Q.1 What is the primary component of lignocellulosic biomass that provides structural strength?
Cellulose
Hemoglobin
Starch
Lipids
Explanation - Cellulose is a polysaccharide that forms the rigid framework of plant cell walls, making up the bulk of lignocellulosic biomass.
Correct answer is: Cellulose
Q.2 Which of the following is NOT a typical product of biomass gasification?
Syngas
Char
Bio-oil
Hydrogen
Explanation - Bio‑oil is produced by pyrolysis, not gasification. Gasification yields syngas, char, and hydrogen as primary products.
Correct answer is: Bio-oil
Q.3 In a direct combustion biomass power plant, what is the main purpose of the steam turbine?
To dry the biomass feedstock
To convert thermal energy to mechanical work
To separate ash from flue gases
To compress the intake air
Explanation - The steam turbine converts high‑pressure steam, produced by burning biomass, into mechanical rotation that drives a generator.
Correct answer is: To convert thermal energy to mechanical work
Q.4 Which conversion pathway yields the highest energy efficiency for woody biomass?
Direct combustion
Anaerobic digestion
Fermentation to ethanol
Gasification
Explanation - Gasification can achieve efficiencies of 30‑40 % by converting solid biomass to a high‑grade syngas, which is then used in combined‑cycle turbines.
Correct answer is: Gasification
Q.5 What is the typical moisture content limit for solid biomass fed into a conventional boiler?
5 %
10 %
20 %
50 %
Explanation - Most boilers require biomass moisture below about 20 % (wet basis) to maintain stable combustion and avoid excess slagging.
Correct answer is: 20 %
Q.6 Which of the following enzymes is key in the hydrolysis of cellulose to glucose?
Amylase
Protease
Cellulase
Lipase
Explanation - Cellulase catalyzes the breakdown of cellulose polymer chains into soluble glucose monomers.
Correct answer is: Cellulase
Q.7 In a biogas plant, the main gaseous component produced is:
Carbon dioxide
Methane
Oxygen
Nitrogen
Explanation - Anaerobic digestion of organic matter generates biogas composed of roughly 55‑70 % methane, the combustible component.
Correct answer is: Methane
Q.8 What is the primary advantage of using a fluidized‑bed combustor for biomass?
Lower capital cost
Higher combustion temperature with uniform heat distribution
Elimination of ash handling
No need for fuel drying
Explanation - Fluidized beds provide intense mixing, enabling uniform temperature, better fuel flexibility, and lower emissions.
Correct answer is: Higher combustion temperature with uniform heat distribution
Q.9 Which of the following feedstocks has the highest heating value on a dry basis?
Wood chips
Sugarcane bagasse
Rice husk
Corn stover
Explanation - Wood chips typically have a higher calorific value (~18‑20 MJ/kg dry) compared to agricultural residues like bagasse, rice husk, or corn stover.
Correct answer is: Wood chips
Q.10 During anaerobic digestion, the stage in which volatile fatty acids are converted to methane is called:
Hydrolysis
Acidogenesis
Acetogenesis
Methanogenesis
Explanation - Methanogenesis is the final biological step where methanogenic archaea transform acetate and hydrogen into methane.
Correct answer is: Methanogenesis
Q.11 Which pollutant is most effectively reduced by installing a selective catalytic reduction (SCR) system in a biomass boiler?
Particulate matter
Sulfur dioxide
Nitrogen oxides
Carbon monoxide
Explanation - SCR uses ammonia or urea to catalytically reduce NOₓ to N₂ and H₂O, achieving >90 % reduction.
Correct answer is: Nitrogen oxides
Q.12 What is the term for the process of converting biomass directly into liquid fuels via high‑temperature, short‑time heating?
Fermentation
Gasification
Pyrolysis
Combustion
Explanation - Fast pyrolysis rapidly heats biomass (≈500 °C, <2 s) to produce bio‑oil, char, and gases.
Correct answer is: Pyrolysis
Q.13 Which of the following is a major challenge when using algae as a biomass feedstock?
