Nursery Industry Explores Biodegradable Containers

Posted by on May 31, 2010

Plastic containers revolutionized plant production. Now a significant percentage of plants are grown in some type of container. At the retail level, containers not only hold plants and soil, but they have become a visual part of the marketing.

Yet, environmental concerns increased with plastic products, both in how they are made and how they become a waste stream. So, container manufacturers began to look at other materials. The challenge was to find materials that could contain the soil and plants as they moved through the production and marketing system, yet breakdown after they were used, usually in composting systems.

Numerous substrates are being used and tested to create a range of biodegradable pots including waste paper, peat, coir, cornstarch resins, wheat, bamboo, and even cow manure.

Finding plastic replacements for containers has become an important research topic, with the American Nursery and Landscape Association (ANLA) starting research several years ago to identify useful container substrates (see below). The key challenge is finding compounds and resins that, when combined, will stand up to normal environmental pressures.

“We need materials that will stand up to the south’s warmer temperatures, heavy irrigation schedules, and high levels of nitrogen,” explained Agricultural Research Service horticulturist Donna Fare. She said these environmental factors work together to break down non-plastic pots in the field. Fare is heading up the ANLA-sponsored research project in McMinnville, Tennessee, which will finally test a chicken-feather based container during this year’s growing season.

Recycled Plastic a First Option
Many nursery container producers have morphed from using virgin plastic to using recycled materials. This is a major step toward sustainability, since it at least recovers the plastic already in use in the nursery industry, plus absorbing some of the consumer waste stream.
For instance, ITML Horticultural Products Inc. has a line of recycled containers, called Elite and Euro System Nursery Containers, made with “100% recycled, indestructible polyethylene material.”

Another example is the Root Pouch containers from Averna and Associates. These pouches are made from polyethylene terephthalate (PETE), which comes from recycled plastic beverage bottles, which are turned into non-woven fabric. It is used to manufacture a full line of nursery containers including propagation liners and various sizes of plantable pouches, available in different densities and degradable life spans.

Finally there are oxo-biodegradable products, which I have not found yet in the industry. Wikipedia defined the plastic as follows:

Oxo Biodegradable (OBD) plastic is polyolefin plastic to which has been added very small (catalytic) amounts of metal salts. These catalyze the natural degradation process to speed it up so that the OBD plastic will degrade when subject to environmental conditions to produce to water, carbon dioxide and biomass. The process is shortened from hundreds of years to months for degradation and thereafter biodegradation depends on the micro-organisms in the environment.” I am going to look into this more, so keep reading.

What are Biodegradable Containers?

While there are differences between aerobic and anaerobic degradation, “biodegradable” is usually considered as a material can be broken down into its organic components. Essentially, biodegradable materials avoid increasing landfills by eventually returning them to the soil through effective composting.

As a note, the “effective composting” is a key step to making any of these containers actually biodegradable. In fact, some national and international standards have stricter criteria, defining compostable as having three requirements:

• First, again they must “biodegrade” which is defined as “breaking down into carbon dioxide, water and bio mass.”
• Secondly, they must “disintegrate,” so after three months of composting and subsequent sifting through a 2 mm sieve, there is no more than 10% residue remaining.
• Finally, no “eco toxicity,” so the bio-degradation does not produce any toxic material and the compost can sustain plant growth.

Unfortunately, these global standards exist to certify compostable plastics (ASTM D6400) and compostable packaging (ASTM D6868), under controlled composting conditions typically found only at industrial composting facilities. It is uncertain whether many of these new “plastics” will degrade quickly and effectively in standard landfills or backyard compost bins.

Molded Fiber Early Option

But, many decades ago, molded pulp or fiber first found uses in the horticulture industry. Molded pulp products are made from natural cellulose fibers, including waste papers and peat, and are biodegradable breaking down in compost systems and most landfills. These molded fiber products, were often used in early propagation stages in combination with rigid plastic trays.

But, as plants moved into gallon sizes, most growers continue to use plastic pots, especially if they are shipping plants. The early fiber pots were just not rigid enough to withstand damage during handling.

