•Digestate from a decentralized on-farm biogas plant was assessed by a battery of ecotoxicological tests including plants, earthworms and aquatic organisms.•Obtained ecotoxicological parameters were ...used to derive indicators for future application of LCA and ERA.•Ecotoxicological investigation was performed under the “matrix-based” approach.
Over the last decade, the number of decentralized farm biogas plants has increased significantly in the EU. This development leads not only to an increasing amount of biogas produced, but also to a higher amount of digestate obtained.
One of the most attractive options to manage the digestate is to apply it as biofertiliser to the soil, because this gives the opportunity of recovering the nutrients, primarily nitrogen and phosphorus, and of attenuating the loss of organic matter suffered by soils under agricultural exploitation.
Studies have claimed that digestates can present a residual biodegradability, and contain complex organic elements, salts or pathogenic bacteria that can damage terrestrial organisms. However few ecotoxicological studies have been performed to evaluate the ecological impact of digestate application on soil.
In this study, the use of digestate as biofertiliser in agriculture was assessed by a battery of ecotoxicological tests considering the potential pollutants present in the digestate as a whole by using the “matrix-based” approach (also known as “whole effluent toxicity” for eluates or wastewater effluents). The direct and indirect tests included plant bioassays with Lepidium sativum, earthworm bioassays with Eisenia fetida, aquatic organisms (Artemia sp. and Daphnia magna) and luminescent bacteria bioassays (Vibrio fischeri).
Direct tests occurred to be more sensitive than indirect tests. The earthworm bioassays did not show serious negative effects for concentrations up to 15% (dry weight/dry weight percent, w/w dm) and the plant bioassays showed no negative effect, but rather a positive one for concentrations lower than 20% (w/w dm), which encourages the use of digestate as a biofertiliser in agriculture provided that proper concentrations are used. The indirect tests, on the eluate, with the using aquatic organisms and luminescent bacteria showed an LC50 value of 13.61% volume/volume percent, v/v) for D. magna and no toxicity for Artemia sp. and V. fischeri.
The ecotoxicological parameters obtained from the experimental activity have been analyzed so that they could serve in both ecological risk assessment (ERA) and life cycle assessment (LCA) to assess the risks and impacts of using digestate as a biofertiliser in agriculture. An interim effect factor of 1.17E−3m3/kg-in-soil is advocated and can be used in life cycle impact assessment modelling of terrestrial ecotoxicity. A predicted non effect concentration for soil organisms was defined at 341mg-digestate/kg-soil and can be used for the dose–response assessment step in ERA. Although these values are recommended for use in ERA and LCA applications, it should be stressed that they underlie important uncertainties, which should be reduced by increasing the number of toxicological tests, in particular of chronic studies conducted at different trophic levels.
Biological production of hydrogen (H2) by dark fermentation is an exciting scientific area for the conversion of low-cost residues and waste into biofuel. The main requirement for an efficient H2 ...production process is the availability of efficient microbial consortia in which H2-utilizing and non-H2-producing bacteria are suppressed. This study was performed to evaluate the H2 production potentials from the organic fraction of municipal solid waste (OFMSW) with and without addition of inoculum. The results showed that hydrogen productions from OFMSW without addition of inoculum were comparable to those obtained with inoculum but a latency phase of about 6 days occurred. On the contrary, addition of inoculum resulted in higher H2 production potentials without any latency phase. The use of a properly pre-treated inoculum confirmed to be an interesting and improvable tool to obtain high H2 yields from organic waste. However the indigenous OFMSW microbiota showed promising hydrogen yields especially toward the development of efficient hydrogen producing microbial inoculants.
•H2 production from municipal organic waste is feasible without addition of inoculum.•H2 production obtained without inoculum was comparable to that with inoculum.•Indigenous microbiota showed high hydrogen yields although with a 6 day latency phase.
•Inoculum pre-treatment technologies are aimed at suppressing H2 consumption in dark fermentation.•Inoculum pre-treatment methods have only temporary effects on H2 consuming populations.•Substrate ...pre-treatment methods enhance the hydrolysis of organic wastes.•Economic viability must be taken into consideration for either substrate or inoculum pre-treatment.
