Effect of covering on greenhouse gas emissions from beef cattle solid manure stored at different stack heights

Abstract: The greenhouse gases such as methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) have increased in atmospheric concentration since 1 750, attracting more and more attention regarding climate change. Agriculture activities contribute to the increase of greenhouse gas concentration in the atmosphere, resulting in a higher global warming potential, which is estimated to contribute about 47%-58% of the total anthropogenic emissions of CH4 and N2O, respectively. Storage of animal manure is reported to be a significant agricultural source of methane and nitrous oxide. Generally, greenhouse gas emissions from animal manure can be influenced by storage stacking configuration and covering during storage. However, there are large uncertainties in this estimation. In order to quantify N2O, CH4, and CO2 emissions from covered beef cattle solid manure compared with uncovered manure stored at different stack heights during storage, four treatments were designed including a stack height of 20 cm without covering (H20), a tack height of 40 cm without covering (H40), a stack height of 20 cm with a 2 cm sawdust covering (H20C), and a stack height of 40 cm with a 2 cm sawdust covering (H40C), and the treatments were replicated three times. Thus, twelve polyvinylchloride cylindrical (30 cm in diameter and 90 cm in height) static vessels were designed and built to measure greenhouse gas emissions in the laboratory experiment. The stacking process commenced on May 29, 2014, and was measured for 49 days. The results showed that manure stack height significantly affected GHG emissions from beef cattle solid manure for both manure with covering and without covering. Compared with the lower stack height (20 cm), the higher stack height (40 cm) increased 40.91% and 61.29% CH4 cumulative emissions per unit of manure weight for covered manure and uncovered manure, respectively, But it decreased by 38.06% and 35.21% N2O cumulative emissions, and 43.68% and 55.12% CO2 cumulative emissions per kg of manure weight. N2O cumulative emission from beef cattle solid manure increased significantly by using cover material regardless of stack heights, 33.87 vs. 42.32 mg/kg for 20 cm stack height and 20.98 vs. 27.42 mg/kg for 40 cm stack height, respectively. CH4 cumulative emissions from covered beef cattle solid manure (3.00 g/kg) was significantly higher than that from the uncovered treatment (2.48 g/kg) for the 40 cm stacks, but CO2 cumulative emissions from covered beef cattle solid manure was significantly lower for the 40 cm stacks, 26.42 vs. 20.20 g/kg. There were no significant difference for CH4 (1.76 vs. 1.86 mg/kg) and CO2 (46.91 vs. 45.01 g/kg) cumulative emissions from covered beef cattle solid manure compared with uncovered for 20 cm stacks. Both CH4 and CO2 are the predominant greenhouse gas emitted from solid cattle manure storage facilities. On the basis of a 100 year global warming potential for CH4 and N2O, cumulative greenhouse gas emissions were (101.07±6.28) and (94.67±3.29) g/kg of manure weight for the 20 and 40 cm stacks without cover, and were (104.20±6.78) and (103.43±3.21) g/kg of manure weight for 20 and 40 cm stack height with cover, respectively. The results suggested that beef cattle solid manure of a 40 cm stack height without covering produced the least greenhouse gas emissions.