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Emergy analysis of oil production from microalgae

Cruz, Rui Vogt Alves da, Nascimento, Claudio Augusto Oller do
Biomass and bioenergy 2012 v.47 pp. 418-425
Cyanobacteria, biofuels, biomass, capital, carbon dioxide, emergy, harvesting, microalgae, oils, operating costs, raw materials, sustainable technology
The use of microalgae and cyanobacteria for the production of biofuels and other raw materials is considered a very promising sustainable technology due to the high areal productivity, potential for CO₂ fixation and use of non-arable land. The production of oil by microalgae in a large scale plant was studied using emergy analysis. The joint transformity calculated for the base scenario was 1.32E + 5 sej/J, the oil transformity was 3.51E + 5 sej/J, the emergy yield ratio (EYR) was 1.09 and environmental loading ratio was 11.10 and the emergy sustainability index (ESI) was 0.10, highlighting some of the key challenges for the technology such as high energy consumption during harvesting, raw material consumption and high capital and operation costs. Alternatives scenarios and the sensitivity to process improvements were also assessed, helping prioritize further research based on sustainability impact.