Mixed Organic Waste Research Articles

European Green Deal: Justification of the Relationships between the Functional Indicators of Bioenergy Production Systems Using Organic Residential Waste Based on the Analysis of the State of Theory and Practice

Based on the analysis conducted on the state of theory and practice, the expediency of assessing the relationships between the functional indicators of bioenergy production systems using the organic waste of residential areas is substantiated in the projects of the European Green Deal. It is based on the use of existing results published in scientific works, as well as on the use of methods of system analysis and mathematical modeling. The proposed approach avoids limitations associated with the one-sidedness of sources or subjectivity of data and also ensures complete consideration of various factors affecting the functional indicators of the bioenergy production system from the organic waste of residential areas. Four types of organic waste generated within the territory of residential areas are considered. In our work, we used passive experimental methods to collect data on the functional characteristics of bioenergy production systems, mathematical statistics methods to process and interpret trends in the functional characteristics of bioenergy production systems using municipal organic waste, and mathematical modeling methods to develop mathematical models that reflect the patterns of change in the functional characteristics of bioenergy production systems. The results indicate the presence of dependencies with close correlations. The resulting dependencies can be used to optimize processes and increase the efficiency of bioenergy production. It was found that: (1) yard waste has the highest volume of the total volume of solid organic substances but has a low yield of biogas and low share of methane production; (2) food waste has the highest yield of biogas and, accordingly, the highest share of methane production; (3) mixed organic waste has the lowest volume of the total volume of solid organic substances and the lowest content of volatile organic substances. The amount of electricity and thermal energy production varies by type of organic waste, with mixed organic waste having a higher average amount of electricity production compared to other types of waste. It was established that the production volume of the solid fraction (biofertilizer) is also different for different types of organic waste. Less solid fraction is produced from food waste than from yard waste. The obtained research results are of practical importance for the development of sustainable bioenergy production from organic waste in residential areas during the implementation of the European Green Deal projects. They provide further research on the development of effective models for determining the rational configuration of bioenergy production systems using organic waste for given characteristics of residential areas.

The liquid by-product of biogas production: characterisation and impact on soil fungi

ABSTRACT A liquid digestate (LD) obtained from the anaerobic digestion of mixed organic waste was characterised and tested on the fungi Pleurotus eryngii, Irpex lacteus and Trametes versicolor. Aqueous mixtures of LD at doses of 0.5, 1 and 2% (v/v) were tested directly or after interaction with 5% (w/v) biochar (BC-LD) and/or 100 mg L−1 soil humic acid (HA-BC-LD and HA-LD). Total luminescence (TL) analysis of LD showed the presence of fluorophores typical of scarcely aromatic matter, while the Fourier transform infrared (FTIR) spectrum evidenced absorption bands typical of labile and non-condensed material. Some spectroscopic variations of the LD sample were observed after its interaction with the other materials. All LD treatments markedly promoted hyphal extension of P. eryngii whose growth rate increased up to 38% at the highest LD dose. The LD alone had no influence on the other fungi, whose growth was stimulated by some combinations of LD with the other materials. In facts, the growth rate of I. lacteus increased in BC-LD 1 and BC-LD 2 (P ≤ 0.05) and in all treatments with HA (up to 6% in HA-LD 2, P ≤ 0.01), while the growth of T. versicolor was promoted by HA-BC-LD 2 treatment (P ≤ 0.05) and slightly inhibited by all BC-LD combinations (up to 7% by BC-LD 1, P ≤ 0.05). The overall results obtained encourage the addition of LD to the soil and suggest a possible use of this material as substrate ingredient for the cultivation of edible mushrooms such as P. eryngii.

