Until 2006, all raw sugar produced in Queensland is acquired by and vested in Queensland Sugar Limited which markets the sugar to domestic and export customers.
The crushing season generally lasts about 22 weeks although some mills crush their available crop in less than 20 weeks and expansion will mean that in some areas, season lengths may increase.
Most of the sugar mills operate under continuous crushing arrangements, 24 hours a day, seven days a week, during the crushing season.
Continuous crushing proves a better utilisation of harvesting, transport and milling capital. Whether continuous crushing or not, the daily operations are on a three-shift, 24 hour crushing basis.
A typical Queensland sugar mill is equipped to crush cane at a rate of more than 500 tonnes per hour and crushes about 1.45 million tonnes of cane per season compared with about 195,000 tonnes per season in 1950.
Australia has some of the most efficient and technologically advanced sugar mills in the world. Some of Australia’s manufacturing companies export machinery and mill technology to other sugar producing countries.
Queensland Sugar Limited operates a quality management scheme on behalf of the industry to ensure that raw sugar produced by mills meets customers’ requirements.
The quality and efficiency of the raw sugar production process have been assisted through improved milling technology and government and non-government research.
Some sugar mills also produce raw sugar suitable for home consumption or manufacturers’ use, called “direct consumption” raw sugar. Their production process conforms with health regulations governing the production and handling of food for human consumption.
History
Australia’s first commercial sugar mill was established in 1864 at Ormiston, in Brisbane, by Captain Louis Hope.
The number of sugar mills throughout Queensland and northern New South Wales increased as the sugar cane growing industry began to expand.
In 1892, there were as many as 72 sugar and juice mills ion operation throughout Queensland. By 1920, this number had decreased to 34 due to server drought and the 1911 strike of mill workers.
ESTABLISHMENT OF AUSTRALIAN RAW SUGAR MILLS
|
Mill |
Built |
Commenced Crushing |
| QLD |
Mossman
Tableland
Mulgrave
Babinda
Mourilyan
South Johnstone
Tully
Victoria
Macknade
Invicta
Pioneer
Kalamia
Inkerman
Proserpine
Farleigh
Racecourse
Pleystowe
Marian
Plane Creek
Fairymead
Millaquin
Bingera
Isis
Maryborough
Moreton
Rocky Point |
1897
1997
1895
1915
1882
1915
1925
1883
1874
1919
1883
1880
1914
1897
1883
1887
1869
1894
1893
1884
1882
1884
1896
1895
1896
1879 |
1897
1998
1896
1915
1882
1916
1925
1883
1874
1921
1884
1884
1915
1897
1883
1887
1869
1895
1896
1884
1882
1885
1897
1896
1896
1879 |
| NSW |
Condong
Broadwater
Harwood |
1879
1880
1874 |
1880
1881
1874 |
| WA |
Ord |
1995 |
1995 |
Source: Mills
MILL OWNERSHIP
Mill ownership became more concentrated during the 1980s and 1990s. In 1980, 19 companies operated 33 sugar mills. In 1997, 12 companies operated Australia’s 29 sugar mills, not including the Tableland Mill which commenced crushing in 1998. In 2012, 9 Companies operated 24 sugar mills.
The state-wide rationalisation of Queensland’s sugar milling and transport operations in recent years resulted in the closure of the Qunaba, Goondi, North Eton, Cattle Creek and Hambledon sugar mills. The cane lands assigned to those mills were reassigned to adjoining mills.
OWNERSHIP OF AUSTRALIA’S SUGAR MILLS
PUBLIC COMPANIES
The Maryborough Sugar Factory Limited – Tableland, Mulgrave, South Johnstone, Maryborough. Owned by Mitr Pohl.
Tully Sugar Limited. Owned by COFCO, through its Australian subsidiary Top Glory (Australia) Pty Ltd.
Wilmar International Limited – Victoria, Macknade, Invicta, Pioneer, Kalamia, Inkerman, Poserpine, Plane-Creek.
Bundaberg Sugar Ltd – Bingera, Millaquin. Owned by Finasucre
PUBLIC UNLISTED COMPANIES – GROWER-OWNED MILLS
Mackay Sugar Limited – Farleigh, Racecourse, Pleystowe, Marian, Mossman.
Isis Central Sugar Mill Co Limited
CO-OPERATIVE/GROWER-OWNED MILLS
New South Wales Sugar Milling Co-operative Limited – Condong Broadwater Harwood
PRIVATE COMPANIES
W H Heck & Sons Pty Limited – Rocky Point
Other Entities
Sugar North Limited, a network organization comprising the independent grower-controlled mills in North Queensland, Mossman and Mulgrave, as well as the publicly owned Tully Mill, was formed in 1993 to ensure the long-term viability of sugar production in far North Queensland. This was disbanded in the early 2000’s. Sugar cane must be milled as soon as possible, but within 16 hours of harvesting, to minimise deterioration. For this reason it is important that the cane farms are in close proximity to the sugar mills they supply.
Transport
Mill owners have made a substantial capital investment in cane railway networks and rolling stock. To ensure the prompt delivery of cane to the mills. Australian mills own and operate a network of 4,190 kilometres of narrow-gauge cane railways. In the 1996 season, 95 percent of the record cane crop was transported to sugar mills using railways. Six mills in Australia use road transport systems exclusively and several use a combination of road and rail transport.
