22 Apr 2021

The environmental hangover from NZ's winemaking

3:47 pm on 22 April 2021

Marlborough's wine industry is booming, but there's no industrial-sized solution to deal with its waste.

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Photo: Getty Images/RNZ

Sewage fungus is not what the wine industry wants people to think of when they sip a sauvignon blanc.

It was also something I wanted to avoid.

But like Marlborough's wine industry, I had a problem on my hands. I had more grape marc than what I knew what to do with.

Grape marc - or pomace - is the soggy leftover product of wine making. It's the skins, seeds and stalks of the grapes after most of the juice has been squished out of them. Roughly 20 percent of each harvested tonne of grapes end up as grape marc.

Depending on what's done with it, grape marc can be a resource, or a liability. If you leave it sitting in a pile, a little juice will leach out. If it's uncovered and rain gets on it, even more will leach out. It's this leftover liquid, slowly leaking out of stockpiled, rotting marc which can damage the environment. If it enters waterways, it can cause sewage fungus.

For Marlborough, where a 50,000 to 70,000 tonne tsunami of grape marc builds from March to the end of April each year, it's been a cause for court cases and academic research.

My own grape marc pile was just 10kg and had been collected to better understand exactly what Marlborough deals with each year.

Getting hold of it took some wrangling and felt a little like a drug deal. Emails to wineries went unanswered so I tapped my personal network. Eventually it paid off. "Hi Farah, my contact says he will have some marc next week," said a text message. What day should I plan to visit the winery to get it? "I'll let you know," was the terse response.

In the end the grape marc came to me and I never met the contact. Pressed on a Friday from sauvignon blanc grapes on Waiheke island, it was loaded into a black plastic rubbish bag, then stuffed into a suitcase with wheels. It sailed to Auckland on the ferry and was wheeled to the deck of a Ponsonby villa. There it sat in the suitcase overnight before being transported to my house.

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Photo: RNZ/Farah Hancock

I had read plenty of horror stories about what happens when grape marc storage goes wrong. What was in the suitcase was nothing like what I had expected.

For starters, it wasn't wet. I had anticipated sloshing but instead it was more like clammy, leathery cornflakes. And although there were a few dead bugs among the flattened grape skins, it wasn't gross.

It smelt fruity and a little yeasty. "Are you making pizza dough?" a visitor asked, arriving while the marc was uncovered in my kitchen. They were right, the house smelt amazing, like I had been busy baking.

It was hard to believe something which smelled so good could lead to the stagnant-smelling sewage fungus Marlborough local Carl Wilkinson discovered in Puka Puka stream in 2016.

The stream was a favourite childhood swimming and fishing haunt but when he visited in 2016 there weren't any eels or freshwater crayfish and swimming was out of the question.

The water was covered with a rust brown layer of scum but what lay underneath was worse. "If you took that little, thin layer off the top of it, it was just jet black - jet black jelly."

The jelly Wilkinson found was an ankle deep mat of sewage fungus. "To put your hands in it, is just like jelly running through your fingers," he says.

Testing concluded the cause of the black jelly was most likely seeping leachate from a pile of grape marc dumped near the stream.

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Photo: Marlborough Express

Wilkinson's discovery wasn't the only grisly grape marc incident in Marlborough between 2016 and 2018.

Neighbours of Babich winery noticed a smell of rotting eggs and foul tasting drinking water. Their water was poisoned by a different pile of grape marc from a different winery. Testing revealed unsafe levels of manganese and iron in two water bores, as well as arsenic in a third. What had leached into these bores had arsenic 20 times higher than drinking water standards.

Then more black fungus popped up in another stream, along with grey clouds of liquid which burnt grass on the stream banks. The biological oxygen demand per cubic metre, a measurement of organic waste polluting the stream, was at levels higher than raw sewage. It wasn't sewage polluting the stream though, it was yet another pile of grape marc, this time linked to Yealands winery leaching pollutants through the soil and into waterways..

Since 2016, grape marc incidents in Marlborough have led to 11 defendants facing a total of 59 charges - and with prosecutions came publicity. In court, David Babich shared how he faced questions at a European trade show about "polluted vineyards in Marlborough".

There was the risk of the media attention shifting from methane-belching cows to grapes and a Ministry for Primary Industries report warned as much, saying: "recent media attention on farming environmental practices may well move its spotlight more on to viticulture".

It was clear, the industry needed an industrial-sized solution, fast.