Comprehensive Analysis and Greenhouse Gas Reduction Assessment of the First Large-Scale Biogas Generation Plant in West Africa

More than 500 million people will be added to Africa’s cities by 2040, marking the largest urbanization in history. However, nonrenewable fossil energy sources are inadequate to meet Africa’s energy needs, and their overexploitation leads to intensified global warming. Fortunately, Africa has a huge potential for biomass energy, which will be an important option for combating climate change and energy shortage. In this study, we present a typical large-scale biogas plant in Burkina Faso, West Africa (Ouagadougou Biogas Plant, OUA), which is the first large-scale biogas generation plant in West Africa. The primary objective of OUA is to treat human feces, and it serves as a demonstration plant for generating electricity for feed-in tariffs. The objectives of this study are to assess the greenhouse gas reduction capacity and economic, environmental, and social benefits of OUA and to analyze the opportunities and challenges of developing biogas projects in Africa. As a result, the net economic profit of the OUA biogas plant is approximately USD 305,000 per year, with an anticipated static payback period of 14.5 years. The OUA plant has the capacity to treat 140,000 tons of human feces and 3000 tons of seasonal mixed organic waste annually, effectively reducing greenhouse gas emissions by 5232.61 tCO2eq, improving the habitat, and providing over 30 local jobs. Finally, the development of biogas projects in Africa includes advantages such as suitable natural conditions, the need for social development, and domestic and international support, as well as challenges in terms of national policies, insufficient funding, technical maintenance, and social culture.

Application of a Full-Scale Horizontal Anaerobic Digester for the Co-Digestion of Pig Manure, Food Waste, Excretion, and Thickened Sewage Sludge

Many laboratory- and pilot-scale studies on anaerobic co-digestion have been conducted in Republic of Korea; however, studies on full-scale demonstration facilities are lacking. This study aimed to present a successful case of a large-scale anaerobic co-digestion facility in Republic of Korea for biogas generation from four organic wastes (pig manure, food waste, excretion, and thickened sewage sludge) using a horizontal anaerobic digester. A preliminary biochemical methane potential test was performed for the individual and mixed organic waste to design a treatment facility for 320 m3/day of organic waste generated in Seosan City. Subsequently, a horizontal anaerobic digester with a 35 day-retention time (based on 320 m3/day input) was constructed. Each organic waste was placed in an anaerobic reactor after pretreatment. The input was gradually increased after the first seeding, and the operation continued for 158 days. Total and volatile solids made up 4.1% and 3.3%, respectively. Throughout the operating period, the digester temperature was maintained at 35–40 °C for mesophilic digestion, and the pH was maintained at 7–8. The average organic matter removal efficiency (volatile solids basis) was 64% and the methane gas production rates were 0.35, 0.6, 0.26, 0.28, and 0.39 Nm3CH4/kg vs. for pig manure, food waste, excretion, thickened sewage sludge, and mixed waste, respectively, resulting in an average methane content of the biogas 68.8%.

New insight into the synergistic reactions involved in the hydrothermal co-liquefaction of synthetic polymer wastes by molecular dynamics and DFT methods

Coliquefying synthetic aliphatic and aromatic polymer wastes using supercritical water has drawn considerable research attention. However, the mechanisms of chemical reactions between different types of polymers are ambiguous. Herein, depolymerization mechanisms for individual polymers and reaction mechanisms for binary polymer mixtures were investigated using molecular dynamics and density functional theory (DFT). The innovative approach showed that the production of oil from individual polymers during HTL was hindered by (1) volatile C1–C4 molecules emitted from aliphatic polymers and (2) polycyclic aromatic hydrocarbons (PAHs) produced from aromatic polymers. Interestingly, synergistic reactions among these byproducts from different polymers could promote oil production during coliquefaction. Specifically, the synergistic radical-related reactions included (1) the ring-opening of PAHs caused by C2H2 molecules emitted from aliphatic polymers and (2) the recombination of PHA branches and short-chain aliphatics. A considerable synergy between aromatic polymers with higher benzene ring contents and aliphatic polymers with lower H/C atomic ratios was observed near the critical temperature of 649 K. This work provides new insights into the synergistic reactions involved in the coliquefaction of synthetic polymers and gives useful guidance for realizing efficient oil production from mixed organic wastes.

