Abstract
Microalgae are a renewable source of unconventional biomass with potential application in the production of various biofuels. The production of carbon-neutral fuels is necessary for protecting the environment. This work determined the possibility of producing biomass of microalgae belonging to Monoraphidium genus using saline wastewater resulting from proecological salmon farming in the recirculating aquaculture system. The tests were carried out in tubular photobioreactors using LED light. As a part of the analyses, the growth and productivity of microalgal biomass, cell density in culture, and lipid concentration and ash content in biomass were determined. In addition, the concentration of selected phosphorus and nitrogen forms present in wastewater corresponding to the degree of their use by microalgae as a nutrient substrate was determined. The biomass concentration estimated in the tests was 3.79 g·L−1, while the maximum biomass productivity was 0.46 g·L−1·d−1. The cells’ optical density in culture measured at 680 nm was 0.648. The lipid content in biomass was 18.53% (dry basis), and the ash content was 32.34%. It was found that microalgae of the genus Monoraphidium effectively used the nitrogen as well as phosphorus forms present in the wastewater for their growth. The total nitrogen content in the sewage decreased by 82.62%, and total phosphorus content by over 99%. The analysis of the individual forms of nitrogen showed that N-NO3 was reduced by 85.37% and N-NO2 by 78.43%, while orthophosphate (V) dissolved in water was reduced by 99%. However, the content of N-NH4 in wastewater from the beginning till the end of the experiment remained <0.05 mg·L−1.
Highlights
The rapid increase in population has resulted in a growing energy need, which is estimated to increase further by ≥50% by the year 2030 [1]
We investigated whether (1) Monoraphidium can be grown using the saline aquaculture-derived wastewater and (2) how the uptake of nutrients from such wastewater can decrease the costs of fertilizer
Microalgae were purchased from the Culture Collection of Baltic Algae (CCBA)
Summary
The rapid increase in population has resulted in a growing energy need, which is estimated to increase further by ≥50% by the year 2030 [1]. As conventional energy resources are shrinking, intensive research is underway exploring the technologies for using renewable energy resources and analyzing the possibilities of reducing the costs of their use. The use of renewable energy can enable reducing air pollution and carbon dioxide emissions worldwide, maintaining the principles of sustainable development [2]. A large part of the world’s energy demand is covered by conventional energy sources, including coal, oil, and natural gas, in recent years, competition for them has widely increased, and sources including wind, sun, water, and geothermal energy are being studied [3]. Bioenergy increases energy independence and reduces greenhouse gas (GHG) emissions [5]. The implementation of modern technologies will significantly increase its share in the energy mix to a level of 108 exajoules (EJ)
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