• Energy Research

AbstractThe optimization of degradation processes and the management of leachate and biogas produced in landfills are key aspects for the establishment of more sustainable municipal solid waste (MSW) disposal in developing countries. In this study, biochemical methane potential (BMP) tests were used to evaluate CH4 production potential and degradation kinetics of fresh waste (FW) and five-year aged excavated waste (EW) samples from a tropical controlled landfill with compositional characteristics of developing countries. BMP tests with reconstituted samples of the biodegradable fraction of both MSW types were performed at three substrate/inoculum (S/I) ratios (0.3, 0.5 and 1.0 g VS substrate g− 1 VS inoculum), and CH4 generation parameters were determined using the first-order and modified Gompertz kinetic models. After 30-d, the best BMP results were reached at S/I ratios of 0.5 and 1.0, with cumulative CH4 productions of 528 and 433 mL CH4 g− 1 VS for FW, respectively; and 151 and 135 mL CH4 g− 1 VS for EW, respectively. The first-order kinetic model provided a good fit to BMP results for FW, whereas the modified Gompertz model showed a better adjustment to the BMP data for EW. Calculated first-order CH4 generation rates for FW and EW were in the range 0.19–0.36 and 0.23–0.25 d− 1, respectively. These results evidence the high biodegradability and CH4 potential of FW disposed of in a tropical landfill in Colombia and the reduced BMP of EW despite a relatively short period after disposal under conventional landfill operation conditions.

Sugarcane press mud (SPM) has a high potential to produce renewable energy through anaerobic digestion (AD); however, hydrolysis is the limiting stage of the process due to the presence of slowly biodegradable compounds. An alternative that can improve this deficiency is anaerobic codigestion (AcoD). In this investigation, the monodigestion of SPM and its AcoD with food waste (FW) were evaluated through the biochemical methane potential (BMP) test, and kinetic parameters were analyzed through the analysis of the kinetic models of first order and modified Gompertz. This study showed that the AcoD of SPM with FW improved the hydrolysis stage, increased methane (CH4) yield, improved the stability of the process, and presented synergistic effects. As regards the hydrolysis stage, the hydrolysis constant was increased, and the lag phase was reduced. The monodigestion of SPM (SPM : FW 100 : 0) showed an increase of 9% with the addition of external nutrients solution, while that of AcoD in the SPM : FW 80 : 20 ratio showed the highest CH4 yield, with increments of 12 and 22% in comparison with the monodigestion of SPM under WN and NN conditions, respectively. It is even possible to add up to 40% of FW (SPM : FW 60 : 40) and achieve an increase of 5% compared to the monodigestion of SPM under the NN condition. The synergistic effects obtained in this study showed that the incorporation of FW, in the substrates ratios evaluated, would improve the AD of the SPM without addition of external nutrients solution, which represents economic and environmental benefits of implementing this alternative at full scale.

In the current study a literature review of household biowaste valorization in large urban centers of developing countries in Latin America and the Caribbean, as well as high-income countries worldwide, was performed. From the analysis of scientific and technical literature of official entities of the two evaluated contexts, 70 large urban centers (37 from Latin America and the Caribbean and 33 from high-income countries), from a total of 34 countries, were studied. The results indicated that household biowaste valorization is established in at least 27 large urban centers, three of them in Latin America and the Caribbean and 24 in high-income countries of North America, Europe, Asia and Oceania. In these, the implementation of 14 type-systems was identified. Although there are differences between the evaluated contexts, the most used treatment methods are composting and anaerobic digestion. Other methods used are thermal processing for animal food production and mechanical biological treatment with composting and with anaerobic digestion. It was evidenced that the implemented systems produce compost (mainly used in gardening and agriculture), electric power, heat, vehicular fuel and animal feed. Finally, despite the relevance of the household biowaste stream in Latin America and the Caribbean large urban centers, and the benefits of its recovery, the results of this study showed the predominance of household biowaste landfilling in this context. In consequence, it is recommended to establish the household biowaste as a priority fraction whose valorization should be the primary aim of management systems.

La codigestión anaerobia (CA) es una de las opciones viables para superar las desventajas de la mono-digestión. Esta investigación presenta los resultados del Potencial Bioquímico de Metano (PBM) donde se evaluó la CA de biorresiduos municipales (BM) de una localidad que realiza separación en la fuente y recolección selectiva con lodos de aguas residuales domésticas (LARD) provenientes de una planta de tratamiento de aguas residuales en diferentes proporciones de mezcla. Se evaluó la producción de metano mediante el modelo modificado de Gompertz y la hidrólisis a través del modelo cinético de primer orden, ya que esta es la etapa limitante en la CA de residuos sólidos. La proporción de mezcla LARD:BM donde se lograron las mayores producciones de metano (105.6 mLCH4·gSV-1), mejores constantes de hidrólisis (Kh) y fases de latencia cortas (menores a 3.3 días) fue 20:80.

Los biorresiduos constituyen la mayor fracción de los residuos sólidos municipales (RSM). El compostaje es una opción promisoria para su manejo, ya que genera un producto (compost) de valor agronómico que ayuda a conservar las propiedades del suelo. La previa selección de Sistemas Agroambientales (SA) con potencial para el uso de este subproducto, permite orientar el proceso de compostaje hacia la generación de un material que satisfaga los requerimientos de calidad de estos sistemas. En este estudio se evaluó la aplicación de una propuesta metodológica para la selección de los SA, la cual incorpora variables ambientales, técnicas, socioeconómicas e institucionales. La aplicación se realizó en el municipio de Versalles, departamento del Valle del Cauca, Colombia, que cuenta con una planta de compostaje de biorresiduos. El estudio permitió identificar, en su orden, el cultivo de café, áreas con pasturas dedicadas a la ganadería y las áreas degradadas, como los SA con mayor potencial para la aplicación de este compost en la zona de estudio. La aplicación de la herramienta puede permitir a los operadores de las instalaciones del compostaje de biorresiduos la planeación estratégica del proceso, contribuyendo a su mejoramiento y sostenibilidad.

Material recovery from municipal solid waste (MSW) is becoming widely adopted in several developing countries. Residential solid waste is one of the most important components of MSW and the handling practices of the MSW by the generators have a major impact on the quality and quantity of the materials for recovery. This article analyzes the generation and composition of residential solid waste and the handling practices by users in three municipalities in Colombia that have a solid waste management plant (SWMP). The findings show that, although there are significant amounts of useful materials, their handling of the materials as “garbage”, the low recognition of recovery work, and the inadequate storage and source management practices, affect material recovery and the operation of SWMPs. These results may be taken as a reference for this type of municipality, because the solid waste management system and the type of operation of the SWMPs analyzed is similar to all of the SWMPs in the country as well as in other countries in the region.