For a lot of us, the day begins only once that first sip of coffee has reached our lips. Recently, it has been noted that the mechanism for brewing coffee and other warm beverages has shifted from the traditional drip-method to a more modern avenue of single-serve machines. These devices, although convenient, produce insurmountable plastic waste which ends up in landfills every year that is becoming expensive and restrictive due to several mandates and bans. Being an avid coffee drinker myself and coming from a culture that embraces coffee with pure delight in the form of filter coffee, I have always been interested in understanding the overlap between a sustainable lifestyle and a delectable habit such as this.
As I embarked on a tour of the composting site at the University of Tennessee, Knoxville in late-March of 2018 hosted by the Sustainability Office, the idea for a biocomposite composting experiment came to mind. This is a large plot of land that collects garden/landscaping and dining waste throughout campus daily to produce compost using the windrow systems which then gets recirculated onto the campus farms and gardens. Generally, it takes close to 3 months for mature compost to be produced from a fresh pile.
Fun fact about this site: it all started by using coffee grounds from the university!
Since our lab was involved in novel biocomposite projects at the time, I was keen on seeking answers with respect to the environmental toll of these products, the idea of potentially measuring the degradation rates of some of the biocomposites that are produced through several manufacturing routes and cross-referencing the mound composition within this industrial-scale composting facility. Alongside this, due to readily available used compostable coffee pods, I thought it would be a fun activity to toss in a few into the mounds to see how long they would take to break down. Little did I know then that it would lead to a paper of its own and I would never again take another cup of coffee for granted.
Our experiments showed complete degradation of these Biodegradable Products Institute (BPI) certified compostable coffee pods within 46 days proving to be a feasible and effective waste stream. The next step was to understand the environmental impact of this new trend.
Anyone working in the field of sustainability knows all too well that there is no one-size-fits-all solution to issues faced by both people and the planet. For this specific case, a life cycle assessment (LCA) was chosen as the methodology of evaluation wherein the environmental impacts of both plastic and compostable coffee pods were assessed using a hybrid approach. This incorporated empirical inputs, information from the university sustainability office, databases such as Ecoinvent 3.4 and US-EI 2.2, and previously published scientific work regarding materials and processes involved in the production of each type of coffee pod. Exploring the Cumulative Energy Demand (CED) methodology for embodied energy and ten other impact categories (global warming potential [GWP], acidification, eutrophication, etc.) from the Tool for the Reduction and Assessment of Chemical and other Environmental Impacts (TRACI) method, comparison of conventional plastic pods versus compostable ones along the supply chain on a per pod as well as annual consumption basis were uncovered.
It was estimated that the university currently consumes about 750 plastic pods per day. Considering the academic calendar when classes are in session, this translates to an annual consumption of about 112,500 pods (562,500 in 5 years). After rigorous analysis, it was found that the embodied energy of landfilling compostable pods was higher than those of the plastic pods while considering the entire life cycle (including disposal) of the compostable pods. However, while looking at the ten other environmental impacts from TRACI, the compostable coffee pods fared best while considering the composting route. Additionally, a 21% savings in terms of waste disposal was realized in addition to value-added nutrient-rich compost being recirculated onto campus gardens and farms at the end of every cycle. This showed that composting compostable pods used in single-serve machines within the university campus had significantly less impact on the environment. This analysis also sheds light on avoiding burden shifting caused by using a single-issue method for decision making. The values mentioned are low estimates and follow the allocation by mass approach.
We proceeded with a variety of sensitivity analyses for possible alternative outcomes looking at transportation distances while considering procurement distances (0 mi, 250 mi, 500 mi, 733 mi, and 1000 mi), end-of-life (EOL) ratios between landfilling and successful composting (0%, 20%, 50%, 80%, and 100%) and other parameters including projected wet weight scenarios wherein interesting conclusions were inferred. We invite you to peruse these results within each scenario from our paper, which can be found here.
The authors would like to extend our gratitude to the composting team at the University of Tennessee, Knoxville for allowing us to conduct experiments over the span of the entire summer of 2018 on top of the excellent upkeep of the industrial-scale composting facility on a daily basis. We also thank the LCA certified consultants from WAP Sustainability, Chattanooga who conducted a detailed external critical review prior to journal submission and are grateful to our colleagues from the Fibers and Composites Manufacturing Facility (FCMF), Institute for Advanced Composites Manufacturing Innovation (IACMI), and Oak Ridge National Laboratory (ORNL) for their help and support throughout the execution of this project.
A video on some of the work conducted during the summer of 2018 may be found here.