Application of microwave radiation for treating source-separated human urine
Noviconoks, Aleksandrs (2025)
2025
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2025061021981
https://urn.fi/URN:NBN:fi:amk-2025061021981
Tiivistelmä
Urine is a nutrient-rich byproduct of the human body containing essential fertilizing nutrients like nitrogen (N), phosphorus (P), and potassium (K). Researchers at SLU lead the work on stabilizing urine and its subsequent conventional dehydration to produce a solid fertilizer. However, the current dehydration method faces limitations due to its heating mechanism, which results in long drying times and high energy consumption.
This study aimed to investigate the effect of microwave radiation on the drying kinetics of acidified urine and the efficiency of the process. Microwave powers of 90W, 180W, 250W, 450W, 700W, and 900W were tested, and concepts such as drying time, moisture ratio, effective diffusivity, activation energy, and mathematical models were assessed.
The microwave drying method achieved mass reduction of 98% and the maximum CF of 53. High drying rates were observed, with a significant decrease in drying time compared to the convection mode: 6-fold at the lowest and 48-fold at the highest microwave power. Moreover, no loss of nitrogen was observed for all the drying experiments with the 100% preserved total available nitrogen. Regarding the mathematical modeling, the Midilli model best described the drying curves of the process with high R2 values (0,990-0,998) and low RMSE values (0,0410 – 0,0309).
The results achieved in this study, particularly the drying rates, indicate the potential of microwave radiation as a substitute for conventional drying methods of acidified urine. This could serve as a starting point for further research on alkalized urine and process scale-up and optimization.
This study aimed to investigate the effect of microwave radiation on the drying kinetics of acidified urine and the efficiency of the process. Microwave powers of 90W, 180W, 250W, 450W, 700W, and 900W were tested, and concepts such as drying time, moisture ratio, effective diffusivity, activation energy, and mathematical models were assessed.
The microwave drying method achieved mass reduction of 98% and the maximum CF of 53. High drying rates were observed, with a significant decrease in drying time compared to the convection mode: 6-fold at the lowest and 48-fold at the highest microwave power. Moreover, no loss of nitrogen was observed for all the drying experiments with the 100% preserved total available nitrogen. Regarding the mathematical modeling, the Midilli model best described the drying curves of the process with high R2 values (0,990-0,998) and low RMSE values (0,0410 – 0,0309).
The results achieved in this study, particularly the drying rates, indicate the potential of microwave radiation as a substitute for conventional drying methods of acidified urine. This could serve as a starting point for further research on alkalized urine and process scale-up and optimization.