Waste plastic solution

Almost every day in the newspapers and on TV we see something about the waste plastic issue, with shots of what seem to be large quantities of baled waste plastic that are looking for a home. The loss of China as a dumping ground for this material has caused people to start talking about taking responsibility for dealing with this apparent mountain of waste plastic in their own backyard. But so far it is just that - talk.

The decision-makers need to know that the solution is already available. For some time Miscanthus New Zealand Limited (MNZ) has been promoting the establishment in New Zealand of stands of the sterile giant woody perennial grass called Miscanthus for a whole variety of commercial uses. One of these uses is for the production of renewable diesel. When the waste plastic issue started being publicised after China had been closed off as a place to dump it, Managing Director of MNZ, Peter Brown, asked the renewable diesel technology owners whether renewable diesel could be made from waste plastic. The answer he received was quite positive.

“We were told that renewable diesel can be made with feedstock that has up to 20% waste plastic content. All plastic is able to be included other than PVC” Brown stated.

“The other 80% has to be biomass and of course we know that an ideal better-than-carbon-neutral biomass for this purpose is Miscanthus. However we are also realistic enough to acknowledge that radiata pine processing residues, wood chips, and even cereal straw can also be used to provide the 80% of biomass that is required.”

Standard renewable diesel plants - which are at a small enough scale that they can be established regionally - require only 50,000 tonnes (dry matter) of feedstock per year. That may sound like a lot but if we assume 20% of a forest harvest is in lower quality pulp logs and half of the rest ends up as forest industry processing residue – local processing of course - this quantity of feedstock can be produced from only about 300 ha of harvested radiata pine forest each year. It can also be produced on an ongoing basis from only 2,500 hectares of Miscanthus. In addition, it appears that Canterbury has about 2 million tonnes of cereal straw going to waste each year. This too could be a valuable feedstock to go with the local waste plastic.

MNZ and its associated companies are also already working on establishing the economics of a renewable diesel plant that is half that size so that it is even more attractive to smaller regions, and indeed to various Pacific Island communities.

Brown commented “We suspect that once this challenge has been picked up and run with, not only will renewable diesel be being produced in New Zealand at a very competitive price that can be fixed for the coming year or even longer if desired, but the waste plastic ‘mountain’ will prove to be only a small part of the national renewable diesel feedstock resource.”

“In the future, whatever waste plastic is generated and accumulated, it will be able to be fed into a locally based renewable diesel production plant and turned into a better-than-carbon-neutral fuel, i.e. renewable diesel. All that it is required is commercial commitment from an appropriately funded business entity that is interested in securing a carbon-neutral future for New Zealand while at the same time, making a good return on its investment. The government has shown that it is not interested at all because the various ministers who should be involved have completely ignored information that has been sent to them by different interested parties.”

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