Topics: Biomass types, Characterization, Conversion routes, Bio chemical

9. BIOMASS ENERGY

Biomass is biological/organic material derived from living, or recently living organisms. (The term is equally applicable to both animal and vegetable derived material, but in the context of energy, it refers to plant based material)

Renewable energy source Stored in form of complex organic compounds of Carbon,

Hydrogen, Oxygen and Nitrogen etc. It is a source of ‘5F’: food, fodder, fuel, fiber and fertilizer. It can be converted into useful forms of energy through

different conversion routes. Gets converted into fossil fuels after several million years

under certain conditions of pressure, temperature, air etc. fossil fuels are not renewable, hence, are not biomass.

BIOMASS

Wood: Trees, bushes, wood residue (Sawdust, bark etc. from forest clearings and mills)

Wastes: Municipal Solid Waste (Paper, food and yard wastes, plastics, wood and tires), Livestock Waste, Process Waste, Sewage

Crops: Starch crops (Corn, wheat and barley), Sugar crops (Cane and beet), Forage crops (Grasses, alfalfa, and clover), Oilseed crops (soybean, sunflower, safflower )

Aquatic Plants: Algae, Water weed, Water hyacinth, Reed and rushes

EXAMPLES OF BIOMASS

Living biomass in plants and trees absorbs carbon dioxide from the atmosphere through photosynthesis

Biomass emits carbon dioxide when it naturally decays and when it is used as an energy source

Biomass causes a closed cycle with no net emissions of greenhouse gases

BIOMASS AND CARBON EMMISIONS

Energy obtained from biomass is called biomass energy.

Produced by green plants through photosynthesis in presence of sun light

Other living organisms consume green plants or their byproduct and generate biomass

BIOMASS ENERGY

6CO2 + 6H2O (CH2O)6 + 6O2 + 636 kCal (biomass)

Sunlight

Chlorophyll t

ORIGIN OF BIOMASS ENERGY

Derived from biological carbon fixation of biomass

Examples are Bioalcohols Biodiesel Green diesel Biogas Solid bio-fuels

BIO-FUEL

Bioalcohols Produced by the action of microorganisms and

enzymes through the fermentation of sugars or starches or cellulose

Biodiesel Produced from oils or fats using

transesterification Green diesel

Produced from traditional fractional distillation to process the oils of canola, algae, jatropha and salicornia

BIO-FUEL (contd…)

Biogas Produced by the process of anaerobic

digestion of biodegradable waste materials or energy crops

The solid byproduct can be used as a biofuel or a fertilizer.

Solid biofuels Raw biomass is burnt directly in a stove or

furnace to provide heat Loose biomass (saw dust, rice husk) is

densified by palletization/briquetting.

BIO-FUEL (contd…)

The raw biomass for extracting secondary energy (fuel, organic chemicals, etc.) is called biomass energy resources.

Biomass Energy Resource are broadly classified into two categories: Nurtured/Cultivated: Biomass from cultivated fields,

crops, forests and harvested periodically, aquatic/marine plants.

Waste Organic Material: Biomass from waste e.g. municipal waste, animal excreta/dung, forest waste, agricultural waste, bioprocess waste, Industrial waste, butchery waste, fishery wastes, processing waste etc.

BIOMASS ENERGY RESOURCE

Category Name of the Biomass Source

Conversion Process

Cultivated Energy Resource

Trees, (Wood chips, saw dusts)

Burning to produce heat and electricity

Aquatic crops, algae, green plants

Producing biogas and biochemicals

Agricultural crops Production of gas (Wood gasification)

Fruit farms Production of wood oil and charcoal (Wood to oil process)

PRINCIPAL BIOMASS ENERGY RESOURCES AND CONVERSION PROCESS

Category Name of the Biomass Source Conversion Process

Waste – Biomass resources from farms and bio-industry

Rice and wheat husk Production of ethyl alcohol by fermentation of molasses, beet root, fruits, potatoes, cereals

Baggase of sugar caneCoconut husk, groundnut shell, straw of rice, wheat etc.Waste of furniture industry, wood industryWaste of poultry industry, fishery industry, food industry, brewery, tannery, butchery etc.Carbohydrates, glucose, fructose etc.

