What question did this study set out to answer?

To investigate CO2 and ethanol emissions during microbial respiration in silage and their environmental implications.

March 2, 2026Open Access

Determining characteristics of CO2 and ethanol emissions from microbial respiration in silage by partitioning of aerobic/anaerobic metabolites

Key Points

To investigate CO2 and ethanol emissions during microbial respiration in silage and their environmental implications.
Developed a multi-sensor instrument to monitor CO2 and ethanol emissions from silage.
Monitored oxygen concentration to distinguish metabolic sources.
Conducted fermentation experiments with maize and ryegrass in glass jars for up to 600 hours.
Analyzed silage temperature and pH to determine aerobic stability and microbial activity.
Initial emissions of CO2 and ethanol primarily resulted from anaerobic metabolism.
CO2 emissions shifted from anaerobic to a mix of aerobic and anaerobic sources as stability changed.
Time lags of about 40 hours for maize and 100 hours for ryegrass were observed between CO2 and ethanol emissions during instability.

Abstract

To investigate potential pollution of silage production to environment, we developed a multi-sensor-based instrument for tracking of carbon dioxide (CO 2 ) and ethanol (EtOH) emissions from feed-out silage, incorporated real-time monitor of oxygen (O 2 ) concentration to distinguish different metabolic sources, and combined measurements of silage temperature (T si ）and pH to identify aerobic-stability and microbial-activity. Two common silage materials (maize and ryegrass), as experimental mini-silos treated either with or without a commercial bio-additive, were fermented in 1.5-L glass jars. The test, started immediately exposing samples to air, lasted 320 h (maize) or 600 h (ryegrass). The achieved data demonstrate: (i) all samples underwent from aerobic-stable to unstable processes; (ii) the initial emissions of CO 2 and EtOH (0 ~ 10 h of aerobic-stable period) yielded mainly from anaerobic metabolism (maize, CO 2 : 1.104 1.294, EtOH: (0.570 0.807) × 10 -2 ; ryegrass, CO 2 : 0.805 0.888, EtOH: (0.060 0.408) × 10 -2 , unit: mol m -2 ), the end-products of preceding fermentation by heterofermentative lactic acid bacteria (LAB) and subsequently accumulated in the sealed jars; (iii), after samples became unstable, the emission of CO 2 represented a mixture of aerobic and anaerobic metabolites, whereas EtOH was anaerobic one, both compounds by yeasts; and (iv) time lags (maize: ca. 40 h, ryegrass: ca. 100 h) between CO 2 and EtOH emissions were observed during the aerobic-unstable period. These findings contribute to our understandings of aerobic deterioration in silage and resulting pollution to air, providing supports for optimization of on-farm silo management to minimize the gas/VOC emissions from silage production. • Multi-sensor-fusion innovation to track CO 2 and ethanol (EtOH) emissions from silage • In situ O 2 -trace classification of aerobic (CO 2 ) and anaerobic (Ethanol) metabolites • Emission characteristics of CO 2 and EtOH determined from maize and ryegrass ensiling • EtOH is an anaerobic metabolite but can be produced by yeast during silage feed-out • Maize/Grass initial-emit: CO 2 1.1 1.3, 0.8 0.9; EtOH (0.6 0.8, 0.1 0.4)×10 -2 , mol m -2

Determining characteristics of CO2 and ethanol emissions from microbial respiration in silage by partitioning of aerobic/anaerobic metabolites

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Abstract

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