Data related to anaerobic digestion of bioplastics: Images and properties of digested bioplastics and digestate, synthetic food waste recipe and packaging information

Abstract

The data presented in this article are related to the research article entitled 'Degradation of some EN13432 compliant plastics in simulated mesophilic anaerobic digestion of food waste' (W. Zhang, S. Heaven, C. Banks, 2018). Zhang et al., 2018. They include quantification of residual materials from preparation of a synthetic food waste feedstock; photographic images of the physical appearance of the test plastics after prolonged exposure to microbial degradation in a continuously-operated anaerobic digestion trial; microscopic images of selected plastics after anaerobic biodegradation; test data and results for a Biochemical Methane Potential assay for the plastics; analytical data for potentially toxic elements in the plastics; and values for residual biogas potential of the digestate. Additional data on experimental methods is given, including a recipe for a synthetic food waste specifically designed for use in anaerobic digestion simulation studies; and details on adjustment of calculations after amendment of the digestate sampling methodology used in the main study.

Keywords: Anaerobic digestion; Biodegradation; Bioplastic; Co-digestion; Food waste; Plastic film.

Fig. 1

Items rejected during SFW preparation: (a) Packaging materials, (b) Materials not put through macerator.

Fig. 2

Plastic tokens recovered from digestate samples on day 98 of the digestion trial: (a) PP, (b) LDPE, (c) CBM. (Left-hand image shows total amount recovered in each case). Fig. 2 continued Plastic tokens recovered from digestate samples on day 98 of the digestion trial: (d) CBHS, (e) CBHB, (f) CBnHS, (g) CDF. (Left-hand image shows total amount recovered in each case). Fig. 2 continued Plastic tokens recovered from digestate samples on day 98: (h) SBF1, (i) SBF2, (j) PLAF, (k) PLAB. (Left-hand image shows total amount recovered in each case).

Fig. 2

Plastic tokens recovered from digestate samples on day 98 of the digestion trial: (a) PP, (b) LDPE, (c) CBM. (Left-hand image shows total amount recovered in each case). Fig. 2 continued Plastic tokens recovered from digestate samples on day 98 of the digestion trial: (d) CBHS, (e) CBHB, (f) CBnHS, (g) CDF. (Left-hand image shows total amount recovered in each case). Fig. 2 continued Plastic tokens recovered from digestate samples on day 98: (h) SBF1, (i) SBF2, (j) PLAF, (k) PLAB. (Left-hand image shows total amount recovered in each case).

Fig. 2

Plastic tokens recovered from digestate samples on day 98 of the digestion trial: (a) PP, (b) LDPE, (c) CBM. (Left-hand image shows total amount recovered in each case). Fig. 2 continued Plastic tokens recovered from digestate samples on day 98 of the digestion trial: (d) CBHS, (e) CBHB, (f) CBnHS, (g) CDF. (Left-hand image shows total amount recovered in each case). Fig. 2 continued Plastic tokens recovered from digestate samples on day 98: (h) SBF1, (i) SBF2, (j) PLAF, (k) PLAB. (Left-hand image shows total amount recovered in each case).

Fig. 11

No. of plastic tokens recovered from digestate sample, predicted no. assuming no destruction, and predicted no. modelled using an empirical first-order decay coefficient for (a) PP, (b) LDPE1, (c) LDPE2, (d) SBF1, (e) PLAB, (f) CDF, (g) CBM, (h) CBHS, (i) CBHB, (j) CBnHS, (k) PLAF and (l) SBF2.

Fig. 3

CBM. (a) Low magnification dark field image of CBM film showing areas where the metallic layer has ruptured and is detaching from the surface. (b) Image taken at a higher magnification using phase contrast, showing fractured surface where the metal coating has broken away. Images by Prof Francisco Torrella, University of Murcia.

Fig. 4

CBM film stained with aqueous methylene blue (MB), showing cellulose beneath the fractured film degrading through the formation of crater-like erosion pits. Bright field image (a) shows darker portions corresponding to areas where metal film is still attached. The reflection of the light in the dark field image (b) of the same area shows details of the material still present at the bottom of the erosion pit, unseen under bright field, with cracks on the film surface as seen from above. Images by Prof Francisco Torrella, University of Murcia.

Fig. 5

CBM film under bright field (oil immersion 100× objective). (a) Edge of an erosion pit showing bacteria on the pit sides spreading out as a biofilm over a component of the remaining cellulose film. The pinkish-red metachromasy surrounding the clear eroded area in the top left corner is evidence of bacterial growths at the periphery. The depth of focus (approx 0.5 μm) only shows a few bacteria on the borders of the eroded area but visual examination shows bacterial growth extending down into the pit. (b) Image showing bottom of pit and areas of bacterial attack around the edges. Images by Prof Francisco Torrella, University of Murcia.

Fig. 6

CBnHS. (a) Dark field low magnification clearly showing perforation of film as bright areas where light penetrates thinner sections. (b) Phase contrast showing extensive surface pitting. Images by Prof Francisco Torrella, University of Murcia.

Fig. 7

CBHS. Combined fluorescent and differential interference contrast images for sample CBHS showing pitting and microbial attack. Sample viewed using a Leica TCS SP2 confocal laser scanning microscope. Images courtesy of Dr Yue Zhang, University of Southampton.

Fig. 8

Data from BMP tests on feedstock components: (a) PLAB (1–3 = I/S ratio 3.8, 4–6 = I/S ratio 1.9), cellulose control; (b) SFW, CP, CBM and CBnHS; (c) PP, CBHS, CBHB, LDPE; (d) CDF, SBF1, SBF2, PLAF. I/S ratio = inoculum to substrate ratio used in the assay.

Fig. 9

Cumulative net specific methane production from residual whole digestate. Vertical dashed line indicates 28-day test duration.

Fig. 10

Feedstock materials: (a) Materials purchased for SFW, (b) preparation of SFW by maceration, (c) unprinted card packaging also used in the mixed feed prepared for the trial.