Engineering Innovations, Challenges, and Opportunities for Lignocellulosic Biorefineries: Leveraging Biobased Polymer Production.

Alternative polymer feedstocks are highly desirable to address environmental, social, and security concerns associated with petrochemical-based materials. Lignocellulosic biomass (LCB) has emerged as one critical feedstock in this regard because it is an abundant and ubiquitous renewable resource. LCB can be deconstructed to generate valuable fuels, chemicals, and small molecules/oligomers that are amenable to modification and polymerization. However, the diversity of LCB complicates the evaluation of biorefinery concepts in areas including process scale-up, production outputs, plant economics, and life-cycle management. We discuss aspects of current LCB biorefinery research with a focus on the major process stages, including feedstock selection, fractionation/deconstruction, and characterization, along with product purification, functionalization, and polymerization to manufacture valuable macromolecular materials. We highlight opportunities to valorize underutilized and complex feedstocks, leverage advanced characterization techniques to predict and manage biorefinery outputs, and increase the fraction of biomass converted into valuable products.

Photodegradation of polyolefin thin films in simulated freshwater conditions.

Polypropylene (PP) and polyethylene (PE) are commonly used polyolefins in a variety of applications, which have resulted in their accumulation in the environment. Once in the environment, these polymers undergo various chemical and physical transformations as the result of environmental stressors such as sunlight. While photodegradation has been studied for decades, there are key gaps in knowledge on the phototransformations of polyolefins that occur under aqueous conditions. Therefore, the goal of this study is to characterize the phototransformations of PP and PE in simulated freshwater conditions. Polymer thin films were irradiated with 254 nm and 350 nm UV light in air, ultra-pure water, and solutions of dissolved organic matter (DOM) to simulate natural systems. Irradiated plastics were evaluated for oxidation and chain scission. It was observed using Fourier transform infrared spectroscopy (FTIR) that oxidation in aqueous environments happened at a slower rate compared to oxidations in air. However, photo-oxidation was accelerated in the presence of DOM compared to ultrapure water, with singlet oxygen and hydroxyl radical causing varied amounts of degradation depending on the polymer. The vinyl characteristic, a chain scission product, revealed an increased yield but the reaction rate showed that these photoproducts were more likely to occur when oxidation is less favorable. Compared to naturally weathered samples, lab observed transformations were on par with naturally degraded samples and support the importance of the in-lab measurements. This work quantifies the extent and rate of photodegradation pathways in PP and PE to demonstrate the importance of photodegradation in aquatic systems.