Upgrading Biorefinery Lignin to Specialty Polymers: Environmental Performance and Economic Feasibility

Ethanol production through bioconversion of lignocellulosic materials utilizes cellulose and hemicellulose of the biomass and leaves most of the lignin part as byproduct. Due to the complexity of lignin structure, and lack of commercialized pathways for converting it to higher-value products, many current lignocellulosic biorefinery designs assume using lignin-rich byproduct for energy to reduce the facility's power needs. However, upgrading lignin to higher-value products not only can potentially boost the economic viability of a biorefinery, but it may also improve its environmental performance.

The phenolic structure and hydroxyl groups of lignin provide an advantage for lignin to be considered for replacing polymeric materials. We investigate the life cycle cost and environmental performance of using lignin in polymers with applications in coatings and composites. Lignin-based resins have displayed similar desirable characteristics to petroleum-based resins including comparable adhesion. Additionally, when used as a filler in composites, lignin can provide comparable mechanical properties. For commercialization decision, however, analyzing the environmental and cost advantage of these lignin-based materials is required.

We study the lignin-based resins supply chain and use process simulation to estimate the cost and environmental impacts of scaled-up lignin conversion to two types of resin and one filler for coating and composite applications. We compare these scenarios to lignin combustion for energy recovery. We demonstrate that in majority of the investigated environmental impact categories, the lignin-based materials show better performance than the commercial product in the market. However, for a more informed decision-making, the cost and environmental tradeoffs need to be considered.