Potential of the biochar derived from agricultural waste residues for peat replacement in horticultural growing mediums

Protected agriculture plays a vital role in increasing food production while minimizing the adverse effects of weather conditions and land limitations. Due to these barriers, soilless plant culture in greenhouse facilities is becoming a trend among farmers. As a result, a substantial amount of waste is generating from greenhouse crop production. Spent growing medium waste wrapped with plastic grow bags is one such waste stream. Mismanagement of this waste creates risk towards the ecosystem. On the other hand, peat is abundantly used as a growing medium component in horticulture due to its favorable qualities as a growing medium component. However, unsustainable peat extraction could lead to greenhouse gas emissions and the degradation of peatlands. Therefore, there is a need to find a sustainable alternative to peat use in horticultural growing media. Under this context, the potential application of biochar in horticulture as a growing medium component to substitute or replace peat was analyzed. In this context, two types of biochars were produced using spent growing medium waste with and without the addition of plastic grow bags sample into the feedstock (BC and BCP). After that, the effectiveness of those two biochar samples on plant growth (Tagetes patula) and physicochemical properties of horticultural growing mediums were examined. Although the addition of BC and BCP increased the pH and EC of growing media, concentrations of PTEs could be kept under the threshold values. The hydrophysical properties of growing media formulations were changed after the addition of biochar. BC and BCP had better particle size distribution and increased the air-filled porosity of the growing media formulations. The plant experiment showed that BC and BCP added treatments had improved performance compared to the control based on the growth parameters of the plants. The addition of plastic in the feedstock for producing BCP did not give any significant impacts on the properties of the growing medium and plant growth