Abstract
With the increasing participation of biomass in the world energy matrix, large amounts of ash are produced through combustion, resulting in the need to dispose of this waste to minimize the environmental impact. An alternative is to use ashes as phosphorus supplements in microalgae cultures. The present work describes the development and use of a balanced culture medium based on the minimal processing of oil palm biomass ash to cultivate Arthrospira platensis Paracas, Neochloris oleoabundans UTEX 1185, and Dunaliella salina SAG 184. The acid extraction process of phosphorus (P) was defined by evaluating the following parameters: temperature (20 to 70 °C), acid load (0.01 to 0.03 mols/g of ash) of HNO3, and liquid/solid ratio (50 to 150 mLg−1). The best efficiency of the extraction process was 97%. The use of HNO3 allowed for the production of an extract containing balanced amounts of N and P sources, the BAX medium (Biomass Ash Extract). This medium was efficient for cultivating the three microorganisms studied, reaching biomass concentrations of 2.03, 0.902, and 0.69 g/L or 84%, 82%, and 99% of the control concentrations for A. platensis, N. Oleoabundans, and D. salina, respectively. In a final scaling-up test, A. platensis showed productivity of 0.047 g L−1d−1 in a 120 L tank in a greenhouse. BAX can be an alternative nutrient medium for microalgae cultivation, especially in integration with biomass-fueled biorefineries.
Highlights
IntroductionBioenergy participation in the world energy matrix has been growing by 8% yearly since 2006 [1]
The temperature and liquid/solid ratio used were based on the literature, while the amount of acid was calculated based on the amount of phosphate theoretically extractable to give extracts respecting the Redfield ratio [54,55]
Even if the equipment is simple compared to the large-scale equipment used in palm processing, it involves a capital cost that would have to be compensated by the income from biomass products. This requires a process simulation and sensitivity analysis to indicate if microalgae production, technically feasible, can be profitable in its biorefinery integration with palm processing. This proof-of-concept study proved that minimally processed palm ash could be used in microalgae production
Summary
Bioenergy participation in the world energy matrix has been growing by 8% yearly since 2006 [1]. It is estimated that by 2050, up to 33–50% of the world’s primary energy consumption could be provided by biomass [2,3]. Plant biomass used directly as an energy source contributes to 10% of the global energy supply. Part of this use is for cooking and heat, generating a scattered residue. Much of the biomass is used in industries—16 to 18% in the United States of America, India, and Brazil in 2009 [4]. This industrial use generates large and localized volumes of ash, which must be disposed of
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