University of Ballarat
Project Name: New South Wales Sugar Industry
Location: New South Wales
Theme(s): Energy Alternatives and Reduction, Air and climate change

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BASIC!

Department of the Environment and Heritage

New South Wales Sugar Industry

Renewable Electricity Generation

                                               
   

Ever seen sugar being made? Sugar is a rich source of energy, so it makes sense that sugar factories have been designed to supply their own fuel to make power for their processing. The NSW sugar industry is moving towards generating electricity not only to supply their own power, but to add electricity to the local electricity grid.

As the saying goes…Sugar is Energy !!!

 
           

Contents

This case study is available as a PDF file. You will need Adobe Acrobat Reader installed on your computer to view the PDF file.

In the beginning…

 

 

The NSW Sugar Industry has been operating for more than one hundred years in northern NSW. In 1978 the New South Wales Sugar Milling Co-operative was formed when cane growers purchased the three New South Wales sugar mills:

  • Condong, on the Tweed River;
  • Broadwater, on the Richmond River; and
  • Harwood, on the Clarence River.

At Harwood, the Co-operative also operates a Sugar Refinery. Throughout northern NSW, the sugar industry occupies 30,000 hectares – that's a lot of sugar plants!

Broadwater Sugar Mill on the Richmond
River 		 
                   

The sugar industry has changed over the past one hundred years, but the principles used in the milling process have remained the same. Sugar mills have always been self-sufficient in supplying their own energy.

This model of operation has served the NSW Industry well, but now some change is near because:

  • the old boilers at Condong, built in 1926, have become difficult to operate and maintain;
  • burning the sugar fields before harvesting is an increasing social nuisance; and
  • the current equipment limits the ability to generate surplus renewable electricity for export to the local electricity grid. Excess energy was already being generated by the current setup – before 1990's this was being contributed to the grid with little benefit to the industry.
    Harwood Mill and Refinery on the Clarence River. (Photo courtesy Sunshine Sugar)
               

In the mid 1990's the Federal Government of Australia recognized the need to deregulate the power industry and in 1997 introduced incentives for the generation of renewable energy. A trading system of Renewable Energy Credits (REC's) was introduced by the Federal Office of Renewable Energy where an industry could be paid a premium for the renewable power they added to the national electricity grid.

The Co-operative's senior management recognized that revenue from the sale of renewable electricity would help to:

  1. fund new efficient boilers;
  2. provide a stable secondary source of income for the NSW Sugar Industry; and
  3. improve a number of environmental and social concerns.

“The vision is to maximize the co-generation of renewable energy by harvesting the whole green crop to improve the economic, environmental and social sustainability of the NSW Sugar Industry.”

(Bruce Lamb, Manager Technical Services, NSW Sugar Milling Co-operative Limited)
                                               

A change to renewable electricity generation

This vision requires both time and intensive negotiations.

What is required for the change?

  1. The Co-operative needed a strategic partner who had experience in the power industry. Delta Electricity, a large electricity company in NSW that is partly government owned, agreed to support the change.
  2. Support for funding was required for the project from banks and financial backers. To receive this support, the project had to be well “justified”
    • Economically – they had to prove the economics of the project
    • Environmentally and socially – to obtain approval from the Environmental Protection Authority (EPA), local councils, and the Land and Environment Court.
  3. Significant changes in operation will be required in that:
    1. The power stations would need to operate all year (instead of six months only for the mill operations) for best viability
    2. Instead of burning the crop and leaving leaf matter in the paddock, the whole green crop would need to be harvested in order to provide enough biomass fuel for electricity generation
    3. The change in nature of the crop material would require changes at every step of the supply chain from farm to factory, including:
      • harvesters;
      • in-field bins;
      • road bins;
      • tarping system;
      • the design of a cane/trash separation plant at the factory; and
      • an efficient method had to be developed for harvesting camphor laurel (which is classed as a woody weed) as a supplementary fuel

Gaining approval

Getting the change approved was not a clear process. To gain the approval of the members of the Co-operative, government bodies, and the general public took both time and careful investigation. Some of the hurdles they encountered along the way include the following:

  • The Co-operative is made up of 600 cane farmers and 450 employees. Many meetings were held at all levels of management. The farmers were initially concerned that the harvesters could not cut the green cane. The new system would also mean less “trash” (leaf matter) will remain on the cane field to help with weed control, as the trash and “billet” (chopped up stem) will both be collected and transported to the mill. Engineers for the sugar industry developed harvester modifications to help deal with these problems.
  • Proving the environmental and social benefits of the project – The Environmental Impact Statement (EIS) involved in-depth studies that took 18 months for the Broadwater mill. Once submitted to the EPA and then local council it took time to gain conditional approval. The EIS was then displayed for public comment. The Broadwater Action Group appealed the project, which was dealt with in the Land and Environment Court, resulting in a further 12 months delay.
Timeline to new operations at Condong and Broadwater Mills

1997 – renewable energy promoted by the Federal Office of Renewable Energy.

