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Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of the fate, transport, and ecotoxicity of MPs and NPs in soil ecosystems. The objective of this study was therefore to develop a procedure to produce MPs and NPs from agricultural plastics (a mulch film prepared biodegradable polymer polybutyrate adipate-co-terephthalate (PBAT) and low-density PE [LDPE]), and to characterize the resultant materials. Soaking of PBAT films under cryogenic conditions promoted embrittlement, similar to what occurs through environmental weathering. LDPE and cryogenically-treated PBAT underwent mechanical milling followed by sieve fractionation into MP fractions of 840 μm, 250 μm, 106 μm, and 45 μm. The 106 μm fraction was subjected to wet grinding to produce NPs of average particle size 366.0 nm and 389.4 nm for PBAT and LDPE, respectively. A two-parameter Weibull model described the MPs' particle size distributions, while NPs possessed bimodal distributions. Size reduction did not produce any changes in the chemical properties of the plastics, except for slight depolymerization and an increase of crystallinity resulting from cryogenic treatment. This study suggests that MPs form from cutting and high-impact mechanical degradation as would occur during the tillage into soil, and that NPs form from the MP fragments in regions of relative weakness that possess lower molecular weight polymers and crystallinity.

Lignin, isolated from switchgrass (Panicum virgatum) and tulip poplar (Liriodendron tulipifera) using organosolv fractionation is currently being explored for its potential use in the production of value-added chemicals and bio-based polymers. Taguchi Robust Product Design (TRPD) was applied to maximize lignin yield from the fractionation process. The following four controllable design factors were used in the TRPD: process temperature (120 °C, 140 °C and 160 °C), fractionation time (56 and 90 min), sulfuric acid concentration (0.025 M, 0.05 M and 0.1 M), and feedstock type (switchgrass/tulip poplar chip ratios of 10/90, 50/50 and 90/10). Process noise was induced in the experiment by using either the mass- or volume-based feedstock charges of switchgrass and tulip poplar chips. A maximum mean lignin yield of 78.63 wt% and signal-to-noise ratio of 37.90 was found at a 90 min runtime, a process temperature of 160 °C, a sulfuric acid concentration of 0.1 M, and a feedstock composition of 10% switchgrass and 90% tulip poplar. Process temperature was the most significant factor that influenced lignin yield. This study may provide a pathway for industrialists and researchers interested in maximizing lignin yield in the organosolv fractionation process.