Greenhouse gas emissions and wood pellet fuel
In New Zealand, wood pellet fuel is 100% made from waste sawdust and wood shavings, bi-products of the timber milling industry in this country. There are minimal alternative uses for these waste products, a large proportion of which is currently burnt at the saw mills in kilns to dry wood before processing. Transforming the waste sawdust in to an easily transportable, energy dense, very low carbon fuel is widely considered to be the best environmental and economic outcome. In addition, there are hundreds of thousands of tonnes of waste wood from the construction industry that are currently being landfilled in NZ and could instead be made in to wood pellets or chip as a renewable fuel.
Being made from waste materials, as opposed to still living trees, wood pellets in NZ have extremely low embedded carbon dioxide. This is especially in comparison to fossil fuels and even compared to NZ electricity which is mainly renewable. All energy sources in NZ have a greenhouse gas emission factor which is reviewed annually and published by the Ministry for the Environment in the Measuring Emissions guide. Wood pellets appear in this guide under “industrial wood” with an emission factor of 0.0150 kg CO2-e/kg. Pellets have an ISO certified energy density of at least 5.1 kWh/kg therefore the CO2 emission factor per kWh is 0.0029 kg CO2-e/kWh.
CO2 emissions from using pellet fuel in NZ compared to other common fuels are -99% vs coal & diesel, -98% vs gas, -97% vs electricity.
There are internationally agreed rules when accounting for carbon emissions, in the same way as there are rules governing the accounting of money. The MfE Emissions Factors are calculated under these rules. The bulk carbon (energy source) contained in wood pellet fuel has already been accounted for during the timber processing and included in wood as a building product. Therefore, only the carbon emissions from the manufacture and transport of the wood pellets are considered as a direct emission when burning wood pellets, returning the CO2 to the atmosphere.
As the carbon emissions from wood pellets are solely from the manufacture and transport of pellets, more efficient manufacturing and shorter freight distances results in lower carbon emissions. Wood pellets are manufactured in three locations in NZ with a good geographical spread of the country, facilitating shorter delivery distances – Taupo (Nature’s Flame), Nelson (Azwood) and Invercargill (Niagara). At Nature’s Flame, the largest pellet manufacturer in NZ, the waste sawdust is dried using waste geothermal heat before reinjection in to the geothermal well by Contact Energy. At Azwood and Niagara the sawdust for wood pellets is dried by burning waste sawdust and shavings from timber processing.
Particulate emissions and ÖkoFEN pellet boilers
ÖkoFEN pellet boilers are designed, tested, manufactured and certified in the EU which has some of the most stringent air quality standards in the world.
All pellet boilers from Apricus NZ Eco Energy meet the air quality requirements of the NZ National Environmental Standards for Air Quality.
Domestic pellet boiler models are certified to Environment Canterbury and Nelson City Councils Ultra Low Emission Pellet Boilers (ULEPB) requirements. This includes particulate emissions for their entire operating cycle, including start up and burn down operation. The registration for Apricus Easypell boilers can be found for ECAN and Nelson City Council.
Boilers larger than 40kW are not included in the ULEPB scheme and are individually consented. Commercial scale ÖkoFEN boilers are designed and consented to meet the air quality requirements of the relevant Regional Council Air Quality plans.
The flues of all ÖkoFEN pellet boilers are designed and installed to direct all emissions away from ground level and other buildings, minimising particulate emissions to the local environment.
ÖkoFEN pellet boilers have extremely low particulate emissions, particularly their innovative flue gas condensing models. The particulate emissions in the flue gas of the boilers are:
3mg/m3 for ÖkoFEN Pellematic condensing boiler (PESK64)
17mg/m3 for ÖkoFEN Pellematic standard efficiency boiler (PES56)
These particulate emissions are respectively 2% (condensing) and 15% (standard) of the particulate emissions of a Clean Air Approved domestic wood burner at 1g/kg fuel burned (equivalent to around 115mg/m3 flue gas). Wood fires are a significant emitter of particulate emissions in NZ during winter, whilst diesel engines are the other main source of particulate pollution, especially outside of the heating season and in NZs larger cities.
The latest ÖkoFEN boilers have an innovative ZeroFlame option that reduces particulate emissions down to levels that are almost unmeasurable, at 2mg/m3 over nine hours operation or 0.22mg/m3 per hour. This is 90% less than the already extremely low condensing boiler particulate emissions. This is available on the smaller models and will be rolled out to larger models over time.
More information on these topics can be found here:
NZ wood fuel – Bioenergy Association
The State of Air Quality in New Zealand – Parliamentary Commissioner for the Environment
ÖkoFEN condensing boiler technology – ÖkoFEN
ÖkoFEN boilers technical specifications – Apricus NZ
Here is a visual comparison of the latest ÖkoFEN pellet boiler technology with other sources of particulate emissions from a household over a year: