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BIOMASS ENERGY

IMPORTANCE:• Biomass materials are used since millennia for meeting

myriad human needs including energy.• Until the middle of 19th century, biomass energy dominated

the global energy supply with a seventy percent share.INTRODUCTION:• Biomass means all materials which come from living

organisms. For inst, waste materials of plants and animals, wood agricultural waste , dead parts of plants & animals.

• Since all the living organisms contain carbon compounds, biomass energy stored in the form of chemical compounds.

• The method of harnessing energy form each one of them can be different.

• During burning of these materials generally causes pollution but can be cheapest form of energy.

BIOFUELS• Bio fuel is the energy recovered from biomass organic matter.• We can divide bio fuels into three groups:

• Fire wood• Organic waste• Liquid fuel

These bio fuels in turn have various energy sources, uses and products. They are:

• Fire wood is the natural wood obtained from trees.• Organic waste comes from two sources animal residues ,

urban man made waste.• Liquid fuel is one of the most widely used bio fuel as it is

obtained from variety of crops and trees.

Examples of biomass energy sources, uses & products

SOURCES EXAMPLES USES/PRODUCTS COMMENTS

Forest products Wood chips Direct burning, charcoal

Major source today in developing countries.

Agricultural waste Coconut husks, sugarcane waste, corncobs, peanut shells

Direct burning Minor source

Energy crops Sugarcane corn, sorghum

Ethanol(alcohol):gasification

Ethanol is major source of fuel in brazil for automobiles

Trees Palm oil biodiesel Fuel for vehicles

Animal residues manure methane Used to run farm machinery

Urban waste Waste paper, organic household waste

Direct burning of methane from wastewater treatment or from landfills

minor source

A DETAILED DISCRIPTION OF SOURCES OF BIOMASS ARE GIVEN

BELOW

FOREST PRODUCTS- WOOD FUEL• The burning of wood is currently the largest use of energy derived

from a solid fuel biomass.• Wood fuel can be used for cooking and heating, and occasionally for

fuelling steam engines and steam turbines that generate electricity.• Wood fuel may be available as firewood, charcoal, chips,

sheets, pellets, and sawdust.• The particular form used depends upon factors such as source,

quantity, quality and application.• Some consider wood fuel bad for the environment, however this is

not the case if proper techniques are used.• One might increase carbon emissions using gas powered saws and

splitters in the production of firewood, but when wood heat replaces carbon-producing fuels such as propane, heating oil or electricity from a coal-burning plant, then wood burning has a positive impact on the carbon footprint.

ADVANTAGES OF WOOD FUEL:• As with any fire, burning wood fuel creates numerous by-products, some

of which may be useful (heat and steam), and others that are undesirable, irritating or dangerous.

• The principle economic advantage of wood biomass energy is that wood is usually significantly less expensive than competing fossil fuels.

• Other advantages include the fact that the amount of carbon dioxide (CO2) emitted during the burning process is typically 90% less than when burning fossil fuel. Wood fuel contains minimal amounts of sulphur and heavy metals. It is not a threat to acid rain pollution, and particulate emissions are controllable.

DISADVANTAGES OF WOOD FUEL:• Smoke, containing water vapour, carbon dioxide and other chemicals

and aerosol particulates, can be an irritating (and potentially dangerous) by-product of partially burnt wood fuel.

• l. A major component of wood smoke is fine particles that may account for a large portion of particulate air pollution in some regions.

• Agricultural residues are of a wide variety of types, and the most appropriate energy conversion technologies and handling protocols vary from type to type. The most significant division is between those residues that are predominantly dry (such as straw) and those that are wet (such as animal slurry).

Sources of agricultural residues:Many agricultural crops and processes yield residues that can potentially be used for energy applications, in a number of ways. Sources can include• Arable crop residues such as straw or husks • Animal manures and slurries • Animal bedding such as poultry litter • Most organic material from excess production or insufficient

market, such as grass silage.

AGRICULTURAL WASTE

•Agricultural residues are divided into two kinds •WET RESIDUES•DRY RESIDUES

DRY RESIDUES• These include those parts of arable crops not to

be used for the primary purpose of producing food, feed or fibre, used animal bedding and feathers:

• Straw• Corn Stover• Poultry litter

StrawStraw is typically obtained at around 15-25% moisture content and has a net calorific value (net CV or lower heating value (LHV)) (when dry) of around 18MJ/kg. It also tends to contain high levels of nutrients as a result of the timing of harvesting, and of silica, which gives a relatively high ash content (around 5%) and can lead to slagging and fouling problems in combustion.• Straw can be used in a range of energy conversion technologies:• Ethanol production (via cellulose process)Corn Stover• Stover is the stalk and leaf residues from harvesting maize for grain, and it may be

used as a biomass source in the same ways as straw.Poultry litter• This most commonly consists of the wood shavings or straw used in deep litter

broiler houses, together with the accumulated droppings.• poultry litter should be maintained in good condition to ensure a healthy flock,

keeping moisture, fat and nitrogen content down, requiring litter to be changed regularly. Poor water drinker design or ventilation can lead to high moisture content, but this should not be allowed to exceed 46%.

• At present the most common energy application for poultry litter is combustion in dedicated power stations for electricity production, however it can also be burned on a smaller scale for heat or combined heat and power.

Wet residues

• These are residues and wastes that have a high water content as collected.

