Investigating renewable feedstocks such as (Hibiscus Cannabis – Kenaf and Crotalaria Juncea – Sunn Hemp) for generation at Mackay Sugar Limited : final report GGP063

Abstract

As the Australian sugar industry embarks on the opportunity to value add from its waste streams our industry will become more sustainable into the future. This project has investigated the opportunity to replace the coal feedstock at the Racecourse Mackay Sugar co-generation facility with fibre, produced from fibre crops such as Kenaf and Sunn Hemp to power the steam boiler to generate electricity. The co-generation unit produces 31mwh of electricity and is powered by bagasse the waste stream from the sugar process and coal when the bagasse runs out. 30,000 tons of coal is burnt firing the steam boiler to generate electricity in conjunction with bagasse, the coal feedstock would require 90,000 tons of fibre to allow for the total replacement of coal. The fibre feedstock would also attract a green certificate value as the product is a renewable source.Mackay Fibre Producers (MFP) has produced the fibre crops for testing at Mackay Sugar, it has also investigate how the product would be prepared to allow it to be handled by the current bagasse handling system at the sugar mill. MFP produced Kenaf and Sunn Hemp for trials to be tested by Mackay Sugar, samples were taken and analysed by SGS lab to determine the combustion test and the residues left after the burning of the product. MFP has tested two harvesting processes and presented the two forms to Mackay Sugar. The bulk density of the two forms of product have been established, this information will be utilized in the business case. The MFP grower group has worked with members of the engineering and management team at Mackay Sugar Limited to develop the results compiled by this project.MFP has successfully produced Kenaf(cannabis hibiscus) and Sunn Hemp (crotalaria juncea) for testing at the Racecourse Mackay Sugar factory and delivered the product in a billet form as well as a foraged state. The kenaf hasn’t successfully flowed through the bagasse handling system, the fibre stands wrapped with componentry which could not be tolerated having the potential to choke feed systems. The chorine value’s of Kenaf were also outside the boiler specified levels which would have a detrimental effect on corrosion within the boiler. At this stage Kenaf would not be suitable as a feedstock to produce co-generation. However Sunn Hemp has met the feedstock criteria’s from the perspective of flowing through the current bagasse handling system, chorine levels are also at an acceptable level, the product calorific value will also meet an acceptable level. Sunn Hemp could be an alternative feedstock for the co-generation unit at the Racecourse Mackay Sugar Co generation unit.