BIOGAS
It is also called "swamp gas". The spontaneous ignition of the fermented gas is the cause of little flames (Wisps), on some water bodies.This gas is produced by anaerobic digestion. It consists primarily of methane (50 to 70%), from which it derives its energetic virtues, and carbon dioxide (CH4 and CO2). The exact composition varies according to its production process.
In what is it different from biomethane?
Also called 'green gas', the biomethane is almost pure methane, obtained from either purified biogas or from syngas produced from wood, through a process called methanation.
This gas, 100% renewable, has the same properties as natural gas. It can be used as fuel (in a motor) or as a combustible (heating).
Also called 'green gas', the biomethane is almost pure methane, obtained from either purified biogas or from syngas produced from wood, through a process called methanation.
This gas, 100% renewable, has the same properties as natural gas. It can be used as fuel (in a motor) or as a combustible (heating).
The biogas production:
On an industrial scale, the biogas can be produced in a methanisation plant, but also spontaneously in landfills for non-hazardous waste, where it is the result of the anaerobic degradation of the biodegradable elements of household waste and similar buried.
Notes: The storage of waste produces biogas named "fatal" because its production is inevitable. The recovering of biogas in landfills allows capturing methane coming from biomass.
The methane, if released into the atmosphere, is a greenhouse gas 21 times stronger than CO2.
If this biogas is not used, it must be burned in torchiere and transformed into CO2
On an industrial scale, the biogas can be produced in a methanisation plant, but also spontaneously in landfills for non-hazardous waste, where it is the result of the anaerobic degradation of the biodegradable elements of household waste and similar buried.
Notes: The storage of waste produces biogas named "fatal" because its production is inevitable. The recovering of biogas in landfills allows capturing methane coming from biomass.
The methane, if released into the atmosphere, is a greenhouse gas 21 times stronger than CO2.
If this biogas is not used, it must be burned in torchiere and transformed into CO2
The use of Biogas:
There are four main uses of biogas:
•Transformation into natural gas for vehicle (NGV).
•Production of heat that is consumed near the production site,
•Injection of biogas, which becomes, after treatment, biomethane into natural gas networks,
•Combined production of electricity and heat in a co-generation power plant.
CROPS DEDICATED TO “METHANATION”:
The production of crops dedicated methane-producers is an alternative way of developing biogas, provided that they do not compete with other sectors, food or otherwise.
Anaerobic digestion of energy crops dedicated «Whole Plant» provides 3 to 5 toe/ha (tonne of oil equivalent per hectare), against only 1.4 toe/ha for rapeseed biodiesel and 1.8 toe/ha for grain-based ethanol. The methanisation is mainly carried out from maize (corn) but its development requires a lot of water and inflates food prices.
Other plants such as alfalfa and sorghum seem more suited to this type of dedicated crop.
Despite some advantages, these first-generation biofuels, derived from food crops are accused of threatening the food security and promoting deforestation. In contrast, second-generation biofuels, from lingo-cellulosic biomass (wood, straw, etc....) are not in competition with food, which is why research is now focused on this type of biomass.
PRESENTATION OF A METHANISATION PLANT:
The process of anaerobic digestion or methanisation consists in sorting waste to remove unwanted compounds from organic matter and then putting it in a digester maintained between 35°C and 50-55°C for about twenty days.
Besides biogas, anaerobic digestion also produces a digestate, which becomes, after treatment and composting, a recoverable organic product for agriculture. ( click on image to enlarge )
DIGESTATE:
In methanisation, most of the nitrogen and nutrients are concentrated in the digestate. It is an organic by-product usable by farm owners, as a substitute for chemical fertilizers.
As a waste product, the digestate is subject to the rules of the landfarming and cannot get out the farming operation.
METHANISATION OF AGRICULTURAL WASTES:
Agriculture is the sector where the impact in terms of greenhouse gas
emissions is the most significant. Indeed, the methane released into
the atmosphere is much more emissive than the burned biogas. In addition, methanisation provides answers to farmers for storage and treatment of waste. It also solves the environmental problem concerning bad smells. Finally and most importantly, it is an additional income for farmers, thanks to great rates for the resale of energy.
METHANISATION OF HOUSEHOLD WASTE:
The methanisation of garbage generally includes the following steps:
•Sorting of wastes upon entry, which must be done very carefully;
•Methanisation of fermentable portion;
•Composting of fermentation residue:
•Incinerating wastes not accepted for methanisation and landfill of the non-combustible wastes and incineration residues.
