Wood processor FAQs
- Why should I consider using wood as energy for my wood processing operation?
- How much of my timber can I dry with energy produced from my wood waste?
- Which wood waste stream is best for energy production?
- Can wood waste fuel types be mixed together prior to combustion?
- What percentage of my wood waste is usable for heat generation?
The use of wood energy is an attractive option as it can provide economic and environmental benefits to your business and New Zealand as a whole. Find out more about the economic and environmental benefits of using wood as energy.
As a rule of thumb, between two-thirds and three-quarters of total timber production can be kiln dried with steam produced from onsite wood waste such as sawdust, bark and shavings. Use the biomass calorific value calculator to calculate the amount of energy you can extract from your wood waste.
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). However, it has a very high moisture content which reduces its net calorific value.
- Bark has a lower moisture content, which increases its 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. However, 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. Use the biomass calorific value calculator to calculate the energy value of different fuel types with varying moisture content levels.
With modern combustion technologies it is often beneficial 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 fuel types. 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. Find out more about wood energy options on the wood energy options for industry page.
Approximately 15% of a log 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 options for your wood waste use our biomass assessment tool.