overview of technologies for converting waste agricultural biomass into energy
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Overview of Technologies for Converting
Waste Agricultural Biomass into Energy
Training onTechnologies for Converting Waste Agricultural Biomass into Energy
Organized by
United Nations Environment Programme (UNEP DTIE IETC)
23-25 September, 2013San Jose, Costa Rica
Surya Prakash ChandakSenior Programme Officer
International environmental Technology CentreDivision of Technology, Industry and Economics
Osaka, Japan
CONTENT
Technology Classification
Direct Combustion
Densification
Thermo-chemical Conversion
Biological Conversion
Liquid Biofuels
Environmental Characteristics
Technology Selection
Technologies in Practice 2
TECHNOLOGY CLASSIFICATION Direct combustion of raw biomass is the simplest
method of extracting energy with lowest cost
– Therefore is the most common method of conversion.
– However, such a use faces the worst features of biomass - bulk and inconvenience.
Therefore, before bio-energy is used for end-use activities, it may have to be converted from its primary form into a form that is more convenient for transport and use.
– This may involve simple physical processing before combustion or upgrading to a variety of convenient secondary fuels (solid, liquid or gas) by means of certain conversion processes. 3
TECHNOLOGY CLASSIFICATION Methods of utilizing waste agricultural biomass
as a source of energy
WAB Resources
Conversion Processes
Intermediate Fuels
Biomass Fuels
Heat
Electricity
Mechanical Power
Direct Combustion / Gasification
HeatEngines
Generator
4RESOURCE TECHNOLOGY APPLICATION
TECHNOLOGY CLASSIFICATION Different processes and technologies are
available for converting biomass to energy.
Could be categorized as:– Direct combustion of the raw biomass– Combustion after simple physical processing,
sorting, chipping, compressing, air-drying (beneficiation)
– Thermo-chemical processing Processes in this category include pyrolysis, gasification or
liquefaction;
– Biological processing Natural processes such as anaerobic digestion and
fermentation encouraged by the provision of suitable conditions giving useful secondary fuel (gaseous or liquid);
– Extraction Trans-esterification to produce biodiesel. 5
TECHNOLOGY CLASSIFICATION
6
Figure 1.10: Methods of using biomass for energy
Combustion Gasification
Pyrolysis; Liquefaction; Hydrothermal
Upgrading
Digestion Fermentation Extraction Oilseeds
Steam Turbine
Gas turbine, combined cycle,
engine
Methanol,
hydrocarbons,
hydrogen
synthesis
Steam Gas Oil Gas Charcoal Biogas
Fuel Cell
Upgrading
Diesel
Gas Engine
Distillation
Ethanol
Esterification
Bio Diesel
Heat Electricity Fuel
Thermo-chemical Conversion Biochemical Conversion
Raw Material/Beneficiated Products Methods of using WAB for Energy
TECHNOLOGY CLASSIFICATION Thermo-chemical conversion routes
7
ICE : Internal Combustion EngineECE : External Combustion EngineLGLF: Low-Grade Liquid FuelHGLF: High-Grade Liquid FuelLMJG: Low-Megajoule GasMMJG: Medium-Megajoule Gas
BI
OM
AS
S
Beneficiation
Upgrading / Conversion
Liquifaction
Gasification
Pyrolysis
Improvedsolidfuels
Char
LGLF
LMJG
HGLF
MMJG
Combustion Heat
Use in ICE Power
Use in ECE
TECHNOLOGY CLASSIFICATION
8
Methods of using WAB for Energy
BENEFICIATION
Drying Dewatering Sizing Densification Separation Torrefaction
Baling Pelletization Briquetting
DIRECT COMBUSTION Combustion of biomass has been widely used in
the past to generate heat– At present, it is making a comeback in many industrial
applications including generation of electricity,
Straightforward conversion of thermal energy into mechanical or electric power results in considerable losses– It is not possible to raise the ratio of thermal to
mechanical power above 60%. – However, if the low temperature waste heat can be
used productively, for instance for drying or heating purposes, much higher overall efficiencies can be obtained.
