Plastic was invented and became so popular and ubiquitous for one main reason:  because it is very durable. This is also why we have a plastic problem today, because plastic products just don’t go bad easily! So does biology and biotechnology really have the potential to solve this conundrum?

Plastics are a recent human invention– recent compared to the far longer history of life on earth. Therefore, most living organisms have not evolved to deal with plastics. However, given how vast and diverse different organisms are, we are optimistic that some organisms would carry some ability to break down plastics, especially bioplastics as many of them are less durable than traditional plastics. Of all types of organisms, microbes are particularly interesting because the number of microbial species present in the world and their diversity is unparalleled compared to other types of organisms. For these reasons, we are currently mining the microbial world for interesting and useful enzymes in the biodegradation of bioplastics. 

For PLA, it is known to be compostable at higher temperatures, which indicates that it is not uncommon for environmental microbes to carry enzymes that can degrade PLA, albeit at less-than-ideal efficiencies. In other words, we can expect to identify microbes from composts that have some reactivity towards PLA which can serve as a great starting point from which we will use bioengineering to substantially improve the biodegradability of microbial strains of PLA. The engineering process also can incorporate additional properties desirable for commercial application of the enzyme. The materials we develop can be used as a supplement in composts or other degradation facilities to achieve high-efficiency PLA breakdown.

Can PLA be composted at home? If one does an internet search on this topic, the overwhelming answer would be: NO! Indeed, PLA is well-known to be compostable at temperatures over 55॰. In comparison, smaller-scale composts oftentimes struggle to reach temperatures higher than 30॰C, a temperature at which barely any composting of PLA is observed.

However, we have found that the ability of home composts to degrade PLA can be trained. Our idea is that by including PLA in our composting feed, over time microbes that can break down PLA at lower temperatures would gradually become more enriched, at which point we would start to be able to observe reasonable levels of PLA break down in home composts. After training our home composts for nearly two years, PLA films put into our compost deteriorate substantially within a month! We are continuing to improve PLA composting efficiency in home composts, and also hope to have a compost supplement available for those who want to compost their PLA at home— this way we know for sure that our PLA waste is disposed of in a sustainable fashion!

Just like lots of things, it took multiple things to align, in our case three things, to kick-start the PLA home-composting project.

More than five years ago, in spite of the highly functional and successful public collection program for kitchen scrap and compostable waste in Taipei City, Dr. Fugmann decided to start our own home compost on the balcony of our 14th floor apartment. It was out of scientific curiosity of trying out city-style home composting and the wish to be completely certain that the organic waste we produced is converted to environmentally friendly and useful secondary material. We were presently surprised that with a pair of small plastic trash bins stacked together, all of our vegetable and fruit scraps were converted into compost for the plants we grew on the balcony.

A few years into our home composting project, products made from compostable bioplastics really started to pop-up in our lives. First came plastic bags with the printed claim that they were compostable. Then at our favorite sandwich shop, the owner told us that they use compostable dining-ware thereby justifying their choice to not offer reusable ones. These incidents alerted us to the increased use of compostable plastic and we realized that more and more plastic trays offered at supermarkets were made with PLA.

Web searches quickly informed us that PLA compostability is highly controversial, thus as curious scientists we did our own experiment by putting PLA products we encountered in our daily lives into our highly productive home composting bin. First we tried PLA plastic bags, and after several months, nothing happened. Then we tried fruit trays from supermarkets. Still absolutely nothing happened after several months, at which point we decided that the rumors were true:  PLA does not degrade in home composts. However, we got lazy and left the PLA tray in there. That’s when the unexpected finding came:  more than a year after the PLA was put into our compost, we realized that the PLA tray had fragmented into lots of smaller pieces, and the pieces that we could still see were quite brittle. We appeared to have made our compost competent in degrading PLA after a long enough time of letting some PLA sit in it!