Organic Waste Streams Research Articles

Chemical safety of black soldier fly larvae (Hermetia illucens), knowledge gaps and recommendations for future research: a critical review

Black soldier fly larvae (Hermetia illucens) (BSFL) are a promising protein source for the feed industry. They can be used to convert organic waste into valuable biomass, and due to their chemical composition, they are a valuable ingredient for several industrial sectors. To use BSFL as a feed ingredient, their chemical safety must be guaranteed. The composition of their rearing substrate is one of the crucial factors for safety, since it might introduce safety risks by bioaccumulation of various (in)organic compounds (e.g. toxic metals, mycotoxins, pesticides, etc.) in BSFL. Though several organic waste streams are potential and valuable rearing substrates for BSFL, the European Union currently does not allow their use due to safety knowledge gaps. This has prompted researchers to conduct several exposure experiments by artificially spiking chemicals to the rearing substrate of BSFL to investigate such risks. Here, we present a critical overview of the current body of literature on this topic and discuss the main findings, gaps, and recommendations for future research. Overall, BSFL do not seem to accumulate contaminants above the European feed legislation limits, except for certain metals (i.e. cadmium, lead, and zinc), which can jeopardise the chemical safety of the BSFL. For all compounds explored to date, except for cyromazine and pyriproxyfen, their presence in the substrate has no effect on the larval growth or survival rate. However, the remaining knowledge gaps concerning other potential hazardous chemicals (e.g. plasticisers, flame retardants, etc.) and their degradation pathways in BSFL still warrant an appropriate chemical safety assessment and can be a reason why several organic waste streams are not yet allowed to grow BSFL. The risks induced by the potential presence and accumulation of other chemical compounds requires further research to enable the safe exploitation of BSFL.

Characterization of Polyhydroxyalkanoates Produced at Pilot Scale From Different Organic Wastes.

Polyhydroxyalkanoates (PHAs) production at pilot scale has been recently investigated and carried out exploiting different process configurations and organic wastes. More in detail, three pilot platforms, in Treviso (North-East of Italy), Carbonera (North-East of Italy) and Lisbon, produced PHAs by open mixed microbial cultures (MMCs) and different organic waste streams: organic fraction of municipal solid waste and sewage sludge (OFMSW-WAS), cellulosic primary sludge (CPS), and fruit waste (FW), respectively. In this context, two stabilization methods have been applied, and compared, for preserving the amount of PHA inside the cells: thermal drying and wet acidification of the biomass at the end of PHA accumulation process. Afterward, polymer has been extracted following an optimized method based on aqueous-phase inorganic reagents. Several PHA samples were then characterized to determine PHA purity, chemical composition, molecular weight, and thermal properties. The polymer contained two types of monomers, namely 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) at a relative percentage of 92.6–79.8 and 7.4–20.2 w/w, respectively, for Treviso and Lisbon plants. On the other hand, an opposite range was found for 3HB and 3HV monomers of PHA from Carbonera, which is 44.0–13.0 and 56.0–87.0 w/w, respectively. PHA extracted from wet-acidified biomass had generally higher viscosity average molecular weights (Mv) (on average 424.8 ± 20.6 and 224.9 ± 21.9 KDa, respectively, for Treviso and Lisbon) while PHA recovered from thermally stabilized dried biomass had a three-fold lower Mv.

Application of artificial neural networks for predicting the physical composition of municipal solid waste: An assessment of the impact of seasonal variation

Sustainable planning of waste management is contingent on reliable data on waste characteristics and their variation across the seasons owing to the consequential environmental impact of such variation. Traditional waste characterization techniques in most developing countries are time-consuming and expensive; hence the need to address the issue from a modelling approach arises. In modelling the complexity within the system, a paradigm shift from the classical models to the intelligent models has been observed. The application of artificial intelligence models in waste management is gaining traction; however its application in predicting the physical composition of waste is still lacking. This study aims at investigating the optimal combinations of network architecture, training algorithm and activation functions that accurately predict the fraction of physical waste streams from meteorological parameters using artificial neural networks. The city of Johannesburg was used as a case study. Maximum temperature, minimum temperature, wind speed and humidity were used as input variables to predict the percentage composition of organic, paper, plastics and textile waste streams. Several sub-models were stimulated with combination of nine training algorithms and four activation functions in each single hidden layer topology with a range of 1–15 neurons. Performance metrics used to evaluate the accuracy of the system are, root mean square error, mean absolute deviation, mean absolute percentage error and correlation coefficient (R). Optimal architectures in the order of input layer-number of neurons in the hidden layer-output layer for predicting organic, paper, plastics and textile waste were 4-10-1, 4-14-1, 4-5-1 and 4-8-1 with R-values of 0.916, 0.862, 0.834 and 0.826, respectively at the testing phase. The result of the study verifies that waste composition prediction can be done in a single hidden-layer satisfactorily.

