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Eco Construcion Bio Mass and Bio Fuels PDF Print E-mail
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Biomass and biofuels:

These are renewable organic fuels from harvested crops -the CO2 released when energy is generated is balanced by that absorbed during the growth of the fuel material. Fuels include woody biomass crops such as coppiced willow, high energy crops such as sugar cane or maize, or animal waste. The Basics of Biomass
 
Biomass

 is the generic term used to describe solid fuels sourced from recently grown material. 

Biomass fuels shouldn't be considered to be 'new' or 'alternative' fuels -in fact they were burnt for fuel thousands of years before fossil fuels were. When fossil fuels are burnt, they release long locked-up carbon back into the atmosphere, whereas in the case of of bio-fuels carbon released when energy is generated is balanced by that absorbed during the growth of the fuel material.
 
The term Biomass covers plant material such as miscanthus and grains as well as woody material such as coppiced willow and wood pellets, and high energy crops such as sugar cane or maize, or animal waste.
 
The commonest biomass fuel is wood -although relatively slow growing in comparison to grasses such as miscanthus, it is an excellent biomass fuel source.  Woody biomass has comparatively high energy density compared to other biomass fuels.  The prevalence of wood processing operations in existing industries such as construction, transportation, and furniture which produce large amounts of waste which are ideal sources of fuel.  Rather than paying the costs of removing waste material, it can be turned into a saleable by product for wood processors and manufacturers.  This is a major benefit to wood fuels as its does not rely solely on agricultural production to provide fuel nor does it take up agricultural land which could be used to produce food. 
 
Most biomass fuels do require some form of processing. Grasses, woody material and seeds can be milled into pellets. Wood can be chopped to length and split, chipped or pelletised in order for it to be burnt.  Grasses can also be baled and burnt whole or be milled into pellets.  The production of fuel pellets is essentially the same as the production of pellets for animal feeds.  The stock material is dried and ground to produce a dust which is then fed through a die to produce the required size of pellet.  Wood pellets do not require any binding agent to be added as the lignin present in the cells of the wood binds the material together when subjected to the high temperatures and pressures found in the pellet mill.      
  
Clifford Jones timber have recently commissioned a Wood pellet mill in Wales (pictured). Using a biomass boiler to produce the heat and power required for the production process, the carbon impact of the plant is significantly reduced.
 
Due to processing and delivery operations biomass is not 100% carbon neutral, however it is classed as being carbon neutral as the emissions factors for biomass fuels are significantly lower that that of fossil fuels for example:
 
A large house using 25,000kWh for heating:
 
Using mains Gas:      25000    x   0.194        = 4850Kg/CO2
 
Using Oil:                   25000    x   0.27          = 6750Kg/CO2    
 
Using Wood Pellets: 25000     x   0.025        =   625Kg/CO2
 
Wood Pellets produce 10.8 times less CO2 than Oil
And 7.76 times less CO2 than Mains Gas
Wood Pellets would have to be transported at least 3000km by lorry before they have the same CO2 emissions per tonne as mains gas.
 
What kind of system will I require?
 
Biomass fuels can be used in various types of appliance, ranging from a basic wood burning stove to a combined heat and power plant producing 2 MWel, for example.  There are several types of boiler design available, each suited to specific applications. 

For instance smaller domestic boilers are likely to be either manually fed, such as log gasification boilers which require fuel to be loaded and ignited by hand for each batch of fuel.  Automatic feed systems which are available for wood pellet boilers which will ignite/extinguish and modulate their output without input from the user. 

The boiler designs for larger output boilers are usually less compact and will accept less homogenous fuels such as wood chip, waste such as forest residues, seeds and grain and combinations of biomass fuels. The larger output stepped grate and fluidised bed combustion boilers are not usually economically viable below 500kWth, unless there is a constant demand for heat, such as an industrial process. 

The initial capital outlay of all biomass systems is a major influence on the selection of type of plant to be installed.  The balance between the initial cost and the payback time of a system may make a certain type of biomass system uneconomical.  
  
The space required for fuel storage as well as space for a delivery vehicle access to the fuel store must also be considered when planning a biomass installation. In the domestic market many properties currently on oil will already have their fuel stored on site and will have access for delivery vehicles, conversely a property with a mains gas supply in an urban environment may not have the space required to install a biomass system. 

In the urban setting district or community heating may be more appropriate.  This solution may use a large biomass boiler or a combination of heat recovery, from an industrial process, and biomass to provide heating for a number of properties.  This scale installation also lends its self to combined heat and power (C.H.P) installations which provide both heating and electrical power.

Smaller appliances for use in the domestic setting are usually fired from high quality wood fuels.  The higher energy densities of wood fuels such as wood pellets, when compared to bagasse pellets for example, are more suited to the domestic setting as they require a low volume of storage.  The low levels of ash produced from modern high efficiency boilers reduce the amount of cleaning required and allow compact boiler designs to be produced.  

The homogenous nature of wood pellets allows ease of handling and delivery to the customer.  Wood fuels are non-volatile, non toxic and present few hazards to the user or distributor.  The end-user experience of wood pellet appliances is potentially much like that of a gas or oil boiler as automatic fuel feed, ash cleaning and removal are available on boilers such as the Windhager BioWIN Automatic wood pellet boiler (pictured).
 
 
Biomass fuels

should be sourced as locally as possible, for example it is not good practice to switch from oil or gas in the UK and then source fuel from South America, for instance.  The prevalence of timber processing as well as managed forests make woody biomass is the obvious choice for use as a renewable fuel within the UK. 

Logs can be sourced from local timber suppliers, from your own woodland or as a by product of your job or business. Wood pellet mills and suppliers are increasing in number each year, The market for wood pellets in Europe is currently expanding, the instability of oil prices has helped to stimulate market growth.  The indexing of the price of pellets to the price oil undermines wood pellet's selling point as being a stable priced, better value alternative to oil. 

As the market develops, pellets and other biomass fuels should be traded as commodities in their own right as they can be sourced from local supplies and do not require large amounts of fossil fuels to produce or deliver them to the end user.   

 
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