Food industry waste - An opportunity for black soldier fly larvae protein production in Tanzania.

Black soldier fly larvae composting is an emerging treatment option with potential to improve biowaste valorization in cities of low-income countries. This study surveyed the current generation and management status of food industry biowaste and their availability and suitability as potential feedstock for black soldier fly larvae (BSFL) composting treatment in three Tanzania cities, Dar es Salaam, Mwanza, and Dodoma. Biowaste-generating food industry companies (n = 29) in the three cities were found to produce banana peels, mango seeds, sunflower press cake, brewery waste, and coffee husks in large quantities (~100,000-1,000,000 kg y-1). Around 50 % of these companies (16/29), primarily vegetable oil companies (10/11), either sold or gave away their waste as animal feed, while most companies (9/11) with unutilized food industry waste landfilled the generated biowaste. Multi-criteria analysis based on substrate availability criteria identified banana peels, mango seeds, and coffee husks with total score points of ≥10/12 as the most suitable feedstock for BSFL composting. However, multi-criteria analysis based on physical-chemical criteria identified brewery waste and sunflower press cake with total score points of ≥11/15 as the most suitable feedstock. Combined availability and physical-chemical properties of individual biowastes showed that all identified types of food industry biowaste can be suitable feedstock for producing BSFL biomass for protein production, but certain waste streams needed to be mixed with other waste streams prior to BSFL-composting to ensure sufficient availability and provide a balanced nutritional profile compared with the single-source biowastes. This study concluded that large volumes of food industry waste are being generated from food industry companies in Tanzania and there is need to establish new biowaste management interventions for resource recovery. Furthermore, for interested stakeholders in the waste management business, multi-stream BSFL-composting can be a suitable solution for managing and closing nutrient loops of the unutilized food industry biowaste in Tanzania and in other similar settings globally.

Process efficiency in relation to enzyme pre-treatment duration in black soldier fly larvae composting.

Black soldier fly larvae (BSFL) composting is a treatment in which biodegradable food waste is converted into animal-feed protein and organic fertiliser. BSFL composting has greatest potential for mixed food waste, but under European Union regulations only plant-based waste is permitted as feed for larvae. Biomass conversion efficiency (BCE) in BSFL composting is lower for plant-based waste than for mixed food waste. One way of improving BCE for plant-based waste is to add enzymes to make the waste more available to the larvae, but enzyme pre-treatment is not commonly applied prior to BSFL composting. Therefore this study examined the impact of enzyme pre-treatment duration on process efficiency in BSFL composting of lettuce-cabbage waste pre-treated with enzymes for 0-4 days. The results showed that total solids (TS) in larvae decreased with longer enzyme pre-treatment. Direct addition of enzymes at the start of BSFL treatment (0 day pre-treatment) resulted in 22% higher BCE on a volatile solids (VS) basis compared with the control, while longer pre-treatment did not improve BCE further. Much of the VS was respired in the 0-day pre-treatment, resulting in lower mass of residues at the end of treatment. Longer pre-treatment increased microbial respiration, suggesting that the microbial community consumed more easily available carbohydrates during the pre-treatment step, which counteracted the purpose of enzyme pre-treatment, i.e. increasing BCE during BSFL composting.

Pre-treatment of banana peel to improve composting by black soldier fly (Hermetia illucens (L.), Diptera: Stratiomyidae) larvae.

Use of black soldier fly (Hermetia illucens (L.), Diptera: Stratiomyidae) larvae (BSFL) is among the solutions being explored to shift the value chain in organic waste management by producing valuable products. Although BSFL consume a range of substrates, nutrient-imbalanced materials with high hemicellulose and lignin content, e.g. manure and banana peel, yield low conversion into larval biomass. This study explored pre-treatment methods to improve the nutrient composition and digestibility of banana peel to achieve higher substrate conversion into BSFL biomass. The pre-treatment methods evaluated were microbial, chemical (non-protein nitrogen), heat-based, and combinations of these. All pre-treatments tested except heating resulted in more efficient BSFL conversion in terms of final larvae weight. The low BSFL responses in pre-treatments were caused by the observed high amounts of tannins and phenolic compounds mainly from the heating pre-treatment. Waste to biomass conversion ratio correlated negatively with substrate volatile solids (VS) and positively with the decrease in VS in pre-treatment. Microbial - 14 days pre-treatments provided the optimum pre-treatment time for the microorganisms to achieve maximum degradation of the substrates, facilitating larval assimilation of the released nutrients. Rhizopus oligosporus-14 days and ammonia + Rhizopus resulted in the most efficient BSFL treatment, measured as protein produced per kg incoming material.

