Valorization of chicken manure into biochar and compost for acidic soil amendment and lettuce productivity

The sustainable management of agricultural waste has become a global priority, particularly in regions where livestock manure poses both environmental challenges and resource opportunities. This study examines the physicochemical properties and agronomic performance of chicken manure-derived biochar as a soil amendment for acidic soils, using Lactuca sativa (Green Oak Lettuce) as a model crop. Chicken manure (CM) was converted into biochar through slow pyrolysis at approximately 500 °C. Comprehensive characterization of CM and chicken manure biochar (CMB) was performed using XRD, FTIR, SEM-EDS, and BET surface area analysis. Compared to raw chicken manure, CMB exhibited markedly higher alkalinity, porosity, and nutrient retention, along with elevated levels of potassium and phosphorus. A greenhouse experiment was conducted to assess the effects of chicken manure biochar, compost, and their combinations on soil properties and plant growth. Among the five treatment conditions, the application of a 20% combination produced the most significant improvements in both soil properties and plant performance, without causing adverse effects related to excessive salinity, pH, and heavy metals. The measured concentrations were within the reference threshold values commonly applied to agricultural amendments. Under the conditions of this short-term study, no exceedance of guideline limits was observed. The findings confirm that an optimized biochar application can effectively ameliorate acidic soils and enhance vegetable crop productivity, thereby supporting the sustainable valorization of chicken manure waste through biochar production.