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As energy costs continue to rise, a leading cereal manufacturer uses anaerobic digestion to generate energy from organic waste. This allows them to reduce energy costs while also reducing environmental impact.

Background

Waste management is a complex issue that can have significant effects on the environment and requires careful consideration. Smart new technologies and processes to avoid, reduce and recover waste can help to decrease the amount of waste being sent to landfill.

The process of anaerobic digestion converts commercial and industrial waste into onsite electricity, heat, and clean methane gas. It produces large quantities of biogas, comprising methane and carbon dioxide. The cleaned methane fraction can be stored, pressurised, and used to generate onsite power and heat, with surplus fed into the electricity grid, or used to power equipment and vehicles.

As energy costs continue to rise, more manufacturers are realising the benefits of using anaerobic digestion to create energy for their plants. With a strong commitment to its social and environmental responsibilities, a leading manufacturer of high-quality cereal products and ingredients, recently commissioned an Australian energy company to establish an anaerobic digestion plant at their manufacturing plant.

The plant will generate methane gas from oat husks and will use this fuel in a combined heat and power generator unit to offset in full their existing and future energy requirements with surplus energy exported to the grid.

A Scalable Solution

Auto Control Systems (ACS), a Rockwell Automation Silver System Integrator, was tasked with developing the automation and control system for the anaerobic digestion plant. Based in Perth, Australia, ACS is a premier provider of industrial automation and control systems, and services in Australia. Andrew Taylor, Engineering Manager at ACS, detailed the importance of having a scalable solution for the plant.

“A scalable solution delivers the flexibility to scale up or down depending on their needs. The automation and control solution we developed delivered that flexibility in a scalable, containerised package. After it was built and pre-tested here in Perth, it was transported to the customer site ready for installation,” he explained.

The Allen-Bradley® CENTERLINE® 2500 IEC Low Voltage motor control centre (MCC) from Rockwell Automation was at the heart of the solution. With Ethernet connectivity, the CENTERLINE MCC streamlined the pre-testing process and ArcShield technology increased protection against internal electrical arcing faults, providing an extra level of safety. Control of the plant’s processes was provided by the Allen-Bradley CompactLogix™ PLC and the PowerFlex® 525 and 753 AC drives deliver the reliability to meet the application requirements of the plant. FactoryTalk® View SE delivers an accurate real-time view of the process with alarming via SMS and allowed ACS to utilise the PlantPAx® libraries to reduce their engineering overheads.

“A pilot plant was developed for this technology almost 10 years ago and the ongoing reliability of that plant utilising the Rockwell Automation technology is impressive, it’s a proven solution. The CENTERLINE MCC was an excellent choice because knowing that the new standard, AS/NZS 61439, would soon be mandated, it was important to make sure the solution met the requirements of this standard,” said Taylor.

Raj Singh, channel account manager, Rockwell Automation added, “Our ultimate aim is to help companies reduce the time from inception to market. Leveraging PlantPAx DCS process object libraries helps reduce the overhead required for the automation infrastructure while delivering improved diagnostics and analytics. Overall, the system features positively impact the lifecycle of the plant operations by ensuring that plant-wide and scalable systems drive productivity, improve profitability, and reduce overall risks for operations.”

Transforming Waste into Energy

The anaerobic digestion process starts in the storage tank where waste oat husks are stored prior to being processed. The husks are then injected into the reactor tanks where they are heated, stirred and then cooled. The four main stages of the process are hydrolysis, acidogenesis, acetogenesis and methanogenesis. Each stage digests the matter into smaller parts, ultimately resulting in a mixture of methane, biogas, water and digestate. The raw biogas is then used to generate heat and electricity for the plant with surplus energy being exported to the grid.

The anaerobic digestion process is continuous and therefore needs to be closely monitored for pH and temperature by the control system. ACS was responsible for the hazardous area accreditation and has full remote access to the plant.

Powering Oat Production

Anaerobic digestion provides many benefits to business, including eliminating transport costs and gate fees for waste disposal; reducing energy costs; the ability to power vehicles and equipment with upgraded biogas; monetising valuable carbon credits under the Australian Government’s Clean Energy Futures Scheme and; monetising surplus electricity fed into the grid.

The anaerobic digestion plant has been successfully commissioned and gas is currently being produced. At the moment this gas is being flared but when fully operational, the manufacturing plant will be generating 1.5MW of electricity and heat which will be used to offset in full the plant’s existing energy requirements.

To discuss a solution for your business please contact us at sales@autocontrols.com.au