Fresh Organic Waste Research Articles

Mortality, Development and Nutrient Content of Black Soldier Fly Larvae (Hermetia illucens L.) Maintained on Different Types of Household Organic Waste

Black Soldier Fly (BSF) has been well studied for many purposes including its utilization as fish feed and decomposer of organic waste. At the grassroots level, this species is used for alleviating the household waste problem, however, long-term mass rearing becomes challenging due to the high mortality and declining size of larvae, and its nutritional content as an alternative to fish feed becomes a question. The objective of this study is to evaluate the effects of different types of household organic waste on larval development, mortality rate, and nutrient content when larvae enter pre pupa stage. Seven days old larvae were maintained with five different types of fresh household organic waste, vegetable waste, animal waste, and mixed waste with three different combinations between vegetable and animal waste with proportions 1:1, 1:3, and 3:1. There are five units for each treatment with each unit containing 50 larvae. Larval morphometry and volumetry, Waste Reduction Index/WRI, Survival Rate/SR, and proximate analysis were observed. Types of Organic household waste significantly affect the mortality, development, and nutrient content of BSF larvae. BSF larvae maintained with a combination of vegetable waste and animal waste with a ratio of 3:1 have a better quality in terms of mortality, development, and nutrient content.

Peningkatan Kapasitas Masyarakat melalui Pengolahan Limbah Organik untuk Pupuk Tanaman di Pekarangan Perkotaan

The most sources of waste have been from households in urban area. The urban high population and daily food consumption effect the waste is potential to pollute the environment. Innovation of waste treatment should be applied by local community in urban area to reduce the household waste. This activity was a community service program UGM 2022 and supporting the Bantul Government program "Bantul free of waste 2025". The aims of this program were to improve community capacity and practice through household organic waste treatment. The activity was carried out at the Singosaren Padukuhan, Wukirsari Village, Imogiri, Bantul Regency, Special Region of Yogyakarta (DIY), in April‒October 2022. The method of program in community were included of field learning by teaching and practicing, community assistance, and evaluation of implementation. The 35 participants of PKK group from Singosaren hamlet joined this program that divided into 6 groups from 5 neighbourhood organisation (Rukun Tentangga). Organic waste process can be processed through fermentation of fresh organic waste (FLOS) or ecoenzyme and into liquid organic fertilizer using the stacked bucket (POCET) for 2–3 months. The FLOS and POCET products of waste fermentation are used as liquid fertilizers for cultivating plants in their yard Pekarangan. FLOS can also be used as multi-purpose liquid cleaner for home appliances. The raw materials included of fruit rind and vegetable waste. The results have showed the community enthusiasm, community capacity on organic waste processing and its utilization independently in the community. The application of FLOS and POCET as plant fertilizer showed better growing of plants in urban home gaden Pekarangan.

Carbon and hydrogen dynamic isotope equations are used to describe the dominant processes of waste biodegradation: Effect of aeration in methanogenic phase of the landfill

The sequence of microbiological processes occurring during the decomposition of fresh and old organic wastes from landfills is analyzed using the developed dynamic models, which are verified on the basis of experimental data previously obtained in anaerobic and aerobic laboratory reactors. The models are based on the material balances of the heavy and light isotopes of carbon and hydrogen during the biodegradation of cellulosic waste as a relatively poorly degradable substrate. According to the models, under anaerobic conditions, dissolved carbon dioxide is a substrate for hydrogenotrophic methanogenesis, which leads to an increase in the isotope signature of carbon in carbon dioxide and its subsequent stabilization. After the introduction of aeration, methane production ceases, and from that time on, carbon dioxide remains only a product of cellulose and acetate oxidation, which causes a significant decrease in the isotopic signature of carbon in carbon dioxide. The dynamics of the deuterium content in the leachate water is described as a consequence of the rate of its entry into and exit from the two (upper and lower) compartments of the vertical reactors, as well as the rates of its consumption and formation during microbiological reactions. According to the models, in the anaerobic case, the water is first enriched with deuterium due to acidogenesis and syntrophic acetate oxidation and then diluted with deuterium-depleted water, which is continuously fed to the top of the reactors. In the aerobic case, a similar dynamic is simulated.

