Subcritical hydrothermal treatment for the recovery of liquid fertilizer from scallop entrails

Abstract

Scallop entrails are organic wastes containing abundant proteins and minerals but are considered difficult to recycle because of high cadmium concentrations. In this work, the current problem of scallop entrails recycling was investigated and a subcritical hydrothermal treatment (SCHT) was examined for the recovery of liquid fertilizer from scallop entrails. Scallop entrails are mainly recycled for composting and feedstuff production. However, the dilution by mixing scallop entrails with other feed waste was the sole countermeasure to reduce the cadmium concentration of compost. For feedstuff production, whole product derived from scallop entrails was exported to other countries instead of domestic utilization. Temperature, retention time (RT) at given temperature, and liquid-to-solid (LS) ratio were examined as SCHT conditions for scallop entrails processing. The extraction ratio of each constituent mainly depends on the temperature rather than the RT or the LS ratio. Upon the SCHT of scallop entrails at 200°C, an RT of 20 min, and an LS ratio of 10, the extraction of fertilizer constituents such as nitrogen, phosphorus, and potassium from the liquid product was optimum, whereas the release of cadmium was suppressed. The concentrations of heavy metals in the liquid product obtained using the above-mentioned SCHT conditions were below the maximum permissible concentration stipulated by the Fertilizer Control Law. SCHT is considered to be a feasible recycling method for scallop entrails to recover fertilizer components with a concomitant separation of cadmium from the product.

EVALUACIÓN DE FITOTOXICIDAD Y CARACTERIZACIÓN DE UN FERTILIZANTE LÍQUIDO ELABORADO MEDIANTE FERMENTACIÓN LÁCTICA UTILIZANDO SUBPRODUCTOS DEL PROCESAMIENTO DE TRUCHA (Oncorhynchus mykiss)

“…Además de la MO, los residuos fermentados de pescado contienen cantidades apreciables de nutrientes como N, P, K, Ca y Mg, que puedan ser aprovechadas por las plantas (Hepsibha & Geetha, 2019). Respecto al contenido de macronutrientes, Hwang et al (2015) señalan que las concentraciones de N, P y K de los FL comerciales tienen valores de 1 000 a 2 000 mg/l. En la Tabla 2 se observa que el contenido de N, P y K del FLVT fue de 12 040 mg/l, 1 189.95 mg/l, 5 540 mg/l, respectivamente.…”

“…De tal forma que las vísceras constituyen de 5 a 8% del peso del pescado entero (Waterman, 2001). Por otro lado, el reciclaje de residuos orgánicos es importante para la recuperación de nutrientes y compuestos orgánicos de la biomasa no utilizada de los diferentes recursos, evitando la generación de gases de efecto invernadero cuando estos residuos se entierran, arrojan a ríos o se colocan en rellenos sanitarios (Hwang et al, 2015).…”