021) (EMCDDA, 2022d).

This decline in seizures appear to have been influenced by a shift in cannabis cultivation in the Western Balkan region since 2016, with less cannabis being grown outdoors. This in turn seems to have been influenced by major eradication efforts in Albania, where operations have been undertaken in cooperation with the Italian Guardia di Finanza.

Overall, the situation has become more diverse and complex, with an increasing number of countries in the region reporting large-scale indoor cannabis cultivation sites, with some of the drug likely intended for export (see Box Industrial-scale cannabis cultivation in the Western Balkan region).

 

Source: EMCDDA, 2022d; Ministry of Interior of Montenegro, 2022. The source data for this graphic is available in the source table on this page.

Some of the cannabis produced for legal markets (e.g. for medical use) also appears to have ended up on the illicit market. North Macedonia legalised cannabis production for medical use in 2016. Between February 2017 and October 2021, 64 companies were granted licences to grow cannabis for medical use (Hall, 2021). Worryingly, there have been indications that cannabis legally produced in some of these sites may have been diverted to the illicit drug market in North Macedonia or smuggled to other countries (EMCDDA, 2022d). For example, in early December 2020, over 2 tonnes of cannabis were stolen from the warehouses of licensed North Macedonian companies in two separate incidents (Ministry of Interior of North Macedonia, 2020a, 2020b). There are also signs that illicit cannabis production may have been deliberately undertaken in licensed production facilities. For instance, in February 2022, North Macedonian police seized about 1.5 tonnes of undeclared cannabis from a legally registered grower (Trkanjec, 2022).

In June 2022, the Albanian government published for consultation a law regulating cannabis cultivation for medical and industrial purposes (Electronic Register Albania, 2022). Overall, potential links between licit production sites and the illegal market in the Western Balkans should be monitored closely (see also Section Cannabis resin production in the EU).

Herbal cannabis production in the EU

In the EU, herbal cannabis appears to be mainly produced for sale on domestic markets rather than for export. Estimating the total cannabis production in Europe is difficult due to the currently limited systematic monitoring of illicit cannabis cultivation, leading to a lack of data on the number and size of illicit cannabis production sites dismantled in Europe each year. Utilisation of the European Reporting on Illicit Cannabis Production (ERICP) data collection tool, developed by the EMCDDA and Europol, has remained limited. This is likely due to a combination of factors, including the time required to report large amounts of data. An additional obstacle is the difficulty of calculating potential national and EU-wide production figures from the existing studies on cannabis yield determination, as these are based on specific growing conditions that are unlikely to be representative of the varying types of illicit settings in which cannabis is grown across Europe (Toonen et al., 2006; Vanhove et al., 2014, 2017).

In addition to the standard reporting protocols, the EMCDDA also obtains information on dismantled cannabis cultivation sites from open source information and ad-hoc information-gathering exercises with supply experts and the national focal points of the Reitox network. Although these data often do not include information on the size of the dismantled sites, they do help to build a better understanding of the extent of illicit cannabis production in Europe. Based on these data, 14 Member States reported dismantling a total of nearly 7 000 illicit cannabis cultivation sites in 2019. In 2020, almost 10 000 sites were reported to have been dismantled (by 14 Member States), while in 2021, 13 Member States reported over 9 000 dismantled sites. Due to incomplete reporting, the size of these sites remains, for the most part, unknown. However, several recent cases indicate that large-scale cultivation sites are frequently detected in the EU.

Seizures of cannabis plants may be regarded as an indicator of the extent of cannabis production in a particular country. While plant seizures are reported annually to the EMCDDA, differences between countries in terms of law enforcement priorities, resources and reporting practices, mean that caution should be exercised in the interpretation of these data. Nonetheless the reported data indicate general trends in cannabis cultivation in the EU (see Figure Quantity of cannabis plants seized in the EU, 2011-2021). In 2021, more than 4.3 million cannabis plants were reported seized in the EU. Seizures in Spain accounted for 75 % of this total, or 3.2 million seized plants, representing a two-fold increase from 2020. HoweveFr, as in previous years, the country seizing the largest number of cannabis plants in Europe in 2021 was Türkiye, which reported confiscating almost 76 million cannabis plants, almost 18 times the EU total.