Eco-enzyme as the natural disinfectant: Increasing school community awareness on waste management

The increase of COVID-19 has influenced aspects of life in global including education. Recently, the Indonesian government has given allowance to schools for conducting offline teaching-learning processes. Preparation should be conducted to maintain the protection of the school environment, including teachers and students. Health protocols remain an important requirement. SD Muhammadiyah 08 Dau Malang was one of the schools that wanted to prepare for conducting the offline teaching-learning process. The preparation of this school was cleaning all the school areas and spraying disinfectant to prevent the contamination of bacteria and viruses. Yet, the principal of SD Muhammadiyah 08 Dau Malang is concerned about the students’ and teachers’ health considering the chemical substance in the disinfectant. Moreover, the cost of disinfectant is also the consideration of the principal for savings. The result of an interview with the principal and observation of the school environment, it needs an alternative disinfectant that contains a less chemical substance, is effective, and is inexpensive. The disinfectant should not cause respiratory infections and is not harmful to students who are children. Concerning the problems faced by SD Muhammadiyah 08 Dau Malang, the team of community service programs brings solutions by introducing eco-enzyme and its advantages for health and the environment. It can be used as a natural disinfectant made of fresh organic waste from the kitchen. It is not only the solution to environmental health and virus protection but also recycling and utilizing waste.

Organic Carbon Speciation in Urban Anthrosols—The Legacy of Historical Waste Management

The impacts of waste management on various soils of agricultural and urban lands may last centuries or even millennia; however, generally, most studies tend to focus only on decadal or shorter timescales. This study investigates the characteristic properties of anthrosols in and around the urban settlement of St Andrews (Scotland), in the context of soil management and organic carbon content and speciation. Formed by the repeated application of fresh organic and pyrogenic wastes since the medieval period, these soils provide a 1000-year urban research context based on historical accounts of town waste management. We employed complementary methods of high-field solid-state 13C-CPMAS NMR, in situ magnetic susceptibility measurement, elemental micro-analysis and portable optically stimulated luminescence (OSL). A significant proportion of the soil organic carbon was present as refractory aromatic C structures, including aryl-C moieties. Portable OSL assessment revealed differences in the intensity and rate of sediment accumulation. The medieval urban areas had higher soil phosphorus concentrations, organic carbon content and magnetic susceptibility relative to the extra-urban site located outside of the medieval burgh. The study confirms that specific signatures, including carbon group functionalities, do reveal evidence of such induced long-lasting past anthropogenic soil modifications.

Technical means for disinfection and processing of bedding manure into organic fertilizers

Organic waste from agricultural production, bedding manure of cattle, pigs, sheep, horses, chickens and poultry litter when kept in cages are the main components for the production of organic fertilizers and biogas production. Waste of grain, cereal crops and sugar beets should be used as components for reducing moisture during aeration in piles, houses and bioreactors. Fresh organic waste should be stored on the sites in piles, where, before being processed in aeration houses and bioreactors, they must go through a mesophilic period. Fresh organic waste, when introduced into the soil in the first year, negatively affects the growth and development of plants, therefore, it must be disinfected and processed into organic fertilizers and biogas. Currently, the lack of knowledge about the methods of disinfection and processing of agricultural waste requires the development of new technological and technical solutions.

