Do Compostable Bags Really Work?

Photo: ACE Solid Waste/flickr.

If you feed them, they will come. Microbes, that is, and by the billions. These good-guy bacteria are a gardener’s best friend because they inhabit and enrich the soil.

One way to feed them is by tossing a compostable bag of kitchen scraps or yard trimmings onto your compost pile. A compostable bag? Will it make it to the compost pile before the bag splits from the moisture or weight of the contents?

There was a time when fears that a compostable bag might rip wide open at the worst possible time were justified. But not anymore. Developments in composition and design technology have improved the strength and degradability of compostable bags for kitchen and yard waste — and even for your pooch, but you don't want to use this last type in your edible garden compost.

BioBag Technology

“There is a dramatic difference from the first flimsy bags that didn’t have a lot of strength to the really strong bags that are available today,” said Jennifer Wagner, marketing director for BioBag USA in Palm Harbor, Fla. With offices in 20 countries and production facilities in Europe and the United States, BioBag is the world’s largest brand of certified compostable bags and film for the collection of organic waste for the purpose of composting.

The new technology that makes BioBags strong includes the advancement of new and more durable grades of compostable resins, the temperature at which the bags are sealed and the design of the bags, Wagner said. Another key feature of BioBags is that they don’t require anything more than what already exists in an active compost pile to break down.

The bags decompose because microorganisms eat and digest the materials the bags are made from. It’s the digestive process that helps to create heat in the compost pile. The materials in the bags that allow microbial organisms to eat them include plants, vegetable oils and a compostable resin sourced in Italy called Mater-Bi, the world’s first bio-polymer made from corn. The corn in most Mater-Bi grades is not of a genetically modified variety, Wagner said.

The more active you can keep your compost pile, said Wagner, the more microbial organisms you will attract. “The higher the rate of active microbes, the quicker the bags and ingredients in the compost pile will break down,” she added.

90 Days to Decomposition

BioBag products meet European home compost standards, which means they will completely degrade in 90 days in a compost pile that maintains a minimum temperature of 45 degrees Celsius (113 Fahrenheit), Wagner said. The United States does not have home compost standards, only commercial standards — although the generally accepted ideal internal temperature for the center of an active compost pile is between 90 degrees and 140 degrees Fahrenheit. To reach that temperature, a compost pile should be at least 3 feet tall, 3 feet wide and 3 feet deep, have a mixture of green material (such as grass clippings and food scraps) to supply nitrogen, brown material (leaves, small branches) to add carbon, have adequate moisture levels and be turned over on a regular basis to give the contents access to oxygen.

While the decomposition of food scraps and yard waste in an out-of-the-way compost bin in the back yard may be quite acceptable to many people, placing food scraps in a bag in the kitchen and leaving them there for a few days might create an “ick” factor for those who set limits on how organic they are willing to be. “Ick” in this case refers to the molds, mildews and unpleasant smells that happen when plastic bags trap moisture and gases from decaying kitchen scraps. The natural material of BioBags, however, allows them to “breathe,” which releases moisture and gases and reduces unwanted side effects.

Not Accepted Everywhere

There’s also an uh-oh factor. Not all communities have Source Separate Organics collection systems and not all of those that have SSO systems accept food waste for composting, Wagner said. “Of the SSO programs that do exist across the nation, only 79 percent of those allow compostable bags,” she added.

Good for Yard Waste

Compostable bags are also a good option for yard waste, whether they are destined for the compost bin or curbside pick up. Polyethylene bags are not an ideal choice for this purpose because many communities that collect and compost lawn trimmings, leaves and small branches have banned them for yard waste. Polypropylene and polyethylene were invented in the 1950s, Wagner said. They began showing up in sandwich bags, produce bags, cleaning bags and garbage bags in the ’50s and ’60s, she added. But, she pointed out, no matter how those first plastic bags were disposed of, they are still around. “Plastic lasts forever,” she said. “Their purpose is their problem.”

Compostable bags designed to hold yard waste are also more environmentally friendly than large paper bags frequently seen along neighborhood curbs. There are several reasons for that. One is that they weigh less than their paper counterparts and consume less energy to transport and decompose. For another, in the case of BioBag, they contribute less to global warming because of the natural renewable ingredients in the raw materials of the Mater-Bi.

Other Brands of Compostable and Degradable Bags

Other brands for residential use include If You Care, Natur Bag, EcoSafe and Bag to Nature. The way to identify compostable bags that will completely degrade is to look for a label on the product packaging that says COMPOSTABLE, BPI, US Composting Council.

Where to Learn More

The Biodegradable Products Institute is a nonprofit certifying organization for compostability that uses its label program to educate manufacturers, legislators and consumers about scientifically based standards for compostable materials that biodegrade in large composting facilities. BPI also promotes the use and recovery of compostable materials though municipal composting.

One of the ways they do that is by directing consumers to the “find a composter” website, which BPI sponsors. The site is a free directory of composting facilities throughout North America that was created and is managed by BioCycle magazine.

You can use the site to find out where to donate or buy organic compost. Either way — and especially if you make your own — composting is an excellent way to make billions of new microbial friends.