Hydrogen is regarded as a clean and non-carbon fuel and it has a higher energy content compared to carbon fuels. Dark fermentative hydrogen production from organic wastes is the most promising technology for commercialization among chemical and biological methods. Using mixed microflora is favored in terms of easier process control and substrate conversion efficiencies instead of pure cultures. However, mixed cultures should be first pre-treated in order to select sporulating hydrogen producing bacteria and suppress non-spore forming hydrogen consumers. Various inoculum pre-treatments have been used to enhance hydrogen production by dark fermentation including heat shock, acid or alkaline treatment, chemical inhibition, aeration, irradiation and inhibition by long chain fatty acids. Regarding substrate pre-treatment, that is performed with the aim of enhanced substrate biodegradability, thermal pre-treatment, pH adjustment using acid or base, microwave irradiation, sonication and biological treatment are the most commonly studied technologies. This article reviews the most investigated pre-treatment technologies applied for either inoculum or substrate prior to dark fermentation, the long-term effects of varying pre-treatment methods and the subsequently feasibility of each method for commercialization.
The benefits of using Black Soldier Fly (BSF) larvae in biowaste treatment include: commercial value of the stabilized residue, production of biomass rich in fats and proteins, suitable both for ...biodiesel production and animal feeding. The use of BSF for leachate treatment would introduce a blue low cost solution in the landfill technology, particularly appropriate in developing countries, where landfilling is still widely applied. This paper aimed to investigate the adaptability of BSF larvae to leachate environment, by using different leachate concentrations (25%, 50%, 75%, 100%) and two different feeding substrates: liquid (pure leachate) and semi-solid (wheat bran mixed with leachate). In all tests mortality was less than 50% and it was mainly linked to food shortages: the higher the nutrient content in leachate, the higher the larval development. Dry mass characterisation demonstrate that BSF prepupae biomass can be exploited as an alternative energy source in the production of biodiesel.
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•Adaptability tests of BSF larvae to the leachate environment.•Use of following substrates: pure leachate and mixture of wheat bran and leachate.•BSF larvae grow while feeding on different substrates containing landfill leachate.•larvae growth is an indicator of the feed consumed and of substrate treatment.•BSF prepupae biomass could be exploited as an alternative energy source.
Semi-aerobic landfilling is applied increasingly as a sustainable technology worldwide, although frequently controversial results are achieved. The authors suggest that differences in water ...availability (climate, moisture content, etc.) and putrescible waste content are the key factors involved in controlling performance and efficiencies. The aim of the present study was to investigate the effect of inverse conditions (high/low) of these two factors. Six lab-scale lysimeters were specifically set up to correspond to three different conditions of water availability (wet conditions, dry conditions and artificially controlled watering under dry conditions) and two different waste types (high and low putrescible content). Lysimeters were operated for four months under thermal-insulated conditions and the quality and quantity of emissions monitored regularly. Concentrations of mobile ammonia and total organic carbon (TOC) in landfilled waste were modelled by means of first-order kinetics, and carbon and nitrogen mass balances were calculated. The best performance for the semi-aerobic process was achieved at a water availability of approximately 1.5–2.4 kgH2O/kgTS using the following two combinations: a) Waste with high putrescible content and no addition of external water due to the presence of sufficient endogenous water in the waste (moisture) to promote biological stabilisation of waste (Respiration index in 4 days, RI4 = 12.87 mgO2/gTS, BOD/COD < 0.05); b) Waste with low putrescible content and controlled watering (RI4 = 12.25 mgO2/gTS, BOD/COD < 0.04). The study highlighted how semi-aerobic landfilling operations should be carefully adjusted case by case according to waste quality and climate conditions.
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•Water availability and putrescible waste content influence semi-aerobic landfills.•Appropriate water supply improved semi-aerobic landfill performance.•Effectiveness demonstrated by landfill gas (LFG) and leachate quality.
