The Oakey Beef Exports (OBEX) in Queensland's Darling Downs is using technology to turn the wastewater from its processing floors into biogas, which is then used to partly power its plant.
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The new COHRAL green energy storage facility.

Global Water Engineering's (GWE) COHRAL (Covered High Rate Anaerobic Lagoon), which was installed by CST Wastewater Solutions, integrates waste treatment with biogas storage, processing and combustion.

The orb-shaped green energy storage facility that's installed at the beef processing plant is helping to demonstrate how industry can profit from environmental initiatives.

Previously, the preferred option for treating abattoir wastewater was with an uncovered anaerobic lagoon, which, though fairly efficient in reducing contaminants, does have a few operational problems - the key being the release of greenhouse gases in the form of methane. 

According to QBE environmental officer Kelly Hawkins, this forced OBEX to take a different look at its business and view waste, not as an expensive cost item, but as an income producing stream.

"It's quite a sophisticated technology when you compare it to our old wastewater treatment systems, and is the first of its kind in Australian abattoirs," Hawkins said.

"The initiative is expected to offset OBEX dependence on natural gas for boilers by substituting it for captured and processed biogas, with the site's dependence on natural gas estimated to be reduced by about 45%, and the site's emissions reduced by around 37%.

"The biogas plant is not yet fully operational, however it currently supplements natural gas with biogas every 2-3 days - the boiler has used approximately 500,000 cubic meters of biogas so far.

"The price of natural gas is variable, but based on last financial year's gas prices this will save us approximately $670,000 per year."

The 26-metre high flexible storage tank features resilient flexible double membrane storage so that gas produced by the COHRAL plant can be safely stored separately from the gas generator. 

The SATTLER biogas storage design selected for OBEX is engineered to be permanently gas-tight with high operational reliability and optimum safety. 

The double membrane gas storage tank consists of an external membrane that forms the outer shape of the tank, as well as an internal and a bottom membrane that make up the actual gas space. 

A permanently running support air blower provides air to the space between inner and outer membrane, thus keeping the gas pressure up at a constant level, irrespective of gas supply and withdrawal.

OBEX manager Pat Gleeson said the project so far had been a success and the process has been a real learning curve for himself and his staff.

"We can see it's going to be very effective when we finalise it all but there's still a bit of work to do yet," Gleeson said.

"The COHRAL plant is expected to repay its cost of construction inside five years through gas purchase savings amounting to many millions of dollars, then continue to deliver benefits and profitability virtually in perpetuity." 

The Queensland government has committed more than $1.2 million in several biogas production projects in the hope the research would help the state transition to a clean energy economy. 

 ssociate professor ernadette cabe and  manager at leeson Associate professor Bernadette McCabe and OBEX manager Pat Gleeson.

 

University of Southern Queensland researcher and associate professor Bernadette McCabe was given $300,000 as part of the state government funding initiative to perfect the process.

Her research team take samples of the water to a Toowoomba lab where the process is recreated on a smaller scale to determine a method of best practice to improve the operations of the plant.

They will review the current performance and seek measures to improve the production of biogas from red meat processing.

They will also develop novel decision support tools and processes for easy assessment and improvement on the performance of the system. 

According to McCabe, while Australia's top five processors are currently capturing biogas from wastewater, there is still considerable scope for process improvement.

"Existing biogas installations at these plants have had varied success and performance efficiency of the digestion process could be improved by up to 30% in some cases," McCabe said.

"A key issue limiting the performance of covered anaerobic lagoons in red meat processing is the nature of wastewater, which is very high strength, and whilst this provides excellent potential for biogas production, it does present operational problems. 

"Plant operators need to be acutely aware of how to manage waste streams to minimise solid loadings such as fat, which can negatively impact the performance of biogas technology systems."

"Advanced systems like COHRAL and those that incorporate heating and stirring options require considerable capital investment, thus plant operators need to have confidence that the waste stream entering the digester will not impact on its operation, but at the same time produce the maximum amount of biogas."

McCabe adds that in the past decade there's been considerable interest in alternative technologies for the treatment of solid and liquid waste. 

This is driven by rapidly increasing energy costs, increasing fertiliser and disposal costs, odour emissions, urban encroachment onto rural areas, and potential for improved regulatory compliance.

"There is growing interest in the use of co-digestion to boost biogas production in Australia, particularly for small wastewater facilities," McCabe said.

"I'm working on initiatives with industry and government to assess the feasibility of producing energy and fertiliser in regions where there is a high concentration of multiple waste streams from farm and industry waste.

"We are starting to see instances where the once parallel fields of water and waste management, and energy are teaming, coupled with better infrastructure planning, and this will only help with the adoption of biogas technology.

"Knowledge sharing between industry, the government and research institutions are key."