It may not be noticeable to the casual observer — but over the summer, the University of Oregon implemented some changes in how it handles compostable waste.

“We ended the post-consumer collection sites in the EMU and elsewhere on campus,” said Steve Mital, UO director of sustainability. “We still do the pre-consumer compost collection in the kitchens, which is responsible for 70% of all the food waste on campus. The bulk of compostable materials on campus are still being captured.”

Mital explained that the difference in those types of compost produced largely comes down the actual food production process. Pre-consumer items includes items that are “directly food” but are not served (like vegetable cuttings or scraps), while post-consumer items include utensils, bowls, and related, non-food kitchen or tableware items that are labelled as compostable.

Why did this change occur in the first place? Mital said that the steps to back away from post-consumer items came because of a decision by the vendors collecting the compost waste. “They issued an announcement several months ago saying that they could no longer accept all the compostable cups and serviceware and other kinds of packaging that are labeled compostable.”

Related: UO residential dining switches to reusable tableware 

Specifically, an information sheet, published by a number of Oregon compost industry companies and shared with those generating compost, gave nine reasons for why they would no longer be accepting artificial compostable material.

One of the companies attached to the letter, Rexius, is based in Eugene and works with different local entities, including UO, in compost collection. Jack Hoeck, vice president at Rexius, said that a major factor behind the change was the problem of contamination in the compost that facilities received, where regular plastic objects were being mixed in with compostable matter, an issue Hoeck said had been going on for several years.

“What was happening was that there was so much co-mingled, with compostable versus non-compostable — it was a bit like unscrambling an egg,” Hoeck said. “Once it’s all in there, how do you sort it all out?” 

Hoeck said the problem was not limited to a single institution. “This is system wide, not just at the U of O,” Hoeck said. “It was very indicative of what we were finding at restaurants and other generators of this material, so finally we said this doesn’t make a lot of sense. If we didn’t have those compostable items in there, we would be able to identify if something was a contaminant or not.”

Mital said that contamination was a “significant problem” at UO.  “There was just a lot of confusion about compostables, what is and what isn’t, and so single-use straws, wax-lined paper cups, and so many other items would often end up in the compost,” he said.

Related: “Curbside composting comes to Eugene“

An additional reason given by the industry information sheet was that service items certified as compostable don’t necessarily break down. According to the message, “certification standards test compostability based on laboratory conditions. [T]hose conditions are not always replicated in the real world (our facilities) which means that some compostable items don’t fully compost.”

Hoeck said that Rexius didn’t have as much of an issue with non-food compostable items breaking down, but they weren’t wholly necessary to begin with. “Really what we’re after in the organic material. The man-made materials can be broken down, but they really don’t add a lot to our process,” Hoeck said. “Just because we can compost a paper plate doesn’t mean it makes good compost, and it doesn’t really add nutrients.” 

For that compost process to work, Hoeck explained, it was necessary to add organic material to the artificial material in order for it to properly break down as compost.

While Oregon composters have stopped accepting artificial materials, Hoeck said that there are other facilities in the country that take compostable service items.

Ultimately, Hoeck said that the goal is to preserve the integrity of the compost system in general. 

“It’s a pretty good model of sustainability, because [compost] is something used or past its useful life, and it’s taken and transformed into something that’s beneficial for growing plants and food again,” Hoeck said. “That part of it’s awesome. It’s when us humans get involved sometimes and don’t think about or understand or behave properly, it can cause some problems. That’s kind of what we’re addressing.”