A lack of standardization in monitoring protocols has hindered the accurate evaluation of microplastic (MP) pollution in the open sea and its potential impacts. As sampling techniques significantly ...influence the amounts of MPs contained in the sample, the aim of this study was to compare two sampling methods: Manta trawl (size selective approach) and grab sampling (volume selective approach). Both approaches were applied in the open sea surface waters of the North-east Atlantic Ocean. Onshore sample processing was carried out using the innovative tape lifting technique, which affords a series of advantages, including prevention of airborne contamination during analysis, without compromising integrity of the results. The results obtained indicated an MP concentration over four orders of magnitude higher using grab sampling compared to the Manta net approach (mean values equal to 0.24 and 4050 items/m3, respectively). Consequently, the sole quantification of MPs using results obtained with the Manta trawl resulted in a marked underestimation of abundance. Nevertheless, the grab sampling technique is intricately linked to a risk of collecting non-representative water volumes, consequently leading to an overestimation of MPs abundance and a significant inter-sample variability. Moreover, the latter method is unsuitable for use in sampling larger MPs or in areas with low concentrations of MP pollution. The optimal sampling method therefore is dependent on the specific objectives of the study, often resulting in a combination of size and volume selective methods. The results of this study have the potential to contribute to the standardization of monitoring protocols for microplastics, both during the sampling phase and sample processing.A lack of standardization in monitoring protocols has hindered the accurate evaluation of microplastic (MP) pollution in the open sea and its potential impacts. As sampling techniques significantly influence the amounts of MPs contained in the sample, the aim of this study was to compare two sampling methods: Manta trawl (size selective approach) and grab sampling (volume selective approach). Both approaches were applied in the open sea surface waters of the North-east Atlantic Ocean. Onshore sample processing was carried out using the innovative tape lifting technique, which affords a series of advantages, including prevention of airborne contamination during analysis, without compromising integrity of the results. The results obtained indicated an MP concentration over four orders of magnitude higher using grab sampling compared to the Manta net approach (mean values equal to 0.24 and 4050 items/m3, respectively). Consequently, the sole quantification of MPs using results obtained with the Manta trawl resulted in a marked underestimation of abundance. Nevertheless, the grab sampling technique is intricately linked to a risk of collecting non-representative water volumes, consequently leading to an overestimation of MPs abundance and a significant inter-sample variability. Moreover, the latter method is unsuitable for use in sampling larger MPs or in areas with low concentrations of MP pollution. The optimal sampling method therefore is dependent on the specific objectives of the study, often resulting in a combination of size and volume selective methods. The results of this study have the potential to contribute to the standardization of monitoring protocols for microplastics, both during the sampling phase and sample processing.
Recent studies have investigated the use of Black Soldier Fly (BSF) larvae as a promising biological treatment process for high organic content wastewater (i.a. Leachate from municipal solid waste ...landfill, food processing effluents), achieving both high treatment efficiency and production of secondary resources from larval biomass (i.a. Proteins and lipids). The present study was aimed at achieving a better understanding of how organic concentration and load might influence treatment performance. Larvae were fed with three artificial wastewaters characterised by same organic substances quality (degree of biodegradability and oxidation of the organic content measured respectively as BOD/COD and TOC/COD ratios) but different organic concentrations. Each type of wastewater was tested at four different loads. Treatment performance was assessed by monitoring both larval growth (in terms of weight variation, mortality and prepupation), and variation of wastewater quality and quantity to determine organic substrate consumption (measured in terms of Total Organic Carbon, TOC). Larval starvation was observed in all tests when TOC concentrations dropped below approx. 1000 mg C/L, which, for the tested wastewater, could be assumed as the limit value for adopting BSF larvae process. Substrate concentration in the feed (mgC/L) influenced larval growth (in terms of maximum wet weight, prepupation and mortality) only when organic load was above 10 mgC/larva: the higher the load, the higher the positive impact of the substrate concentration. On the contrary, the specific substrate consumption rate (vS, mgC/larva/day) appeared not to be influenced by substrate concentration but only by the organic load, with a Michaelis Menten like relationship. Accordingly, substrate load can be assumed as a design parameter for BSF treatment process, while substrate concentration might only influence potential resource recovery from larval biomass.