I had a similar issue. My own marc starred in a lengthy photoshoot but then I was faced with the dilemma of how to get rid of it without upsetting my neighbours.

By day four its smell had become a little sharper. "It smells like cask wine," said one person. Another thought it smelt like church. A third said it reminded them of cleaning up the morning after a party.

I knew some of the basics about dealing with grape marc. Lessons from The Gremlins movie applied. Getting it wet was a no-no. The liquid which leaches out of stockpiled marc is like kryptonite, I had been told. It would lay waste to plants and soil. Rain on the pile would just multiply the leachate. The last thing I wanted to be responsible for was sewage fungus in the local stream.

There were also lessons from abroad. Had I owned a still, I could have tried my hand at distilling it, like the Italians, Australians and French do with almost all of their grape marc. With a bit of care I could make grappa, a colourless, strong liquor drunk in Italy, or industrial alcohol. In Spain about half of the marc is distilled into alcohol and the other half is spread on land as a soil conditioner. In California, just over half is composted and seeds are used to make grapeseed oil.

Or, I could follow Greece's low-effort approach and throw it in the bin; over half of their grape marc goes straight to landfill.

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Raupara Springs viticulturist Matt Fox. Photo: Supplied

Better advice came from Raupara Springs viticulturist Matt Fox. The marc could be added to a vegetable garden without first being composted, it just needed to be mixed with something.

"If you're able to put some sort of leafy material with it that will likely have higher nitrogen, that will help it break down faster without starving your soil of a nitrogen source."

So, lawn clippings?

"Yep, that will do it."

4kg of my 10kg pile were added to a modest vegetable plot, along with grass clippings.

Fox should know what to do with it. Raupara Springs has used grape marc at their Blind River Valley vineyard in Marlborough for a few years. Each harvest marc is spread between the rows of vines as quickly as possible after pressing, and as thickly as council rules allow.

It's all about soil health, he says. Better soil means healthier vines and more grapes. Spreading grape marc increased the organic carbon in the soil of one vineyard from around 3.8 percent to 5.4 percent.

In agricultural circles, that's considered a big lift, according to Fox. "Usually you wouldn't see that sort of gain in such a short period of time."

There were also improvements in the soil microbial content, which he says helps nutrient cycling and improves the ability of the soil to store water.

He'd like to see more in the industry utilise grape marc.

"For the longest time it was a waste product … We have quite easily, with some capital inputs, managed to turn around what was a problem into a massive beneficial tool for us."

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Composting grape marc at Raupara Springs. Photo: Supplied

Fox admits Raupara Springs has a few things on it's side. Not only does it own vineyards, it has its own winery and has trucks to move the marc from the winery back to the vines.

Marcus Pickens, the general manager of the local industry group, Wine Marlborough, explains companies which make wine sometimes don't have their own vineyard, or even much land of their own to spread marc on. They make wine from grapes grown by other vineyards.

"It's not as easy as just saying 'return to sender',' you sent me the grape, I'll send you the marc'."

Most vineyards don't want to spread grapes grown at other vineyards on their property. Pickens thinks this is fair. "They know exactly what they've done on their vineyard, they don't know what their neighbour's done."

Trying to keep grape marc separate at the winery to return to sender would be an "infrastructure and logistical nightmare," he says.

This leaves problematic piles of marc sitting around, with the potential to leach pollutants and poison people's drinking water and the environment.

The prosecutions of 2016 came as a jolt. Pickens says the industry had been talking about the problem prior to the spate of court cases, but these "triggered us to look closely at how we change behaviour".

A flurry of solutions were touted. Compost, stock food, fuel, hand sanitiser and grape seed oil have all been mentioned. Distillation into grappa or industrial alcohol is not really an option here according to Pickens. New Zealanders just don't drink grappa, and Fonterra already produces industrial alcohol as part of its milk processing.

The challenges for any solution is the ability to cope with a raw material which arrives all at once, the need for a solution which doesn't require it to be transported long distances, and the amount of money it would take to set up a facility big enough to cope.

Pickens isn't convinced consumers would pay a premium price to know the marc had been dealt with sustainably.

It would be "quite a stretch" he says, to think the average wine drinker knows "there's even such a thing as grape marc".

His preferred solution would be for it to be spread under vines: "Nothing more simple than returning what you've taken from the land - returning it back to the land."