Greenhouse Gas and Air Pollutant Emissions from Composting.

Composting can divert organic waste from landfills, reduce landfill methane emissions, and recycle nutrients back to soils. However, the composting process is also a source of greenhouse gas and air pollutant emissions. Researchers, regulators, and policy decision-makers all rely on emissions estimates to develop local emissions inventories and weigh competing waste diversion options, yet reported emission factors are difficult to interpret and highly variable. This review explores the impacts of waste characteristics, pretreatment processes, and composting conditions on CO2, CH4, N2O, NH3, and VOC emissions by critically reviewing and analyzing 388 emission factors from 46 studies. The values reported to date suggest that CH4 is the single largest contributor to 100-year global warming potential (GWP100) for yard waste composting, comprising approximately 80% of the total GWP100. For nitrogen-rich wastes including manure, mixed municipal organic waste, and wastewater treatment sludge, N2O is the largest contributor to GWP100, accounting for half to as much as 90% of the total GWP100. If waste is anaerobically digested prior to composting, N2O, NH3, and VOC emissions tend to decrease relative to composting the untreated waste. Effective pile management and aeration are key to minimizing CH4 emissions. However, forced aeration can increase NH3 emissions in some cases.

Improvement of the Polyhydroxyalkanoates Recovery from Mixed Microbial Cultures Using Sodium Hypochlorite Pre-Treatment Coupled with Solvent Extraction.

The use of mixed microbial cultures (MMC) and organic wastes and wastewaters as feed sources is considered an appealing approach to reduce the current polyhydroxyalkanoates (PHAs) production costs. However, this method entails an additional hurdle to the PHAs downstream processing (recovery and purification). In the current work, the effect of a sodium hypochlorite (NaClO) pre-treatment coupled with dimethyl carbonate (DMC) or chloroform (CF) as extraction solvents on the PHAs recovery efficiency (RE) from MMC was evaluated. MMC were harvested from a sequencing batch reactor (SBR) fed with a synthetic prefermented olive mill wastewaster. Two different carbon-sources (acetic acid and acetic/propionic acids) were employed during the batch accumulation of polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from MMC. Obtained PHAs were characterized by 1H and 13C nuclear magnetic resonance, gel-permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. The results showed that when a NaClO pre-treatment is not added, the use of DMC allows to obtain higher RE of both biopolymers (PHB and PHBV), in comparison with CF. In contrast, the use of CF as extraction solvent required a pre-treatment step to improve the PHB and PHBV recovery. In all cases, RE values were higher for PHBV than for PHB.

Composting effect and antibiotic removal under a new temperature control strategy

The main objective of this study was to investigate the feasibility of a new temperature control strategy in the co-composting process to accelerate operation cycle and remove antibiotics from mixed organic wastes. The evaluation of the composting process showed that composting with temperature control (TC) was completed within 14 days. The final compost of TC exhibited a 10% higher degradation of organic matters, more humus formation and 11.25% lower heavy metals concentration than conventional composting (CC), which fully met the Chinese National Agricultural Organic Fertilizer Standard requirements. The degradation extent and kinetic of macrolides, tetracyclines, sulfonamides and fluoroquinolones showed that the removal efficiency of total antibiotics in TC was 23.58% higher than CC, with less half-life, which was significantly correlated with higher temperature. Particularly, the highest removal was observed for sulfonamides (87.45%) in TC, the half-life of which was reduced by 75.95% compared with CC. The higher degradation rate was attributed to enhanced decomposition of unstable antibiotics and degrading activity of microbes at high temperature. The microbiological analysis showed that the external heating led to a distinct composition and succession of bacterial community in TC. Firmicutes, Proteobacteria, Actinobacteriota and Bacteroidota were dominant and the emergence of Patescibacteria and Chloroflexi at cooling period in TC proved that the later composting environment was in an oligotrophic state. Current research provided a promising rapid composting approach for high-quality fertilizer production and antibiotic management in organic waste disposal.

