Producing biomass: Biomass types: Tree residue: Sawmill residue
About half of the wood arriving at Australian mills for processing becomes a finished product. The remainder is residue, or waste. Residue includes sawdust, woodchip, bark, planer shavings, and pole shavings that accumulate at milling sites.

There is potential in the forest products industry to use sawmill residue to generate energy onsite or at a local bioenergy plant.

Evaluating the economics

Processing tree logs into uniform sizes, such as timber planks, produces significant waste – about 50 per cent of a log is left over as waste. The sawmill industry aims to minimise this waste and, if possible, to market it as ‘low value sawmill by-products’.

A 2011 study by RIRDC, Facilitating the adoption of biomass co-firing for power generation, found that sawmills in Queensland use a significant volume of wood by-products onsite to produce heat for drying timber.

Power generation is another option considered by some Queensland mills, particularly cypress pine processors located in western parts of the state where distance excludes supplying these by-products for other markets, such as landscaping.
Wescor sawmill, Gympie. The sawmill runs partly on bioenergy produced from sawdust. Photo John McGrath, FFI CRC.
Transportation is a major limitation for all biomass producers, according to the report.

The cost of transporting biomass 50–200 km is estimated at $12–$46 per tonne. Unless a power station is within 200 km, transport alone may represent more than 50 per cent of the total cost for producers.

Other factors that affect the price of sawmill residue include:
  • type and size of residue (whether its fine sawdust or larger shavings from softwood or hardwood)
  • uniformity and predictability of residue supply
  • hygiene of residue
  • moisture content and/or whether the residue is decomposing
  • scale of the value added by the biorefinery (e.g. high value chemicals vs. energy vs. commodity chemicals)
  • competing markets, such as the landscaping sector

Benefits

Bioenergy systems that operate onsite at a sawmill can generate clean, sustainable and cheap heat and power.

Sawmills also have the option of selling their wood milling wastes to bioenergy power stations.

An example of a forestry and sawmill residue feedstock project is described in Section 5.4 (page 73) of the report, A bio-energy roadmap for South Australia, which was prepared for the state government in August 2015.

The report also describes the technology options for producing energy from forestry and sawmill residues and outlines the main issues that need to be considered

Supplying

A guide to handling wood by-products for use in bioenergy [PDF, 2.2 MB], published by RIRDC, is useful for sawmill and wood processing facilities that produce sawdust, wood shavings and chip fines, that could be used as bioenergy feedstock.

The guide looks at:
  • desired qualities of wood by-products (biomass)
  • grinding wood pieces to optimal size for bioenergy plant
  • managing biomass moisture
  • maintaining biomass hygiene
  • sorting, segregating and storing biomass
  • loading biomass
  • adapting existing operations


The guide is based on a Biomass fuelwood study [PDF, 1.4 MB] conducted by South East Fibre Exports in 2011. The study was supported by the Australian Forest Products Association and the Department of Agriculture, Fisheries and Forestry.
The study aimed to:
  • model predicted woody biomass produced by 9 timber processing facilities in eastern Victoria and south-eastern NSW and the likely costs of collection
  • analyse optimal physical and chemical properties of woody biomass fuel
  • estimate operating costs
  • produce best-practice guidelines for producing wood biomass for bioenergy
  • consider knowledge gaps, risks and opportunities

Storing and transporting

Ensuring wood by-products are stored properly on-site at sawmills will increase the revenue that sawmill operators can make when selling to bioenergy power stations.

Both the Biomass fuelwood study[PDF] and A guide to handling wood by-products for use in bioenergy[PDF] offer key points for suppliers to consider when either building new storage or adapting current bunker storage systems.

When storing sawmill residue:
  • install overhead conveyors to directly feed bunkers or overhead hoppers
  • keep bunkers covered so that residue doesn’t get exposed to rain
  • concrete bunker floors to avoid contaminating residue with soil and stones.
  • allow for easy access to bunkers by trucks and other large vehicles, such as loaders.


The study and guide also provide key points to consider when loading residue into trucks for transporting.

When loading residue:
  • use a front-end loader
  • install ramps to improve efficiency when loading trucks with a front loader
  • install overhead hoppers to load trucks quickly and efficiently.

Contacts

David Hall

Energy Developments and Resources (EDR)

4 Glenneth Court, Bonny Hills NSW 2445,
Phone: +61 (0)2 6585 5368

david.hall@energydr.com.au
Martin Moroni

Private Forests Tasmania

30 Patrick Street, Hobart 7000,
Phone: 0361654073

admin@pft.tas.gov.au
Simon Penfold – Woody Biomass

African Mahogany Australia / Australian Bioenergy Partners

12 Churchill Court, East Brighton, Vic 3187,
Phone: 0488009843

Simon.penfold@ambrazil.com.au
Giles Perryman – Refgas Australia

Refgas Australia

Dunsborough, WA. 6281,
Phone: 0447 393 363

refgas@askwm.com
Fabiano Ximenes

Forest Science - Department of Industry - Lands

level 12, 10 Valentine Ave, Parramatta NSW 2150,
Phone: 0458760812

fabiano.ximenes@dpi.nsw.gov.au
Col Stucley

Enecon

Suite 5, 651 Canterbury Road, Surrey Hills, Victoria 3127
Phone: +61 (03) 9895 1250

cstucley@enecon.com.au
Mohammad Reza Ghaffariyan

Forest Industries Research Centre (FIRC) University of the Sunshine Coast

Sippy Downs, Qld 4556
Phone: 07 5456 5447

mghaffar@usc.edu.au
EDR Energy Development and Resources Pty Ltd.

Contact: David Hall

4 Glenneth Court, Bonny Hills, NSW 2445
Phone: +61 (0) 26585 5368 and +61 418206293

david.hall@energydr.com.au
Gavin Matthew

Australian Forest Products Association

Deakin West, Australian Capital Territory, 2600,
Phone: 02 6285 3833

Gavin.matthew@ausfpa.com.au
Peter Mitchell

South East Fibre Exports

Jews Head, Edrom Road, Eden, New South Wales, 2551,
Phone: 02 6496 2200

peterm@sefe.com.au