How to accelerate the waste methanisation?
Organic waste, e.g. from supermarkets or restaurants, are mixed with vegetal waste, regularly watered and stored for a duration of one month in sealed enclosures (digesters) which are heated to a temperature of 38°C to speed up fermentation.
Incineration versus methanisation:
The methanisation of waste has several advantages compared to incineration.
In addition to its balance sheet in terms of greenhouse gas emissions, it does not emit toxic smoke, does not generate thermochemical transforming of products is free of residue from smoke treatment and of slag and is more economical overall.
METHANISATION OF INDUSTRIAL WASTE:
Industrial methanisation aims to reduce the pollution load of waste-water releases to comply with environmental regulations, to reduce the mass of industrial sewage to be handled and finally, to produce energy.
SEWAGE TREATMENT PLANTS:
Sewage treatment plants treat waste-water, whether from sewer or septic tank. Some also treat industrial sewage.
In general, low load waste-waters and sludges are separated to be treated differently. It is in the sludges treatment that methanisation can act.
There are four main uses of biogas:
•Transformation into natural gas for vehicle (NGV).
•Production of heat that is consumed near the production site,
•Injection of biogas, which becomes, after treatment, biomethane into natural gas networks,
•Combined production of electricity and heat in a co-generation power plant.
CROPS DEDICATED TO “METHANATION”:
The production of crops dedicated methane-producers is an alternative way of developing biogas, provided that they do not compete with other sectors, food or otherwise.
Anaerobic digestion of energy crops dedicated «Whole Plant» provides 3 to 5 toe/ha (tonne of oil equivalent per hectare), against only 1.4 toe/ha for rapeseed biodiesel and 1.8 toe/ha for grain-based ethanol. The methanisation is mainly carried out from maize (corn) but its development requires a lot of water and inflates food prices.
Other plants such as alfalfa and sorghum seem more suited to this type of dedicated crop.
Despite some advantages, these first-generation biofuels, derived from food crops are accused of threatening the food security and promoting deforestation. In contrast, second-generation biofuels, from lingo-cellulosic biomass (wood, straw, etc....) are not in competition with food, which is why research is now focused on this type of biomass.
PRESENTATION OF A METHANISATION PLANT:
The process of anaerobic digestion or methanisation consists in sorting waste to remove unwanted compounds from organic matter and then putting it in a digester maintained between 35°C and 50-55°C for about twenty days.
Besides biogas, anaerobic digestion also produces a digestate, which becomes, after treatment and composting, a recoverable organic product for agriculture. ( click on image to enlarge )
Methanisation plant diagram
 |
| Methanisation digestate |
In methanisation, most of the nitrogen and nutrients are concentrated in the digestate. It is an organic by-product usable by farm owners, as a substitute for chemical fertilizers.
As a waste product, the digestate is subject to the rules of the landfarming and cannot get out the farming operation.
METHANISATION OF AGRICULTURAL WASTES:
 |
| Digesters |
Agricultural biogas diagram
Biogas production according to raw material
METHANISATION OF HOUSEHOLD WASTE:
The methanisation of garbage generally includes the following steps:
•Sorting of wastes upon entry, which must be done very carefully;
•Methanisation of fermentable portion;
•Composting of fermentation residue:
•Incinerating wastes not accepted for methanisation and landfill of the non-combustible wastes and incineration residues.
How to accelerate the waste methanisation?
Organic waste, e.g. from supermarkets or restaurants, are mixed with vegetal waste, regularly watered and stored for a duration of one month in sealed enclosures (digesters) which are heated to a temperature of 38°C to speed up fermentation.
Incineration versus methanisation:
The methanisation of waste has several advantages compared to incineration.
In addition to its balance sheet in terms of greenhouse gas emissions, it does not emit toxic smoke, does not generate thermochemical transforming of products is free of residue from smoke treatment and of slag and is more economical overall.
METHANISATION OF INDUSTRIAL WASTE:
Industrial methanisation aims to reduce the pollution load of waste-water releases to comply with environmental regulations, to reduce the mass of industrial sewage to be handled and finally, to produce energy.
Industrial effluents treatment process
SEWAGE TREATMENT PLANTS:
Sewage treatment plants treat waste-water, whether from sewer or septic tank. Some also treat industrial sewage.
In general, low load waste-waters and sludges are separated to be treated differently. It is in the sludges treatment that methanisation can act.
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