Ammonia and Greenhouse Gas Emissions from Biogas Digester Effluent Stored at Different Depths

Abstract

Carbonaceous and nitrogenous gases are produced during storage of livestock manure, with the magnitude of production being affected by the chemical properties of the manure and the physical conditions of storage. This lab-scale study quantifies the emission rates of ammonia (NH3), nitric oxide (NO), and greenhouse gases (GHG), i.e., methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), from biogas digester effluent (BDE) stored at different depths of 1.0, 1.5, and 2.0 m in dynamic emission vessels (DEVs). The selected storage depths were reflective of the typical depth range of on-farm BDE storage in China. The static storage was held at a relatively constant media temperature of 15°C and an air exchange rate of 11.5 air changes per hour (ACH) for 78 days. Each depth regimen was replicated four times using four DEVs (12 DEVs total). The results showed that the mean (±SE) daily gaseous emission rates per volume of BDE stored at 1.0, 1.5, and 2.0 m depths, in g gas m-3 d-1, were, respectively, 9.1 (±0.7), 10.1 (±0.6), and 10.1 (±0.4) for CH4 (p = 0.39); 38.0 (±2.2), 34.5 (±1.3), and 30.7 (±0.6) for CO2 (p < 0.05); 1.9 (±0.11), 1.3 (±0.08), and 0.9 (±0.03) for NH3 (p < 0.05); and 6.7 (±0.5) × 10-3, 5.0 (±0.8) × 10-3, and 3.4 (±0.2) × 10-3 for N2O (p < 0.05). Nitric oxide (NO) emissions were negligible. The overall GHG (CH4 + N2O + CO2) emissions were dominated by CH4, which accounted for more than 85% of the CO2-equivalent emissions for all three storage depths. The CH4 emissions peaked during the early storage period, with the first 20-day cumulative emissions accounting for 56% to 58% of the total 78-day storage emissions. The results reveal that storage of BDE at 2.0 m depth yielded lower CO2, NH3, and N2O emission rates but similar CH4 emission rates compared to the 1.0 and 1.5 m depths.

Composition and Toxicity of Biogas Produced from Different Feedstocks in California

“…Another important GHG formed during the life cycle of organic waste management is nitrous oxide (N 2 O). N 2 O is known to account for more than 20% of the total global warming potential (100 year scale) associated with GHGs emissions from organic waste storage practices, , but N 2 O is unlikely to form in the anaerobic digestion process that produces biogas …”

The Characteristics of Carbon, Nitrogen and Sulfur Transformation During Cattle Manure Composting—Based on Different Aeration Strategies

“…Concentrations of CH 4 , CO 2 , N 2 O, NO, SO 2 , and H 2 S gases of fresh and exhaust air were automatically measured and recorded. With a known aeration rate, the gaseous emission fluxes from the compost reactors were calculated using the following equation [29]:ERi=(Cout_i−Cin_i)×VR×0.001×60×24 where ERi is the mean emission flux on day i (mg·m −3 ·d −1 ), Cin_i is the gas concentration of inlet air on day i (mg·m −3 ), Cout_normali is the gas concentration of outlet air on day i (mg·m −3 ), VR is the aeration rate (L·min −1 ·m −3 ), 0.001 is the conversion factor from L to m 3 , 60 is the conversion factor from min to hour, and 24 is the conversion factor from hour to day.…”