Cannabis grows well outdoors; give it sun, soil, and water and it behaves like any other flowering annual. Only a small portion of the cannabis sold in legal markets is grown outdoors however, and the indoor & greenhouse grows contribute most of the industry’s environmental footprint.
More recently, however, there's been a shift in how flower is grown, how it's shipped, and what information growers are willing to verify on product labels. Here are some of the biggest changes and how you can be a more eco-conscious consumer.
In this article:
Why cannabis has an outsized footprint
Most legal cannabis in the United States is grown indoors, under artificial light, in rooms that are heated, cooled, dehumidified, and carbon-dioxide enriched around the clock. That setup delivers consistent flower every week of the year, but draws an enormous amount of electricity.
A Colorado State University team ran a life-cycle analysis of indoor cannabis production across the country and published the results in Nature Sustainability. Indoor cultivation generates between 2,283 and 5,184 kilograms of carbon dioxide for every kilogram of dried flower, depending on the local climate and power grid. Outdoor cultivation produces 22.7 kilograms. Climate control equipment accounted for more of that energy than the grow lights did. Scaled down to what a cannabis shopper actually buys, one ounce of cannabis grown indoors can carry up to the same carbon footprint as burning 16 gallons of gasoline.
Water varies by region but still follows an overall similar pattern. Massachusetts regulators publish water-use benchmarks for cultivators and recommend greenhouse or outdoor settings to bring demand down. Analysts have also argued that the industry’s standard way of measuring water use understates how much large indoor cannabis grow facilities actually consume.
Grow method
CO₂ per kg of dried flower
What drives it
Outdoor (sun-grown)
~23 kg
Sunlight does most of the work; almost no climate control
Greenhouse
~327 kg
Supplemental lighting, partial climate control
Indoor
2,283–5,184 kg
Round-the-clock HVAC, high-intensity lighting, CO₂ enrichment
The packaging problem
Every gram of legal cannabis arrives in a container engineered to satisfy child-resistance, tamper-evidence, and opacity rules. In practice that means rigid plastic, often in a package several times larger than the product inside it. Plastic has historically made up more than half of all cannabis packaging sold as legal markets scaled up.
Traditional curbside recycling mostly can't process it. Municipal sorting equipment typically filters out anything smaller than about four inches across, which includes nearly every pre-roll tube, concentrate jar, and eighth container on the shelf. Those pieces drop out before they can ever be sorted to be recycled.
Independent programs have started cropping up to address this issue. Maryland’s High 5 Initiative has recycled at least 500,000 pieces of cannabis packaging collected from 40 participating dispensaries and ground it into commercial resin. In Oregon, P3 Distributing runs a drop-box program with roughly 60% of the state’s dispensaries and has collected more than 100,000 pounds of plastic since 2018 — about 10% of the state’s cannabis packaging waste, which is even better than the national polypropylene recycling rate.
If your dispensary keeps a return bin near the register, that's probably what it's for. If not, it never hurts to suggest having something like that implemented.
What different product certifications actually mean
“Organic” is one claim you should never see on a cannabis package: the USDA National Organic Program cannot certify a crop that remains federally illegal. Private certifications have filled that particular void, but they verify very different things.
Seal
What it verifies
Where you will see it
Sun+Earth Certified
Regenerative organic practices, sun-grown, fair wages and working conditions
Craft outdoor farms
Clean Green Certified
Third-party audit of inputs and processes, modeled on national organic standards
Indoor and outdoor, multiple states
DEM Pure
Living soil, no bottled nutrients or synthetic inputs
Small-batch farms, mostly West Coast
“Sustainably grown,” no seal
Nothing verifiable — unregulated marketing language
Everywhere
Sun+Earth Certified sets the highest bar as it requires cannabis grown in living soil under natural sunlight with no synthetic pesticides or fertilizers, and it audits fair wages and safe working conditions alongside the farming itself. The labor criteria is unusual for an environmental seal, but it overlaps with the wider (and much-needed) equity conversation happening across the industry.
Don't overthink it
If you're feeling overwhelmed, here are three details you can quickly & easily check when you're shopping for cannabis:
Grow method. Sun-grown and greenhouse flower carry a small fraction of the footprint of indoor, and the old assumption that outdoor means lower quality has not held up. Choosing products by grow style is the single highest-leverage habit here. Fall is also the easiest time to act on it, since the outdoor harvest lands on shelves through October. Most menus do not label grow method, so look for “sun-grown,” “outdoor,” or “greenhouse” on the package, or ask the staff behind the counter.
Package size and material. Glass and paperboard get recycled far more reliably than small rigid plastics. Buying a larger format rather than four single-gram containers also cuts the material per gram substantially — and flower stored in a sealed glass jar holds its terpenes longer, so the sustainable choice is usually the better-tasting one.
A named farm. Sustainability claims only mean something when there is a specific farm attached to them. Packaging with a listed cultivator, harvest date, and grow method is more trustworthy and providing verifiable information.
Takeaways
Indoor cultivation generates at least 100 times more carbon per kilogram of dried flower than outdoor, with climate control equipment accounting for the majority of the load.
Most cannabis packaging is too small for municipal recycling equipment to sort, which is why dispensary take-back bins exist. Ask whether your store has one (and if they don't, consider suggesting they do).
“Organic” cannot legally appear on a cannabis label, so private seals like Sun+Earth, Clean Green, and DEM Pure are the eco-friendly certifications to look for instead.
“Sustainably grown” with no seal or farm name behind it is unregulated marketing language and not reliable or verifiable.
Grow method, package size, and a specified farm are the three easiest-to-check details when shopping with sustainability in mind.
