Pumice Pathways

A five-year research programme (begun in October 2023) around the use of pumice in concrete and its potential for reducing carbon emissions, is being led by Te Kunenga ki Pūrehuroa Massey University, Market Economics and Te Arawa - alongside Waipapa Taumata Rau Auckland University’s engineering department. A unique component of the kaupapa has been the application of a tikanga Māori approach over the entire project.

Pumice (or pungapunga) is a porous, lightweight material, abundant in Aotearoa and produced by explosive volcanic eruptions. It has unique properties that have made it a desired, widely traded natural resource since human prehistory. Its versatile use is recorded in archaeological artefacts worldwide, including Aotearoa, where Māori used pumice for tools, ornaments and spiritual items, such as fishing net floaters, abraders, tattoo ink bowls, ember carriers and spinning tops.

It has also been important for construction since ancient Rome, when ‘Roman concrete’ was first used. Concrete is the foundation of modern civilisation and at present is the most consumed man-made material in the world, with over 10 billion tons produced annually. It consists mainly of water, aggregate and cement, the latter being responsible for 8% of global CO₂ emissions. Replacing some of the cement with pumice could significantly reduce the carbon footprint of this essential material, a practice that has successfully been implemented overseas in the past decade.

Presently in Aotearoa New Zealand there are relatively few uses and applications for pumice, even though the Taupo Volcanic Zone in the North Island of New Zealand has been one of the most active volcanic zones on earth in the last 10,000 years. Here, a minimum of 34 large-scale, caldera-forming explosive eruptions in the last 1.6 million years have covered the landscape in several thousand meters of volcanic material, providing extensive and valuable (but underutilised) resources that could help solve some pressing socio-economic, supply-chain and climate-change mitigation issues.

The programme, while hosted by Te Kunenga ki Pūrehuroa Massey University, was co-designed and is co-led with tangata whenua of the “pumice lands”, Te Arawa and Tūwharetoa iwi, in alignment with iwi aspirations and hapū/whānau intergenerational goals and values. The programme is  exploring pumice resources within the rohe, while drawing on Te Arawa aspirations and economic modelling to identify pathways for a Māori-led pungapunga/pumice economy to maximise benefits, while minimising risks. It includes developing resource gathering tikanga (protocols) and post-extraction land restoration options promoting kaitiakitanga.

Wally Tangohau is general manager of Te Pumautanga o Te Arawa Trust. He works alongside Clark Pirika, chair of the Trust and is part of the project advisory group. Wally explains the project was begun following a meeting in Rotorua pre-COVID that led to the five-year-long research programme.

The three key goals of the programme are; to support iwi aspirations by developing a new industry, as well as grow involvement and leadership in that industry. In addition, if developed in certain forestry areas, that are currently managed by Māori Trusts, to create further value in those areas by providing alternative land use options. At the same time, and for the benefit of all New Zealand, to develop a local product that will reduce the carbon footprint of concrete used in this country’s infrastructure projects.

Dr Anke Zernack is a senior research officer at Te Kunenga ki Pūrehuroa Massey University’s School of Agriculture and Environment, and an authority on volcanic activity. She says, ‘There were about 10 years of relationship building between ourselves and Te Arawa, exploring options guided by  Vision Matauranga. We looked at which assets Te Arawa have that could be developed through collaborative research, and how we could progress Te Arawa's aspirations in research and development.’

Through a Vision Matauranga Capability Fund project (undertaken with Wally Tangohau, looking at uses for pumice in horticulture) Dr Zernack says it became clear that there was much more that could be done with pumice in addition to horticulture and hydroponics, because it is used worldwide for other things, especially in construction. ‘So we got together and discussed what would be desirable for Te Arawa. That took a couple of years with a diverse team with people from the Massey Volcano group, market economics, and Auckland University bring the engineering aspect - under the umbrella of and guidance from Te Arawa.’

Dr Zernack explains Massey University’s area of research is looking at the volcanic material - where we find it, what its characteristics are, and how much there is in each of these areas. And working closely with engineers from the University of Auckland, we are also developing recipes and processes for new concretes that can be produced from the resources available and are optimised for low-carbon and performance properties.

