Lots on biochar toward the end of this report. Also links here to the NZBRC report produced for MDC.
“The Marlborough District Council has also been busy looking at options and in 2018 initiated a $170,282 research project predominantly funded through a Waste Minimisation Fund grant. The goal of the project was to look at options to turn grape marc into a stable, reusable and marketable product.
Massey University scientists, Professor Jim Jones and Associate Professor Sarah McLaren, were involved in the project and investigated the technical, economic and environmental impact, especially the carbon footprint, of different options of repurposing marc.
Finding a solution which minimises risk was one of the priorities.The land-spreading at Indevin represented a potential liability which they list in their report as “BOD [biological oxygen demand] of soil, forming methane, nitrous oxide and leaching into waterways.”
The estimation of how much marc equates to the 200kg of nitrogen per hectare of nitrogen arrived at by Jones and MaClaren was 42.6 tonnes per hectare, not 90 tonnes.
“It looks to us like an increased risk profile. It’s not to say something will go wrong. Nobody is doing anything illegal,” Jones says.
Jones’, whose speciality is burning things, says drying grape marc, instead of composting it, creates a start point for a number of different options.
It could be turned into pellets to feed to animals, or potentially be used as a fuel, or spread out on land throughout the year, not directly after harvest, or be used to make electricity.
He has another trick up his sleeve.
“You can then make biochar out of it,” he says, explaining biochar is essentially charcoal, but instead of burning it, it’s buried.
“The driver for making biochar is that when you’ve made the biochar, the carbon that was in the plant material turns from a form that rot to a form that will not rot. It will stay there for well over a hundred years, even thousands of years.”
If the marc had been left to rot and breakdown through land spreading, the carbon would be lost. This method locks the carbon up.
Mclaren, who specialises in what’s called life cycle analysis, where she looks at emissions from all parts of a supply chain, says using grape marc to lock up carbon has potential to support aspirations to become carbon zero, “in a not insignificant way”.
There’s a couple of fish hooks in this idea. At present biochar is not recognised as a carbon sink in the New Zealand Emissions Trading Scheme, says MaClaren. Secondly, setting up a plant to complete this process comes at a cost.
Jones thinks passing the cost of setting up a plant on to the end consumer would work out to a few cents a bottle, something he thinks people would be willing to do for a ‘green label’ sustainable product.
He estimates wineries might be paying somewhere between $10 and $30 per tonne of grape marc to have it spread at the Indevin property.
He’s worked out a cost per tonne of grape marc for a number of options. Composting works out at $16 to $22 per tonne. Making it vanish each harvest by turning it into electricity would cost around $42 per tonne of grape marc. “It’s more expensive, but they’ve sent it to the electricity generator – it’s gone.”
Turning it into biochar to be buried costs even more – coming out at $50 to $52 per tonne. It’s cheaper than landfill, which he says would be around $90 per tonne.”
