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.

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With the rapidly changing needs of the construction industry and higher education, Conceive—Design—Implement—Operate (CDIO) educational framework is essential in delivering basics and practical aspects to undergraduate students. This study presents an attempt to explore the use of hardware and software applications for geotechnical engineering education. An example for development of hardware (Arduino UNO) and software applications (Mobile applications) for estimating soil moisture and its regulation is presented. The study provides a new learning environment, where students from civil engineering (major) can work hand to hand with that from electronics (minor) to develop applications for soil moisture measurement. A collaborative workshop is proposed and executed. The workshop includes basic concepts related to hardware (Time domain reflectometry [TDR] probe, Arduino UNO, and Water flow measurement) and software (LabVIEW and Android studio programming platforms) followed by project implementation in a group of 5–6 students. Satisfaction and comprehension were found to increase significantly for subjects (electronics and optics) to students of civil engineering background. The adopted tools represent economical means for application in conventional classrooms as well as laboratories for undergraduate students with a civil engineering background. This integration of the digital and physical world is an attempt at approaching soil mechanics mathematics from technology and arts from a scientific perspective. The examples presented in this study can be useful for developing open‐source laboratories within the framework of the undergraduate curriculum in civil engineering.

Microwave-assisted pyrolysis (MAP) is considered as one of the improved biochar production options given its cost efficiency, efficient heat transfer and better-quality control. Researchers have observed that biochar can be considered as an alternative erosion control material due to its high porosity, surface area, and surface functional groups. However, as per the available literature, contradictions exist regarding some erosion control mechanisms of biochar with respect to water holding capacity (WHC), bulk density, and aggregate formation. Further, there is a lack of exploration as to how biochar produced using MAP can be adopted for erosion control. The objective of this study is to critically review existing literature on the usage of biochar for erosion control in various types of soils. In addition, the use of the MAP technique for producing biochar for erosion control is explored. Based on the review, the available experimentation research is generally of short duration with the least consideration of the long-term ageing effects of biochar. The studies on erosion control using biochar have been mostly conducted in the shallower zone (i.e., within 20 cm). The effect of different types of biochars on various soils does not seem to have been investigated systematically. It has been observed that the mechanism of washing away biochar particles and nutrients is rarely taken into account while measuring erosion. Further, the comparative analysis of biochar types produced from various feedstocks, including their physiochemical properties, is rarely explored for their applications in soil erosion. This study aims to critically analyze available literature for the erosion suppressing mechanism of biochar, limitations and the feasibility of microwave-assisted biochar production for the purpose of soil erosion control.

The influence of biochars on water retention, mitigating nutrient leaching, and pollutant removal in green infrastructure has been explored in the past. However, there is a lack of understanding on how feedstock (i.e., biomass) would affect biochar physicochemical properties and hence, overall erosion control (including infiltration, surface, and sub-surface runoff) in green infrastructure. The main purpose of this study was to investigate the effect of biochars produced from three different feedstocks (pig manure, wood, and kitchen waste) on the erosion of granite residual soil. Flume experiments were conducted to measure and analyze soil erosion, runoff, and infiltration. The result showed that the runoff and soil erosion of kitchen waste biochar (KWB) samples were reduced by 17.7% and 21.7%, respectively. On the contrary, wood biochar (WB) and pig manure biochar (PMB) were found to enhance runoff and soil erosion. In addition, biochar particles were found in runoff and infiltration in erosion experiment. Thus, it is important to note that measures should be taken to prevent biochar loss when using biochar as a soil amendment. Additionally, the effects of different types of biochar on soil hydraulic and hydrophobicity properties should be taken into account as a selection criterion for choosing amendments in green infrastructure. This study finds that kitchen waste biochar has better performance in improving soil hydraulics and erosion.

The present study focuses on the effect of root density on gas permeability and water retention in biochar‐amended soil used as a cover material in landfills. Biochar amendment of soil is important measurement in landfill cover, while vegetation is an important for ecological restoration. Despite its importance, little attention has been given to the adaptation of vegetated biochar‐amended soil in landfill cover. The interactions between the biochar, vegetation, and soil concerning the gas permeability remain unknown, which may lead to unexpectedly increased waste gas emissions in landfill covers. To enhance the utilization efficiency of biochar amendment and vegetation techniques in landfill covers, further investigation of their coupled effects on gas permeability and water retention is necessary. Four different treatments were applied to manufacture series of soil columns: bare soil (BS), biochar‐soil composite (BSC), vegetated biochar‐soil composite with low planting density (VBSCL) and high planting density (VBSCH). The soil water characteristic curve and gas permeability were observed under natural wetting and drying cycles. The results showed that VBSCL increased gas permeability by 142% as compared to BSC. VBSCH enhanced gas permeability by 168% as compared to BSC. This was due to the spreading and decaying root systems forming preferential pathways for gas transfer. Additionally, VBSCL and VBSCH made around a 10% increase in volume water content at the whole suction range, while BSC just enhanced around 20% water content at the low suction range (less than 10 kPa). The combination of roots and biochar have significantly enhanced water retention during entire suction range due to capillarity.

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