1997/8 – Managers of Co-operative saw the revenue from generating renewable energy would help to pay for new boilers

1999-2001 – In depth studies for the Environmental Impact Statement (EIS) carried out

2001 December – EIS submitted to EPA

2002 Mar - Dec – submitted to Council, EIS displayed for public comment. Appeal raised by the Broadwater Action Group

2003 February – Project sent to the Land and Environment Council (LEC)

2003 November – Approval received through the LEC. Calling for tenders

2004 early – Tendering finalized and the contract to be signed.

006 June – Plant to be completed and commissioned, ready for the June – December milling season.

 

Find a copy of the Environmental Impact Statement for the “Broadwater Biomass Cogeneration Proposal” at:

www.nswsugar.com.au/Cogeneis/Docs/
Broadwater% 20EIS%20Final%2012-2-02.pdf
                       
 

Broadwater Sugar Mill will undergo changes after the Condong Mill.
     
                                               

What does the change look like?

The main changes to the system occur during harvesting at the cane fields, and on arrival at the mill.

Harvesting and separation

A Traditional Harvest

Traditionally, the sugar cane is burned to reduce the biomass.

Harvester machines traditionally cut the cane into billets (lengths of about 20cm). The leaf matter is separated and remains on the field.
Billets are loaded into infield transporters that tip the billets into 23 tonne bins. These bins are transported to the sugar mill.

 

 

 

(Photos courtesy of Bruce Lamb, Manager Technical Services, Harwood Sugar Mill)

A Green Harvest

A new harvester was designed to cut the green cane. Both the cane and leaves are collected.

Much more biomass will be transported to the mill. Larger road bins for the trucks were designed. A special, easy to erect tarp system was designed to prevent leaf matter (called “trash”) from flying out of the truck during transport.

At the mill, the trash is separated from the billets in a separator called a “Cane/Trash Separation Plant”.

 

 

 

The matter is poured from the truck onto a conveyor belt, gets tossed in the air, and past a stream of air. The leaves (trash) land at one end, cane lands at the other. The trash material is discharged onto the “bagasse conveyor” (see below) where it is to be mixed with the normal fuel for the boiler.

                                               
The Sugar Milling Process

The sugar milling process is outlined below. Click on a section of the diagram to see photos and a description of the process.

The following photos have been taken from Harwood Sugar Mill, the oldest operating mill in Australia, built in 1874. You will notice that the milling train is still partly run by the old steam engines. The photos show the traditional process as Harwood Mill has undergone no changes yet.

(Click to enlarge sections)
   
Shredder
  The billets travel up the carrier to be shredded in a hammer mill. The result is a damp fibrous material.
Milling train
The fibrous material continues through a set of rollers (called a “mill”) that squeezes out the juice. The fibre is then mixed with more dilute juice and squeezed again through another mill. There are four mills at Harwood. The fibre is mixed with more dilute juice at each stage and finally water to wash out the last of the sugar before going through the final mill. This is like a “counter current leaching process” because the water and juice flow in the opposite direction to the fibre.
Bruce Lamb with a new electrical motor that turns one of the rollers. Two of the rollers are powered by large steam turbines, installed in 1874.

Milling produces:

  • a sugary liquid that is sent to the mixed juice tank, then through heaters before entering the clarifier; and
  • the fibrous “bagasse” that contains no more sugar but becomes fuel for the boiler.