• This makes them energetically inefficient to use for combustion or gasification, and financially and energetically costly to transport. It is therefore preferable to process them close to production, and to use processes that can make use of biomass in an aqueous environment.

Typical wet residues include:• Animal slurry and farmyard manure • Grass silage

Animal slurry and farmyard manure

• Manures collected from animals such as cattle and pigs during periods of the year when they are housed, typically contain 6-10% dry matter and so are not appropriate for combustion or gasification without energetically and financially costly drying.

• They are also inefficient to transport any distance or store owing to the high proportion of water.

• The high water, and low dry matter content means that the most appropriate energy technology for making use of animal slurries is anaerobic digestion for the production of biogas.

TransportationAnimal slurry can be transported by tanker and pumped into and out of storage receptacles.

Energy crops• An energy crop is a plant grown as a low-cost and

low-maintenance harvest used to make biofuels, or combusted for its energy content to generate electricity or heat. Energy crops are generally categorized as woody or herbaceous plants; many of the latter are grasses.

• Energy crops of this sort can be used in conventional power stations or specialised electricity generation units, reducing the amount of fossil fuel-derived carbon dioxide emissions.

Types of biomass from energy crops

• Solid biomass• Liquid biomass• Gas biomass

Solid biomassEnergy generated by burning plants grown for the purpose, often after the dry matter is pelletized. Energy crops are used for firing power plants, either alone or co-fired with other fuels. Alternatively they may be used for heat or combined heat and power (CHP) production.Example: Elephant grass (Miscanthus sinensis) is an experimental energy crop

Gas biomass (methane)• Energy crops can also be

grown to boost gas yields where feedstock's have a low energy content, such as manures and spoiled grain.

• It is estimated that the energy yield presently of bioenergy crops converted via silage to methane is about 2 GWh/km².

• Anaerobic digesters or biogas plants can be directly supplemented with energy crops once they have been ensiled into silage

Liquid biomass (biodiesel)• Liquid biomass can be

an alternative source for diesel and petrol.

• Ethanol produced from fermenting corn , sugarcane etc. can generate biodiesel which can be used in automobiles.

• Although the Efficiency of biodiesel is still argued because of problems of harvesting and processing the ethanol is used as one of the mail sources of fuel In brazil .

ANIMAL RESIDUES

Animal slurry and farmyard manure• Manures collected from animals such as cattle and pigs

during periods of the year when they are housed, typically contain 6-10% dry matter and so are not appropriate for combustion or gasification without energetically and financially costly drying.

• They are also inefficient to transport any distance or store owing to the high proportion of water.

• However some energy technologies make use of biomass in an aqueous slurry, and these can make efficient use of such 'wet' materials.

• The high water, and low dry matter content means that the most appropriate energy technology for making use of animal slurries is anaerobic digestion for the production of biogas.

Types of cattle from which biomass is derived are:

Dairy cattle: Dairy cattle typically produce between 42 kg and 64 kg (depending on body weight) of manure per day, so if they are housed for 50% of the year that corresponds to 7.6-11.6 tonnes pa per cow. Between them the UK herd of 2 million dairy cows produces around 20 million tonnes of slurry, equivalent to around 2 million tonnes of dry matter (at 10%).Beef cattle: The resource from the UK beef herd of 1.8 million will be less, as they typically spend less time housed, though may still be in excess of 5 million tonnes (wet) pa.Pigs and sheep: There are also 4.9 million pigs in the UK and 20 million sheep. However, as sheep are kept almost entirely outdoors collecting their manure may not be practical.

Types of cattle from which biomass is derived are:

Poultry litter: This most commonly consists of the wood shavings or straw used in deep litter broiler houses, together with the accumulated droppings.At present the most common energy application for poultry litter is combustion in dedicated power stations for electricity production, however it can also be burned on a smaller scale for heat or combined heat and power.

Biomass from Urban waste

Urban waste Municipal Solid Waste:• During the course of everyday living, society generates a number of

waste products including glass, plastic, paper, aluminium and other metal cans, yard clippings, wood, construction materials, etc.

• A number of these products are recycled, but the majority are disposed of in landfills. Some of these materials, most notably wood, could be recovered and used for bioenergy and bio products.

• Waste material generation is not limited to cities, but is most concentrated there due to the high density of population, thus these wastes are often referred to as urban wastes - even though they can include wastes generated in rural and non-metropolitan areas as well.

• Most ordinary household waste (i.e., garbage or trash) is classified as municipal solid waste (MSW) and is disposed of in MSW landfills.

Urban waste Landfill Gas:• Landfill gas is the by-product of the decomposition

of solid wastes in landfills.• It is composed primarily of carbon dioxide and

methane.• The U.S. Environmental Protection Agency reports

that as of December, 2005 there were 395 operational landfill energy projects in the U.S. Two-thirds of these facilities generated electricity for use onsite or for sale to the electrical grid (EPA, 2007).

Urban waste• Refuse Derived Fuel:• Refuse derived fuel (RDF) is produced by processing

municipal solid waste to increase the fuel value of the waste. • The processing removes non-combustible materials (e.g.,

inorganic materials such as glass and metal) as well as wet organic materials (e.g., food scraps) and creates a consistent sized feedstock.

• Materials contained in RDF generally include textiles, paper and cardboard, wood, and plastics. Sometimes other petroleum derived wastes, such as tires, are included.

• The RDF can be combusted by itself in waste-to-energy facilities or co-fired with other materials (such as coal) to produce electricity.

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