ABSTRACT A recent report published by the University of California at Berkeley (Lundquist et al, 2010) does not project a favourable outcome for near-term, large-scale algal biodiesel production without wastewater treatment as the primary goal. This view is reinforced by a recent change in emphasis in wastewater treatment technology, from simply oxidizing the organic matter in the waste (i.e. removing the BOD) to removing and recovering the nutrients, specifically nitrogen (N) and phosphorus (P), the root cause of eutrophication of inland waterways and coastal zones. Nowadays, progressive wastewater treatment plants operate as recovery plants, recovering water, nutrients, metals and energy. This growing need for nutrient removal and recovery markedly improves the prospects for using algal ponds in wastewater treatment, since microalgae are particularly efficient in capturing and removing N and P over a large range of ratios and concentrations, by supplementing the cultures with CO2. In this paper, the lifetime net present values (LNPV) and carbon footprints of four processing pathways for the future development of Melbourne’s two largest treatment plants are discussed and compared. Each pathway combines algal biomass production with fuel and/or energy production and various co-products. They have been assessed using a spreadsheet model developed by CSIRO. Preliminary results indicate that: (1) different nutrients (C, N or P) could limit the plants under each pathway, and (2) algal oil suitable for the production of biodiesel could be produced for half the current retail price of diesel in Australia (i.e. for less than US$1 per litre). The algae-to-biodiesel pathway combines algal growth ponds and oil extraction with anaerobic digestion of the residual algal biomass for energy purposes. It has an impressive carbon footprint. Reference: |