Energy recovery by anaerobic digestion of algal biomass from integrated microalgae/constructed wetland wastewater treatment.

The present study evaluated the potential for biogas generation from microalgae (MA) biomass and macrophytes used in vertical flow constructed wetlands (VFCW). The samples were obtained by separation and collection of MA after a hydraulic retention time of 14 days, frozen and taken to the laboratory, while the macrophytes of VFCW were obtained, by pruning, every 6 months. The obtained results presented reductions of 63.22% and 61.18% for COD and BOD5, respectively, and removal efficiencies of 53.91% for TP and 99.98% de N-NH3. Average biogas generation was 2322.51 NmL-gSV-1 with 54.61% CH4 (winter/2019), 4491.47 Nml-gSV-1 with 57.17% CH4 (spring/2019), 680.78 NmL-gSV-1 with 16.04% CH4 (summer/2020), and 681.0 NmL-gSV-1 with 19.86% CH4 (autumn/2020) for MA biomass and generation of biogas of 3826.70 NmL-gSV-1 with 44.26% CH4 for VFCW biomass in winter and spring/2019 and of 829.68 NmL-gSV-1 with 17.06% CH4 in summer and autumn/2020. Regarding electricity generation, the present work obtained 1.50 kWh/m3, therefore reaching similar values to other studies that used more traditional biomass sources.

Sustainability indicators for bioenergy generation from Amazon׳s non-woody native biomass sources.

This data article focuses on sustainability indicators for bioenergy generation from Brazilian Amazon׳s non-woody native biomass sources, considered to be modern forms of biomass. In the construction of the indicators, the Indicator-based Framework for Evaluation of Natural Resource Management Systems (MESMIS, from the original Spanish) method was used, with the application of the seven sustainability attributes to identify critical points and limiting and favorable factors for sustainability. The data yielded a list of 29 indicators distributed across 27 critical points, selected from three system evaluation areas: 11 environmental indicators, 11 social indicators, and 7 economic indicators.

Inventory data on Brazilian Amazon׳s non-wood native biomass sources for bioenergy production.

This data article presents a set of non-wood native biomass sources identified for bioenergy production in isolated communities living in Amazon׳s extractive reserves. The data were inventoried using management plan documentation, which provides technical information on Amazon׳s protected areas. The sample was collected from a virtual database published by the Ministry of Environment, the federal body responsible for managing protected areas in Brazil. Five variables were extracted from the management plans to produce the inventory, which includes data on biomass typology, nomenclature and occurrence, as well as mode of access to communities and availability of energy sources in the protected areas.

Life cycle comparison of waste-to-energy alternatives for municipal waste treatment in Chilean Patagonia.

The energy system in the Region of Aysén, Chile, is characterized by a strong dependence on fossil fuels, which account for up to 51% of the installed capacity. Although the implementation of waste-to-energy concepts in municipal waste management systems could support the establishment of a more fossil-independent energy system for the region, previous studies have concluded that energy recovery systems are not suitable from an economic perspective in Chile. Therefore, this work intends to evaluate these technical options from an environmental perspective, using life cycle assessment as a tool for a comparative analysis, considering Coyhaique city as a case study. Three technical alternatives were evaluated: (i) landfill gas recovery and flaring without energy recovery; (ii) landfill gas recovery and energy use; and (iii) the implementation of an anaerobic digestion system for the organic waste fraction coupled with energy recovery from the biogas produced. Mass and energy balances of the three analyzed alternatives have been modeled. The comparative LCA considered global warming potential, abiotic depletion and ozone layer depletion as impact categories, as well as required raw energy and produced energy as comparative regional-specific indicators. According to the results, the use of the recovered landfill gas as an energy source can be identified as the most environmentally appropriate solution for Coyhaique, especially when taking into consideration the global impact categories.

Assessment and optimization of an ultrasound-assisted washing process using organic solvents for polychlorinated biphenyl-contaminated soil.

The goal of this work was to evaluate a washing process that uses organic solutions for polychlorinated biphenyl (PCB)-contaminated soil, and includes an ultrasound pre-treatment step to reduce operational times and organic solvent losses. In a preliminary trial, the suitability of 10 washing solutions of different polarities were tested, from which three n-hexane-based solutions were selected for further evaluation. A second set of experiments was designed using a three-level Taguchi L27 orthogonal array to model the desorption processes of seven different PCB congeners in terms of the variability of their PCB concentration levels, polarity of the washing solution, sonication time, the ratio washing solution/soil, number of extraction steps and total washing time. Linear models were developed for the desorption processes of all congeners. These models provide a good fit with the results obtained. Moreover, statistically significant outcomes were achieved from the analysis of variance tests carried out. It was determined that sonication time and ratio of washing solution/soil were the most influential process parameters. For this reason they were studied in a third set of experiments, constructed as a full factorial design. The process was eventually optimized, achieving desorption rates of more than 90% for all congeners, thus obtaining concentrations lower than 5 ppb in all cases. The use of an ultrasound-assisted soil washing process for PCB-contaminated soils that uses organic solvents seems therefore to be a viable option, especially with the incorporation of an extra step in the sonication process relating to temperature control, which is intended to prevent the loss of the lighter congeners.

Lessons learned for a more efficient knowledge and technology transfer to South American countries in the fields of solid waste and contaminated sites management.

The present paper describes the development, performance and conclusions derived from three know-how and technology transfer projects to South American countries. The first project comprised a collaborative study by European and South American universities to find sustainable solutions for Chilean and Ecuadorian leather tanneries which had underachieving process performances. The second project consisted of investigations carried out in a Brazilian municipality to enhance its municipal solid waste management system. The final collaborative programme dealt with the initial identification, evaluation and registration of suspected contaminated sites in an industrial region of Chile. The detailed objectives, methods and procedures applied as well as the results and conclusions obtained in each of the three mentioned projects are presented, giving special attention to the organizational aspects and to the practical approach of each programme, concluding with their main advantages and disadvantages for identifying a set of qualitative and quantitative suggestions, and to establish transferable methods for future applications.

Investigations on mechanical biological treatment of waste in South America: towards more sustainable MSW management strategies.

This work presents an analysis on the suitability of mechanical biological treatment of municipal solid waste in South America, based on two previous experimental investigations carried out in two different countries. The first experiment was performed for determining the mass and volume reduction of MSW in the province of Concepción (Chile). The implemented bench-scale process consisted of a manual classification and separation stage, followed by an in-vessel biological degradation process. The second experiment consisted of a full-scale experiment performed in the city of Estrela (Brazil), where the existing municipal waste management facility was adapted to enhance the materials sorting and separation. Expressed in wet weight composition, 85.5% of the material input in the first experiment was separated for biological degradation. After 27 days of processing, 60% of the initial mass was reduced through degradation and water evaporation. The final fraction destined for landfilling equals 59% of the total input mass, corresponding to about 50% of the initial volume. In the second experiment, the fraction destined to landfill reaches 46.6% of the total input waste mass, whilst also significantly reducing the total volume to be disposed. These results, and the possible recovery of material streams suitable for recycling or for preparing solid recovered fuels, are the main advantages of the studied process.