How can managed composting keep “renewable” materials out of landfills?

In a cradle-to-cradle viewpoint, sustainable-material flows are divided into two systems: biological or technical metabolisms. A unique characteristic of many renewable materials is that they can be recycled (technically recovered) or composted (biologically recovered). This gives renewable materials a broad array of post-use options not shared by many materials such as plastics or metals.

There is increasing interest in the managed composting of organic and renewable materials. In the US, landfills are one the most significant man-made sources of greenhouse-gas emissions due to the anaerobic decomposition of biodegradable materials (primarily vegetation and food). While studies have revealed that landfills tend to be tombs rather than composting reactors, these studies have also found that wet, readily degradable materials tend to decompose rapidly, resulting in the release of methane—a greenhouse gas 21 times more potent than carbon dioxide. As a consequence, the diversion of wet, organic materials will likely become an important area of focus as the US considers how to reduce its greenhouse-gas emissions. The City of San Francisco already has an aggressive managed-composting program to divert organic waste from landfills. The resulting compost is used for local agriculture. Several European countries are also pursuing managed composting.

The introduction of bioplastics has helped to catalyze the discussion of composting within the packaging community. Along with wet, organic wastes, packaging made from renewable and compostable materials will be a likely candidate for landfill diversion. Clearly, recycling is a higher-value recovery option for many renewable materials, but foodservice packaging that is often contaminated and not a candidate for recycling can be very suitable for composting as long as it's designed with that end in mind. Designing for composting will be especially important for packaging to ensure that any coatings, inks or other components are suitable and safe for composting systems. Experience to date suggests that beyond certification of compostability (e.g., BPI or DIN CERTCO), commercial composters will require validation that packaging is safe and will not compromise the quality of their compost before they accept it.

Managed composting systems strive to provide the optimal moisture, oxygen and temperature to produce high-quality compost, and as a result, most emissions occur in the form of carbon dioxide. Managed composting—like aerobic biodegradation in nature—allows organic and renewable materials to be recovered in a “carbon-neutral” manner and produce a beneficial soil amendment. Managed composting differs from backyard composting where temperatures do not reach the levels achieved in managed systems. While managed composting is still in its infancy, it's clearly a more sustainable option for the management of renewable materials than allowing the economic and environmental investment made in the creation of these packaging materials to be lost in a landfill.

Resources: www.biocycle.net, www.bpiworld.org, www.compostingcouncil.org, www.dincertco.de