It’s been a bit of a battle but biogas plant EarthPower is now making money and electricity. As landfill charges rise and parts of the operation are upgraded it is well placed to power ahead.

A giant gurgling stomach in the middle of Sydney is proof you can make good use of leftovers. It’s also evidence that hard work and compromise can sometimes save a project from a premature demise. In the world of generating energy from non-conventional resources, where so much is new and untested, it often takes raw determination to show that an idea can work.

In the case of EarthPower, where two digesters tower up behind a giant shed in an industrial zone on the banks of the Parramatta River, the fact it is generating electricity and revenue – with fertilizer as a commercial byproduct – is reason enough to give anyone hope for the future of waste-to-energy projects.

But it was touch and go there for a while.

EarthPower began operations in 2003 but struggled in its early days, general manager David Clark tells EcoGeneration during a site visit in November. With a million or so tonnes of food waste going to landfill it shouldn’t have been too hard to get 80-120 thousand tonnes to the EarthPower plant, but waste companies were stuck in their ways and those that did choose to deliver to the plant were not so good at separating out contaminants such as plastic, metal and glass.

Gate fees for landfill at the time were about $80 a tonne, Clark says, and separating out contaminants added more cost for customers. The plant couldn’t attract enough waste, and what it got was often littered with other useless stuff. It was time for compromise, so EarthPower relaxed its requirements from less than 5% contaminants to less than 25% and built a pre-treatment facility where non-degradable detritus would be removed.

The new regime proved too hopeful. Pretty soon the high levels of contaminants such as glass and polystyrene caused problems in processing and extra waste to landfill. Some equipment for pre-treatment was taking a hammering and just wasn’t fit for purpose.

Shaky ground

There were dark days at the plant. By 2007 the global financial crisis was sending shivers around the world and EarthPower’s owner, merchant bank Babcock & Brown, decided to sell the plant to waste giants Cleanaway and Veolia as a joint-venture. But separation of contaminants was still a problem and part of the plant was decommissioned in 2009. With a leaner operation it was decided to rein the contamination limit back to 5%, ban glass and plastic and tolerate single-layer plastic.

Slowly things improved and throughput today is about 50,000 tonnes a year, up from 30,000 tonnes.

Most of EarthPower’s revenue comes from gate fees, which range between $200 to $250 a tonne depending on quantity and quality.

“If we put our prices up to landfill [about $300 a tonne] or higher people would say it’s too much trouble and take it to landfill, which is kind of sad because I believe we have such a good environmental outcome,” says Clark, who is certain the plant’s location, in the geometric centre of Sydney, will ensure it grows as landfill charges rise.

Other people’s rubbish

It’s Thursday morning at EarthPower and a truck is backing off the weighbridge to dump its load of smelly edibles beside a huge tub at the bottom of a screw conveyor. A front end loader scoops and dumps, scoops and dumps, its huge wheels spinning slowly on the greasy concrete floor. The food is conveyed to a hydropulper, essentially a giant blender, where liquid is added and the organic slurry – about 4% solids – is stored before it is required in the anaerobic digestion tank out back.

A steady feeding of digesters works best, says Clark, a chemical engineer. “If you over feed them you can in a very short time make them become upset and the methane quality can drop away quite quickly.”

In the digester, the temperature hovers around 27 degrees Celsius as bacteria go to work and biogas methane is produced. The digester holds up to 4,600 cubic metres of goo, and it’s usually filled up to about 11 metres, Clark says.

EarthPower general manager David Clark.

It’s like a giant chemistry set, where some sludge is dewatered and sent to a drying plant to be made into fertiliser and the rest is sent back to the digester to maintain the population of microbes. The biogas is sent to a row of three V16 generators, where one is usually employed to drive alternators and generate electricity – about 8GWh a year – that is exported to the network.

EarthPower sells its green electricity to EnergyAustralia, and before the current contract it sold to Diamond Energy. Clark has watched the power price rise over the three-year term of the contract and will be interested to see how negotiations take place for the next one.

The plant runs on imported electricity and all generated electricity is exported. More goes out than goes in, making the plant a net exporter. There’s plenty of roofspace at the site but Clark isn’t considering solar. “It would add complexity,” he says. Some biogas is used in the drying process and some is flared. None is sold. Jacket water heat from generators is sent to heat process water and the digester and exhaust heat is used to dry digested food waste, preparing it to become fertilizer.

Power out

The engines are nearing the ends of their lives and Clark expects modern replacement gas engines will lead to more efficiencies and availability. If two are run all the time and all the plant’s gas is used to fuel them the operation will produce more electricity.

The digesters are surprisingly responsive for their size, he says. “It gets that sugar hit straight away,” he says. “That means the digesters are very healthy; than can take that food and process it.”

Waste-to-energy technology is becoming far more stable, says BioEnergy Australia CEO Shahana McKenzie, and the raw materials will always be on hand. As councils and state governments set targets towards zero waste policy there will be fewer and fewer options about what to do with degradable matter. “There’s a long way to go but we are definitely heading in the right direction,” McKenzie says.

National consistency for waste levies and gate fees would make a massive difference, she says. In Queensland there is no waste levy at all. “We are advocating for a national consistent approach to the waste levy that would be at a level that would be enough to increase the sustainability of these projects.”

Investors are at the fringes, weighing their options. The Australian Gas Infrastructure Group announced at the Bioenergy Conference in Sydney in November that it would like to use biogas to supplement line losses. “There’ll definitely be some progress in that in the coming years,” McKenzie says. Funding has already been announced for two projects in Perth.

Back at EarthPower a gaggle of visitors fresh from the conference gather around Clark to look at the fertilizer which is the plant’s final tangible product. Not so long ago the project was on the brink but now it produces enough electricity to power about 6,000 households.

Waste-to-energy technology might play at the margins of the clean energy transition but it is a better solution than landfill and it can turn a profit.

“It can be done,” Clark says. “It is achievable.”