Bioenergy overview Biomass resources Bioenergy technologies Concluding remarks

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Title

Biomass

Mário Costa

Departamento de Engenharia Mecânica

Instituto Superior Técnico

Avenida Rovisco Pais, 1049

Avenida Rovisco Pais, 1049--001 Lisboa, Portugal

001 Lisboa, Portugal

Mário Costa

RENEWABLE ENERGY RESOURCES,

RENEWABLE ENERGY RESOURCES, InstitutoInstituto Superior Superior TécnicoTécnico, , 22 March 2010

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Bioenergy overview

Biomass resources

Bioenergy technologies

Synopsis

Bioenergy technologies

Concluding remarks

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Global energy sources

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Renewable energy use

2001

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Bioenergy

Bioenergy cycle/carbon cycle

cycle/carbon cycle

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Commercial carbon cycle

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Biomass resources

Energy crops

–

– Woody crops

Woody crops

–

– Agricultural crops

Agricultural crops

Waste products

–

– Wood residues

Wood residues

–

– Temperate crop wastes

Temperate crop wastes

–

– Tropical crop wastes

Tropical crop wastes

–

– Animal wastes

Animal wastes

–

– Municipal solid waste

Municipal solid waste

–

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Corn

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Soybeans

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Sugar cane

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Switchgrass

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Municipal solid waste

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Heat energy content

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Bioenergy

Bioenergy technologies

technologies

Thermochemical conversion

Direct combustion

(direct combustion of solid matter)

Gasification

(exposing a solid fuel to high temperatures and limited oxygen produces biogas)

Pyrolysis liquefaction

(heating the biomass can produce pyrolysis oil and leaving charcoal)

Biochemical conversion

Anaerobic digestion

(bacteria, in an oxygen-starved environment can produce methane)

Fermentation

(biomaterial that is used to manufacture ethanol and biodiesel by an anaerobic biological process in which sugars are converted to alcohol by the action of microorganisms)

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Bioenergy

Bioenergy technologies

technologies

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Bioenergy

Bioenergy technologies

technologies

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Bioenergy

Bioenergy technologies

technologies

Direct combustion

Direct combustion of solid matter where the biomass is fed into a furnace where it is burned. The heat is used to boil water and the energy in the steam is used to turn turbines and generators

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Biomass direct combustion

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Current status of biomass

combustion

There are a lot of combustible biomass available

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Current status of biomass

combustion

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Current status of biomass

combustion

Biomass combustion (modern plus traditional combustion)

represents around 15% of world energy consumption…

… and some up to 90% in some developing countries!

About 2.5 billion people worldwide depend on biomass combustion

through the use of relatively simple combustion devices

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Combustion technologies

Grate furnace Bubbling fluidized bed furnace

Circulating fluidized bed furnace

Pulverized fuel furnace

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Grate furnace

Combustion technologies

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Bubbling fluidized bed furnace

Tertiary

air

Fuel

feeding

Superheaters

Water tubes

Combustion technologies

Primary

air

Secondary

air

Bottom ash

removal

feeding

Start up

burners

Refractory

Sand

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Circulating fluidized bed furnace

Dilute suspension

Water tubes

Combustion technologies

Return

leg

Dense

suspension

Circulation

Secondary

air

Primary

air

Cyclone

Fuel

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Pulverized fuel furnace

Combustion technologies

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Comparison

between

some

characteristics

of

the

combustion processes in grate, fluidized bed and

pulverized fuel furnaces

Characteristic

Combustion technology

Pulverized Grate Fluidized bed

Combustion technologies

Combustion efficiency (%) 99 70-90 90-99

Global thermal efficiency (%) 35-45 25-35 40-55

Excess air (%) 15-50 20-40 10-25

Particle size (mm) < 0.5 12-20 8

Operating temperature (ºC) 1400-1700 1400-1700 800-1000

NO_x emissions High High Low

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Co

Co--firing

firing

The use of biomass co-firing

Direct co-firing in coal fired power plants is used by power stations in EU and USA

Demonstrated successfully in more than 130 installations worldwide, for most combinations of fuel and boiler type

Most use about 10% of biomass (energy basis) but can readily burn up to 25% thermal

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Co

Co--firing

firing

The use of biomass co-firing

Indirect co-firing with pre-gasification or other thermal pretreatment

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Co

Co--firing

firing

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Direct co-firing

: Fiddlers’ Ferry Power Station (UK)

uses 20% of

biomass

Co

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Indirect co-firing

: Lahti, Finland

Co

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Co

Co--firing

firing

Advantages of co-firing

Co-firing can be undertaken with existing power plants, and thus has high power generation efficiency

Short term implementation on large scale; if well-managed, technical risks are low

It is attractive in terms of the capital investment requirement and generation cost.

