PNS/BAFS 364:2023 Flashcards
PNS/BAFS 364:2023
Biogas System — Specifications — Wet Anaerobic
Digestion Process
biological conversion of biodegradable materials by microorganisms in the
absence of oxygen creating two main products: biogas and digestate (ISO,
2018)
anaerobic digestion process
amount of organic matters in a substrate that can be degraded by anaerobic
microorganisms. It also indicates the biogas output per unit quantity of
substrate (Deng et al., 2020)
biochemical methane potential (BMP)
gas produced by anaerobic digestion of organic matter (ISO, 2018). It consists
typically of 40-75 % methane, 14-45 % carbon dioxide, along with small
amounts of water vapor and other gases (ISO, 2020)
biogas
system used to process agricultural, fishery, and agro-industrial waste to
produce biogas and sludge consisting of, but not limited to, a mixing tank/inlet,
digester, gas chamber and outlet/sludge tank/hydraulic pressure tank
(AMTEC-UPLB, 2001, modified)
biogas system
biomass
non-fossilized, biodegradable organic materials originating from naturally
occurring or cultured plants, animals and microorganisms, including
agricultural products, by-products and residues that can be used in
bioconversion process and other processes, as well as gases and liquids
recovered from the decomposition and/or extraction of non-fossilized and
biodegradable organic materials (Renewable Energy Act of 2008, 2008,
modified).
biomass resources
biomass resources includes:
agricultural and fishery wastes
agro-industrial wastes
consist of solid and liquid waste, slurry including by-products and
residues resulting from the production and processing of crops, livestock,
poultry, and fishery (AMTEC-UPLB, 2002a;2002b, modified)
agricultural and fishery wastes
consist of solid and liquid waste generated from local activity or series of
activities to maintain or raise the quality or change the form or
characteristics of agricultural, fisheries and forestry products
(Agricultural and Fisheries Mechanization [AFMech] Law, 2013,
modified)
agro-industrial wastes
ratio of carbon and nitrogen content in substrate (Deng et al., 2020)
carbon nitrogen ratio (C/N)
amount of oxygen consumed by oxidizing substrate under heating condition
with chemical oxidants, usually expressed in terms of oxygen consumption in
mg/L or g/L (Deng et al., 2020)
chemical oxygen demand (COD)
anaerobic digestion installation including reactors, tanks and related
equipment (ISO, 2018); also known as biodigester or bioreactor
digester
residue that comes out at the outlet after the substrate is digested/processed
inside the digester (AMTEC-UPLB, 2001)
effluent
safety component meant to combust biogas during exceptional situations
when the biogas is not utilized (ISO, 2018)
flare
distance as measured from the slurry filling line to the inside top of the inlet
tank (Code on sanitation of the Philippines, 1975, modified)
freeboard
space inside or outside the digester for the collection and storage of biogas
(AMTEC-UPLB, 2001); also known as gasholder or biogas storage
gas chamber
average period that a given quantity of slurry is retained in the digester
expressed either in hours or days (AMTEC-UPLB, 2001)
hydraulic retention time
retention time
serves as passage or duct of the slurry from the inlet tank to the digester
(AMTEC-UPLB, 2001, modified)
inlet pipe
chamber where substrate and water are collected, stored and separated from
heavy and non-biodegradable materials before feeding them into the digester
(AMTEC-UPLB, 2001, modified); also known as mixing tank or equalization
tank
inlet tank
temperature range of 20 to 40 oC where mesophilic microorganisms operate
(AMTEC-UPLB, 2001)
mesophilic temperature
serves as passage or duct where the effluent or the slurry is forced out
(AMTEC-UPLB, 2001)
outlet pipe
amount of volatile organic dry matter entering the digester over time,
measured in kilogram per cubic meter digester volume per day (ISO, 2018)
organic loading rate
chamber where digestate is stored (AMTEC-UPLB, 2001, modified)
outlet tank
layer of floating material that may accumulate on the surface of the digester
