Temperature Effects on Properties of Rice Husk Biochar and Calcinated Burkina Phosphate Rock

Vincent K. Avornyo, Andrew Manu, David A. Laird and Michael L. Thompson
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Vincent K. Avornyo: Department of Soil Science, University for Development Studies, Tamale P.O. Box TL 1882, Ghana
Andrew Manu: Department of Agronomy, Iowa State University, Ames, IA 50011-1051, USA
David A. Laird: Department of Agronomy, Iowa State University, Ames, IA 50011-1051, USA
Michael L. Thompson: Department of Agronomy, Iowa State University, Ames, IA 50011-1051, USA

Agriculture, 2021, vol. 11, issue 5, 1-13

Abstract: Rice husk biochar (RHB) and phosphate rock (PR) are locally accessible resources that poor farmers in Sub-Saharan Africa (SSA) can utilize to increase rice productivity. However, biochars are variable depending on feedstock, pyrolysis temperature, and duration. Phosphate rocks from SSA are of low solubility. The goal of this study was to determine whether pyrolysis of rice husk (RH), calcination of PR, and the calcination/pyrolysis of a RHB-PR mixture at 300 °C, 500 °C, and 700 °C can increase formic acid (FA)- extractable phosphorous (P). The properties of these RHBs were compared to the properties of RHB produced through a simple farmer-friendly pyrolysis technique termed “Kun-tan”. Properties of calcinated PR were also compared to the raw PR. Quartz formed from amorphous SiO 2 during RH pyrolysis and was the dominant mineral phase in the biochars, irrespective of the pyrolysis temperature. Formic acid-extractable P content, pH, and ash content of the biochars increased with increasing pyrolysis temperature. At 700 °C, FA-extractable P content of the RHB was 219% more than the feedstock. Hydroxyapatite and quartz were the dominant minerals in the PR irrespective of calcination temperature, indicating that hydroxyapatite and quartz were stable to at least 700 °C. Rather, calcination decreased the FA-extractable P content of the PR.

Keywords: rice husk biochar; phosphate rock; phosphorous; quartz; hydroxyapatite (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2021
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