environment

Food scraps: The man turning our waste into natural gas

Auckland Council just announced kerbside food waste collections from 2021, taking up to 100,000 tonnes of scraps out of landfill. But where’s that rotting waste mountain going to go? Business editor Nikki Mandow tracked down the guy with the plan and asked him. Spoiler alert: It’s not compost, and it’s quite cool. Or hot. Warmish maybe.

It sounds corny, but Andrew Fisher is a man on a mission. Several missions. As a former NZ Army special air services officer, he has done stints in Afghanistan, Papua New Guinea, and East Timor.

And the week I meet him at his far-from-swish office/factory in the Auckland industrial suburb of Wiri, he’s off to give as much of his in-demand ‘O’ blood group blood as he can, following pressure on supplies after the volcanic eruption at Whakaari-White Island. 

But Fisher’s main job these days is trying to tackle the problem of food waste. And hopefully make money out of it. 

For the last 12 years his company, EcoStock Supplies, has taken up to 35,000 tonnes of waste food a year from supermarkets and manufacturers - bread, chips, vegetable scraps, breakfast cereals, pasta etc - and turned it into animal feed.

But there’s a whole lot you can’t put into animal feed. Meat, for example, or pizza boxes with that scraping of Hawaiian in the bottom.

So from next year, EcoStock will be heading into a whole new league - establishing in New Zealand a process which could in the end turn the hundreds of thousands of tonnes of food waste produced each year in this country into an alternative for natural gas.

Fisher is the driving force behind Ecogas, a joint venture company which has just started building a $10 million-plus “anaerobic digestion” plant in Reporoa, between Rotorua and Taupo. The other partner is renewable electricity and gas company Pioneer Energy.

Caption: The Ego Gas plant is modelled on a sister plant in Perth (pictured) and on similar digesters used for several years in Europe. Photo: Supplied

Imagine an enormous black compost bin with a dome and you’re on the right track. You put the food in, let the micro-organisms chomp on it for a while, and you get methane gas, CO2 and fertiliser.

The main difference between composting and the anaerobic digestion process is, as the name suggests, the presence or absence of oxygen.

Composting is aerobic = with air; anaerobic is the opposite. With the anaerobic digester, the biogas produced from the closed system rises into the dome and gets captured, piped out and used. 

How it works

“You have a big tank and you are continuously feeding it with what looks like a thick spirulina that’s made out of food waste. And then bugs much like the ones in human stomachs start converting it to energy,” Fisher says. 

“At set mealtimes, maybe up to 12 a day, you take the fertiliser from the bottom - it looks like weak tea - and you add the same weight of waste food. We cultivate our own bugs, like yogurt.

“Each lot of food waste takes 30-70 days to get through.”

Once completed, hopefully in 2020, Fisher’s Ecogas anaerobic digester will collect around 20,000 tonnes of organic food waste from manufacturers in the Rotorua/Taupo area (dairy factories, commercial bakeries, cool stores, milk sheds, fruit graders and the like), break it down using the natural micro-organisms in the food at 37-41 degrees, then collect the methane and CO2 and turn it into biogas, which can be used as an alternative for natural gas.

(Just in case you are as clueless as I am, methane is the main ingredient in natural gas). 

The really cunning part is that the Reporoa anaerobic digester is being built right next to Turners & Growers’ massive greenhouses, and will send its biogas straight across. 

T&G will use the gas to provide heat for the greenhouses at night and CO2 for the tomatoes, peppers and the like during the day. 

Which is apparently just what vegetables like best.

The biogas will replace the natural gas which T&G and many food producers and industry use at the moment.

Fisher hopes Reporoa will be the model for a swathe of anaerobic digesters to be built around the country to deal with food and other organic waste.

Including Auckland’s food waste.

As Regional Economic Development Minister Shane Jones said when he announced $7 million of Provincial Growth Fund loans for the Ecogas project: 

“Every year 327,000 tonnes of food waste goes to landfills in New Zealand, which could be turned into biogas energy to fuel an engine for electricity or heat, as well as help us achieve lower carbon emission targets.” 

The Auckland plan

The Auckland collection should see bins given to half the city’s households from October 2021 and the other half in 2022. 

