Methanogenic Potential Research Articles

Methodologies for Measuring Microbial Methane Production and Emission from Soils—A Review

Methane is an important greenhouse gas. Prediction of its long-term effect on climate changes requires understanding of the sources of its release into the atmosphere. The present work aimed to review the most widely used modern methods for measuring microbial production and emission of methane in soils, and to assess their applicability to various microbial ecosystems. A classification of methods for measuring methane production in microbial soil ecosystems is proposed, based on the basic physical and mathematical approaches to data processing for each method. Under laboratory conditions, methane production is determined by soil samples incubation and layered mass balance methods, which makes it possible to investigate the methanogenic potential of a microbial community for subsequent simulation of microbial processes; these methods, however, cannot be directly extrapolated to natural ecosystems. To determine methane production in field experiments, gradient methods are used, as well as a deep soil chamber technique developed for wetlands. Methods for measuring methane emission are described, as well as their advantages and limitations. While traditional chamber techniques are simple and therefore widely used, their implementation is limited by such factors as changes in environmental conditions caused by using the chamber, small spatial scales, and difficulties in chamber installation in some ecosystems. More recently developed micrometeorological methods are free of these limitations and provide for proper estimations of gas emissions from ecosystems even if these emissions are heterogeneous in space and time. To estimate emissions from such specific objects as landfills and livestock complexes or at large scales (regional or even global), the inverse modeling method is used.

Surface physico-chemistry governing microbial cell attachment and biofilm formation on coal

An essential but missing component in our understanding of microbial interactions leading to coal bed methane (CBM) formation lies in the relationship between coal and coal-adhering microorganisms. Here, we explored the influence of surface physico-chemistry on the microbial cell attachment on coal, utilising a known coal-oxidising bacterium P. fluorescens Pf-5 as a model. Based on the interfacial free energy of adhesion calculation and direct observation of cell adhesion on coal, natural lignite and subbituminous coals offered the most conducive surface for cell attachment driven by favourable hydrophobic and acid-base interactions. Coal pretreatments dramatically decreased coal surface hydrophobicity and increased its electron-donating potential (γ−), resulting in unfavourable interaction with cells that were hydrophilic and possessed high γ−. An exception to this was peroxide treatment, which maintained a low γ− of the coal surface and allowed favourable coal-cell interaction to occur. Cell colonisation on lignite appeared to be the strongest amongst all coal types, likely due to the relatively high van der Waals surface energy component that influence the adhesion strength in favourable cell-coal interactions. This would partly explain the higher methanogenic potential found in lignite compared to subbituminous coal in previous studies, as more adsorbed cells potentially lead to greater liberation of small organic compounds. Although our cell enumeration results generally correlated with the thermodynamic data, some exceptions were present that signify the biological role in cell-to-coal attachment and biofilm formation. Overall, these findings provide insights into the fundamental parameters that are involved in cell-coal adhesion dynamics at the molecular level.

Environmental methane emissions from seagrass wrack and evaluation of salinity effect on microbial community composition

Methane generation from seagrass contributes to green-house gases emissions but can also be a potential controlled biogas source. Understanding the natural fluctuations of emissions and the biotic and abiotic factors underlying such variations is essential. In this work, CH4 emission from beach-cast seagrass from the High-Adriatic coast was analysed. Biochemical methane potential (BMP) tests were used to evaluate CH4 generation at different temperatures (30 °C and 35 °C) and salinity levels (from 0‰ to 35‰), consistent with the typical observed environmental conditions. The changes in the microorganism community composition were investigated by means of amplicon metagenomics sequencing. The results underlined a specific CH4 emission in the range of 0.90–1.37 NmL CH4/g Volatile Solids (VS) d at 35 °C and 0.36–0.50 NmL CH4/g VS d at 30 °C. The most intense methane generation was observed at intermediate salinity levels of 18‰ at 35 °C and 9‰ at 30 °C. The total seasonal emission from the investigated beach-cast seagrass was estimated as 0.1399 mmol CH4/m2g. The microbial community analysis highlighted that Rhodobacteraceae was the most abundant family, coherently with its abundance in the marine environment. Low salinity (0–9‰) samples showed a prevalence of carbohydrate–degrading Ruminococcaceae, while the carbohydrate-fermenting Petrotogaceae were more abundant in high salinity (18–35‰) samples. The total lack of an important functional class was not noticed in any salinity level, except for sulphate-reducing bacteria, which were virtually absent when salinity was 0‰. The present study allows a better understanding of the environmental conditions resulting in a higher methanogenic potential and an enhanced comprehension of the bacterial communities associated to this process. The obtained information can be of help for designing efficient systems for producing methane from seagrass wrack, as well as for selecting the most appropriate managing route among the currently available technologies (such as on-site environmental preservation, composting, anaerobic digestion).

