The Challenge
Carter Holt Harvey’s (CHH) Myrtleford sawmill processes plantation timber predominantly for the housing industry.
The sawmill uses waste sawdust and wood shavings produced on the site to fire boilers for the production of steam, which is used to heat timber drying kilns. A significant amount of ash is produced in the boilers. Because of the major fire and safety hazards associated with handling large quantities of hot ash, it must be “quenched” (cooled with large quantities of water) as it is removed from the boilers. The quenched ash is sold as a soil conditioner.
CHH was using 38 million litres/year of potable water for this process – or five per cent of Myrtleford’s drinking water. After being used once, this water was sent to trade waste.
The town’s main industry wanted to dramatically reduce its water consumption and trade waste discharge.
The Project
CHH used a Smart Water Fund grant to assist with the design and installation of an innovative boiler ash water-recycling project. This improved ash-handling process aimed to reduce the large amounts of potable water used to quench ash from the boilers.
Using a concept copied from the water treatment industry, a filtration process using a series of settling tanks, pumps and valves was designed to clean ash out of the water – allowing the water to be re-used in the system up to ten times. The remaining sediment, cold ash (carbon), could then be collected as a by-product for the production of soil conditioner.
The technology was adapted for the sawmill by a CHH engineer and constructed by local firm Nicoll Engineering.
The Outcome
Lessons Learnt
Following a six-month trial, results clearly showed the boiler ash water-recycling process would reduce potable water consumption of 38 million litres a year by almost 90 per cent – to just 4 million litres.
In addition to the huge water savings, the sawmill is now on track for a 90 per cent reduction in its trade waste discharge of 35 million litres annually.
“The fact that we can go from using five percent of our town’s water supply to about half a percent is a really rewarding result,” says Site Manager Laurie Medlock. “We have also significantly reduced the amount of ash carried over into trade waste, so there are some very real environmental gains here.”
The Benefits
Since its installation in October 2006, the reduction in potable water use has not only saved a significant amount of the town’s fresh water supply, but the improved collection and re-use of the ash by-product has also reduced silt build-up in local sewage ponds.
CHH will save about $60,000 a year in trade waste charges through the improved process. The system cost approximately $40,000 to create and install and, through reduced water and waste bills, has already paid for itself.
“We’re delighted that something with such obvious benefits to our community and local environment is not only paying for itself, but bringing bottom line benefits to our business, too.”