tank (AMTEC-UPLB, 2001)
scum
adding or introducing anaerobic microorganism to the digester to enhance bio-
digestion (AMTEC-UPLB, 2001)
seeding
settled portion or precipitate of the slurry; a mud-like, semi-solid mass
(AMTEC-UPLB, 2001)
sludge
mixture of substrate and water (AMTEC-UPLB, 2001, modified)
slurry
average period time the slurry is in the inlet tank prior to digestion, expressed
in days (ISO, 2018, modified)
storage period
part of the biomass which is biodegradable and converted by anaerobic
microorganisms and/or enzymes as catalyst into biogas (ISO, 2018)
substrate
feedstock
amount of residues remaining after evaporation and dehydration of substrate
at a certain temperature, expressed in percent (%); It is also referred to as dry
matter, expressed in g/L (Deng et al., 2020)
total solid (TS)
the difference of the total solids and ash content (remaining solid after burning
total solids for one hour at 550 ± 50 °C), expressed in percent (%); It is also
referred to as organic dry matter, expressed in g/L (Deng et al., 2020)
volatile solid (VS)
anaerobic digestion which uses organic material with consistency of 10-20%
dry matter or less (Angelonidi & Smith, 2015, modified)
wet anaerobic digestion
Classifications
A. According to capacity
1. Household biogas system
2. Non-household biogas system
- According to utilization
* Farm-scale biogas system
* Commercial-scale biogas system
- According to energy content
* Small
* Medium
* Large
B. According to the number of digesters
1. Single-digester biogas system
2. Multi-digester biogas system
C. According to feeding method
1. Continuous-fed
2. Batch-fed (mixed or unmixed)
This type of biogas system uses biomass resources from one household for
its own use and consists of a digester and an application for cooking, heating
or lighting only (ISO, 2021).
Household biogas system
This type of biogas system uses agricultural fishery and agro-industrial
wastes from a farm for its own use and an application for heating, lighting
or electrical power production only (ISO, 2021, modified).
Farm-scale biogas system
This type of biogas system uses agricultural fishery and agro-industrial
wastes to produce biogas available for sale (ISO, 2018, modified).
Commercial-scale biogas system
Biogas system with a production capacity of biogas having an energy
content of 0.1 GWh to 5 GWh per year, as specified in Table 1.
Small
Biogas system with a production capacity of biogas having an energy
content of 5 GWh to 100 GWh per year, as specified in Table 1.
Medium
Biogas system with a production capacity of biogas having an energy
content of more than 100 GWh per year, as specified in Table 1.
Large
Biogas system composed of only one digester (AMTEC-UPLB, 2001,
modified).
Single-digester biogas system
Biogas system composed of two or more digesters arranged in either series
or parallel, or a combination of both (AMTEC-UPLB, 2001, modified). This can
also be a multi-stage digester biogas system.
Multi-digester biogas system
Biogas system that is fed with substrate continuously to produce biogas. This
type of biogas system needs a continual supply of substrate.
Continuous-fed
Biogas system that are filled and discharged completely after a fixed retention
time.
Batch-fed (mixed or unmixed)
The non-household biogas system should require a ??? (Code on sanitation
of the Philippines, 1975, modified) distance from vulnerable areas and water
sources in compliance with local and national ordinances, other laws, and
rules and regulations which may be later created or otherwise identified
relevant to biogas systems regarding environmental concerns (ISO, 2021, modified).
25-m
There shall be a vicinity map duly signed by an applicable licensed engineer(s) included in the engineering plans for the biogas system with geographical coordinates using ??? as reference. The vicinity map shall comply with the requirements of the ??? (Omnibus guidelines governing the award and administration of renewable energy contracts and the registration of renewable energy developers).
