Wattyl manufactures solvent-based paints for the industrial and automotive refinish markets.
Until recently, the company did not think of waste minimisation as a priority and little attention was paid to the processes used for cleaning tanks and other equipment. More than 130,000 litres of dirty wash solvent was generated each year. Most of this waste was sent off-site for distillation/disposal in 200 litre drums, at significant cost.
Cleaner production initiatives
Participation in the Cleaner Technology Incentive Scheme sponsored by the Victorian EPA has resulted in the purchase of a small distillation unit capable of handling 800-900 litres/day of dirty solvent. Initial trials quickly pointed to the need to change the whole approach to equipment cleaning. A Process Group, comprising representatives from management, technical and factory staff, was set up. Over a period of 3-4 months, the Group introduced a series of formalised cleaning procedures:
- random choice of cleaning solvent was replaced by an evaluation process, leading to a choice of one single solvent for all tank and equipment cleaning;
- manufacturing procedures were modified to minimise or eliminate the use of wash solvent; and
- waste streams were separated and segregated, and a process of formal identification and recording introduced to provide traceability.
The distilled solvent was, in most cases, about 90% pure. Initially, it was intended to use the distilled solvent as wash solvent, but even 10% dilution significantly reduced cleaning efficiency. It was trialled as a partial replacement for purchased solvent in several blended thinner formulations which Wattyl found to be satisfactory in many of the products. By using the distilled solvent to replace new solvent, it was easily converted to a relatively cheap, gun-wash washing solvent that can be sold.
With about 90% yields achievable from the still, attention was then turned to the 10% sludge. A laboratory program was initiated to look at how the sludge could be used. A new paint product - a primer - was formulated around the distillation sludge. This primer has since been modified on several occasions to incorporate other waste or by-products from the paint factory.
Advantages of the process
Wattyl once had to dispose of 130,000 litres of dirty solvent wash and considerable quantities of waste paint each year.
It is now able to:
- distil 800-900 litres/day;
- recover up to 90% of wash solvent, which is re-used into finished product;
- recover the distillation sludge as a raw material in a specially formulated paint product; and
- recover about 60% of waste paint, which was previously disposed off-site, and use it to produce the same paint product.
The $100,000 capital investment in the distillation unit was re-couped in just over 12 months of operation. Contribution has continued at that rate and stockpiles of waste have been extensively reduced.
Cleaner production incentives
Reducing the cost of off-site disposal was the key motivation. The resulting new product uses and paint recovery have proven to be an unexpected windfall. The recycling of the solvent on-site also eliminates safety and environmental risks associated with the transport and off-site disposal of the used solvent.
The fact that the solvent had not been a company priority, and that there was little experience of using recycled solvent, meant that there was considerable uncertainty about the potential benefits of on-site distillation. The commitment of time and effort in the project, therefore, needed a re-thinking of this aspect of Wattyl’s business.