The Dynamics of C and N by Combination of Composted Fresh Organic Waste as Soil Amendment in the Soil Thickness at Pineapple Plantation, Lampung Indonesia

The purpose of the research was to study the effect of decomposition of fresh organic waste on improvement of soil nutrients, especially the presence carbon avalability at soil surface layer. The study was conducted to evaluate the decomposition progress of fresh organic waste and canned pineapple waste on Ultisol Lampung. The experiment was designed with a completely randomized factorial design with two factors: the first was fresh organic waste (200 ton.ha-1 chopper pineapple crops, 40 ton.ha-1 cattle manure, 40 ton.ha-1 cassava waste, 40 ton.ha-1 waste pump pineapple, 2 ton.ha-1 mill juice pineapple), and the second was thickness on the top layer (i.e. 0-15 cm, 0-30 cm and 0-45 cm), the each repeated 3 replication so total treatments were 24 plot pots. The results showed that the fresh organic waste and canning pineapple waste application can increase the resistance carbon and nitrogen on the soil. The more thickness of soil indicate to the more decrease of C, N, C/N ratio. The thickness of the soil 0-15 cm of C loss above 60%, 0-30 cm loss of C is less than 30 % and less than 20 % loos C-organic for 0-45 cm. The N loss less than 50 % on 0-15 cm, and less than 40% for 0-30 and 0-45 cm. Fresh organic matter decomposition rate in the near of top soil more faster than subsoil. The thickness of 0-45 cm it showed very low total carbon whiches affected to the the value of the C/N, It smaller than C/N ratio on the soil thickness above. Its because the process of decomposition of fresh organic matter mixed with mineral soil becomes slower. The innovation of technology that applied to combination on soil thickness with organic waste and canning pineapples can increase avalability of carbon and soil nutrients at Ultisol Lampung. It is an important aspect to improve soil fertility.

Odor mapping of an urban waste management plant: Chemometric approach and correlation between physico-chemical, respirometric and olfactometric variables

New approaches are of crucial importance to evaluate and minimize the odorous impact in the management of organic waste. The objective of this study is to develop an odor map to identify the highest critical odor points in an urban waste treatment plant from the physico-chemical, respirometric and olfactometric variables evaluated in different emission sources. Fresh organic waste such as sewage sludge (SL) and organic fraction of municipal solid waste (OFMSW) were found to be the most influential odorous substrates (14.57 and 2.41 ouE/s·m2, respectively), due to their high concentration in biodegradable organic matter. Compost derived from both fresh organic materials (C-SL and C-OFMSW) were the least influential substrates in terms of odor emission (≤0.1 ouE/s·m2) as a consequence of their stabilization. Inorganic waste (IW) showed an odor potential as high as 2.10 ouE/s·m2, similar to OFMSW, due to the organic material adhered to IW surface emits high amount of unpleasant odors. Leachate lagoons (LIX) were classified as middle critical emission points (0.7 ouE/s·m2), because of the high mineralization of nitrogen in the form of ammonical nitrogen. Moreover, the emission sources were clearly grouped according to their physico-chemical and respirometric characteristics by principal component analysis (PCA) and a value as high as 67.3% of the total variance was explained. Finally, odor emission was predicted from the physico-chemical and respirometric variables by multivariate regression, with respirometric variables (OD20 and SOUR), total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (N-NH4+) and the residence time (t) being the most influential variables on the prediction correlation (r = 0.9768). SL and OFMSW contributed 60% and 15%, respectively, to the global odor emission derived from the treatment plant, followed by IW (13%) and LIX (11%).

Inside the small-scale composting of kitchen and garden wastes: Thermal performance and stratification effect in vertical compost bins

