A lot has been written about the benefits of planting trees on farms as part of a property management plan and a regional forest industry development strategy.

Where landholders plan to make commercial returns from farm forestry, it is important to have a strong understanding of the markets for their forestry products. Just like meat, fibre and grain products, forest products require processing before markets will buy them.

Forest processing industries have developed around existing natural forests or large plantation forests and there are limited market openings for small forest growers in Australia. One strategy is for forest growers to process timber on-site at the time of harvesting.

The National Commercial Agroforestry Strategy identified that limited information about the viability and management of on-site processing was a barrier to widespread adoption of farm forestry. So the Joint Venture Agroforestry Research and Development Program (JVAP) commissioned research to investigate utilisation practices for the farm forester. The research was managed by RIRDC.
 

Background

JVAP research into utilisation practices for the farm forester found that the on-site processing system with the greatest potential is portable sawmilling. This is because the returns for sawn timber can be high, and the costs associated with operating a portable sawmill can be relatively low.

Twenty-five portable sawmill operators in Victoria, and 14 portable sawmill manufacturers, were interviewed during implementation of the JVAP research project. This provided an understanding of issues involved with owning and operating a portable sawmill so that the true costs of on-site sawn timber production and its potential returns could be assessed. The JVAP research compared the level of automation, the productivity, and prices of portable sawmill systems.

Information gathered from the JVAP research was used to construct scenarios that indicate conditions which have to be met for a viable portable sawmilling enterprise.

Portable Sawmilling
Portable sawmilling is taken to include production of green, air-dry and kiln-dry sawn timber using sawmilling equipment which is taken to the farm forestry site, operated there, and then dismantled. The JVAP research found that nearly half the portable sawmill operations in Victoria are contract sawmillers on farm foresters.

There are numerous portable sawmills on the Australian market, ranging from simple lightweight frames to which a chainsaw can be attached, to complex horizontal band saw mills, single circular saw units and twin circular saw units.

There are also benchsaws consisting of a stationary headrig and a carriage onto which sawlogs are placed and subsequently moved through the saw. In general, the JVAP research found that the most productive sawmills possess the highest level of automation, and these are relatively expensive.

Portable sawmills have the potential to contribute to both industrial-scale and farm forestry. At an industrial scale, portable sawmills have the potential to use timber resulting from salvage operations following natural disasters and commercial harvesting operations in existing forests.

At a farm forestry scale, portable sawmills have the potential to deal effectively with small-scale and relatively isolated plantings which have not attracted industrial-scale timber processors.

Advantages of portable sawmilling are widely documented and include:

• supplying niche markets which cannot be served from industrial processors;
• adding value to farm forestry timber on the farm, thus capturing more margin for the forest grower;
• return of residues such as bark, sawdust and edgings to the forest site;
• flexibility to meet changing local demand and supply opportunistic markets;
• reducing logs to commercially recoverable timber an-site to reduce transport costs;
• harvesting and milling timber in otherwise inaccessible sites; and
• harvesting and milling timber from plantings which would otherwise be too small.

Nevertheless, portable sawmills have a number of disadvantages, including relatively low productivity, high labour intensity, and a requirement for heavy lifting at or close to ground level. In addition, the working environment may not conform with best industry practise for occupational health and safety.

The dimensional accuracy and product finish of timber sawn with portable sawmills may not be of as high quality as timber from industrial-scale mills. Similarly, portable sawmills are unlikely to be able to handle small diameter sawlogs from rapidly grown eucalypts with their associated high internal growth stresses.

