subject: UPGRADING BIOMASS BY TORREFACTION (1) [print this page] UPGRADING BIOMASS BY TORREFACTION (1) UPGRADING BIOMASS BY TORREFACTION (1)
In the last decades, energy demand is growth significantly. It is because increasing of economic activity in the world influenced this demand by countries. Energy consumption has exceeded over than 400 EJ annually. As IEA (International Energy Agency) reports, the world's energy demand will increase by 45% until 2030. The position of fossil energy reaching 80% and oil fuel continues to dominate. Furthermore, the reserve of fossil fuel keeps depleting.
Actually, excessive use of fossil fuel has caused global warming, causing changes in climate and, therefore, creating distortion in the environment as well as threatening all living creatures. The use of renewable energy is a strategic method to increase competitive energy production cost. In addition, the implementation of Kyoto Protocol which has elaborated in the Copenhagen meeting (COP15) has encouraged all developed countries to conduct a ratification of the protocol and responsibility upon the decrease in emission.
One of the renewable energies undergoing a significant increase is biomass. Biomass is a term for all organic material that stems from plants (including algae, trees and crops). It belongs to renewable sources. Its availability is unlimited as long as the regenerating process is conducted well.
Biomass fuel is also more environments friendly compared to fossil fuel since the CO2 emission it releases to the atmosphere will be reabsorbed. It is called carbon neutral. Consequently, it will prevent excessive accumulation of carbon dioxide in the atmosphere.
Biomass is characterized by its flexibility in nature to be transformed into certain forms of energy. The technologies used to convert the biomass into certain forms of energy are those of thermochemical and biochemical. The former consists of combustion, gasification, pyrolysis and hydroliquifaction. The biochemical process used an anaerobic digestion to generate biogas and fermentation to produce ethanol.
Combustion constitutes the simplest conversion process compared to others. However, it has the disadvantage in the form of the high rate of moisture and low energy density. Gasification is the process of converting biomass into combustible gas mixture through partial oxidation at the high temperatures. Gasification produces synthetic gas such as carbon dioxide, carbon monoxide, methane and hydrogen.
Other technologies are pyrolysis meaning that a chemical process of decomposing biomass to produce bio-oil in the absence of oxygen at temperature ranges of 300 - 650 C. Through thermochemical biomass gain options as direct feedstock gasification, combustion, pyrolysis or liquefaction. However, each of the processes has its own disadvantages. For example, in the gasification process there will be disadvantages such as tar yield, inefficiency in heat rate and high moisture. Some of the gasification process requires biomass with small-sized particles. The smaller the biomass size, the better would be the heat transfer. It is because the grind ability of biomass is critical to gasification process.
