Technical indicators to improve municipal solid waste management in developing countries: A case in Mexico.

Nowadays, increasingly complex sets of indicators are used to compare and diagnose municipal solid waste management (MSWM). These sets incorporate new priorities regarding sustainability and focus on measuring the progress to zero waste. Nevertheless, in developing countries, where MSWM is still striving to protect health from the potential impacts of waste, the MSWM information available is scarce and of low quality. This work proposes a basic set of indicators for analyzing technical aspects of street cleaning, waste collection and disposal in such contexts. Based on the assessment of 66 Mexican municipalities, ten indicators were identified that can be calculated with the information available. For each indicator, reference values were established, and their performance was evaluated by means of a traffic light system. In addition, a method that allows the quality of the information to be classified into four levels according to the data source, its uncertainty, the temporal coverage, and its spatial coverage was applied. The results obtained revealed an incipient implementation of MSWM and highlighted the need to increase the coverage of the collection services and to improve the conditions of the disposal sites in most of the municipalities that were studied. The proposed set of indicators can be used as a starting point to systematize the monitoring and detection of areas of improvement in the MSWM of the municipalities studied, as well as in other systems in similar contexts.

Degradation of Plastics under Anaerobic Conditions: A Short Review.

Plastic waste is an issue of global concern because of the environmental impact of its accumulation in waste management systems and ecosystems. Biodegradability was proposed as a solution to overcome this problem; however, most biodegradable plastics were designed to degrade under aerobic conditions, ideally fulfilled in a composting plant. These new plastics could arrive to anaerobic environments, purposely or frequently, because of their mismanagement at the end of their useful life. This review analyzes the behavior of biodegradable and conventional plastics under anaerobic conditions, specifically in anaerobic digestion systems and landfills. A review was performed in order to identify: (a) the environmental conditions found in anaerobic digestion processes and landfills, as well as the mechanisms for degradation in those environments; (b) the experimental methods used for the assessment of biodegradation in anaerobic conditions; and (c) the extent of the biodegradation process for different plastics. Results show a remarkable variability of the biodegradation rate depending on the type of plastic and experimental conditions, with clearly better performance in anaerobic digestion systems, where temperature, water content, and inoculum are strictly controlled. The majority of the studied plastics showed that thermophilic conditions increase degradation. It should not be assumed that plastics designed to be degraded aerobically will biodegrade under anaerobic conditions, and an exact match must be done between the specific plastics and the end of life options that they will face.