|Environmental Management Improves Product Quality in Wool Scouring||Australia||-||Full scale|
MANUFACTURE OF TEXTILES # 3
In 1980, European companies began to move wool scouring capacity to Australia due to environmental problems and land constraints in Europe. A French company, CIL (Compagnie D'Importation De Laines) purchased the Goulburn Wool Scour (GWS), Australia in 1988. However, it was soon found that they faced with numerous environmental problems at the plant. GWS responded by turning these problems into business solutions. It sought cleaner production through improved efficiencies. It undertook a program of research and development using technology adapted from the mining, food and steel making industries. It set a target payback period of two years for every measure to be adopted, reflecting the recession in the industry.
At peak production, the GWS plant processes around 50 tons of wool per day on two lines covering all grades of wool. The company operates on a basis of three shifts per day, five days per week.
Cleaner Production Principle:
Recovery, reuse and recycling; Process modification; Housekeeping
Cleaner Production Application:
Wool scouring is a polluting as well as energy-intensive process. It involves de-dusting, then washing in a series of hot detergent bowls, followed by rinsing to remove lanolin, dirt and sweat (suint) from greasy wool. The dirtiest liquor streams are treated to remove as much dirt and wool grease as possible. In unmodified plants, a single scouring line produces a pollution load equivalent to the pollution produced by 30,000 people. On an average, each ton of greasy wool contains 150 kg of lanolin, 40 kg of suint, 150 kg of dirt (organic and inorganic), and 20 kg of vegetable matter and 640 kg of wool fiber.
GWS adopted a management philosophy based on the three R's - reduce, reuse and recycle. An R&D program that looked at adoptable technologies from the mining, food and steelmaking industries has produced several modifications to its plant.
GWSs initiatives include:
|Minimizing water consumption, with recycling of up to 50% of wastewater;|
|Recovery and use, or sale, of waste by-products; and|
|Saving energy to cut up to 25% off power bills.|
1. Minimizing water consumption
The GWS team cleans the dry wool using a highly adapted de-duster, which incorporates several changes from the original design. This reduces the load and effluent disposal problem further in the process. Depending on the extent of contamination of the wool with vegetable matter, normally vegetable matter ranging between 3-15% is removed from the wool. A full self-cleaning function is being supplemented with a vacuum process to take away the dirt and further reduce labor time, increasing the overall efficiency of the process.
Each of the two scour lines uses 12,000 liters of water per hour, 10,000 of which is recycled from the rinse process. Used rinse water has a BOD of about 150. GWS uses a 4- megaliter-dam to grow algae as part of the cleaning process for recycling rinse water. The algae metabolize nutrients out of the water. From here, the water is pumped to a trickle tower and clarifier. Next, a saw tooth weir assists removal of flocculated algae and gravity settling of other contaminants. Recycled rinse makes up to 50% of the rinse water requirement and costs only half the price of the drinking water piped in from Goulburn.
2. Recovery and use, or sale, of waste by-products
The effluent and dirt removed by pre-treatment is ploughed into the paddocks. It could be mined in later years for organic fertilizer, with up to 10% potassium content. GWS runs all water from the scour process (except for process water that is reused to wash down the plant and water the gardens) through a Humbolt Decanter and centrifuge to remove solids. The sludge by-product of the centrifuge (approximately 2,000 tons a year) is also ploughed into GWS's paddocks returning organic matter to the soil. The sludge is spread at the plant site in a closed area where the many weeds that are brought in with the fleeces can be controlled.
Valuable wool grease is recovered from the wastewater. About 1,000 tons per year is sold to cosmetics companies in the USA, Asia and Europe. A benefit of GWS's high recovery of wool grease is that oil-soluble pesticides that have been placed on the sheep's back by farmers are also trapped. This means that GWS does not have pesticide residue problems in the remaining scour water that could limit its use for irrigation. The purchasing companies remove the pesticides later from the grease.
The remaining scour water, with a BOD of 22,000, goes through a 120-day holding pond, and then a 60-day holding pond for anaerobic biological treatment. The extraction of solids is so effective that the 11 meter-deep ponds have only filled with 1.2 meters of sludge over the past 15 years. From the ponds, the water is pumped to storage dams and spray-irrigated onto pastured fields.
The plant produces 250,000 - 300,000 liters of effluent per day. This is used to irrigate two farms owned by GWS - 40 hectares next to the plant and another 40 hectares in a rural location reached by a 5.3 km pipeline, giving 150,000 cubic meters of storage. The effluent output is equivalent to approximately 250-mm rainfall per year over the total 80 hectares, and is sprayed out by mobile irrigators.
The irrigation has enhanced the soil structure and provided a lush crop of grass, which is regularly mulched to build up organic matter in the profile. Ten thousand black wattles have also been planted to improve the soil. Gypsum is added every 6-7 years to help break up any crust in the soil structure.
Recycling and effluent disposal is helped by the fact that GWS is one of only a few scours in the country running a full-alcohol, straight chain detergent. Although the detergent is less effective than the non-ionic detergents generally used by other scours, it is sufficient for GWS; needs because of the efficiency of its pre-treatment dry cleaning process.
Detergent residuals in the soil have dropped by 90%. Sludge spread on GWS land becomes biologically active in a relatively short time as the alcohol detergent breaks down in 3 to 4 weeks. The previous detergent used to take as long as 7 to 8 months to break down. GWS has demonstrated that now, even earthworms can grow prolifically in the sludge.