PRINCIPAL BIOMASS ENERGY RESOURCES AND CONVERSION PROCESS (contd…)

Renewable and inexhaustible (theoretically) source of energy

Biomass is very abundant. It is easy to convert to a high energy portable fuel

such as alcohol or gas which are efficient, viable and relatively clean-burning.

It is cheap in contrast to the other energy sources. Biomass production can often mean the restoration

of waste land (e.g. deforested areas) Commercial use of biomass may reduce the problem

of waste disposal

ADVANTAGES OF BIOMASS ENERGY

It may also use areas of unused agricultural land and provide jobs in rural communities.

When direct combustion of plant mass is not used to generate energy (i.e. fermentation, pyrolysis, etc. are used instead), there is minimal environmental impact

If it is produced on a renewable basis using biomass energy, it does not result in a net carbon dioxide increase as plants absorb it when they grow.

Nitrogen-rich bio-digested residue from a biogas plant is a good soil conditioner and improves the fertility of soil

ADVANTAGES OF BIOMASS ENERGY (contd…)

A dispersed and land-intensive source Low energy density 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

DISADVANTAGES OF BIOMASS ENERGY

Scope of biomass energy Rural applications of biomass energy. Urban and industrial applications of biomass energy. Biomass as a primary source for large scale electrical

power generation. India has vast land based, aquatic, forest, agricultural

biomass resources. Biomass energy processes serve many purposes: Energy supply: Fuel, biogas, Organic chemicals Rural development Waste disposal Environment balance

SCOPE OF BIOMASS ENERGY

Growing of selected species of tree and plants on a short rotation basis on waste or arable land for energy generation point of view e.g. Acacia nilotica (Babul, grows even in wasteland) Dalbergia Sissoo (Sheesham, high calorific value up to

4900 kcal/kg) Prosopis Juliflora (Vilayati Babul, Root up to 50m) Albizzia Lebbeck (Siris)

ENERGY PLANTATIONS (TERRESTRIAL)

Growing of floating water plants e.g., water hyacinth in rivers, lakes, ponds etc in tropical / sub-tropical area (yield 25 T(dry)/ha/yr)

ENERGY PLANTATIONS (AQUATIC)

Algae biomass is an important renewable source of energy produced by photosynthesis.

BIOMASS FROM WATER BODIES

The algae is produced in algae farms. Algae contains organic matter which can be converted into methane gas (a useful fuel) in a simple biogas plant by the process called anaerobic digestion. Algae crops are likely to be cultivated on large scale to obtain renewable energy.

After extracting the biogas, the organic residue from the biogas-plant is added to the algae pond. This acts as a food to the bacteria in algae pond. The algae-bacterial combination consumes the waste organic water in the pond, absorbs solar energy and results in rapid growth of algae.

BIOMASS FROM WATER BODIES (contd…)

The biomass can be converted to useful energy forms such as: Heat Gaseous, Liquid and Solid fuels Organic chemical

The biomass conversion process has several routes depending upon temperature, pressure, micro-organisms, and process conditions. These routes are classified in following three broad categories. Direct combustion (Incineration) Thermo-chemical conversion Biochemical conversion

BIOMASS ENERGY CONVERSION PROCESSES

Biomass Resource Conversion Process Products Market

Solid biomass (Wood, Stem)

Combustion Heat Heat/CHP, ElectricityPyrolysis Bio oil, Fuel gas Transportation fuelGasification Fuel gas Transportation fuel

Wet biomass (Organic waste, Manure)

Anerobic digestion

Biogas Electricity

Sugars and starch Plants (Sugarcane, beet, cereals)

Hydrolysis and Fermentation

Bio-ethanol Transportation fuel,Chemical

Oil crops (rapeseed, sunflower)

Extraction and Esterification

Bio-diesel Transportation fuel

BIOMASS ENERGY CONVERSION PROCESSES AND END PRODUCTS

DIRECT COMBUSTION

Direct combustion (rapid oxidation accompanied by heat and light) of biomass is the most straightforward method of energy production.