Phosphorus Removal from Wastewater: The Potential Use of Biochar and the Key Controlling Factors

In recent years, a large volume of literature has been published regarding the removal of phosphorus (P) from wastewater. Various sorbing materials, such as metal oxides and hydroxides, carbonates and hydroxides of calcium (Ca) and magnesium (Mg), hydrotalcite, activated carbon, anion exchange resins, industrial solid wastes and organic solid wastes, have been suggested for P removal. Many of these sorbents are expensive and/or may cause some environmental problems. In contrast, biochar, as an economical and environmentally friendly sorbing material, has received much attention in recent years and has been used as a novel sorbent for the removal of different organic and inorganic pollutants. Biochar is a type of sustainable carbonaceous material that is produced from the thermal treatment of agricultural organic residues and other organic waste streams under oxygen free conditions. This paper reviews the potential use of biochar and the key controlling factors affecting P removal from wastewater. The ability of biochar to remove P from wastewater depends on its physical and chemical properties. Some of the most important physicochemical properties of biochar (structural characteristics, electrical conductivity (EC), mineral composition, pH, zeta potential, cation exchange capacity (CEC) and anion exchange capacity (AEC)) are affected by the feedstock type as well as temperature of pyrolysis and the P sorption capacity is highly dependent on these properties. The P removal is also affected by the water matrix chemistry, such as the presence of competing ions and bulk pH conditions. Finally, several recommendations for future research have been proposed to facilitate and enhance the environmental efficiency of biochar application.

Nitrogen Recovery via Aquaponics–Bioponics: Engineering Considerations and Perspectives

Nitrogen, a critically important nutrient that boosts yields in agriculture and food production, is currently overused to meet the rising demand for food. Surplus nitrogen ends up in the environment in excess of the capacity of natural nitrogen cycle, thereby leading to serious environmental pollutions, such as eutrophication of water bodies and emission of nitrous oxide (a highly potent greenhouse gas) to atmosphere. Aquaponics–bioponics is an emerging soilless technology for nitrogen recovery that links organic vegetable production to aquaculture effluent remediation (aquaponics) or organic waste recycling (bioponics). This Review presents the concept of aquaponics–bioponics for nitrogen recovery. Nitrogen transformations and nitrogen mass distributions in aquaponic–bioponic systems are critically discussed, along with the nutrient availability of several organic composts that can be integrated with the systems, and the microbial communities involved. This discussion is followed by a dynamic nitrogen modeling for managing nitrogen from different wastes in aquaponics–bioponics. Various emerging engineering technologies that could improve aquaponics–bioponics are presented, including aeration with microbubbles and/or nanobubbles, cocultivation with algae, process automation with Internet of Things, and integration with indoor vertical farming (plant factory with artificial light). Overall, the Review lays out the state-of-art in aquaponics–bioponics and highlights potential approaches for developing highly efficient nitrogen recovery technologies from diverse organic waste streams.

On the Applicability of a Precursor Derived from Organic Waste Streams for Bacteria-Based Self-Healing Concrete

Bacteria-based self-healing concrete has the ability to heal cracks due to the bacterial conversion of incorporated organic compounds into calcium carbonate. Precipitates seal the cracks, theoretically increasing the service life of constructions. The aim of this paper is to propose a precursor for bacteria-based self-healing concrete derived from organic waste streams, produced is in line with the circular economy principle and ideally more affordable than other substrates. To verify the applicability of the proposed healing agent, some fundamental requirements of the proposed system are studied, such as its influence on functional properties, crack sealing capacity and evidence of bacterial activity in concrete.

Substrate availability drives mixed culture fermentation of glucose to lactate at steady state.

