CO2 sequestration potential over 100 years of cattle manure biochar in soil as affected by different feedstocks and pyrolysis temperatures

Cattle manure, containing lignocellulosic biomass such as sawdust, rice straw, and rice husk as bedding materials, is rich in organic matter and serves as a promising feedstock for biochar for carbon dioxide removal (CDR).However, the characteristics of manure-based biochar vary depending on feedstock composition, composting maturity, and pyrolysis temperature.This study evaluated the properties of cattle manure biochar (CMB) and 100-year carbon sequestration potential of CMB under different process conditions such as composting maturity (fresh and composted), mixing lignocellulosic biomass (sawdust, rice straw, and rice husk) and pyrolysis temperature (400C, 500C, and 600C).CMB produced showed organic carbon contents above 30% for all process conditions.However, only the composted manure pyrolyzed at 400C achieved an H/C org molar ratio 0.7, a key criterion of international biochar certification as a CDR.Pyrolysis at 500C satisfied this requirement regardless of feedstock types.The potential carbon sequestration of CMB was found to range from 0.68 to 1.67 tCO 2 -eq per ton of dry biochar, decreasing by approximately 1% for each 1 C increase in soil temperature under global warming scenario.CMB mixed with lignocellulosic biomass showed higher potential carbon sequestration compared to that without lignocellulosic biomass.At a pyrolysis temperature of 400C, the composted manure demonstrated a higher potential of carbon sequestration than fresh manure.However, this difference became negligible when the pyrolysis temperature was at 500C or higher.Therefore, this study suggested that CMB produced at pyrolysis temperatures 500 C could meet an H/C org molar ratio 0.7, with its carbon sequestration potential increasing through the mixing of lignocellulosic biomass such as sawdust, rice straw, and rice husk.