Characteristics and nutrient values of biochars produced from giant reed at different temperatures

To investigate the effect of pyrolysis temperature on properties and nutrient values, biochars were produced from giant reed (Arundo donax L.) at 300-600 degrees C and their properties such as elemental and mineral compositions, release of N, P and K, and adsorption of N and P were determined. With increasing temperatures, more N was lost and residual N was transformed into heterocyclic-N, whereas no P and K losses were observed. P was transformed to less soluble minerals, resulting in a reduction in available-P in high-temperature biochars. A pH of <= 5 favored release of NH4+, PO43- and K+ into water. Low-temperature biochars <= 400 degrees C) showed appreciable NH4+ adsorption (2102 mg kg(-1)). These results indicate that low-temperatures may be optimal for producing biochar from giant reed to improve the nutrient availability. (C) 2012 Elsevier Ltd. All rights reserved.