Repeatability and ranking of long-term enteric methane emissions measurement on dairy cows across diets and time using GreenFeed system in farm-conditions.

The aims of this work were to study on dairy farm conditions: i) the repeatability of long-term enteric CH4 emissions measurement from lactating dairy cows using GreenFeed (GF); ii) the ranking of dairy cows according to their CH4 emissions across diets. Forty-five Holstein lactating dairy cows were randomly assigned to 3 equivalent groups at the beginning of their lactation. The experiment was composed of 3 successive periods: i) pre-experimental period (weeks 1 to 5) in which all cows received a common diet; ii) a dietary treatment transition period (weeks 6 to 10); and iii) an experimental period (weeks 11 to 26) in which each group was fed a different diet. Experimental diets were formulated to generate more or less CH4 production: i) a diet based on ryegrass silage and concentrates, low in starch and lipid, designed to induce high CH4 emissions (CH4+); ii) a diet based on maize silage and concentrates, rich in starch, designed to induce intermediate CH4 emissions (CH4int); iii) a diet based on maize silage and concentrates, rich in starch and lipid, designed to induce low CH4 emissions (CH4-). Gas emissions were individually measured using GF systems. Repeatability of gas emissions, dry matter intake (DMI) and dairy performances measurements was calculated from data averaged over 1, 2, 4, and 8weeks for each animal. Hierarchical cluster analysis was performed to rank individual animals according to their CH4 emissions. No significant differences were observed for daily CH4 emissions (g/day) among diets, because of lower DMI of CH4+ cows. When CH4 emissions were referred to units of DMI or milk, the differences among diets emerged as significant and persistent over the observed period of lactation. Repeatability values of gas emissions measurements were higher than 0.7 averaged over 8weeks of measurement, but still higher than 0.6 for CH4 g/day, CO2 g/day, CH4 g/kg milk, and CH4/CO2 even averaging only 2weeks of measurement. The repeatability of CH4 emissions measurement was systematically lower than those of DMI or dairy performance parameters, like milk and FPCM yield, irrespective of the averaged measurement period. The dairy cow ranking was not stable over time between all individuals or within any of the diets. In our experimental conditions, the GF performance in the long term can be considered reliable in differentiating dairy herds by their CH4 emissions according to diets with different methanogenic potential, but did not allow the ranking of individual dairy cows within a same diet. Our data highlight the importance of phenotyping animals across environment in which they will be expected to perform.

Effects of alkali, autoclaving, and Fe+ autoclaving pretreatment on anaerobic digestion performance of coking sludge from the perspective of sludge extracts and methane production.