3. Energy saving
GWS adds most heat at the end of the drying line rather than at the beginning. This is not a conventional practice in the industry. The company uses innovative drying processes at the point of heat injection with the help of tightly zoned monitoring controls. Refinements on this approach have led to a saving of 56% in energy costs in the dryer, which translates into a saving of $68,000 and reduces the annual bill to $300,000 for the whole plant.
GWS has also made savings through simple measures such as increasing the number of light panels in the roof. Where lights are installed, they are isolated for individual switching and driven by photocells to minimize wasted electricity. A power balancing system is also used to optimize load throughout the plant. To save further energy in plant ventilation, seven electrically driven exhaust fans have been replaced by convection venting.
On the scouring line, a highly controlled and monitored processing system has enabled the management and operators to apply just the right amount of energy appropriate to each of the stages. For instance, scouring requires a temperature of 62 degrees Celsius, while rinsing only requires 52 degrees Celsius. Not only does controlling the temperature save energy, but the warm effluent from the process is tapped by heat exchangers to recycle much of the heat back into the processing line, as well as for wash-down water. Any heat that escapes is used for other purposes. For instance, an energy counterflow system in the boiler is used to preheat incoming fresh water to minimize the energy required to get it to processing temperature. Optimizing temperatures used in stages of the scouring process and improvements in boiler efficiency has reduced gas usage by 25%.
Clean-down water is kept at 55 degrees Celsius so that wool grease is removed while keeping the workers safe from the risk of being scalded. Most of the other plants in the industry run at 60-65 degrees Celsius. GWS can save energy using the lower temperature because of their pre-treatment and processing efficiency.
GWS also has two air compressors that have small PLCs monitoring all functions. The larger compressor is programmed to carry the base load, and the smaller compressor is programmed to start and stop on the peak loads, thereby eliminating unnecessary compressor running time.
4. Efficiency and waste minimization strategy
The company is constantly looking for ways to improve efficiency and to cut waste. It employs a programmer to design process control and monitoring software programs specific to the plant. The close monitoring system enables continuous engineering and managerial fine-tuning. GWS has the complete history of the process settings of every batch of wool treated since 1992, enabling it to refine processes against its own and industry benchmarks. GWS gained support from CIL for innovations because it has demonstrated, through performance monitoring, that cleaner production pays.
The use of 100% computer control and monitoring has enabled the company to refine processes to day-to-day accountability for each batch. In one case, GWS questioned the manufacturers of the new drier installed on the second production line. GWS established, through close monitoring, that the new drier was less energy efficient than the company's earlier model on the first line. The finding has prompted some modifications.
Key GWS staff meet each morning to analyze the previous day's results on a wide range of economic, engineering and environmental performance indicators. This ensures that quality of product, efficiency of operation and optimum environmental management are at the forefront of planning and decision-making. Management aims to get the plant to 100% efficiency and maintain it there.
The highly computerized process controls have had the added benefit of enabling GWS to tailor processes to client requirements, rather than offering a generic product. This has given the company a marketing edge.
5. Training and informing dissemination
The labor force ranges from 35-46, depending on workflow. Most operators come from a non-industry skilled background and are trained intensively over 12 months, with another operator shadowing them on every task. GWS management believe that the key to encouraging line staff to come up with new ideas is keeping them fully informed of what management wants, and aware of the reduce, reuse, recycle philosophy. The intensive plant monitoring system then provides data for staff to base ideas and test them.
6. Environmental risk management
GWS has large irrigation storage dams and reserve areas available in case there is a particularly wet year. All the effluent from 12 months' production can be stored in the dams without the need to irrigate. This precaution exceeds the one-in-100 year's rainfall levels.
7. Minimizing storage, handling and transport costs
Wool delivered to the plant is tri-packed (i.e., three bales reduced to the size of one) to ensure efficient storage in the wool stores. For processing, these bales need to be expanded or reconditioned back to their loose wool state. Most plants have steam boilers, which inject steam into the bales. This process softens the lanolin and allows the bales to expand back to their original size.
Since GWS has no steam on-site, it has devised a system of packing the bales into insulated shipping containers and ducting the wool dryer exhaust into the containers. This exhaust vapor is at 100% relative humidity and approximately 65 degrees Celsius. It takes 24 hours to expand the bales back to full size.
The energy used in this process is free, as it is the waste exhaust from the dryer. The steam injection equipment used by other wool scours costs in excess of $100,000, plus the energy used to run them. GWS uses recycled shipping containers to achieve the same results.
GWS uses a high-density bale press for packaging the scoured wool. The press has a gentle action on the wool fiber and gives lower kilograms per cubic inch meter-density than the traditional tri-pack bale. This results in better processing performance and yield for the clients' products.
Each bale is more compact and therefore, more wool per unit of space can be loaded onto each truck. The dump wool press not only enables full truck weight loading; it also saves the wool having to be taken back to the wool stores to be compressed for export.
Environmental and Economic Benefits:
In an astonishing business turnaround, GWS went from being a battler on the environmental and business fronts, to a world leader in product quality and environmental performance - in just six years. At the same time, it was able to reduce costs significantly by reducing waste and gaining finer control of its processing.
It was this performance that led to Goulburn Wool Scour being selected to scour the most expensive bale of wool ever produced. With a bale price of $1.2 million, each ounce rivaled the price of gold, and became known as the Golden Fleece. GWS has also been awarded in the Industry Category of the National Energy Awards, run by Australia's Department of Primary Industries and Energy.
This case study was taken from The Cleaner Production Case Studies Directory EnviroNET Australia (see address above). It was edited for the ICPIC diskette in November 1998. It has not undergone a formal technical review by UNEP IE.
Subsequently, in March 1999 the case study underwent a technical review by Dr. Prasad Modak, Environmental Management Centre, Mumbai, India.