Generally direct combustion is applicable to solid biomass including cultivated biomass and waste biomass.

The heat released by direct combustion can be used for several useful purposes such as cooking, industrial heat, steam generation etc.

The direct burning of biomass is the cause of a great deal of pollution and has contributed to global warming.

Incineration is the process of burning completely to ashes. The heat generated is either used to generate electricity or to provide heat for industrial purposes and space heating

DISPOSAL OF PADDY STRAW

November 4, 2008Source: Earth Observatory (NASA)

Smoke due to improper combustion (Damage to environment and loss of huge source of energy)

SATELLITE PHOTOGRAPH ON GOOGLE EARTH SNAPSHOT OF NORTHERN INDIA

Only Boiler & ESPneeds to be redesigned

An electrostatic precipitator (ESP) controls particulate emissions

A TYPICAL POWER-PLANT

SILAGE PILING

BIO-MASS STORAGE METHODS

EURO BAGGING

BIO-MASS STORAGE METHODS (contd…)

THERMO-CHEMICAL CONVERSION Biomass is converted into another chemical form by thermo-

chemical processes in which heat is the dominant mechanism. These processes include gasification and pyrolysis and are

separated principally by the availability of oxygen and conversion temperature.

Gasification is the conversion of a solid biomass into a gaseous fuel at a high temperature with controlled air.

Pyrolyisis involves the heating of biomass such as wood or agricultural waste at around 500-900 oC in the absence of oxygen to decompose it into gas and charcoal (carbon). A major advantage of pyrolysis is that carbon dioxide, one of the main drawbacks to most biomass energy conversion processes, is not produced. A disadvantage, however, is that the biomass must be heated to relatively high temperatures, a process that itself requires significant amounts of energy.

The process makes use of the enzymes of bacteria and other micro-organisms to break down biomass to produce liquid and gaseous fuels

In most cases micro-organisms are used to perform the conversion process: anaerobic digestion, fermentation and composting.

Other chemical processes such as converting vegetable or animal oils into biodiesel is transesterification.

BIO-CHEMICAL CONVERSION

Biological treatment can be done either in presence of oxygen (aerobic) or in absence of oxygen (anaerobic).

In India, anaerobic digestion plants are commonly known as Biogas Plants or Gobar Gas Plants. In such plants slurry of cow dung and water is fed to the digester and is allowed to ferment for a few weeks. The biogas is released. The biogas contains about 55% of methane (CH4). This gas is used as a fuel.

There are two types of Biogas PlantsFixed headFloating head

ANAEROBIC DIGESTION

ENERGY ROUTE OF BIOGAS

Sl. No. Constituents % (V/V)

1 CH460

2 CO2 38

3 H2S < 1

4 H2O vapors ~ 1

TYPICAL BIOGAS COMPOSITION

Heating value = 4500 – 4700 k cal/m3

SCHEMATIC OF A FIXED DOME TYPE BIOGAS PLANT

Position a of dome with less gas in the dome. Position b of dome with more gas in the dome.

