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Why there are no Dry Anerobic Digestors in the US

posted Mar 25, 2010, 5:28 PM by Bob Wenzlau   [ updated Mar 25, 2010, 5:30 PM ]
Until recently, in the US it has simply been cheaper to landfill waste.  With no price on carbon and little emphasis on GHG reductions, the US has not been a leader in adopting these conversion technologies.  

There are several generation/variants of anaerobic digestion.  The oldest technology is known as "wet" anaerobic digestion, and is widely deployed worldwide, including in the US where it is used primarily for animal manure or sewage sludge -- there are numerous digesters associated with dairy farms, for example, and many associated with wastewater treatment plants.   The process is called wet because the material being processed is basically the consistency of soup.  

In the 90's, a new type of "dry" digesters came onto the market in Europe.  This is the lineage we are talking about for Palo Alto.  There are over 70 full-scale dry anaerobic facilities in more than ten countries in Europe and Asia, processing over 2 million tons per year of sewage, municipal organic waste, and yard waste.  There are at least five significant vendors providing the technology for these installations.  We have looked most closely at technology from a company called BEKON, which has what we think is the newest generation of digester that is particularly appropriate to Palo Alto's mix of wastes.  BEKON currently has 16 installations in Germany, Switzerland and Italy.  

A convergence of RPS requirements, landfill diversion requirements, and concern over GHGs has suddenly made this technology very interesting in the US, and I think we will see many new deployments over the next decade.  I do not believe the technology risk is very high, but that is in part what a feasibility study should consider.