November 15, 2011
By Jen Llewellyn
OMAFRA Nursery Crops Specialist

Mahendra Thimmanagari
OMAFRA Crop Bioproducts Specialist

The Ontario nursery industry is the largest in Canada, representing 44 per cent of the total farm gate sales of nursery stock in the country, with a total growing area of around 23,525 acres.
Estimates show one-third of this area is devoted to container production.
The Ontario nursery industry has actively participated in plastic recycling programs for containers, poly films, trays, wraps, bags, etc., in an attempt to reduce the amount of waste plastic in landfills.
Some wholesale nurseries, horticultural suppliers and garden centres are also providing collection depots.
Several growers are presently experimenting with bio-based containers to reduce the impact of production on the environment.
Fibre-based materials such as coconut coir and rice hulls are used to manufacture biodegradable containers for the nursery and greenhouse sector. Several pot suppliers offer biodegradable pots that are really catching on in some product lines.
Let’s take a moment to review the terminology for various bio-based products in the industry:
  • Bio-based refers to products made with some component of biological, or organic renewable materials, such as crops and crop residues, grasses, and wood fibres.
  • Biodegradable container material is broken down through a biological microbial process (bacteria, fungi). Under natural conditions, it can take several months to years to break down.
  • Compostable is a process similar to biodegradation, but it occurs under specific composting conditions (temperature, O2, CO2) and therefore takes a shorter time (six to eight months in commercial operations).
 Compostable plastic products must meet the standards, ASTM D6400, or ASTM D6868, to be labelled as compostable.
Some nursery growers have been trialling coconut coir pots (imported from Asia).
These coir pots can last two to three years in outdoor production and still maintain their integrity and natural look. One of the advantages of the porous coir pot is the additional air in the root zone. Growers have seen a significant increase in the amount of fibrous roots for several species of trees grown in coir pots, compared to smooth-walled plastic pots. This increased root mass is a huge boost for plant quality and out-planting success and can make up for the added cost.
Make sure the pot you choose is appropriate for the length of time that crop will be in production.
Most of the biodegradable, bio-based pots out there are geared toward short production cycles in the greenhouse (three to six months), after which they may become brittle, or fall apart when handled. Typically they are made out of rice hulls, corn or coir.

Higher costs

Although bio-based pots function very well, they often cost significantly more than plastic pots. With continuously rising input costs in nursery and greenhouse production, profit margins have been reduced. During these tough economic times, the nursery industry is looking to reduce costs.
Some Canadian researchers are examining bio-based pots that can be manufactured here in Ontario.
Locally grown, locally processed and locally manufactured products can reduce the carbon footprint of the product. The energy required for manufacturing biobased pots is usually lower, along with emissions, compared to petroleum-based plastic pots. When blended with recycled plastic materials, bio-based materials reduce the need for the virgin polymer in the manufacturing process. However, plastic pot manufacturers are already using some recycled plastic in their products.
A University of Guelph research project led by Dr. Amar Mohanty, Bioproducts Discovery and Development Centre, BDCC, and funded by OMAFRA, has recently been commercialized. Through Ontario businesses, biocomposite “bio-bins” are being retailed by Home Hardware and Canadian Tire stores across Canada.
In this biocomposite product, switchgrass was blended with oat hulls and used plastic. The composite was a process developed at BDDC, University of Guelph and then molded to produce the bio-bin products.
Manufactured by companies in the Cambridge and Kitchener region, there is a license agreement between the University of Guelph, Evolution Biopolymers/Green Ripple Innovations, Waterloo. It has been estimated that the bio-bins will reduce greenhouse gas emissions by 25 per cent.
Since local switchgrass, oat hulls and recycled plastic (agricultural bale wrap, plastic mulch, greenhouse plastic film) were used, the cost of the final product was actually 10 per cent lower than a comparable plastic pot. The BDDC’s goal is to manufacture 100 per cent bio-based products at a competitive price.
Dr. Mohanty also has an additional research project looking at biocomposites from proteinous co-products and natural fibres containers. Corn gluten meal and soy meal are plasticized with low grade glycerol (a byproduct from biodiesel) into bioplastic.
The bioplastic will be reinforced with Ontario-grown switchgrass and miscanthus.
At this time, there are only a handful of companies manufacturing biodegradable polymers in the global marketplace. These are made from corn, potato and other plant starches. Because of the high cost, it has been difficult to justify their use in place of traditional plastic products. Composites made from biodegradable polymers that are byproducts of corn gluten meal, dry distillers’ grains, glycerol, and plant fibres from perennial grasses, agriculture residues, can help reduce the cost and environmental footprint of these products. Another goal of Dr. Mohanty is to develop bio-based materials and other biocomposites that can be blended with waste plastic films from greenhouse production.
There is no question that developing bio-based materials for pots in nursery and greenhouse plant production is extremely challenging. In particular, it is challenging to meet the needs for a long term, woody nursery crop. The much longer cropping cycle, irrigation method, long-term outdoor exposure and handling practices (pot spacing, inventory shifting) can have significant implications on the feasibility of using biobased materials for nursery pots.
Research indicates that crop fibres, recycled plastics and agricultural byproducts can all be sourced from Ontario and manufactured into various biocomposite products. These ventures may open new markets for manufacturers, suppliers and growers, while reducing the volume of plastic waste in Ontario.
Jennifer Llewellyn may be reached at 519- 824-4120, ext. 52671, or by email