Mixed-culture fermentation (MCF) enables carbon recycling from complex organic waste streams into valuable feedstock chemicals. Using complex microbial consortia, MCF systems can be tuned to produce a range of biochemicals to meet market demand. However, the metabolic mechanisms and community interactions which drive biochemical production changes under differing conditions are currently poorly understood. These mechanisms are critical to useful MCF production models. Furthermore, predictable product transitions are currently limited to pH-driven changes between butyrate and ethanol, and chain-elongation (fed by lactate, acetate, and ethanol) to butyrate, valerate, and hexanoate. Lactate, a high-value biopolymer feedstock chemical, has been observed in transition states, but sustained production has not been described. In this study, steady state lactate production was achieved by increasing the organic loading rate of a butyrate-producing system from limiting to nonlimiting conditions at pH 5.5. Crucially, butyrate production resumed upon return to substrate-limited conditions. 16S ribosomal DNA community profiling combined with metaproteomics demonstrated that the butyrate-producing lineage Megasphaera redirected carbon flow through the methylglyoxal bypass when substrate was nonlimiting, which altered the community structure and metabolic expression toward lactate production. This metabolic mechanism can be included in future MCF models to describe the changes in product generation in substrate nonlimiting conditions.

O-aryl and Carbonyl Carbon Contents of Food Waste and Biosolid Predict P Availability in an Acidic Soil

Organic waste streams, otherwise known as organic amendments (OA), contain potentially valuable nutrients which may additionally increase legacy nutrient availability in soil. This is particularly the case for phosphorus (P) where declining reserves of rock phosphate add an extra dimension to their utility. In acidic soils, OA have been reported to increase P availability through the action of O-aryl and carbonyl groups (represent organic acid compounds) by substituting previously fixed, legacy P and forming organometallic complexes to reduce P sorption. This study aimed to investigate if signature P (orthophosphate) and C (O-aryl and carbonyl) content of OA could be used to predict soil P availability, to replace traditional ways of testing OA and also for future prescriptive applications. Food waste and biosolid were the sources of OA in this study, with pyrolysis and composting processes used to create a range of functional groups. Nuclear magnetic resonance (NMR) spectroscopy was utilized to identify forms of C (solid-state 13C NMR) and P compounds (solution-state 31P NMR) in these OA. The O-aryl, carbonyl, and orthophosphate content were higher in pyrolysis and composted materials compared to their feedstock substrate. The effect of OA addition on soil P availability was monitored in a 110-day laboratory incubation study. Results showed an increase in soil P availability (Olsen P) and a decrease in soil P buffering capacity (PBC) after incubation. The increase in soil P availability was not predicted well by the NMR-derived orthophosphate content of OA, which may be due to the overestimation of plant-available orthophosphate content by the solution-state 31P NMR. Furthermore, an additional increase in soil ΔOlsen P (difference between observed and expected) was obtained above the Olsen P added from OA indicating substitution of previously fixed soil P. Both indices of P availability namely ΔOlsen P (r = 0.63–0.83) and ΔPBC (difference between treatment—control) (r = −0.50 to −0.80) showed strong (but opposite) correlations with the ratio of O-aryl to carbonyl C content of OA. It was concluded that the ratio of O-aryl and carbonyl C content of OA could be used to predict the P availability in acidic soil.

A review paper on aerobic and anaerobic biodegradation

Biodegradation, whether aerobic or anaerobic, is a method for cleaving large molecules from a mosaic of chemicals and materials in a series of steps, with some of the smaller molecules being valorized as a pollution abatement strategy and a source of energy through biogas generation. Biogas may be made from virtually any kind of biomass, including main agricultural sectors and different organic waste streams, which can be used as a sustainable energy source. Animal dung that has not been properly handled or managed is a significant cause of pollution in the air and water. Some of the most serious concerns include nutrient leakage, particularly of nitrogen and phosphorus, as well as ammonia evaporation and microbial contamination. the animal manufacturing is responsible for 18 percent of total CO2 equivalent emissions and 37 percent of atmospheric methane, which has 23 times the global temperature potential of CO2. Furthermore, the global animal production sector is responsible for 65 percent of human activity nitrous oxide and 64 percent of anthropogenic ammonia emissions.

