Seasonal changes in bulk density-based waste identification and its dominant controlling subcomponents in food waste

Bulk density is an effective evaluation criterion for food and residual household solid waste (HSW) source separation accuracy, but the effect of seasonal components on its variation is unknown. The objective was to accurately determine seasonal variation in bulk-density based waste identification and to ascertain the dominant controlling subcomponents in food waste leading to seasonal variation. A total of 540 bagged wastes were collected in Beijing in August and December representing summer and winter half year. Low-valued food and residual waste were the primary categories, accounting for 60% and 35% of HSW, respectively. Average residual waste threshold was <114 kg/m(3), irrespective of season, with good homogeneity (p=1.000). For food waste, winter thresholds were all lower than summer in investigated communities, appearing relatively seasonal difference (p=0.102), so they were divided into two: >193 kg/m(3) in winter and >211 kg/m(3) in summer. Mixed waste thresholds were 114-193 and 114-211 kg/m(3) in winter and summer, respectively. Moreover, the pericarp moisture remarkably changes with season (p<0.005) while other subcomponents remain unaffected. Frequency distribution of pericarp species further indicate a higher frequency of watermelon pericarp in summer leads to greater food waste moisture than in winter, and therefore significant bulk density threshold differences between seasons. Understanding seasonal change in bulk density identification provides a theoretical basis for 'intelligent supervision trashcan' application in various climate areas across China, further realizing more efficient residual and food waste resource recovery.