Landfill black goo: What is this stuff and what can we do about it?

Webinar Summary
Black, sticky, gel-like matter, aka black goo, has been accumulating in leachate collection systems (granular layers, pumps, pipes, tanks, etc.) in municipal solid waste landfills causing extensive and costly clogging problems. This clogging material, which is distinctly different from conventional biomass, emerged in North America over the last decade and is now commonplace and problematic. Black goo has also been observed in several south American countries, and most recently in central and western Europe. Black goo clogs pipes, drainage layers, sumps, and pumps, requiring costly maintenance and making leachate extraction inefficient. To understand this phenomenon, black goo samples were collected from more than 20 landfills in North America and Europe. Each was analyzed by Fourier-transform infrared (FTIR) spectroscopy and solid-state nuclear magnetic resonance (ssNMR) to examine their chemical structure. Loss on ignition (LOI) and thermogravimetric analysis (TGA) were used to determine organic matter content and to compare black goos to conventional biomass. Scanning electron microscopy (SEM) was used to examine morphological characteristics of the black goo samples. The analyses indicate that black goos are primarily composed of superabsorbent polymers (SAPs) used in a variety consumer and industrial products (e.g., diapers, feminine products, incontinence products, water stop, paint hardener), which are ubiquitous in the waste stream. SAPs dissolve in leachate draining down through the warm waste, and coalesce in cooler low-energy environments such as the floor of a cell, in a sump, in saturated degraded waste, and in storage tanks. Because SAPs are ubiquitous in the waste stream, black goos are likely to become an increasingly significant problem. Management strategies include landfill designs that promote higher flow velocities in the leachate collection system and periodic flushing with warm solutions and reagents that can degrade SAPs.