DOI: 10.57755/mxta-km21
title: SEM (Scanning Electron Microscopy) microstructural surface topography of biowaste and biowaste-derived composts with controlled moisture levels

description: <p>The dataset comprises SEM (Scanning Electron Microscope) micrographs presenting the microstructural surface topography of biowaste and biowaste-derived compost samples collected during a 14-day laboratory-scale composting process.</p><p>The composted material consisted of a biowaste mixture composed of cherry tree branches, fresh grass cuttings, and model food waste prepared according to Valta et al. (2019) (doi: 10.1177/0734242X18823943), in a mass ratio of 4:1.5:1, respectively. Composting was carried out at 45°C.</p><p>The study included three experimental variants differing in the initial moisture content of the biowaste:</p><ul><li>Reactors 1–4 correspond to biowaste with an initial dry matter content of 68.4% (denoted as M100 – representing the highest moisture level analyzed),</li><li>Reactors 5–8 correspond to biowaste with an initial dry matter content of 78.4% (denoted as M90 – representing a moisture level 10 percentage points lower than the highest),</li><li>Reactors 9–12 correspond to biowaste with an initial dry matter content of 87.4% (denoted as M80 – representing a moisture level 20 percentage points lower than the highest).</li></ul><p>During the composting process, distilled water was added every three days as follows: 10 mL to reactors 1–4, 5 mL to reactors 5–8, while reactors 9–12 were incubated without any water addition throughout the process.</p><p>Samples of substrates and composts were collected on days: 0, 7, 14. The SEM analysis was conducted for reactors R1-R3, R5-R7, R9-11.</p>
description: <p>A model food waste (FW) mixture (potatoes, rice, pasta, onions, apples, bananas, tomatoes, lettuce, bread, cheese, and ham) was prepared based on the methodology described by Valta et al. (2019) (doi: 10.1177/0734242X18823943). The composted material consisted of a biowaste mixture: cherry tree branches cut into ~10 cm pieces, fresh grass clippings, and food waste, combined in a mass ratio of 4:1.5:1, respectively, to achieve an optimal carbon-to-nitrogen (C:N) ratio for composting.</p><p>After preparing the biowaste mixture, it was divided into three groups with varying moisture content:</p><ul><li>a mixture with an initial dry matter content of 68.4%,</li><li>a mixture with approximately 10 percentage points lower moisture content (dry matter content of 78.4%),</li><li>and a mixture with approximately 20 percentage points lower moisture content (dry matter content of 87.4%).</li></ul><p>The latter two mixtures were obtained by drying the biowaste in a laboratory dryer at 105°C for 30 minutes and 75 minutes, respectively.</p><p>Reactor assignment was as follows:</p><ul><li>Reactors 1–4 correspond to biowaste with an initial dry matter content of 68.4% (denoted as M100 – representing the highest moisture level analyzed),</li><li>Reactors 5–8 correspond to biowaste with an initial dry matter content of 78.4% (denoted as M90 – representing a moisture level 10 percentage points lower than the highest),</li><li>Reactors 9–12 correspond to biowaste with an initial dry matter content of 87.4% (denoted as M80 – representing a moisture level 20 percentage points lower than the highest).</li></ul><p>During the composting process, distilled water was applied every three days: 10 mL to reactors 1–4, 5 mL to reactors 5–8, while reactors 9–12 received no additional water. The distilled water was evenly distributed over the surface of the waste in each bioreactor using a diffuser.</p><p>The composting experiment was conducted over a 14-day period using 900 mL bioreactors. The bioreactors were placed in thermostatic chambers (ST3, POL-EKO, Wodzisław Śląski, Poland) maintained at a constant temperature of 45°C. Aeration was passive and achieved by opening the bioreactors for approximately 10 minutes daily.</p><p>Samples of substrates and composts were collected on days: 0, 7, 14. The SEM analysis was conducted for reactors R1-R3, R5-R7, R9-11.</p><p>Before SEM analysis, the dried (105°C, 24 h) compost samples were ground to a particle size of 70–300 mesh using a laboratory mill operating at 28,000 rpm (Chemland, Stargard, Poland). The samples were then mounted on the microscope stage using carbon tape. Their surfaces were subsequently coated with a gold (Au) layer by sputtering for 300 s (coating thickness up to 2 nm) using an Edwards Scancoat Six Sputter Coater (Manor Royal, Crawley, West Sussex, UK). Microstructural surface topography analysis was performed with an EVO LS15 scanning electron microscope (Carl Zeiss, Germany) at an accelerating voltage of EHT &#61; 20 kV. Observations were carried out using a secondary electron detector (SE1). SEM micrographs were acquired for each sample at magnifications of 50×, 150×, 500×, and 1000×.</p><p>Sample codes follow the structure: M for Moisture level (100, 90, 80), D for Day (00, 07, 14), and R for Reactor number. For example, the sample coded M100D07R4 represents material from day 7, collected from reactor 4, operating at the highest moisture level.</p>