Low lipid content
High land requirement
Seasonal variation
Difficulty in harvesting and dewatering
Explanation - Algal cultures have low biomass concentration, making harvesting and water removal energy‑intensive.
Correct answer is: Difficulty in harvesting and dewatering
Q.14 The term 'biomass-to-liquid' (BTL) usually refers to:
Direct combustion of wood chips
Conversion of biomass into synthetic diesel via gasification and Fischer‑Tropsch synthesis
Fermentation of sugars to ethanol
Anaerobic digestion to produce biogas
Explanation - BTL processes gasify biomass to syngas, then convert it to liquid hydrocarbons using Fischer‑Tropsch chemistry.
Correct answer is: Conversion of biomass into synthetic diesel via gasification and Fischer‑Tropsch synthesis
Q.15 Which parameter most directly influences the rate of biomass pyrolysis?
Particle size
Ambient humidity
Fuel moisture content
Atmospheric pressure
Explanation - Smaller particles have larger surface‑to‑volume ratios, leading to faster heat transfer and quicker pyrolysis.
Correct answer is: Particle size
Q.16 In a combined heat and power (CHP) plant using biomass, the term 'cogeneration' means:
Generating electricity and useful heat from the same fuel source
Using two different fuels simultaneously
Storing excess electricity in batteries
Separating CO₂ from flue gas
Explanation - Cogeneration captures waste heat from power generation for district heating, improving overall efficiency.
Correct answer is: Generating electricity and useful heat from the same fuel source
Q.17 Which of the following best describes the Energy Return on Investment (EROI) for most modern biomass power plants?
Less than 1
Approximately 1
Between 2 and 5
Greater than 10
Explanation - Current biomass plants typically achieve an EROI of 2–5, meaning they produce 2‑5 units of energy per unit of energy invested in feedstock production and processing.
Correct answer is: Between 2 and 5
Q.18 Which of these is a primary advantage of using pelletized biomass over raw wood chips?
Higher moisture content
Uniform size and density for consistent combustion
Lower calorific value
Increased ash production
Explanation - Pellets have standardized dimensions and low moisture, enabling stable feed rates and efficient burning.
Correct answer is: Uniform size and density for consistent combustion
Q.19 What is the main chemical reaction occurring during the combustion of biomass?
CₓHᵧ + O₂ → CO₂ + H₂O + Heat
CₓHᵧ → CO + H₂ + Heat
CₓHᵧ + H₂O → CH₄ + CO₂
CₓHᵧ → C + H₂ + Heat
Explanation - Complete combustion oxidizes carbon and hydrogen in biomass to carbon dioxide, water, and releases heat.
Correct answer is: CₓHᵧ + O₂ → CO₂ + H₂O + Heat
Q.20 In the context of biomass energy, the term 'feedstock' refers to:
The electrical output of a turbine
The raw organic material used as fuel
The ash residue after combustion
The catalyst used in gasification
Explanation - Feedstock is any biological material—wood, crop residues, waste—that is processed to generate energy.
Correct answer is: The raw organic material used as fuel
Q.21 Which greenhouse gas is most directly reduced when biomass replaces coal in power generation?
Methane (CH₄)
Nitrous oxide (N₂O)
Carbon dioxide (CO₂)
Ozone (O₃)
Explanation - Biomass is considered carbon‑neutral because the CO₂ released during combustion is roughly equal to the CO₂ absorbed during growth, unlike fossil coal.
Correct answer is: Carbon dioxide (CO₂)
Q.22 Which of the following is NOT a typical use for the char produced in biomass gasification?
Soil amendment (biochar)
Activated carbon for filtration
Fuel for gas turbines
Carbon sequestration
Explanation - Char is a solid carbon material; it is not suitable as a direct fuel for gas turbines, which require gaseous or liquid fuels.
Correct answer is: Fuel for gas turbines
Q.23 What is the role of a cyclone separator in a biomass combustion system?
To remove moisture from the fuel
To separate ash particles from flue gases
To increase the temperature of the combustion chamber
To inject oxygen into the furnace
Explanation - Cyclones use centrifugal force to extract particulate matter (ash) from the exhaust stream before emission control devices.
