Macadamia Nut Power Plant

Grid connected, renewable cogeneration
Location: Gympie, QLD

The site

Regionally based Suncoast Gold Macadamias (SGM) processing site produces about 5000 tonnes of waste macadamia nut shells each year. The shells previously were sent to landfill, garden mulch or burned to produce heat. The plant will now utilise the shells as fuel for cogeneration, thereby increasing the energy efficiency of the site.

Technology

The 6 MW, high pressure steam boiler produces nine tonnes of steam per hour, which is used in the nut process and to generate electricity. The process steam is passed through a plate heat exchanger to create hot water. This is used to dry the nuts in their shells in storage silos. The remaining steam is passed through a 1.5 MW steam turbine. During any hour of operation the plant can convert 1680 kg of waste shell into 1.5 MW of electricity. The plant is connected to the local (Energex)11 kV grid via a 2 MVA transformer.

Energy Purchase and Supply

The plant is registered as a non-scheduled generator in the National Electricity Market (NEM). The plant works in season from April to end November - five to six days a week to production requirements. The steam turbine generates about 9.5 GWh per annum of electricity, of which 1.4 GWh is consumed onsite. The remaining 80 per cent is exported to the grid. Under the third party power arrangement, the host gains steam and electricity without charge in return for supplying the fuel source and plant site. The power plant is eligible to create Renewable Energy Certificates under the Mandated Renewable Energy Target, which Ergon Energy has rights to under long-term agreement.

Future

By 2005 it is expected that the facility will double its power output.More than 150 growers throughout Queensland and northern New South Wales could supply up to 10,000 tonnes of macadamia nut shells. Investigations are also under-way into utilising the reject nut-in-shells that were previously burnt as waste.