9
DIRECT COMBUSTION Fuels and Combustion
Biomass combustion
10
Combustion Unit
Air and Fuel Combustion
Products
Heat Energy
Light
Volatile Matter
Hot Flue Gas
Flame Front
Entrained Air
Burning CharAsh
Wood
Conduction to Wood
Radiation to Wood
Radiation to
Surrounding
Convective Heat to Surrounding
EnergyCombustion of ProductsOxidizerFuel
DIRECT COMBUSTION Biomass combustion
- Processes and temperatures in a burning piece of wood
11
Gaseous-phase combustion Diffusion flame, mostly Turbulent – a ‘free’ fire T > 1000C (probably T < 1000C) Simultaneous heat and mass transfer with chemical reaction; Surface combustion – a slow process 500C < T < 800C Problem same as in zone A but with sources/sinks due to pyrolytic reactions 200C < T < 500C Heat conduction in a medium with a moving boundary; Mitigation of moisture & gases; Uncertain properties T < 200C
Figure 6.1: Processes and temperatures in a burning piece of wood
Flame
D
Char
C
Pyrolytic Zone
B
Virgin Wood
A
Hea
t Flo
w
Gas
Flo
w
Properties of Fuels– Solid.
DensityMoisture ContentVolatile Matter and Fixed CarbonSulfur ContentAsh Calorific Value
DIRECT COMBUSTION
12
Fuel Volatile Matter Fixed Carbon Ash
Paddy Husk 63.3 14.0 22.7
Bagasse 74.0 19.3 6.7
Wood 77 - 87 13 - 21 0.1 - 2.0
Lignite 43.0 46.6 10.4
Anthracite Coal 5.0 80 15
DENSIFICATION Densification (briquetting or pelleting) is used to
improve characteristics of materials (especially low density biomass)– Productive transport,– Improved fuel characteristics.
Raw materials used include sawdust, loose crop residues, and charcoal fines.
The material is compacted under pressure– Depending on the material, the pressure, and the
speed of densification, additional binders may be needed to bind the material
13
DENSIFICATION There are two main briquetting technologies
– Piston press– Screw press.
In the piston press the material is punched into a die by a ram with a high pressure.
In the screw press, the material is compacted continuously by a screw.
With the screw press generally briquettes of higher quality can be produced.
14
THERMOCHEMICAL CONVERSION In thermochemical conversion, biomass is
subjected to appropriate temperatures and pressures and normally a restricted supply of oxygen
Pyrolysis is the basic thermochemical process to convert biomass into more valuable or more convenient products– In fact, it is the oldest method of processing one fuel
in order produce better one
Conventional pyrolysis involves heating the original material in the near-absence of air, typically at 300 - 500C, until the volatile matters has been driven off. 15
THERMOCHEMICAL CONVERSION The residue is then the char (more commonly
known as charcoal)– Char has about twice the energy density of the
original fuel and burns at a much higher temperature
For many centuries, and in much of the world still today, charcoal is produced by pyrolysis of wood. – Depending on the moisture content and the efficiency
of process, 4 - 10 kg of wood are required to produce one kg of charcoal
16
THERMOCHEMICAL CONVERSION With more sophisticated pyrolysis techniques,
the volatile matters can be collected– Careful choice of the temperature at which the
process takes place allows the control of the composition.
– The products formed are normally a gas, an oil-like liquid and charcoal
– The distribution of these products is dependent on the feedstock, temperature and pressure of reaction, the time spent in the reaction zone and the heating rate.
– High temperature pyrolysis (1000C) maximizes the production of gas (gasification) while lower temperature pyrolysis processes (<600C) have been used for the production of charcoal (carbonization).
– Another approach to produce liquid fuels and chemicals from biomass is direct catalytic liquefaction
17
BIOLOGICAL CONVERSION Biological conversion consists of exposing
biomass to certain microorganisms.
The secondary fuels produced are the result of metabolic activity of the microorganisms.
Production of Ethanol and biogas are the two most common biological conversion processes.
Ethanol fermentation from carbohydrates is probably one of the oldest processes known to man. – Today, it is widely regarded as an important potential
alternative source of liquid fuels for the transport sector. 18
LIQUID BIOFUELS Definition
- The term biofuels generally refers to liquid fuels made from biological sources, which include pure plant oil (PPO), bioethanol and biodiesel.
