Stefan Diener

Conversion of organic material by black soldier fly larvae: establishing optimal feeding rates:

Larvae of the black soldier fly, Hermetia illucens (Diptera: Stratiomyidae), are voracious feeders of organic material and may thus be used in simple engineered systems to reduce organic waste in low- and middle-income countries. Controlled feeding experiments with standard fodder were conducted to assess the optimum amount of organic waste to be added to a CORS system (Conversion of Organic Refuse by Saprophages). A daily feeding rate of 100 mg chicken feed (60% moisture content) per larva resulted in an optimum trade-off between material reduction efficiency (41.8%, SE 0.61) and biomass production (prepupal dry weight: 48.0 mg, SE 2.0). Applied to market waste and human faeces, this corresponds to a potential daily feeding capacity of 3—5 kg/m2 and 6.5 kg/m2, respectively. In addition, H. illucens prepupae quality was assessed to determine their suitability to substitute fishmeal in animal feed production. The chitin-corrected crude protein content ranged from 28.2 to 42.5%, depending on the amount of food provided to the larvae. Based on our study, a waste processing unit could yield a daily prepupal biomass of 145 g (dry mass) per m2. We conclude that larvae of the black soldier fly are potentially capable of converting large amounts of organic waste into protein-rich biomass to substitute fishmeal, thereby contributing to sustainable aquaculture.

Faecal sludge management with the larvae of the black soldier fly (Hermetia illucens) — From a hygiene aspect

Inadequate and lacking sanitation and wastewater treatment systems can lead to the spreading of diarrhoeal diseases. One contributing factor in the lack of such treatment systems is the lack of economic incentives for stakeholders throughout the service chain. However, the organic fraction of the waste is high in valuable plant nutrients and could be reused in agriculture and as animal feed. For example, grown larvae of the black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae), make an excellent protein source in animal feed, while the feeding activity of the larvae substantially reduces the dry mass of the treated material. This study examined the effect of black soldier fly larvae on the concentration of pathogenic microorganisms in human faeces and found a 6 log10 reduction in Salmonella spp. in human faeces in eight days, compared with a <2 log10 reduction in the control. No increased reduction was observed for Enterococcus spp., bacteriophage ΦX174 or Ascaris suum ova.

Bioaccumulation of heavy metals in the black soldier fly, Hermetia illucens and effects on its life cycle

In developing countries, effective waste management strategies are constrained by high collection costs and lack of adequate treatment and disposal options. The organic fraction in particular, which accounts for more than 50% of the waste production, constitutes a great, yet mostly neglected, reuse potential. Concomitantly, the demand for alternative protein sources by the livestock feed industry is sharply increasing. A technology that effectively transforms organic waste into valuable feed is therefore a timely option. Larvae of the non-pest black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae), may be used to reduce the mass of organic waste significantly. Concurrently, larval feeding converts organic waste into prepupae (last larval stage) which is high in protein. In combination with a viable market, this potential animal feed may cover the waste collection costs and thus promote innovative, small-scale entrepreneurs to establish a profitable business niche. Organic waste, however, often c...

Treatment technologies for urban solid biowaste to create value products: a review with focus on low- and middle-income settings

Treatment of biowaste, the predominant waste fraction in low- and middle-income settings, offers public health, environmental and economic benefits by converting waste into a hygienic product, diverting it from disposal sites, and providing a source of income. This article presents a comprehensive overview of 13 biowaste treatment technologies, grouped into four categories: (1) direct use (direct land application, direct animal feed, direct combustion), (2) biological treatment (composting, vermicomposting, black soldier fly treatment, anaerobic digestion, fermentation), (3) physico-chemical treatment (transesterification, densification), and (4) thermo-chemical treatment (pyrolysis, liquefaction, gasification). Based on a literature review and expert consultation, the main feedstock requirements, process conditions and treatment products are summarized, and the challenges and trends, particularly regarding the applicability of each technology in the urban low- and middle-income context, are critically discussed. An analysis of the scientific articles published from 2005 to 2015 reveals substantial differences in the amount and type of research published for each technology, a fact that can partly be explained with the development stage of the technologies. Overall, publications from case studies and field research seem disproportionately underrepresented for all technologies. One may argue that this reflects the main task of researchers—to conduct fundamental research for enhanced process understanding—but it may also be a result of the traditional embedding of the waste sector in the discipline of engineering science, where socio-economic and management aspects are seldom object of the research. More unbiased, well-structured and reproducible evidence from case studies at scale could foster the knowledge transfer to practitioners and enhance the exchange between academia, policy and practice.