Tree-Based Automated Machine Learning to Predict Biogas Production for Anaerobic Co-digestion of Organic Waste

The dynamics of microbial communities involved in anaerobic digestion of mixed organic waste are notoriously complex and difficult to model, yet successful operation of anaerobic digestion is critical to the goals of diverting high-moisture organic waste from landfills. Machine learning (ML) is ideally suited to capturing complex and nonlinear behavior that cannot be modeled mechanistically. This study uses 8 years of data collected from an industrial-scale anaerobic co-digestion (AcoD) operation at a municipal wastewater treatment plant in Oakland, California, combined with a powerful automated ML method, Tree-based Pipeline Optimization Tool, to develop an improved understanding of how different waste inputs and operating conditions impact biogas yield. The model inputs included daily input volumes of 31 waste streams and 5 operating parameters. Because different wastes are broken down at varying rates, the model explored a range of time lags ascribed to each waste input ranging from 0 to 30 days. The results suggest that the waste types (including rendering waste, lactose, poultry waste, and fats, oils, and greases) differ considerably in their impact on biogas yield on both a per-gallon basis and a mass of volatile solids basis, while operating parameters were not good predictors of yield at this facility.

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.

Downstream processing and characterization of polyhydroxyalkanoates (PHAs) produced by mixed microbial culture (MMC) and organic urban waste as substrate

The utilization of food waste and sewage sludge as organic substrate from urban context for the synthesis of microbial polyhydroxyalkanoates (PHAs) has been only recently investigated at pilot scale. Within this context, two stabilization methods have been found for preserving the amount of PHA intracellularly produced by open mixed microbial culture (MMC): thermal drying and wet acidification of the biomass at the end of PHA accumulation process. The extracted PHA from the two differently stabilized biomasses was then characterized with regard to 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 93.0–79.8 and 7.0–20.2 w/w, respectively. PHA extracted from wet-acidified biomass had higher average molecular weights (Mw) of 370–424 kDa while PHA recovered from thermally stabilized dried biomass had a 3-fold lower Mw (on average). The PHA decomposition temperatures Td10% and Tdmax were in the range 260–268 °C and 269–303 °C, respectively, not dependent on the monomeric composition or molecular weight. Thermal properties such as melting temperature (Tm1 132–150 °C; Tm2 155–167 °C) and melting enthalpy (26–70 J/g) were quantified in a relatively broad range according to the different stabilization-extraction method and obtained composition.

Ingenious Method Towards Sustainable Decentralized Solid Waste Management

Solid waste management is a huge environmental threat not just in context to Indian Scenario, but globally as well. It is reported that on average around 1.5 lakh tones of solid waste is generated per day in India of which only 20% is treated and managed safely, the rest is dumped on land or burnt both which are highly toxic to human and animal health. At several waste processing sites in India, the fresh mixed waste received each day, is first manually separated to remove plastics and other non-biodegradable contents, this exposes the laborers to a very unhygienic working conditions and exposes them to deadly microbes and stench.. In the present work, we have developed an ingenious way which handles mixed waste with minimal manual intervention and protects the health of laborers while generating good quality manure. The mixed waste is directly fed in to the bio bins where due to microbial action, the biodegradable components are composted, the treated waste is then separated in to compost and non-biodegradable components using a bench top trommel. It was found that Bioinoculum combined with cow dung quickly achieved the compost of mixed organic waste with minimal maintenance in contrast to vermi-composting. From this study, it is observed that the mixed municipality waste could be treated and managed effectively, safeguarding the health of laborers and the generated compost is of good quality which can be used for crop cultivation or gardening

