By James Wall.
After a recent trip to the Melbourne Zoo, I was fortunate enough to see the “Hotrot” composting system that has has been installed there. It is an enclosed system that emits very little smell. It composts in about ten days. First the waste material is shredded, and then put into this enclosed composting tunnel that has a massive auger like shaft with tines attached pushes the compost from one end to the other. The shaft moves about five minutes every hour.
Hot air is added, and excess waters, odour and heat are released as vapour, and discharged through an exhaust, into a bio-filter. This means no leachates or run-off are produced, ensuring higher nurient value of the end product. After the process is complete, yes, out comes some lovely garden compost and any potential weed seeds eradicated.
This process has really helped the zoo process its waste and lessen the smell which can cause local issues in other open composting processes. The staff at the zoo also seemed to be proud to be part of the process. The manures composted are only from herbivores (non-meat eaters) and unfortunately doesn’t include elephant poo as it contains a high sand content, due to the way an elephant eats. This coarse sand would cause damage to the components of the composter so it is composted in the traditional way and fortunately doesn’t smell too bad. Straw, herbivore’s poo, food scraps and prunings from the zoo are included. Up to 2.4 tonnes a day.
At this point, the compost is sent to our potting mix and compost supplier Grow Better. They then bag it under the name Zoo Gro and sell it to local nurseries like ourselves. It is completely organic and is an ideal, nutritious compost for all garden beds. Best of all, a royalty from every bag sold goes back to the Melbourne Zoo.
We also sell a wonderful compost from Grow Better called Black Gold. It has been loved by our customers for many years. After seeing the process at the
Melbourne Zoo and talking to some of our fellow local nurseries around Melbourne, we are proud to also be able to offer Zoo Gro. On sale now in 30 litre bags.