Gas to Energy and the Sao Joao Landfill

Arial View of Sao Joao Landfill 

Unfortunately, I caught a cold and was unable to attend the trip to the Sao Joao landfill.  This landfill is one of the largest in all of Brazil, collecting the 15,000 ton daily trash production of Sao Paulo.  The landfill is an exploratory project in alternative energy generation, producing energy through the combustion of methane gas.  It is currently at full operational capacity and has 24.64 MW of installed capacity spread among 16 turbine-generator systems.  The project consumes a fair amount of energy, and some energy loss is expected during transmission to the grid.  Thus, about 20.9 MW of energy will be transmitted to the Sao Paulo grid after the transmission lines are commissioned.

Generator Room at Sao Joao

There are also environmental and social implications to this project.  Methane gas that would normally contribute to greenhouse gas emissions is now combusted and thus destroyed.  This is done through what is referred to as a LFG (landfill gas) recovery system.  There are also stacks included in the plant design to burn of leftover methane, further preventing emissions.  The link below contains formulas for verifying the greenhouse gas reduction potential of the landfill.  In terms of social value, construction of the plant provided temporary jobs for workers in the area.

Schematic of Methane Gas Energy and LFG Recovery System

The gas is collected from the ground and taken through a condensate knockout step.  This removes water and other contaminates to prepare the gas for use as a fuel.  If the amount of gas coming from the landfill is greater than the generator capacity, the gas is burned of via flare stacks.  This is done rather than retaining the gas because buildup can cause the landfill to explode.  Compressors and coolers are also utilized to condense the gas to a level usable by the internal combustion engines.  

http://cdm.unfccc.int/filestorage/8/O/0/8O01DQS97FACYKBE6LJWNUGVX52ZPM/PDD.PDF?t=RkN8bXFtNzM0fDCrFXbzW35ZMKwT7ufAjtC3