Hemp Sustainability: What the Data Really Shows

Hemp is one of the most resource-efficient crops in temperate agriculture. Peer-reviewed comparisons put its crop water requirement about 38 % below cotton and its total water footprint about 60 % below, and field research estimates carbon uptake at roughly 8 to 15 tonnes of CO2 per hectare in a single season. But hemp is not automatically sustainable. Whether a finished hemp product is genuinely low-impact depends on how it was grown, dried, extracted and shipped - and indoor cultivation under artificial light can cancel out every advantage the plant has in the field.

This article separates the measured figures from the marketing, and explains what sustainable hemp cultivation looks like under Swiss conditions. It is written by the team behind Vapor Spirit, a certified organic CBD Shop operating in Zürich since 2015.

Is hemp sustainable? The short answer

Hemp scores well on four measurable points: low irrigation demand, minimal need for pesticides, fast biomass build-up, and a deep root system that improves soil structure. It scores badly on two: energy-intensive indoor cultivation, and long transport routes for cheap imported biomass.

In other words, "hemp" is not a sustainability claim. "Field-grown, organically certified, regionally processed hemp" is.

Hemp and carbon: how much CO2 does one hectare absorb?

Hemp reaches maturity in roughly 100 to 120 days and can produce 10 to 15 tonnes of dry matter per hectare, of which around 45 to 50 % is carbon by weight. Research from the Centre for Natural Material Innovation at the University of Cambridge puts atmospheric uptake at approximately 8 to 15 tonnes of CO2 per hectare per growing season, compared with roughly 2 to 6 tonnes per hectare per year for typical forest.

Why the higher figures need context

You will frequently see the claim that one hectare of hemp absorbs 22 tonnes of CO2, or 44 tonnes with two harvests. That figure comes from industry advocacy papers rather than from independent life-cycle assessments, and it describes gross uptake during growth - not net sequestration.

The distinction matters. Carbon is only removed from the atmosphere for the long term if it stays locked in something durable: hemp-lime insulation, fibreboard, textiles, or stable soil organic matter. Hemp that is burned, composted or smoked returns its carbon within months. Academic reviews using conservative harvest yields arrive at figures closer to 3 to 4 tonnes of CO2 per hectare of net sequestration, plus an additional 2 to 5 tonnes stored over the lifetime of hemp-derived building materials.

Honest summary: hemp is a strong carbon crop, roughly twice as effective per hectare per year as average forest, but it is not a climate solution on its own.

Water: hemp versus cotton in numbers

Water use is where hemp's advantage is best documented. A 2023 meta-analysis in the Journal of Agrometeorology compared data from 28 published sources and found the following differences against cotton.

Metric	Hemp vs. cotton	What it means
Crop water requirement (CWR)	38 % lower	Less total water per crop cycle
Total water footprint (WF)	60 % lower	Less water per kilogram of usable fibre
Crop irrigation requirement (CIR)	84 % lower	Far less artificial irrigation
Irrigated water footprint (IWF)	91 % lower	Minimal draw on groundwater and rivers
Land for the same fibre yield	approx. one third	Higher fibre output per hectare

Be sceptical of the widely shared claim that hemp needs 300 to 500 litres of water per kilogram while cotton needs 20,000. Those numbers compare best-case rain-fed hemp against worst-case irrigated cotton in arid regions. The peer-reviewed range above is less dramatic and far more defensible.

In Swiss and Central European conditions the practical point is simpler: hemp generally grows without any irrigation at all. Research at the Bern University of Applied Sciences on winter hemp for textiles confirms that hemp performs well under Swiss conditions without irrigation and with little to no plant protection products, while cotton cultivation accounts for an estimated 10 to 20 % of global pesticide use.

Soil health, deep roots and crop rotation

Hemp develops a pronounced taproot that can reach up to two metres. This breaks up compacted layers, improves aeration and water infiltration, and leaves organic matter deeper in the soil profile than shallow-rooting crops do.

Because the canopy closes quickly and densely, hemp also suppresses weeds mechanically, which is one of the reasons it needs little or no herbicide. In a rotation, that makes it a useful break crop: it interrupts pest and disease cycles from cereals and reduces the pressure that continuous monoculture puts on soil microbiology.

Phytoremediation - the qualified version

Hemp is often described as a soil cleaner because it takes up heavy metals such as cadmium, lead and nickel. This is accurate, and it is exactly why it cannot be both things at once.

