Chemical Usage in a Lamb Skin Tannery

Carlile Bros Pty. Ltd.

By implementing a number of cleaner production initiatives relating to more efficient usage of tanning chemicals, Carlile Bros Pty. Ltd. has been able to continue operation of the Bowron lambskin tannery in the face of lower trade waste limits and increased trade waste costs. A key component of Carlile Bros.' cleaner production program was a detailed understanding of all its waste streams.

Contact

Mr Graeme Carlile

Carlile Bros. Pty. Ltd.

PO Box 150

Bendigo VIC 3550

Ph: 61 54 431033

Fax: 61 54 437961

Background

Carlile Bros. Pty. Ltd. is a joint venture partner in the Bowron lambskin crust tannery located at Bendigo, in regional Victoria. The tannery processes green and salted lamb skins to produce crust tanned skins, which are further processed in tanneries in New South Wales and New Zealand.

The Process

The green or salt preserved skins are processed in wooden vats where the skins are soaked, washed, fleshed, scoured and tanned with a synthetic tanning agents. Each vat has a capacity of 50 skins. After draining, the skins are then dried, ready for further processing.

Cleaner Production Initiative

The main cleaner production initiatives involved were:

• the installation of a centrifuge to spin dry skins between the washing and tanning stages;
• installation of a system to collect and recycle tanning liquors; and
• evaluation of specific chemicals used in the tanning process.

An essential prerequisite to identifying these cleaner production initiatives was the undertaking of a rigorous mass balance and analysis program over every process operation in the tannery. This was essential to obtaining valuable and precise data on the various sources of effluent, and allowed the identification of a number of cleaner production options.

Key findings from the mass balance analysis were:

• tanning liquors were not being fully recycled and up to 50 per cent of some tanning chemicals were being discharged to the effluent;

• there was excessive water use on the baffling and fleshing machines, which could be reduced by installation of automatic controls;

• a high concentration of boron in the final effluent could be reduced by the selection of alternative chemicals; and

• the effluent quality was sensitive to the concentration of tanning solution.

One of the main reasons for the relatively low rate of tanning liquor recycling was that additional water was entering tanning solutions. As a result, excess tanning solution had to be dumped from the tanning baths at the end of each cycle. The minimisation of this water input was given a high priority.

One of the more significant inputs of water into the tanning solutions was water carryover from the skin washing process. In the existing process the skins were left to drip dry between the washing and tanning stages. This proved to be an ineffective method of removing excess water from the skins and in fact was adding approximately 5 litres of water per skin to the tanning solution. The installation of a centrifuge to spin dry the skins after washing has reduced the carryover volume by 30 per cent.

After tanning, the skins are left to air dry in a specified area. All excess tanning solution that drains from the skins is collected and returned to the tanning baths.

Advantages of the Process

The main advantage of these cleaner production initiatives was that it has allowed the tannery to continue operating in the face of more stringent discharge standards being imposed by the regional water authority. The reductions in contaminant loading of the effluent are detailed in the following table.

PARAMETER	PERCENTAGE REDUCTION
Total kjeldhal nitrogen	40%
Phosphorous	70%
Boron	60%
Chemical oxygen demand	no change
Suspended solids	no change
Salinity	no change

The costs and savings from implementation of the program are as follows:

ECONOMIC BENEFITS
Costs
Capital expenditure	$250,000
Increased labour	$30,000 pa
Waste stream monitoring program	$30,000
Annual Savings
Reduction in raw water	$2,500
Reduction in chemical usage	$63,000
Reduction in trade waste charges	$14,000
Total Annual Saving	$79,500
Payback Period	5.7 years

The proactive approach taken to cleaner production has resulted in the water usage falling from 700-800 litres per skin to 400 litres per skin. Even though the volume of effluent has been reduced and quality improved, the trade waste costs have increased from $30,000 pa in the late 1980s to $250,000 pa in 1995, due to across the board increases by the water authority.

There is also a strong feeling that the cleaner production initiatives have resulted in an improvement in product quality, as a result of better tanning efficiency, which has resulted in increased competitiveness in the world market.

Cleaner Production Incentive

The key management initiator was an increase in trade waste charges being proposed by the regional water board to cover the cost of construction and operation of a new tertiary treatment plant. At the same time, the regional water board also reviewed and tightened the limits for trade waste discharges.

Significantly, while these projects have been successful for Carlile Bros, they have served merely as a springboard for further cleaner production work. The company has subsequently established its own Research and Development Department to conduct research into a number of potential cleaner production initiatives.

Barriers

The cleaner production initiatives that have been implemented at the tannery are considered by the tannery management to be simple. However the largest barrier to implementing cleaner production was a lack of knowledge of internal effluent stream volumes and quality. For this reason an extensive monitoring and analysis program, which ran for nearly three years, had to be undertaken. The information gained from this exercise disproved prevailing beliefs on where the wastes were coming from and was an essential precursor to implementing any of the cleaner production initiatives.

Case study prepared: January 1997 by ACCP

The Cleaner Production Case Studies Directory is part of EnviroNET Australia.

For more information contact:

Environment Australia
Environment Protection Group
PO Box E305
KINGSTON ACT 2604
AUSTRALIA
Email: cproduction@ea.gov.au
URL: http://www.environment.gov.au/net/environet.html