Krishna R Reddy1Poupak Yaghoubi1Yeliz Yukselen-Aksoy1,21Department of Civil and Materials Engineerin...

1. Effects of biochar amendment on geotechnical properties of
landfill cover soil
Krishna R Reddy1
Poupak Yaghoubi1
Yeliz Yukselen-Aksoy1,2
1Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, USA
2Department of Civil Engineering, University of Dokuz Eylul, Turkey
Yeliz Yukselen-Aksoy, Department of Civil Engineering, University of Dokuz Eylul, Tinaztepe
Yerleskesi, Buca, Izmir 35160,
Turkey. Email: yeliz.yukselenatdeu.edu.tr
Abstract
Biochar is a carbon-rich product obtained when plant-based biomass is heated in a closed container
with little or no available
oxygen. Biochar-amended soil has the potential to serve as a landfill cover material that can oxidise
methane emissions for
two reasons: biochar amendment can increase the methane retention time and also enhance the
biological activity that can promote
the methanotrophic oxidation of methane. Hydraulic conductivity, compressibility and shear
strength are the most important
geotechnical properties that are required for the design of effective and stable landfill cover
systems, but no studies have
been reported on these properties for biochar-amended landfill cover soils. This article presents
physicochemical and geotechnical
properties of a biochar, a landfill cover soil and biochar-amended soils. Specifically, the effects of
amending 5%, 10% and
20% biochar (of different particle sizes as produced, size-20 and size-40) to soil on its
physicochemical properties, such
as moisture content, organic content, specific gravity and pH, as well as geotechnical properties,
such as hydraulic conductivity,
compressibility and shear strength, were determined from laboratory testing. Soil or biochar
samples were prepared by mixing

2. them with 20% deionised water based on dry weight. Samples of soil amended with 5%, 10% and
20% biochar (w/w) as-is or of
different select sizes, were also prepared at 20% initial moisture content. The results show that the
hydraulic conductivity
of the soil increases, compressibility of the soil decreases and shear strength of the soil increases
with an increase in
the biochar amendment, and with a decrease in biochar particle size. Overall, the study revealed
that biochar-amended soils
can possess excellent geotechnical properties to serve as stable landfill cover materials.
Article Notes
Declaration of conflicting interests The authors declare that there is no conflict of interest.
Funding Financial support for this project is provided by the US National Science Foundation [Grant
CMMI #1200799], which is gratefully
acknowledged.