A hemp plant grown to remediate contaminated soil accumulates those contaminants in its biomass. That biomass is then unsuitable for food, cosmetics or extraction. Any producer claiming their flowers come from a phytoremediation site is either confused or selling something you should not consume. For consumables the relevant question is the opposite: was the soil clean, and does the batch certificate of analysis show heavy metal and pesticide screening?

We cover how to spot the difference in our guide on recognising low-quality CBD products and reading lab analyses.

Where hemp sustainability claims fall apart

Most articles on this topic stop at the field. The larger share of a finished product's footprint, however, is decided after cultivation - in the lighting, the drying and the extraction.

Indoor cultivation under high-intensity lamps, with active climate control and dehumidification, is by an order of magnitude the most energy-intensive way to produce cannabis flower. Greenhouse cultivation uses daylight and needs supplementary light and heating only in the shoulder seasons. Outdoor cultivation is the lowest-impact option, at the cost of a single annual harvest and greater weather dependence.

Cultivation method	Energy demand	Harvests / year	Typical trade-off
Indoor	Very high	4 to 6	Highest consistency and terpene retention, highest footprint
Greenhouse	Moderate	2 to 4	Good balance of control and daylight use
Outdoor / field	Low	1	Lowest footprint, most weather-dependent quality
Fibre / seed hemp	Very low	1 to 2	Not used for flower; feeds textiles, food, construction

We label cultivation method openly rather than describing everything as "natural". You can compare greenhouse-grown flowers against indoor-grown flowers directly, and our detailed comparison of indoor versus outdoor cultivation explains what each method does to terpene profile, appearance and price.

Hemp cultivation in Switzerland

Switzerland is a small but instructive hemp market. Outdoor hemp acreage has grown steadily since 2015 and stood at around 291 hectares in 2020, according to figures cited by Agroscope, the Swiss federal centre of excellence for agricultural research. Agroscope runs variety trials and cultivation-technique projects specifically for hemp, including the CBD-flower segment.

The regulatory framework is unusually clear. Under Swiss law, hemp containing less than 1 % THC is not treated as a controlled narcotic and may be cultivated and marketed agriculturally. Since 1 January 2021, seed-law requirements for industrial hemp below that threshold have been dropped, although plant-health rules and a plant passport still apply. We explain the threshold in detail in our article on the THC limit for hemp products in Switzerland.

For a producer, that combination - a temperate climate that needs no irrigation, short transport distances and a stable legal status - is what makes genuinely low-impact hemp realistic rather than aspirational. It is also the reason our own range is Swiss Made rather than imported.

Bio Suisse and Demeter: what the labels actually certify

Two Swiss certifications carry real weight in hemp:

●       Bio Suisse (Knospe / Bud): whole-farm organic conversion, no synthetic pesticides or mineral nitrogen fertiliser, mandatory biodiversity areas on at least 7 % of the farmland, and restrictions on processing aids. It certifies the operation, not just the individual field.

●       Demeter (biodynamic): everything organic requires, plus closed nutrient cycles, biodynamic field preparations, and a mandatory link between livestock and arable land. It is the stricter of the two.

Both are audited annually by an independent body, which is the meaningful difference between a certification and a claim on a label. You can read what that means for our products under vegan and organic hemp products from Switzerland and on our about us page.

Hemp compared with other crops

Criterion	Hemp	Cotton	Maize	Softwood forest
Irrigation need	Very low	Very high	Moderate to high	None
Pesticide need	Very low	Very high	High	Low
Time to harvest	100 to 120 days	approx. 180 days	approx. 150 days	25 to 80 years
CO2 uptake per ha/year	approx. 8 to 15 t	Low	approx. 5 t	approx. 2 to 6 t
Rooting depth	up to 2 m	approx. 1 m	approx. 1 m	Deep
Usable plant share	Almost complete	Fibre only	Grain, silage	Timber

The figures are indicative ranges, not fixed constants: real outcomes depend on variety, soil, climate and management. The pattern, however, is consistent across sources - hemp delivers a high usable yield for comparatively low input.

What this means when you buy hemp products

If sustainability is one of your buying criteria, four questions separate a credible product from a green-sounding one:

●       Where was the hemp grown, and is the origin actually named rather than described as "European"?

