Techno-economic study for a gasification plant processing residues of sewage sludge and solid recovered fuels.

The energetic valorisation of wastes through gasification is a promising solution with a better environmental impact in terms of pollutant emissions compared with incineration, landfilling, and heat and power generation from fossil fuels. However, techno-economic studies are imperative to define the viability of these technologies and to optimise heat and power consumptions and costs. This work intended to develop a techno-economic analysis for a small-scale gasification plant processing mixtures of solid recovered fuels and sewage sludge, assuming a capacity of 883 kg/h and two different sale scenarios: (A) production of electric energy, and (B) production of hydrogen. Gasification tests and mass and energy flow analyses were carried out for the economic assessment. The results showed that both scenarios presented viability for implementation. Although scenario A was more attractive in the short-term period due to the lower payback period (9 year) and higher internal rate of return (IRR, 7.5%), the other option was more favourable at the end of plant's life once the net present value was greater (1,801,700 €). Based on the results of a sensitivity analysis, a conclusion could be drawn that the economic indicators payback period and IRR were most influenced by capital expenditures applied in the plant.

Virtual Reality Applied in a Thermoelectric Power Plant Planning

Abstract The planning of a new thermal power plant is linked to the various decision elements and evaluation criteria. Factors such as the plant's geographic positioning, primary energy supply points, paths, and means of delivery of this primary energy should be analyzed. Similar studies are imposed when studying the change of a thermoelectric plant's primary energy source occurs. In Brazil, several plants are currently investigating the exchange of their primary fuel from oil to gas due to the decrees issued by ANEEL. This paper presents software, which uses virtual reality to assist in the various stages of the planning process and in the analyses that must be performed. This software was developed for the Hidrotermica Group and had as the primary target the Borborema Thermoelectric Power Plant.

Unraveling interactive characteristics of microbial community associated with bioelectric energy production in sludge fermentation fluid-fed microbial fuel cells.

This first-attempt study deciphered the interactive characteristics of anodophilic microbial community-associated bioelectricity production in waste activated sludge (WAS) fermentation fluid-fed microbial fuel cells (MFCs). A novel schematic elucidation for illustrating synergistic interactions in anodic microbial consortia towards electrogenesis was proposed. Moreover, the specific genera of Pseudomonas, Desulfovibrio, Phyllobacterium, Desulfuromonas, Chelatococcus and Aminivibrio were dominant in anodic biofilms, leading to an electrogenesis efficiency of 1.254 kWh/kg COD and peak power density of 0.182 W/m2 (at feeding level of 1.20 g COD/L). It was apparently higher than those MFCs fed with glucose/acetate. The fermentative species contributed positively in reorganizing microbial community structure in anodic biofilms, positively relating to electrogenesis via interactions with exoeletrogens in MFCs. Finally, a more electrogenesis was positively associated to larger anodic microbial diversity, relatively medium anodic community evenness, together with higher abundance of functional genes related to electrogenesis in functional species in MFCs fed with WAS fermentation fluid.

An integrated approach for waste activated sludge management towards electric energy production/resource reuse.

This study developed an integrated approach for electric energy harvest/resource reuse from waste activated sludge (WAS) pretreated by enzymolysis based on anaerobic fermentation and microbial fuel cells (MFCs). WAS solubilization by the 3-h enzymatic pretreatment (a blend of hydrolytic enzymes caused over 5300 mg/L soluble COD release) prompted volatile fatty acid (VFA) production with 3580 mg COD/L after 10-d fermentation. After solid-liquid separation, fermentation liquid with high VFA content was fed into MFCs for electric energy production, while solid residues were used for making building materials (such as blended cements). Results showed that the electricity conversion efficiency of fermentation liquid (VFA) reached 1.254 kW h/kg COD with over 90% organics removal and solid residues could be consumed potentially as qualified substitutes for producing cements. As such, this study may provide some new thinking on future WAS management towards electricity harvest/resource reuse with zero secondary wastes discharge.

Realization of Quasi-Omnidirectional Solar Cells with Superior Electrical Performance by All-Solution-Processed Si Nanopyramids.

Large-scale (156 mm × 156 mm) quasi-omnidirectional solar cells are successfully realized and featured by keeping high cell performance over broad incident angles (θ), via employing Si nanopyramids (SiNPs) as surface texture. SiNPs are produced by the proposed metal-assisted alkaline etching method, which is an all-solution-processed method and highly simple together with cost-effective. Interestingly, compared to the conventional Si micropyramids (SiMPs)-textured solar cells, the SiNPs-textured solar cells possess lower carrier recombination and thus superior electrical performances, showing notable distinctions from other Si nanostructures-textured solar cells. Furthermore, SiNPs-textured solar cells have very little drop of quantum efficiency with increasing θ, demonstrating the quasi-omnidirectional characteristic. As an overall result, both the SiNPs-textured homojunction and heterojunction solar cells possess higher daily electric energy production with a maximum relative enhancement approaching 2.5%, when compared to their SiMPs-textured counterparts. The quasi-omnidirectional solar cell opens a new opportunity for photovoltaics to produce more electric energy with a low cost.

Comparison of the mesophilic and thermophilic anaerobic digestion of spent cow bedding in leach-bed reactors.

Anaerobic digestion of spent cow bedding in batch leach-bed reactors (LBRs) was compared in mesophilic and thermophilic conditions for the first time. Results show that the use of thermophilic conditions enhanced only the degradation kinetics of easily-degradable matter during the first days of the digestion, whereas similar methane yields (80% of the Biomethane Potential) were reached after 42days at both temperatures. Therefore, the anaerobic digestion in LBRs of spent cow bedding, a substrate rich in slowly-degradable compounds, was not improved in term of methane production considering the overall digestion time. Moreover, the high initial biogas production rate in thermophilic reactors was found to significantly reduce the energetic performance of the cogeneration unit at industrial scale, leading to a 5.9% decrease in the annual electricity production when compared to a mesophilic one.