Original article: fermented pulp and paper bio-sludge as feed for black soldier fly larvae

This study evaluates the use of fermentation to increase nutrient availability in pulp and paper bio-sludge (PPBS) as feed for black soldier fly larvae (BSFL). Rearing of BSFL on fermented PPBS was carried out in a climate chamber in order to assess nutrient availability and larvae survival and growth. The PPBS used came from a chemo-thermomechanical pulp/groundwood pulp mill. The PPBS was fermented at 35 degrees C and 55 degrees C, respectively, at initial pH of 10. The effects of sediment and liquid from fermented PPBS on larvae dry weight, survival rate until the prepupae stage, bioconversion, and reduction rate of PPBS were measured. The bioconversion of the liquids (4.1-6.6%) was substantially higher than for both the sediments and untreated PPBS (<= 0.4%). The survival rate, on the other hand, was substantially lower (26.3-30.9 %) than for the sediments and untreated PPBS (49.5-52.6%). Neither the sediments nor the liquids had significant effects on the larvae weight or on the PPBS reduction rate. The sediments had no significant effect on the survival rate or the bioconversion. This study demonstrates that fermentation dissolves a part of the PPBS and that dissolved substances in the fermentation liquid readily convert to larvae biomass. However, the bulk of the lignocellulose is not dissolved, and most of PPBS nutrients remain unavailable for growth of the larvae. Further research should focus on improved pretreatment of PPBS to increase availability of nutrients and thereby improve the feasibility of BSFL as a recycling method for PPBS.

Automated summary

This study evaluates the use of fermentation to increase nutrient availability in pulp and paper bio-sludge (PPBS) as feed for black soldier fly larvae (BSFL). The results show that the bioconversion rate of fermented liquids is higher than that of sediments and untreated PPBS, but the survival rate of larvae is lower. The sediments have no significant effect on larvae weight or PPBS reduction rate. Further research should focus on improving the pretreatment of PPBS to increase nutrient availability and improve the feasibility of using BSFL as a recycling method for PPBS.