As well as being a substrate in itself sawdust can also be used to create spawn for inoculation of other substrates such as logs or straw. Often when used a substrate, sawdust is enriched with a source nitrogen such as wheat bran to increase yeilds, this then requires sterilisation. However, there is no need to enrich spawn and therefore you can avoid more energy intensive processes of sterilisation.
Grading the sawdust appropiately is important especially if the intended use is log inoculation as large particles/shavings will not easily fill the palm inoculators (for more discussion on grading sawdust see here: Enriched Sawdust Blocks)
By far the easiest way to make sawdust spawn is to use wood pellets. This is a process of adding pellets to water at a ratio of 1:1 by volume. Using polypropylene bags as the container allows you to use hot water, this will also decrease the chances of contamination. Once cooled you can an add the optimum amount of grain spawn (10-20% by dry weight of substrate).
The one potential drawback to using pellets is the difficulty of acquiring hardwood pellets. However, the fact that the pellets used are softwood doesn’t seem to effect the performance of the spawn.