Beyond landfills: New Zealand’s march towards a circular economy

Landfills (and incinerators in other countries) suck up waste together with recoverable recyclables and valuable resources. When resources are abundant and inexpensive, and the impact on the environment is not a prevailing concern, the current waste disposal method (landfilling) which is based on the linear economy (take-make-dispose), can be very successful.

However, we’re rapidly approaching a point where the linear model is no longer viable because the availability of many non-renewable resources can’t keep up with demand. We’ll demand three planets’ worth of resources every year by 2050! We must create a more sustainable and equitable economy by minimising waste, promoting resource efficiency, diverting resources from landfills, and creating new economic opportunities.

So, what is a circular economy?

A circular economy is more like a life cycle; when the item starts to become irrelevant or broken it is reused, recycled, repurposed, recovered, remanufactured, or composted. Instead of being discarded, the item begins the cycle again as a new object.

A circular economy lowers greenhouse gasses, decreases our reliance on fossil fuels, lessens resource extraction, reduces our reliance on landfills, and cuts the amount of waste we send to landfills. It also invites you to look at the objects in your life differently. Do I really need this? Do I really have to throw this into the rubbish? Can it be repurposed or recycled?

The Faculty of Engineering has many academics and students who are working with industries creatively trying to find circular solutions to linear problems. They are discovering opportunities in rubbish and uncovering untapped resources.

How engineers are turning waste into value

One of the ways is from the dairy industry, using methane extraction to turn it into biogas which can then be harnessed to produce energy. Cow effluent releases one of largest amounts of methane in New Zealand dairy farms, which means it is one of our greatest untapped resources.

Yvonne Nleya is a PhD candidate and is determining how to extract methane from cow effluent and convert it into biogas as a way of reducing on-farm greenhouse gaseous emissions. Biogas is a renewable fuel that can be extracted from organic materials, like animal waste, through a process called anaerobic digestion. Biogas can then be harnessed to produce energy.

Currently cow effluent is disposed of in one of two ways: the two-pond system or land application. The two-pond system, aka the oxidation pond treatment system, uses anaerobic (without oxygen) and aerobic (with oxygen) digestion to decontaminate the waste. While this process was initially thought to be a positive alternative to the land application system studies show it still releases methane during the anaerobic process which contributes to greenhouse gasses.

In the land application process, the manure is left where it is expelled or is shovelled into a muck pile. This releases methane gas, and can also contaminate nearby freshwater, and lead to nitrate leaching. Yvonne’s work would harness that methane and convert it into biogas energy. That biogas could in turn be used to heat and power houses and farms. Eventually, with the right resources, farmers could use this energy to power their neighbours’ properties as well.

Yvonne’s supervisors include two academics from the Faculty of Engineering, Saeid Baroutian & Brent Young, and an industry supervisor from Gavins Ltd, an agricultural company with an interest in farming research and development.

There are many other industries that dispose of resources that have the potential to be reused.

Kerry Jack Robertson is trying to create a circular economy within the medicinal cannabis industry. In New Zealand, the use of cannabis as a recreational drug is prohibited. Proper treatment and disposal of cannabis plants grown legally for medicinal purposes is mandated by law, as they still have small amounts of cannabinoids in them after processing.

Jack is spending his PhD, partnered with Greenlab, to understand the issues surrounding cannabis waste and researching how hydrothermal processing of cannabis waste can destroy residual cannabinoids to create bioenergy or biofertiliser.

Hydrothermal processes are water-based processing treatments. Organic material is combined with water while enduring high temperatures and immense pressure and transformed into bioenergy, like biogas, bio-oil and biochar, or fertiliser. Jack believes that through hydrothermal processing, we can upscale cannabis waste and “turn it into something useful.”

If the waste is used to create biogas, bio-oil or biochar, Greenlab could use it to power their facility or as fertiliser to improve our soil. As cannabis production increases so does the cannabis waste, but Jack is determined to make the cannabis industry a fully circular one.

Preserving metal

Circular economies can be developed with non-organic material in mind too. Having already completed an Engineering degree in France and a PhD in Materials Science and Engineering from the University of Southampton, Marie-Salome Duval-Chaneac felt there was more research to be done and that there was more of an environmental impact she could make.

She is now working on her second masters, a Masters of Sustainable Resource Recovery studying life-cycle assessments. Marie-Salome has a background in 3D metallic printing and recognised a sustainability problem within the field. She believes that continuously optimising a process is futile if the supply chain is not designed for sustainability.

Knowing there was a need to make supply chains more sustainable, she shared her idea with her supervisors, Saeid Baroutian and Xun Xu, who jumped at the chance to work with her. Marie-Salome, in collaboration with Phoenix Metalman Recycling, conducts exploratory research on waste minimisation and resource recovery for metallic and non-metallic alloys.

Her work on mineral resources like nickel and cobalt is crucial in the context of increasing demand for green technology and the transition away from fossil fuels. She seeks innovative solutions to enhance metal sustainability, prevent the loss of valuable minerals in metallic alloys, and promote their repurposing.

Being part of the circular economy needs taking the first step in making an impact. If you want to help support a circular economy and bring your everyday ideas into reality, the Faculty of Engineering is the place to start, backed by world-class facilities and state-of-the-art research centres that provide students with the tools they need to increase their knowledge and educate those around them.

These students are supported by many of the amazing leading academics at the University of Auckland. Students here have more than one supervisor. Most of these supervisors are within the Faculty of Engineering, but some students are doing transdisciplinary research with supervisors in two different faculties, like physics and science.

With the broad possibilities for making a true impact on sustainability and our environment, we need more people who are willing to be the next change makers for the future.

To find out which masters programme aligns with your interests and is the right fit for you, take our postgraduate Engineering quiz.