Mixed waste processing has seen its share of ups and downs since it was first introduced in the United States in the 1970s, but with today’s ever-increasing focus on boosting landfill diversion rates, this somewhat controversial waste management method is once again in the spotlight. Here are eight things you should know about mixed waste processing.
What is mixed waste processing?
As its name implies, mixed waste processing (MWP) is a one-bin system with no source separation. The consumer places all household waste, including recyclables and organics, into a single bin; the combined waste is then taken to what has become known as a “dirty” material recovery facility, where the recyclables are pulled out and processed.
MWP could help boost recycling rates.
A recent report on the evolution of MWP facilities (which was prepared for the Plastics Division of the American Chemistry Council by waste consultants Gershman, Brickner & Bratton, Inc.) states that MWP could have the potential to significantly boost recycling rates, especially for certain materials like specific grades of plastic.
These potential recycling increases are driven by two principal factors. The first is the reduced rate of consumer error. Even households that are conscientious in their recycling habits typically wind up sending at least some recyclables to the landfill along with their household trash. In fact, up to half of the average municipal solid waste stream may be comprised of recyclable commodities. But with MWP, there is no consumer separation of trash and recyclables, and so the risk of recyclables being inadvertently sent to the landfill is greatly reduced.
The second factor is the improved processing technologies that are at currently at work in MWP facilities. For example, new optical sensors now make it possible for particular plastics to be identified, separated, and sorted into distinct groups, meaning that more recyclable commodities are making it to the appropriate final destination for processing than was previously possible with only existing collection systems.
Recyclables recovery wasn’t always the primary focus of MWP.
In fact, according to the report described above, MWP facilities were initially designed to capture waste for energy recovery. In the early days of MWP, recyclables had less value, and so it was the energy recovery potential that became the primary driver of MWP facility development. However, as waste management priorities have shifted, MWP is valued today primarily for its potential recycling benefits.
The arguments for MWP go beyond recycling.
According to experts, there are a number of additional reasons why it makes sense for MWP to be a key waste management strategy for the future. These include the fact that the habits of our “disposable” society do not seem likely to change anytime soon, meaning that greater landfill diversion rates are needed urgently. There’s also the fact that siting and obtaining permits for waste-to-energy facilities, another widely touted solution to our waste issues, is currently very challenging and likely to remain so.
MWP facilities can be combined with existing large materials recovery facilities (MRFs).
Increasing our focus on MWP doesn’t have to involve substantial investments in new sites and facilities. It’s often possible to combine MWP with waste management activities at existing large MRFs, which could have the potential to greatly increase both the volume of recycled materials handled and the revenue generated by those materials, particularly high-value metals and plastics.
MWP is not without challenges.
One of the biggest obstacles to widespread MWP implementation concerns the quality of the recycled materials that are recovered from the waste stream. In particular, the paper industry is concerned that the quality of the feed stocks used in the paper-making process will suffer if recycled paper is not handled separately, but rather is pulled out of a waste stream that contains organics and other potential contaminants. Better data and more case studies are in order to demonstrate the impact that MWP could have on commodity prices, as well as to paint a clearer picture of realistic recovery numbers.
Low consumer involvement in MWP has pros and cons.
While there are fewer chances for consumers to make recycling mistakes with MWP, this low level of consumer participation could prove to be a double-edged sword, as it removes the opportunity to educate consumers on the consequences of their consumption habits and waste and recycling choices.
MWP has its limitations, but it’s nevertheless an important tool.
Even strong MWP advocates are not arguing that this waste management method is the only one we need. Rather, most experts agree that MWP would work most effectively in collaboration with a landfill or a waste-to-energy facility, allowing for a final sorting of municipal solid waste to recover the maximum possible value of recyclables prior to the ultimate disposal method. By covering the gaps that existing methods miss on their own, this type of combined approach could make a significant contribution to more sustainable management of post-use materials.