Emissions and impacts of waste at disposal sites
With population increase comes greater waste generation. This results in a series of environmental, climate and health impacts at disposal sites, such as leachate and gas emissions. The study presented below describes the main harmful compounds generated from buried waste as well as the sustainable actions to eliminate the sources of these emissions, including waste co-processing in cement kilns. By Enrique De Hoyos, CEMEX, Mexico, Gabriela Ortiz, Debanhy Olvera, Diana Ángeles, Rodolfo de la Garza and Daniela Anaya, ITSEM, Mexico.
Figure 1: waste at a landfill (© Pixabay)Due to continuous population growth and urbanisation, environmental and public health challenges like waste management have become crucial. Human-generated waste significantly contributes to environmental and social issues in many countries. In this context, landfills – the final disposal site of solid waste – are particularly important sources of air, soil and water pollution, each of which is associated with specific groups of pollutants and other unwanted products. Thus, it is essential to provide proper means (ie, clinker kiln co-processing) for reintroducing these wastes into a circular economy to eliminate the negative impacts.
Phases of pollutant formation
Waste disposed in landfills undergoes several biological and chemical processes that generate pollutants in the form of gases and within leachate, the latter referring to liquid drained (via percolation) from the residue. These processes are divided into the five phases described below.1, 2, 3
Figure 2: leachate generation phases
(© CEMEX/ITSEM)
1. Initiation – organic compounds begin to decompose via aerobic microorganisms in the top layers, forming carbon dioxide (CO2).
2. Transition - in lower layers, the remaining organic matter decomposes anaerobically, producing CO2 and CH4. Low-pH leachate with volatile acids and diluted heavy metals is produced.