Biogas Synthesis as Means of Solid Waste Management in Kampala, Uganda

Cattle dung, cooked food waste, and chicken droppings mixed with coffee husks have been used separately and also as mixtures to form anaerobic digestion slurries in a bid to treat to degrade the organic fractions of these wastes and recycle the bio-fertilizer after recovering biogas. Single and mixed substrate slurries evolved significant quantities of methane within 27days together with reduced mass of soil conditioner. The volume of biogas formed in cogeneration mixtures were higher than for single substrate digestion due to the C/N ratio shifting to near 30:1 as a result of mixing. So degradation of organic pollutants was higher in mixed substrate digestion mixtures. Our study yielded average volumes ranging from 315 to 435+ 5.65.mL/L which was in agreement with what is in literature. Digestion of cattle dung, cooked waste foods, and droppings of chicken and mixed substrate slurries using sludge inoculums was very effective in degrading solid waste from homes, thus detoxifying it to bio-fertilizers. Although both single and mixed substrate digestion of waste yielded high enough volumes of biogas; digestion of slurry of mixed organic solid waste substrates is better method of waste management. Digestion of garbage from Kampala should be tested at macro levels at both ambient and mesophilic temperatures. There is need to try out the garbage digestion experiments in the semi-arid towns as well as very cold towns in Uganda.

Siloxane compounds in biogas from manure and mixed organic waste: Method development and speciation analysis with GC-ICP-MS

A novel method for the determination of linear and cyclic siloxane compounds (L2, L3, D3, D4, D5, and D6) in biogas was developed by combining gas chromatography (GC) with inductively coupled plasma mass spectrometry (ICP-MS). Using a continuous liquid quench sampling system, biogas samples were collected from a Swiss biogas production plant processing manure and mixed organic wastes. Although significant concentrations of siloxanes are normally linked to biogas from wastewater treatment plants (WWTP) or landfill gas, manure and mixed organic waste samples also showed values in the range of 0.1 mgSi Nm−3, which would be particularly critical for appliances such as solid oxide fuel cells (SOFC). The GC-ICP-MS method showed very good linearity for all the investigated compounds (R2 between 0.999 and 1.000). The limits of detection and quantification (LOD and LOQ) in the gas for cyclic compounds, such as D5, vary based upon the used sampling conditions (approximate range of 0.002–0.004 mgSi Nm−3 and 0.007–0.014 mgSi Nm−3, respectively). To the best of our knowledge, these LOD and LOQ values are by far among the lowest reported in literature and they satisfy the EURAMET (the European Association of National Metrology Institutes) requirements, which fix recommended levels for Si total amounts between 0.1 and 0.3 mgSi Nm−3 for measurement in biogas or bio-methane. The GC-ICP-MS method was evaluated by comparing its performances with a flame ionization detector (FID), operated in parallel with ICP-MS, and with GC-MS (gas chromatography - mass spectrometry). The GC-FID showed higher detection limits and matrix effects than GC-ICP-MS. Nevertheless, it can still be suitable for an initial estimation of the siloxane compounds present in the biogas, at least for samples having relatively high concentration, by following some data treatment optimization. The GC-MS analyses were considered here as a further confirmation of the accuracy of the GC-ICP-MS results.

FORMULASI PAKAN UNGGUL BERBASIS BIOTEKNOLOGI LIMBAH ORGANIK LOKAL UNTUK IKAN LELE ORGANIK KUALITAS EKSPOR

Research on Superior Feed Formulations Based on Local Organic waste Biotechnology for Export quality organic Catfish. Research Objective: The discovery of feed types of tilapia and organic catfish that have export quality nutritional content based on the best quality local marine organic waste through a touch of biotechnology. Furthermore, the complete chemical composition of the waste used and feed components is obtained. Research Methods: Determine the best composition of biomass of marine organic waste and local onshore organic wastes with the highest levels of protein and carbohydrates and integrated with other wastes. The nutritional content is analyzed, namely: Carbohydrates, fats, proteins, and supporting minerals, namely: Fe, K and Ca. Instrumentation used to support the research objectives is AAS and HPLC. Research Results: Export quality organic catfish pellet feed in the form of waste: marine fish, sea shrimp waste, sea crab waste, rice bran waste, corn waste, mixed organic waste, golden snail waste, seaweed waste and coconut water waste respectively (27; 15; 7.5; 33; 3; 2.5; 5; 2.5 and 2) %b/ b, starch 2% b/b and marine phytoplankton biomass 0.5% b/b. The nutritional content of organic catfish pellets that have been produced, namely: 51% protein b/b, 24% carbohydrate b/b, 9% fat b/b, crude fiber 8%b/b, water content 2 - 2.5%b/b, mineral Fe 1% b/b, mineral K 1% b/b, mineral Ca 1%b/b, ash content 2 - 2.5%b/b. Feed packing for export quality organic catfish pellets is given the "SANTARI-KU" label.
 Keywords: Superior feed, local organic waste biotechnology, export quality organic catfish, Santari-ku.