According to the Spanish authorities, seizures of herbal cannabis and cannabis plants in the country showed annual increases ranging from 150 % to 350 % in the period between 2015 and 2021 (Spanish Interior Ministry, 2021). In 2022, the number of cannabis plants seized in Spain could be even higher as law enforcement dismantled several large-scale illicit production sites (see Box Cannabis plantations using fake authorisations dismantled in Spain). Although large scale cannabis cultivation takes place in many EU countries, Spain has made it a law enforcement priority (Spanish Interior Ministry, 2021) which may not be the case in other countries. This is reflected in the data reported, but nonetheless confirms the emergence of Spain as one of the largest cannabis production zones in the EU.

Cannabis is cultivated both indoors and outdoors in Spain. Criminal networks in the country have also long been involved in cannabis resin trafficking from Morocco, using well-developed trafficking logistics. Information from Europol indicates that the individuals involved in illicit cannabis cultivation in Spain represent a variety of nationalities, including Spanish nationals, traffickers from other EU countries, and criminals originating from or with connections to the Western Balkan region or Asian countries.

 

The source data for this graphic is available in the source table on this page.

Environmental impact and hazards of cannabis cultivation

Information on the environmental impacts of cannabis cultivation is limited and more research is needed (EMCDDA and Europol, 2019). Some knowledge gaps in this area have recently been addressed, largely as a result of research emanating from North America, where regulated cannabis markets have been established (Wartenberg et al., 2021). Regardless of setting (indoor, outdoor or greenhouse), six environmental impact pathways from cannabis cultivation have been documented in the literature. These are water use, energy use, pesticide use, water pollution, air pollution and land cover change (Wartenberg et al., 2021; UNODC, 2022).

Water use

Cannabis plants generally require larger quantities of water compared to crops such as maize, rice or soy when grown in similar conditions (see Box Estimated water needs for outdoor cannabis cultivation).An outdoor-grown cannabis plant may for example consume between 18.9 and 20.8 litres of water per day (National Drug Intelligence Centre of the US Department of Justice, 2007; Wilson et al., 2019) and require, on average, 150 days for one harvest cycle (Butsic and Brenner, 2016). However, energy and water use vary according to a number of factors, such as geographical location, cultivation method or strain-related characteristics (Summers et al., 2021), making it difficult to extrapolate water use estimates.  

Depending on the time of year, a cannabis plant cultivated indoors may require between 9 and 11 litres per day (Wilson et al., 2019). Indoor cultivation can be undertaken throughout the year, which in many cases leads to at least four growing cycles per year (Vanhove et al., 2014). As indoor cannabis cultivation in the EU also appears to be more widespread than outdoor production, the overall water demand is likely higher. For example, an indoor cannabis cultivation site of 500 plants and operational throughout the year would potentially consume between 1.6 million and 2.0 million litres of water annually. Some indoor cannabis sites in Europe consume additional quantities of water, for instance those using water-cooled air-conditioning (Vanhove et al., 2023).

Energy use

Energy use accounts for the largest share of carbon dioxide emissions caused by indoor cannabis cultivation (Summers et al., 2021). Most of the energy directly expended in indoor cultivation is used to power lighting and for water and air circulation, while in outdoor sites the majority of the energy used directly is channelled into pumping water and producing fertilisers (Wartenberg et al., 2021) (see Box Carbon footprint of cannabis production). Additionally, an indirect use of energy derives from the use of fertilizers, whose production is an energy-intensive process with considerable carbon emissions. Some studies have estimated that illicit cannabis cultivation sites consume large amounts of electricity (Mills, 2012; Summers et al., 2021; EMCDDA and Europol, 2019). However, the total quantity of energy used by such sites in a specific area is difficult to assess, as data on the size, conditions and number of cannabis cultivation sites are rarely comparable and often incomplete, which makes inaccuracies in terms of extrapolation inevitable (Vanhove et al., 2017; UNODC, 2022). According to the Dutch electricity grid operator, a total of 111 million kilowatt hours of electricity was stolen in 2021 by the operators of at least 1 800 indoor cultivation sites discovered by the police. By extension, the operator estimated that more than 1 billion kilowatt hours of electricity was stolen to power illicit cannabis cultivation sites in the Netherlands that year (²); which is more than the annual consumption of all the households in the city of Rotterdam (Netbeheer Nederland, 2022) (see Box Criminal network steals EUR 1.5 million worth of electricity for industrial-scale cannabis cultivation in Spain).

