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Solid Biomass

Solid biomass is defined as any plant matter used directly as fuel or converted into other forms before combustion. Included are wood, vegetal waste (including wood waste and crops used for energy production), bagasse (solids left over from the processing of sugarcane or fruit), straw, grains, animal materials/wastes, sulphite lyes, also known as "black liquor" (an alkaline spent liquor from the digesters in the production of sulphate or soda pulp during the manufacture of paper) and other solid biomass. The fuel can be used directly as for fire or used to power other devices such as electrical generators.

Solid biomass fuel can be used as it is found, but it often benefits from some processing to make it drier or denser than it is in nature. For example, the process of making charcoal transforms wood into a dry substance that is nearly pure carbon. Removing impurities can also improve efficiency.

Whether solid biomass is renewable or not depends entirely on how rapidly it is used. Wood met human energy needs for millennia, but once a forest is completely cut down, it becomes useless until the trees grow back, if they do.

Animal waste

Animal feces, also called manure or dung, is an important source of fuel around the world. Manure contains large amounts of carbon and nutrients that can be used as fertilizer, but it also contains ample plant fiber that will burn. Dried dung is widely used as fuel for fires in areas where there are many animals. Manure can be allowed to decay to produce methane. Animal dung causes especially bad air pollution; the World Health Organization estimates that 1.5 million people have died of inhaling air polluted by burning dung.

Bagasse

Bagasse is the solid material left behind after removing a product from its source, such as juice from oranges or grapes and the sugar from sugarcane. About 30 percent of the sugarcane is left over after processing, and this solid fibrous material has long been used as fuel. In the earliest days of sugarcane processing, the bagasse was used as fuel for the sugar mill; in some cases, the processors would not extract as much sugar as they could from the bagasse so that they would have more bagasse left over to burn.

Bagasse is now an important source of fuel in Brazil. Brazil expanded its sugar industry in the 1970s to make sugar to produce ethanol. The ethanol plants use bagasse to power their machinery. Brazilian sugar growers sell excess bagasse to other industries, such as juice and vegetable oil factories, which burn it instead of fuel oil. This saves the nation several million dollars a year in oil import costs.

Bagasse produces few greenhouse gases. However, burning any renewable biomass fuel causes smoke that can seriously cloud the air in the immediate area. Sugarcane cutters often burn cane fields before cutting down the sugarcane and the resulting smoke can linger in nearby towns for weeks.

Charcoal

Charcoal is the black combustible material made by removing the water and volatile substances from wood or other organic materials. It consists almost entirely of carbon, usually between 85 and 98 percent. The main reason to make wood into charcoal is to make it burn hotter and more efficiently. To make charcoal, wood is buried to prevent oxygen from reaching it and allowing it to catch fire and then baked at a moderate heat for many hours. The impurities burn off in smoky clouds. Commercial charcoal manufacturers add borax to bind (hold together) the charcoal, nitrate to help it catch fire, and lime to color the ashes white.

Garbage

Scientists have been experimenting with ways to turn garbage into fuels or useful substances. Some types of garbage can be converted into biogas, which can be used as fuel. Garbage is also a component of P-Series fuel.

Straw, Grain and Dried Plants

There is some possibility that dried plant matter could be used to manufacture ethanol. Making ethanol from this kind of cellulose (cellular material in plants) is more difficult than making it from sugarcane or grain. Straw and hulls do not contain as much sugar, and it is more difficult to remove the sugar from them, but it is possible. These dried substances can also be made into compost or converted into biogas. They are usually not the best fuels for fires because they burn quickly and cannot produce long-lasting heat.

Wood

Wood is perhaps the oldest solid biomass fuel. In many parts of the world wood is still the primary or the only available source of power. Wood is still a common source of heat in colder climates where it is plentiful -- some homes have wood stoves that burn wood to heat the house. Others have boilers outside the house that pipe heat into the home. Wood had a brief resurgence in popularity after the 1973 oil crisis.

Burning wood does not contribute to greenhouse gases because burning wood releases no more carbon dioxide than can be consumed by growing trees. Modern heating stoves are designed to emit few greenhouse gases. Burning wood does produce ash, but ash can be used as fertilizer or in soap making.

Deforestation is a growing problem around the world. Without enough trees to provide wood, solid biomass fuel will not be a practical source of energy

Solid Biomass Limitations

Naturally, there are difficulties: Biomass is generally bulky and requires a lot of space to store it, not to mention transport of material to the burner etc. Biomass will generally require chopping before combustion is possible, to ensure a good mixture with air. Drying of the material will also be necessary in some cases, which is a problem exacerbated by the fact mentioned above, that biomass tends to be bulky. The mixture of fuels will require some cleaning of the flue gases and regular checks with a combustion analyser to ensure that everything is working as planned
Solid biomass is only renewable as long as it is not consumed faster than it can be replaced. Solid biomass fuels have much lower energy content than fossil fuels, which means that people using them must acquire large quantities of them to do the same jobs that much smaller quantities of fossil fuels can achieve. Coal, for example, burns much hotter than wood and lasts longer. Anyone using solid biomass for home heating and energy must have access and transportation for large quantities of fuel and must be able to store it until it is needed, such as in a woodpile.

Solid Biomass Advantages

The advantages of using biomass are obvious: this is material that would otherwise have been either left to rot (producing CO2) or simply burnt in an uncontrolled manner (producing CO2 as well as smoke and fumes). Since we are apparently going to produce carbon dioxide with this material, whether we use it or not, we might as well use it and gain an advantage from the matter! It is important to add to the calculation the fact that the energy produced here would have to be produced anyway, probably by burning one fossil fuel of other. Biomass is not exactly something for nothing, but it is, in ecological terms, a cheap alternative.
The other use made of biomass is pyrolysis. In this process the material is broken down under heat to produce combustible gases, mainly carbon monoxide and hydrogen. This gas can then be used in normal combustion processes.