Greenhouse gas and volatile organic compound emissions of additive-treated whole-plant maize silage: part A—anaerobic fermentation period

Background Silage emits climate- and environment-relevant gases during fermentation and feed-out periods. This trial aimed to determine the unknown carbon dioxide (CO 2 ), methane, nitrous oxide, ethanol, and ethyl acetate emissions of constant maize silage material over both periods. The results will be published in two consecutive articles (Part A: anaerobic fermentation period, Part B: aerobic storage period). Methods The untreated control (CON) was compared with the chemical additive treatment (CHE; 0.5 g sodium benzoate and 0.3 g potassium sorbate per kg fresh matter) and the biological additive treatment (BIO; 10 8 colony-forming units (CFU) Lentilactobacillus buchneri and 10 7 CFU Lactiplantibacillus plantarum per kg fresh matter). Barrel silos ( n = 4) were connected to gas bags to quantify gas formation during anaerobic fermentation (30 or 135 ensiling days). Glass jar silos ( n = 12) were used for laboratory silage analysis. Results CHE produced significantly ( p < 0.05) less gas (6.7 ± 0.3 L per kg dry matter ensiled material (kg DM ) until ensiling day 14.0 ± 0.0) and ethanol (8.6 ± 1.5 mg kg DM –1 ) than CON did (8.5 ± 0.2 L kg DM –1 until ensiling day 19.5 ± 6.4; 12.2 ± 1.5 (mg ethanol) kg DM –1 ). BIO indicates prolonged gas formation (9.1 ± 0.9 L kg DM –1 until ensiling day 61.3 ± 51.9; 12.0 ± 2.1 mg kg DM –1 ). CO 2 is the main component of the gas formed. All treatments formed methane and nitrous oxide in small quantities. CON emitted significantly more CO 2 eq emissions than BIO and less than CHE ( p < 0.05). Additives had no effect on ethyl acetate gas emissions. For BIO, ethanol concentrations in the material ( r S = 0.609, p < 0.05) and gas quantities ( r S = 0.691, p < 0.05) correlate with ethyl acetate gas quantities. All the treatments exhibited decreasing gas and CO 2 quantities, and the dry matter mass increased between ensiling days 14 and 30 (− 0.810 ≤ r S ≤ 0.442; p < 0.05 to p = 0.20). Conclusion Silage generates climate- and environmental-relevant gases during fermentation and silage additives affect this pattern. Gas formation exceeds the fixation potential, and the carbon footprint of silage fermentation is negative.