Aerobic Municipal Solid Waste Compost Quality According to Different Layers of Composting Bioreactor

Composting is one of the methods of solid waste management (SWM) where the organic component of solid waste stream is biologically decomposed under controlled conditions. A bioreactor tank was designed to contain 59.2 kg of mixed organic municipal solid waste, the organic matter was degraded under aerobic condition for 30 days. The tank was 45 cm in diameter, 130 cm total height and a 0.2 cm wall thickness. Three circular openings with screwed cover having diameter of 12 cm were leveled at (20, 40 and 80) cm respectively to withdraw samples. Temperature, moisture and pH were measured for three layers as process guideline indicators. Maximum temperature ranged between (34.79 to 46.91) ºC. Initial pH value was 6.53, ended within a range of (7.4 to 7.44). Chemical analysis for the composts in the three levels proved that the final C/N ratio ranged between (13.8 to16.1), TOC ended within a range of (17.33% to 25.24 %), final nitrification index (N-NH4/N-NO3) ranged between (0.22 to0.31), final of P% ranged between (0.89% to 1.23%), final of K% ranged between (1.69% to 1.81%) and results of germination index (GI %) ranged between (76.54%, to 88.35%) for three layers respectively. At the close of the experiment results proved that aerobic in-vessel composting could reduce the large amounts of wastes by 40% as a total mass. A satisfactory degree of decomposition was apparent in all levels, and the material was characterized by a pleasant earthy odor, and the obtained compost can be classified as mature compost. In conclusion, the three different layers do not have much effect on the quality indices of the final product.

Effective management of faecal sludge through co-digestion for biogas generation

The use of fossil fuels as primary energy source has led to global climate change and human health problems. Renewable energy resources appear to be the efficient solutions to the problems resulting from the use of fossil fuels. In this study, biogas production efficiency from faecal sludge and its combination with three feed stocks was evaluated. Three feedstock materials (cow dung, cow intestinal waste and mixed organic waste) were fed into a 2 m3 capacity digester to mix with faecal sludge for biogas production. Standard methods were used to determine chemical and biological qualities of influent and effluent slurries. The biogas produced was analyzed using multi-gas analyzer to determine the concentrations of CO, CO2, CH4 and H2S.Methane formed major component of the biogas produced by all the substrates (40-70%) followed by carbon dioxide (20-30%) and H2S (8-10%). The macronutrients of the bio-slurries produced ranged from Carbon (5.3 + 0.11- 6.0 + 0.01%), Nitrogen (0.36 + 0.1 - 0.46 + 0.1%), Phosphate (0.11 + 0.02 – 0.24 + 0.11%) and Potassium (0.1 + 0.01 - 0.4 + 0.1%). The Carbon/Nitrogen ratio of the bio-slurries produced ranged from 12:1 to 15:1. The microbial contents of faecal sludge, only slurry had lowest total count of bacteria of 1.2 x 10-2cfu/100ml. conclusively, co-digestion was effective in converting faecal sludge mixed the three feed stocks into pure biogas and nutrient rich bio-slurries as organic fertilizer.Keywords: Cow-dung, Biogas, Escherichia coli, Faecal-sludge

Investigation on greenhouse gas emissions and compost dynamics during in-vessel co-composting of septage and mixed organic wastes

