APRA has welcomed the University of Calgary as a new member. Researchers from the U of C are focused on plastics projects. The articles below summarize the research being proposed. APRA and the U of C welcome members to share their expertise and interest in joining one of these projects. Please reach out to APRA, Giovanni or Milana to find out how you can get involved.
Towards microplastic-free waste recycling
Lead by Giovanni Natale
Giovanni and his team are tackling microplastics to help stop contaminants in the environment. Giovanni is seeking experts in plastic recycling and wastewater treatment to join the team’s efforts by becoming part of an advisory/steering committee for this program. Please reach out to gnatale@ucalgary.ca
The recycling of plastics is a process that includes mechanical, thermal and chemical stresses. Shredded plastics go through prewash and multiple friction washer stages followed by centrifugation and/or hydrocyclone separation. The process can include thermal cycling/drying and solvents/additives. Mechanical recycling, a common method in post-consumer recycling, involves cleaning and sorting plastic waste followed by processes like size reduction, extrusion, and granulation to produce feedstocks for downstream chemical processes. Recent and surprisingly alarming reports (Altieri et al, Brown et al. ) indicate that the resulting plastic recycling process stream is a complex matrix containing microplastics (MPs) from various sources and generated through multiple degradation mechanisms, organic matter (e.g., food, bacteria, organic compounds) as well as potential toxins, drugs and forever chemicals. Standard filtration processes do not capture MPs below 5 µm. In plastic recycling facilities, MPs released into the environment can make up to 5% by mass of the total plastic processed. For one recycling facility, this can account for an alarming 50 to 1,000 tonnes per year of MPs going into the receiving waterway, considering an average of 20,000 tonnes per year of plastic treated. At the same time, municipalities struggle to maintain biosolids and, thus, compost free of plastics because of human error or ineffective public education or policies. During compost processing, biological, thermal and mechanical degradation of plastics can produce in situ MPs, which are difficult to detect, quantify and eliminate (Porterfield et al., Gui et al.). Here, we propose a comprehensive transdisciplinary approach to develop technologies to prevent, detect, remove and degrade MPs in waste recycling processes. The suite of novel technologies is thought with in mind the complexities of such process streams and is focused on selectivity and scalability.
The detection and capturing of MPs in waste recycling process streams (e.g., plastic recycling, composting) is a multifactorial challenge. Process streams often contain a wide range of MPs with different sizes, shapes, densities, and compositions, making it challenging to develop universal separation methods. In addition, MP contamination will interfere with the detection and separation of the MP surfaces with standard gravimetrical or coagulation-based technologies. Addressing these limitations requires the development of novel specialized and scalable separation methods. For plastic recycling processes, we propose two technologies to treat MPs in the process stream:
1. The first is based on a nanobubble-based separation technology. The second is a biological route based on the engineering of isogenic strains to selectively target MPs as a nutrient source. Thus, a biofilm-based floatation process is proposed by tuning biomass production.
2. In parallel, bacterial engineering is employed to develop novel methods for the degradation of MPs in solid matrices, such as during composting. Multi-microbial interactions and social behaviour need to be accounted for to accelerate these processes in real systems.
The transdisciplinary approach described tackles MPs in waste recycling process streams by a) determining the mechanisms of their formation and identifying preventing methodologies in waste recycling, b) exploring novel molecular technologies and derivative processes with high specificity to trace and remove MPs from process streams and c) developing novel microwave-based platforms to analyze in real-time presence and chemistry of the MPs in process streams. In parallel to the technological development described, a stream of research is dedicated to policy development around MPs and waste recycling based on the anticipated discoveries.
These efforts will help remove MPs and micropollutants in waste recycling, inform policy development and educate communities via outreach activities. Combating this societal problem is imperative for environmental and human health.
Enhancing Safety of Food-Grade Recycled Plastics with AI Augmented Advanced Sensing Technologies
Milana Trifkovic and her team are working on a project to improve the quality and safety of food-grade recycled plastics. Milana is looking for end-users of recycled food-grade plastics to collaborate on the project. Reach out to mtrifkov@ucalgary.ca
Contamination from food residues is a significant concern for food-grade recycled plastics, as it can pose health risks if the recycled plastic is used to package new food products. Surface contaminants can promote microbial growth, spoilage, and certain contaminants may embed in the plastic matrix, leaching into food during reuse. To ensure safety, recycled food-grade plastics must meet strict regulatory standards. These standards require thorough cleaning and processing to minimize contamination risks. However, achieving consistent purity can be challenging, especially when dealing with mixed or poorly sorted waste streams. As a result, most of the recycling efforts in Canada focus on non-food-grade plastics, with a few exceptions like beverage containers made out of PET where food-grade recycling is more feasible.
The core innovation is the development of cost-effective sensing technologies, augmented with artificial intelligence (AI) and machine learning (ML) to effectively sort different food-grade plastics, but also properly assess contaminants from food residues prior to the cleaning steps and effectiveness of their removal by current common practices. This includes the creation of an economical online Raman spectroscopy tool, developed in collaboration with Anton Paar, a leader in the field. Additionally, the program will integrate microwave-based sensing technology from UCalgary. Existing methods like near-infrared (NIR) spectroscopy and X-ray fluorescence (XRF) will serve as benchmarks for surface and bulk characterization, while with high-speed cameras providing further data by capturing visual markers such as color and watermarks. These sensing tools will be augmented with AI/ML to significantly boost sorting accuracy and efficiency.
The outputs of the thorough characterization will serve as a base to develop life cycle model assessing the economic and environmental impacts of the different options throughout the sorting process such as extent of separation, food residue amount present before and after cleaning cycles, advise on the strategy to achieve optimal economic and environmental outcomes.
The project objectives include quantification of residual food contaminants; impact of microbial growth on the permeability and integrity of food-grade plastics in recycling; quality of recycled/washed food-grade plastics; life cycle assessment; and developing of online sensing technologies with AI/ML models.
Given the limited information on the removal of food-grade residues from food-grade recycled plastics in Canada, we believe this study will be the first publicly available research to establish best practices for ensuring public health safety.