Landfill Gas
Landfill Gas
For many years, landfills have been common method of waste handling. When waste has been
placed in landfill, a process of anaerobic breakdown of wet organic
material starts to take place. It is because of the anaerobic process
that biogas is formed in landfills. Mannvit engineering has designed and procured a biogas upgrading plant in Álfsnes and is currently working on a feasibility study for a plant at Akureyri.
A methane upgrading plant converts the original makeup of landfill gas to biomethane. Before conversion, landfill gas is made up of primarily methane and carbon dioxide,
with methane making up 50-60% of the gas. To produce high calorific gas, carbon dioxide and other contaminants are removed from the
landfill gas in a biogas upgrade plant, producing gas with 95% methane
content, also known as biomethane. The properties of biomethane gas
are similar to natural gas and can be utilized as vehicle fuel or input
directly into the local gas grid.
To extract the biogas from the landfill, boreholes were drilled in the
landfill and polyethylene gas wells inserted. Biogas is then extracted
by applying active suction to the wells. Careful control of the
suction pressure and gas composition is a key factor for optimum
results.
Methane gas production started in 2001 at Alfsnes with a small biogas
upgrading facility. Demand quickly increased so a new upgrade plant
was erected in 2005. The new biogas upgrade plant was fully designed
and procured by Mannvit Engineering. The plant utilizes a SCADA system
and can be monitored and operated on-line. The plant has proven to be
very reliable with minimum downtime, a testimony to the expertise and
know-how of Mannvit's design and equipment selection.
At the Álfsnes site in Iceland, landfill gas can either be utilized
directly for electrical production or sent to the biogas upgrading
plant where the landfill gas is upgraded to biomethane gas, which can
used as vehicle fuel. When landfill gas is used for generating
electricity, a considerable amount of waste heat is generated. This
waste heat can be utilized for district heating.
The plant at Álfsnes is capable of handling up to 800 m³/h of landfill
gas, which corresponds to 450 m³/h of biomethane gas. The energy
content is comparable to 400 l/h of petrol.
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