Characterisation and evaluation of biochars for their application as a soil amendment

Abstract

Biochar properties can be significantly influenced by feedstock source and pyrolysis conditions; this warrants detailed characterisation of biochars for their application to improve soil fertility and sequester carbon. We characterised 11 biochars, made from 5 feedstocks [Eucalyptus saligna wood (at 4008C and 5508C both with and without steam activation); E. saligna leaves (at 4008C and 5508C with activation); papermill sludge (at 5508C with activation); poultry litter and cow manure (each at 4008C without activation and at 5508C with activation)] using standard or modified soil chemical procedures. Biochar pH values varied from near neutral to highly alkaline. In general, wood biochars had higher total C, lower ash content, lower total N, P, K, S, Ca, Mg, Al, Na, and Cu contents, and lower potential cation exchange capacity (CEC) and exchangeable cations than the manure-based biochars, and the leaf biochars were generally in-between. Papermill sludge biochar had the highest total and exchangeable Ca, CaCO 3 equivalence, total Cu, and potential CEC, and the lowest total and exchangeable K. Water-soluble salts were higher in the manure-based biochars, followed by leaf, papermill sludge, and wood biochars. Total As, Cd, Pb, and polycyclic aromatic hydrocarbons in the biochars were either very low or below detection limits. In general, increase in pyrolysis temperature increased the ash content, pH, and surface basicity and decreased surface acidity. The activation treatment had a little effect on most of the biochar properties. X-ray diffraction analysis showed the presence of whewellite in E. saligna biochars produced at 4008C, and the whewellite was converted to calcite in biochars formed at 5508C. Papermill sludge biochar contained the largest amount of calcite. Watersoluble salts and calcite interfered with surface charge measurements and should be removed before the surface charge measurements of biochar. The biochars used in the study ranged from C-rich to nutrient-rich to lime-rich soil amendment, and these properties could be optimised through feedstock formulation and pyrolysis temperature for tailored soil application.

Soil Health, Crop Productivity, Microbial Transport, and Mine Spoil Response to Biochars

“…As shown in Table 1, biochar produced through gasification of Kentucky bluegrass (Poa pratensis) seed waste (KBSW) will generally have a high ash content and alkaline pH value (pH ≈ 10). High ash content causes pH values of biochar to be >9 [26,27], thus making materials such as alkaline KBSW biochar suitable "designer biochar" for neutralizing acidic soils [28,29]. Furthermore, both biochars presented in Table 1 contain C and nitrogen (N), as well as plant macro-(e.g., Ca, P, and K) and micronutrients (e.g., Cu and Zn).…”

Biochar: Pyrogenic Carbon for Agricultural Use - A Critical Review

“…Instead of analyzing which biochar results from certain production conditions, it is already possible to define which biochar is desired and then fit the production conditions to obtain it (Mašek and Brownsort, 2010;Singh et al, 2010;Kim et al, 2012;Novak et al, 2014).…”

A bioszén felhasználásának lehetőségei a talaj tápanyag-utánpótlásában – Szemle

“…Ennek aránya a pirolízis hőmérsékletével és a folyamatban részt vevő oxigén mennyiségével nő. A nagyobb hamutartalom a bioszén pH-értékét és a mineralizált formában jelen lévő könnyen oldható elemek koncentrációját megnö-veli (SINGH et al, 2010a). A hamu frakció elemtartalma azonnal felvehető a növé-nyek és a talajlakó mikroorganizmusok számára.…”