Solid Waste

Although plastic pollution happens globally, the micro- (-1), to earthworm casts (14.8 ± 28.8 particles g-1), to chicken feces (129.8 ± 82.3 particles g-1). Chicken gizzards contained 10.2 ± 13.8 microplastic particles, while no microplastic was found in crops. An average of 45.82 ± 42.6 macroplastic particles were found per gizzard and 11 ± 15.3 macroplastic particles per crop, with 1-10 mm particles being significantly more abundant per gizzard (31.8 ± 27.27 particles) compared to the crop (1 ± 2.2 particles). The data show that micro- and macroplastic are capable of entering terrestrial food webs.

Efforts to recycle organic wastes using black soldier fly (BSF) Hermetia illucens into high-nutrient biomass that constitutes a sustainable fat (biodiesel) and high-quality protein ingredient in animal feeds have recently gained momentum worldwide. However, there is little information on the most suitable rearing conditions for growth, development and survivorship of these flies, which is a prerequisite for mass production technologies. We evaluated the physiological requirements for growth and reproduction of H. illucens on two diets [spent grains supplemented with brewers' yeast (D1) and un-supplemented (D2)]. Development rates at nine constant temperatures (10-42°C) were fitted to temperature-dependent linear and non-linear day-degree models. Thereafter, life history table parameters were determined within a range of favourable temperatures. The thermal maximum (TM) estimates for larval, pre-pupal and pupal development using non-linear model ranged between 37.2 ± 0.3 and 44.0 ± 2.3°C. The non-linear and linear day-degree model estimations of lower developmental temperature threshold for larvae were 11.7 ± 0.9 and 12.3 ± 1.4°C for D1, and 10.4 ± 1.7 and 11.7 ± 3.0°C for D2, respectively. The estimated thermal constant of immature life stages development of BSF was higher for the larval stage (250±25 DD for D1 and 333±51 for D2) than the other stages evaluated. Final larval wet weight was higher on D1 compared to D2. The population growth rate was most favourable at 30-degree celsius (°C) with higher intrinsic rate of natural increase (rm = 0.127 for D1 and 0.122 for D2) and shorter doubling time (5.5 days for D1 and 5.7 days for D2) compared to the other temperatures. These results are valuable for the optimization of commercial mass rearing procedures of BSF under various environmental conditions and prediction of population dynamics patterns using computer simulation models.

The microbial colonization of plastic wastes has been extensively studied in marine environments, while studies on aged terrestrial wastes are scarce, and mostly limited to the isolation of plastic-degrading microorganisms. Here we have applied a multidisciplinary approach involving culturomics, next-generation sequencing analyses and fine-scale physico-chemical measurements to characterize plastic wastes retrieved in landfill abandoned for more than 35 years, and to assess the composition of bacterial communities thriving as biofilms on the films' surfaces. All samples were characterized by different colors but were all of polyethylene; IR and DSC analyses identified different level of degradation, while FT-Raman spectroscopy and X-ray fluorescence further assessed the degradation level and the presence of pigments. Each plastic type harbored distinct bacterial communities from the others, in agreement with the differences highlighted by the physico-chemical analyses. Furthermore, the most degraded polyethylene films were found to host a bacterial community more similar to the surrounding soil as revealed by both α- and β-diversity NGS analyses. This work confirms the novel hypothesis that different polyethylene terrestrial waste samples select for different bacterial communities, and that structure of these communities can be correlated with physico-chemical properties of the plastics, including the degradation degree.

The limitations of the research on the water-salt migration of sulfate-stained soil using solid waste as the sole binding material, such as the difficulty in characterizing the hydration reaction products over time, were addressed in this study. The research focused on different ratios of solid waste-based binding materials for solidifying sulfate-stained soil. Through the combination of experiments and theory, a water-salt migration model for solidified sulfate-stained soil using solid waste-based binding materials was established. Compared to traditional studies, this model can represent the time-dependent characterization of the hydration process. By introducing the grey correlation degree theory and using porosity as the evaluation index, the dynamic evolution characterization of the hydration products of solid waste-based binding materials was achieved. An innovative approach was adopted to construct the relationship between porosity and matrix suction using the Logistic curve, which served as a link to establish the water-salt migration equation. The porosity was used to control the spatial-temporal distribution of water and salt, compensating for the traditional model's neglect of the influence of changes in the cementing system on water-salt migration. The influence of the amount of binder, the proportion of slag, and the salt content on the pore structure of the solidified soil was systematically clarified, verifying that an increase in binder amount, an increase in the proportion of slag, and a decrease in salt content can significantly optimize the pore structure and inhibit water-salt migration. This provides a theoretical basis for the water-salt migration of solidified sulfate-stained soil using solid waste-based binding materials.