What is wood fuel?
What is wood energy?
Wood energy in the form of heat is created from the combustion of biomass fuel (solid biofuel). In New Zealand biomass fuel is generally referred to as wood fuel because wood is the primary source of the biomass.
What is biomass (wood) fuel?
Biomass fuel (solid biofuel) is sourced from wood or herbaceous biomass (biological material derived from living, or recently living organisms).
Solid biofuel comes in a number of forms, including firewood, shavings, sawdust, wood chips, wood pellets, agricultural crops such as miscanthus and bark.
Solid biofuel from herbaceous material
Agricultural crops such as miscanthus and straw from cereal crops can be used as a fuel for production of heat. Herbaceous material has a different composition from wood and its combustion must be handled differently from that of wood.
Solid biofuel from waste
Community based organic solid waste from urban landscaping, manufacturing and community forests can be used directly as a biomass fuel. However, it often has a large amount of green matter which means that it has a high moisture content and thus a poor grade of fuel. It can be blended with better grades of solid biofuel to get an appropriate overall moisture content or diverted to composting.
Organic municipal solid waste can be pelletised and used as a combustion fuel. The pellets are often around 20-30mm diameter. The moisture content of the pellets can be adjusted by the amount of dry paper etc that is included in the feedstock.
Solid biofuel quality standards
The quality of solid biofuels is critical to their use. All heat plant is designed for specific types and ranges of fuel characteristics. Not all biomass fuel is the same. Biomass sourced from forest harvest residues, wood processing or agricultural residues will generally require treatment before it is suitable to be used as a fuel. The treatment may involve drying, commutation or screening.
Suppliers of biomass fuel must produce and supply the fuel to the specifications set out in their fuel supply contract.
- The fuel specification should be based on the biomas characteristics set out in Technical Guide 1 ‘Solid biofuel classification guidelines’.
- The methods of verifying that the fuel delivered is that specified in the fuel supply contract is set out in Technical Guide 5 ‘Standard methods for verifying the quality of solid biofuel’.
- Guidance on the overall sale and purchase of biomass fuel is set out in Technical Guide 6 ’Contracting to deliver quality biomass fuel to customers’.