Good question (and same text formatting..) - the modeling depends on what you want to express. A waste flow is something you want to get rid of, treating it / consuming it is a benefit. A recyclate is maybe more typically a by-product, if a process has that as output, model it as a product (and apply allocation as the process that has it as output becomes multifunctional then). Often, you will have a mixed waste stream that is indeed waste, but once it is treated, sorted, ... you will get reyclates that are useful inputs in a production process, and in this case, the waste treatment process that has these recyclates as ouput is also multifunctional, as it treats waste (a waste flow as input) and produces products (the recyclates) as output. You can also apply allocation then. All clear 
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