Talking Trash 1: Why Sortation Matters

Let’s talk about something everyone produces but nobody really likes – trash. People produce billions of tons of waste annually. While there are many ways to reduce the amount of waste we produce, it is not possible to stop it entirely. Waste is, quite literally, inevitable. The disorder (entropy) in the universe increases with time, which just means that things will always break and there will always be some amount of waste. Once our things become our trash, we have two options: we can dispose of them or we can try to reclaim them as a resource. From a planetary health perspective, there are a lot of reasons to want to reclaim wastes as resources. Unfortunately, it is not easy to do so economically. 

Wastes have three features that make them difficult to use as a resource: they are degraded, diffuse, and/or mixed. First, wastes may be degraded. Examples of this include the strawberries you forgot in the back of the fridge that sprouted fuzzy fungus or your old grill cover that looks like a teenager’s jeans. Degradation also happens to dishes, cars, phones, and really anything that can be broken beyond repair. A second feature of waste is it may be too diffuse. Small pieces of anything that are spread far and wide – bits of plastic, bits of metal, bits of most anything – are expensive to collect for recycling. If the material is of low value, it may be too expensive to collect for recycling. Think about old glass, most of which is not recycled in the United States. Glass tends to break into small pieces as it moves through waste collection processes, it is heavy, and it has relatively low value. The combination of factors makes glass recycling uneconomical in many areas of the United States. The last feature of waste is it is mixed. When different kinds of material are mixed together, they are difficult or impossible to recycle. The upshot is pure materials are a resource while mixed materials are trash. The mixture of things in your trash can are an example. Separate cardboard from aluminum cans and both are valuable resources, leave them mixed and they are not usable. 

Today we are going to focus on mixed wastes. In the recycling business, the process of sorting mixed wastes is called sortation. Without sortation there is no recycling. If sortation can be accomplished at a low enough cost, then much of what ends up in the trash could become a resource. Given the importance of sortation, established firms and startup companies are working to improve sortation so less waste is landfilled and more is recycled.  

The keys to sortation are purity and throughput. Purity is needed so the sorted materials will have economic value as a resource, like in our example of aluminum cans and cardboard. Throughput is necessary for sortation to be affordable. Sorting millions or billions of tons of trash means billions or trillions of individual objects have to be sorted – it’s a huge job! People are certainly capable of sorting trash, and the average person can sort 20 to 40 recyclable objects per minute. However, hand sortation is dirty, dangerous work and is therefore better done by machines. 

Given the importance of sortation, established companies have spent decades developing machines that use the physical properties of wastes – like density, magnetism, and electrical conductivity – to sort wastes. Sortation is also a great application for technologies originally developed for other markets, including artificial intelligence (AI), robotics, advanced sensors, and manufacturing-style automation. Startup companies such as AMP Robotics, Glacier, GreyParrot, and ZenRobotics (acquired by Terex) are doing exciting things with AI and robotics to improve the abysmally low recycling rate for plastics (less than 10% in the US). We are excited by the work at Sortera Technologies and what they are doing to improve the recycling of the metals needed for rapidly expanding industries related to renewable energy and electric vehicles. Sortera’s approach is great for people, planet, and profits – right in our wheelhouse! In our next post, we will dig into scrap metal, an overlooked industry that is critical to the global economy.