Biomass to replace oil?
Posted by jingoisticbuthornydesperado on January 14, 2009
Human civilisation has been increasingly becoming ever more reliant on fossil fuel as primary energy source to sustain its own growth and comfort. However, the usage of fossil fuel is unsustainable as it converts large amount of carbon fuel into carbon dioxide, which would otherwise be stored in natural carbon reservoirs deep inside the earth crust.
Biomass is a much cleaner alternative to fossil fuel as it does not directly interfere with the natural carbon cycle, i.e. since biomass will either decay or be consumed as food source by organisms releasing carbon dioxide anyway, using biomass as fuel source does not increase the aggregate amount of carbon dioxide in the atmosphere. Usage of biomass in energy industry had not been economically appealing because fossil fuel is cheaper. It is only when fossil fuel becomes more expensive, then only does biomass appear to be more economically attractive. Although price of oil has taken a turn downwards of late, it is projected to go up again late 2009 (as forecasted by BP and Shell), hence biomass appeal will not wane.
The cheapest use of biomass comes from waste products such as wood bark, sawmill dust and waste cooking oil. These products do not compete with agricultural food products, neither do they occupy fertile land specifically for food purposes, hence they are not ethically controversial unlike the usage ‘sugarcane to ethanol’ in Brazil or ‘palm-oil to bio-diesel’ in Indonesia and Malaysia. Another potential benefit is that it does not directly require large swathes of biologically diverse rainforest to be deforested and converted for agricultural use.
Gasification converts biomass to syngas (in the form of hydrogen and methane gas) with tar and char as waste products. Tar in syngas is undesirable as it can potentially foul gas combustor and fuel cell. The amount of tar can be reduced by using catalysts such as dolomite and nickel, producing more syngas as a result. The char can be recycled back for further gasification.
Apart from having a cheap source of biomass, it is also vital to have a technologically reliable process with good investment opportunity. Fluid bed technology scores well in both technological strength and market attractiveness.
Also, using fluid bed for gasification is essentially a self-sustaining process, i.e, the amount of heat it produces from partial burning of biomass is more than enough to offset the heat it consumes to produce syngas. Otherwise, it will be an idiotically oxymoronic to use fossil fuel to generate syngas from biomass.