Recycling of our Stonewool

At the recent Protected Cropping Australia Conference, Chisholm and Grodan held an informal meeting for growers to look at potential recycling options for growers who are using stonewool as a medium.

Whilst our European colleagues are well served in this area with Grodan recycling their product for producing bricks, the Australian market is hindered by the lack of critical mass of growers in localised areas. 

The meeting soon identified that whilst a Nationally based total solution would be great, the reality was that growers are seeing local solutions to recycle the product. And the recycling issue is not just limited to the stonewool, with growers looking for whole of enterprise solutions that will allow them to process crop trash as well.

On a more local level, we have been looking at how we might utilise our old stonewool slabs for a secondary use. Trainee Sara Nour and Diploma student Marcus Long have been looking at trials involving adding increased percentages of green matter to shredded stonewool with the aim of producing a composted green waste product with stone wool as an additive. These trials are in the early stages and we will be looking to publish their findings as time develops.

After we had removed the plastic, the initial issue was how to shred the slabs. We did investigate using a commercial tree chipper, but the trials with this style of machinery were varied to say the least! The action of the chipper was very aggressive and the dry slabs turned to dust - and blew away!, whilst slabs with a SMC of approx 30% or greater just clogged up the machine.

Our second attempt at shredding the product involved a more agricultural solution. Certificate 3 students Mark Lim, Robert Bounday, Graham Elsworth, Aaron Jackman and Di Lester have been involved in this process, and this saw them running a tractor mounted rotary hoe across the slabs with a PTO speed of 540 RPM. 

 

The rear shield was initially kept up to allow for a more open breaking process of the slabs and then lowered to mill the product.

The results were promising in that we were left with a fairly fine product that we now believe we can utilise as either a generic mulch for tress and shrub beds, or a potentially useful product that we can use in relation to 'vertical wall landscaping' as part of our Landscape students developing project.

 

So our 'local solution' seems to be working well in terms of processing, and we will keep you posted on the results of the 'secondary use' viability. 

For further information on any of the processes that we are experimenting with, feel free to contact us via e mail at tony.bundock@chisholm.edu.au