The annual costs represent a range of expenses incurred in the running of the plant from payroll charges to maintenance costs. The most significant of these costs is depreciation, which is calculated using the FCI based on 10-year plant life as rec­ommended in Peters et al. [26] . All other annual costs were calculated using the methods specified in Molina Grima et al. [21] with the exception of labour, supervi­sion, wastewater treatment, and goods and services tax. Labour was assumed to be constant, with 12 employees working during the day and 3 working at night, each charged at the standard labour hourly rate given in ENR (US $34.16). Supervision was also assumed to be constant, with two managers working during the day and one at night, charged at the skilled labour hourly rate again outlined in ENR (US $44.99). Wastewater treatment cost was also estimated based on the costing data reported by Molina Grima et al. [21]. Finally, goods and services taxes were charged at a rate of 10%, reflecting the tax codes applicable to Australia.