The installation of a computerised animated cane transport scheduling system has enabled cane movements between the farms and mills to be monitored. Using computer images, all cane bins can be located on the tracks to ensure they are moved quickly and efficiently. This process assists millers in operating an efficient cane transport system and reduces cane delays.
Milling Process
1. After harvesting, cane is transported to the mill where it is weighed and processed at automated cane-receiving stations. The name of the producing farm and the weight of each cane bin is automatically recorded.
2. The cane billets are tipped onto a cane carrier and transported to a shredder. The shredder reduces and shreds the cane into fibrous material and ruptures the juice cells.
3. Pairs of rollers feed the cane through a series of mills. Each mill consists of three large rollers arranged in a triangular formation. This process separates the sugar juice from the fibrous material, called bagasse. The sugar juice is pumped away for processing into raw sugar and the bagasse is recycled as a fuel for the mill boiler furnaces.
4. Juice extracted from the crushing mills contains impurities which are removed by adding lime and heating the limed juice. The lime neutralises acids and precipitates impurities which “settle out” in large specially designed vessels called clarifiers. The clear sugar juice is run off from the top of each clarifier.
Muddy juice extracted from the bottom of the clarifiers is mixed with fine bagasse and then filtered using cylindrical rotating vacuum filters to recover the sugar. The mud and bagasse mix (filter mud) extracted by the filters is used as a fertiliser on cane farms and in gardens. This recycles much of the phosphorous taken up from the soil by the cane plant.
5. The clear juice from the clarifiers is concentrated by boiling it under vacuum ina series of connected vessels called effets or evaporators. The concentrated juice is called syrup.
6. The syrup (about 65-70 percent sugar) is concentrated by boiling in a vacuum pan and is seeded with small sugar crystals in a process called crystallisation.
The sugar crystals are grown to the required size by adding more syrup while boiling continues. When the crystals reach the required size (approximately 1.0mm), the mixture of syrup and crystals called massecuite is discharged from the pan.
7. Syrup is separated from the raw sugar crystals in centrifugals which contain perforated baskets which spin at high speed in a casing (similar to a household washing machine). The dark syrup surrounding the crystals is “thrown off” and passes through the perforations. The spin-off syrup is boiled again and more raw sugar crystals are recovered. This procedure is repeated until the amount of sugar obtained is too small to make further extractions economical. Molasses is the syrup left over from the final centrifuging. This is stored for later sale.
8. The raw sugar from the centrifugals is dried by tumbling through a stream of air in a rotating drum.
9. The raw sugar is then transferred for short-term storage in bulk bins at the mills.
Research
Australia’s sugar mill owners finance a range of scientific research and development projects to improve raw sugar quality and processing. Research is conducted for and on behalf of all Australian sugar mill owners by the Sugar Research Institute (SRI), James Cook University, Central Queensland University, University of Queensland and the Bureau of Sugar Experiment Stations.
Key research areas include:
· Cane harvesting and transport· Cane preparation· Milling and diffusion· Raw sugar quality issues· Effluent treatment · Workplace, health and safety issues· Juice clarification, heating and evaporation· Sugar crystallisation, separation and drying · Steam generation and energy systems· Environmental aspects.
Environment and by products
A variety of by-products result from the milling of sugar cane. All mill by-products are recycled adding to the efficiency of the milling process and benefiting the environment.
Bagasse
Bagasse is the expended cane fibre which remains after the juice has been extracted. It provides nearly all of the fuel required for steam and electricity generation at the mills. In 1996 mills provided about 20 megawatts of power to the Queensland electricity grid. From 1998, five Queensland sugar mills provided an additional 49 megawatts of power a year to the grid under a $70 million 10 year agreement with the Queensland Transmission and Supply Corporation. This was to make more effective use of the heat energy in bagasse and to reduce slightly the quantity of coal burnt at power stations, with consequent reduction in greenhouse gases.
Bagasse is an annually renewable fuel and can also be used as stock feed. Several formulations have been trialed with idea of supplying the feed lot industry. Another possible use for bagasse fibre is the manufacture of paper pulp and fibre board.
Ash and filter mud
Ash and filter mud are used as soil conditioners on cane farms and gardens. Boiler ash is scrubbed from the mill stacks before the exhaust gases are released into the atmosphere. Filter mud is the residue left after the sugar cane juice has been clarified.
Molasses
Molasses is the black syrup remaining after the sugar syrup has been boiled and passed through the centrifugal for the last time in the mill or refinery. About 50 percent of the molasses produced in Australia is exported and the remainder is used in stock feed and in distilleries where industrial alcohol (ethanol), rum and carbon dioxide are made.
Ethanol
Ethanol (Ethyl Alcohol) can be produced from fermented molasses. Industrial grade Ethanol (Power Alcohol) is manufactured from molasses at Sarina by CSR Distilleries Operations Pty Ltd and at Rocky Point by ethanol plant attached to Rocky Point Mill. Ethanol can be used in a number of products including perfume, toiletries, bricks, cleaning products and shoe polish, as well as being used as a fuel.
Bundaberg Distillery uses ethanol from fermented molasses to make rum. Bio-dunder is a waste product of the process and is used as a fertiliser on cane farms.
