TerraNova has the glass recycling contract for Christchurch, along with many other recyclable materials, which farmers often put to quite innovate uses. In horticulture reflective materials are used under fruit trees and grape vines to provide more of the energy from the sun’s rays to the developing fruit, lifting the flavours and possibly ripening the fruit earlier.

TerraNova is a charitable trust which is charged with finding innovative ways of using waste materials. Sarah Gordon, resource analyst from TerraNova, thought of the possibility of using crushed glass under the grape vines and mentioned that to her CEO, Richard Lloyd, who has an interest in grape growing and wine making. He asked Sandihurst Wines if the idea was practical and they contacted Glen Creasy, of the Lincoln University Food and Wine Group.

Glen has been using crushed mussel shells in reflective trials in the Marlborough/Nelson region for a couple of years, proving the viticultural benefits of the mulch, through light reflection, weed suppression and soil conditioning. Mussel shells are a waste product which need disposal because of the huge volumes generated by the mussel industry in Marlborough.

Glen has set up a trial of the crushed glass at Sandihurst, using about 200m of pinot noir grape row. The glass was spread to a depth of 5cm just before Christmas and the grapes will be harvested mid-April. Wine will be made in batches from vines with the glass reflective and those without, to compare. It will take two years to establish the viticultural benefits of the glass as a reflective mulch. Glen expects it to change the flavour and possibly advance the ripening. But weed suppression may not be as good as mussel shells. It will help with soil moisture retention.

The crushed glass is a completely safe and inert, sugar or sand-consistency material, without sharp corners, and it is too heavy to blow away. It may remain as a mulch for many years, without dispersing or being incorporated in to the soil. It is believed to be a world first for the use of crushed glass in this way.

Sandihurst owners Hennie and Celia Bosman are committed to sustainable vineyard practices and they see the use of crushed glass taking some responsibility for the waste glass produced in New Zealand every year. They also hope to utilise TerraNova’s product in other applications such as landscaping and in the flooring and wall panels of their new tasting shop.

The biggest cost is the crushing, carting and spreading of the glass. TerraNova thinks it may be possible to take a glass crushing plant to the vineyards and ask patrons to return their wine bottles, to be crushed and recycled as a reflective mulch.

TerraNova has made an application to Enterprise New Zealand for funding of a masters student to carry out the trial work and some equipment for environmental monitoring in the vineyard. Lincoln University’s role is to develop credible, scientific trials to compare wines produced from rows of grapes subject to the glass-enhanced ripening and rows that have not been treated with the crushed glass. The performance of the crushed glass mulch will also be measured against that of crushed mussel shells.

The Sandihurst trial complements other research being run by Glen on the modification of vineyard microclimates and wine quality, such as at Neudorf Vineyards, Upper Moutere, where the Sustainable Farming Fund and New Zealand Winegrowers have supported the research into the use of crushed mussel shells.

Evaluation of the effectiveness of mussel shells has been underway since 2001 and has produced some promising preliminary results.

Glen said that the general idea of enhancing the availability of understorey light has been explored internationally using a number of means, for example shiny aluminium, but cost and practicality of application have frequently been issues. The recycled glass option had price as well as ease-of-use advantages, he said.

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