Pretreatment of activated sludge is an important step in increasing the reaction speed during anaerobic digestion by accelerating the hydrolysis process. It is necessary not only to analyze the changes in the general properties of the sludge before and after pretreatment but also to further analyze and evaluate the sludge structure and extracellular polymeric substances (EPS). In this study, the changes in coking sludge extracts after pretreatments with alkali, autoclaving, and Fe+ autoclaving were analyzed and compared using EPS heat extraction method. Moreover, the methane production potential of the pretreated coking sludge was investigated via biochemical methane potential (BMP) test. The results showed that after alkali, autoclaving, and Fe+ autoclaving, the concentration of protein and polysaccharide in the bound sludge extract accounted for approximately 40% and 28%, 62% and 51%, and 66% and 83% of the total protein and polysaccharide extracted from the sludge, respectively. In the experiment without pretreatment, there is no phenomenon of gas production from coking sludge. According to the BMP test results, Fe+ autoclaving pretreatment showed the highest methane production of 257mL/gVSS. This study revealed that the analysis of sludge extracts was necessary in assessing the effects of anaerobic digestion pretreatment and methanogenic potential. Moreover, coking sludge showed higher methanogenic potential after Fe+ autoclaving pretreatment.

Structural Characterization of Dissolved Organic Matter in Permafrost Peatland Lakes

Thermokarst lakes result from the thawing of ice-rich permafrost and are widespread across northern landscapes. These waters are strong emitters of methane, especially in permafrost peatland regions, where they are stained black by high concentrations of dissolved organic matter (DOM). In the present study, we aimed to structurally characterize the DOM from a set of peatland thermokarst lakes that are known to be intense sites of microbial decomposition and methane emission. Samples were collected at different depths from three thermokarst lakes in the Sasapimakwananisikw (SAS) River valley near the eastern Hudson Bay community of Kuujjuarapik–Whapmagoostui (Nunavik, Canada). Samples were analyzed by spectrofluorometry, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and elemental analysis. Fluorescence analyses indicated considerable amounts of autochthonous DOM in the surface waters of one of SAS 1A, indicating a strong bioavailability of labile DOM, and consequently a greater methanogenic potential. The three lakes differed in their chemical composition and diversity, suggesting various DOM transformations phenomena. The usefulness of complementary analytical approaches to characterize the complex mixture of DOM in permafrost peatland waters cannot be overlooked, representing a first step towards greater comprehension of the organic geochemical properties of these permafrost-derived systems.

Biogas y compost a partir de residuos

El incremento de residuos asociados al crecimiento de la población es un problema grave en nuestra sociedad. La posibilidad de biometanización es una alternativa amigable con el medio ambiente ya que contribuye al procesamiento de centenares de toneladas de basura que se acumulan en nuestras ciudades. En Neuquén, la fracción orgánica de los residuos alcanza el 44 % y es una potencial fuente de energía. Este puede ser valorizado por medio de biogas y compost.El potencial metanogénico se puede medir empleando el método de la jeringa que tiene la ventaja de ser un procedimiento experimental de bajo costo. El presente trabajo consistió en comparar la cantidad de biogas generada en función de la concentración de sólidos totales. El potencial de biogas es el volumen de producto generado por la cantidad de sustrato, en este caso, la fracción orgánica de los residuos. Se realizó el ensayo usandolo como sustrato y empleando el agua residual de laguna anaerobia como inóculo. Se utilizó jeringas de 60 ml a 35 °C con concentraciones sustrato 5 %, 10 %, 15 %, 20 % y 40 % de sólidos totales de la fracción orgánica y 10 ml de inóculo de agua residual de laguna anaerobia. Se determinó que la condición más favorable fue para las concentraciones de 5 % y 20 % de sólidos totales. Además, se evaluó la preparación de un acelerante para el digestato por el método de zucconi.

English

Wastewater treatment is a serious environmental problem, especially in developing countries such as Morocco. Their discharge into the natural environment has negative impacts on water resources and the environment. They are therefore purified to reduce the concentration of the main pollutants. Often biological remediation is used when wastewater contains biodegradable organic pollutants. This generally leads to treated water that can be discharged into the environment reused, or used as wastewater sludge. In the case of domestic or municipal water, this sludge has a fermentable character, which can have negative impacts on the environment especially when it is discharged directly into the environment. This sludge is subjected to various aerobic or anaerobic treatments to reduce the fermentable fraction. Anaerobic treatment seems more attractive because it gives the way to eliminate organic matter, produce biogas and manure compost both in one time. In this work, an experimental study was conducted on the ambient temperature anaerobic digestion of sewage sludge in two reactors, one operating without agitation and the other with agitation, to evaluate the impact of the latter on the biological process. Key words: Bio-methanization, ambient temperature, agitation, methanogenic potential, sludge, wastewater treatment plant, COD, pH.