Decentralized composting has been proposed as a best available practice, with a highly positive impact on municipal solid wastes management plans. However, in cold climates, decentralized small-scale composting performance to reach thermophilic temperatures (required for the product sanitization) could be poor, due to a lack of critical mass to retain heat. In addition, in these systems the composting process is usually disturbed when new portions of fresh organic waste are combined with previous batches. This causes modifications in the well-known composting evolution pattern. The objective of this work was to improve the understanding of these technical aspects through a real-scale decentralized composting experience carried out under cold climate conditions, in order to assess sanitization performance and to study the effects of fresh feedstock additions in the process evolution.Kitchen and garden organic wastes were composted in 500 L-static compost bins (without turning) for 244 days under cold climate conditions (Bariloche, NW Patagonia, Argentina), using pine wood shavings in a ratio of 1.5:1 v: v (waste: bulking agent). Temperature profile, stability indicators (microbial activity, carbon and nitrogen contents and ratio) and other variables (pH and electrical conductivity), were monitored throughout the experience.Our results indicate that small-scale composting (average generation rate of 7 kg d−1) is viable under cold weather conditions, since thermophilic sanitization temperatures (> 55 °C) were maintained for 3 consecutive days in most of the composting mass, according to available USEPA regulations commonly used as a reference for pathogens control in sewage sludge. On the other hand, stability indicators showed a differentiated organic matter degradation process along the compost bins height. Particularly, in the bottommost composting mix layer the process took a longer period to achieve compost stability than the upper layers, suggesting that differential organic matter transformation appears not to be necessarily associated to the order of the waste batches incorporation in a time line, as it could be expected. These findings suggest the need to discuss new ways of studying the composting process in small-scale compost bins as well as their commercial design.

Elucidation of functional chemical groups responsible of compost phytotoxicity using solid-state 13C NMR spectroscopy under different initial C/N ratios.

More than 1 milliontons of fresh organic wastes is produced in the Souss-Massa region in Morocco. Tomato organic residues represent more than 25% of the total organic wastes and are deposited in uncontrolled landfills. Thus, composting can represent a valuable and pertinent solution to this environmental problem. The objectives of this experiment are to identify the potential functional groups responsible for compost phytotoxicity and to determine the optimum initial carbon to nitrogen ratio (C/N) for maximum recovery of tomato residues. The experiment consisted of the variation of the initial C/N ratios (25, 30, 35, and 40) using mixtures of different raw materials (tomato residues, melon residues, olive mill pomace, and sheep manure). Physicochemical parameters (pH, electrical conductivity, C/N ratio, and humic acid/fulvic acid ratio) were determined and spectroscopic analyses (UV-vis and NMR-13C) were performed during the composting process along with quality parameters (germination and phytotoxicity tests) at the end. The results showed that the compost with the initial C/N ratio of 35 is the most humified with the least phytotoxic effect. The germination and phytotoxicity tests were negatively correlated with the methoxyl/N-alkyl-C ratio and O-alkyl-C. These two functional groups are probably the origin of phytotoxicity expression in compost quality tests. Thus, a simple and precise quality test could be performed to evaluate directly the phytotoxicity and maturity of compost.

Evaluation of PAH removal efficiency in an artificial soil amended with different types of organic wastes

The removal of polycyclic aromatic hydrocarbons (PAHs) from a spiked OECD (Organisation for Economic Co-operation and Development) artificial soil was investigated. Laboratory-scale thermally insulated bioremediation reactors were used to implement biostimulation strategy of composting. The selected PAHs included anthracene, chrysene, benzo(k)fluoranthene, and benzo(a)pyrene with an initial concentration of 658 mg of USEPA 16 PAHs kg−1 soil (d/w). The contaminants’ removal was improved by amending the contaminated soil with four different types of fresh organic waste. After 140 days of incubation, the removal of three-ring and four-ring PAHs in all reactors was higher than five-ring PAHs. The reactor displaying a mesophilic phase during bioremediation ended with a removal of 89 and 59 % for three-ring and four-ring PAHs, respectively. In contrast the reactor displaying a thermophilic phase ended with 71 and 41 % removal for three-ring and four-ring PAHs, respectively. The highest five-ring PAH removal was obtained for reactors with buffalo manure and sewage sludge amendments (40 and 33 %, respectively), while food and kitchen waste and fruit and vegetable waste amendments showed less efficiency (26 and 8 %, respectively). Microtox® test data indicated lower toxicity in reactor amended with sewage sludge considering that this setup reached the highest PAH removal and DHA (dehydrogenase activity) compared to others.

