Training on Technologies for Converting Waste Agricultural Biomass
Training on Technologies for Converting Waste Agricultural Biomass into Energy Organized by United Nations Environment Programme (UNEP DTIE IETC) 23 -25 September, 2013 San Jose, Costa Rica Overview of Technologies for Converting Waste Agricultural Biomass into Energy Surya Prakash Chandak Senior Programme Officer International environmental Technology Centre Division 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 Heat Direct Combustion / Gasification Biomass Fuels Generator Electricity Heat Engines Intermediate Fuels RESOURCE Mechanical Power TECHNOLOGY APPLICATION 4
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, ü sorting, chipping, compressing, air-drying (beneficiation) – Thermo-chemical processing ü Processes in this category include pyrolysis, gasification or liquefaction; – Biological processing ü Natural processes such as anaerobic digestion and fermentation encouraged by the provision of suitable conditions giving useful secondary fuel (gaseous or liquid); – Extraction ü Trans-esterification to produce biodiesel. 5
TECHNOLOGY CLASSIFICATION Methods of using WAB for Energy 6
TECHNOLOGY CLASSIFICATION § Thermo-chemical conversion routes 7
TECHNOLOGY CLASSIFICATION Methods of using WAB for Energy BENEFICIATION Drying Dewatering Sizing Densification Separation Baling Pelletization Briquetting Torrefaction 8
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 Air and Fuel Heat Energy Combustion Unit Combustion Products Light § Biomass combustion Convective Heat to Surrounding Hot Flue Gas Flame Front Radiation to Surroundin g Wood Volatile Matter Radiation to Wood Entrained Air Conduction to Wood Burning Char Ash 10
DIRECT COMBUSTION § Biomass combustion - Processes and temperatures in a burning piece of wood 11
DIRECT COMBUSTION § Properties of Fuels – Solid. ü Density ü Moisture Content ü Volatile Matter and Fixed Carbon ü Sulfur Content ü Ash ü Calorific Value 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 12
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 - 500 C, until the volatile matters 15 has been driven off.
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 (1000 C) maximizes the production of gas (gasification) while lower temperature pyrolysis processes (<600 C) 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
LIQUID BIOFUELS § Production and uses of liquid biofuels First Generation (Conventional) Biofuels Biofuel Specific Names Biomass Feedstock Production Type Process Straight Vegetable Oil crops Cold pressing/ Oil (SVO); (e. g. Rapeseed, Corn, extraction Pure Plant Oil (PPO) Sunflower, Vegetable/ Soybean, Plant Oil Jatropha, Jojoba, Coconut, Biodiesel from Cold pressing/ Cotton, energy crops extraction & Palm, Rapeseed methyl transetc. ) esterification ester (RME), fatty Algae Biodiesel acid methyl/ethyl ester (FAME/FAEE) Biodiesel from waste; Waste/cooking/ Trans. FAME/FAEE frying oil/animal fat esterification Conventional Sugarcane, Sweet Hydrolysis & Bioethanol bioethanol sorghum, Sugar beet, fermentation Cassava Grains Ethyl Tertiary; Butyl; Bioethanol Chemical Bio-ETBE Ether synthesis Uses Diesel engines, Generators, Pumping (all after modifications); Use for cooking and lighting, as possible; Transportation Diesel engines for power generation, Mechanical applications, Pumping; Transportation (diesel engines) Internal combustion engine for motorized transport 20
LIQUID BIOFUELS § Production and uses of liquid biofuels Second Generation Biofuels Biofuel Specific Names Biomass Production Type Feedstock Process Hydro-treated Vegetable oils Hydro-treatment Biodiesel biodiesel and animal fat Cellulosic Lignocellulosic Advanced material hydrolysis Bioethanol bioethanol & fermentation Biomass-to-liquids Lignocellulosic Gasification & (BTL): material synthesis Fischer-Tropsch Synthetic (FT) diesel; biofuels Biomethanol Biodimethyl-ether (Bio-DME) Biohydrogen Lignocellulosic material Uses Internal combustion engine for motorized transport Gasification & synthesis or biol. 21
LIQUID BIOFUELS § Production and uses of liquid biofuels Parameters 1 st Gen. 2 nd 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-High Potential for net reduction in greenhouse gas emissions Medium-High Readiness for use in existing petroleum infrastructure 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 Medium High Minimum scale for economical production 22
