Variability of Physical and Chemical Properties of TLUD Stove Derived Biochars

Federico Masís-Meléndez,Carlos A García-González,Jaime Quesada-Kimsey,Diana Segura-Chavarría,Karolina Villagra-Mendoza

doi:10.3390/app10020507

Federico Masís-Meléndez, Carlos A García-González + Show 3 more

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https://doi.org/10.3390/app10020507

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Abstract

Biochar is a carbon-rich organic material, obtained by the thermochemical conversion of biomass in an oxygen-limited environment, used as a soil amendment to stimulate soil fertility and improve soil quality. There is a clear need in developing countries for access to low cost, low technology options for biochar production, for example, top-lit updraft (TLUD) stoves, which are popular and spread worldwide. However, TLUD biochars are inevitably very variable in their properties for a variety of reasons. We present laboratory triplicate tests carried out on TLUD biochars obtained from waste pinewood and a Guadua bamboo. Analyzed properties include specific surface area (A-BET), porosity, skeletal density, hydrophobicity, proximal and elemental composition, cation exchange capacity (CEC), relative liming capacity and pH. SEM images of the bamboo and wood biochars are compared. The biochars were mixed with composted human excreta at 5% and 10% biochar content, and available water content (AWC) was analyzed. Operating temperatures in the TLUD were recorded, showing different behaviors among the feedstocks during the process. Differences in operating temperatures during charring of the bamboo samples seem to have led to differences in A-BET, hydrophobicity and CEC, following unprecedented trends. For the mixtures of the biochars with compost, at 5% biochar no significant differences were observed for AWC. However, in the 10% biochar mixtures, bamboo biochar showed an unexpectedly high AWC. Overall, variations of chemical and physical properties between bamboo biochars were greater, while pinewood biochars showed similar properties, consistent with more homogeneous charring temperatures.

Highlights

In recent years, there has been an increasing interest in biochar for agricultural and environmental applications
Biochar quality for soil amendment relies primarily on the volume and size of its pores and on the functional groups on the surface [4]. These aspects are driven by key factors; known as the feedstock type [5,6], the biochar particle size [7] and the pyrolysis conditions, for instance, the charring temperature, the heating rate and the residence or holding time [8]
These temperatures were recorded with thermocouples placed in the space above the charring material in the top-lit updraft (TLUD) combustion chamber

Summary

Introduction

There has been an increasing interest in biochar for agricultural and environmental applications. Sci. 2020, 10, 507 for pollutants and nutrients [3] These contributions of biochar vary with its quality. Biochar quality for soil amendment relies primarily on the volume and size of its pores and on the functional groups on the surface [4]. These aspects are driven by key factors; known as the feedstock type [5,6], the biochar particle size [7] and the pyrolysis conditions, for instance, the charring temperature, the heating rate and the residence or holding time [8]

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