Treatments to Improve Consistency in Properties of Rice Ash for Concrete & the Anticipated Costs, 2022


Sabbie Millerd, Dept. of Civil and Environmental Engineering, UC Davis

This project seeks to use rice straw/hull ash (RSA) as a mineral additive for concrete. It would replace fly ash, a by-product of coal burning power plants. It has been shown by this project in previous work, that RSA can be an effective substitute in concrete.

The focus of this cycle of research was to determine the economic and environmental impacts of key processes. Findings to date suggest that preparing rice straw for combustion to derive the ash as a mineral additivity for concrete has notable impact. From an economic perspective, both capital and operating costs are high. Our preliminary estimates put these at approximately $300,000 and $170,000, respectively, for rice straw ash recovery from a 200-acre rice farm. However, total revenue from ash and fertilizer that could be recovered was estimated at less than $10,000 annually for the same size farm. For greenhouse gas (GHG) emissions from producing rice straw ash, impact was just under break even with electricity and cement replacement.