Hemp waste...where does it go?
Photo by: Marcin Jozwiak, @marcinjozwiak
Cannabis and Hemp products are taking the nation by storm now that these plants have been legalized for recreational use in 17 states. But a lot of demand requires just as much supply - which means a LOT of agricultural waste. According to Alai, the CEO of 9Fiber, “every acre of hemp harvested generates two to five tons of stalk waste, while every pound of cannabis harvested results in 1.5 to 4.5 pounds of stalk waste.”
The cannabis flower is the primary part of the plant containing THC and CBD, and once harvested, the rest of the plant is considered non-hazardous cultivation waste. Leaves, stalks, trimmings, failed plants and flowers - all organic fibrous material that will go to one of four places:
Composter
Digester
Landfill
Incinerator
Composting:
Composting cannabis waste on-site is a very popular method of cannabis waste management because the resulting compost can be used as a fertilizer by the cultivators to produce more crops. However, some states limit the amount of cannabis waste that can be used in this way, such as Oregon, which only allows 100 tons per year.
The only negative side to the composting process is that natural composting is aerobic - meaning oxygen is required. Microorganisms break down the material through aerobic respiration to oxidize the organic matter, which produces carbon dioxide much like human respiration.
In-Vessel Digestion:
In-Vessel digestion, according to CalRecycle, a branch of the California Environmental Protection Agency, includes aerobic digestion, anaerobic digestion, and other controlled biological decomposition processes. These processes take place in a sealed container in which the entire digestion process can occur. For a cultivator, this means that they would need to self-haul or pay a hauler to transport their waste to a permitted in-vessel digestion facility.
Anaerobic digestion is a process that requires no oxygen, and within the oxygen-free container, bacteria breaks down the organic material which then produces biogas, primarily made up of methane. This system is much slower than aerobic digestion but the biogas can be used as an energy source or vehicle fuel, making it one of the cleanest transportation gasses according to California’s Low Carbon Fuel Standard.
Landfills:
In California, cultivation waste is fortunately considered as a green material, or organic waste. However, cannabis waste is only considered organic as long as it is not combined with any hazardous or toxic material. With most disposal, bleach or another chemical agent is mixed in to deface the plant, which makes it unusable for composting and the waste must go to a landfill.
But let’s consider pure organic cannabis waste. Can you just throw it away and send it off to a landfill anyway? In California you can. Because organic waste falls under the Regional Waste Franchise Authority, a commercial cannabis cultivator can throw their unwanted cannabis waste into their municipal trash bin.
This has become such a problem that many landfills are running out of space, and “actually have regulations prohibiting you taking large bulk agricultural product to the landfill.” In fact, Washington State completed a study in 2018 which “found that landfills accumulated 1.7 million pounds of plant waste since legalization in 2014.” This is a problem since plants do not decompose safely in landfills (due to the lack of oxygen and soil microbes), but instead release the harmful greenhouse gas, methane, which is 84 times more potent than CO2 over the course of 20 years.
Incinerators:
Incineration is an attractive waste management option for cannabis waste because within minutes all you’re left with is ash, a sterile material that can be disposed of in the trash or composted in the field. But why go through the trouble of incinerating the cannabis waste if you’re still left with a product that needs disposal? Well, one benefit is that the volume of ash produced is only about 2% of the original volume that goes in, so it would not take up as much space in the landfills. However, is it worth releasing all the carbon into the atmosphere that the plant has already taken out through photosynthesis?
Creating a Circular Economy & Pollima:
Fortunately, some companies are attempting to “close the loop” or come up with alternate solutions for all this waste. “Closing the Loop” is a method that utilizes the principles of developing a circular economy - an alternative to the traditional linear economy (make, use, dispose), in which we keep resources in use for as long as possible, extract the maximum value from them while in use, then recover and regenerate products and materials at the end of each service life.
Pollima Furniture company has come up with another use for all this waste, making it the world’s first CO2-negative furniture company. Pollima prevents the digestion or incineration of cannabis, hemp, and other plant by-products and therefore keeps greenhouse gas emissions from entering the atmosphere. By then using a hydraulic press powered by renewable energy, the plant waste is given new life as it is formed into furniture that is usable in any home or office.
Conclusion
In our everyday lives, we often take for granted the processes required for receiving items on our doorstep within a few days time, or going down the street to select food from a market with stockpiles of different items. Sometimes we even think carefully about what to do with these items when we are finished with them, meticulously selecting the correct bin as we discard an object. Not often though do we think about how the excess materials from manufacturing or agricultural procedures are discarded. Unfortunately, 25% of the waste generated in the United States comes from the Manufacturing Sector, and 21% comes from the Agricultural sector, whereas only 14% comes from Municipal Solid Waste. However, by increasing awareness of these issues and supporting businesses that prioritize sustainability, we can reduce landfill and incineration emissions, reduce landfill waste overall, improve general land use, and progress towards a circular economy. The waste generated from cultivating cannabis is just one area where creative solutions have already begun to manifest.