Utilization of solar energy in sewage sludge composting: Fertilizer effect and application

•Solar energy technologies were utilized in aerobic sewage sludge composting.•Greenhouse and solar reactors were constructed to compare impacts on the composting.•Impatiens balsamina was planted in pot experiments to evaluate fertilizer effect. Three reactors, ordinary, greenhouse, and solar, were constructed and tested to compare their impacts on the composting of municipal sewage sludge. Greenhouse and solar reactors were designed to evaluate the use of solar energy in sludge composting, including their effects on temperature and compost quality. After 40days of composting, it was found that the solar reactor could provide more stable heat for the composting process. The average temperature of the solar reactor was higher than that of the other two systems, and only the solar reactor could maintain the temperature above 55°C for more than 3days. Composting with the solar reactor resulted in 31.3% decrease in the total organic carbon, increased the germination index to 91%, decreased the total nitrogen loss, and produced a good effect on pot experiments.