The full report of the JVAP Research presents detailed findings from a survey of portable sawmills. The survey found that:

• Chainsaw mills - are cheap but labour intensive with low conversion percentage (because of wide saw kerf), a need for double handling and poor timber finish.
• Horizontal bandsaw mills - have high conversion percentages because of a narrow saw kerf and consequently relatively low fuel consumption and can cut wide logs, but these mills require two passes to produce dimensional timber and bandsaw blades require frequent sharpening and setting and are prone to damage in hardwoods.
• Single circular saws - have low power requirements and produce dimensional timber with two passes of the saw over the log but have a wider saw kerf than bandsaws and are labour intensive because they have a low level of automation.
• Double circular saws - can handle very large logs, cut dimensional timber with one pass of the saw and have a facility to return sawn timber to the operator with the return of the saw carriage, but also possess a relatively wide saw kerf and have difficulty in managing partially sawn logs.
• One-person bench sawmills - these portable mills enable accurate sizing of products, have high productivity and have labour saving log handling facilities; but are relatively expensive and are the least mobile of the portable sawmills surveyed.

The JVAP research compared the level of automation per $1000 of sawmill purchase prices for different portable sawmills. This suggested that the lower priced sawmills such as single circular saws offer more value for money than more expensive sawmills such as some double circular saws.

Table 1 summarises the main advantages of particular types of portable sawmills.
 

Table 1: Main advantages of Differenet Portable Sawnmills
 

Sawmill category

Main advantages

Chainsaw mills   Horizontal bandsaw mills     Single circular sawmills     Twin circular sawmills   Bench-type units

Rugged and relatively inexpensive Extremely portable Safe Increased timber recovery Simple production of slabs and wide boards Competitive prices, good value for money Able to handle difficult timbers Relatively low amount of sawlog handling required Powered saw carriage reduces physical work required Sawn timber return facility reduces labour requirements High productivity makes it suitable for large volumes of low value timber

Financial Analysis

• the additional equipment required before sawmilling can begin;
• the sawn timber needs of potential markets;
• matching the sawmill to likely timber resources; and
• labour requirements to load, mill, stack and market timber.

Many potential costs are not considered before a portable sawmill is purchased - for example the time required for producing and marketing sawn timber, safety and log handling equipment, sawlog supply costs, and storage and handling costs for sawn timber. Figure 1 shows the typical distribution of costs for a softwood sawmill.
 

The cost of sawlogs used by a sawmill is usually the highest single cost of sawn timber production - often amounting to 60 percent of total costs. Softwood stumpage, harvest and transport typically costs around $50/m3. Hardwood stumpage, harvest and transport typically costs between $30 and $100/m3 depending on species and quality.

To ensure high returns from quality timber, sawlogs should be processed as soon as possible after felling, especially during warm weather.

The actual time spent sawing is a small proportion of the total time spent producing sawn timber. Therefore, the layout of the site for portable sawmilling should ensure that log supply, loading, and timber handling are as rapid as possible. Log loading is required only for portable mils with a bed or carriage. When using other types of mills, log positioning is the most important issue.

The JVAP research analysed the costs and break-even values for different portable sawmilling options. The details are available in the full report. Figure 2 shows the break-even volumes for individual portable sawmills surveyed.

Figure 2 shows that portable sawmilling is financially feasible if certain conditions are met, not least of which are the availability os sufficient volumes of sawlogs and competitive prices for sawn timber. The smaller break-even volume for hardwood enterprises in all cases highlights the benefits of targeting high value species.
 
 

However, the technical limitations of milling certain species, such as high internal growth stresses in small eucalypt logs, may make infeasible the processing of sufficient quantities of high value sawn timber. Note that the break-even analysis summarised in Figure 2 does not allow for labour costs - on the assumption that owner operators are making the comparison.

The relatively low productivity of portable sawmills means that the production of industrial wood products may be difficult to achieve competitively. Both milling for high throughput and milling for high recovery highlight the labour intensiveness of portable sawmilling enterprises. There is a tradeoff between productivity and capital outlay requirements in portable sawmilling. The targeting of high value species and products is the most viable proposition for portable sawmilling operators.
 

Occupational Health and Safety Issues

The loading and handling of sawlogs and sawn timber can result in injury because heavy lifting is often required. Circular saw mills which move across a log set in position on the ground reduce the risk of lifting injuries.

