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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Bioproducts Research » Research » Research Project #435720

Research Project: Continuous Torrefaction of Walnut Shells: Scale-up and Characterization for Optimal Commercial Applications

Location: Bioproducts Research

Project Number: 2030-41000-058-21-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Oct 1, 2018
End Date: Sep 30, 2019

California walnut producers have seen a significant reduction in their returns on shells due to excess supply, with few viable commercial outlets. To expand market opportunities, USDA researchers, along with several commercial partners, have explored thermal conversion of shells in a process called torrefaction as a means to create plastic additives. Test applications have included use in commodity plastics, in tire formulations, as “activated carbon” for filter devices, and as biochar for soil amendment. While prototypes have been made at the lab-scale, work is needed to scale-up and optimize production as quickly as possible. The aim is to provide commercially-viable torrefied shells into new market applications. Our objectives are to 1) produce viable biochars from shells on a continuous basis at the pilot-scale, 2) create prototype commercial products using torrefied shells as additives and enhancers, and 3) present prototype materials to industrial partners for their review.

We will then examine the effects of temperature, time (residence time in the furnace) and size of output particles (grind mesh) as well as the effect of grinding samples before or after thermal treatment. Basic measurement of the biochars’ output properties will include product yield, particle size, moisture uptake and color. We will create prototype commercial products using biochar from shells and then present prototype materials to industrial partners for their review.