Effects of Litter Amendment in Reducing Ammonia and Greenhouse Gas Emissions from Broiler Litter

Abstract

The United States is the largest poultry producer, consumer, and exporter of poultry products. The broiler industry constitutes 60% of the total poultry industry and produces approximately 9.17 billion broilers annually in the United States. The sector generates about 12.6 million metric tons of broiler litter (BL) annually. One of the major problems faced by poultry producers is the NH3 production inside the poultry houses. The NH3 concentration above 25 ppm harm the birds and reduces their productivity. Higher NH3 emissions also affects the environment. Besides NH3, BL is also a source of greenhouse gas emissions [GHG (N2O, CO2, and CH4)]. The higher emissions of NH3 and GHGs have environmental consequences such as global warming and climate change. Therefore, manure management becomes essential in reducing gaseous emissions into the atmosphere. Researchers have identified different methods to reduce NH3 and GHG emissions from BL. The use of amendments to reduce NH3 emissions from BL has been investigated previously; however, very few datasets exist that have reported the effectiveness of amendments to reduce GHG emissions from BL. Therefore, the objectives of this study were to evaluate the potential of biochar (B), zeolite (Z), FGD-gypsum (G), and sodium bisulfate (S) at different application rates in reducing NH3 and GHG emissions from BL. The BL samples used in the experiments were collected from the commercial poultry farms of Alabama. We conducted two experiments, one for NH3 emissions and another for GHG emissions. One hundred grams of BL samples were treated with litter amendments at four different rates, kept in mason jars, and incubated at 30 ºC for 40-days. The moisture content of BL was maintained at 40% throughout the experiment. Phosphoric acid traps were used to trap NH3 produced from BL using a 2.5 cm3 sponge. The acidified trap was prepared by dipping the sponge sequentially on 1M H3PO4, followed by 1M KOH, DI, and a mixture of 1M H3PO4 + Glycerol. The sponge was squeezed after dipping in each solution, and finally, 3 ml of 1M H3PO4 + Glycerol was added to the sponge to trap NH3, which was hung inside the jars. The trapped NH3 was extracted with 40 mL of 2M KCl solution and analyzed in a flow injection analyzer. A similar experimental setup was developed for GHG (N2O, CO2, and CH4) measurement, where GHGs samples were taken from the headspace of the jars in a pre-evacuated vial using a 10 ml syringe at 0-minute, 60-minute, and 120-minute intervals. The gas samples were analyzed using a Shimadzu Gas Chromatography equipped with a flame ionization detector (FID) and electron capture detector (ECD). The results showed that 13% and 17% B (w/w) reduced NH3 emission by 40.7 and 45.6%, respectively, compared to control. Among the different rates of Z, 8% reduced NH3 by 19.6% and 11% (w/w) reduced by 32.5%. There was no significant difference between the different rates of gypsum however, 15% G reduced NH3 by 9.1%. Application of S at rates of 2%, 4%, 6%, and 7% (w/w) significantly reduced NH3 emissions by 90.5, 98.6, 99.7, and 99.8 %, respectively, compared to control. Based on the percent reduction of NH3 emission compared to control, the efficiency of the amendments can be ranked as follows: S > B > Z > G. On the contratry, effect of amendments on GHG emissions showed a large variability in results. The application of 13% and 17% B significantly increased cumulative CO2 and N2O emissions whereas 5% and 9% B had no effect on GHG emissions compared to control. Zeolite and G application had no significant effect on GHG reduction. Sodium bisulfate at rates of 4, 6, and 7% reduced CO2 emissions by 13, 29, 32 % and N2O emissions by 33, 46, 48 %, respectively, compared to control. Among the amendments used, 4, 6, and 7 % of S were found promising for reducing GHG emissions from BL. Further studies with different combinations of amendments will provide additional insights in reducing NH3 and GHG emissions from BL. These findings contribute to ongoing efforts to identify amendments of choice for poultry producers to minimize emissions from poultry production systems as well as environmental impacts benefiting poultry, human health, and the environment.