Greenhouse gas emission during composting process is inevitable, although it relies on natural degradation. A good balance on carbon-to-nitrogen (C/N) ratio as well as the aeration mode could significantly control the emissions. The C/N ratio can be adjusted using optimal feedstock composition. The aeration can be done using passive and active modes. In the present study, greenhouse gas emissions during in-vessel co-composting of septage and organic waste with active and passive modes of aeration were investigated. This fills the gap in implementing suitable septage treatment practice. Retention of high temperature (> 55 °C) for prolonged period ensured the compost hygienization. The active aeration system showed significantly lower greenhouse gas emission compared to that of passive system. The contribution of CH4 and N2O to the total greenhouse gas was estimated to be 2.5% and 7.4% in the passive and 0.9% and 3.8% in the active aeration modes while > 90% was CO2. The resulted compost maturity was confirmed by seed germination index (> 80%) and NO3−/NH4+ index (> 6.25). Our study highlight that in-vessel co-composting with active aeration is a suitable option to convert waste to a nutrient-rich fertilizer in a shorter period compared to other septage treatment options.

Effective biorefinery approach for lactic acid production based on co-fermentation of mixed organic wastes by Enterococcus durans BP130

Abstract Various challenges facing the industrial manufacture of biobased lactic acid (LA) have been occurred. These include substrate and/or pre-treatments cost, medium cost, and contamination risk as a result of utilizing neutral pH and mesophilic conditions. Therefore, this study focused on development of consolidated bioprocess for LA production from organic wastes under harsh conditions. A newly isolated thermo-alkali-tolerant lactic acid bacterium, Enterococcus durans BP130, was firstly used for direct LA production from banana peels (BP). Increasing the solid concentration of BP from 4.0% to 6.7% [w-dry matter/v] have resulted in increased fermentation efficiency with the highest LA production (19.2 g L−1) at 6.7% [w-dry matter/v]. Besides, co-fermentation of BP and food waste (FW) materials resulted in 13% improvements in LA concentration and 12% in LA productivity at 0.5:1 of FW:BP (w/w). Increasing of food waste concentrations could replace the nutritional components of the media and achieved increased LA production. Without any nutrients supplementation, food waste substituted the medium components and resulted in 14.3 g L−1 of LA produced using mixed substrates of FW:BP at 3:1 (w/w). The highest LA concentration of 28.8 g L−1 with a yield of 0.85 g g−1-consumed sugar and productivity of 0.24 g L−1 h−1 was achieved in batch fermentation using CaCO3 as a neutralizing agent. This study introduced effective mixed waste-based biorefinery process for direct LA production in an inexpensive fermentation system.

Xanthobacter-dominated biofilm as a novel source for high-value rhamnose.

Rhamnose is a high-value carbohydrate used in flavorings, aromatics, and pharmaceuticals. Current demand for rhamnose is filled through plant-based sources; however, microbially originated rhamnolipids have been proposed as an alternative source. A mixed microbial biofilm, cultured from a wastewater sludge, was found to comprise > 8 dry weight% rhamnose when provided volatile fatty acids as carbon source, and 24 dry weight% when given glucose. The latter rhamnose concentration is a fourfold higher production mass than the current plant-based origin and is competitive with yields from pure microbial cultures. The biofilm was characterized based on total carbohydrate production at varying nutrient levels, individual carbohydrate monomer production from varying organic acid substrates, and microbial community composition-based on 16s rRNA. Biofilm carbohydrate production was maximized at a C:N ratio of 28 (mol:mol). The production of rhamnose varied significantly based on carbon substrate; glucose had the greatest yield of rhamnose, followed by propionic acid, lactic acid, acetic acid, valeric acid, and butyric acid. Microbial community analysis indicated an abundance of organisms within the Xanthobacter genus, which is known to produce rhamnose as zeaxanthin rhamnoside. Rhamnose production was heavily correlated with ribose production (R2 = 0.96). Results suggest that mixed microbial biofilms could be a competitive source of monomeric rhamnose that may be produced from mixed organic waste streams of variable composition via volatile fatty acids and glucose.