Clarifier

The juice goes into a clarifer where the “mud” (and pith from the cane ) is allowed to settle to the bottom. This “mud” is sucked onto a rotating vacuum filter drum (bottom left).
  • The “mud” is sprayed with water to wash out the juice and the sugary liquid goes into the drum.
  • The “mill mud” is collected from the outside of the drum. The ash from the boiler is mixed with the mill mud (above middle) and sent by trucks back to the cane fields as fertilizer (above right).
Evaporators and vacuum pans
  • Clear juice overflows from the top of the clarifier and goes to the evaporators. The juice entering the evaporators is 15% sugar concentration.
  • This is a 5-stage evaporation station. The juice is boiled under vacuum to evaporate water from the sugar solution. Each vessel has slightly higher vacuum. As the vacuum increases, the boiling temperature for the juice decreases. This means the juice does not need to be heated to high temperatures to evaporate the water.
  • The first vessel is heated with steam. The vapour that is boiled off the juice in the first vessel is used to heat the second vessel. The vapour from the juice in the second vessel is used to heat the third vessel, and so on. In this way, for a 5-stage set, only one tonne of steam is needed to evaporate five tonnes of water from the juice.
  • River water is used to condense vapour from the final vessel to create the vacuum
  • The liquor leaving the final vessel has a concentration of 70% sugar.
  • In a vacuum pan, the liquor is “seeded” with a slurry of sugar crystals and held under vacuum at 70 ° C for a couple of hours to allow the crystals to grow at a controlled rate.The thick slurry of large crystals and liquor leaving the pan is called “Massecuite”.
Centrifugals
 

(a) The massecuite enters the centrifuge.

(b) The centrifuge spins at high speed to separate the liquor from the crystals.

(c) The liquor seeps through small holes in the drum, while the sugar crystals are held on the sides of the drum. A scraper can be seen scraping the crystals from the side of the drum. These fall through the bottom and travel to the rotary drier.

(d) The damp sugar crystals.
Rotary sugar drier and storage
  As the sugar is sifted and rotated, the remaining water on the surface of the crystals is evaporated. The dry raw sugar is stored in a storage shed, ready for refining.  
                                               

Production of Electricity

The boiler

 
  • The current boilers are designed for a certain efficiency so there is just enough natural bagasse fuel to run the factory and no excess. The boilers produce enough steam to run the factory's engines and turbines and also for process heating.
  • With the new process, all high pressure steam will be used to generate electricity, and all the motors will be electrical. It is more efficient to use the steam to generate electricity in one big turbine set – this is much like the generation of electricity at a power station.
 
     
  • Each sugar mill will be equipped with a new high pressure boiler to generate electricity for the whole year (apart from 2 weeks for maintenance), 24 hours a day, 7 days a week

Storage of bagasse and trash

Excess bagasse and trash will be stored until needed. During the crushing season (June to December), the excess fuel will be transported away from the mill via an “overland conveyor belt” to a stockpile. When the milling shuts down (between January and May) the conveyor belt will feed the stock-piled fuel to the boiler to allow electricity generation to continue.

Producing “Green” electricity

The amount of electricity generated by steam at each mill will be enough to supply power to a town of 5,000-10,000 population. Each mill will feed electricity to the local electricity grid via new high voltage power lines.

To get an idea of how much green power this is, a total of 400 gigawatt hours of electricity will be generated by two of the mills each year. This electricity generation is considered to be “Greenhouse Gas Neutral” because the carbon dioxide released during burning and stored in the sugar equals the carbon dioxide taken from the atmosphere during photosynthesis. No extra greenhouse gas remains in the atmosphere. Burning coal for electricity releases greenhouse gases into the atmosphere that would otherwise remain locked up in the earth. Burning sugar cane means a saving of 400 gigawatt hours of coal-produced electricity. This is equivalent to 350,000 tonnes of greenhouse gases per year replaced by the renewable energy generated from the two sites.

To put it another way, the same amount of electricity produced by burning coal releases the same amount of greenhouse gas as the gas released by 75,000 cars each year!

                                               

Summary

The changes you will see at each mill are:

  • a new boiler;
  • a conveyer to take trash to the bagasse conveyor to be used as fuel;
  • a conveyor belt over the road to transport trash/bagasse to a stockpile;
  • aeparator to separate trash from billet cane; and
  • new high voltage power lines.

The main benefits are:

  • stable secondary income for the NSW Sugar Industry;
  • elimination of cane fires and cane ash;
  • better working conditions in factories by elimination of old boilers;
  • cleaner boiler emissions; and
  • reduction in the burning of fossil fuels.
Condong and Broadwater Mills are to undergo the change first. Once the installations at the two proposed sites have been commissioned successfully, the vision is to develop the third mill at Harwood along similar lines, thereby completing the change for the whole NSW industry.
                                               

Useful Resources and Contacts

                                               

Acknowledgements

  • Bruce Lamb, Manager Technical Services, NSW Sugar Milling Co-operative Ltd
Photos by Linda Darby unless otherwise indicated

                                             
Content coordinated by Ben Quinney, University of Ballarat. | CRISCOS Provider No 00103D| Disclaimers | Guestbook
Date researched: November 2003 | Case study initially prepared: April 2004