Selecting reliable and robust freshwater macroalgae for biomass applications

• Published in: PloS one 2013-05, Vol.8 (5), p.e64168-e64168
• Main Authors: Lawton, Rebecca J, de Nys, Rocky, Paul, Nicholas A
• Format: Article
• Language: English
• Subjects: Aeration; Algae; Aquaculture; Ashes; Biochemical composition; Biodiesel fuels; Biofuels; Biology; Biomass; Biomass energy; Bioremediation; Calorific value; Carbon content; Carbon dioxide; Chlorophyta; Cladophora; Cultivation; Deoxyribonucleic acid; DNA; Earth Sciences; Fresh Water; Freshwater; Gracilaria; Industrial wastes; Moisture content; Nutrient removal; Oedogonium; Physiology; Polyculture; Productivity; Raw materials; Renewable energy; Rhodophyta; Seaweed - growth & development; Seaweed - metabolism; Seaweeds; Species; Species Specificity; Spirogyra; Stocking; Taxonomy; Ulva rigida; Water content
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0064168

Intensive cultivation of freshwater macroalgae is likely to increase with the development of an algal biofuels industry and algal bioremediation. However, target freshwater macroalgae species suitable for large-scale intensive cultivation have not yet been identified. Therefore, as a first step to identifying target species, we compared the productivity, growth and biochemical composition of three species representative of key freshwater macroalgae genera across a range of cultivation conditions. We then selected a primary target species and assessed its competitive ability against other species over a range of stocking densities. Oedogonium had the highest productivity (8.0 g ash free dry weight m⁻² day⁻¹), lowest ash content (3-8%), lowest water content (fresh weigh: dry weight ratio of 3.4), highest carbon content (45%) and highest bioenergy potential (higher heating value 20 MJ/kg) compared to Cladophora and Spirogyra. The higher productivity of Oedogonium relative to Cladophora and Spirogyra was consistent when algae were cultured with and without the addition of CO₂ across three aeration treatments. Therefore, Oedogonium was selected as our primary target species. The competitive ability of Oedogonium was assessed by growing it in bi-cultures and polycultures with Cladophora and Spirogyra over a range of stocking densities. Cultures were initially stocked with equal proportions of each species, but after three weeks of growth the proportion of Oedogonium had increased to at least 96% (±7 S.E.) in Oedogonium-Spirogyra bi-cultures, 86% (±16 S.E.) in Oedogonium-Cladophora bi-cultures and 82% (±18 S.E.) in polycultures. The high productivity, bioenergy potential and competitive dominance of Oedogonium make this species an ideal freshwater macroalgal target for large-scale production and a valuable biomass source for bioenergy applications. These results demonstrate that freshwater macroalgae are thus far an under-utilised feedstock with much potential for biomass applications.