Types of sources of bioenergy biomass
Biomass is the total mass of organic substances that occur in a habitat. There are various types of biomass on the planet, which can be used in different ways. Examples of uses of biomass are the food industry, in the manufacturing process of various products or in construction.
When their original use is over, the biomass can be used in a minor way to the generation of energy. For example, the organic wastes that are a mixture of wasted material, can be used as a source of renewable energy.
The energy contained in organic waste is often used through the generation of biogas. In landfills, it happens to the conversion of part of the organic waste into methane which is normally wasted. In some cases, however, it may be advantageous for the fermentation direct these waste treatment systems anaerobic. Waste with a high content of wood can also be dried and burned as a solid fuel.
A study area of applications of biomass is the creation of crops for energy purposes, planted to be used directly as a fuel. This issue will be discussed in the following sections, by analysing the various types of biomass sources.
Sources of biomass
Biomass can be classified into four categories according to their origin:
Cultures for the purposes of power generation: they are cultivated for the production of energy. Its function is to capture solar radiation to store it in biomass. Examples of crops for energy are rapeseed, sunflower and corn.
Agricultural and forestry residues: Are wastes that are generated naturally in the grain harvest, and the harvesting of trees, such as straw and wood waste. This group of ?sub-products? is especially suitable for recycling with the purpose of power generation, because it reduces the costs of production of the main products, or increases the efficiency of the chain of cultivation
The Sub-organic products: processing of biomass to create products, form an additional group of sub-products. These sub-products include organic waste, the effluents of agricultural and industrial processing wastes wood and vegetable fibers. In these cases, the recycling for energy generation may lead to an increase of the utility and ensure that parts of the production process are permanent, and environmentally sustainable.
Organic waste: Examples are household waste, sludges industrial and domestic wastewater, the waste of food production. These wastes are generally subject to the respective legislation. Consequently, they must be met all the legal requirements, the origin to the control's epidemic of waste.
The plant biomass is generally in the solid state. It features geometric forms and a water content that, in the majority of cases and for technical reasons, it interferes directly in its use for power generation.
The sources of biomass used as fuels are classified according to the state of aggregation in which they are found: solid, liquid, or gaseous.
The state of existing aggregation determines the possibilities of use of sources of biomass and the type of infrastructure of power generation required. The heat exchangers or combustion systems that combine heat and power are able to use solid fuels, while the combustion engines are unable to.
The shape and state of aggregation of the products of biomass processed are determined by the technologies and conversion systems available.
In the process of transformation of biomass into energy, there are methods of operation that are optimized for each type of use, characteristics of the biomass and particular levels of performance.
To obtain an efficient operation, these levels and characteristics must be kept within strict limits.
Use of biomass sources
There are three forms of energy fundamental: heat energy, mechanical energy and electrical energy, and they can all be obtained through the sources of biomass.
There are many possibilities for the generation of the forms of energy desired, the sources of biomass, in different states of aggregation.
Usually the heat is produced in combustion systems. On a small scale, these systems can warm a room, while that on a large scale, the heat generated in a central and through distribution networks can heat the homes of several blocks of a city.
For combustion systems stationary, whose sole function is the production of heat is dominated by solid fuels, in respect to biomass. The wood, such as waste or raw material, can be used for heat generation, with low costs of processing, milling, or drying.
The mechanical energy is produced by means of generators of heat and energy, as the combustion engines. In these, the liquid fuel or gas is ignited in the cylinders, and expansion of the fuel/air mixture, caused by the combustion is then converted into energy. The heat produced by this process must be dissipated to the environment through a cooling system.
The use of biodiesel in Europe, as for example, a mixture of ethanol in France and the use of ethanol pure, in Brazil, are examples of the use of biomass sources with success, in the transport sector.
With the vegetable oils extracted sunflower seeds and other oilseeds, and the alcohol produced biomass, it is possible to cover the needs of fuel for locomotion. The biomass fuels are a viable alternative, equivalent to the fossil energy sources.
The systems that produce mechanical energy such as combustion engines or combustion turbines, direct and indirect, are coupled to electric generators, which convert mechanical energy into electrical energy.
The use of mechanical energy for electrical power production generates approximately two-thirds of the heat for a third of electricity, that shows the increase of the economic efficiency of cogeneration (simultaneous production of heat and electricity in stationary applications.
The biogas the landfill of waste, recycling of agricultural waste or other organic waste, can be used in the central stationary energy production.
Sources of solid biomass
The largest source of waste solid biomass wood processing. The residuals are obtained when the wood is taken out of the forests and in the industrial processing of wood products. In many locations, other sources of biomass such as straw are also used to produce energy.
In the thinning of the forests in addition to the trunks of the trees that are used for the industries of furniture and construction, are also collected waste wood of lower quality. In each forest hectare, these residues can be obtained the 0.4 - 0.8 tonnes of wood dry. In addition, other maintenance actions in the forest to generate wood waste annually of about 1.5 tons per hectare for a forest area for permanent use.
In the forestry the trees are felled with the aid of machines, that use an arm with a saw attached. In addition, these machines can automatically remove the branches the trunk, remove the bark and cut the stem into pieces. This method provides that part of the processing of timber is carried out before the timber out of the forest.
When the trunks round are transformed into planks and beams, are produced large quantities of waste. However, most of these is used in the wood industry for other purposes. Wood chips without bark, for example, are raw material for manufacturing coal of high quality.
However, another part of these wastes continues to have impurities and is, therefore, unsuitable for use as a raw material. These pieces of bark are ideal for recycling for energy generation. Due to the high ash content, these wastes are mainly used in large power plants heat supply and cogeneration plants, as a substrate for co-heating.
Other waste is significant, coming agriculture, which include straw and hay. The residues of post-harvest are usually available at the local level and in large quantities.