Recycling perlite: New, improved method saves resources

March 17, 2011

BOSSIER CITY, LA--Perlite, a processed volcanic mineral, is widely used as a component of soilless growing mixes. Lightweight, sterile, and easy to use, perlite is popular with greenhouse growers. But because salt and pathogen buildup can occur when perlite is reused, it must be replaced every year or two to minimize the risk of crop failure. The cost of disposing of old material and replacing it with new perlite can be significant and often prohibitive for smaller greenhouse operations. Hanna Y. Hanna, a researcher at Louisiana State University Agricultural Center's Red River Research Station, has developed a new method for recycling perlite that can save tomato growers a significant amount of money without reducing crop yield.

Hanna, who has done extensive previous research on perlite, says that using the same perlite to grow successive crops like tomatoes can be risky; it tends to compact and is subject to salt build-up and pest contamination. "Steam sterilization of used perlite before planting a new crop is recommended to safeguard against pathogen contamination, but this treatment requires the use of expensive steam generators and is not efficient in desalinating the medium", Hanna said.

In a recent issue of HortTechnology, Hanna reported on a new method developed to accelerate the recycling of perlite. The experiments were conducted in a greenhouse over three growing seasons to evaluate three different methods for perlite recycling and their effects on cost, desalination efficiency, and tomato yield.

Three recycling methods--"no stir/sift-then-disinfect", "stir-then-disinfect", and "sift-then-disinfect"--were put to the test for Hanna's experiments. Each recycling method consisted of two components: the reconditioning action and the hot water treatment. During the experiments, perlite recycled with the no stir/sift-then-disinfect method was not reconditioned before the hot water treatment. Instead, it was agitated with a nozzle mounted on a pressure washer wand during the hot water treatment. Perlite recycled with the stir-then-disinfect method was reconditioned first with an auger mounted on an electric drill, then treated with hot water. Perlite recycled with the sift-then-disinfect method was reconditioned first by sifting the perlite with a homemade apparatus, then treated with hot water.

"The results revealed that recycling perlite with the no stir/sift-then-disinfect method reduced labor input by 49% and 81% compared with the stir-then-disinfect and the sift-then-disinfect methods, respectively. The no stir/sift-then-disinfect method reduced recycling cost by 22% and 50% compared with the other two methods, respectively", Hanna noted. Tomatoes grown in perlite recycled with any of the three methods produced similar marketable and cull yields and fruit weight.

The results showed that the no stir/sift-then-disinfect method is less time-consuming, more economical, and has no negative impact on yield. The new method gives greenhouse tomato growers more cost-effective options for recycling perlite while saving valuable natural resources.

"The cost of renting of a hot water pressure washer and a few miscellaneous items can be the only out-of-pocket expense for using this method. Additionally, the method eliminates labor time and effort to remove old medium from the greenhouse, transport it to a land fill or a vacant field for disposal, and fill other bags with new perlite", Hanna concluded.
-end-
The complete study and abstract are available on the ASHS HortTechnology electronic journal web site: http://horttech.ashspublications.org/cgi/content/abstract/20/4/746

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org

American Society for Horticultural Science

Related Recycling Articles from Brightsurf:

Paper recycling must be powered by renewables to save climate
The study, published in Nature Sustainability, found that greenhouse gas emissions would increase by 2050 if we recycled more paper, as current methods rely on fossil fuels and electricity from the grid.

Lighting the path to recycling carbon dioxide
Combining solar-harvesting materials with carbon-dioxide-consuming microbes could be an efficient way to generate clean fuels.

Plastics, waste and recycling: It's not just a packaging problem
Discussions of the growing plastic waste problem often focus on reducing the volume of single-use plastic packaging items such as bags, bottles, tubs and films.

NREL research points to strategies for recycling of solar panels
Researchers at the National Renewable Energy Laboratory (NREL) have conducted the first global assessment into the most promising approaches to end-of-life management for solar photovoltaic (PV) modules.

Recycling plastics together, simple and fast
Scientists successfully blended different types of plastics to be recycled together, providing a solution to the environmental problem of plastic waste and adding economic value to plastic materials.

Chemical recycling makes useful product from waste bioplastic
A faster, more efficient way of recycling plant-based 'bioplastics' has been developed by a team of scientists at the universities of Birmingham and Bath.

New recycling method could make polyurethane sustainable
Polyurethanes (PUs) are used in many products, such as mattresses, insulation, footwear and construction materials.

Almond orchard recycling a climate-smart strategy
Recycling orchard trees onsite can sequester carbon, save water and increase crop yields, making it a climate-smart practice for California's irrigated almond orchards, finds a study from the University of California, Davis.

'Deceptively simple' process could boost plastics recycling
Plastics are a victim of their own success, so inexpensive, easy to use and versatile that the world is awash in plastic waste.

New membranes for cellular recycling
Cells produce the shell of the autophagosomes on the spot.

Read More: Recycling News and Recycling Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.