Laboratory Scale Bio Gas Plant

STARTING UP A BIO GAS PLANT

POST NUMBER :08   Date : 02/05/2004
BIO GAS PLANT PROCESS DESCRIPTION:

FLOW CHART: CRUSHER(less than 7mm particle size)----thermophilic Aerobic digester(Temp 55 degree C)---Mesophilic Anaerobic Digester(37 Degree C and pH at 7.5)---Manure Pit

Biotechnology process

stage one : hydrolysis by hydrolytic bactaria, conversion of extracellular molecules

stage two : thermophilic fermentation based on carbohydrates

stage three : synthesis of volatile fatty acids by acetogenic bacteria

stage four : synthesis of methane by methanogenic organisms

STARTING UP A BIO GAS PLANT:

OPERATION OF BIO GAS PLANT

FLOW CHART: CRUSHER(less than 7mm particle size)----thermophilic Aerobic digester(Temp 55 degree C  pH  5.5)---Mesophilic Anaerobic Digester(37 Degree C and pH at 7.5)---Manure Pit

Aspect	Bottlenecks	Remarks
CONTROLS	Check for Gas leaks	Check hood , pipe etc. Monthly checking of leakage by pressure system and or with soap water
	Cow dung slurry	Make slurry of cow dung and fresh water in the ratio 2kg dung 15 liter water (thumb rule 10% dung of water volume). Fill up the bio digester with the slurry.
	Slurry fermentation	Wait for slurry to form gas. It normally takes 3 to ten days.Gas formation can be seen by rising of floating dome or pressure gauge in fixed dome.
	Start of Feeding	Start fresh feeding after formation of gas. Start with small quantity of feed material in 1:1 ratio. After 15 days, start feeding full capacity.
	Complete Release of first gas produced	Gases should be released to the atmosphere at least three  times at a gap of three days each. It may be needed to be released more till methane percentage of 60% reached .Do a sample bio gas test to know exact position of gas produced.
Technical	Improper preparation of influent solids leading to blockage and scum formation	Proper milling and other treatment measures (pre- soaking, adjustment of C/N ratio); removal of inert particles: sand and stone.
	Temperature fluctuations	Careful regulation of temperature through use of incorporation of auxiliary solar heating system.
	Maintenance of pH for optimal growth of Methanogenic bacteria C/N ratio	Appropriate choice of raw material, regulation of C/N ratio and dilution rate. Appropriate mixing of N-rich and N-poor substrates with cellulosic substrates.
	Dilution ratio of influent solids content	Appropriate treatment of raw materials to avoid stratification and scum formation.
	Retention time of slurry	Dependent upon dilution ratio, loading rate, digestion temperature.
	Loading rate	Dependent upon digester size, dilution ratio, digestion temperature.
	Seeding of an appropriate bacterial Population for biogas generation	Development of specific and potent cultures.
	Corrosion of gas holder	Construction from cheap materials (glass fibre, clay, jute-fibre reinforced plastic) and/or regular cleaning and layering with protective materials (e.g., lubricating oil).
	Pin-hole leakages (digester tank, holder, inlet, outlet)	Establishment of "no leak" conditions, use of external protective coating materials (PVC, creosotes
	Occurrence of CO2 reducing calorific value of biogas	Reduction in CO2 content through passage in lime-water
	Occurrence of water condensate in gas supply system (blockage, rusting)	Appropriate drainage system using condensate traps
	Occurrence of H2S leading to corrosion	On a village scale, H2S removed by passing over ferric oxide or iron filings
	Improper combustion	Proper air gas  mixing appliances necessary
	Maintenance of gas supply at constant pressure	Regulation of uniform distribution and use of gas; removal of water condensate from piping systems; appropriate choice of gas holder in terms of weight and capacity
Residue utilization	Risks to health and plant crops resulting from residual accumulation of toxic materials and encysted pathogens	Avoid use of chemical industry effluents; more research on type, nature, and die-off rates of persisting organisms; minimize long transportation period of un-dried effluent
Health	Hazards to human health in transporting night soil and other wastes (gray-water)	Linkage of latrine run-offs into biogas reactors promotes non-manual operations and general aesthetics
Safety	Improper handling and storage of methane	Appropriate measures necessary for plant operation, handling, and storage of biogas through provision of extension and servicing facilities

DO NOT USE eggshells, Onion peels or left-over bones in this system as they will affect the efficient functioning of the system

Hazards: Methane in a concentration of 6 to 15 percent with air is an explosive mixture. Since it is lighter than air, it will collect in rooftops and other enclosed areas. It is relatively odorless and detection may be difficult. Extreme caution and special safety features are necessary in the digester design and storage tank

POSTED BY SALEEM ASRAF SYED IMDAADULLAH AT 5/02/2004 11:13:00 PM