Traditionally, wastewater treatment plants were solely designed to fulfil a vital role in ensuring public health and the protection of our natural environment. Through the progression of innovation and technology, SA Water’s facilities have evolved into rich sources of diverse, sustainable energy and water management opportunities, capable of generating their own power by harnessing biogas – a by product of treating sewage which is captured and turned into heat and electricity.
SA Water’s emphasis on green energy was typified earlier this year after brewing a genius idea which led to one of its major wastewater treatment plants producing record power generation.
Covid-expired beer brews energy ale
The closure of breweries, pubs and restaurants across Australia, to help stop the spread of COVID-19, created a vast oversupply of beer, forcing brewers to dispose of their product once it reached expiry.
Certain waste produced by industry, such as expired beer, is quite challenging and costly for manufacturers to manage, and unlike domestic waste, isn’t suitable for discharge to the wastewater network.
Rather than allowing the beer in South Australia to go to waste, the product’s high energy potential made it the perfect ingredient for a process known as co-digestion, which produces biogas – a source of green energy.
Millions of litres of beer that expired while the hospitality industry was shut down at the height of COVID-19 restriction measures quenched the thirst of digesters at SA Water’s Glenelg Wastewater Treatment Plant, boosting renewable energy generation to around 650 megawatt hours each month, for three consecutive months.
Destined to wet whistles before breweries, pubs and restaurants closed, the unused beer from local South Australian breweries was repurposed on-site and converted into electricity to power the plant’s treatment processes, reducing wastage and benefiting the environment.
SA Water Senior Manager Production and Treatment, Lisa Hannant, said beer was liquid gold for the digesters and fuelled record energy generation at the plant.
“Our Glenelg Wastewater Treatment Plant has always been a strong performer in generating its own energy from biogas, and the addition of ales and lagers took it to new heights amid the shutdown,” Ms Hannant said.
“Glenelg’s co-digestion program adds high strength organic waste from industry to sludge from the sewage treatment process, which is heated in the oxygen-free environment of the large, sealed concrete digester tanks, so it breaks down through natural bacterial metabolic processes and releases biogas.
“Harnessing the power of biogas through our on-site gas engines creates renewable energy for the treatment plant and a sustainable alternative for industrial waste that’s otherwise difficult to dispose of and treat.
“Beer’s high calorific load and methane potential means it’s perfect for co-digestion and by adding around 150,000 litres of expired beer per week, we generated a record 355,200 cubic metres of biogas in May and 320,000 cubic metres in June, before topping our May record in July with 371,600 cubic metres.
“To put these figures into perspective, the electricity generated by our engines from biogas is enough to power 1,200 houses.
“Honourably, our thirsty digesters have been doing their bit for the environment by drinking themselves silly and with such a horrific diet it’s no wonder they produce so much gas!”
Prior to their recently developed taste for beer, the digesters would typically generate enough biogas to provide around 80 per cent of the Glenelg facility’s energy needs.
The plant’s record power generation made it 97 per cent energy self-sufficient during July this year.
“Many businesses have been impacted by the restrictions in place to stop the spread of COVID-19 and this is just one example of how an industry has remained resilient and adapted to ensure their resources aren’t wasted, while enabling a beneficial outcome for the environment,” Ms Hannant said.
“Breweries have since adjusted their production schedules following the easing of restrictions in South Australia which enabled the hospitality industry to reopen, and our biogas generation for August returned to normal levels, so we’re glad the beer is ending up where it’s intended.”
First operational in 1932, the Glenelg Wastewater Treatment Plant treats around 20 per cent of Adelaide’s sewage – processing, on average, 55,000 litres each day.
Rich resource recovery opportunities
Biogas production is linked to the nature and volume of substrates entering the digesters, which are typically in the form of primary sludge and waste-activated sludge.
The co-digestion process is unique to SA Water’s Glenelg plant, however anaerobic digesters in place at its Bolivar and Christies Beach facilities also convert waste to energy to help power treatment operations.
Ms Hannant said extracting opportunities for resource recovery at wastewater treatment plants delivers rich economic and environmental outcomes.
“Our treatment facilities have evolved from their traditional role of protecting public health and are now regarded as valuable sources of sustainability,” Ms Hannant said.
“By combining innovation, technology and waste management, we’re nurturing a circular economy which champions water reuse opportunities and renewable energy, to pave the way for a green future.
“Bolivar’s existing digesters create and capture enough biogas to cover up to 90 per cent of the plant’s energy requirements, and we’re now exploring initiatives to optimise gas yields.
“As one of South Australia’s largest electricity users, it’s important to identify and invest in opportunities that enhance our sources of clean energy, such as producing biogas.
“This sustained focus on generating renewable energy is reducing our carbon footprint, improving operational efficiencies, contributing to a healthier environment and ultimately keeping costs down for our customers.”