Batch Process Operational Effects on Phosphorus Attainment in Hydrochar Produced by Hydrothermal Carbonization of Dairy Manure

Highlights Temperature ramp-up from 180°C to the pre-set processing temperature significantly affects total phosphorus attainment rate. The transition time of temperature ramp-up is crucial in assessing the change of TP attainment rate. Temperature cooling does not show significant effect on total phosphorus attainment rate. Abstract. As an alternative technology for phosphorus cycling, hydrochar produced from animal manure is a great vehicle to attain phosphorus from dairy manure and apply it back to cropland in an environmentally friendly manner. Hydrochar production by hydrothermal carbonization (HTC) greatly reduces the time to manage animal manure compared to traditional lagoon systems. Before being established as a practical technology for hydrochar production in continuous-flow operations, HTC in batch mode is the best way to systematically investigate and optimize the process conditions for high efficiencies. This study investigates specifically the effect of temperature ramp-up rates on the attainment of total phosphorus (TP) in hydrochar produced from dairy manure through batch-mode HTC operations. Experimental results revealed that the transition in temperature ramp-up greatly affected the TP attainment rate in hydrochar, depending on the pre-set processing temperatures and holding time. Statistical analysis confirms that such an effect is significant if the holding time is 30 min or less. This is due not only to the higher processing temperatures but also to the extra 5 to 15 minutes of processing time required for the ramp-up to the pre-set temperatures of 195°C to 255°C, at which point biomass decomposition has already occurred. It is concluded that the temperature ramp-up in batch HTC processes significantly affect the TP attainment rate in hydrochar produced from dairy manure. Before developing continuous-flow HTC systems, it is recommended that experimental results from batch operations be carefully interpreted. Keywords: Batch processes, Dairy manure, Hydrochar, Hydrothermal carbonization, Phosphorus.