Economic and business models coming from this work are also being looked at especially by Market Economics, to determine how Te Arawa can become leaders in this area, led by a Te Ao Māori worldview, while minimising risk. Tangohau says this Te Ao Māori approach is another layer, ‘where everything we do has to have a tikanga (correct practice) component. We've got a number of our young engineers, who are based in Auckland, and they're either working towards their PhD or lecturing at Auckland University. They’re also very connected to their Te Arawa roots as well. They're already aware of the two worlds - and being able to combine the two worlds in this research project makes the journey a little bit easier.’

Another part of the Trust’s work is in recognising and utilising our already connected relationships with landowners within the rohe. ‘So it's not just about the extraction, it's also about the remediation aspect of it as well. And so, having Te Arawa landowners being an integral part in shaping what that actually looks like, is key.’

Dr Zernack adds there is an advisory group comprising several iwi representatives. And the young Te Arawa Whakapapa engineers with their combined academic and cultural backgrounds, are working out the principles needed to operate under. They include; how the resource should be addressed, what tikanga should be applied to process and extract it - while also keeping in contact with hapu and whanau through Wally, Clark, and the other advisory group members.

Dr Zernack says they have looked at the volcanic deposits previously from a natural hazards perspective, so there is information available on which eruption produced a particular kind of material, but not from a resource perspective. Now, grain size, chemistry, and other material properties that engineers need to know to decide if it can be used for concrete, are being studied.

In addition, the two main volcanic centres located around Rotorua and Taupo produce different types of pumice in different volumes. So distribution and volume, especially on Māori-owned land governed by Māori Land Trusts is also being investigated. Anke explains as some locations are quite big forestry areas, they are likely to be the target areas in the first instance, where it would be relatively easy to incorporate pumice extraction into cycles of tree harvesting.

‘At the same time we are looking at how we can ensure the land is not devalued, and how it can benefit the people of the land, potentially using this local resource for buildings and other things.’

‘We are also looking at the soils in between different eruptive deposits. If you imagine the landscape now, you've got soil on top. If an eruption happened, that soil would be buried and you then form a new land surface. And because we've got 25 eruptions over time, say from the Taupo volcano - we've got different types of paleo or buried soils, that have had a lot more time to form between eruptions. A lot of these buried soils are actually more mature and potentially better than the young, immature soils that we have on top. So we'll be looking into those different soils to discover what their properties are also in the next couple of years.’

‘We’ll be asking, when we bring them to the surface, what happens? How does it change the soil? And can it actually provide an opportunity for land use change? Could this, once we've taken the pumice out and the new surfaces up, provide an opportunity for moving away from forestry in certain areas to pasture or horticulture?’

‘We've got a good idea of what we've got in terms of resources and we've also identified some key areas. So we're trying to bring in the land owners now and are running Wananga where we're inviting various land trusts to bring them along and show them the opportunities there.’

‘We're also working with industries to see how that can be brought into the standards and into the industry to make sure that what we're finding can actually be implemented. And the engineers are still busy testing the various samples that we've given them. So we have a rough understanding of which resources might be the best, but we're still waiting for the testing to actually come through.’

‘We're looking at 20 different types of material. And if you understand the key material properties that influence their use, then we can apply that to all of our resources. Because, as volcanologists, we know what the material is like in different areas. So once the engineers tell us, this type of material is the best for an application, then we can apply it. Now that we're halfway through the work, we’re also starting to look at the big picture and the potential business plan.’

Clark Pirika notes, ‘I think the great thing here is we've been a part of this journey right from the outset. And being able to tell that story to our wider iwi, hapu, and landowners adds some weight in terms of what our aspirations are’.

The ambitions for this programme will not only support the transition to a low-carbon economy for Aotearoa-NZ and support local communities but also re-connect iwi, hapū and whānau with mātauranga of the historic pumice economy, and empower Te Arawa and Tūwharetoa to make land-use and investment decisions that will revitalise and reframe our economy.

As Clark puts it, ‘Our bottom line is to grow our garden so that we can share the spoils of the kai that's being harvested. So, that's how I see this. We're putting seeds in the garden, we're growing veggies, and then those spoils are being shared out.’ 

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