Bio-sludge from the Pulp and Paper Industry as Feed for Black Soldier Fly Larvae: A Study of Critical Factors for Growth
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ORIGINAL PAPER
Bio‑sludge from the Pulp and Paper Industry as Feed for Black Soldier Fly Larvae: A Study of Critical Factors for Growth and Survival R. Norgren1,2 · O. Björkqvist3 · A. Jonsson4 Received: 5 November 2018 / Accepted: 21 October 2019 © The Author(s) 2019
Abstract Pulp and paper bio-sludge (PPBS) has low economic value and is therefore often composted or incinerated. The purpose of this work is to evaluate the feasibility of using PPBS to breed black soldier fly (Hermetia illucens) larvae (BSFL), so improving resource efficiency and supplying protein and fat to the animal feed market. BSFL were reared on PPBS in a climate chamber on a laboratory scale in order to assess nutrient deficiency, inhibition and whether the BSFL recycle the PPBS well or not. The PPBS used came from a chemi-thermomechanical pulp/groundwood pulp mill. The effect of supplementing nutrient solution added either into the PPBS or as a free liquid surface were studied. Prepupae dry weight, survival rate until prepupae stage and residual dry PPBS were measured. The addition of reference diet leachate into the PPBS did not have a significant impact on the weight of the prepupae (2.0 mg) but the survival rate was significantly higher (16.0%). On the other hand, the addition of reference diet leachate as a free liquid surface had a significant impact on both the weight of the prepupae (4.8 mg) and the survival rate (25.7%). The bio-conversion and PPBS—reduction was as best 0.4 and 3.2% respectively. This study has proven that the nutrients in PPBS are not readily available to the larvae. Addition of reference diet leachate increase the survival rate which opens up for possibilities of co-digestion. However, it is clear that under the tested conditions, BSFL is not recycling PPBS well and BSFL as a method for recycling of PPBS need further research. Graphic Abstract
Keywords Pulp and paper bio-sludges · Valorization · Black soldier fly larvae
Statement of Novelty
Introduction
Valorization of pulp & paper bio sludge by Black Soldier fly larvae is a novel approach. Our results show that further research on nutrient availability and co-digestion are needed.
Treating wastewater from the pulp and paper industry produces large quantities of bio-sludge (PPBS). In Sweden alone, the yearly production amounts to 200,000–300,000 tons [1]. The composition of PPBS varies depending on the paper mill process and wastewater treatment, but typically it contains crude protein 1.5–8.3%, fat 0.3–3.3%, 10–30% dry substance (DS), lignin 17–40% DS, nitrogen
* R. Norgren [email protected] Extended author information available on the last page of the article
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18,000–84,000 mg/kg DS, phosphorus 1,700–21,000 mg/ kg DS, potassium 200–4,600 mg/kg DS and ash (27% DS) [2, 3]. It is also frequently contaminated with toxic heavy metals such as lead, mercury and cadmium [2]. Since the concentration of valuable substances is rather low, it has low economic value and is often incinerated or composted [1, 4]. From a resource c
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