Biomass
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Biomass boilers work on the same principle as gas boilers. They burn biomass (such as woodchip, wood pellets or straw), bio-diesels (such as rapeseed oil, vegetable oil) or bio-gases (such as bio-methane) to provide heat in a similar way as coal, oil or gas fired boilers or alternatively in a stand alone, more traditional stove. They can be used on a range of scales from district heating to domestic. Solid biomass can be converted to liquid or gas fuels by biological or thermal methods (see energy from waste). Biomass can also be used in CHP or CCHP or in combination with fossil fuel eg in power stations (co-firing).
Types
- Various fuels
- Stoves and boilers, range of sizes
Other components Fuel store and delivery area Hot water cylinder (thermal store) External flue for exhaust gases, above the roofline
Typical savingThere are no energy savings as bio-fuel boilers are typically as or less efficient than gas-fired boilers. However, bio-fuelled heating is considered low carbon or zero carbon as the bio-fuel usually absorbs similar amounts of CO2 in its growth as it gives off in its combustion. Transport and processing of the bio-fuels does result in some emissions, so the savings vary. The Building Regulations assume emission factors of 0.025 kgCO2/kWh for biomass heating compared to 0.194 kgCO2/kWh for natural gas and 0.422 kgCO2/kWh for grid electricity.
Indicative cost
Biomass boilers usually more expensive than conventional boilers and require fuel store. Costs vary from £100 /kW to £320/kW for biomass boilers from 50 - 1250kW. Unlikely to achieve major fuel cost savings using biomass/biogas unless the fuel is a free waste product.
Main issues affecting feasibility
- Heat demand: Can serve all heat and hot water demand, but requires a relatively steady load as slower to respond to demand than gas boilers.
- Fuel source: Local, sustainable fuel source should be used to reduce transport and other associated impacts. May not suit city centre locations.
- Emissions: Nitrous oxide emissions can be higher than gas boilers.
