PAES 413

biogas plant

plant used to process animal wastes or manure to produce biogas and sludge consisting of an inlet/mixing tank, digester, gas chamber and outlet/sludge tank

integrated plant

biogas plant where the digester and gas chamber form one unit

split-type plant

biogas plant where the digester and gas chamber form separate units

multi-digester plant

plant with series of digesters

floating type

plant consisting of digester and a moving, floating gasholder that either float directly in the fermenting slurry or in a separate water jacket

fixed type

closed digester with an immovable, rigid gas chamber and a displacement pit

balloon type

plant consisting of a heat-sealed plastic or rubber bag (balloon), combining digester and gasholder

collecting tank

holding tank where manure and water are collected, stored and separated from heavy and non-biodegradable materials before feeding them into the digester

inlet pipe

serves as conveyor of the manure-water mixture or slurry from the mixing tank to the digester

digester

water and air tight container designed for the process of anaerobic microbiological degradation of organic matter into which the slurry is introduced for digestion and methanization

baffle board

division in the digester that prevent the slurry from premature exit into the sludge/outlet tank

stirrer

mechanical device inside the digester used to stir the slurry

gas chamber

space inside or outside the digester for the collection and storage of biogas

gasholder retainer

cantilever beam that holds the gasholder/movable cover in position at the desired biogas pressure

outlet pipe

serves as conveyor where the effluent or the slurry is forced out

backfill

layer of compacted soil and gravel to support the digester wall

loading rate

amount of slurry fed per unit volume of digester capacity per day

substrate

organic material used to produce biogas

seeding

adding or introducing anaerobic bacteria to the digester

slurry

mixture of manure and water

freeboard

difference in height between the digester wall and the filling line

filling line

level of slurry when the digesters is at full load

retention time

average period that a given quantity of slurry is retained in the digester for digestion

toxic materials

materials that inhibit the normal growth of pathogens in the digester such as mineral ions, heavy metals and detergents

methanization

various processes that take place among the methanogens, non-methanogens and substrates fed into the digester as inputs

methanogens

anaerobic bacteria that act upon organic materials and in the process, produce biogas

mesophilic temperature range

temperature range of 20 oC - 40 oC where mesophilic bacteria operates

gas production rate

amount of biogas produced per day per cubic meter of slurry

biogas

mixture of gas (composed of 50 to 70 percent methane and 30 to 40 percent carbon dioxide) produced by methanogenic bacteria

scum

layer of floating material (mainly fibrous) on the slurry

sludge

settled portion or precipitate of the slurry; a mud-like, semi-solid mass

effluent

residue that comes out at the outlet after the substrate is digested/processed inside the digester

Continuous-fed biogas plant

System where tank size should not exceed total slurry volume for 10 days

Slurry volume

Volume of manure and water at a 1:1 ratio

Batch-fed

Slurry input rate multiplied by slurry charging interval

Optimum dimension calculation

Follows the procedure used for digester tank

Inlet pipe diameter

Minimum diameter required is 0.2 m

Digester tank capacity

Calculated from daily slurry volume multiplied by retention time

Retention time

Time range for different animal manure types in the digester

Optimum cross-section of digester plant

Includes ratios for different cross-section types

Floating type digester

Includes recommended ratios for different cross-sections

Baffle board

Located midway between inlet and outlet pipes in the digester

Fixed type digester

Integrated digester and gas chamber with specific volume requirements

Balloon type digester

Volume occupied by slurry in the digester

Gas chamber volume calculation

Based on manure amount multiplied by gas production rate

Gas production potential

Calculated by multiplying manure amount by gas production rate

Gas chamber volume for floating type

Depends on gas production and consumption

Effective gas volume calculation

Daily biogas production minus consumption for cost minimization

Outlet pipe diameter

Minimum diameter required is 0.2 m

Outlet tank volume for floating and balloon type

Minimum volume equal to daily slurry input of the digester

Outlet tank volume for fixed type

Volume should be 1/3 of digester volume occupied by slurry

Functional requirement for collecting tank

Includes concrete channels, slope, and sluice gate specifications

Functional requirement for inlet pipe

Includes material, inclination, and positioning specifics

Functional requirement for digester construction

Details on materials, reinforcement, plastering, and access specifications

Balloon type

A type of biogas digester made of red mud plastic, natural polyethylene plastic tube, heat-sealed plastic, or rubber balloon with the upper portion serving as gas storage.