Impact of intermittent aerations on leachate quality and greenhouse gas reduction in the aerobic–anaerobic landfill method

The aerobic–anaerobic landfill method (AALM) is a novel approach in solid waste management that could shorten the landfill post-closure period and minimize the environmental loads. In this study, the aerobic–anaerobic landfill method was evaluated by using intermittent aeration. In addition, the nitrification–denitrification process was assessed as a means of reducing the emission of greenhouse gases (GHGs) and improving the leachate quality during the degradation of the organic solid waste. The leachate quality and the gas composition in each of the reactors were measured during the experimental period (408days). The aeration process entailed the injection of air into plexiglass cylinders (200cm height×10 cm diameter), filled with fresh organic solid waste collected from a composting plant. Different aeration routines were applied, namely, continuous aeration (aerobic reactor A), aeration for three days/week (aerobic–anaerobic reactor B), aeration for 6h/day (aerobic–anaerobic reactor C), and no aeration (non-aerated reactor D). It was found that aerobic reactor A produced the best results in terms of reduction of GHGs and improvement of the leachate quality. The aerobic–anaerobic reactor C was found to be more effective than reactor B in respect of both the emission of GHGs and the leachate quality; moreover, compared with aerobic reactor A, energy costs were reduced by operating this reactor. The transition period phenomenon was investigated during an intensive seven-day experiment conducted on the discharged leachate obtained from aerobic–anaerobic reactors B and C. The experiment concerned the differences in the composition of the gas during the aeration and the non-aeration periods. It was found that the transition period between the aeration and non-aeration cycles, which followed the simultaneous nitrification–denitrification had a considerable effect on the leachate quality of both the reactors. The results indicated that AALM has the potential to reduce leachate pollutants and the emission of GHGs. Furthermore, the occurrence of simultaneous nitrification–denitrification presents the prospect that intermittent aeration could reduce landfill aftercare and energy costs.

Hydrogen production of a salt tolerant strain Bacillus sp. B2 from marine intertidal sludge

To isolate a salt tolerant hydrogen-producing bacterium, we used the sludge from the intertidal zone of a bathing beach in Tianjin as inoculum to enrich hydrogen-producing bacteria. The sludge was treated by heat-shock pretreatment with three different temperature (80, 100 and 121°C) respectively. A hydrogen-producing bacterium was isolated from the sludge pretreated at 80°C by sandwich plate technique and identified using microscopic examination and 16S rDNA gene sequence analysis. The isolated bacterium was named as Bacillus sp. B2. The present study examined the hydrogen-producing ability of Bacillus sp. B2. The strain was able to produce hydrogen over a wide range of initial pH from 5.0 to 10.0, with an optimum at pH 7.0. The level of hydrogen production was also affected by the salt concentration. Strain B2 has unique capability to adapt high salt concentration. It could produce hydrogen at the salt concentration from 4 to 60‰. The maximum of hydrogen-producing yield of strain B2 was 1.65±0.04mol H(2)/mol glucose (mean±SE) at an initial pH value of 7.0 in marine culture conditions. Hydrogen production under fresh culture conditions reached a higher level than that in marine ones. As a result, it is likely that Bacillus sp. B2 could be applied to biohydrogen production using both marine and fresh organic waste.

Remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil through composting with fresh organic wastes

