Sawmiller FAQs
Q: How much of my timber can I dry with energy produced from my very own waste streams?
As a rule of thumb, between two-thirds and three-quarters
of total timber production can be kiln dried with steam produced from
onsite waste streams such as sawdust, bark and shavings. For more
information on the energy extractible from your wood waste streams try
our biomass calorific value calculator.
Q: Which waste stream is best for combustion?
All sawmill waste streams have different pros and cons for combustion.
Sawdust is a good clean fuel with very low ash content (about 1%),
as long as it is handled correctly to avoid soil contamination (i.e.
dirt). It has a very high moisture content which reduces its net
calorific value.
Bark has a lower moisture content, which increases it's net
calorific value, but it tends to be highly contaminated (i.e. dirty).
This results in high ash production that can cause problems in the
combustion stage.
Dry wood shavings have the highest fuel value at around 21 GJ/tonne
and are usually a clean, low-ash fuel. Their very low bulk
density leads to problems, in conveying systems, and large storage
facilities. Handling systems need to be designed specifically around
these characteristics. For more information on the energy value of
different fuels and how this depends on moisture content try our biomass calorific value calculator.
Q: Can wood-waste fuels be mixed together prior to combustion?
With modern combustion technologies it is often advantageous to
create a mix of waste streams if this can be done consistently. This
mix can give a higher fuel value than the lowest individual
feedstock. It can also improve the handling characteristics of
the fuel. In particular, fluidised bed boilers
are designed to burn low value fuels with a range of moisture contents
and particle sizes. For more information see the main section on utilising wood waste.
Q: What percentage of my wood flow is usable for heat generation?
Approximately 15% of a sawlog can be utilised as fuel, this includes
bark, wet sawdust and dry shavings. In addition, off-cuts can be hogged
or chipped to use as fuel.
In many places there is a market for pulp chip, however, market
fluctuations, and particular circumstances may make it more likely that
chip is used as a fuel. To investigate further options for your wood
waste use our on-site biomass assement tool.
For mor information on any of these topics talk directly to a expert at the bioenergy call centre: 0800 BIOENERGY (0800-246363). Alternatively you can visit the main FAQ section of the BKC portal.