For my own pile of marc his advice is similarly low-tech. "The easiest option would be just to use the leftover marc as a mulch around some trees in your garden or roses/shrubs etc. You could also just dig it into your vege garden or compost it."

Two weeks in, my marc's smell had changed again. "Currant cake," one person thought, another thought it smelt like a boozy Christmas cake, a well-travelled third person thought it smelt like the markets in Prague at Christmas time.

The shrubs in the garden received an early Christmas present. My pile of marc was reduced by another 4kg. I still had 2kg to deal with and no way to return to sender.

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Grape marc arriving at Indevin's Bankhouse Estate Photo: Marlborough District Council website

For people with big piles of marc and no land to spread it on, one large-scale solution has emerged. Indevin's Bankhouse Estate received permission from Marlborough District Council to spread fresh grape marc over crop land at a rate of up to 90 tonnes per hectare. Initially it was reported this was a transitional activity undertaken in 2019, to give the industry "breathing space" until a pilot plant that would turn it into fertiliser could be built.

This year's harvest will be the third year marc has been spread at the estate.

"It's a great solution," says Pickens. "Whether it's a solution for the next 10 years, we don't know. I'm sure there's a lot of science going on to establish that."

One thing which raised eyebrows was the amount of grape marc permitted to be spread on the land. Guidelines the Marlborough District Council commissioned AgResearch to write in 2012 recommend a maximum of 3 tonnes of grape marc per hectare. It's the same amount Italy allows to be spread.

How three tonnes a hectare grew to 90 tonnes relates to nitrogen according to the council: "...the application rate of 90 tonnes/ha/year of grape marc proposed results in nitrogen loading of 200kg/ha/year," says a spokesperson for Marlborough District Council's compliance team.

Lincoln University's Dr Jim Gibbs was told about land spreading consented at Indevin by an industry figure who was in shock at the amount allowed to be spread.

The amount allowed prompted him to question the council about their decision.

Correspondence obtained under the Official Information Act shows the council acknowledged the nitrogen loading was higher than its own rules allow, but say this was done based on information it received from a soil consultant engaged by Indevin.The consultant suggested because grape marc breaks down slowly, the amount of nitrogen available to plants slowly ekes out. It says this 'available' nitrogen is different to the 'total' nitrogen.

Gibbs is skeptical of this approach, saying he's heard it's not an argument which would be accepted by other councils.

He also expressed concern that the grape marc was allowed to be stored on bare ground, or on ground with a layer of lime after delivery, instead of on a surface like concrete, or plastic which would contain leachate. Even in dry weather at least one truck has been stuck in the marc and had to be towed out.

Gibbs says he's worked with grape marc for some time, looking at its potential as a stock feed and worries the council didn't understand how wet grape marc can be when they approved the consent. In his work he found grape marc often included washdown water from cleaning out vats and can be up to 80 percent liquid.

"In some cases it's closer to a soup than a feed."

The high sugar content of white grapes can cause biological oxygen demand.

"If you watch where these sort of streams and leachate come out, then they act like the herbicide Roundup. They kill all the plant life underneath them."

The Marlborough District Council told RNZ no concrete pad is needed as the grape marc is spread within 48 hours of arriving at the property, and leachate doesn't form within this timeframe.

Gibbs disagrees with the council's view that leachate does not occur until 48 hours has passed.

"The fact is that there's a lot of sugar all around this material, there's a lot of sugar from the very process of squeezing it all out, that's around every surface area of this material. And then the process routinely adds a lot of water, which puts that sugar into solution. So that original material that runs off it is leachate under anybody's definition of that it's a leachate."

He thinks Indevin, the company spreading it, has good intentions and is trying to solve an industry-wide problem but says: "What is most important to me is that councils have a duty of care, they have a duty of care to make sure that what's put in front of them is done very carefully."

He says the council had previously taken a hard-line approach to how much marc can be spread.

"My feeling is that this was a knee jerk reaction to the fact that the council recognised that it would put a lot of pressure on wineries and stop them from doing what they were doing before, but there was no plan b."

The Marlborough District Council says soil monitoring is part of the conditions of the consent and results haven't raised any issues of concern other than elevated levels of potassium in 2019 which improved by 2020. Based on this it sees no reason to review the amount of marc allowed to be spread.

Indevin's group operation's manager Deane Caughey says to date, only about half of the permitted 90 tonnes per hectare has been spread on the property. Two crops per year are grown on the soil where the marc is spread and soil samples are taken before and after marc dumping.