Sequential bioethanol and methane production from municipal solid waste: An integrated biorefinery strategy towards cost-effectiveness

The organic fraction of municipal waste (OFMW), source-sorted (SS-OFMW) and non-sorted (NS-OFMW), was used as raw material for the sequential production of bioethanol and biogas. Non-isothermal and simultaneous saccharification and fermentation (NSSF) resulted in maximum ethanol concentrations of 51 g/L and 26 g/L for SS-OFMW and NS-OFMW samples, showing overall process yields of up to 80 % and 59 %, respectively, even without subjecting substrate to hydrothermal pretreatment. Subsequently, the solid residues resulting from the fermentation were further subjected to anaerobic digestion (AD), showing a methanogenic potential of 384 ± 6 mL CH4/g of volatile solids (VSin) and 322 ± 3 mL CH4/g VSin, respectively. These methane yields were similar or even higher to those obtained when using non-fermented OFMW substrates (SS-OFMW: 380 ± 18 mL CH4/g VSin and NS-OFMW: 239 ± 4 mL CH4/g VSin), highlighting NSSF as a beneficial step to enhance methane yields during AD. Overall, bioconversion of OFMW would benefit from coupling bioethanol and biogas production since the biogas produced might be further employed as bioenergy source to compensate operational costs.

Comparative analysis of prediction models for methane potential based on spent edible fungus substrate

In this study, ten spent edible fungus (SEF) with different compositional features were used for the maximum methanogenic potential (P0) evaluation, and the prediction models including regression and kinetics based on this were developed separately. The results showed that the regression model with more chemical components had a good correlation with the P0, and at least three chemical compositions could reach the threshold of sensitivity. The Cone model showed the best fitting effect on P0 in all kinetic models, which had higher R-square (>0.994) and lower error (1.004–5.672%). Meanwhile, the minimum digestive testing time (14 days) was determined by the evaluation of sensitivity via statistical indicators. It is concluded that the determination of the prediction model of P0 should be evaluated with the combination of statistical indicators and specific requirements.

Alternative methanogenesis - Methanogenic potential of organosulfur administration.

Alternative methanogenesis - Methanogenic potential of organosulfur administration.

Assessment of Inoculum to Substrate Ratio to Recover Energy from Cassava Wastes Through Anaerobic Digestion

The proliferation of cassava agro-food industries leads serious environmental problems due to the pollutants organic wastes discharge into the environment and heavy pressure put on forest resources to meet their internal energy needs. Biogas generated by anaerobic digestion is a versatile renewable energy vector regarding to the methane content which can be used to replace firewood and provide cassava factories with cost-effective energy. Cassava wastes show high biodegradables carbohydrates content against low nitrogen content. Due to the sugars content, cassava waste failed rapidly in inhibition during anaerobic digestion process. This paper focused on optimization of cassava wastes anaerobic digestion by using some chemical and adjusting the inoculum to substrate (I/S) ratio. The I/S = 1 is optimal to reach the maximal methane yield from cassava wastes. The biochemical methanogenic potential (BMP) showed 368 ± 26 mL/gVS; 156 ± 63 mL/gVS; 309 ± 75 mL/gVS respectively for untreated cassava wastewater (CWW), cassava peels treated with sodium bicarbonate (CP-Na) and cassava peels treated with potash locally (CP-P) called «akanwu». Untreated cassava peels (U-CP) yielded biogas with no methane content. The average methane content of the vial was at 71% (v/V) after 15 days of solid retention time (SRT) of CWW, 47% (v/V) and 58% (v/V) respectively for CP-Na and CP-P after 7 days of residence time.

