Australian canned fruit and fruit drinks company Golden Circle is planning to install a larger boiler to take better advantage of biogas produced from the anaerobic wastewater treatment at the factory’s food processing plant in Northgate, Queensland.
The existing boiler burns around 30% of the biogas produced, while the new boiler will utilise about 90% of the generated biogas.
Golden Circle’s wastewater plant, which includes a third digester utilising CST Wastewater Solutions ’ and Global Water Engineering's (GWE) high efficiency anaerobic technology to produce biogas, has already saved Golden Circle more than $2 million a year in effluent disposal since the plant's upgrade to cope with increasing production volumes.
Golden Circle manufactures more than 400 products, including shelf-stable fruit and vegetables, fruit juices and cordials. At it's main processing operation at Northgate in north Brisbane, Golden Circle operates an Upflow Anaerobic Sludge Blanket (UASB) wastewater treatment plant. Wastewater fed into the anaerobic wastewater treatment plant is mainly from the company's fruit processing operations. Solid matter is first separated out as much as possible, leaving mostly dissolved fruit sugars.
Two digesters were installed in 1989, while a third digester from GWE was added in 1996 to cope with increasing production volumes at the plant. This anaerobic wastewater treatment plant has reduced the concentration of fruit sugars in the effluent, saving Golden Circle $2 million a year in discharge fees, although there is still some daily discharge to the Queensland Urban Utilities sewage treatment system.
Biogas from the Northgate factory began to be utilised in the late 1990s to contribute to the steam needs of the operation, after previously being flared off. The biogas presently feeds a 3.5 MW boiler that produces about 5T of steam per hour, used for cooking foods, pasteurisation and sterilisation.
Biogas from the anaerobic wastewater treatment plant does not supply all of the Northgate factory’s steam needs, but supplements the steam produced by burning coal. Currently the burnt biogas is offsetting about 5% of coal usage, while the new boiler will offset 15%. This need for this coal usage offset comes as energy prices rise and the need to curb greenhouse emissions grows.
According to CST Wastewater Solutions, which supplied the GWE digester in 1996, the concept of using wastewater to create green energy is much more widely applicable than is often realised.
“Any factory with a biological waste stream or wastewater with high COD (Chemical Oxygen Demand) can easily use this model to generate energy,” says Michael Bambridge, Managing Director of CST Wastewater Solutions.
“So far, most industries have been focusing on treating their effluent to meet local discharge standards. While this can contribute to reduced discharge fees, wastewater treatment installations have never been seen as significant revenue generators.
“However, by using anaerobic wastewater treatment to generate biogas, an entirely different light is shed on the cost structure of wastewater treatment infrastructure. It can now become a substantial additional source of income for many factories and processing plants, especially those involved in vegetable matter and other primary product processing,” he adds.
The first benefit of anaerobically treating the organic effluent and waste material is of course cleaner effluent. On average the removal efficiency of GWE’s anaerobic wastewater treatment installations is as high as 90-95%, easily bringing the organic load down to regulatory discharge standards for most types of wastewater.
“For the most heavily loaded wastewaters, extra post-treatment steps can further purify the effluent, meeting even the most stringent discharge regulations for water re-use," says Bambridge.
Besides cleaning the wastewater (which other processes can ultimately achieve), the greatest advantage of anaerobic wastewater treatment is the controlled, continuous production of valuable biogas. Other types of treatment, such as aerobic, do not provide this benefit.
Closed anaerobic reactors generate large quantities of methane (CH4) from the organic materials in the wastewater that can diminish or even completely replace the use of fossil fuels in the production process.
Industries with high organic loads can generate enough biogas to fully cover a factory’s energy needs and still have a biogas surplus to feed it into power generators and sell electricity to the national grid.
Besides the economical advantage of anaerobic wastewater treatment, there isa lso the environmental advantage, significantly reducing a factories’ carbon footprint. Closed anaerobic process systems prevent large quantities of CH4 being emitted into the atmosphere.
With CH4 being 21 times more harmful to the atmosphere than carbon dioxide, anaerobic wastewater solutions can qualify for Emission Reduction Certificates for projects in countries listed under the United Nations Kyoto Clean Development Mechanism (CDM) and Joint Implementation (JI) programs.
Typical industries amongst GWE’s proven references that are very suitable for anaerobic wastewater treatment are:
- food processing & canning (fruits, vegetables, meat, fish, seafood)
- snacks, confectionary, dairy
- beer and beverages (beer, soft drinks, tea, coffee- and milk-based drinks, fruit juices)
- fermentation industry (alcohol, yeast, monosodium glutamate etc)
- biofuels (ethanol, biodiesel)
- pulp & paper
- agro and agro-processing industries (vegetables, beet sugar, starch, palm oil)
- petrochemical (PTA, PET, glycol and polyester factories).