Pesticide use, and water and air pollution

The use of pesticides alongside water and air pollution (e.g. contamination by fertilisers and fungicides) related to agriculture is a global issue, with numerous negative impacts on the environment, such as the disruption of ecosystems and adverse effects on human health (Wartenberg et al., 2021). To date, no quantitative study has measured the contribution of pesticides to water and air pollution from illicit cannabis cultivation (Cuypers et al., 2017; Wartenberg et al., 2021; UNODC, 2022). According to recent research, some of the chemical particles associated with cannabis odours may negatively affect air quality (Seltenrich, 2022). While further research is needed in this area, the environmental and human health impacts of cannabis cultivation are assessed as posing a growing threat (Wartenberg et al., 2021; UNODC, 2022).

Land cover change

Most of the existing research on the links between illicit drug crop cultivation and climate change has focused on the carbon dioxide emissions caused by direct and indirect deforestation (UNODC, 2022). Studies quantifying deforestation resulting from the outdoor cultivation of illicit drug crops mostly relate to coca crops grown for cocaine production in South America, while such studies on cannabis cultivation are very scarce (Wartenberg et al., 2021).

Hazards of illicit cannabis cultivation

Since illicit cannabis cultivation sites do not comply with health and safety standards, they present a range of potential human hazards. These can be physical, electrical, chemical or biological in nature (Vanhove et al., 2018).

Cannabis resin production outside the EU

Most of the cannabis resin consumed in Europe has traditionally originated from sources of production outside the region – predominantly from Morocco, although Afghanistan, Albania and Lebanon have also been mentioned as marginal sources. Although there is little doubt that Morocco remains the largest supplier of the European cannabis resin market, it is often difficult to identify other potential sources, including within the EU, due to insufficient profiling of the cannabis resin available in Europe.

Other countries, such as India, Nepal, Pakistan and some Central Asian nations are known producers but do not seem to supply the European market in any significant way. It has recently been claimed that large-scale cannabis resin production is taking place in Syria (Reuter, 2020; COAR, 2021). A number of multi-tonne cannabis resin consignments shipped from Syria were seized in EU ports between 2018 and 2020, often together with large amounts of captagon tablets (see Amphetamine module). However, the seized cannabis resin may have been produced in Lebanon and then smuggled to Syria before shipping. It is unlikely that the resin and captagon seized in EU ports from ships departing Syria were destined for the European drug market; their end destination was probably the Persian Gulf.

After remaining fairly constant for about 10 years (EMCDDA and Europol, 2019), cannabis cultivation and resin production appear to have declined sharply in Morocco in 2018 and 2019 (UNODC, 2022). However, a key limitation is that cannabis resin production has long been underestimated in Morocco (EMCDDA, 2012). International data indicate that the area under cannabis cultivation, reported at around 47 000 hectares between 2010 and 2018, decreased to 21 000 hectares in 2019 (-55 %). Similarly, estimated cannabis resin production, which was reported at between 700 and 760 tonnes a year between 2010 and 2017, decreased to 424 tonnes in 2018 (-41 % compared to 2017) before increasing to an estimated 596 tonnes in 2019 (-17 % compared to 2017) (UNODC, 2022; EMCDDA and Europol, 2019). It is difficult to reconcile the production estimates of Moroccan cannabis resin with seizures likely to be of Moroccan origin carried out in Europe and North Africa. For instance, Morocco, Algeria and Spain together reported seizures of cannabis resin of approximately 541 tonnes in 2018 and more than 720 tonnes in 2019 (UNODC, 2022). This points to the probability that cannabis resin production continues to be underestimated in Morocco.