- Global biofuel production from year 2000 to 2011
19
0
10
20
30
40
50
60
70
80
90
100
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Bio
fuel P
rod
ucti
on
(M
illio
n L
iters
)
Year
Ethanol
Biodiesel
LIQUID BIOFUELS Production and uses of liquid biofuels
20
First Generation (Conventional) BiofuelsBiofuel Type
Specific Names Biomass Feedstock Production Process
Uses
Vegetable/Plant Oil
Straight VegetableOil (SVO);Pure Plant Oil (PPO)
Oil crops(e.g. Rapeseed, Corn, Sunflower,Soybean,Jatropha,Jojoba,Coconut,Cotton,Palm,etc.)Algae
Cold pressing/extraction
Diesel engines,Generators,Pumping (all after modifications);Use for cooking and lighting, as possible;Transportation
Biodiesel
Biodiesel fromenergy crops
Cold pressing/extraction &trans-esterification
Diesel engines for power generation,Mechanicalapplications,Pumping;Transportation(diesel engines)
Rapeseed methylester (RME), fattyacid methyl/ethylester (FAME/FAEE)Biodiesel from waste; FAME/FAEE
Waste/cooking/frying oil/animal fat
Trans-esterification
BioethanolConventionalbioethanol
Sugarcane, Sweet sorghum, Sugar beet, Cassava Grains
Hydrolysis &fermentation Internal combustion
engine for motorized transport
Bio-ETBEEthyl Tertiary; Butyl; Ether
Bioethanol Chemical synthesis
LIQUID BIOFUELS Production and uses of liquid biofuels
21
Second Generation BiofuelsBiofuel Type
Specific Names Biomass Feedstock
Production Process
Uses
BiodieselHydro-treatedbiodiesel
Vegetable oils and animal fat
Hydro-treatment
Internal combustionengine for motorized transport
BioethanolCellulosic bioethanol
Lignocellulosic material
Advanced hydrolysis& fermentation
Synthetic biofuels
Biomass-to-liquids(BTL):Fischer-Tropsch (FT) diesel; BiomethanolBiodimethyl-ether(Bio-DME)
Lignocellulosicmaterial
Gasification &synthesis
Bio-hydrogen
Lignocellulosicmaterial
Gasification &synthesis or biol.
LIQUID BIOFUELS Production and uses of liquid biofuels
22
Parameters 1st Gen. 2nd Gen.
Direct food vs. fuel competition Yes No
Feedstock cost per unit of production High Low
Land-use efficiency Low High
Feasibility of using marginal lands for feedstock production Poor Good
Ability to optimize feedstock choice for local conditions Limited High
Potential for net reduction in fossil fuel use Medium Medium-High
Potential for net reduction in greenhouse gas emissions Medium Medium-High
Readiness for use in existing petroleum infrastructure Yes Yes
Proven commercial technology available today Yes No
Simplicity of processes Yes No
Capital costs per unit of production Low High
Total cost of production High High
Minimum scale for economical production Medium High
LIQUID BIOFUELS First, second and third generation biofuels
23
Biofuels
Ethanol Biodiesel
1st Generation 2nd Generation 1st Generation 2nd Generation 3rd Generation
Corn Cane Maize
Switchgrass Cellulosic Gasification
Palm Soybeans Rapeseed
Jatropha Gasification
Algae
ENVIRONMENTAL PERFORMANCES Impacts of emissions from biomass combustion
24
Component Biomass Sources Climate, environmental and health impactCarbon dioxide (CO2) Major combustion product
from all biomass fuelsClimate: Direct GHG. However, biomassis a CO2-neutral fuel
Carbon monoxide (CO)
Incomplete combustion of all biomass fuels
Climate: Indirect GHG through ozone formation. Health: Reduced oxygen uptake especially influences people with asthma, and embryos. Suffocation in extreme cases.
Methane (CH4) Incomplete combustion of all biomass fuels
Climate: Direct GHG. Indirect GHG through ozone formation.
