Environment industries archive
Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.
Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.
This case study is no longer current with respect to the Company's business activities and operations and was not updated in the review of 2001, but is retained for informational, educational and historical purposes.
ConAgra Wool Pty Ltd has investigated a number of cleaner production initiatives for their wool scouring operation. The increased recovery of wool grease and optimisation of sulphuric acid usage in the carbonising process has provided significant economic returns to the company.
ConAgra Wool Pty Ltd is a wool scouring operation that supplies scoured and carbonised wool to the global market. The company participated in the Victorian Government's Cleaner Production Demonstration Project in 1992.
The scouring process involves washing the wool in a number of different "bowls" in open tanks which contain various cleaning solutions - that together comprise a scouring line. ConAgra has four scouring lines at its Laverton plant. After passing through the scouring line, the clean wool still contains some organic matter such as seed burrs. These are removed by carbonising, a process involving washing the wool with sulphuric acid, which dehydrates the organic matter, then rinsing and drying in an oven. The application of heat to the dehydrated organic matter turns it into carbon, which can then be easily removed as a dust material.
Wool scouring process diagram
The scouring process generates significant quantities of waste, including:
There are two main effluent streams at the plant:
In the excisting process the overflows from the washing bowls are sent to 'heavy solids' tanks, where the solids are settled out and the wash solution is returned to the wash bowls. The heavy solids tanks are located at some distance from the scouring lines, and as the wash solutions operate at an elevated temperature of 65 degrees Celsius, heat losses are experienced. In addition, the heavy solids tanks are nearing capacity as production volumes increase.
Current water usage is in the range of 20-25 litres per kilogram of wool processed. The long term objective for ConAgra is to halve this value.
ConAgra participated in the Victorian Cleaner Production Demonstration Program in 1992. The outcome from this program was the identification of a number of potential cleaner production processes that required further research and development (R&D) work to establish their viability. Participation in the program has led to an ongoing interest in cleaner production. Initiatives have included:
The wool scour line
The increased recovery of wool grease has had both environmental and economic benefits. The increased grease recovery has reduced the amount of Biochemical Oxygen Demand and Suspended Solids in the final effluent discharge, with a corresponding decrease in trade waste charges. Another benefit from improved grease recovery has been an improvement in washed wool quality. This has enabled ConAgra to maintain its market share in the face of considerable competition.
$16,000 per line
$27,500 per line
The single most important incentive for ConAgra to implement cleaner production initiatives has been the potential cost reductions that can be achieved. ConAgra already pays a significant amount of money for waste disposal and discharge of effluent to the sewerage system, and there is always attention being given to opportunities to reduce these costs.
Technical problems have been experienced with the hydrocyclones. Excessive rates of internal wear from the high solids loading has led to a search for more resistant construction materials. The initial hydrocyclones were made of a ceramic material, which has now been changed to a polyurethane material. Problems have also been experienced with solids buildup in the pumps, resulting in a decrease in pumping efficiency.
The initial R&D work indicated that the hydrocyclones worked effectively on the wash stages, and this was where the initial work was targeted. When ConAgra expanded the fitting of hydrocyclones to the rinse streams they found that they were not as effective as had been expected. This resulted in a level of disenchantment with the technology.
Accessing capital is also a barrier for ConAgra. This means that capital expenditures, even where the pay back is very attractive, need to placed into forward budget planning.