Sonoco promotes paper over plastics for biodegradable plant pots

Despite the many advances made in the past few years by bioplastics, it will not surprise plastics processors that paper remains a powerful competitor in many applications in which biodegradability is advantageous. A recent example of this stems from Hartsville, SC where packaging processor Sunoco is promoting its ReadyGrow paper plant pots as a sustainable alternative to plastic plant pots. However, the paper pots' durability is derived in large part from their oxo-biodegradable plastic lining.   

Sonoco is a multi-billion dollar/year packaging processor of consumer and industrial, heavy in the paperboard industry but also with a globally active plastics packaging network. The processor announced last week that Metrolina Greenhouses has specified Sonoco's biodegradable ReadyGrow planters for Metrolina' spring herbs. The one-quart planters entered the market last month. The paper pots don't impact Sunoco's plastics operations, as it does not process these.

The ReadyGrow plant pots are made from recycled paperboard produced in Sonoco's paper mills. They biodegrade in soil within 180 days of planting. The pots are porous to allow oxygen to pass through the container to a plant's roots. Sonoco says it uses its own "RootGuard" proprietary coating to ensure the pot withstands greenhouse watering and maintains good water absorption while in the soil. Once planted, the coating breaks down, allowing the plant's roots to penetrate through the pot.

In answer to questions from PlasticsToday, Sonoco spokesperson Robin Montgomery confirmed this coating is made from low-density polyethylene that is compounded with an oxo-biodegradable additive, which eventually breaks the plastic down into an inert material. This coating enables the recycled paper pot to withstand greenhouse watering for twenty weeks and maintains good water absorption in the soil. This allows greenhouses to use less water than plastic pots during the growing cycle.

As Montgomery explained, the processor chose an oxo-biodegradable material primarily because the coating fragments in the presence of oxygen, breaking down the LPDE and becoming inert. This also means it won't negatively impact the recycling stream should the pot end up being recycled. Asked about the potential for plant starch-based bioplastics such as polylactic acid in these plant pot applications, Montgomery replied that pots made with hydro-biodegradable materials such as PLA are not as compatible in a standard recycling stream.