Opinion: The New Zealand wine industry has been a great success story, creating world-renowned wines with continued export demand, but it’s an industry that produces a lot of waste, and faces challenges getting rid of it. This includes the left-over grape skins and seeds – the grape marc – now treated largely as a waste stream, but which is a significant resource that could be directed towards novel high-value products.

New Zealand produces over 50,000 tonnes of grape marc annually, and many New Zealand companies need to pay for their grape marc to be disposed of. Some of it is spread directly onto land, which is an inadequate solution as soils can be overloaded because of high biological oxygen demand, while leaching of the raw grape marc can pollute underground water systems. Large composting operations have been established, but face challenges in relation to leachate and runoff into waterways and associated compliance issues.

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Overseas, and in some local New Zealand cases, grape marc is being processed to produce products with food and nutritional applications, such as grape seed oil or extracts containing polyphenols – compounds found widely in fruits and herbs, and with known antioxidant properties.

Recovery of the wine acids is also an established commercial process overseas, to make tartaric acid that can be added to wines with insufficient acidity. It is also possible to ferment the grape marc and obtain an appealing piquette – a lower alcohol wine – although this leaves behind a “depleted” grape marc that still needs to be disposed of.  

We believe the time is ripe to rethink the use of grape marc and establish a novel integrated grape marc bio-refinery concept in New Zealand. Starting in October, our team from Scion, Auckland University of Technology, the University of Canterbury and the University of Auckland’s Centre for Green Chemical Science, will work closely with industry partners and overseas collaborators on a five-year programme, “Waste to treasure: using novel chemistry to valorise residual plant materials”.

We will stay in close contact with the wine industry, supported by the Bragato Research Institute, and take a stakeholder (industry, consumers, community) co-creation approach in the design of novel products with applications in the food, pharmaceutical, building, and fine chemicals sectors.

The New Zealand food industry will use grape proteins and bioactive polyphenols as plant-based dietary ingredients. The antioxidant polyphenols will also be combined with further biopolymers sourced from agricultural waste, such as gelatin from seafood or animal sources, to create smart food packaging that can extend shelf-life. We will also create value out of fine chemical and surfactants (the main component of cleaning detergents) based on grape marc components. 

We also aim to use grape marc to produce novel high-value paper products with fire-retardant and antimicrobial properties and integrated paper-based electronics. In the initial stages we will provide lab demonstrations, improving the sustainability of establish extraction steps, followed by pilot-scale tests to give an indication of process issues and scalability.

We will be doing this at the university’s Goldwater Wine Science centre on Waiheke Island, which has already provided specially processed grape marc for preliminary research projects on grape marc in the past and is an ideal location to test out different processing steps and extraction procedures at a pilot-scale.

Our researchers have successfully undertaken projects on grape marc and related industry waste-streams in the past. We believe New Zealand is in need of greater leadership in the creation of high-value product revenue streams while eliminating primary industry waste.

This approach could then be applied to other local horticultural industries in the future. We will continue to evaluate techno-economic and lifecycle analysis considerations for the processes we will develop, and for our overall biorefinery concept.

The calls from New Zealanders for a circular economy are growing, and we aim to showcase how we can use science to add commercial value to the waste of an industry that exported $2.3 billion worth of wine in 2023, while limiting how much of it is sent to landfill. 

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