Biogas Production Systems and Upgrading Technologies: A Review.

SUMMARYThe underutilized biomass and different organic waste streams are nowadays in the focus of research for renewable energy production due to the effusive use of fossil fuels and greenhouse gas emission. In addition, one of the major environmental problems is also a constant increase of the number of organic waste streams. In a lot of countries, sustainable waste management, including waste prevention and reduction, has become a priority as a means to reduce pollution and greenhouse gas emission. Application of biogas technology is one of the promising methods to provide solutions for both actual energy-related and environmental problems. This review aims to present conventional and novel biogas production systems, as well as purification and upgrading technologies, nowadays applicable on a large scale, with a special focus on the CO2 and H2S removal. It also gives an overview of feedstock and the parameters important for biogas production, together with digestate utilization and application of molecular biology in order to improve the biogas production.

The Current Status, Potential Benefits and Future Prospects of the Australian Biogas Sector

Anaerobic digestion technology provides a new approach to treat organic waste while generating greenhouse gas (GHG) savings. Moreover, the methane gas produced during the process can be used to generate electricity. In order to ensure that Australia stays on its trajectory towards a carbon neutral future, the use of anaerobic digestion technology to treat its abundant organic waste streams should be considered. Thirty million tonnes (Mt) of organic waste was produced in 2017. The use of anaerobic digestion to treat 1 tonne of waste could result in 0.143 tonne of CO2-e in GHG savings. In contrast, other more widely employed waste disposal methods such as landfilling, composting and incineration may generate GHG emissions. Additionally, the use of methane for electricity production also generates the least GHG emissions per MWh. This is approximately 3 times lower than crude oil, 4 times lower than black coal and 5 times lower than brown coal. However, the adoption and implementation of anaerobic digestion technology in Australia face several immediate constraints. Firstly, anaerobic digestion technology is deemed unprofitable, incurring high initial capital cost, operating costs and extremely long payback periods. Secondly, there is a lack of government support in terms of a national target for biogas production via anaerobic digestion. This review will provide an in-depth analysis into the current state of the Australian biogas sector. In addition, the review discusses the opportunities to make anaerobic digestion technology more financially viable and to accelerate the growth of the Australian biogas sector.

Fermentation of Organic Residues to Beneficial Chemicals: A Review of Medium-Chain Fatty Acid Production

Medium-chain fatty acids (MCFAs) have a variety of uses in the production of industrial chemicals, food, and personal care products. These compounds are often produced through palm refining, but recent work has demonstrated that MCFAs can also be produced through the fermentation of complex organic substrates, including organic waste streams. While “chain elongation” offers a renewable platform for producing MCFAs, there are several limitations that need to be addressed before full-scale implementation becomes widespread. Here, we review the history of work on MCFA production by both pure and mixed cultures of fermenting organisms, and the unique metabolic features that lead to MCFA production. We also offer approaches to address the remaining challenges and increase MCFA production from renewable feedstocks.

Use of black soldier fly and house fly in feed to promote sustainable poultry production

The growing human population, changing dietary habits and intensifying competition between food and feed production underline the urgent need to explore novel sustainable production chains. In the past, the poultry sector has gained popularity due to its superior environmental and economic benefits compared to other livestock production systems. Therefore, it is of special interest to focus on refinement and innovation along the value chain to further improve the sector’s sustainability. One major issue is the transition towards sustainable protein sources in poultry feed. In this regard, insects are the secret rising stars. Insect species such as the black soldier fly (Hermetia illucens) and house fly (Musca domestica) have been proposed for farming as multifunctional mini-livestock for feed. One major property of these flies is that larvae can convert low-quality organic waste streams into valuable body mass containing high levels of high-quality protein and fat. Furthermore, the larvae are reported to have health- and welfare-promoting effects due to bioactive compounds and poultry having a natural interest in them. The aim of the current paper is to discuss the state-of-the-art of using black soldier fly and house fly larvae as components of poultry feed and to highlight knowledge gaps, future opportunities and challenges. Some first studies have focussed on the successful partial replacement of soybean meal or fishmeal by these insects on poultry performance. However, since the sector is still in its infancy several uncertainties remain to be addressed. More research is required on identifying optimal inclusion levels, clearly differentiating between insect products based on their nutritional value and health-stimulating effects, and comparing the potential of insect products across species.

