Arsenic charcoal won’t be fuelling BBQS
A pyrolysis plant boss has assured critics that arsenic-laden charcoal will not be ending up in anyone’s barbecue.
The charcoal would be produced by a pyrolysis plant proposed for Blenheim, intended to reduce timber going to landfill by turning it into charcoal in a low-temperature oxygen-free industrial furnace.
The plant was proposed as a way to get rid of thousands of stockpiled vineyard posts across Marlborough, which were treated with copper chrome arsenic and potentially leaching chemicals into the soil.
The charcoal, which would retain most of the arsenic from treated timber, would then be sold commercially, the plant’s resource consent application said.
But as submissions on the application roll in, an energy consultant, who would not be named, said he doubted there would be many buyers for the charcoal due to the high concentration of arsenic.
Burning the charcoal, for example to fuel a furnace, would release arsenic into the air, he said.
‘‘You would need really hightech and fairly expensive equipment to filter emissions, and it would have to be monitored really carefully to make sure that works properly,’’ the consultant said.
He described a filtration system called ‘‘scrubbers’’, that involved a shower of ‘‘finely divided water droplets’’ in a ‘‘special chimney’’, which arsenic stuck to instead of being discharged directly to the air.
The water would then need to be treated, he said.
‘‘By this point you’ve sort of swallowed the spider to catch the fly, haven’t you? And even then you still haven’t solved the nightmare problem of toxic fly ash. You don’t want that building up in occupied areas.
‘‘It wouldn’t take very much fly ash from the smoke stack to increase the arsenic levels beyond the guidelines for soil for residential lifestyle blocks nearby.’’
Charcoal was an expensive end product and most people fuelled industrial heating or boilers tended to use wood waste instead, a cheaper and easily available fuel, the consultant said. He was not aware of any regulations about chemicals in barbecue charcoal sold domestically, he said.
‘‘I have heard of examples where people have burnt charcoal made from Cca-treated timber unwittingly and got a green flame. But that’s an extreme case.’’
Waste Transformation Ltd chief executive Mike Henare said charcoal had ‘‘many uses’’ besides barbecue fuel, though that was the primary market in New Zealand.
He already sold charcoal from his Timaru plant, which pyrolysed mostly untreated timber. The resource consent did not say what the charcoal would be sold for, but Henare said it would not sold as barbecue charcoal.
‘‘To be sold in this market it needs to be suitable for food preparation, which ours is not, so we do not sell into this market,’’ Henare said.
‘‘Even charcoal we manufacture from untreated timber is still not sold into this market, as in our view may still carry the risk of contaminants. Our untreated timber charcoal is currently sold as a coal replacement in industrial and home heating.’’
He would not reveal the companies he was considering selling the charcoal from the Blenheim plant to, citing commercial sensitivity, but none of them would be using it as fuel, he said.
The consultant also raised concerns about the storage of the charcoal at the Bluegums Landfill, where it would be stored in an open shed for at least eight days before being transported by truck.
‘‘For the transport of the charcoal alone you would need extensive health and safety regulation. It would be a hazardous substance. You would have to be cautious over dust generation - are workers exposed to the charcoal dust? It may be more prone to wind dispersal than other products. That should all be acknowledged in the application,’’ the consultant said.
‘‘People can’t leave their heads in the sand about the future of the product. That must be addressed.’’
Submissions close on April 16.