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Unformatted text preview: plants with
capacities between 10-700 m3/hr have been started, producing vehicle fuel mainly from
sewage sludge. Biogas as a vehicle fuel is free from fuel tax and thus competitive to the
traditional fuels. The Laholm co-digestion plant with a capacity of 250 m3/hr is
producing natural gas quality from biogas since 2000, by upgrading biogas and adding
propane to correct the heating value and Wobbe-index. In France two upgrading plants,
with a capacity of 100 respectively 200 m3/hr are in operation since 1994 respectively
1995, making vehicle fuel from sewage sludge, or landfill gas. Development of
biogas and development of a broader natural gas vehicle market can be mutually
supportive. The broader market development creates the basis for broader use of
biogas, and development of biogas supplies in areas without natural gas distribution
will make it possible to use natural gas vehicles practically anywhere in Europe.
BIOMASS GASIFICATION IN SUPERCRITICAL WATER
Wet biomass (70-95 wt.% water) may not be converted economically by traditional
techniques like pyrolysis, combustion, and gasification, due to the cost and energy
requirement for mechanical liquid-solid separation, as well as water evaporation (2.4
MJ/kg at atmospheric conditions). Gasification in hot compressed water is considered
as a promising technique to convert such wet streams into medium calorific gas, rich in
either hydrogen or methane. At temperatures and pressures above the critical point of
water (Tc = 373.95oC, Pc = 220.64 bar) there is no distinction between gas phase and
liquid phase. Also the behaviour of water will change considerably at these
supercritical conditions, and water will even be consumed as a reactant.
Supercritical water gasification (SCWG) is an alternative route for wet biomass
streams, which are converted via anaerobic digestion. According to van de Beld et al
about 25% of the Dutch biomass-related sustainable energy targets in 2020 could be
realised by optimal use of the available wet biomass streams in the Netherlands.
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This essay was uploaded on 03/18/2014 for the course ENG 316K taught by Professor Kruppa during the Spring '08 term at University of Texas.
- Spring '08
- Chemical Engineering