Methanogenic potential of diclofenac and ibuprofen in sanitary sewage using metabolic cosubstrates

Diclofenac (DCF) and ibuprofen (IBU) are widely used anti-inflammatory drugs and are frequently detected in wastewater from Wastewater Treatment Plants and in aquatic environments. In this study, the methanogenic potential (P) of anaerobic sludge subjected to DCF (7.11 ± 0.02 to 44.41 ± 0.05 mg L−1) and IBU (6.11 ± 0.01 to 42.61 ± 0.05 mg L−1), in sanitary sewage, was investigated in batch reactors. Cosubstrates (200 mg L−1 of organic matter) in the form of ethanol, methanol:ethanol and fumarate were tested separately for the removal of drugs. In the DCF assays, P was 6943 ± 121 μmolCH4, 9379 ± 259 μmolCH4, 9897 ± 212 μmolCH4 and 11,530 ± 368 μmolCH4 for control, fumarate, methanol:ethanol and ethanol conditions, respectively. In the IBU assays, under the same conditions, P was 6145 ± 101 μmolCH4, 6947 ± 66 μmolCH4, 8141 ± 191 μmolCH4and 10,583 ± 512 μmolCH4, respectively. Without cosubstrates, drug removal was below 18% for 43.10 ± 0.01 mgDCF L−1 and 43.12 ± 0.03 mgIBU L−1, respectively. Higher P and removal of DCF (28.24 ± 1.10%) and IBU (18.72 ± 1.60%) with ethanol was observed for 43.20 ± 0.01 mgDCF L−1 and 43.42 ± 0.03 mgIBU L−1, respectively. This aspect was better evidenced with DCF due to its molecular structure, a condition that resulted in a higher diversity of bacterial populations. Through the 16S rRNA sequencing, bacteria genera capable of performing aromatic ring cleavage, β-oxidation and oxidation of ethanol and fatty acids were identified. Higher relative abundance (>0.6%) was observed for Smithella, Sulfuricurvum and Synthophus for the Bacteria Domain and Methanosaeta (>79%) for the Archaea Domain. The use of ethanol favored greater mineralization of organic matter and greater methane production, which can directly assist in the metabolic pathways of microorganisms.

New bacterial and archaeal lineages discovered in organic rich sediments of a large tropical Bay.

The nutrient and oxygen gradient present in marine sediments promotes high levels of microbial diversity. We applied metagenomics and biogeochemical tools to analyze microbial communities in different sediment depths (0-4m below sea floor, mbsf) from Guanabara Bay, Brazil, a brackish tropical ecosystem with a history of massive anthropogenic impacts, and a largely unknown sediment microbial diversity. Methanogens (e.g. Methanosarcinales, Methanomicrobiales) were more abundant at 1 mbsf, while sulphate-reducing microbes (Desulfurococcales, Thermoprotales, and Sulfolobales) were more abundant at deeper layers (4 mbsf; corresponding to 3K Radiocarbon years before present, Holocene Epoch). Taxonomic analyzes and functional gene identification associated with anaerobic methane oxidation (e.g. monomethylamine methyltransferase (mtmB), trimethylamine methyltransferase (mttB) and CO dehydrogenase/acetyl-CoA synthase delta subunit) and sulfate reduction indicated the dominance of Campylobacteria (Sulfurimonas) at deeper sediment layers. Gene sequences related to assimilation of inorganic sulfur increased with depth, while organic sulfur related sequences decrease, accompanying the clear reduction in the concentration of sulfur, organic carbon and chla torwards deeper layers. Analyzes of metagenome assembled genomes also led to the discovery of a novel order within the phylum Acidobacteriota, named Guanabacteria. This novel order had several in silico phenotyping features that differentiate it from closely related phylogenetic neighbors (e.g. Acidobacteria, Aminicenantes, and Thermoanaerobaculum), including several genes (carbon monoxide dehydrogenase, CO dehydrogenase/CO-methylating acetyl-CoA synthase complex subunit beta, heterodisulfide reductase, sulfite exporter TauE/SafE family protein, sulfurtransferase) that relevant for the S and C cycles. Furthermore, the recovered Bathyarchaeota genome SS9 illustrates the methanogenic potential in deeper sediment layer.