Composting may enhance bioremediation of PAH-contaminated soils by providing organic substrates that stimulate the growth of potential microbial degraders. However, the influence of added organic matter (OM) together with the microbial activities on the dissipation of PAHs has not yet been fully assessed. An in-vessel composting-bioremediation experiment of a contaminated soil amended with fresh wastes was carried out. Four different experimental conditions were tested in triplicate during 60 days using laboratory-scale reactors: treatment S (100% soil), W (100% wastes), SW (soil/waste mixture), and SWB (soil/waste mixture with inoculation of degrading microorganisms). A dry mass loss of 35 ± 5% was observed in treatments with organic wastes during composting in all the treatments except treatment S. The dissipation of the 16 USEPA-listed PAHs was largely enhanced from no significant change to 50.5 ± 14.8% (for SW)/63.7 ± 10.0% (for SWB). More obvious dissipation was observed when fresh wastes were added at the beginning of composting to the contaminated soil, without significant difference between the inoculated and non-inoculated treatments. Phospholipid fatty acid (PLFA) profiling showed that fungi and G-bacteria dominated at the beginning of experiment and were probably involved in PAH dissipation. Subsequently, greater relative abundances of G + bacteria were observed as PAH dissipation slowed down. The results suggest that improving the composting process with optimal organic compositions may be a feasible remediation strategy in PAH-contaminated soils through stimulation of active microbial populations.

Assessment of benefits and risks of landfill materials for agriculture in Eritrea

In Eritrea, farmers have applied landfill materials as fertiliser to their fields for several decades. A sampling scheme in the landfill site of Asmara and selected farmers' fields was carried out to investigate the benefits and risks of using landfill materials for agriculture. Soil samples were collected from farmers' fields (7 samples) and from the Asmara landfill site (12 samples). The samples were analysed for major plant nutrients, heavy metals (Cd, Cr, Cu, Pb, Ni, Hg and Zn), and some physical properties. Nearly 65% (by weight) of the total landfill material mined from the landfill site constituted waste fractions of various substances. The remaining 35% was composed of soil-like materials, which are apparently used to fertilize agricultural soils. The average organic matter, total nitrogen, and available phosphorus contents of soils with landfill material measured 2.4%, 0.13%, and 45 mg kg(-1), respectively. However, soils without landfill material consisted of 1.1 % organic matter, 0.04% total N, and <40 mg kg(-1) of available P. Except for Hg, all the other heavy metals in the landfill site showed values above the permissible limits. In particular, the average concentrations of Cu (913 mg kg(-1)) and Pb (598 mg kg(-1)) in the landfill site were nine-fold and four-fold greater than the allowable limits, respectively. It is, therefore, suggested that composting fresh organic wastes should be considered and tested as an alternative material for fertilising agricultural soils and to maintain the quality of the environment.

Application of fresh and composted organic wastes modifies structure, size and activity of soil microbial community under semiarid climate

Although the application of organic amendments is considered a suitable tool for improving soil fertility, few studies have been conducted in semiarid climates to evaluate the joint effect of such practice on the structure and function of the soil's microbial community. The aim of this work therefore was to make a comparative study of the effect of organic materials of differing degrees of stabilization (a sewage sludge and a compost made from the same) on the size, activity and structure of the microbial community in a semiarid soil. In samples taken in spring, summer and autumn over a 2-year period we analysed parameters that indicate the size of the microbial community [microbial biomass C (MBC)], its general activity (ATP and respiration) and specific activity related to the N, P and C cycles in the soil (urease, phosphatase and β-glucosidase, respectively). Two years after the organic amendment, the structure of the microbial community was studied by analysing phospholipid fatty acids (PLFAs). At the end of the experiment, the MBC of the compost and sludge-treated soils was 489 and 463 mg C mic kg −1, respectively, while the MBC of the control soils was 247 mg C mic kg −1. Over the 2-year period, the higher β-glucosidase, urease and alkaline phosphatase activities of compost and sludge-treated soils reflected higher substrate availability in these plots compared to the control plots. Indeed, plant abundance increased by about 25% with organic amendments. Whereas the bacterial to fungal ratio of signature PLFAs did not change, the ratio of monounsaturated/saturated and the ratio of Gram +/Gram − of the different treatments indicated that a different bacterial community developed 2 years after amendment with compost and sludge. Thus, factor analysis via PLFAs showed a change in microbial community structure in amended soils versus control soil. It can be concluded that microbial biomass and activity of degraded semiarid soils can be improved by the addition of organic materials of differing degrees of stabilization (compost and sewage sludge). Compost-amended soils showed the highest carbon contents, while in general no differences in activity or microbial biomass where found between compost or sludge treatments. Although phytotoxic substances in sewage sludge might negatively affect plant development, the similar density of plant cover developed in sludge and compost-treated soils suggests that any phytotoxic substances had been degraded.