LIQUID BIOFUELS § First, second and third generation biofuels 23
ENVIRONMENTAL PERFORMANCES § Impacts of emissions from biomass combustion Component Biomass Sources Carbon dioxide (CO 2) Major combustion product from all biomass fuels Carbon monoxide Incomplete combustion of (CO) all biomass fuels Methane (CH 4) Incomplete combustion of all biomass fuels Non Methane Volatile Incomplete combustion of Organic Components all biomass fuels (NMVOC) Polycyclic Aromatic Incomplete combustion of Hydrocarbons (PAH) all biomass fuels Particles Soot, char and condensed heavy hydrocarbons (tar) from incomplete combustion of all biomass fuels. Fly ash and salts Climate, environmental and health impact Climate: Direct GHG. However, biomass is a CO 2 -neutral fuel Climate: Indirect GHG through ozone formation. Health: Reduced oxygen uptake especially influences people with asthma, and embryos. Suffocation in extreme cases. Climate: Direct GHG. Indirect GHG through ozone formation. Climate: Indirect GHG through ozone formation. Health: Negative effect on human respiratory system Environment: Smog formation Health: Carcinogenic effects 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 24 system. Carcinogenic effects
ENVIRONMENTAL PERFORMANCES § Impacts of emissions from biomass combustion Component Nitric oxides (NOX = NO and NO 2) Biomass Sources Minor combustion product from all biomass fuels containing nitrogen. Additional NOx may be formed from nitrogen in the air under certain conditions Climate, environmental and health impact 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. NO 2 is toxic Nitrous oxide Minor combustion product Climate: Direct GHG. (N 2 O) from all biomass fuels Health: Indirect effect through ozone depletion containing nitrogen in the stratosphere Ammonia Small amounts may be emitted Environment: Acid precipitation. Vegetation (NH 3) as a result of incomplete damage. Corrosion and material damage. conversion of NH 3 from Health: Negative effect on the human respiratory pyrolysis/ gasification system. Sulphur Minor combustion product Climate and environment: Reversed greenhouse oxides from all biomass fuels effect through aerosol formation. Acid (SOX = SO 2 containing sulphur. precipitation. Vegetation damage. Smog and SO 3) formation. Corrosion and material damage. Health: Negative effect on the human respiratory 25 system, asthmatic effect
ENVIRONMENTAL PERFORMANCES § Impacts of emissions from biomass combustion Component Heavy metals Ground level ozone (O 3) Biomass sources All biomass fuels contain heavy metals to some degree, which will remain in the ash or evaporate Secondary combustion product from atmospheric reactions, including CO, CH 4, NMVOC and NOX Hydrogen Chloride (HCl) Minor combustion product from all biomass fuels containing chlorine Dioxins and Furans PCDD/PCDF Small amounts may be emitted as a result of reactions including carbon, chlorine, and oxygen in the presence of catalysts (Cu) Climate, environmental and health impact Health: Accumulate in the food chain. Some are toxic and some have carcinogenic effects 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, asthmatic effect Environment: Acid precipitation. Vegetation damage. Corrosion and material damage. Health: Negative effect on the human respiratory system. Toxic Health: Highly toxic. Liver damage. Central nervous system damage. Reduced immunity defense. Accumulate in the food chain 26
ENVIRONMENTAL PERFORMANCES § Carbon emissions Technology Coal-fired AFBC* IGCC** Oil-fired Gas-fired Geothermal Small hydro Nuclear Wind Photovoltaic Large hydro Solar thermal Wood Fuel Extraction 1 1 1 <1 N/A ~2 N/A N/A -1509 CO 2 Emissions (Tonnes per GWh) Construction Operation Total 1 1 10 1 7 5 4 3 3 962 961 748 726 484 56 N/A 5 N/A N/A 1346 964 963 751 726 484 57 10 8 7 5 4 3 -160 27
TECHNOLOGY SELECTION § Analysis of the Options TECHNOLOGY ü SAT Methodology RESOURCE APPLICATION § Level of use Household energy Briquetting Carbonization Combustion Anaerobic Digestion Gasification Pyrolysis Biofuel applications Bio-chemicals Research Pilot Demonstration Commercial 28
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