Characterizing Corn and Cattle Manure Derived Biochars Relevant to Their Use as Soil Additives

Biomass-derived biochars have shown potential for improving soil properties as a whole that are conducive to plant growth with reduced environmental pollution. Four types of biomass, namely, corn stover (CS), dried distillers’ grains and solubles (DDGS), dairy manure (DM), and beef feedlot manure (BFM), were transformed to biochar through pyrolysis at 400°C with 1, 2, or 3 h residence time. The biochars were characterized by proximate analysis (volatile matter (VM), ash, and fixed carbon (FC)), ultimate analysis (total carbon (TC), hydrogen (H), nitrogen (N), sulfur (S), and oxygen (O)), and thermogravimetric analysis (pH, electrical conductivity (EC) and bulk density (BD)). Scanning electron microscopy (SEM), energy dispersion spectroscopy (EDXS), and Fourier transform infrared radiation (FTIR) spectroscopy were used to categorize pore size, functional groups, and mineralogical properties related to potential use in environmental remediation. The highest heating value (HV) was measured with CS (28 to 29 MJ kg-1), and the lowest HV was measured with BFM (~5 MJ kg-1). The greatest organic carbon (OC) content was obtained with CS (68%), followed by DDGS (63%), DM (44%), and BFM (15.4%) biochars. The SEM images showed the macrocellular morphology of the original shape of the biomass particles, which consisted mainly of aggregate microspheres 2 to 10 µm in size. The surface functional groups of all four biochars were dominated by hydroxyl, methyl, methylene, aromatic carbonyl/carboxylic, and alkene groups. The CS and DDGS biochars showed higher TC (76%), FC (61%), OC (67%), water holding capacity, and mineral contents and outperformed the DM and BFM biochars as the best soil amendments. Keywords: Beef feedlot manure, Corn stover, Dairy manure, Dried distillers’ grains and solubles.