Greenhouse gas emissions from small-scale fly larvae composting with Hermetia illucens.

Fly larvae composting is an emerging waste treatment alternative with great potential to increase revenue from food waste management. For wider implementation, fly larvae composting has to be evaluated in comparison with conventional systems, based on direct greenhouse gas (GHG) emission data for the treatment process, which are currently limited. This study evaluated direct emissions of CO2, CH4, N2O and NH3 from composting of food waste using black soldier fly (BSF) larvae (Hermetia illucens). Use of BSF larvae-associated bacteria in 7-day pre-treatment and seeding at larvae treatment start were evaluated and compared to larvae treatment without bacteria addition. The treatments were performed in a set of 14-day laboratory-scale experiments. Mean substrate reduction was 49 ±â€¯8% and bioconversion ratio was 24 ±â€¯8% (both dry matter basis). Direct GHG emissions from the fly larvae treatment process were generally very small, with emissions of CH4 and N2O equivalent to 0.38 kg CO2-equivalents per ton food waste treated assuming global warming potential over 100 years, while mean total CO2 emissions were 96 g CO2 per kg food waste treated. Additional emissions could be expected to occur in the pre-treatment process, which did not provide any significant improvement in bioconversion ratio or reduction in total GHG emissions during treatment. Similarly, use of BSF larvae-associated bacteria did not significantly improve process efficiency. No NH3 emissions were detected, as reflected in total N mass balance over the treatment cycle. The results show that total direct GHG emissions from food waste treatment by fly larvae composting are lower than those from conventional food waste treatment, and that pre-treatment and seeding of food waste with BSF larvae-associated bacteria do not further reduce total GHG emissions.

Quality of greywater treated in biochar filter and risk assessment of gastroenteritis due to household exposure during maintenance and irrigation.

AIM: This study evaluated treatment of greywater (GW) by a biochar filter in Jordan and assessed the annual risks of infection (Pi-annual ), annual risk of disease (Pd-annual ) and disease burden (in disability-adjusted life years; DALYs) of gastroenteritis caused by Salmonella spp. and rotavirus due to ingestion of GW during system maintenance and consumption of green onions irrigated with treated and nontreated GW. METHODS AND RESULTS: The biochar filter efficiently removed 93% of biochemical oxygen demand (BOD5 ) and 85% of solids, while removal of Escherichia coli was insignificant. Treatment of GW decreased the median Pd-annual due to ingestion of GW from 1·39 × 10-2 to 6·0 × 10-3 for Salmonella spp. but did not affect Pd-annual caused by rotavirus (9·73 × 10-1 to 1·0). Consumption of onions irrigated with treated GW had a median Pd-annual of 1·25 × 10-9 to 1·2 × 10-8 for Salmonella spp. and 4·96 × 10-4 to 4·37 × 10-3 for rotavirus infection, which was 99·9 and 90% lower, respectively, than the risk when consuming onions irrigated with nontreated GW. The highest risks of gastrointestinal disease were thus associated mainly with direct ingestion of GW when maintaining the system. CONCLUSIONS: Garden produce irrigated with GW treated in biochar filter did not display intolerable risks of rotavirus-based gastroenteritis during summer season in the study area given that the produce is harvested 1 to 2 days, and washed, before consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: This study contributes to scientific-based knowledge on the suitability of biochar filters for onsite greywater treatment and confirms the microbial safety of recycling treated greywater for garden irrigation.

Fate of pharmaceuticals and pesticides in fly larvae composting.

A novel and efficient organic waste management strategy currently gaining great attention is fly larvae composting. High resource recovery efficiency can be achieved in this closed-looped system, but pharmaceuticals and pesticides in waste could potentially accumulate in every loop of the treatment system and spread to the environment. This study evaluated the fate of three pharmaceuticals (carbamazepine, roxithromycin, trimethoprim) and two pesticides (azoxystrobin, propiconazole) in a fly larvae composting system and in a control treatment with no larvae. It was found that the half-life of all five substances was shorter in the fly larvae compost (<10% of control) and no bioaccumulation was detected in the larvae. Fly larvae composting could thus impede the spread of pharmaceuticals and pesticides into the environment.