One of the earlier producers of non-plastic containers was active here in Oregon…Western Pulp Products. The company has more than a 50-year history of making containers using waste paper, collected by charitable organizations (“post-consumer”), while other sources are “pre-consumer,” including Kraft, waxed, and other waste paper. Only the metal rings and hanging wires are not decomposable.

“Even the wax paraffin used to bind the pulp will degrade during composting or in the soil,” said sales manager Jim Lee

While their products are not considered “organic,” they can be used to grow organic plants, according to Lee. He said their growers received approval from Oregon Tilth that organic vegetable transplants can be grown in their molded fiber containers but the plant must be removed from the container before it is planted in the soil. 


Jiffy pots are another decade-old name in nursery containers, entering the market in the mid-1950’s. The George Ball Company bought the U.S. rights from the Norwegian firm that developed the technology. They found numerous uses in nursery propagation, becoming a standard tool for growing plants. But, again, they tended to be too fragile for field and shipping uses.

Wide Range of Substrates Now Available
Many of the newer biodegradable containers are actually manufactured by processes similar to the Western Pulp method…a plant based substrate held together with a binding agent. The choice for substrates continues to expand.

One example are the Fertil biodegradable plant pots, made from 100% natural biodegradable wood fibers, composing 80% of the substrate, plus 20% peat moss. Meanwhile, Summit Plastics Company has a biodegradable line, “Eco 360,” that features containers made of corn, wheat and wood fibers.

Another company, T & R, Woodburn, Oregon, is offering a new line of containers called Ecotainable®. Manufactured by Kelmar’s Creations, the products use ‘patented’ bioresin materials, made from wheat, tapioca, potato starches and corn, to form pots and other products.

CoCo Coir Pot, made by Green Neem, is a biodegradable cultivation pot made of coconut fibers, which have exceptionally high permeability to water, air and roots. Coir products are now available through several companies.

Cow Pots is taking a different approach, using “odor-free, 100% composted cow manure” as the substrate. They claim the manure also adds more nutrition when the plant is growing or transplanted.

Fungi Grows Containers
A radically different approach is the EcoCradle products.
The new product is made from agricultural byproducts including cottonseed hulls, buckwheat hulls and rice husk that are mixed with a filamentous fungi — mycelium — as a bonding agent — and allowed to grow inside molds. The mycelium secretes an enzyme that decomposes the organic waste as it grows. After seven days at room temperature in the dark, a compact, ultra light, malleable material is formed that can resist high temperatures, according to company literature.

Downsides?
While there is an increasing availability of alternative containers, most nurseries have been slow to switch from plastic. Even Northwoods Nursery, Molalla, Oregon, well known for its many sustainable efforts, is still using plastic pots.

“We are just not sure they will hold up over a longer time frame,” said Laura O’Leary, sustainable director for Northwoods. While the nursery has implemented other “sustainable practices,” including recycling plastic containers, they are still holding back on moving to these newer options, she said. Like many nurseries, they plan to test new products, hoping to find products that prove tough.

In addition to needing perfect conditions to decompose, some manufacturers are also cautioning consumers that the pots need to be handle correctly when planting to avoid problems.

For example, Bonnie Plants, uses biodegradable pots extensively, with the smaller versions made by Jiffy. They listed the following rules for using their pots:
• To ensure success, drench the pots thoroughly just before planting.
• Remove the shrink-wrap label from the rim of the pot by cutting it with scissors.
• Also tear away the top of the pot so that the rim is not exposed above ground after planting. If the pot dries out, it can rob moisture from the roots when capillary action pulls water up to the dry rim.
• Finally, tear away the bottom half of the pot before placing the plant in its hole to exposes some roots to direct contact with the soil.

Like any new technology, biodegradable containers will need further refinement and testing to create products that growers will use confidently, especially if plants are shipped.

While there are ongoing research projects (see above) testing how well plants grow in these non-plastic choices, work done over a decade ago showed that plants would grow as well, or better, in biodegradable pots. So, it seems that chief concern remains durability. Once that is solved, biodegradable products could have a bright future in the nursery industry.

You can continue to follow this topic here. I am convinced that we will find more and more organic “waste” products that can be turned into various compostable or plantable pots and containers. Ultimately, they will prove their economic advantage.

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