UC Merced

The combination of recent drought conditions, closing of biomass processing plants, increased open-burning permit costs, and current practices of agriculture and forest management have created an abundant amount of biomass that is causing increased green house gas (GHG) emissions and potential for catastrophic wild fires. This has motivated the search for innovative solutions for the usage of biomass and its byproducts.

Activated carbons are highly valuable products with endless applications in the food and pharmaceutical industries, among others. While the conventional (physical) activation process involves exposing biochar to superheated steam, the addition of electric fields is being analyzed as an innovative alternative to the energy-intensive physical activation process. The application of an electric field creates a plasma discharge in the gases and induces Joule heating in the carbonaceous material. The main objective of this dissertation is to investigate the dynamics of charge/Joule heat transport and thermal runaway. The purpose is to induce thermal breakdown (high temperatures) in biomass, biochar, and graphite with low energy input and in short amounts of time. This concept was explored through numerical simulation using an electric-thermal model and two variations of a hydrodynamic model, which were developed as part of this work. Results show that Joule heating indeed produces high temperatures in the order of seconds for wood, and in fractions of a second for biochar and graphite -- with low energy input.

A second objective is to produce and assess activated carbons derived from agricultural residues and forest woody biomass. In this work, physical activation of peach pit biochar was explored. BET surface areas up to nearly 600 m^2/g were obtained. Though these values are significant, they are still lower than those of commercial activated carbons (>1000 m^2/g). However, these are promising results, especially, because these materials have the potential to be used in industrial filtering applications, not only in soils, as is mainly the case for raw biochar. Moreover, in addition to providing a new market for biomass utilization, biochar and activated carbon provide a stable method for capturing and sequestering carbon.