- Philippine Reference System (PRS) 92
- Department of Energy (DOE) Department Circular (DC) No. DC2019-10-0013
The size of the inlet tank should hold the equivalent slurry volume for a
minimum of ??? and maximum of ??? (AMTEC-UPLB, 2001, modified),
unless appropriately justified by a designed calculation.
- 1 day
- 10 days
The biogas system shall have an ??? to allow the slurry to enter the
digester where it will be broken down by microorganisms to produce biogas.
inlet pipe
Inlet and outlet pipes shall be made of ???.
non-corrosive materials
The biogas system shall have a ???, where the breakdown of organic
matter through the process of anaerobic digestion, shall take place to
produce biogas and other gases.
digester
??? represents the quantity of organic matter that the biogas system can effectively process within a given time frame. Typically, Low organic loading rates for biogas systems ranges at ???, whereas high organic loading rates fall within the range of ???.
- Organic loading rate
- 0.15 to 1 kgCOD/m³-d
- 1 to 10 kgCOD/m³-d
Generally, a manhole with diameter of at least ??? should be constructed in place for maintenance. For stainless steel digester, the manhole should be made of stainless steel as well, with a diameter of at least ???.
- 600 mm
- 500 mm
Structural design of the digester should comply with the ???
National Structural
Code of the Philippines (NSCP)
Classification of biogas digester
A. According to gas chamber design
1. Floating type
2. Fixed type
B. According to position
1. Ground digester
2. Underground digester
Composed of a moving gas chamber that either floats directly in the
fermenting slurry or in a separate water jacket.
Floating type
Composed of a gas chamber fixed to the digester
Fixed type
Digester placed above ground level.
Ground digester
Digester placed below ground level to avoid disruption.
Underground digester
The biogas system shall have a ??? to provide storage and
management for the valuable biogas produced by the digester.
biogas chamber
For floating type, the biogas chamber shall be equipped with an appropriately
designed ??? for safety purposes.
stopper
A ??? (e.g., pressure valves/gas meter, open
manometer, etc.) shall be installed in the biogas chamber.
flare or other regulating devices
The biogas system shall have an ??? to facilitate the removal of
digested material or digestate from the digester.
outlet pipe
The biogas system shall have an ??? to receive and temporarily store
the effluent coming out from the digester.
outlet tank
For floating, the minimum volume of the outlet tank shall be equal to the ??? of the digester
daily slurry input
For fixed type, the volume of the outlet tank shall be ???
1/3 of the digester volume occupied by the slurry
For batch-feed type, the outlet tank shall function as a storage tank with a
minimum volume ???
equal to the digester before disposal
The biogas system shall have an ??? to collect, store
and treat the effluent coming from the outlet tank.
effluent management unit
The biogas system shall have a ??? to process and
manage the residual sludge generated during the anaerobic digestion
process, in a way that minimizes environmental impacts and maximizes the potential for beneficial reuse.
sludge management unit
A ???, if provided, shall act as a pressure regulator and
outlet of the biogas digester.
hydraulic pressure tank
Materials requirements for biogas system
Parameter / Minimum requirements
- Tensile strength / 12 MPa (12 N/mm2)
- Gas permeability / <350 cc/m2/d/bar of methane
- Safety considerations / Shall be in conformance with Occupational
Safety and Health (OSH) Standards
A biogas system should have a facility layout prepared, which is composed of,
but not limited to:
a) Complete list of facility components with dimensions/footprints
b) Distance of components
c) Access roads.
Masonry
Concrete masonry should conform to the ??? (Standard specification for loadbearing concrete
masonry units) and ??? (Standard specification for non-loadbearing concrete masonry units) (BAFS-DA, 2021).
- American Society for Testing and
Materials (ASTM) C90 - ASTM C129
Steel/metal
Structural steel should conform to ??? (Standard specification for
carbon structural steel) and ??? (Standard specification for pipe, steel,
black and hot-dipped, zinc-coated, welded and seamless).
Welded connections should conform to criteria specified in Table 8.1 or Table
10.15 of American Welding Society (AWS) D1.1 (Structural welding — Steel).