Application of Different Organic Wastes on Soil Properties and Wheat Yield

Fresh and composted organic wastes [beet vinasse (BV), sewage sludge (SS), and a cotton gin crushed compost (CCGC)], were applied for 4 yr to a Typic Xerofluvent in dryland conditions near Seville, Spain. Organic wastes were applied at rates of 5, 7.5, and 10 Mg organic matter ha−1, respectively. The effect on the soil's physical properties, soil microbial biomass, and six soil enzymatic activities (dehydrogenase, urease, protease, β‐glucosidase, arylsulfatase, and alkaline phosphatase activities) and the yield parameters of wheat (Triticum aestivum cv. Cajeme) were ascertained. The application of CCGC compost improved the soil's physical (structural stability, bulk density), chemical (exchangeable sodium percentage, ESP), and biological properties (microbial biomass, soil respiration, and enzymatic activities) and the wheat yield parameters; however, the application of SS adversely affected the soil biological properties and reduced the wheat yield, probably because high of amounts of heavy metals. The application of fresh BV also adversely affected the soil's physical, chemical, and biological properties and the wheat yield, probably because high amounts of Na and fulvic acids were introduced into the soil by the vinasse, which destabilized its structure. Wheat yield decreased 22.5% in BV with respect to CCGC‐amended soil, 13.6% in SS with respect to CCGC‐amended soil, and 7.9% in BV with respect to SS‐amended soil. These results suggest that the chemical composition of the three organic wastes notably influenced the soil properties and therefore the wheat yield parameters. Of the three organic wastes studied, alone the application of CCGC originated a positive effect in the soil and in the wheat yield parameters, while the application of BV and SS originated a negative effect in the soil properties and therefore in the wheat yield parameters.

Evaluating the use of electrical resistivity imaging technique for improving CH 4 and CO 2 emission rate estimations in landfills

In order to improve the estimation of surface gas emissions in landfill, we evaluated a combination of geophysical and greenhouse gas measurement methodologies. Based on fifteen 2D electrical resistivity tomographies (ERTs), longitudinal cross section images of the buried waste layers were developed, identifying place and cross section size of organic waste (OW), organic waste saturated in leachates (SOW), low organic and non-organic waste. CH 4 and CO 2 emission measurements were then conducted using the static chamber technique at 5 surface points along two tomographies: (a) across a high-emitting area, ERT#2, where different amounts of relatively fresh OW and SOW were detected, and (b) across the oldest (at least eight years) cell in the landfill, ERT#6, with significant amounts of OW. Where the highest emission rates were recorded, they were strongly affected by the thickness of the OW and SOW fraction underneath each gas sampling point. The main reason for lower than expected values was the age of the layered buried waste. Lower than predicted emissions were also attributed to soil condition, which was the case at sampling points with surface ponding, i.e. surface accumulation of leachate (or precipitated water).

Microbial inoculum with leachate recirculated cultivation for the enhancement of OFMSW composting

