Azwood strive to create high-quality composts in a range of values, repurposing different residues and products from industries around New Zealand.
Although we use a lot of different methods to try and mitigate stone in compost, it is not possible to eliminate them completely.
Where does stone come from?
From forestry sites
One of our main ingredients for our compost products is pine or origin bark. This bark can contain a small amount of stone from the logging process or when the bark is collected from the storage areas before a log is processed. Stones are sometimes lodged into the bark crevasses or can be pick up from the ground on which it fell on.
From green waste
We offer a green waste drop off service where anyone can come and dump their green waste and we repurpose into compost. Often this can include roots and also dirt where stones can get caught up. We process this product and chop it down which reduced any large stones but there may be still fragments of it dispersed throughout.
From the ground
On our manufacturing site where we process bulk compost the surface is compacted gravel. Due to the size of the yard if we were to concrete the area, this would cost millions of dollars and in order to absorb those costs this would reflect in a very expensive compost product. There is risk in weather events and general processing that some stone can get collected from this surface and into the composted product.
To understand the scale of our composting process read – How Azwood makes quality, consistent compost in bulk
So what do we do to control it?
Unless stated otherwise, our composts are screened to 12-20mm depending on the grade/blend. This means that any particle dimension that can fit through a 12-20mm hole would slip through. This screening process will eliminate most stone outside of this size which reduces the stone content.
✓ We train our operators consistently to carry out quality control procedures and ensure we are operating with quality in mind.
✓ There are standards to comply with for contamination checking of incoming raw materials to ensure we a receiving consistent raw products.
✓ Azwood has some of the best and leading stone removal equipment in the bark processing operation but this still cant remove ALL of the smaller particles.
Is stone in compost bad?
Not necessarily.
If there is too much it could be, but small particles here and there shouldn’t really have any effect on the growing operation or purpose of the product if they are below the size of which our quality control processes are set up for.