Soil Carbon Sequestration Due to Salt-Affected Soil Amelioration with Coal Bio-Briquette Ash: A Case Study in Northeast China

Increasing soil carbon storage and biomass utilization is an effective process for mitigating global warming. Coal bio-briquettes (CBB) are made using two low-ranked coals with high sulfur content, corn stalks, and calcium hydroxide, and the combustion ash can ameliorate the physicochemical properties in salt-affected soil. CBB ash contains mainly calcium compounds, such as calcium sulfate, calcium hydroxide, and calcium carbonate, and coal fly ash and biomass ash. In this paper, changes in soil carbon and nitrogen content through salt-affected soil amelioration during 5 months using two CBB ashes and pig manure were examined in Northeast China. Application rates of CBB ash were 0 tha&minus:1 (control), 11.6 tha&minus:1, 23.2 tha&minus:1, 46.4 tha&minus:1, and 69.6 tha&minus:1. Consequently, total carbon content in topsoil (0&ndash:0.15 m) after harvest of maize in all test fields indicated a range between 27.7 tCha&minus:1 and 50.2 tCha&minus:1, and showed increased levels compared to untreated salt-affected soil. In a 3.0% (69.6 tha&minus:1) application plot of only CBB ash with higher carbon and higher exchangeable Ca2+, the carbon content increased by 51.5% compared to control plot, and changes in carbon sequestration compared to untreated soil was roughly twice that of the control plot. CBB ash contributed to carbon application and pig manure supply as a form of N fertilization in the case of all test plots. Changes in carbon content due to soil amelioration have a significant relationship with changes in corn production and soil chemical properties, such as pH, Na+, Cl&minus:, sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP). Therefore, CBB production from low-ranked coal and waste biomass, and the use of CBB ash in agriculture is advocated as an effective means for sequestering carbon.