Scotland MBT Plant
The Dunoon Mechanical Biological Treatment (MBT) plant is one of three built in Scotland for Argyll and Bute. The plants were designed by CRS and are operated by Shanks Waste Services Ltd. Each plant is designed to accepted 13,000 t/a of mixed household waste, collected in plastic bin bags.
Waste is delivered into the reception area from which it is loaded, via a conveyer it the Hydrum. Here the bags are opened using high pressure water and the waste pulverised and mixed. The waste leaving the drum passes over a 50 mm screen. The oversized material passes over a magnetic head roller to remove the ferrous metals for recycling and the remaining oversize goes to landfill. The undersize organic fraction is removed to CRS Composting Bays by loading shovels. The composting bays have retractable roofs and, once filled with the waste are closed and assigned a batch number. The composting process has ABPR approval. Probes are inserted into the waste to monitor the temperature to ensure that the ABPR time/temperature parameter of 60°C for 2 days is achieved. The temperature data is transmitted via a data logger to a PC in the office. The CRS Batchtrack software records the temperature and alerts the operator when the first barrier parameter has been passed. Air is forced up through pipes in the floor to ensure that the composting process is fully aerated. The air circulation is managed by the Air Handling Unit and an Odour Control Unit neutralises all obnoxious smells by oxidation using ozone. The composting material is then transferred to the second barrier bays where again the time/temperature parameter of 60°C for 2 days must be passed.
The compost now needs to be matured and dried. It is moved to bio-drying bays where air is continued to be forced through the compost. Here it remains until it is dusty dry.
The compost is now ready for the unique CRS G2S process. The dried material is screened at 4 mm. Any oversize is then milled and the glass particles reduced to sand. The milled material is rescreened and the two sub 4 mm fractions combined to create a compost-like output (CLO). This soil-forming material is currently being used for restoring the old landfill.
Scotland MBT Plant Statistics
| Plant Design | CRS |
| Consulting engineer | Halcrow |
| Operating contractor | Shanks Waste Services Limited |
| Plant Owner | Shanks and Argyll Bute |
| Composting Vessels | Single door bays with retractable roofs |
| Pre-treatment process | Hydrum, Screen, Magnet |
| Post-treatment process | Double screen and mill |
| Maturation | Enclosed bio-drying |
| Process monitoring | CRS Batchtrack |
| Number of tunnels | 8 off |
| Tunnel waste capacity | approx 140 tonnes |