In addition, Moroccan cannabis resin estimates do not take into account the developments that have affected production in the Rif region for a number of years. As reported in the previous edition of this report, the cultivation of hybrid cannabis plants with potentially much higher resin yields and THC content are gradually replacing ‘traditional’ cannabis plant varieties (EMCDDA and Europol, 2019). This modernisation of the Moroccan cannabis industry, which may have been introduced by European growers established in the Rif (Chouvy and Macfarlane, 2018), allows the production of cannabis resin and extracts of higher potency than in the past. These changes in Morocco are likely to be a major contributor to the dramatic increase (191 %) in the potency of seized cannabis resin in Europe since the early 2010s. However, there may also be other factors influencing this development, such as the possible production of high-potency resin in Europe (see Figures Indexed trend of mean potency (% THC) of cannabis resin in the EU, 2011-2021 and Average of maximum and minimum values for cannabis resin potency (% THC) in the EU, 2011-2021 (EMCDDA and Europol, 2019; Rigter and Oomen, 2021).

 

Source: The source data for this graphic is available in the source table on this page.

 

Source: The source data for this graphic is available in the source table on this page.

Cannabis resin production in the EU

Cannabis resin is also produced in the EU from locally grown cannabis using methods such as ice-cooling or ‘Pollinators’ (EMCDDA and Europol, 2019). This has been the case in the Netherlands for many years, where locally grown plants are used to produce ‘nederhasj’ (‘netherhash’), a type of resin usually containing a high percentage of THC and low levels of CBD. There are signs that similar types of high-potency cannabis resin are produced in other European countries. For instance, since 2014, Austria, Belgium and Hungary have reported to the EMCDDA a small number of offences related to cannabis resin production. Although it is difficult to ascertain the scope of the phenomenon, there are some indications that cannabis resin production in Europe may be increasing, that it is probably larger than presently available data suggest and that much of the resin produced has a high concentration of THC.

Annual monitoring of cannabis products sold in Dutch coffeeshops indicates that some of them sell ‘nederhasj’. In the 2018-2021 period, the average potency of ‘nederhasj’ was found to be between 21 % and 29 % THC, although some samples contained over 70 %. While the imported cannabis resin sold in Dutch coffeeshops over the same period – almost all of which was likely imported from Morocco – was found to have a somewhat lower average potency (between 23 % and 25 %), in the last few years this average has increased steadily, with some samples found to contain over 50 % THC. There are no indications of large-scale production of ‘nederhasj’, and only a minority of coffeeshops in the sample sold locally produced resins (Rigter and Oomen, 2020, 2021). However, it should be noted that a study commissioned by the EMCDDA indicated that two-thirds of the samples of cannabis resin seized in Denmark (N = 47) were Dutch-type and only about a third were Moroccan-type. This is a strong indication that at least some ‘nederhasj’ is being trafficked to drug markets outside the Netherlands (Freeman, 2020).

There are signs that significant quantities of high-potency cannabis resin are manufactured in other EU countries. For instance, a cannabis cultivation site that also produced extracts, including resin, was dismantled by the Greek police in 2018 (EMCDDA and Europol, 2019). Several law enforcement operations in Spain over the last two years, some of which have involved sites specifically dedicated to cannabis resin production, have also led to seizures of cannabis-resin-manufacturing equipment, cannabis resin, cannabis oil and cannabis plant material ready for processing into resin.

