Adsorption Technologies for Sustainable Reduction of CH4 and CO2 from Agricultural Livestock

Ruminants, mainly dairy cattle, are widely recognized as one of the main contributors to methane emissions in the environment, playing a significant role in the global warming phenomenon. Considering that a cow emits about 500 L/d of methane 1 and in view of the increasing population of cows due to the intensive farming activities, the daily methane emission is considerable. Extensive efforts have been made to reduce methane emissions from ruminants prior to their release into the environment; however, considering that the enteric fermentation process is unavoidable, it is crucial to establish methods for capturing the emitted methane. Given the common practice of implementing forced ventilation within barns for animal well-being, the discussed process aims to capture methane via adsorption on zeolite through the barn ventilation. The literature review has identified commercial zeolite 13X and Clinoptilolite as suitable materials. The Adsorption isotherms of the gases on the selected adsorbent materials were taken from the literature and are being currently validated through experiments. It is estimated that a cattle (600 kg of body weight) consumes 21 kg DMI /day and due to the enteric fermentation and respiration releases 23 g CH4 / kg DMI and 647 g CO2 / kg DMI 2. Carbon dioxide poses a significant challenge for methane capture on zeolite, because adsorption competition exists between CO2 and CH4. Therefore, it is suggested that the adsorption process is dominated by the carbon dioxide adsorption. The design work, performed using Aspen Adsorption® V11 software, revealed the necessity of a two-stage adsorption system, with two beds in series. An initial “guard bed” filled with zeolite 13X is used to adsorb carbon dioxide and other gases from the barn, while efficiently adsorbing methane in the second bed of the same volume filled with Clinoptilolite, a cost-effective natural zeolite with excellent properties for methane adsorption. With the current configuration, the first bed reaches saturation in 210 days whereas the second bed reaches saturation in 40 days; consequently, five replacements need to be executed while keeping the guard bed in operation. The designed plant allows to obtain an exiting flow consisting only of air, therefore mitigating the environmental impact of the agricultural sector. References: [1] K. A. Johnson, D. E. Johnson, Journal of Animal Science 1995, Volume 73, 2483 – 2492. [2] A. Jonker, L. J. Farrell, Animal Production Science 2019, Volume 6, initial 1063 – 1069. Acknowledgments This study was carried out within the Agritech National Research Center and received funding from the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022).