Circular Economy: Symbiotic Recycling of Consumer Products

Start Date: 
Sep 1, 2017
End Date: 
Aug 31, 2020
Summary: 

We will study the value stream, distribution points, and social incentives for consumer participation to define a collection network for optimal recovery. We will solve a key AHP recycling road-block, SAP recycling via de-polymerization and re-polymerization. We will define consumer recycling drivers, develop waste-to-energy (WTE) factors for an effective value proposition, and develop advance chemical methods to facilitate SAP recycling. We will: a) demonstrate de-polymerization of model and real SAP materials, b) identify energy/material handling requirements for critical catalysis and WTE systems, and c) understand motivations/detractions from consumer recycling.

The idea of a circular economy, a system where linear production to disposal is shifted instead towards re-use and regeneration, has placed focus on single-use consumer products. In particular, single-use consumer products like absorbent hygiene products (AHPs), which include baby diapers, feminine protection pads, and adult incontinence pads, pose unique challenges to municipal solid waste systems and consume considerable resources. These products, which typically contain combinations of polypropylene, polyethylene, elastics, cellulose, and superabsorbent polymers (SAPs), emit more greenhouse gases than 1.5 million EU households combined each year. The SAPs in these products are of particular importance as they have been reported to make up over one third of the total mass of AHPs and contribute substantially to the environmental impacts.

Partial recycling of AHPs like baby diapers has been achieved with mixed success by a handful of companies. However, these recycling technologies typically aim to reduce ends-of-life impacts, thus neglecting the biggest impacts in the life cycle. Therefore, I aim to shed light on how we might lessen the impacts at the beginning of the life cycle by focusing on theoretical SAP recovery. My research analyzes the environmental and social trade-offs associated with AHP waste under the following three scenarios: 1) current standard diaper disposal via landfill or incineration in a standardized European context, 2) diaper recycling without recovery of the SAP and 3) recycling with theoretical recovery of the SAP. Environmental impacts of these scenarios were modeled in the LCA software SimaPro and social impacts were modeled in the open source software OpenLCA using the Product Social Impact LCA (PSILCA) database and supported by literature. Results show that theoretical SAP recovery decreases life cycle emissions significantly compared to standard landfilling and incineration and moderately when compared to current recycling technologies. Theoretical SAP recovery also demonstrates large potential offsets of energy and water burdens involved in SAP manufacturing. By assessing these environmental impacts and integrating the social analysis, I clarify the point at which AHP disposal demonstrates potential for circular economy.

Sponsor: 
Procter & Gamble