In June 2021, Operation Overdose led to the dismantling by the Spanish Guardia Civil of ‘one of Spain’s first hashish production sites’ in Alicante Province. Industrial equipment to manufacture cannabis resin was seized, as well as more than 8 tonnes of cannabis products including a large quantity of cannabis resin powder, several 1-kilogram resin packages and plant material in different stages of processing (Guardia Civil, 2021a). In July 2022, Spanish law enforcement dismantled a huge cannabis production site spread over 32 hectares in Barcelona Province, seizing a total of 6 tonnes of cannabis plants and herbal material. The site, which had been active since at least 2018, had posed as a licit industrial hemp production facility but lacked the necessary licences (see Box Cannabis plantations using fake authorisations dismantled in Spain). This facility produced significant amounts of cannabis resin, seizures of which yielded 305 kilograms in powder form and 17 kilograms in pressed form, alongside chopped plant material likely intended for the manufacture of cannabis resin (Guardia Civil, 2022a). Large amounts of chopped cannabis have also been seized from other dismantled illicit plantations in Spain, for instance during Operation Safari, in Toledo Province in October 2021 (Guardia Civil, 2021b). In February 2023, an Italian-led criminal network investigated by Spanish and Italian police had set up a large cannabis plantation in southern Spain where they manufactured cannabis resin. The criminal group was composed of Albanian, Italian, Spanish and Moroccan nationals, and was also involved in smuggling cannabis resin from Morocco into Europe. Twenty suspects were arrested and 2.5 tonnes of cannabis resin, 45.6 kilograms of herbal cannabis and EUR 5.5 million in assets were seized (Europol, 2023a). 

Overall, as observed in the previous edition of this report (EMCDDA and Europol, 2019), the widespread availability and ease of purchasing equipment to produce cannabis resin, combined with the extensive cultivation of cannabis plants in Europe, means that the manufacturing of cannabis extracts, especially cannabis resin, could become more widespread in the future.

(1) In this section ‘THC’ on its own refers to delta-9-tetrahydrocannabinol (delta-9-THC). When discussing other forms of THC, the term ‘delta-9-THC’ is explicitly mentioned.

(2) The Dutch electricity grid operator based its estimates on a national total of 30 000 illicit cultivation sites, with each site consuming 35 000 kilowatt hours per year.

(3) In cases where the deforestation took place specifically to establish the cannabis cultivation site. Data on biomass stocks in temperate forest regions: 5 kilograms carbon dioxide per square metre.

(4) Average greenhouse gas emissions of electricity generation in Europe in 2020: 229 grams carbon dioxide per kilowatt hour (European Environment Agency, Energy indicators).

(5) Real-world exhaust emissions of plug-in hybrid electric vehicles (PHEVs): 90-105 grams carbon dioxide per kilometre (Plötz et al., 2022).

Source data

Factors determining yield of indoor cannabis cultivation

Factor	Level 2	Level 3	Number
Agricultural inputs	Nutrients		1
Agricultural inputs	Plant growth regulators		1
Agricultural inputs	Substrate	Peat soil	1
Agricultural inputs	Substrate	Hydroponics system	1
Environment	Light	High-pressure sodium lamps	0.6
Environment	Light	Metal halide lamps	0.6
Environment	Light	LED	0.6
Environment	Atmospheric control	CO2 concentration	0.6
Environment	Atmospheric control	Temperature	0.6
Environment	Atmospheric control	Electrical conductivity	0.6
Environment	Atmospheric control	Water-cooled air conditioners	0.6
Process and treatment	Pruning and training	Defoliation	0.6
Process and treatment	Pruning and training	Lollipopping	0.6
Process and treatment	Pruning and training	Low-stress training	0.6
Process and treatment	Propagation	Cuttings	0.6
Process and treatment	Propagation	Seeds	0.6
Process and treatment	Propagation	Monster cropping	0.6
Process and treatment	Plant density		0.9
Plant strain and variety	Auto- flowering		2.5
Plant strain and variety	Photoperiodic plants		2.5

Quantity of herbal cannabis seized in the Western Balkans, 2017-2021 (Tonnes)

Drug	2017	2018	2019	2020	2021
Herbal cannabis (tonnes)	89.524	31.214	19.559	14.319	14.442

Indexed trend of mean potency (% THC) of cannabis resin in the EU, 2011-2021 (Index (base = 100))

Year	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021
Potency resin (THC %)	100	126	137	151	157	169	177	194	224	227	291

Average of maximum and minimum values for cannabis resin potency (% THC) in the EU, 2011-2021 (% THC)

Year	Min	Max
2011	4	16.1
2012	2.4	17.2
2013	5.8	22.4
2014	7.3	20.7
2015	7	26.6
2016	7	24
2017	8.5	24.2
2018	9.4	26.9
2019	12	28.8
2020	12	28.9
2021	10.3	30.6

References

Consult the list of references used in this module.