BATCH PROCESS OPERATIONAL EFFECTS ON PHOSPHORUS ATTAINMENT IN HYDROCHAR PRODUCED BY HYDROTHERMAL CARBONIZATION OF DAIRY MANURE

As an alternative technology for phosphorus cycling, hydrochar produced from animal manure is a great vehi-cle 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 tradi-tional 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 pro-cessing 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 degrees C to 255 degrees 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 attain-ment 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.