CONTENTS • Introduction • What is Biomass • Sources Of Biomass • Biomass Conversion Technology • Advantages • Disadvantages • Applications • References • Conclusion
INTRODUCTION • Many of the developing countries produce huge quantities of agro residues but they are used inefficiently causing extensive pollution to the environment. The major residues are rice husk, coffee husk, coir pith, jute sticks, bagasse, groundnut shells, mustard stalks and cotton stalks. Sawdust, a milling residue is also available in huge quantity. Apart from the problems of transportation, storage, and handling, the direct burning of loose biomass in conventional grates is associated with very low thermal efficiency and widespread air pollution.
WHAT IS BIOMASS? • Biomass is biological material derived from living, or recently living organisms. In the context of biomass for energy this is often used to mean plant based material, but biomass can equally apply to both animal and vegetable derived material. • In ecological studies, biomass is the mass of living organisms present in a particular area or ecosystem. The measurement of the amount of biomass present is handled differently based on the reason for the measure and exactly what the measurement is supposed to mean.
SOURCES OF BIOMASS • Raw materials that can be used to produce biomass fuels are widely available across the world and come from a large number of different sources, and wide variety of forms. • Biomass is carbon, hydrogen and oxygen based. Biomass energy is derived from five distinct energy sources: garbage, wood, waste, landfill gases, and alcohol fuels. • Biomass can be converted to other usable forms of energy like methane gas or transportation fuels like ethanol and biodiesel. Rotting garbage, and agricultural and human waste, release methane gas - also called "landfill gas" or "biogas." Crops like corn and sugar cane can be fermented to produce the transportation fuel, ethanol. Biodiesel, another transportation fuel, can be produced from left-over food products like vegetable oils and animal fats
BIOMASS CONVERSION TECHNOLOGIES • From the time of Prometheus to the present, the most common way to capture the energy from biomass was to burn it to make heat. Since the industrial revolution this biomass fired heat has produced steam power, and more recently this biomass fired steam power has been used to generate electricity. • These methods are used for conversion. • Densification of Biomass • Combustion and incineration • Thermo chemical conversion • Biochemical conversion
DENSIFICATION • Bulky Biomass is reduced to a better volume to weight ratio by compressing in a die at high temp & pressure. • It is shaped into briquettes or pellets to make a more compact source of energy which is easier to transport and store than the natural Biomass. • Pellets and briquettes can be used as clean fuel in domestic chulhas bakeries and hotels.
COMBUSTION • Direct combustion is the main process adopted for utilizing Biomass energy. • It is burnt to produce heat utilized for cooking, space heating industrial processes and for electricity generation. • This utilization method is very inefficient with heat transfer losses of 30-90% of the original energy contain in the Biomass.
INCINERATION • Incineration is process of burning completely the solid Biomass to ashes by high temp oxidation. • Incineration is a special process where the MSW(municipal solid waste) is incinerated to reduce the volume of solid refuse (90%) and to produce heat, steam and electricity. • Waste incineration plants are installed in large cities to dispose off urban refuse and generate energy.
THERMOCHEMICAL CONVERSION. • These are processes in which heat is the dominant mechanism to convert the biomass into another chemical form. The basic alternatives of combustion, torrefaction, pyrolysis, and gasification are separated principally by the extent to which the chemical reactions involved are allowed to proceed (mainly controlled by the availability of oxygen and conversion temperature).
There are a number of other less common, more experimental or proprietary thermal processes that may offer benefits such as hydrothermal upgrading (HTU) and hydroprocessing. Some have been developed for use on high moisture content biomass, including aqueous slurries, and allow them to be converted into more convenient forms. Some of the applications of thermal conversion are combined heat and power (CHP) and co-firing. In a typical biomass power plant, efficiencies range from 20-27%. • A range of chemical processes may be used to convert biomass into other forms, such as to produce a fuel that is more conveniently used, transported or stored, or to exploit some property of the process itself.
BIOCHEMICAL CONVERSION • A microbial electrolysis cell can be used to directly make hydrogen gas from plant matter • As biomass is a natural material, many highly efficient biochemical processes have developed in nature to break down the molecules of which biomass is composed. • Biochemical conversion makes use of the enzymes of bacteria and other micro-organisms to break down biomass. In most cases micro-organisms are used to perform the conversion process: anaerobic digestion, fermentation and composting. Other chemical processes such as converting straight and waste vegetable oils into biodiesel is transesterification. Another way of breaking down biomass is by breaking down the carbohydrates and simple sugars to make alcohol.
ADVANTAGES OF BIOMASS • Biomass is very abundant. It can be found on every square meter of the earth as seaweed, trees or dung. • It is easy to convert to a high energy portable fuel such as alcohol or gas. • It is cheap in contrast to the other energy sources. • Biomass production can often mean the restorations of waste land (e.g. deforested areas). • It may also use areas of unused agricultural land and provide jobs in rural communities. • If it is produced on a renewable basis using biomass energy does not result in a net carbon dioxide increase as plants absorb it when they grow. • It is very low in sulphur reducing the production of acid rain.
DISADVANTAGES • Could contribute a great deal to global warming and particulate pollution if directly burned • Still an expensive source, both in terms of producing the biomass and converting it to alcohols • On a small scale there is most likely a net loss of energy--energy must be put in to grow the plant mass • Agricultural wastes will not be available if the basic crop is no longer grown. • Some Biomass conversion projects are from animal wastes and are relatively small and therefore are limited. • Research is needed to reduce the costs of production of Biomass based fuels.
APPLICATION OF BIOMASS • Biomass is a versatile energy source. It can be used anywhere. • Biomass is an important source of energy and the most important fuel worldwide after coal, oil, and natural gas . • In rural India biomass is used for cooking and agricultural growth • It has been very useful for village households that own cattle. • The use of sugarcane to produce electricity is increasingly being used in Indian sugar mills: this is being done to clean the environment, cut down power costs and earn additional revenue. After the juice has been extracted from the sugarcanes, the leftover pulp - bagasse - is sold to power plants. Here, the bagasse is burned. The energy produced is then provided to the sugar mills.
CONCLUSION • Wood fuels and biomass will be an important source of energy for the next century. • Their use in the industrial and transportation sectors is quite promising, based on credible forecasts and on the present trend observed in several developed and some developing countries. • The main motivation for industrial and transportation use is C air emission caused by burning fossil fuels and their global consequences. • Developing countries, mainly those in the tropics, can take advantage of this fact to improve gains thus allowing a better quality of life of the population.
REFERENCES • ED WARD S.CASSEDY,prospects for sustainable energy. • D.P KOTHARI ,renewable energy sources • B.H KHAN