The noise levels around portable sawmills are high and so sawmill operators should use hearing protection.
Sawdust moved around by wind and draughts can create respiratory and eye problems in operators, as can exhaust fumes. Mills with cable controls such as twin circular sawmills are advantageous because the operator is removed from the carriage when it is passing through the log - thus distancing the operator from exhaust fumes and sawdust.

Related to portable sawmills safety is the issue of sawmill training. Only 2 of the 6 Australian sawmills manufacturers surveyed in the JVAP research offer training. Since many sawmill contractors using portable sawmills have no previous sawmilling experience, there is a need for vocational training. At the moment this training is available from the Logging Industry Training Centre in Mount Gambier and the Victorian Timber Industry Training Centre (VTITC) in Creswick.
 

Marketing Considerations

Many of the problems encountered by farm foresters with respect to sawlogs and other forest products may simply be pushed along the processing stream if potential products and markets are not carefully considered.

The return for sawn timber is greatly influenced by the sawmilling strategies used, the type of logs sawn, the management of the operation, and the handling and grading of sawn timber.
 

Sawmilling Strategies

Backsawing - production of boards with faces roughly tangential to annual growth rings - is quicker than quarter sawing and permits easier handling of growth stresses. Quarter sawing - cutting boards with faces parallel to the rays - produces boards with a more decorative appearance and less cupping, warping and shrinkage that backsawn boards.

Live sawing - cutting a face, sitting the log on that face and then cutting boards from the positioned log - is possible with chainsaw mills, horizontal bandsaw mills, and bench-type circular saws.

Backsawn and quarter sawn boards are most easily done with single and twin circular sawmills, but it is possible with chainsaw mills, horizontal bandsaw mills, and bench-type circular saws with frequent log repositioning.

Split taper sawing - parallel to the central axis of the log - is the most common longitudinal cutting strategy employed with portable sawmilling and results in least wastage.
 

Type of Logs Sawn

Management of the Operation

Handling Sawn Timber

Options available include:

• Air drying - freshly processed timber is stacked under shelter and allowed to dry slowly to a moisture content in equilibrium with the surrounding atmosphere, typically between 6 and 20 percent. Stacks should be sited so that they are parallel to the prevailing wind to ensure even drying throughout the stack. Ideally, a stack should be 1.2m wide and 2.4m high. To prevent degrades associated with air drying is end checking and splitting due to uneven drying. Application of a sealant to the ends of boards or draping a tarpaulin over the ends of the stack reduces the risk of end checking.
• Kiln drying - this allows more rapid drying than sir drying but requires greater technical skill and involves higher capital investment. Because of the control it allows, kiln drying can be used to target specific market needs. Conventional kiln drying is unlikely to be appropriate for portable sawmill operators because of its cost. Alternatives are dehumidification and solar type kilns.
• Dehumidification drying - these use a heat pump consisting of an evaporator, condenser, compressor and control system, to remove moisture from a kiln using circulating air which alternatively heats/dries and then cools/releases moisture outside. This form of drying is easy to operate and energy efficient but can take longer and requires electricity rather than alternative sources of energy.
• Solar drying - greenhouse type kilns and external collector type kilns fall into the solar drying category since they generally rely on solar heated air as the drying medium. To be effective, solar kilns require careful design to balance the ratio of collector area to the capacity of the kiln. However, well designed kilns have been found to require 1.5 to 3 times less drying time than air dried timber. In addition, solar drying has been found to result in less drying degrade because of diurnal fluctuations in temperature.

Grading Sawn Timber

• Appearance grade - based on the visual characteristics of the timber and relating generally to boards less than 50 mm thick.
• Structural grade - based on feature affecting the strength, stiffness and practical requirements of structural applications and relating to dimension stock and timbers greater than 50 mm in thickness.

Mechanical stress and machine proof grading are more accurate and time efficient than visual stress grading. A portable sawmiller wishing to produce structural timber can obtain a visual stress grading ticket from the VTITC.