"All of those soil samples have validated the model is actually working and that it is a beneficial process."

The company is also running trials looking at other options such as anaerobic digesters, and stock food. Caughey says these would be medium to long-term solutions and would require investment.

Gibbs sees other options which could be a win-win for Marlborough, like turning the grape marc into a silage-like stock feed which can even reduce animal methane emissions.

"They like the smell of it, they love the taste of it, and it's a very safe feed."

To make this work would require investment. Fresh marc would need an impermeable surface to be stored on, as well as a rubber-lined dam to hold the leachate which drains off.

The leachate can be diluted with water and used for irrigation in summer, and the grape marc can be ensiled - turned into silage. Once it's silage it can be stored safely for some time until it's fed out.

"It's one primary industry feeding another one, and producing a clean, green material."

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.

What should someone like me - without the means of burning marc oxygen-free at 500 degrees celsius to make biochar - do with 2kg of unwanted grape marc?

"We put ours in the freezer," says Jones with a laugh.

The prospect of a permanent tupperware of marc living in my freezer, already crammed with mystery leftovers, doesn't appeal. It was staying outdoors in a sealed bucket.

By this point the smell of my grape marc has evolved. Opening the bucket lid briefly releases an intense smell, similar to nail polish.

For the climate's sake McLaren warns against ignoring it. "Just don't leave it in a pile, or compress it where it goes anaerobic and produces methane." She advises daily marc fluffing: "You'll need to go out every morning and turn it."

It's sage advice. Come 2023 and there will be a methane spotting satellite run from New Zealand. Methane doesn't hang around long in the atmosphere, but does heat it up while it's around.

The satellite won't be able to zero in on my modest backyard bucket of marc or a cow burp from space, but it will have no problem spotting large piles of marc emitting methane.

My attempt to see if my marc was producing methane, with a lighter gingerly held over the open bucket, might have horrified health and safety experts and not be terribly robust science, but didn't result in any blue flare of flame, or loss of eyebrows. Fluffing my marc, was added to my daily routine.

When asked what's next for Marlborough's grape marc, Jones explains moving beyond the research stage hasn't been plain sailing. Their research report came out amidst the 2020 Covid-19 lockdowns, when vineyards and wineries had to scramble to safely get the harvest in during a pandemic.

There was an effort to set up a working group. "Which has been difficult because the wine industry is a competitive industry and in Marlborough dominated by foreign owned companies." Creating a solution at scale would require collective action "so that's been a bit of a sticking point", Jones says.

He says there's a project involving Lincoln University and AgResearch studying biochar for agricultural and forestry sectors and there's interest from the wine industry to join that project. There's also an initiative underway to get biochar included in the Emissions Trading Scheme as eligible for carbon credits.

His view is there's a chance for New Zealand to gain a competitive advantage.

"If you can do something that involves a number of processing steps, you've actually got the opportunity to take side streams off that."

He reeled off a list which included tartaric acid, polyphenols, tannins, grape seed oil and activated carbon which can be used to absorb pollutants.

"You've got to start with something and I think addressing the environmental side of it and having a real win with biochar is the first place to start."

Marlborough District Council's solid waste manager Alec McNeil thinks the starting point for the industry is to assure itself land spreading, which has become "sort of standard practice" is sustainable, "if that's the case, then they might not be required to do anything," he says.

If it's not sustainable, then he thinks a next stage would be a trial plant to create biochar, followed by commercialisation.

"It's just how the market can set itself up to present the best attractive proposal to the industry."

The worst possible situation - and one he thinks is unlikely - is for all avenues for it to disappear. This would mean land spreading would be unavailable and there was no demand for stock food, or compost.

"The worst case scenario would be putting it back to landfill."

I still had 2kg of marc to deal with and my vegetable garden was at grape marc breaking point. I didn't want to put it into the bin where it would make its way to landfill. I canvassed friends and family for creative solutions.

Art was one suggestion: "Set it in resin as an ode to the importance of product stewardship."

Burning was another. "Can you incorporate it into candles? Imagine the scent of beeswax and grapes at dinner."

"Waste disposal, a bit at a time" was a third no-nonsense idea to deal with the leathery skins.

But it was the final suggestion that solved my problem.

"Keep it Kiwi," they said. "Plant some feijoas. Use the grape marc as mulch."

After a trip to the garden centre and a bit of sweat, the bucket was finally emptied.