Recycling Waste Products from Molasses Fermentation

CSR Distilleries

CSR’s Sarina ethanol distillery has changed from an environmental pariah in the local community into a welcome industry. Through a world-first plant design, it has reduced steam and water consumption, improved plant productivity and product quality, and turned a pollutant into a saleable, import-replacing product. Instead of closing down in the face of community opposition to its environmental performance, the distillery has improved its business position. The community’s complaints have also ended.


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At its Sarina distillery, near Mackay in North Queensland, CSR Distilleries ferments molasses to produce ethanol for Australian and export markets. One of the waste products of this process is a liquid known as dunder.

The process

The distillery, which CSR purchased in 1972, discharged dunder directly into the tidal creek systems adjacent to Llewellyn Bay, within the Great Barrier Reef. As the local population grew and community expectations of environmental performance increased, CSR implemented a trade waste system, based on spray irrigation onto ploughed evaporation plots. This system operated satisfactorily during dry weather, but problems were experienced during the tropical wet season.

For example, biological oxygen demand levels in run-off from the plots were high, resulting in low oxygen levels in the local creek system. Discolouration of water sources was also a problem, and the onset of warm humid weather occasionally caused maggot infestation within the plots, leading to high levels of house flies on and around the plots. These, plus odour problems, put CSR ‘on the nose’ with the local community.

Although the local community valued the distillery as a major employer, CSR and its employees wanted to improve the community attitude towards the distillery's operation and to improve the condition of the spray irrigation site.

Several options to improve the method of dunder disposal were considered, including:

In examining these options and the economics of the plant, CSR concluded that any dunder disposal operation had to generate savings or revenue sufficient to justify the building of a new plant. Otherwise, it would have to close.

The new plant option was considered in detail, with particular attention to the possibility of reducing water consumption and hence concentrating the dunder into an economic by-product. The solids component of dunder has always been recognised as a significant source of potassium, with potential for use as a soil fertiliser. However, the high water content of dunder resulted in a low concentration of potassium, and consequently widespread use of dunder as a fertiliser source was limited due to transport economics. Consideration of the new plant option focused on producing fertiliser as a viable by-product.

Cleaner production initiatives

During the 1980's, CSR built and operated a small-scale (one-tenth capacity) treatment plant to test a new continuous fermentation technology called Biostil. Laboratory trials indicated that the process would increase ethanol yield, but more importantly, it would effectively double the dunder concentration and reduce steam consumption.

To further improve the process, particularly for the handling of trade waste, the pilot plant was used as a model to determine how to increase the dunder concentration further. By modifying the pilot plant's operation to a semi-continuous mode, the plant successfully produced dunder at four times the original concentration.

After further research, CSR constructed a new distillery at Sarina, using a two-tank, semi-continuous Biostil fermentation system, coupled with the latest technology in heat reuse distillation system.

Advantages of the process

The plant was a world-first for Sarina and achieved:

The new plant commenced trial operations in May 1989, and moved into fully operational mode almost immediately. The distillery is fully automated, and is operated by one person using computer-controlled equipment.

Biodunder has been accepted by cane and other farmers as a valuable potassium-rich fertiliser and 100% of the Biodunder product at the Sarina distillery is now recycled into this market (see Graph below). Previously, only imported fertiliser was used by the cane farmers in the area. CSR, through its Sarina distillery, is now working with the sugar industry to improve and add further value to the Biodunder by adding nitrogen and trace elements.

Percentage of dunder used locally

Cleaner production incentives

CSR now generates revenue from a value-added product, which was previously a pollutant. Public complaints about the distillery have ended. The environmental benefits of the initiative were acknowledged in 1992, when the Australian Chemical Industry Council awarded its annual Environment Award to CSR employees who had been instrumental in developing the Biodunder concept.

The dunder spray irrigation system which had been in use since CSR purchased the distillery, and which was expected to be phased out over four years, was shut down less than two years after the Biostil plant was installed. The old spray irrigation areas have been fully rehabilitated and wash-off from the old evaporation plot areas during rain periods now contains no residual dunder spray material.

The public image was important to CSR. The company commented that:

CSR is a company with a 140 year old tradition...committed to continuous improvement in every facet of our operations...current concerns about environmental issues have been successfully addressed. - CSR


The Sarina distillery was a world-first in the way it addressed the dunder disposal problem through the use of the semi-continuous fermentation technology. This meant that there was risk and uncertainty during the development phase, but it has helped solve the trade waste disposal problem associated with all molasses distilleries.

Because Biodunder was a new product, at the same time as the new Biostil plant was being designed and built, a Biodunder Marketing Officer was employed to test its marketability. The Bureau of Sugar Experimental Stations assisted by conducting canefield trials and determining optimal dunder application rates at its test station in Mackay. The Biodunder Marketing Officer at Sarina is continuing to develop the market by maintaining and improving relations with local organisations, including cane grower groups and transport companies.

Local community groups have been encouraged to visit the new factory and inspect the regeneration of the land area previously used for dunder disposal and the new dunder/fertiliser storage and loading installation. This has helped spread awareness of the Distillery’s excellent new environmental performance.

The Cleaner Production Case Studies Directory is part of EnviroNET Australia.
For more information contact:
Environment Australia
Environment Protection Group
PO Box E305