SCHEMATIC OF A FLOATING DOME TYPE BIOGAS PLANT

COMPARISON OF FIXED AND FLOATING HEAD BIOGAS PLANT

Janta/Fixed dome type Floating Dome type Biogas Plant 1 Gas is released at variable pressure Gas is released at constant pressure 2 Identifying defects is difficult Identifying the defects in gas holder

easy 3 Cost of maintenance is low Cost of maintenance is high 4 Capital cost is low Capital cost is high (for same

capacity) 5 Space above the drum can be used Floating drum does not allow the use

of space for other purpose 6 Temperature is high during winter Temperature is low during winter 7 Life span is comparatively longer Life is short 8 Requires move excavation work Requires relatively less excavation

SIZES OF BIOGAS PLANTS

Category Biogas Delivery

Size of Digester Application

Very small Biogas plant

0.65 m3/day

- For small family of 3 members having 2 cattle.

Small biogas plant

2 m3/day - For family of 6 members having 8 cattle.

Medium (family size) biogas plant

3 m3/day 1.6 m dia, 4.2 m height

For family of 12 persons having 12 heads of cattle.

Large (farm size) biogas plant

6 m3/day 3.3 m dia, 4.65 m height

For a farm having poultry diary etc., 20 cattle.

Very Large (community size)

2600 m3/day

(CO2 free)

1000 m3 Cattle 1000

Advantages Disadvantages

• The slurry is constantly submerged below the dome.• The pressure is naturally

equalised.• No danger of excessive pressure.• No danger of mixing between

biogas and external air. Hence no danger of explosion.• Gas is obtained at uniform and

constant pressure.• Gas does not leak through the

dome as the slurry provides natural screen.

• Higher cost due to fabricated dome construction.• Dome upper surface is exposed

to sunlight and external atmosphere. The heat is lost during winters.• The outlet pipe between the

floating dome and fixed external connection should be of flexible hose type. It is subjected to sun rays, rain and movement. It needs regular attention and maintenance.

ADVANTAGES AND DISADVANTAGES OF FLOATING DOME DESIGN

LARGE BIOGAS PLANT AT VIJAYAVADA MUNICIPAL CORPORATION

TYPICAL GAS PRODUCTION FROM DIFFERENT FEEDSTOCK

Sl. No. Feedstock Typical Gas Yield

(liters/kg)Typical Methane Content

(%)1. Paper Waste 480 532. Bagass 330 573. Spent Tea Waste 235 574. Food Waste 160 625. Bamboo Pulp 145 546. Dry Leaves 118 607. Green leaves & twigs 100 658. Fruit waste 91 509. Bamboo dust 53 7210. Distillery effluent 31 7511. Black liquor (Paper Mill) 22 6912. Animal Excreta

- Cow/Bullock- Buffalo- Pig- Chicken

36367862

60-65%“““

13. Human Excreta 70 “

SALIENT FEATURES OF FOOD WASTE BIOGAS PLANTS (BIOMETHANATION)

Quantity (MT/Day)

Eqv. LPG (Kg/Month)

Eqv. Electricity (Units/Day)

Bio manure (MT/Annum)

Area (sq.ft)

1 890 – 940 105 30 3000

2 1750 – 1850 210 60 3500

3 2600 – 2800 315 100 4300

4 3500 – 3700 420 130 5000

5 4400 - 4700 525 160 5300

FERMENTATION Process of production of ethyl alcohol from any

feedstock containing sugar or starch or also from cellulose materials.

Feedstock: Sugar: Sugar beets, sugar cane, sweet sorghum,

Fruits etc Starches: Grains like corn, wheat, potatoes etc. Cellulose: Wood, solid waste, agricultural wastes etc.

Process of production: Fermentation of fermentable sugar solutionFermentation of sugar solution to Ethyl alcohol Separation of ethanol from other by – products.

Feedstock

Milling

Sterilization

Cooking

Cooling

Fermentation

Bear

Distillation

Dehydration

DenaturationFuel alcohol

(enzymes & water added to form mess)

(yeasts addition)(2 days)

(10% ethyl alcohol)

PROCESS OF PRODUCTION OF FUEL ALCOHOL

ENERGY ROUTES OF URBAN WASTE TO ENERGY

PYROLYSIS OF URBAN WASTE