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Plastic mulch films contribute to better crop production. Concerns for lack of sustainable disposal methods for conventional polyethylene (PE) mulch led to development of biodegradable plastic mulches (BDMs) that can be soil-incorporated or composted after use. Environmental weathering of BDMs during crop growth reduces their mechanical strength and alters the molecular structure of their polymeric components. However, the impact of weathering on BDMs’ biodegradability is not fully understood. The biodegradability of agriculturally weathered and unweathered BDMs in soil and compost was compared using standardized laboratory tests (ASTM D5988 and D5338) using four BDMs (experimental polylactic acid and polyhydroxyalkanoate-based film [PLA/PHA] and three commercially available polybutyrate [PBAT]-based BDMs). In soil, biodegradation of weathered PLA/PHA was greater than its unweathered counterpart. For PBAT-based BDMs, the extent of biodegradation varied. A decrease of the weight-averaged molecular weight (Mw) of PBAT and PLA and thermostability of PLA, PHA, PBAT, and starch components was observed during biodegradation in the soil. The proportion of the minor components PHA and starch decreased during biodegradation, indicating preferential utilization of PHA over PLA and starch over PBAT by microbes. Bacterial abundance was significantly higher than fungal abundance in soil and was more prominent in soil adjacent to weathered than unweathered BDM treatments. Under composting conditions, unweathered PBAT-enriched mulches yielded higher CO2 evolution than their weathered counterpart. Together, these results suggest that environmental weathering enhances biodegradation of BDMs and mulch’s polymeric constituents also influence the microbial degradation, more so for bacterial than fungal communities.

Microplastics (MPs) and nanoplastics (NPs) dispersed in agricultural ecosystems can pose a severe threat to biota in soil and nearby waterways. In addition, chemicals such as pesticides adsorbed by NPs can harm soil organisms and potentially enter the food chain. In this context, agriculturally utilized plastics such as plastic mulch films contribute significantly to plastic pollution in agricultural ecosystems. However, most fundamental studies of fate and ecotoxicity employ idealized and poorly representative MP materials, such as polystyrene microspheres. Therefore, as described herein, we developed a lab-scale multi-step procedure to mechanically form representative MPs and NPs for such studies. The plastic material was prepared from commercially available plastic mulch films of polybutyrate adipate-co-terephthalate (PBAT) that were embrittled through either cryogenic treatment (CRYO) or environmental weathering (W), and from untreated PBAT pellets. The plastic materials were then treated by mechanical milling to form MPs with a size of 46-840 µm, mimicking the abrasion of plastic fragments by wind and mechanical machinery. The MPs were then sieved into several size fractions to enable further analysis. Finally, the 106 µm sieve fraction was subjected to wet grinding to generate NPs of 20-900 nm, a process that mimics the slow size reduction process for terrestrial MPs. The dimensions and the shape for MPs were determined through image analysis of stereomicrographs, and dynamic light scattering (DLS) was employed to assess particle size for NPs. MPs and NPs formed through this process possessed irregular shapes, which is in line with the geometric properties of MPs recovered from agricultural fields. Overall, this size reduction method proved efficient for forming MPs and NPs composed of biodegradable plastics such as polybutylene adipate-co-terephthalate (PBAT), representing mulch materials used for agricultural specialty crop production.

Organosolv treatment is an environmentally friendly fractionation method that affords a lignin stream with high purity. The severity of the treatment affects the chemical composition of the generated, very complex lignin degradation product mixtures. Understanding the effects of the process severity on the types and relative abundances of the individual compounds in the mixtures is of great importance for the optimization of the treatment and the development of downstream conversion processes. In this study, seven organosolv switchgrass lignin samples prepared at different reaction temperatures and using different acid concentrations and reaction times were initially analyzed by using high-resolution mass spectrometry with negative ion-mode electrospray ionization ((−)ESI HRMS). Fast pyrolysis coupled with negative ion-mode atmospheric pressure chemical ionization and HRMS (py/(−)APCI HRMS) was also used to characterize the lignin degradation products. This method generated similar data as (−)ESI HRMS. Lignin monomers and dimers were found to constitute the majority of compounds in the mixtures. High-performance liquid chromatography coupled with (−)ESI high-resolution multistage tandem mass spectrometry (HPLC/(−)ESI HRMSn) based on collision-activated dissociation (CAD) was employed to obtain structural information for the most abundant compounds as well as a β-O-4 dimer with a relatively low abundance in the organosolv lignin samples. The relative abundances of lignin–carbohydrate complexes were found to be high under mild organosolv treatment conditions but become low under moderate and harsh treatment conditions. As lignin compounds with β-O-4 linkages are not stable under acidic conditions, the relative abundances of these compounds were found to be very low. The relative amounts of lignin monomers decreased as the treatment severity increased while the relative abundances of lignin dimers, trimers, and bigger oligomers increased, possibly due to repolymerization reactions under the harsher treatment conditions.

Biodegradable plastics can reach full degradation when disposed of appropriately and thus alleviate plastic pollution caused by conventional plastics. However, additives can be released into the environment during degradation and the fate of these additives can be affected by the degradation process. Here, we characterized TiO

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, a low value by-product of biomass fractionation, is of current particular interest for the production of value added materials such as carbon fibers within a biorefinery. Accordingly, we have isolated lignin, hemicellulose, and cellulose by organosolv fractionation of loblolly pine (Pinus taeda) under the influence different fractionation severities (2.50–3.31). A designed experimental matrix targeted maximum lignin and pulp yields and lignin glass transition temperature (Tg) as a function of several process parameters. Optimal fractionation conditions were estimated from an enhanced regression model of the statistically significant variables generated using response surface design (RSD). The most significant factor influencing lignin and pulp yields was solvent composition (p-value

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.

The concept of the integrated biorefinery is critical to developing a robust biorefining industry in the USA. Within this model, the biorefinery will produce fuel as a high-volume output addressing domestic energy needs and biobased chemical products (high-value organics) as an output providing necessary economic support for fuel production. This paper will overview recent developments within two aspects of the integrated biorefinery—the fractionation of biomass into individual process streams and the subsequent conversion of lignin into chemical products. Solvent-based separation of switchgrass, poplar, and mixed feedstocks is being developed as a biorefinery “front end” and will be described as a function of fractionation conditions. Control over the properties and structure of the individual biomass components (carbohydrates and lignin) can be observed by adjusting the fractionation process. Subsequent conversion of the lignin isolated from this fractionation leads to low molecular weight aromatics from selective chemical oxidation. Together, processes such as these provide examples of foundational technology that will contribute to a robust domestic biorefining industry.