Japanese Knotweed

One of the questions we often get asked at the Olus Sales Team, relates to sterilisation and purity of our end product of 10mm compost.  From a personal point of view, to be able to say to customers that we do not add anything at all to our compost is fantastic, in these times when people are looking for a chemical free and organic product.  Plastic and metal are taken out of the compost in the final screening process, by way of blowers to eliminate plastic and overband magnets to remove any metal, however, customers often query how much contamination any unwanted species may remain in our end product. 

 

 

In our composting process the temperature of the windrows is crucial to eliminate what is known in our industry as “obnoxious weeds”.  Temperatures for the approval of our PAS100 accreditation need to be 67 degrees for a period of 48 hours, this sanitises the compost and kills all the pathogens and weed seed.  One of the absolute no-nos for us to intake on site is Japanese Knotweed, however initial research (see Organics Recycling – Winter 2011), is looking into the possibility that Japanese Knotweed cannot survive temperatures of more than 45 degrees (over a 48 hour period).

 

Windrows on site, will be at temperatures of 75 degrees for potentially 5 weeks , therefore with the potential to eliminate such an invasive species, that we are not allowed to take in, the composting process will eliminate far less invasive species and give a far cleaner end product than previously thought.

 

The alternative for Japenese Knotweed is the expensive and government recommended disposal by means of being buried to a depth of greater than 5 metres, or being incinerated.  Both these processes are far more costly than the composting process and have far reaching environmental consequences.  

 

We are looking forward to hearing how further research which now needs to be undertaken to establish the process for Japanese Knotwood, but on a far larger scale to prove the purification in the process.