A fleet of electric trucks will pick up the food waste and bring it back to a couple of depots in Auckland. Where, initially at least, the waste will head down to the anaerobic digester in Reporoa, Fisher says. 

“The council’s best case scenario is to collect 75,000 tonnes from Auckland households - 25,000 tonnes in the 12 months. 

“We have plenty of capacity at Reporoa to deal with that.”

But once tonnage from the Auckland collection reaches a certain trigger point, Ecogas wants to build a couple of anaerobic digestion facilities in Auckland. 

“We’ve identified sites, but we won’t start building until we’ve got community buy-in in terms of the collection.”

He says overseas experience suggests some communities really take food separation and collection on board. But some don’t.

“We hope Auckland shoots for the world best, not the worst, in terms of households using the bins. But the difference between the most engaged places overseas and the least engaged can be huge in terms of volume.”

Greenhouse gas

Fisher says the Reparoa plant will sequester 3,500 tonnes of carbon in the first year, building as volumes increase.

It can help methane emissions too. In Europe and the US, one of the main drivers for the increasing number of anaerobic digestion plants is greenhouse gas reduction - capturing the methane that would otherwise have come out of decomposing food in a landfill and gone straight into the atmosphere. 

The UN Food and Agriculture Organization estimates 30 percent of food is wasted globally across the supply chain, contributing 8 percent of total global greenhouse gas emissions. 

As The Washington Post writes: “If food waste were a country, it would come in third after the United States and China in terms of impact on global warming."

To be fair, methane from landfills is only part of that 8 percent figure - it also includes the production, transport, packaging and refrigeration emissions wasted when you throw your now-blackened bag of salad greens away uneaten.

In the UK, supermarket Waitrose announced recently it would be using compressed natural gas (CNG) made from biomethane to fuel 58 specially adapted trucks.  

The company has been using anaerobic digestion to deal with food waste from its stores since 2008.

And farmers in the US are putting anaerobic digesters on their farms, taking food and organic waste from local businesses, combining it with manure from their own cows, and using the gas to power their farm, and to sell into the grid. 

Fisher reckons Ecogas should be in a good position to expand its digester business once the first one’s up and running.

The company has been running a small-scale pilot for the last two years and is working with digester operators in Perth and the UK to hone the process for New Zealand conditions.

In five years’ time Fisher would like Ecogas to be operating five plants across the country. 

“Our growth will be driven by supply-side demand - big New Zealand manufacturers that need energy. We’ll be co-locating with large companies looking for long-term energy security."

Any excess gas could go into the national grid, he says. 

But keeping a digester working smoothly isn’t always easy.

Delicate digestion

Think: feeding a baby, Fisher says.

“You start on liquids, not solids. And you have to change your feed very gradually, maybe 1-2 percent a day. You can’t go from feeding it vegetables to curry overnight - it will start burping.

“When your baby rolls its eyes and changes colour, you know things aren’t right. Same with a digester, you have to get a feel for it.”

There are also plenty of external things that can go wrong, he says. 

“There are so many critical points and points of failure. Feedstock, collections, contaminations, public holidays.” 

Public holidays? 

If you don’t have enough food for your digester and it shuts down, it can take weeks to get it up to speed again, he says. 

That’s not good.

Not your average manufacturer

Meanwhile, the waste business model takes a bit of time to get your head around too. 

A normal manufacturer will buy stuff from suppliers, and turn it into products they sell to customers.

But with Fisher’s EcoStock business, most of the revenue is generated at the supply end - companies and councils paying him to take food waste away. 

His main competitors are not other animal-feed producers, but landfill operators, who fight, sometimes ruthlessly, for the waste contracts.

“I have to be the same price as landfills.”

And what if we all got on board and started reducing the amount of food waste we produce?

Fisher reckons New Zealand produces up to 120 million tonnes of food and food production-related waste a year, if you combine agricultural waste (including manure) with other household, factory and restaurant/cafe waste.

That means there’s some way to go before New Zealand runs out. 

In the meantime, the fun’s just starting in terms of scaling up the waste-to-gas business.

“I think I’d rather run around in Afghanistan than apply for resource consents.”

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