It can increase the amount of renewable energy and thereby reduce the CO₂ emissions

Almost any biomass material can be used (e.g., wood, olive and palm oil waste, cereal and straw. Thus it is attractive in terms of security of supply Usually, biomass fuels present low levels of sulphur, nitrogen and toxic

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Co

Co--firing

firing

Disadvantages of co-firing

Biomass is a poor fuel: it contains O2 and a substantial amount of moisture

Contains potassium: it can cause corrosion

Biomass can be expensive: it depends on subsidies at present May not be sustainable

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MSW power plant

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Composition of MSW

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Integrated waste plant

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Landfill gases

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Bioenergy

Bioenergy technologies

technologies

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Bioenergy

Bioenergy technologies

technologies

Gasification

Biomass heated with no oxygen

Gasifies to mixture of CO and H

2

(called “syngas” for

synthetic gas)

Mixes easily with oxygen

Burned in turbines to generate electricity (like natural gas)

Can easily be converted to other fuels, chemicals, and

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200 tons of wood chips daily

Forest thinnings; wood pellets

Converted to gas at ~1000 ºC

Biomass

Biomass gasifier

gasifier

Converted to gas at ~1000 ºC

Combined cycle gas turbine

8 MW power output

McNeil Generating Station biomass gasifier – 8MW

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Bioenergy

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Bioenergy

Bioenergy technologies

technologies

Pyrolysis liquefaction

Heat is used to chemically convert biomass to bio-oil

Pyrolysis oil is easier to store and transport than solid biomass material and can be burned like petroleum to generate electricity Phenol oil a chemical used to make wood adhesives, molded Phenol oil a chemical used to make wood adhesives, molded

plastics and foam insulation. Wood adhesives are used to glue together plywood and other composite wood products

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Pyrolysis

Heat bio-material under pressure

500-1300 ºC

50-150 atmospheres

Carefully controlled air supply

Up to 75% of biomass converted to liquid

Tested for use in engines, turbines, boilers

Currently experimental

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Pyrolysis

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Bioenergy

Bioenergy technologies

technologies

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Bioenergy

Bioenergy technologies

technologies

Anaerobic digestion

Decomposition of organic matter by anaerobic bacteria in an oxygen-starved environment

Anaerobic digesters compost (or "digest") organic waste in a

machine that limits access to oxygen encouraging the generation of methane and carbon dioxide by microbes in the waste. This

methane and carbon dioxide by microbes in the waste. This digester gas is then burned as fuel to make electricity

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Anaerobic digestion

Decompose biomass with microorganisms in closed tanks

known as anaerobic digesters

Typical composition of biogas

Methane CH₄ 50-75

Methane-rich biogas can be used as fuel or as a base

chemical for bio based products

Methane CH₄ 50-75 Carbon dioxide CO₂ 25-50 Nitrogen N₂ 0-10 Hydrogen H₂ 0-1 Hydrogen sulfide H₂S 0-3 Oxygen O₂ 0-2

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Anaerobic digestion

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Anaerobic digestion

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Bioenergy

Bioenergy technologies

technologies

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Bioenergy

Bioenergy technologies

technologies

Fermentation

Unlike other renewable energy sources, biomass can be converted directly into liquid fuels (biofuels) for our transportation needs

(cars, trucks, buses, airplanes, and trains)

The two most common types of biofuels are ethanol and biodiesel Ethanol is an alcohol, created by fermenting biomass high in

carbohydrates. It is used as a fuel additive to cut down carbon monoxide and other emissions

Biodiesel is made by combining alcohol with vegetable oil, animal fat or other recycled cooking grease and is also an additive to

reduce emissions. When pure, biodiesel is a renewable alternative fuel for diesel engines

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Biodiesel Bus

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Ethanol yields

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Ethanol production plant

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Ethanol production

Corn kernels are ground in a hammer mill to expose the starch

The ground grain is mixed with water, cooked briefly and

enzymes are added to convert the starch to sugar using a

chemical reaction called hydrolysis

Yeast is added to ferment the sugars to ethanol

The ethanol is separated from the mixture by distillation and

the water is removed from the mixture using dehydration

Energy content about 2/3 of gasoline

Takes energy to create ethanol from starchy sugars

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Economic issues

• Sustainable Development

Move toward sustainable energy production

• Energy Security

Reduce dependence on imported oil

• Rural Economic Growth

Provide new crops/markets for rural

business

• Land Use

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Economic issues

• Sustainable Development

Move toward sustainable energy production

• Energy Security

Reduce dependence on imported oil

• Rural Economic Growth

Provide new crops/markets for rural

business

• Land Use

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Environmental issues

• Air Quality

Reduce NO

_x

and SO

₂

emissions

• Global Climate Change

Low/no net increase in CO

₂

• Soil Conservation

Soil erosion control, nutrient retention,

carbon sequestration, and stabilization of

riverbanks.

• Water Conservation

Better retention of water in watersheds

• Biodiversity and Habitat

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Heat and CO

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Bioenergy

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