Climate change poses a significant challenge, impacting human life globally, the environment, and economic development. It particularly affects the alteration of seasons, natural disasters, extinction of species, and the shifting pattern of pathogens and disease carriers. The primary contributors to climate change are greenhouse gases, predominantly carbon dioxide (CO2) and methane (CH4), originating mainly from human economic activities. This phenomenon also serves as a major catalyst for more frequent and severe natural disasters, resulting in substantial loss of life, property, and significant economic and social repercussions, especially at the community and local levels where disaster response capacity is limited.

   What are we trying to solve

In 2015, the international community collaborated to address this issue and formulated the Paris Agreement, aimed at controlling the rise in the world's average temperature, enhancing adaptability, and fostering recovery from climate change impacts. Thailand ratified the agreement on September 21, 2016. Presently, methane concentrations in the atmosphere are 2.5 times higher than pre-industrial levels, with 40 percent originating from natural sources and the remaining 60 percent from human activities, particularly agriculture, specifically from livestock farming.

Efforts have been made to capture and utilize methane from livestock farming as biomethane, an alternative renewable fuel. However, the combustion of biomethane, while preventing methane release, still produces carbon dioxide, thereby not entirely addressing greenhouse gas emissions. Recognizing this, there is a need to explore solutions to reduce carbon dioxide emissions resulting from methane combustion in livestock farms, aiming for carbon neutrality to combat climate change, improve quality of life, and potentially create carbon credits through technologies like carbon capture and utilization, such as the Hybrid Na-CO2 System, which converts carbon dioxide into hydrogen. This approach holds promise for transforming the environmental impact of livestock farming.


   Anthropogenic sources and agricultural sources
Approximately 60 percent of methane (CH4) emissions released into the atmosphere are a result of human activities, specifically categorized as anthropogenic sources. The primary contributor to these emissions is agriculture, particularly from the fermentation processes occurring in the digestive systems of livestock, a phenomenon known as Enteric Methane. This issue is particularly pronounced in cattle farms, standing out as the foremost source of methane (CH4) emissions, accounting for 32 percent of the total methane (CH4) emissions. This information is sourced from the International Energy Agency's report in 2021.
Although the use of biogas may have been an efficient way to deal with methane gas which is the byproduct for agriculture, the combustion process still creates a significant amount of CO2. Therefore, using carbon capture technology, along with the Hybrid Na-CO2 system, we can mitigate both the methane and CO2 production from dairy cows.
   Methane gas

When fermenting cow dung, apart from producing methane gas, other gases such as hydrogen sulfide (H2S) are also generated. As a result, the gases obtained from fermentation must undergo the Biogas Scrubber process to filter and retain only methane gas (CH4). The quantity of gas generated is influenced by various factors including food quality, management practices, and environmental conditions.

Recognizing that methane gas (CH4) is a potent greenhouse gas, efforts have been made to address this concern. A method has been devised to efficiently and safely eliminate methane gas, aiming to mitigate its environmental impact.

Currently, there is ongoing discussion about the practical uses and safety considerations of methane gas. It can serve as a fuel for various daily activities and is also capable of generating electricity. Moreover, methane gas can be utilized in cooking without posing harm, depending on the location. It is crucial to note that burning methane gas (CH4) in a confined space is hazardous due to poor ventilation. However, in outdoor or well-ventilated environments, it poses no danger, and there is no residue left in the food.

The combustion of methane gas (CH4) yields the highest quantity of carbon dioxide, with additional byproducts including ammonia (NH3) and water vapor (H2O). Among these byproducts, carbon dioxide gas (CO2) holds the most significant proportion. In subsequent processes, there is a conversion of carbon dioxide gas (CO2) into hydrogen energy.

In the process of methane gas combustion, the resulting product is carbon dioxide (CO2), a component initially factored into the design of the original Biogas project.

 

Traditionally, these carbon dioxide (CO2) gases were released into the atmosphere, with plants acting as a natural mechanism for absorbing carbon dioxide (CO2). To address environmental concerns, carbon capture technology (CCUS) has been introduced. This technology aims to capture carbon dioxide (CO2) to prevent its release into the atmosphere. The captured carbon dioxide (CO2) is then utilized as a reactant in the Hybrid Na-CO2 system, ultimately producing hydrogen (H2) and electrical energy cells as the final products.

  But what is the Hybrid Na-CO2 System and how does it work?

The hybrid Na-CO2 cell is essentially a fuel cell that can continuously produce electrical energy and hydrogen through efficient CO2 conversion with stable operation for over 1,000 hr from spontaneous CO2 dissolution in aqueous solution. In addition, this system has the advantage of not regenerating CO2 during charging process, unlike aprotic metal-CO2 cells. This system could serve as a novel CO2 utilization technology and high-value-added electrical energy and hydrogen production device.