Kinetic study and experimental productions of methane production from UASB reactor treating wastewater from recycled pulp and paper for the continuous test

The aim of this research it is to show how the biogas anaerobic digestion from treatment of recycled pulp and paper wastewater industry (RPPW) can be a renewable energy. Furthermore, a kinetic study of hydrolyzed COD and productions of methane from UASB digester treating RPPW for the continuous test is established. This will allow to reduce the organic matter deposited in landfills and CO2 emissions and to find viable solutions to minimize the environmental impact of RPPW. This study analyses the biogas products and energy recovery processes from a thermic and electric point of view from the theoretical equations. Thus, this study evaluated the performance of mesophilic methanogenic up-flow sludge blanket reactors (UASB) operating continuously in single-stage (UASB I). The maximum methane yields were 250.9 mLCH4/gCOD removed for UASB I, corresponding to 82.7% of the maximum theoretical energy 6.336 kJ/gCOD removed, Methanogenic potential were 4 137 928 m3CH4/year and electrical energy potential were 510 703 MWh/year. The kinetic study allowed us a hydrolysis rate kh = 0.04 indicates a correct simulation for the UASB digester treatment system for RPPW with an R = 99.668%.

Comparison of methanogenic potential of wood vinegar with gradient loads in batch and continuous anaerobic digestion and microbial community analysis

Anaerobic digestion (AD) of wood vinegar wastewater (WVWW) has considerable potential in energy recovery and sustainable development. WVWW contains abundant acetic acid and some refractory organics. Therefore, the batch and continuous AD of WVWW were investigated. The threshold value of the inhibitory concentration was obtained at a chemical oxygen demand (COD) of 4 g/L in batch AD. Three-dimensional electrolysis was adopted to improve the biodegradability of WVWW, and a reduction in the inhibitory rate from 38.2% to 4.9% and an increase in methane production by 53.8% were observed. The up-flow anaerobic sludge blanket reactor achieved an efficient conversion of methane at an organic loading rate (OLR) of <8.58 g COD/L·d. However, the OLR of 10.01 g COD/L·d decreased the methane production from 350.6 to 42.5 mL CH4/g CODfed. Aminicenantales, Acetobacterium, Anaerolineae, and SBR1031 were the dominant bacterial genera in continuous AD. Fewer genera with similar classifications were detected in the batch AD. In the archaea community, acetotrophic methanogens (Methanosaeta) dominated and increased continuously with increasing OLR. Microbial analysis revealed that toxic substances affected bacterial diversity and promoted the enrichment of Intestinimonas, Syntropobacter, and Propionicimonas at high OLRs. The continuous AD was most suitable for the energy recovery from WVWW.

Methane production by anaerobic co-digestion of mixed agricultural waste: cabbage and cauliflower

ABSTRACT Anaerobic co-digestion of residual cabbage and cauliflower mixed at a ratio 1:1 (w/w) was investigated in two continuously stirred tank reactors under mesophilic conditions to ensure stability and enhanced methane generation. The experiments, including start-up, inoculum acclimatisation and treatment of the waste mixture, were carried out over a 65-day period. The characterisation results showed that the residual mixture contained a high proportion of total Kjeldahl nitrogen (around 37 g N/kg dry weight). The maximum value of methanogenic yield potential was found to be 250 LSTP/kg VS (volatile solid) added, at STP conditions (0°C, 1 atm), by loading organic substrate at a concentration of 1 g VS/L, while its biodegradability was 60%. However, instability of the biomethanisation process was observed after 17 days, which might be a consequence of the high concentration of nitrogen in the reactors. The evaluation of the kinetics of the valorisation process revealed that the waste mixture studied can easily be biodegraded through anaerobic co-digestion.

Indirect measures of methane emissions of Sahelian zebu cattle in West Africa, role of environment and management.