Agitator/Stirrer

Device used to mix the substrate in a biogas plant to improve bacteria activity, release biogas, provide fresh nutrients, and ensure uniform temperature distribution.

Gas chamber

Part of a biogas plant where gas is stored, with specific requirements for different plant types like floating-drum and fixed dome.

Gas Outlet pipe

Pipe connected to the biogas plant's outgoing valve, with specific requirements for material, installation, and testing for gas-tightness.

Piping system

System connecting the biogas plant to gas appliances or reservoir, with guidelines on materials, installation depth, and protection against UV radiation.

Flame arrester

Safety device made of fine copper wire mesh inserted in the gas line to prevent the risk of flames traveling back into the biogas plant.

Outlet pipe

Pipe used to draw slurry from the biogas plant, with specific requirements for different plant types like concrete, fixed type, balloon type, and floating type.

Chamber material

Concrete with smooth finish, may have steel reinforcement.

Chamber cover

Made of ordinary or corrugated GI sheets.

Overflow height

At least 100 mm lower than gas chamber's lower surface.

Chamber floor height

At least equal to operating pressure or 0.2 m from filling line + 15% freeboard.

Blind drain

Constructed for water seepage from pit bottom, filled with gravels or chips.

Circular drain

Built for water seepage from excavated earth bank walls.

Deep wells

Constructed 2 m away from pit for excessive groundwater.

Sunken barrel

Used for managing excess water and shifting sand.

Heating systems

Recommended for maintaining proper substrate temperature.

Pumps

Used for fast substrate movement or when gravity is impractical.

Pump delivery lines

Made of steel, PVC, PE, or reinforced plastic/rubber tubing.

Visual check

Inspect digester inner wall for cracks, gaps, and tightness.

Water-holding mark

Fill digester with water to check for leaks or cracks.

Air tight method

Test gas tightness by pressurizing digester with water or air.

Sludge management

Involves spreading digested slurry on fields or further conditioning.

Hydrolysis

First stage of digestion process, breaking down waste into simpler compounds.

Acidification

Second stage where monomers are fermented into various acids.

Methanization

Final stage where acids are converted by bacteria into methane.

Mesophilic temperature

Optimal range for anaerobic fermentation: 20°C - 40°C.

pH value

Should be maintained between 7 - 8.5 for optimal digestion.

Available Nutrient

Substrates need carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorous, etc.

Inhibitory factors

Mineral ions can stimulate or inhibit bacterial growth.

Nitrogen content

Important for maintaining proper C/N ratio in organic materials.

Gas Production Potential

Amount of gas produced per kg of manure

Retention Period

Duration manure is retained for gas production

Excavation Procedure

Process for digging underground digester

Maximum Excavation Slope

Ratio of height to width based on soil type

Foundation of Digester

Base material for the digester construction

Backfilling

Process of refilling the digester with soil mixture

Parts of Floating Type Plant

Components of a biogas plant with external guide frame

Parts of Fixed Type Plant

Components of a stationary biogas plant

Parts of Balloon Type Plant

Components of a biogas plant with a balloon structure

Digester Height Formula

Calculation for determining digester height based on volume and ratio

Gas Chamber Dimensions

Specifications for gas chamber size in biogas plant

Water-Sealed Gas Chamber

Upper part of digester with double-walled water seal

Distance of Retainer

Vertical distance of gas retainer below top of digester wall

Mixing Chamber Volume

Calculation for determining the volume of the mixing tank

Dimension of Digester Tank

Size calculation for the digestion tank

Gasholder Dimension

Specifications for the size of the gasholder in a biogas plant