•Concentration influenced larval growth, thus the amount of recoverable biomass.•Organic loads influenced the substrate consumption rates (vS) regardless of concentration.•vS Increased with organic loads, fitting a Michaelis Menten like relationship.•Treatment unit design can be based on organic loads, regardless of organics concentration.
•Biohydrogen production by using DM filtration was successfully applied.•Influent COD concentration significantly affected the DM filtration behaviour.•High influent COD concentration deteriorated DM ...filtration performance.•H2 production was affected by VFA accumulation at high influent COD.
This study investigates the possibility of using dynamic membranes (DMs) as a solid-liquid separation medium for fermentative H2 production under mesophilic conditions. In particular, the fouling behaviour of DM and H2 production are studied in response to different influent COD concentrations (10–100 gCOD L−1). The results demonstrate that the influent feed concentration significantly affects the filtration behaviour of DM. In fact, the decrease in influent COD concentration determined an improvement of both DM permeability and solids separation. In addition, high influent COD concentration (above 30 g L−1) and resulting high organic loading rates, favoured the accumulation of volatile fatty acids (VFA), leading to the inhibition of bio-hydrogen production. The results, thus, demonstrated that stable DM filtration and H2 production can be achieved by operating the bench-scale anaerobic DM bioreactor at low influent COD concentration (10–30 g L−1) and at an HRT of approximately 1 d. However, stable DM was achieved applying rather low filtration fluxes (approximately 2 L m−2 h−1).
Two-stage anaerobic digestion of food waste was performed using four different inoculum pre-treatment methods to enrich hydrogen (H2) producing bacteria from sludge. The pretreatments used in this ...study included heat shock, alkaline treatment, aeration, and a novel pretreatment using waste frying oil (WFO). Alkaline pretreatment and aeration did not completely inhibit methanogens in the first stage while no methane (CH4) was detected in the reactors cultivated either with heat shock or WFO-pretreated inocula. The highest H2 and CH4 yields (76.1 and 598.2 mL/gVS, respectively) were obtained using the inoculum pretreated with WFO. The highest total energy yield (21.96 kJ/gVS) and total organic carbon (TOC) removal efficiencies (95.77%) were obtained using inoculum pretreatment with WFO. The total energy yield trend obtained using the different pretreatments was as follows: WFO > alkaline > heat > aeration > control.
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•Two-stage anaerobic digestion using a novel inoculum pre-treatment method.•The novel pre-treatment was compared with three common inoculum pre-treatment methods.•Highest H2 and CH4 productions were obtained using the novel pre-treatment.
The inhalation of pesticide in air is of particular concern for people living in close contact with intensive agricultural activities. This study aims to develop an integrated modelling methodology ...to assess whether pesticides pose a risk to the health of people living near vineyards, and apply this methodology in the world-renowned Prosecco DOCG (Italian label for protection of origin and geographical indication of wines) region. A sample field in Bigolino di Valdobbiadene (North-Eastern Italy) was selected to perform the pesticide fate modellization and the consequent inhalation risk assessment for people living in the area. The modellization accounts for the direct pesticide loss during the treatment of vineyards and for the volatilization from soil after the end of the treatment. A fugacity model was used to assess the volatilization flux from soil. The Gaussian puff air dispersion model CALPUFF was employed to assess the airborne concentration of the emitted pesticide over the simulation domain. The subsequent risk assessment integrates the HArmonised environmental Indicators for pesticide Risk (HAIR) and US-EPA guidelines. In this case study the modelled situation turned to be safe from the point of view of human health in the case of non-carcinogenic compounds, and additional improvements were suggested to further mitigate the effect of the most critical compound.
•New approach for the evaluation of pesticide inhalation exposure nearby vineyards.•Volatilization from soil modelled with a fugacity model “Soil”.•Dispersion of pesticide modelled with CALPUFF.•No acute and chronic risk identified for residents.•Application of drift reduction technique has been investigated.
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