GHG Emissions Reduction

Methodology of GHG Emissions Reduction

Biogas as Primary Source of GHG Emissions

Biogas composes of predominantly methane (CH4) and carbon dioxide (CO2) gases, a sizeable amount of water vapour (H2O) together with traceable volumes of hydrogen sulphide (H2S), hydrogen and ammonia.

Biogas is produced in the absence of oxygen from anaerobic treatment of palm oil mill effluent (POME) in which organic materials are digested by bacteria.

CH4 contributes more to greenhouse effect in raising global temperature than CO2 does.

Functionality of Biogas Plant

The Group endeavours to minimise the release of biogas into surrounding airspace for the purpose of withholding and converting CH4 into grid electricity for sale.

This energy conversion process is operated through a biogas plant jointly owned by the Group and a 3rd party company.

Besides reducing GHG emissions, the biogas plant also helps to augment revenue generating capacity of the Group.

SCHEMATIC DIAGRAM of BIOGAS PLANT OPERATION

01

PRE TREATMENT

POME is conditioned to achieve parameter values required before entering bio-digester.

  • A screening process removes bigger objects like dirt and fibres;
  • Mixing and pH neutralisation achieves optimal pH of 6.5 to 7.5;
  • Cooling system reduces POME temperature to about 40°C – 50°C

02

Bio-digester

Conditioned POME is pumped into bio-digester to produce biogas and a by-product residue called slurry.

The digester is both air-tight as well as water-tight in the form of either covered lagoon or continuously stirred tank reactor.

02-A

Sedimentation Pond

The anaerobic effluent flows from bio-digester to sedimentation pond where the digested POME separates further into sludge and solids.

A solid removal system extracts out the sludge and solids accumulated in both the bio-digester and sedimentation pond.

03

SRUBBER H2S

Before biogas can generate power, hydrogen sulphide (H2S) must be reduced by scrubber to a level permissible by the gas engine.

This stage is necessary to optimise operation, prevent corrosion and endure lifetime of the gas engine subsequently.

03-A

FLARE

For safety reason, the flare is installed to burn off excess biogas if its production volume exceeds the maximum flow of it allowed to enter gas engine.

Sometimes when the gas engine is offline for maintenance or repair, biogas has nowhere to go but to be released by means of burning or flaring it.

04

Dehumidifier

A gas dehumidifier is used to reduce moisture content by extracting water vapour out of biogas in readiness for its input to gas engine.

In this way, combustion function in gas engine is optimised through prevention of condensation and protection of gas engine against acid formation from reacting water with H2S and oxygen.

A high-quality biogas of low humidity level will promote engine efficiency and economise biogas fuel consumption.

05

Gas Engine

It is an internal combustion engine that runs biogas as fuel, which is fed into the engine for generating electricity.

Gas engine converts energy stored in biogas into mechanical energy to drive alternator or generator for producing electricity.

06

Step-up Transformer

Before electricity is transmitted to a power grid line, a step-up transformer is used to boost voltage and reduce current flow in order to minimise power lost during transmission of electricity over long distance cable line.

07

Grid Electricity Transmission

Electricity produced from renewable energy (RE) resource like biogas is sold to National Grid Malaysia by supplying electricity to the high-voltage electric power transmission network owned by Tenaga Nasional Berhad.

Accounting for GHG Emissions Reduction

The United Nations’ Framework Convention on Climate Change has recognised biogas plant as a Clean Development Mechanism (CDM) used for capturing GHG from emission into environment. In order to quantify reliably the reduction of GHG emissions contributed by biogas plant, the Group applies the following standard equation which is consistent with the recommendation of Malaysian Green Technology Corporation (MGTC) on CDM Electricity Baseline that guides the calculation of Certified Emission Reduction (CER) achievable from implementing biogas power plant.

Emissions Reduction (ER)
= Baseline Emissions (BE) – Project Emissions (PE)

BE refer to a hypothetical scenario in which GHG emissions would reasonably have occurred had there been NO such biogas plant. In other words, BE is GHG emissions in the absence of the biogas project. BE consist of:
  • Emissions from releasing methane into atmosphere; and
  • Emissions from electricity generated by grid-connected power plant.
  PE refer to GHG emissions that would occur if a biogas plant is implemented. PE consist of:
  • Emissions from electricity consumed to capture and burn methane gas;
  • Emissions from burning methane gas; and
  • Emissions from captured but unburnt methane – usually taken as 10% of captured methane.