In this study, we prepared calcium (Ca)-enriched biochar from digested sludge derived from food waste at pyrolysis temperatures in the range of 600 to 900 °C. We evaluated the properties of phosphorus (P) recovery of the biochar and the fertilizer properties of the biochar after the P recovery (P-loaded biochar). The results showed that the amount of P recovery increased with increasing pyrolysis temperature, while the P recovery capacity of biochar was consistently high at all the investigated temperatures. The fertilizer properties of P-loaded Caenriched biochar prepared at 600 °C, evaluated by the komatsuna cultivation test were comparable to the chemical fertilizer Ca(H2PO4)2. The results suggest that the Ca-enriched biochar could serve as a P recovery material and an environmentally friendly fertilizer.
The utilization of corn residues as a potential biomass for thermochemical conversion was investigated. The general objective of the study was to design and develop a thermochemical conversion unit and evaluate its performance in terms of the production of bio-oil, bio-char and syngas. The developed thermochemical conversion unit comprises a hopper, modified worm drive, reactor, cyclones separator, and syngas condenser. Three kilograms of size-reduced corn cobs were loaded to the reactor, then subjected to thermochemical conversion varying the operating temperature (with and without heater) and three airflow rates. Results showed that the highest percentages of biochar, bio-oil and syngas collected using the developed machine were 24%, 37% and 59%. Biochar contained 34% of volatile combustible matter, 60% of fixed carbon and a heating value of 26.3 MJ/kg. The thermochemical conversion unit has a waste to energy conversion efficiency that could reach as high as 91%. To achieve the highest percent recoveries of bio-oil and syngas, the machine should be operated at an airflow of 84 L/s. On the other hand, to obtain the highest recovery of bio-char, the unit should be operated at lower airflow. The conduct of up-scaling of the developed thermochemical conversion unit, testing and evaluation under field condition, and perform financial analysis are recommended.