Collaborative Research: Designing Drop-In Solid Biofuel Blends via Harmonization Across Combustion and Fuel Science

About This Grant

The U.S. pellet market is worth almost $9 billion. The majority of pellets are made from hardwood processing waste, and their applications are limited to heating and energy generation. Biomass-based pellets could replace coal in some industrial settings if they can achieve a higher energy density and strength than wood-based pellets. Converting low-cost, regionally available materials such as food processing waste and fast-growing crops into high-value solid fuels could enhance rural energy independence. However, designing biobased combustible fuels as drop-in substitutes for coal requires advances in fundamental energy science. This project will use experiments and process design to overcome limitations with single char-based solid fuels and design drop-in fuel mixtures that optimize properties between various biomasses. The project will bring together stakeholders from academia, industry, and government to explore implications of bioenergy. Project outcomes will help the U.S. become a leader in biobased fuels. Hydrothermal Carbonization (HTC) is an efficient way to produce solid biofuels from wet wastes. Yet hydrochars (HCs) do not combust like the coal they are thought to replace, owing to the presence of secondary char (SC), a tarry material that forms during HTC. This project will design true drop-in solid biofuels by aligning carbonization levels between hydrochars and torrefied biochars (BCs) to reduce fuel segregation and increase thermal stability and energy density of HC-only fuels. The SC present on HCs may serve as a pellet binder, improving hydrophobicity and tensile strength, but it will alter ignition and burning characteristics due to its higher reactivity and lower porosity. By integrating fuel and combustion science, the project team will develop rapid thermogravimetric analysis-based assessment method to predict key combustion behaviors (ignition delay, ignition mode, combustion mode, burning rate) and how SC impacts these behaviors. Through the development of a statistical model the team will determine the optimal SC composition and HC-BC blend ratios. The project will promote economic diversification in rural areas of the US by identifying key characteristics of feedstocks that optimize biomass-to-fuel conversion and utilization. Three key audiences are targeted in research translation activities to support a Resilient Rural Economy: students in the laboratory and in engineering Capstone Design courses; researchers across the fuel and combustion communities; regional stakeholders from industry, academia, and government. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.