In the previous blog, I wrote about the pollution caused due to man-made materials, and in this article, I will focus on methane as an environmental pollutant and what can be done to overcome its toxicity.
Methane is the smallest saturated hydrocarbon in nature, and it is generally produced as a by-product of anaerobic digestion. The microorganisms that can utilize the carbon sources as food under limited oxygen are capable of producing methane. These biological reactions occur naturally in marshes and swamps, rice fields, as well as cattle-rearing areas, allowing the methanogenic bacteria to grow and produce methane. Excessive burning of plant and animal-based products also increases methane load.
Several human activities have also led to methane production, and the most common actions include burning coal and petroleum as fuels, wastewater treatment, and expansion of rice fields for agriculture. The methane gas escapes into the atmosphere and causes ecological issues like Global Warming.
Potential issues and problems
Since methane is a naturally produced organic compound, there shouldn’t be any problems with its over-production, right? However, the reality is far from the belief because methane is a highly potent Greenhouse gas, with even higher toxicity than carbon dioxide. So what happens to the methane produced from human activities? After all, it cannot be allowed to escape unchecked. Well, the methane gas produced from the industries is willingly burned for conversion into carbon dioxide before it discharges into the atmosphere.
However, the approach is not Eco-friendly as it leads to over-accumulation of carbon dioxide, which is also a Greenhouse gas and contributes towards Global warming. Did you know, that Global warming also increases methane emissions, thereby forming a vicious cycle. Therefore, the major issue is the lack of appropriate technology that can assist in the entrapment and utilization of excess methane.
A) Methane as a biofuel
Methane is a highly reduced molecule that can release a colossal amount of energy when burnt in the presence of air (the calorific value of methane is 50.5 MJKg-1). The methane produced from the industrial gas exhaust can be compressed and concentrated to remove other components (such as moisture, carbon dioxide, hydrogen sulfide, etc.). The concentrated methane gas can be used for cooking, electricity generation, and even as a biofuel.
B) Methane transformation to produce Value-added products
As previously specified, methane is a highly reduced compound (CH4); therefore, its conversion can make a variety of ‘commercial commodities’ such as methanol, formaldehyde, formic acid, and so on. These commodities can be produced chemically (reacting methane with air or oxygen) or biologically (using methane-utilizing organisms).
Methane utilizing organisms! Sure, that sounds fascinating, and believe me, it is. Methane-utilizing organisms are called methanotrophs, and they can produce all the above-mentioned commercial commodities. Not just that, they can also accumulate biopolymers (PHAs) for the replacement of non-biodegradable plastic. If Methanotrophs are cultivated, we can make ‘Bioplastic’ out of methane! Does that mean we can actually address two environmental issues together? Well, yeah, that’s exactly what I’m talking about!
As I hinted in my previous blog, we need to address the ever-increasing accumulation of xenobiotics and ‘remedy’ their consequences. Studies have suggested that the Methanotrophs have special enzymes (MMOs – methane mono-oxygenase), which can degrade these toxic compounds and transform them into non-toxic alternatives.
Technical aspects and Future perspectives
Methane can be a highly valuable commodity if proper strategies can be developed for its applications. Future systems need to be developed with a special focus on the following:
Methane is colorless, odorless, and light gas, so it can escape into the air without detection. Therefore, several methane sources have not yet been identified but contribute to Global warming. Detection and constant monitoring of methane levels would help in preventing its emissions.
Proper entrapment strategies
Since methane is a gas, it mixes (diffuses) with air and becomes diluted; therefore, it is difficult to use the mixed gas commercially. Entrapping the gas can increase the methane concentration and improve its applications for commercial purposes.
Methane transformation using chemical and biotech technologies
Methane transformation into value-added compounds like methanol can prevent relentless burning and production of carbon dioxide. This will reduce the Greenhouse effect and eventually global warming.
Coupling of methane generation and transformation
Since methane can be produced by specific microorganisms and consumed by another group of microorganisms, the applications of both processes can be coupled together. Supposedly, wastewater treatment results in excess methane production, which can be harnessed to produce commercial commodities like methanol, formaldehyde, PHAs, etc. This can prevent unnecessary methane emissions into the air and reduce the transportation costs for methane supply.
Methane is cheap, renewable and a readily available resource. Even though it is challenging to utilize methane for bio-fuel production and synthesize commercially important value-added products, it has significant advantages. The development of suitable biotech strategies will help in unleashing its potential and shift society towards sustainable development.