Rearing substrate impacts growth and macronutrient composition of Hermetia illucens (L.) (Diptera: Stratiomyidae) larvae produced at an industrial scale

Organic waste is a rapidly increasing problem due to the growth of the agricultural production needed to meet global food demands. Development of sustainable waste management solutions is essential. Black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae) (BSF), larvae are voracious consumers of a wide range of organic materials ranging from fruits and vegetables to animal remains, and manure. Thanks to this ability and considering the larval high protein and lipid content, BSF larvae are a useful additive in animal feeds and biodiesel production. Unfortunately, the feasibility of using the black soldier fly as a tool for waste valorization and feed production has primarily been investigated at the benchtop scale. Thus, mobilization of current practices to an industrial scale is challenging because scaling up from small laboratory studies to large industrial studies is not necessarily linear. The goal of this study was to demonstrate the ability of the BSF to recycle organic waste at an industrial scale. To accomplish this goal, three organic waste streams were used (e.g., apples, bananas, and spent grain from a brewery) to test six diet treatments (1) apple, (2) banana, (3) spent grain, (4) apple and banana, (5) apple and spent grain, and (6) banana and spent grain. Working at scale of 10,000 BSF larvae life history traits, waste valorization, protein and lipid profiles were measured for each diet treatment. Differences were recorded across all variables, except substrate conversion, for larvae fed on fruit and spent grain (alone or with fruit). Growth rate significantly differed across treatments; larvae reared on spent grain grew twice as fast as those fed apples alone, but those reared on the apple and spent grain mixture produced twice as much insect biomass. However, it should be noted that larvae resulting from the apple diet contained 50% more fat than larvae fed the fruit and spent grain mixtures. Commonly-available organic wastes were successfully used at an industrial scale to produce BSF larvae that have the potential to substitute other sources of protein and lipids in different industrial applications. Industrialization efforts are encouraged to assess these impacts when integrating diverse ingredients into larval diets as a means to more precisely predict output, such as larval development time and final larval biomass.

Glycine-acyl Surfactants Prepared from Black Soldier Fly Fat, Coconut Oil and Palm Kernel Oil

: Black soldier fly (Hermetia illucens) larvae are a new source of high-quality bio-based materials that can be implemented for technical applications. Black soldier fly larvae can be bred in high numbers in small areas and organic waste streams, making large scale industrial breeding possible. Fats from the black soldier fly are very rich in lauric acid, and the fatty acid profile resembles that of palm kernel and coconut oil. Therefore, black soldier fly fats could be envisaged to have similar applications to these plant-derived oils. : The aims of this work were (1) to use black soldier fly fat, palm kernel and coconut oil to synthesize a glycine-acyl surfactant by means of a Schotten-Baumann reaction; (2) to determine the yield and purity of the reaction products; and (3) to determine solubility, foaming capacity, surface tension and critical micelle concentration of the surfactants in comparison to a commercially-available glycinecoconut oil surfactant, Amilite GCS-11®. : The aims of this work were (1) to use black soldier fly fat, palm kernel and coconut oil to synthesize a glycine-acyl surfactant by means of a Schotten-Baumann reaction; (2) to determine the yield and purity of the reaction products; and (3) to determine solubility, foaming capacity, surface tension and critical micelle concentration of the surfactants in comparison to a commercially-available glycinecoconut oil surfactant, Amilite GCS-11®. : It is concluded that black soldier fly fats are a suitable alternative to coconut or palm kernel oil for the preparation of glycine-acyl surfactants.

Anaerobic Co-Digestion of Kitchen Waste and Blackwater for Different Practical Application Scenarios in Decentralized Scale: From Wastes to Energy Recovery

This study was performed to investigate the anaerobic digestion feasibility of kitchen waste and blackwater under different scenarios in laboratory tests. According to biochemical methane potential tests, when the kitchen waste to blackwater solid ratio was 1:1, the cumulative methane production reached the highest amount at 313.2 mL/g volatile solids (VSs), which was 26.4% and 29.4% higher than the anaerobic monodigestion of kitchen waste and blackwater, respectively, indicating that the anaerobic codigestion of kitchen waste and blackwater had a synergetic effect. Furthermore, the effect of different initial total ammonia nitrogen concentrations in blackwater on anaerobic digestion was determined based on the above experimental results, thereby proving that reducing the total ammonia nitrogen concentration in blackwater can appropriately improve the efficiency of methane production. Therefore, anaerobic digestion is a suitable method for the biogas production of kitchen waste and blackwater. It is of great significance for the organic waste stream treatment of households in a decentralized scale, especially in rural areas.