●       Was it field, greenhouse or indoor grown - and does the seller say so unprompted?

●       Is there an organic certification from an audited body, or only organic-sounding wording?

●       Is a current batch certificate of analysis available, covering cannabinoids, pesticides and heavy metals?

Our Swiss-grown range covers CBD oil, CBD flowers and CBD cosmetics. Customers outside Switzerland can order through the European shop. If you want to understand how the extract itself is produced, see our explainer on CO2 extraction.

If you prefer to see and smell the material before buying, our CBD Zürich store at Rosengartenstrasse 3 in Zürich-Wipkingen is open Monday to Friday from 11:00 to 18:30 and Saturday from 12:00 to 16:00. Directions and opening hours are on the store page, and customer reports are collected under experiences with Vapor Spirit.

Frequently asked questions

Is hemp really more sustainable than cotton?

For fibre, yes, and the evidence is solid. A 2023 meta-analysis across 28 studies found hemp requires roughly 38 % less crop water and has a 60 % smaller water footprint than cotton, needs about a third of the land for the same fibre yield, and requires far fewer plant protection products. The advantage is largest in temperate climates where hemp grows rain-fed.

How much CO2 does one hectare of hemp absorb?

Research from the University of Cambridge puts uptake at around 8 to 15 tonnes of CO2 per hectare per growing season, roughly double the 2 to 6 tonnes typical of forest. Net long-term sequestration is lower, because carbon only stays out of the atmosphere if the biomass ends up in durable products or stable soil organic matter.

Does hemp clean contaminated soil?

Hemp does take up heavy metals such as cadmium and lead, which makes it useful for phytoremediation. But biomass grown on contaminated land accumulates those contaminants and must not be used for food, cosmetics or extraction. Remediation hemp and consumable hemp are two different supply chains.

Is indoor-grown hemp flower less sustainable than outdoor?

Yes, substantially. Indoor cultivation requires artificial lighting, climate control and dehumidification year-round, which dominates the product footprint. Greenhouse cultivation sits in between, and field-grown hemp has by far the lowest energy demand. Indoor growing is chosen for consistency and terpene retention, not for its environmental profile.

What does Bio Suisse certification mean for hemp?

Bio Suisse certifies the whole farm, not a single field: no synthetic pesticides or mineral nitrogen fertiliser, at least 7 % of farmland as biodiversity area, restrictions on processing, and an annual independent audit. Demeter adds biodynamic requirements and closed nutrient cycles on top of that.

Is hemp cultivation legal in Switzerland?

Yes. Hemp with less than 1 % THC is not classified as a narcotic under Swiss law and can be cultivated and marketed agriculturally. Since January 2021 seed-law requirements no longer apply to industrial hemp below that threshold, though plant-health rules and a plant passport remain in force. Cantonal notification requirements vary.

Where can I buy Swiss organic hemp products?

Vapor Spirit has sold Swiss-grown hemp products since 2015, online and from the store at Rosengartenstrasse 3 in Zürich. The full range is at https://www.vaporspirit.ch/ and includes oils, flowers, cosmetics and accessories, with batch lab reports available on request.

Sources

●       Agroscope - Hanf (Cannabis sativa L.), Swiss acreage and variety trials: https://www.agroscope.admin.ch/de/hanf-cannabis-sativa-l

●       Federal Office for Agriculture (BLW) - Hanf, legal framework and the 1 % THC threshold: https://www.blw.admin.ch/de/hanf

●       Bern University of Applied Sciences (BFH) - winter hemp for textiles in Switzerland: https://www.bfh.ch/de/forschung/forschungsprojekte/2022-251-128-726/

●       Wise et al. (2023), Journal of Agrometeorology - water requirements and water footprints of hemp and cotton: https://journal.agrimetassociation.org/index.php/jam/article/view/2260

●       Swiss Farmers Union (SBV) - hemp in Swiss agriculture: https://www.sbv-usp.ch/de/hanf-in-der-schweizer-landwirtschaft

Notice

This article is intended solely for general informational purposes and does not constitute medical advice. Cannabidiol (CBD) is not a medicinal product. No therapeutic or health claims are made.

Legal notice (Switzerland)

CBD products are legal in Switzerland provided the THC content does not exceed 1 %. This content refers exclusively to the legal situation in Switzerland. If you have health-related concerns, consult a qualified medical professional.