Gathering power from a weed

KATRINA BIELESKI/Waikato Times

PROJECT: Shane Carter wants to turn aquatic weed into an energy source.

Shane Carter wants to turn a pest plant into a power source.

Mr Carter, a Waikato University chemistry and engineering PhD candidate, is working on a project which could see small lake or riverside communities potentially generating their own energy from the anaerobic digestion of a common aquatic weed.

He has also been awarded the $107,000 Te Tipu Putaiao (TTP) Fellowship by the Foundation for Science, Research and Technology to advance the project, which he has been working on for six months.

Mr Carter already holds several science and engineering qualifications, and operates his own business, and he will be putting those skills to use as he looks to advance his water weed project.

For his PhD, he has been harvesting a few kilograms of oxygen weed (also known as hornwort and elodea) from lakes near Rotorua. The weed is then dried before being put in a small digester– currently a Tupperware container – where the anaerobic digestion takes place. He is currently working on various possible methods of anaerobic digestion, and as the weed is digested, it releases methane which can be harvested.

"At the moment, we're going through a whole lot of digester-type trials to find out which one has the best effect," Mr Carter said.

The project has three main components: developing "reasonably fast" digester technology, cost-effective collection methods to harvest the weed working alongside iwi groups and then refining and using the two byproducts.

The methane released during the digestion process could be harvested and used for heating purposes, or even used in a generator to produce electricity.

Mr Carter is essentially trying to speed-up the anaerobic digestion process, and the methane produced is one of the byproducts from the procedure, the other being a slurry which can be used for fertiliser.

Mr Carter said as far as he was aware, his project was the only one of its kind which involved converting aquatic weed into a potential energy source.

He faces a few "limiting factors" in the development of his project, including a bacteria which "eats" methane, alkaloids in the plant which inhibit anaerobic digestion.

He has to establish whether he can work around those issues.

The next stage of his project will be a continuously working digester.

In the long-term, Mr Carter's project could lead to sustainable energy production, and it's feasible it could lead to enough energy generation to power a small community.

"The TTP funding aims to utilise technology that makes use of Maori principles, so it's important this project is a two-way process.

"I've worked with Maori previously on iwi-based waste management projects, and Maori views are way ahead in terms of the environment. And while anaerobic digestion is still a fringe technology, it is becoming more mainstream."

His project could lead to a business venture for his firm, Interface Chemistry, when he completes his study.

Surprisingly, Mr Carter "hated chemistry at school", but his current PhD study is his fourth burst of tertiary education, and he expects to complete his PhD in about two years.

He also offers consultancy advice on waste and energy management and efficiency, and says the "ideal" PhD project resulted from previous work with American firm Ocean Earth.

- © Fairfax NZ News