Traditional composting operation may take over 2 weeks for the primary stage. The enhancement of the composting process will shorten the operation time and thus reduce the composting space and production costs. In this work, a microbial inoculum originated from the MSW leachate was used for the enhancement of the biodegradation of organic fractions of MSW (namely OFMSW hereinafter) in the composting process. The leachate generated from OFMSW composting was cultivated in the presence of foreign nutritions of beef extract, peptone, K 2HPO 4 and CaCO 3, respectively. The rough microbial inoculum was then harvested from the cultivated leachate and employed for the enhancement of OFMSW composting. One percent of the rough inoculum was mixed with 99% of the organic wastes (on wet basis). When the composting process proceeded at Day 7, the leachate thus generated was re-cultivated with the said nutrition and introduced into fresh organic wastes for another 7-day composting; repeating this step and the final generated leachate (namely final inoculum) was used for the fresh organic waste composting process. Seeding effects in terms of composting parameters (temperature, oxygen uptake rate, pH, cellulase, microbial numbers, moisture content, and nitrogen concentrations) were tested and the data were collected as reported in this paper. It was found that the temperature in the composting system seeded with the final inoculum could reach over 55 °C for the duration of over 96 h, and the numbers of thermophilic bacteria, actinomyces and molds in the refuse, increased by approximately 100%, 70% and 50%, respectively, after a 20-day primary composting. pH maintained at 7.0 with slight fluctuation, thus facilitating the microbial behaviors of cellulose depletion. Meanwhile, the oxygen uptake rate (OUR) and cellulase activity was observed to increase by some 50% and 26%, respectively. The development trend of nitrogen concentrations also indicated that the microorganisms in the final inoculum had the ability to endure the extreme temperature of 70 °C. Hence, it can be concluded that the final inoculum developed with leachate recirculated cultivation can work well, benefited from the indigenous communities present to efficiently accelerate the OFMSW composting process.

Enhanced soil toxic metal fixation in iron (hydr)oxides by redox cycles

The possibility to foster toxic metals (Cd, Cu, Ni, Pb and Zn) fixation on Fe (hydr)oxides, either native or added as ameliorants, was investigated at the laboratory scale in two heavily polluted arable and grassland soils by inducing repeated cycles of the reduction and oxidation. Soil samples were treated with Fe-rich waste (FeW) alone or together with fresh organic waste (OW) to accelerate reduction step. The FeW (242 g Fe kg − 1 ) was an air dried sediment produced by treatment of olive mill waste waters and the OW (410 g C kg − 1 ) was obtained by source separate collection of solid urban waste. The efficiency of metals immobilization was evaluated in terms of biological availability. Phyto-availability was assessed either by 1 M NH 4 acetate extraction (exchangeable fraction) and by 0.005 M DTPA/0.1 M triethanolamine (pH 7.3) extraction, whereas hazard to humans from direct soil ingestion (oral bio-accessibility) was tested by the physiologically based extraction test (PBET). Aerobic incubation of soils treated with FeW + OW did not cause any significant change to the exchangeable fraction of toxic metals in both the arable and the grassland soils, whereas one to three redox cycles, applied after FeW + OW addition, reduced Cd and Cu in both soils and Pb in the arable soil below detection limits. Exchangeable Zn was reduced in the FeW + OW treated soil by 50 and 90% in the arable and grassland soils, respectively. DTPA-extractable Cd, Cu and Zn were unaffected by treatments when soils were maintained oxic, but on the contrary, decreased significantly after one to three redox cycles by 88%, 93%, 36% and 95%, 98%, 65% in the arable and grassland soil, respectively. Lead showed a different behaviour with a general tendency to increase its availability. This result could be explained with the progressive dissolution of Mn oxides during the redox cycles. DTPA-extractable Ni showed in the arable soil a progressive increase, but remained constant in the grassland soil. A further reduction in DTPA-extractable metals, particularly evident for Ni, Pb and Zn, was observed after 150 d ageing of treated soils. Soil treatments were also effective in reducing potential hazard from direct soil ingestion in grassland soil (95%, 100%, 27% and 30% for Cd, Cu, Pb and Zn respectively), whereas the effect was much lower in the arable soil. The mechanisms of metal fixation are compatible with chemisorption and co-precipitation on Fe (hydr)oxides. These results suggest that redox cycles can be applied to FeW treated soils to reduce biological availability of many toxic metals in neutral soils, but their efficiency varies according to the element and soil composition. The addition of OW generally fosters metal fixation by intensification of the reductive process.