Potential of windrow food and green waste composting in Tunisia.

Solid waste management and disposal is one of the most significant challenges facing urban communities around the world. There is a wide range of alternative waste management options and strategies available for dealing with the notable increase in the waste stream. Composting is one of the most viable and efficient waste treatment options in terms of the reduction in the negative effects from the application of organic waste to soil. The experimental research aimed to examine the potential of producing compost from different organic waste streams in Tunisia. Two experimental windrow piles made from cooked and uncooked food and garden wastes were initiated and temporally monitored. The composting process was controlled in terms of temperature and moisture. Sampling was carried out over the period of the composting process. All of the collected samples were analyzed in terms of their physical, chemical, and biological properties; pH, C:N ratio, nitrification index (NI), microbiological tests, respiration activity (AT4), and heavy metal content. The quality of the final product was determined and compared with Tunisian and German standards. The findings demonstrated a significant reduction in the initial C:N ratio to about 15 by the end of the process. Additionally, the results showed that the compost produced appeared to be stable and was deemed to be class V finished compost; the NI was found to be around 1, while the AT4 was estimated to be lower than 6mg O2/g TS. Regarding the heavy metal content, the final products were characterized as having a lower concentration than those values set by Tunisian and German standards.

Designing Circular Waste Management Strategies: The Case of Organic Waste in Amsterdam

AbstractUrban waste management is one of the most complex and urgent challenges that the society faces. In this paper, an innovative research methodology is proposed, introducing a systemic approach to circular waste management strategy‐making. Urban waste management is a complex system that needs to be tackled in a holistic, yet context‐specific manner. To produce truly integrative outcomes, this paper provides insight into the system as a whole, its components and the relationships between them, using specific tools, to form the basis for a circular strategy. A toolbox is presented for transforming the current linear and fragmented waste management processes into integrative and circular strategies. The proposed integrative methodology encompassing outline, multipillar mapping, and synthesis can be applied to different locations and waste streams. The concept is subsequently demonstrated through a case study focusing on the municipality of Amsterdam (the Netherlands) and the management of organic waste streams.

Black soldier fly larvae show a stronger preference for manure than for a mass‐rearing diet

AbstractThe attention for black soldier fly larvae (BSFL) as an alternative ingredient for food and feed products is on the rise. While many studies have reported the efficiency of BSFL to bio‐convert a wide range of organic waste streams into larval biomass, so far, it is unknown whether BSFL prefer certain waste streams over others when they have the possibility to choose. Here, we performed a choice‐test experiment to explore the preference of BSFL when exposed to pig manure and a mass‐rearing diet consisting of plant by‐products currently used for industrial BSFL production. We found that after 1 hr of exposure to both feeds, BSFL strongly preferred pig manure over the mass‐rearing diet. The preference for manure became stronger as larval age increased. Our results provide the first evidence that BSFL express a distinct diet preference. Understanding the reasons for the strong preference for manure is relevant for a diverse array of practical applications and to inform the discussion on insect welfare.

Governing the circular economy: Assessing the capacity to implement resource-oriented sanitation and waste management systems in low- and middle-income countries

Transitioning to a circular economy requires strategic investments in infrastructure, but it also requires policy coherence, coordination and collaboration among stakeholders across sectors and governance levels. In this paper, we aimed to identify the factors that facilitate or impede governance capacity to adopt circularity in the form of resource recovery from urban organic waste streams. We conducted a literature review and semi-structured interviews using the ‘Governance Capacity Framework’ in a case study of Naivasha, Kenya. Our findings emphasize the importance of leadership from the public sector in co-developing visionary strategies for circularity and using their convening power to facilitate cross-sectoral collaboration. Moreover, we identify a need for bridging theoretical circular economy concepts to initiatives in local communities of practice. The insights in this paper are relevant for advancing the understanding of challenges for governance of the circular economy especially in low-and middle-income country contexts.