The chemical reaction of CO2 dissolution mechanism is as follows:

Equation 1:

CO2(aq) + H2O(l) ⇌ H2CO3(aq), Kh = 1.70 × 10−3

Equation 2:

H2CO3(aq) ⇌ HCO3-(aq) + H+(aq), pKa1 = 6.3

When CO2 is purged into an aqueous solution (e.g., distilled water, seawater, NaOH solution), CO2 dissolution proceeds and carbonic acid (H2CO3(aq)) is formed through the hydration of CO2 (Equation 1). For a standard state condition in pure water, this spontaneous chemical equilibrium of CO2 hydration is determined by the hydration equilibrium constant (Kh = 1.70 × 10-3). Then, the carbonic acid dissociates into HCO3- and H+ determined by the first acid dissociation constant (Ka), shown in Equation 2

Because carbonic acid is a polyprotic acid dissociating multiple steps, an in-depth understanding of CO2 dissolution requires that the second acid dissociation step, i.e., HCO3-(aq) ⇌ CO32-(aq) + H+(aq) (Ka2 = 4.69 × 10-11), be considered. However, the second acid dissociation constant is significantly smaller than the first (Ka1 ≫ Ka2), making it negligible in calculating the proton concentration. 

The electrochemical reactions are composed of anodic reaction of sodium metal oxidation (Equation 3) and cathodic reaction of hydrogen evolution (Equation 4):

Equation 3 (Anodic reaction): 

2Na → 2Na+ + 2e− Eo = −2.71 V

Equation 4 (Cathodic reaction): 

2H+ + 2e− → H2(g) Eo = 0.00 V

Equation 5 (Net equation): 

2Na + 2H+ → 2Na+ + H2(g) Eo = 2.71 V

Then, the electrochemical net equation is simply given as the oxidation of
Na metal and the spontaneous evolution of hydrogen (Equation 5).
Because the potential of cathodic reaction is closely influenced by the pH of aqueous
solution, the dissolution of CO2 renders a favorable electrochemical reaction environment
by acidifying the aqueous solution.



  References:

Food and Agriculture Organization of the United Nations.//(2022).//Livestock and enteric methane.//Retrieved September 29,2023,/from/https://www.fao.org/in-action/enteric-methane/news-and-events/news-detail/cutting-livestock-methane-emissions-for-stronger-climate-action/en

United Nations.//(2023).//Take urgent action to combat climate change and its impacts.//Retrieved September 29,2023,/from/https://sdgs.un.org/goals/goal13


Professor Guntae Kim et al.//(2018).//Scientists Turn Carbon Emissions into Usable Energy.//Retrieved September 29,2023,/from/https://news.unist.ac.kr/scientists-turn-carbon-emissions-into-usable-energy/?fbclid=IwAR1I1kt8oYUGFIr7VbsRIhFjl5FMUHJVb7mmTgpos3kYH6UV-sagOKIYJqs


Tim Searchinger et al.//(2021).//Opportunities to ReduceMethane Emissions fromGlobal Agriculture.//Retrieved September 29,2023,/from/https://searchinger.princeton.edu/sites/g/files/toruqf4701/files/methane_discussion_paper_nov_2021.pdf


S.Suwansri.//(2014)./A biomethane solution for domestic cooking in Thailand.//Retrieved September 29,2023,/from/https://www.sciencedirect.com/science/article/abs/pii/S0973082614000842

IEA.//(2021).//Methane and climate change.//Retrieved September 29,2023,/from/https://www.iea.org/reports/methane-tracker-2021/methane-and-climate-change

Changmin Kim et al.//(2018).//Efficient CO2 Utilization via a Hybrid Na-CO2 System Based on CO2 Dissolution.//Retrieved September 29,2023,/from/https://www.sciencedirect.com/science/article/pii/S258900421830186X

Cristian Arthur Robbins.//(2012).//Food waste diversion for enhanced methane gas production at the drake water reclamation facility.//Retrieved September 29,2023,/from/https://api.mountainscholar.org/server/api/core/bitstreams/e5f38957-64d9-4589-90de-8f7815550aef/content


  Webmaster & Presenters:

This site is brought to you by Pheempapob Chatarupacheewin M.5/1 No.42 from Saint Gabriel's College, Thailand via Adobe Dreamweaver 2021,
presenting Miss Renu Rattanapol

Presenting to Master Kongkiat Nualnuplong with the help of 2 co-presenters, Patdanai Wisittanong No.28 and Peerawich Rthamkun No.31 from M.5/1 of Saint Gabriel's College.