Why electricity will replace coal in dairy plants

Dairy factories mostly use coal to power the boilers needed to dry milk into powder. Synlait is taking the plunge to install an electricity-powered boiler. It will be the first of many. Gavin Evans explains why that matters.

New Zealand is unlikely to see another large-scale coal-fired boiler installed, Energy Plant Solutions managing director Brendon Stephensonsays.

The 6 MW electrode boiler the firm will install at Synlait’s Dunsandel plant later this year is unlikely to be the last, he says.

The high-voltage boiler technology, coupled with growing consumer demand for products with a low-carbon footprint, will push the country’s food processors away from the coal many rely on for process steam and hot water.

“With the focus on renewables these electrode boilers are really coming to fruition,” Stephenson told Newsroom.

“It takes one to take the plunge and then the rest will follow.”

“I would be surprised if another large-scale coal-fired boiler is installed in New Zealand.”

The implications are huge. Heavy industry contributes more than a fifth about of the country’s emissions. And while major sites - like the Glenbrook steel mill or  Fonterra’s Edendale plant - are big contributors, there are dozens of smaller sites where their next boiler replacement, or expansion, could be done with an electric unit of the size planned for Dunsandel.

Stephenson says three-quarters of the country’s boilers are probably 5 MW or smaller.

“There are hundreds and hundreds of them.”

The firm has 16 staff and will take on more contractors for the Synlait project, Stephenson says.

Synlait moves ahead of Fonterra

Synlait announced its plans for a $125 million liquid milk plant at its Dunsandel site in December. Its decision to opt for an electrode boiler there – and a commitment to install no new coal-fired capacity across the company – was announced this month among a set of new sustainability goals.

They include commitments to halve off-farm emissions per kilogram of milk solids by 2028. On-farm emissions will be reduced by 35 per cent on the same basis.

Synlait says the new boiler will operate at about half capacity initially and can be upgraded to 12 MW further down the track. At 6 MW the annual emission saving relative to coal is equivalent to taking more than 5,300 cars off the road.

Fonterra last year pledged to install no new coal boilers after 2030. It is seeking a site to trial an electric boiler and In the meantime is investing $1.5 million to convert a coal boiler at its Brightwater plant near Nelson to also burn wood. It expects a 25 per cent decline in site emissions as a result.

It’s an opportunity that excites Energy Efficiency & Conservation Authority chief executive  Andrew Caseley.

His organisation had been looking for some time for a business to work with at this scale of deployment to provide a demonstration site for the wider food processing industry. That’s why the authority was prepared to contribute $250,000 to the cost and provide technical advice.

“This technology is not size-constrained,” he says. “Much bigger units are used internationally.”

Many of New Zealand’s industrial boilers are much larger. Synlait’s biggest coal-fired boiler is 25 MW.

Caseley says the electric boilers are proven technology that will potentially have broad application in many industries. One of the key things to learn from this project is the potential impact on the local power supply and the level of investment and time needed if that has to be increased or reinforced.

Christchurch-based network company Orion has doubled the capacity of transformers at Dunsandel, south-west of the city, and will install two new 11 kV lines to supply the site.
David Freeman-Greene, the firm’s commercial general manager, wouldn’t say how much the work has cost, given it was funded by Synlait.

Twice as expensive as coal

Synlait says the total investment – including the network upgrade and running costs – on a 10-year basis will be about twice what the company would have spent on a coal unit. Going to 12 MW won’t require further investment in electricity infrastructure.

Chief executive  John Penno told investors that expected increases in carbon costs and the country’s increasing investment in low-cost renewable power supply made the electric boiler a “sound economic decision for us.”

The company had considered using electricity in its first boiler at the $200 million infant powder plant it plans at Pokeno, south-east of Pukekohe, but the local power supply was insufficient.

And while the gas-fired boiler planned there will have about a third of the emissions of a coal-fired unit, Penno says electricity is an option for any further boilers it installs there.

“We would like to get away from gas if it’s possible but there’s some engineering work to be done to see if its viable.”

No piped gas in South Island

Many of the country’s biggest meat and dairy processing sites are on the South Island where there is no piped gas supply. Firms including  Danoneand  Westland Milk have installed LPG-fired units during recent expansions.

Palmerston North-based EPS has installed more than 150 MW of boiler capacity in the past seven years, including gas, LPG and biomass-fired units.

Boiler made in China

The 30-tonne pressure vessel for Synlait – which will be 6.5 metres high and three metres wide - will be fabricated in China. All the valving, instrumentation, insulation and control systems will be added here.

Electrode boilers rely on an 11 kV power supply. Typically, an industrial site would have a 400-volt supply, with a step-down transformer between it and the distribution network, Stephenson says.

While electricity is generally more costly than other boiler fuels, the efficiency gains can be considerable. A large volume electricity buyer should also be able to negotiate a better price, he says.

Stephenson says the electrode boiler is about 99.5 per cent efficient, whereas gas-fired units may achieve 90 per cent efficiency with heat recovery units, and coal about 70 per cent.

Quicker to boil

Another big advantage of the electrode units is their responsiveness. Not only can they be quickly turned on and off, but they can come up to heat in minutes, compared with about four hours for a coal-fired boiler. During the dairy season a coal unit may remain running at low heat all day.

Stephenson says a big determinant in the economics of installing an electrode boiler will be whether a site has ready access to an 11 kV power supply.

“If the power is there and it’s at 11 kV and there’s enough capacity, than its relatively easy.”

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