Bolted connections should conform to ??? (Standard specification for high strength structural bolts, steel and alloy steel, heat treated, ??? minimum tensile strength, inch and metric dimensions).
Steel sheets should conform to ??? (Standard specification for steel sheet, zinc-coated (galvanized) or zinc-iron alloy-coated (galvannealed) by the hot-dip process).
- ASTM A36
- ASTM A53
- ASTM F3125
- 120 ksi (830 MPa) and 150 ksi (1040 MPa)
- ASTM A653
Rubber and plastic
??? type of plastic should be recommended for gas holder/gas storage lining in conformance with ??? (Standard specification for polyethylene plastics pipe and fittings materials).
??? should be in conformance with ??? (Standard specification for Poly [Vinyl Chloride] [PVC] plastic pipe, schedules 40, 80, and 120). The PVC materials should not be used if the location is ??? (ISO, 2021).
- High Density Polyethylene (HDPE)
- ASTM 3350
- Polyvinyl Chloride (PVC)
- ASTM D1785-21a
- exposed to heat or sunlight
Composite materials
Reinforcing steel bars should conform to ??? (Standard specification
for deformed and plain carbon-steel bars for concrete reinforcement). (BAFS-DA, 2021)
ASTM A615
Wood/timber
Wood or timber to be used should conform to ??? (Standard practice for establishing structural grades and related allowable properties for visually graded lumber). (BAFS-DA, 2021)
- ASTM D245
Biogas system structures are categorized as ??? of Presidential Decree (PD) 1096, series of 1977 (Adopting a National Building Code of the Philippines [NBCP] thereby
revising Republic Act numbered sixty-five hundred forty-one [R.A. NO. 6541]), and shall comply with the requirements indicated along with the existing Implementing Rules and Regulations (IRR) of the NBCP (PD 1096).
Industrial or Storage and Hazardous under Group F or G
Construction works shall comply with ???, series of 1977 (Adopting a NBCP thereby revising RA 6541) along with the corresponding IRR.
Chapters 11 and 12 of the PD 1096
The geotechnical investigation shall include:
a) Location of water table;
b) Soil bearing capacity; and
c) Other relevant information that would like to be considered.
Geotechnical investigation for household biogas system shall include:
a) Ocular inspection; and
b) Manual digging of about 1.5 m to check the level of the water table.
Excavation for the digester should be ??? as possible. A ??? minimum
gap on both sides shall be allowed for backfill. ??? of the earth bank (ratio
of excavated height to width) should be considered in order to avoid the
collapse of earth
- vertical
- 0.15 m
- Slope
ratio of excavated height to width
Slope
Maximum excavation slope on various grounds
Kind of soil - Ratio of height to width
- Sandy soil - 1:1
- Clayey sandy soil - 1:0.67
- Clayey soil - 1:0.50
- Clay - 1:0.33
- Soil with gravel - 1:0.67
- Dry loess - 1:0.25
Foundation of the digester should be made of ???, and tamped before pouring of concrete.
cobbles or crushed stones
For loose soil, the mixture of the backfill should be ???. Water content in the backfilled soil should be about ???
30% gravel or broken stones and 70 % soil
20 % – 25 %
Each layer of backfill outside the wall should be ???.
compacted
The backfill area should be ??? to allow easy drainage of surface
water. ???, should be grown in the backfilled
area.
- well-sloped
- Grass and plants but not trees
All plumbing works shall comply with the ???
Revised National Plumbing Code of
the Philippines
Any electrical installations shall comply with the ???
National Electrical Code
(NEC)
All mechanical installations shall comply with the ???
Philippine Mechanical
Engineering Code (PMEC)
Biogas systems shall comply with applicable safety provisions indicated in ??? (Biomass and Biofuels Safety, Health and Environment
Code of Practice).
Sections V (Biomass facilities) and VI (Biofuel facilities) of the DOE DC No.
