Biomass can be used to replace coal, oil and natural gas in home heating systems.
Biomass refers to anything that is growing or has been grown, usually plant material.
It has come to mean plant materials or substance made from plant materials that can be burned. Trees, wood, wood chips all count as biomass.
Why Replace Fossil Fuels with Wood-based and Similar Fuels?
Biomass fuels are carbon neutral. This means that they do not contribute towards global climate change. When you burn wood and wood products you do release carbon dioxide into the air, but this is only the carbon dioxide that the tree removed from the air by photosynthesis while it was alive.
Governments are increasing taxes on fossil fuels in a bid to persuade people to use gas rather than oil or coal. Natural gas produces less carbon dioxide for each unit of heat than any other fossil fuel. By switching to wood pellets or some other form of biomass fuels you are going one better and are switching to a carbon neutral fuel for your home heating.
Biomass Replacements for Home Heating
Wood has been around as a home heating fuel since the Stone Age. Burning wood on an open fire is extremely inefficient, but there are much better ways of burning it. A modern room heater extracts nine times more useful heat from every log than an open fire does.
A room heater burns wood based fuels or coal in a cast iron box that has a glass door that can be opened, but which is usually kept closed.
Keeping the glass door shut means that the wood burns more slowly and that all the flammable gases, like carbon monoxide, that are released when the wood is heated also burn. It is these gases burning that gives rise to the small blue flames on the top of the fire. If you open the glass door on a room heater it is not much more efficient than an open fire.
The other big difference between room heaters and open fires is the amount of convected heat from each one.
An open fire gives very little convection, except up the chimney. Most of the heating of the room is by radiation. Radiation travels in straight lines, so you must be close to and directly in front of an open fire to feel much heat.
A wood fuelled room heater passes the hot gases over a ribbed, cast iron heat exchanger to extract heat from them and cool them down before letting them escape up the chimney. The room heater draws in air from the room, passes it over the hot heat exchanger, warming the air, then pushes the warm air back into the room. The warm air circulates around the room by convection, having a similar warming effect to a central heating radiator.
You can buy some combined biomass fuel room heaters and heating boilers, basically a room heater where there are two heat exchangers, the first one taking heat from the waste gases and using it to heat water for your home or home heating, the second heat exchanger taking the still hot gases and extracting more heat from them in order to heat air from the room.
Processed Wood Fuels
Wood has several disadvantages as a biomass fuel.
It is irregular in shape, so is awkward to store. The amount of heat obtainable from a piece of wood depends on the type of tree and on whether it has been seasoned and allowed to dry out.
You can buy biomass briquettes made from compressed wood shavings. These are the size of a house brick. They are stackable, and rectangular in cross-section, so storage and transport is a lot more efficient than unprocessed wood. The biomass briquettes burn in a similar way to wood, leaving little ash.
Wood processors take wood, grind it up, so it has the texture of sawdust, then stick it together, using high pressure, into pellets. The wood pellets have a uniform, small and rounded shape, so they can be moved using belts. Many biomass home heating systems use a large hopper inside the furnace to hold the pellets, which then trickle into the combustion chamber by gravity.
You can have a conveyor belt arrangement that automatically keeps the biomass fuel hopper inside the furnace topped up, or you can fill it by hand once or twice a day.
Wood pellets are bulky to store and MUST be kept dry. They absorb water vapor from the air, so storage in bulk is very difficult, unless they are in an inside, dry storage bunker next to the furnace. The heat from which will keep the pellets dry.
Most people who have biomass heating buy their wood pellets in bags, a few at a time, reducing any cost savings over oil or coal.
Can I use Biomass in My Kitchen Range
If your range is a coal fuelled one you might expect to be able to use wood chips, wood or similar biomass fuels in it. Sadly, range manufacturers advise against this, unless your range has been especially designed to burn biomass you will have to continue burning coal.
Other Biomass Fuels
Research is being done in many countries into turning biomass from agricultural waste, into usable fuels. Agricultural waste being used includes sources as diverse as straw and corn husks. These biomass fuels are not yet widely available
Charcoal is included in the biomass category of fuels, being made by heating wood in the absence of air, so get the charcoal grill out more often and reduce fossil fuel use. Burning charcoal in the open in a grill is as inefficient as burning wood in an open fire, however. In African countries and India special charcoal stoves are being used to reduce the amount of charcoal used and to extract more heat from each piece by burning the gases that are releases by combustion, rather than just letting them escape into the atmosphe