In Northern Senegal, traditional cattle management systems (TRAD) which depend on natural forages coexist with intensified systems (INT) which rely on periodic supplementation with crop residues and local concentrates. This study aims to estimate the effects of seasons and management systems on the methane emissions of Gobra zebu, in relation to the diet's chemical composition and feed intake. Six Gobra zebu cows per management system were individually monitored over 10months, diet and faeces were sampled each season and their chemical composition and dry matter intake (DMI) were predicted by near infrared spectroscopy. Each diet was fermented in vitro to assess methane production and volatile fatty acid concentration. The DMI and digestible organic matter intake (DOMI) decreased (P < 0.0001) during the dry seasons for both systems in the same range, but INT improved the crude protein of the diets (P < 0.0001). Enteric methane production (mmol.g-1 dry matter) was lower for TRAD than INT, except during the rainy season when TRAD cows experienced a higher increase (P = 0.002). The methanogenic potential (methane production in vitro × DMI) varied with the seasons and the system with more accentuated variations for TRAD (P< 0.0001). Methanogenic potential shows true reflection of the effects of the seasons and management systems. The results highlight that enteric methane emissions varied with seasonal changes and that intensifying the diet induced no mitigating effect.

Potential and location of an anaerobic digestion plant using prickly pear biomass in semi-arid Mediterranean environment

In recent years, prickly pear biomass has had a growing role in the area of agro-energy, aimed at the production of biogas and biomethane. However, technical validations of the use of prickly pears for energy purposes have not yet been carried out in Sicily, a region that accounts for more than 90% of Italian investment in cacti. A design idea was proposed in workshops to various stakeholders regarding building an anaerobic digestion plant to produce electricity from renewable sources (primarily but not exclusively prickly pear biomass). The BMP (biochemical methane potential) test was used to estimate the methanogenic potential of prickly pear biomass. Identification of the area in which to locate the investment [within the province of Catania and within the area governed by the production regulations of Ficodindia dell’Etna DOP (Etna Prickly Pear PDO)] was carried out using mainly AGEA data and a geographic information system (GIS). ISTAT and AGEA data were used to determine the individual variables, supplemented as necessary by information gathered through direct study and a face-to-face methodology. Existing relationships were studied using social network analysis (SNA). Results confirmed the benefits hoped for by interested stakeholders and also facilitated the identification of new alternative uses to that of fresh fruit sales. A biogas plant using prickly pears can, in this context, make a significant contribution – from the perspective of the circular economy – to supporting both the environment and producers.

Lab-scale anaerobic digestion of cassava peels: the first step of energy recovery from cassava waste and water hyacinth

ABSTRACT Cassava processing in Republic of Benin, which is used to produce different food products, discharges a large amount of polluting organic matter into the environment in the form of peels and wastewater. Besides, water hyacinth a rich nitrogen plant invades Benin water streams leading in aquatic ecosystem asphyxia and blocks the navigation. Both cassava wastes and water hyacinth show a high biodegradable content enable to be treated through anaerobic digestion. According to the literature, the main challenge in cassava wastes anaerobic digestion is early inhibition caused by a rapid acidification linked to low nitrogen and high biodegradable sugars content. This paper focused on the theoretical and biochemical methanogenic potential determination which is an essential step of recovery energy on large scale of both substrates. Stoichiometric methanogenic potentials of cassava wastes are close to the biochemical methanogenic potentials. However, it was necessary to treat cassava peels with potash «akanwu» and phosphate buffer pH 7.2. Average cumulative methane yield was 368 mL/gVS; 309 mL/gVS and 178 mL/gVS respectively for cassava wastewater (CWW), cassava peels (CP), water hyacinth (WH). Co-digestion of cassava peels with water hyacinth yielded on average 211 mLCH4/gVS. Despite that methane yield of co-digestion was lower than the summative methane yield of each substrate, the process has removed the chemicals products then improved cassava peels treatment. In addition, methane yield of water hyacinth increased by 10% when co-digested with cassava peels.