Effects of pyrolysis temperature, feedstock type and compaction on water retention of biochar amended soil

He Huang,Peinan Chen,Xilong Huang,Peng Lin,Ankit Garg,Peiying Wang,Yuantian Zhang,Yuanxu Huang,Narala Gangadhara Reddy

doi:10.1038/s41598-021-86701-5

He Huang, Peinan Chen + Show 7 more

Open Access

https://doi.org/10.1038/s41598-021-86701-5

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Abstract

Recent studies on water retention behaviour of biochar amended soil rarely considers the effect of pyrolysis temperature and also feedstock type into account. It is well known that pyrolysis temperature and feedstock type influences the physical and chemical properties of biochar due to stagewise decomposition of structure and chemical bonds. Further, soil density, which is in a loose state (in agricultural applications) and dense (in geo-environmental engineering applications) can also influence water retention behaviour of biochar amended soils. The major objective of this study is to investigate the water retention properties of soil amended with three different biochars in both loose and dense state. The biochars, i.e. water hyacinth biochar (WHB), chicken manure biochar (CMB) and wood biochar (WB) were produced in-house at different pyrolysis temperature. After then, biochars at 5% and 10% (w/w%) were amended to the soil. Water retention behaviour (soil suction and gravimetric water content) was studied under drying and wetting cycle simulated by varying relative humidity (RH, 50–90%). Results show that 10% WHB produced at 300 °C were found to possess highest water retention. CMB is found to possess higher water retention than WB for 10% amendment ratio. In general, the addition of three biochars (at both 300 °C and 600 °C) at 10% (w/w) significantly improved the water retention at all suction ranges in both loose and dense compaction state as compared to that of the bare soil. The adsorption (wetting) and desorption (drying) capacity of biochar amended soils is constant at corresponding RH.

Highlights

CBC Unit cost of biochar per ton CFEEDSTOCK Cost of feedstock for per ton biochar CPRODUCTION Cost of per ton biochar pyrolysis CEXTRA Cost per ton of transportation and so on SS Sum of squares
It can be observed that the biochar yield produced at 300 °C temperature is higher than the biochar produced at 600 °C irrespective of the type of feedstock type
The current study presents a novel viewpoint by analysing water retention property (i.e., soil water characteristic curve (SWCC)) for loose and compacted soils amended with biochars produced at different pyrolysis temperature and feedstock

Summary

Introduction

CBC Unit cost of biochar per ton CFEEDSTOCK Cost of feedstock for per ton biochar CPRODUCTION Cost of per ton biochar pyrolysis CEXTRA Cost per ton of transportation and so on SS Sum of squares. The moderate heating rate during slow pyrolysis generally leads to the breakdown of weaker bonds while tending to retain stronger bonds[8] Such a rearrangement reaction promotes the structural stability of solid biochar. The sorption and desorption properties of biochar amended soil mainly depend on available pore spaces in the soil matrix, which can be controlled by the compaction state (loose and dense). These properties depend on the feedstock type, and pyrolysis temperature[27,28,29,30]. Based on the thermodynamic relationship, for a known temperature and relative humidity for each time interval, the total suction of the sample can be calculated by Kelvin equation using Eq (1)[34]

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