Feasibility and efficiency of microalgae cultivation for nutrient recycling and energy recovery from food waste filtrate

Abstract

With the continuous growth of economic and population, the generation of food waste has significantly increased in recent years. The disposition of food waste, typically through incineration or landfill, can lead to severe health and environmental problems, accompanied by high additional costs. However, the leachate produced from food waste during collection, transportation and landfill operations predominantly contains high levels of nutrients necessary for microalgae growth. The integration of microalgae cultivation into waste treatment for nutrient recycling presents a potential route for energy recovery from food waste. Therefore, this study was conducted to evaluate the feasibility of microalgae cultivation for food waste filtrate treatment. In addition, the optimal cultivation conditions and nutrient removal efficiency for microalgae in food waste filtrate treatment were investigated. The results indicated that Cyanobacterium aponinum exhibited the highest growth rate (0.530 cells d-1) and maximum cell density (9.6 × 106 cells mL-1) among eight potential microalgal species in 10% food waste filtrate treatment under 10,000 lux and 32°C. It was also observed that C. aponinum had significantly higher biomass productivity and nutrient removal efficiency under a 5% CO2 concentration. The successful cultivation of C. aponinum demonstrated that food waste filtrate could be a promising growth medium, reducing the high cost of cultivation with synthetic medium. However, further efforts should be made to utilize microalgae in food waster filtrate treatment, transitioning from laboratory condition to a pilot scale.

Fig 1. Growth of eight selected algal strains cultured in various concentrations of food waste filtrate.

The mean and standard deviation of three replicates are shown.

Fig 2

Growth rate (A) and maximum cell density (B) of eight selected algae in 10% food waste filtrate. The mean and standard deviation of three replicates are shown. Means with different letters for each treatment indicate significant differences at p < 0.05 according to a one-way ANOVA test.

Fig 3. Growth of C. aponinum cultured under various light intensities.

The mean and standard deviation of three replicates are shown.

Fig 4

Growth rate (A) and maximum cell density (B) of C. aponinum cultured under various light intensities. The mean and standard deviation of three replicates are shown. Means with different letters for each treatment indicate significant differences at p < 0.05 according to one-way ANOVA test.

Fig 5. Growth of C. aponinum cultured under various temperatures.

The mean and standard deviation of three replicates are shown.

Fig 6

Growth rate (A) and maximum cell density (B) of C. aponinum cultured under various temperatures. The mean and standard deviation of three replicates are shown. Different letters at each treatment indicate significant differences at p < 0.05 according to a one-way ANOVA test.

Fig 7. Growth of C. aponinum cultured under various CO₂ concentrations.

The mean and standard deviation of three replicates are shown.

Fig 8

Growth rate (A) and maximum cell density (B) of C. aponinum cultured under various CO₂ concentrations. The mean and standard deviation of three replicates are shown. Means with different letters at each treatment indicate significant differences at p < 0.05 according to one-way ANOVA test.

Fig 9. pH of the medium for cultivating C. aponinum under various CO₂ concentrations.

The mean and standard deviation of three replicates are shown.

Fig 10. Nutrient removal efficiency of food waste filtrate treatment by C. aponinum under different CO₂ concentrations.

The mean and standard deviation of three replicates are shown. Means with different letters at each treatment indicate significant differences at p < 0.05 according to a one-way ANOVA test.

Fig 11. Temperature change of culture in both laboratory and on-site pilot environments.

The mean and standard deviation of three replicates are shown.

Fig 12

Maximum growth rate (A) and maximum cell density (B) of C. aponinum in filtered and non-filtered food waste filtrate. The mean and standard deviation of three replicates are shown. Means with different letters at each treatment indicate significant differences at p < 0.05 according to a one-way ANOVA test.