# Carbon-Negative Construction Material Based on Rice Production Residues

## TL;DR

A new carbon-negative building material is made from rice waste, offering an affordable and eco-friendly solution for housing in Africa.

## Contribution

The study introduces a scalable, carbon-negative construction material using rice production residues for low-cost housing.

## Key findings

- The composite material avoids cement use and captures CO2 during hardening.
- Field trials in Kenya confirmed structural strength and benefits like termite resistance.
- A semi-automatic system enables fast construction by unskilled laborers.

## Abstract

This study presents a cost-effective, carbon-negative construction material for affordable housing, developed entirely from locally available agricultural wastes: rice husk ash, wood ash, and rice straw—materials often problematic to dispose of in many African regions. Rice husk ash provides high amorphous silica, acting as a strong pozzolanic agent. Wood ash contributes calcium oxide and alkalis to serve as a reactive binder, while rice straw functions as a lightweight organic filler, enhancing thermal insulation and indoor climate comfort. These materials undergo natural pozzolanic reactions with water, eliminating the need for Portland cement—a major global source of anthropogenic CO2 emissions (~900 kg CO2/ton cement). This process is inherently carbon-negative, not only avoiding emissions from cement production but also capturing atmospheric CO2 during lime carbonation in the hardening phase. Field trials in Kenya confirmed the composite’s sufficient structural strength for low-cost housing, with added benefits including termite resistance and suitability for unskilled laborers. In a collaboration between the University of Tartu and Kenyatta University, a semi-automatic mixing and casting system was developed, enabling fast, low-labor construction of full-scale houses. This innovation aligns with Kenya’s Big Four development agenda and supports sustainable rural development, post-disaster reconstruction, and climate mitigation through scalable, eco-friendly building solutions.