Why producing CBG, LBG, hydrogen, methanol from biogas can be beneficial

Source: The post is based on an article “Why producing CBG, LBG, hydrogen, methanol from biogas can be beneficial” published in DTE on 19^th October 2022.

Syllabus: GS 3 – Environment

Relevance: Biogas and its various applications.

News: With the advancement in research and the tremendous urge to shift to greener fuels, biogas came back into the picture to supplement the rising global energy demand.

What is Biogas?

Biogas is a renewable fuel produced using the anaerobic digestion process from the organic feedstock. It is primarily composed of methane (50-65%), carbon dioxide (30-40%), hydrogen sulfide (1-2.5%) and a very small fraction of moisture.

What are the subsidiary sustainable transportation fuels one can obtain from biogas?

Biogas can be converted to produce numerous sustainable transportation fuels.

Methane

The removal of unwanted components like carbon dioxide, hydrogen sulphide and moisture from raw biogas yields pure methane (over 97% content). Some of the common methods to purify biogas include water scrubbing, membrane separation, pressure swing adsorption and adsorption.

Compressed biogas (CBG)

Upgraded or high-purity biogas compressed at 250 bar pressure results in a fuel called compressed biogas (CBG). This has properties similar to compressed natural gas (CNG) and could be directly used to power CNG engines.

However, CBG is considered more suitable to power small-sized vehicles, though heavy engines have been used for short-distance driving.

Liquefied biogas (LBG)

It is obtained by liquefying the biogas-derived methane by cooling it at -162 degrees Celsius. It has a higher energy density that lowers the storage space requirements of CBG.

At atmospheric pressure, the energy density of liquid methane is roughly 600 times more than that of gaseous methane and 2.5 times greater than that of methane at 250 bar.

Advantages of LBG: a) LBG has become a viable alternative fuel for heavy-duty road transportation since it has a comparatively high energy density (1 litre of LBG against 2.4 litres of CBG), low sulphur content and lower life cycle greenhouse gas emissions than diesel.

Hydrogen

Gasification of biogas is performed by limiting the amount of oxygen and steam present in the reaction and heating the bio-methane to high temperatures (usually over 600°C). As a result of this process, Syngas a mixture of hydrogen and carbon monoxide is created. The hydrogen produced after the removal of carbon monoxide could be used in fuel cells to generate power.

Methanol

Direct methanol production from biogas is done through methanotrophy or partial oxidation. Methanol is an effective fuel with an octane rating of 100. It emits less particulate matter and NOx than gasoline and doesn’t produce SOx because it doesn’t contain sulphur.

Methanol is more affordable than LNG or marine oils with virtually no SOx or NOx emissions.

How India is promoting biogas?

CBG is the only transportation fuel from biogas for which commercialisation efforts have been made. The government has been encouraging private businesses to set up CBG plants and provide CBG to oil marketing companies for sale as automotive and industrial fuels under the Sustainable Alternative Towards Affordable Transportation (SATAT) scheme.

The scheme has set a goal to produce 15 million tonnes of CBG from 5,000 plants by 2023–24.

What are the challenges in promoting biogas in India?

Currently, LBG, hydrogen and methanol are not produced from biogas in India. This is because,

a) CBG exists in the gaseous form. So, it demands bigger volumes for transportation, b) Unavailability of biogas in bulk for such derivatives, c) There is an absence of infrastructure to generate and market these fuels, d) There is a deficiency of modified automobile engines in India, e) There is a lack of effective research and development push to improve process economics.

Overall renewable sources like biogas could be used to produce numerous fuels but their potential still remains untapped.