In Germany you can now smoke, possess and grow cannabis. Weed production generates a lot of greenhouse gases, but there is also a better way.

Hemp leaves under artificial lighting.

A light goes on: grow lamps make cannabis potentially bad for the climate Photo: Mystery/imago shot

Germany now allows smoking marijuana. In reality, everything has an impact on the climate. That too?

Yes. But measuring the effect is not so easy. To be sure, the federal government didn't even try. When asked, Karl Lauterbach's Ministry of Health (SPD), responsible for the cannabis law, defers to Cem Özdemir's (Greens) Ministry of Agriculture for his technical expertise, which he defers due to his leadership. The Ministry of Economy and Climate of Robert Habeck (Greens) suspects that the information comes from Özdemir or the Minister of the Environment, Steffi Lemke (Greens), who in turn suspect the Ministry of Agriculture. If the traffic light government were to implement the promised climate control, it would have to verify the climate adequacy of all its laws. But as things stand, they often find themselves in ecological obscurity.

What does the cannabis law allow?

Since April 1, adults can legally smoke joints in Germany, even without medical need. You can carry up to 25 grams of cannabis with you and possess a total of 50 grams at your place of residence. The number of joints produced depends on personal dosage, the norm is three per gram. Adults who have lived in Germany for at least six months can grow up to three cannabis plants at their place of residence, but only for that. Own use.

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Attention: If all three plants prosper, you will probably obtain more than the 50 grams allowed; according to the law, the excess must be destroyed. It is not allowed to sell the herb or give it away. Only three companies remain authorized for commercial cultivation in Germany: Aurora Cannabis, Tilray and Demecan. They produce cannabis for medical use. Starting July 1, several people will be able to form together so-called cultivation associations, either as an association or cooperative. Anyone who wants to grow their own marijuana should always take “appropriate safety precautions” to protect seeds, plants, and finished marijuana from unauthorized access, especially by children.

Is there data on the amount of greenhouse gases caused by grass production?

For example from the United States. In one study, a research team led by Hailey Summers of Colorado State University arrived at a range of 2.3 to 5.2 tons of greenhouse gases per kilogram of dried flowers, depending on the region. The results are in the specialized magazine. Nature sustainability appeared. This variation is mainly explained by the respective states' reliance on climate-damaging coal to generate electricity.

Does this mean that smoking marijuana is always bad for the climate?

No, you can also grow cannabis in a much more climate-friendly way. “CO is the lowest2Footprint when grown outdoors,” explains agricultural economist Bernhard Osterburg from the Thünen Institute in Braunschweig, who conducts research and policy advice on agriculture, forestry and fisheries. After all, plants that are outdoors in the sun don't need grow lights, and their huge energy consumption is what causes CO emission.2-The balance of smoking marijuana is potentially bad. However, it still largely depends on where production takes place. In Germany last year more than half of the electricity was generated from renewable energies such as wind and solar. This is significantly better than the electricity assumed by, for example, the American study.

When grown outdoors, the United Nations Office on Drugs and Crime accounts for between 22.7 and 326.6 kilograms of greenhouse gases per kilogram of cannabis. The results are particularly bad when forests are cleared for fields. The climate footprint also depends on other factors: how much is plowed, how much is fertilized with nitrogen? Do tractors run on diesel?

Also the 22.7 kilograms of CO2, which the United Nations cites as the lower limit of the climate footprint of outdoor cannabis, remain relatively high for a plant-based agricultural product. According to a study by the Ifeu Institute, a kilo of tomatoes produces on average less than a kilo of carbon dioxide. But since the new law still severely limits the cultivation of cannabis, a true agricultural industry cannot be expected: it can only be grown for personal consumption. Three plants in a flower bed have little impact in terms of climate. The greenhouse is also a middle point between fully illuminated indoor cultivation and a completely free garden or field.

What effect does German law have on cannabis?

Anyone who now grows their plants openly in the garden or on the balcony instead of secretly in the illuminated closet will save emissions. Compared to marijuana that is not homegrown, its origin is crucial: Is weed from a Moroccan field or a factory replaced by artificial light? In some cases, protection requirements may speak against outdoor cultivation, since access to third parties is not allowed.

Georg Wurth of the German Hemp Association also suspects that the maximum possession amount is rather an incentive for indoor cultivation, which damages the climate. After all, the garden only has one harvest per year, which can produce a maximum of 50 grams. If you want more, you have to enter. This is certainly important for your personal climate balance and also for your electricity bill. The German Hemp Association estimates that a 95-day harvest cycle requires around 200 kilowatt hours of electricity for 50 grams of herb. That's more than the average refrigerator with freezer uses all year long. You can improve your carbon footprint by switching to green electricity from a trusted supplier. Wurth himself from the Hemp Association is a supporter of climate-friendly outdoor cultivation: “My grass likes to see the sun.”