Moisture levels, biodegradation

Anaerobic. Moisture is added to the waste mass in the form of recirculated leachate and from other sources to obtain optimal moisture levels. Biodegradation occurs in the absence of oxygen (anaerobically) and produces landfill gas. Landfill gas, primarily methane, can be captured to minimize greenhouse gas emissions and for energy projects. 

Carmichael, Christman, and Pfaendeer, 1997). This is further exacerbated by poor contaminant solubility and pollutant aging. With temperature and moisture levels, there may be a reduction in rate of reaction, whereas in the case of inacces-sibiUty of contaminants, there may be a level of residual contaminant remaining at the end of the biodegradation process. 

From this viewpoint, the natural environments should be better identified, in terms of ecological habitats, and test approaches should in turn be based on the typical conditions experienced by the plastic products when entering each habitat, since the microbial population (and thus biodegradation activity) could be quite different. Tosin and co-workers [13] have identified 6 habitats where plastic waste can reside when littered in the marine environment 1) pelagic domain (the plastic products float freely in estuaries and the open ocean water), 2) eulittoral zone (tides and storm waves bring great quantities of plastic waste to the shoreline, where plastic products get partly buried and kept wet by tidal inundation and waves), 3) supralittoral zone (the plastic products are washed onto the beach, exposed to a sandy soil with a low moisture level), 4) sublittoral zone (plastic products settle on marine sandy sediment where they are exposed to the seawater/sediment interface), 5) plastic products can otherwise sink to the bottom of the deep sea and 6) plastic products can be slowly buried within sediments on the sea-floor. 

As previously mentioned, a minimum level of soil moisture is necessary for successful biodegradation. The continuous circulation of air during bioventing results in the evaporation of soil moisture. For this reason, the design of these systems must include an appropriate installation for adding water to the contaminated zone. Care must be taken to avoid the addition of excess water. If soil moisture is significantly increased, e.g., above the limit of 85%, air circulation is no longer effective due to the decrease in free soil porosity. 

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