At Sun & Swell, we are not just passionate about compostable packaging, but we're also curious about what happens to our packaging after use. We want to understand what goes on at an industrial compost facility, so our Head of Sustainability, Kate, went to tour two facilities to learn more. Read on to learn about what goes on at an industrial composting facility.
First, we want to emphasize how cool composting facilities are! They essentially take organic materials (food scraps, yard waste, and compostable packaging) and turn it into something that we desperately need and that can actually be sold on the market as a product: nutrient-rich soil. Disposal of waste is a big issue in the US and the world alike. Organic materials make up 56% of municipal solid waste (source) and currently a majority of that goes straight to landfill where it emits methane (a potent greenhouse gas) and takes up space (i.e. land clearing for landfills). If this organic waste could instead be composted, this waste could be diverted from landfills and instead turned into products that can be used to enrich soil. Whether you’re composting in your backyard or sending it to an industrial composting facility, there are numerous environmental benefits of composting.
What is industrial composting?
Composting is where organic materials naturally decompose in a controlled environment. The biological processes are the same whether it’s a home compost or an industrial compost and the same main principles hold like the temperature, moisture levels, and carbon to nitrogen ratio.
Industrial composting facilities can handle large amounts of waste, versus the amount of organic material you could process in your backyard compost. Industrial methods can help slow the growth of landfills, cut down on greenhouse gasses, and reduce the need for chemical fertilizers. They are an essential step toward combating climate change.
3 types of industrial composting:
Windrow: Organic material are collected and arranged in long rows. These piles must be regularly mixed in order to be exposed to oxygen, moisture, and heat. This process can produce fertile soil in bulk and the timelines is around 4 months.
Static Pile Composting: This method works by mixing organic materials with debris like wood chips or paper. Piles are occasionally mixed and turned and some facilities opt to aerate the piles with pipes to get oxygen to different layers of the pile. This process takes around 3 months, however it doesn’t work well with grease or animal byproducts so they have to spend more time sorting beforehand. This process can also be covered (CASP) where there is more control and less air pollution.
In-Vessel Composting: In this method, organic materials are first shredded and mixed, then they get deposited into a commercial composting machine. This machine controls temperature, hydration, and aeration. It can also rotate and churn the composition to ensure that every part decomposes at the same rate.
Through an in-depth tour of two different facilities with two different methods of composting, Kate learned so much about the process and what goes on day-to-day at these composting facilities.
At both facilities the general outline went as follows: waste is dropped off at the site by haulers, it then goes to a Materials Recovery Facility (MRF) to get sorted. From there, compostable materials (organics etc.) are sent to some form of decomposition site. Finally, the end product (compost!) is ready to be sold and used again as an input into another system. Full circularity!
At the first site, the sorting was done manually by workers who organized it into categories of compostable, recyclable, and destined for landfill. From here the organics and compostable materials got sent to windrow piles, where they were turned and watered at least once a week to provide aeration, mixing, and proper moisture and temperatures. After about 5-10 weeks the organic waste is naturally composted by microorganisms and the compost is ready. It is then sold to local organic farmers in the area as well as used in Turf Rescue, the first biochar-based, compost blended amendment, specifically formulated to reduce the water needs for lawns and turf.
At the second facility, they had a brand new Material Recovery Facility that used technology called the Trom Screen which separates heavy from light waste, and smaller items from larger items to sort the waste brought in. The waste got sorted into recycling, compost, and landfill categories by weight. Currently plastics #1 and #2, dry and clean cardboard, and dry and clean paper, glass, and metals are being sorted out at the Materials Recovery Facility (MRF) and collected for recycling. All organic materials, including wet paper (used paper towels, too!), food scraps, plant material that can't go in green waste, and wet cardboard, are getting pulled out to be composted. Next is the optical sorter which is used for the trash and recyclables. Each has a different material goal related to size, type, and color.
Next, the organics are sorted out and moved to the anaerobic digester. Here they were put through a cycle where the organic broke down in a sealed environment without oxygen. Methane gas is released from this breakdown and then captured and used as an energy source to power the facilities and neighboring communities. The other end product from this process, digestate, was brought out of the sealed vessels and organized into long piles where it dried out and any glass or other materials were sorted out. During the drying process it loses up to 50% of its moisture content. After this what is left is compost and it can be sold and used in the community.
One of the most eye-opening parts of the tour was actually just seeing the amount of waste that goes to the facility. At one point our tour guide mentioned that the large slope behind us was all landfilled trash that was buried and he said that this landfill only had around 10 years left before it was full and couldn't be used anymore. Then our trash will have to go somewhere else. It really made us think about the way in which our linear economy works. Where we just use things once and throw them away. Sadly "away" actually just means buried in the ground. It also brought to life the huge importance of composting. If we can divert large amounts of waste from the landfill to be composted, this will save space and prevent methane from being produced. We are so grateful we got to learn more about the composting process at these facilities and understand the end-of-life of waste a bit more.