MOTAT was recently presented with an award from FRONZ for our efforts to introduce sustainable fuels into our operations along with a $1000 to go towards the cause.
We started down this track two years ago with a visit to SCION (the Forestry Research Institute in Rotorua) to find out more about a product - torrefied wood pellets - they were making on a lab. scale from waste forestry slash. Use of this material for a fuel appealed at the time with slash presently being a waste product and causing untold damage when the motu is subject to severe flooding.
More importantly though it can be a sustainable, recyclable product provided the forests are renewed. Sure, you can argue you produce CO2 when you burn it but if the forests are replanted the CO2 gets reabsorbed by the growing trees in an ongoing cycle so there is a constant balance.
On the other hand, burning fossil fuels add incrementally to the total carbon dioxide already in the atmosphere and we are all becoming painfully aware of what this is doing to our weather.
The load of torrefied pellets made for us by SCION was burnt in 100 in a carefully monitored trial which impressed us all at the time - good steaming capability with little smoke and ash - generally a cleaner operation all round. We used around 30% more fuel than for the equivalent operation on coal.
We should be able to improve on this consumption when we have access to a completely torrefied product with a heat value similar to coal. Unfortunately, no manufacturing plants are in operation in NZ producing this product yet.
In the meantime, both the MOTAT boiler house and 100 are running on another waste product. This is made from compressed Vitex sawdust and is in the form of 50mm diameter pieces not to dissimilar to lumps of coal. Again, the calorific value isn't as good as torrefied wood or coal but Vitex like our native Puriwi, is one of the hottest burning wood's around.
Provided we keep this product out of the rain we are both getting a good result burning this substitute fuel.
Our operations are much cleaner with reduced smoke and smell and an ash that is valuable for gardens rather than a toxic sulphurous waste we were dumping as landfill previously.
Other heritage boiler users are watching our progress keenly as coal is gradually phased out and none of us want to see our heritage steam treasures relegated to cold, rusting, lifeless museum pieces.
A group of us recently returned to SCION for an update on torrefaction and progress towards making this fuel in NZ.
A new business venture - Foresta NZ - is well underway with plans to set up the first commercial plant in the Kawerau - Rotorua area shortly. We had a discussion with their management in their Tauranga office on the same day we visited SCION.
Following on from this first plant, Foresta's plans are to build a number of identical plants alongside all the major exotic forest areas in NZ. First product is probably two years away and if we can talk them into compressing into coal sized lumps our future fuel needs will be solved.
By Tony Messenger
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