Exploring effects of novel chemical modification of biochar on soil water retention and crack suppression: towards commercialization of production of biochar for soil remediation

Recently, incentives have been provided in developed countries for promoting commercialization of biochar production for usage in construction industry. One of the main reasons for such incentives is the carbon sequestration capacity of biochar, which can be highly useful for countries to meet their goals of carbon emission reduction by 2030. In this regard, chemical modification of biochars has also been done to enhance their surface area and functionality, which is useful for adsorption of pollutants. However, rarely any studies are conducted to explore the effect of chemical treatment of biochar on soil cracking and water retention. The major objective of this study is to explore the crack and water retention properties of chemically modified biochar amended soil. Pig manure biochar (PMB) and peach shell biochar (PSB) with contrasting compositions were modified with H3PO4 and KOH. Soils were mixed with modified biochars at four dosages (0, 2, 5, and 8%). Crack intensity factor (CIF) and moisture content were measured during drying-wetting cycles. Results showed that H3PO4-modified biochar has been found to have a higher impact on water retention as compared to KOH-modified biochar. KOH modification instead tends to reduce hydrophilic functional groups on surface of biochar. Pig manure biochar appears to have a higher crack suppression capacity than even functional biochars. In most cases, 5-8% biochar dosage is generally found to be an optimal range for reducing cracks and improving water retention. Based on the given testing conditions, the effect of chemical modification of biochar on cracking appears to be inconclusive. It should be noted that the results in this study are based on a given testing conditions and generalization requires further studies on different types of soils.