BIOGAS
1.Biogas:
- Biogas, is a renewable fuel produced using the anaerobic digestion process from organic feedstock.
- It is primarily composed of methane-50-65%, Carbon dioxide-30-40%, Hydrogen sulfide-1-2.5% & small amount of moisture.
- It was thought of as a rural economy product.
- With the advancement in research & the tremendous urge to shift to greener fuels, biogas came back into the picture to supplement the rising global energy demand.
- Biogas contributes to all 17 Sustainable Development Goals.
- Biogas can be converted to produce numerous sustainable transportation fuels.
- The removal of unwanted components like carbon dioxide, hydrogen sulphide & moisture from raw biogas yields pure methane.
| Some of the common methods to purify biogas include water scrubbing, membrane separation, pressure swing adsorption & adsorption. |
2.CBG-LBG:
- The high-purity biogas compressed at 250 bar pressure results in a fuel called compressed biogas(CBG).
- CBG has properties similar to compressed natural gas(CNG) & could be directly used to power CNG engines.
- The drawback of CBG is its existence in the gaseous form, which demands bigger volumes for transportation.
- Hence, it is considered more suitable to power small-sized vehicles, though heavy engines were used for short-distance driving.
- If the biogas-derived methane is liquefied by cooling it at -1620 C, the fuel thus obtained is liquefied biogas(LBG).
- LBG has higher energy density that lowers storage space requirements.
- At atmospheric pressure, the energy density of liquid methane is roughly 600 times more than that of gaseous methane & 2.5 times greater than that of methane at 250 bar.
- LBG has become a viable alternative fuel for heavy-duty road transportation as it has a comparatively high energy density, low sulphur content & lower lifecycle greenhouse gas emissions than diesel.
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Biomethane:
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3.Key Points:
- Gasification is performed by limiting the amount of oxygen & steam present in the reaction & heating the bio-.methane to high temperatures>6000C.
- Syngas, which is a mixture of hydrogen & carbon monoxide, is created as a result of gasification.
- The hydrogen produced after the removal of carbon monoxide could be used in fuel cells to generate power.
- Methanol can also be generated from syngas.
- Methanol is an effective fuel with an octane rating of 100, which emits less particulate matter.
- Methanol, which is affordable than LNG or marine oils with virtually no SOx /NOx emissions, attracted a lot of interest from the maritime community.
4.The context in India:
- CBG is the only transportation fuel from biogas for which commercialisation efforts were made.
- The Indian Government was encouraging private businesses to set up CBG plants & provide CBG to oil marketing companies for sale as automotive & industrial fuels under the Sustainable Alternative Towards Affordable Transportation(SATAT) scheme.
- SATAT has set goal to produce 15 million tonnes of CBG from 5,000 plants by 2023-24.
- Presently, LBG, hydrogen & methanol are not produced from biogas in India.
- The reasons are the unavailability of biogas in bulk for such derivatives, absence of infrastructure to generate & market these fuels, the deficiency of modified automobile engines as well as the lack of effective research & development push to improve process economics.
- The Indian Government & Niti Aayog have outlined roadmaps to hasten the transition towards green fuels & promote LNG, hydrogen & methanol.
- A renewable source like biogas that could be used to produce these fuels, still remains untapped.
Source: Downtoearth