DC2021-06-0020
Biogas systems shall conform to safety provisions indicated in ??? (Technical means for ensuring safety — Guidelines).
PNS/BAFS 330:2022
For the design of any pressurized component of the biogas system, a
minimum factor of safety of ??? shall be used.
2.0
Materials shall comply with the ??? as
specified in the DENR Department Administrative Order (DAO) 2015-09
(Rules and procedures for the implementation of the GHS of classifications and labeling of chemicals in preparations of Safety Data Sheets (SDS) and labeling requirements of toxic chemical substances).
Globally Harmonized System (GHS)
Biogas flare presence requirement
Capacity production or processing raw
biogas, Nm3/h — Biogas flare required — Biogas buffer
- 0-10 — Flare within 24 h call-off
basis
— 2 h; no buffer if flare is
available - 10-20 — Flare within 12 h call-off
basis
— 2 h; if no buffer, flare readily
available - > 20 — Permanent Flare
— 0.5 h; immediately to permanent flare, as far as no buffer is available or buffer is exceeded
Nm3
/h = ???
Normal cubic meter per hour
In case of methane release in the facility, it shall be combusted by an
???
emergency flare
Flare shall comply with the ??? (Fire Code of the Philippines).
IRR of RA 9514
Venting and discharge of hazardous gases
Discharge of vent pipes shall not be located near ignition sources or ventilation openings, altitudes where the risk of inhalation is possible. A minimum required safety distance of ??? shall be applied. A manual describing the explosion safety zones and their location, along with where the vents are discharged, shall be provided. (ISO, 2021, modified)
Safety measures shall be taken to ensure that the effluent is sufficiently stable
so that the release of hazardous gases that are dangerous to humans, animals and the environment is minimized. Required permit or any equivalent
document shall be secured before releasing hazardous gases in compliance with ???.
- 5 m
- Section 16 of the Philippine Clean Air Act of 1999
Fire control and mitigation
The biogas plant shall comply with the fire control and mitigation requirements
indicated in ??? (Fire hazards, protection and control) of the ??? (Biomass and biofuels safety, health and
environment code of practice), ???
(Renewable energy safety, health and environment rules and regulations), and the ???
- Item V of
- Section III of
DOE DC No. DC2021-06-0020 - Section 26 of DOE DC No. DC2012-11-0009
- IRR of RA 9514 (Fire Code of the Philippines).
The biogas plant shall be provided with the following, as applicable:
a) Fire suppression devices, equipment or systems (e.g., flame arrester, biogas control valve, or fire extinguisher);
b) Fire safety structures (e.g., fire exits, fire break); and
c) Fire protection and warning systems (e.g., fire alarm, smoke detectors).
Operation and Maintenance
The operation and maintenance provision shall be in conformance with the provisions from ??? (Biogas Plant – Specifications)
PAES 413:2001
Starter/Seeding
The initial raw materials should contain slurry with a high bacteria population.
About ??? of the total slurry volume should be added when the digester is
about ??? full.
- 5-10%
- 25%
Filling the digester
Before putting any slurry into the digester, all valves should be ???. Mix the biomass resource and water thoroughly and fill the digester up to the ???
- open
- ring level or top beam
Mixing slurry for loading
Mixing slurry for loading should be based on the designed ??? as specified in the design or by the manufacturer.
organic loading rate
Masonry
If the digester is damaged in the form of cracks or leaks, the damaged area
should be repaired. The edges of the damaged area should be cleaned and
roughened. ??? should be attached to the walls with nails at least ??? from either side of the crack. The plastering ??? mortar should be at least ??? thick. The finish should be
roughened and should be allowed to dry for at least ???. Wax/paraffin seal shall be applied. Testing shall be performed afterward for verification
(AMTEC-UPLB, 2001).
- Two to three layers of chicken wire
- 30 cm
- cement-sand (1:3)
- 13 mm
- two weeks
