BNNZ Miscanthus Biochar Project

TL: FAR miscanthus (still too green)
TR: baled miscanthus, Co/ MiscanthusNZ
BL: flame-cap trench production
BR: miscanthus biochar

Report Co/ Dennis Enright, BNNZ chair

“A plot of mature miscanthus growing at the FAR research centre at Tamahere was offered to BNNZ members to use for a biochar production demonstration and biochar yield assessment.
Miles Pope, Simon Day and Dennis Enright for BNNZ and Peter Brown of MiscanthusNZ met on site on May 21st . We intended harvesting some miscanthus and taking it back to Miles’ yard at Pukekohe to pyrolyse in an open trench as we see this could be an approach that farmers might use.
However we found that the miscanthus still had a high moisture content with tops that were still green, which made it unsuitable for trench flame-cap pyrolysis. It is likely to be August before it is sufficiently dry to pyrolyse, so we will not be using it for demonstration purposes.
Peter had already offered us some bales of dry miscanthus (harvested more than a year ago) so we collected two big circular bales weighing 220 kg and 240 kg with a total estimated volume of 3 cubic metres.
Miles dug a trench with his digger, having dimensions about 0.9 m wide, 0.6 m deep and 4 m long. We then began a fire in the bottom of the trench, and over about 1.5 hours we fed all the miscanthus into the trench. The miscanthus readily pyrolysed and was quenched with water at the conclusion. We produced approximately 1.5 m3 of biochar.”

BNNZ are now hoping that the deferred production of biochar from the FAR block will be progressed after August and that this may lead to crop field trials.

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