Non Methane VolatileOrganic Components(NMVOC)
Incomplete combustion of all biomass fuels
Climate: Indirect GHG through ozone formation. Health: Negative effect on human respiratory system
Polycyclic AromaticHydrocarbons (PAH)
Incomplete combustion of all biomass fuels
Environment: Smog formationHealth: Carcinogenic effects
Particles Soot, char and condensed heavy hydrocarbons (tar) from incomplete combustion of all biomass fuels. Fly ash and salts
Climate and environment: Reversed greenhouse effect through aerosol formation. Indirect effects of heavy-metal concentrations in deposited particles.Health: Negative effect on the human respiratory system. Carcinogenic effects
ENVIRONMENTAL PERFORMANCES Impacts of emissions from biomass combustion
25
Component Biomass Sources Climate, environmental and health impactNitric oxides(NOX = NO and NO2)
Minor combustion product from all biomass fuels containing nitrogen. Additional NOx may beformed from nitrogen in the air under certain conditions
Climate and environment: Indirect greenhouse effect through ozone formation. Reversed greenhouse effect through aerosol formation. Acid precipitation. Vegetation damage. Smog formation. Corrosion and material damage. Health: Negative effect on the human respiratory system. NO2 is toxic
Nitrous oxide (N2O)
Minor combustion product from all biomass fuels containing nitrogen
Climate: Direct GHG. Health: Indirect effect through ozone depletion in the stratosphere
Ammonia (NH3)
Small amounts may be emitted as a result of incomplete conversion of NH3 from pyrolysis/ gasification
Environment: Acid precipitation. Vegetation damage. Corrosion and material damage. Health: Negative effect on the human respiratory system.
Sulphur oxides(SOX = SO2 and SO3)
Minor combustion product from all biomass fuels containing sulphur.
Climate and environment: Reversed greenhouse effect through aerosol formation. Acid precipitation. Vegetation damage. Smog formation. Corrosion and material damage. Health: Negative effect on the human respiratory system, asthmatic effect
ENVIRONMENTAL PERFORMANCES Impacts of emissions from biomass combustion
26
Component Biomass sources Climate, environmental and health impactHeavy metals All biomass fuels contain
heavy metals to some degree, which will remain in the ash or evaporate
Health: Accumulate in the food chain. Some are toxic and some have carcinogenic effects
Ground levelozone (O3)
Secondary combustion product from atmospheric reactions, including CO, CH4, NMVOC and NOX
Climate and environment: Direct GHG.Vegetation damage. Smog formation.Material damage. Health: Indirect effect through ozone depletion in the stratosphere. Negative effect on the human respiratory system, asthmaticeffect
Hydrogen Chloride (HCl)
Minor combustion product from all biomass fuels containing chlorine
Environment: Acid precipitation. Vegetation damage. Corrosion and material damage. Health: Negative effect on the human respiratory system. Toxic
Dioxins and FuransPCDD/PCDF
Small amounts may be emitted as a result of reactions including carbon, chlorine, and oxygen in the presence of catalysts (Cu)
Health: Highly toxic. Liver damage. Central nervous system damage. Reduced immunity defense. Accumulate in the food chain
ENVIRONMENTAL PERFORMANCES Carbon emissions
27
Technology CO2 Emissions (Tonnes per GWh)Fuel
ExtractionConstruction Operation Total
Coal-fired 1 1 962 964AFBC* 1 1 961 963 IGCC** 1 1 748 751Oil-fired - - 726 726Gas-fired - - 484 484Geothermal <1 1 56 57Small hydro N/A 10 N/A 10Nuclear ~2 1 5 8Wind N/A 7 N/A 7Photovoltaic N/A 5 N/A 5Large hydro N/A 4 N/A 4Solar thermal N/A 3 N/A 3Wood -1509 3 1346 -160
TECHNOLOGY SELECTION Analysis of the Options
SAT Methodology
Level of use
28
RESOURCE
TECHNOLOGY
APPLICATION
Research Pilot Demonstration Commercial
GasificationPyrolysis
Biofuel applicationsBio-chemicals
Household energyBriquetting
Carbonization Combustion
Anaerobic Digestion
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