Correct answer is: To separate ash particles from flue gases
Q.24 In a typical anaerobic digester, the optimal temperature range for mesophilic digestion is:
10‑20 °C
30‑40 °C
45‑55 °C
60‑70 °C
Explanation - Mesophilic microorganisms thrive at 30‑40 °C, offering stable biogas production with lower energy input than thermophilic ranges.
Correct answer is: 30‑40 °C
Q.25 Which technology can be combined with biomass combustion to improve overall plant efficiency to over 80 %?
Combined cycle (gas‑turbine/steam‑turbine)
Steam reforming
Electrolysis
Direct fuel cell
Explanation - A combined‑cycle plant uses the high‑temperature syngas from gasification to drive a gas turbine, then recovers waste heat in a steam turbine, boosting efficiency.
Correct answer is: Combined cycle (gas‑turbine/steam‑turbine)
Q.26 Which of the following best describes the term 'bio‑refinery'?
A plant that only produces electricity from biomass
A facility that converts biomass into a spectrum of bio‑based products and energy
A system for storing large quantities of wood chips
A method for drying biomass before combustion
Explanation - Bio‑refineries aim to maximize value by producing fuels, chemicals, and power from renewable biomass feedstocks.
Correct answer is: A facility that converts biomass into a spectrum of bio‑based products and energy
Q.27 The main reason why lignin is considered a high‑energy component of biomass is:
It contains nitrogen
It is highly soluble in water
It has a high carbon‑hydrogen ratio and aromatic structure
It is easily fermented
Explanation - Lignin’s complex, aromatic polymer yields more heat upon combustion compared to cellulose or hemicellulose.
Correct answer is: It has a high carbon‑hydrogen ratio and aromatic structure
Q.28 Which of the following is a typical by‑product of the Fischer‑Tropsch synthesis when processing biomass‑derived syngas?
Methanol
Ethanol
Hydrogen sulfide
Heavy waxes
Explanation - Fischer‑Tropsch converts syngas to a range of hydrocarbons, including long‑chain waxes that can be upgraded to diesel.
Correct answer is: Heavy waxes
Q.29 In biomass energy systems, the term 'pretreatment' most commonly refers to:
Cooling the combustion gases
Mechanical, chemical, or thermal processes that increase the accessibility of carbohydrates
Installing emission control equipment
Charging the battery storage
Explanation - Pretreatment breaks down lignocellulosic structures, improving enzymatic hydrolysis for bio‑fuel production.
Correct answer is: Mechanical, chemical, or thermal processes that increase the accessibility of carbohydrates
Q.30 Which of the following statements about biogas upgrading is TRUE?
Upgrading removes CO₂ to increase methane concentration.
Upgrading adds more CO₂ to the gas.
Upgrading converts methane to ethanol.
Upgrading reduces the calorific value of biogas.
Explanation - Biogas upgrading processes (e.g., water scrubbing, PSA) remove CO₂, producing biomethane with ~95 % methane suitable for grid injection.
Correct answer is: Upgrading removes CO₂ to increase methane concentration.
Q.31 Which factor most strongly affects the ash melting point in a biomass boiler?
Silica content
Carbon content
Moisture content
Nitrogen content
Explanation - High silica and other alkali metals lower the ash fusion temperature, increasing slagging risk.
Correct answer is: Silica content
Q.32 What is the typical lower heating value (LHV) range for dry wood pellets?
5‑8 MJ/kg
10‑12 MJ/kg
15‑20 MJ/kg
25‑30 MJ/kg
Explanation - Dry wood pellets possess an LHV of roughly 15‑20 MJ/kg, reflecting their high carbon content and low moisture.
Correct answer is: 15‑20 MJ/kg
Q.33 Which of the following is a main advantage of using torrefied biomass over raw biomass?
Higher water content
Improved grindability and energy density
Lower carbon content
Increased ash production
Explanation - Torrefaction reduces moisture and creates a brittle, high‑energy material that grinds more easily and transports more efficiently.
Correct answer is: Improved grindability and energy density
Q.34 The term 'bio‑hydrogen' most commonly refers to hydrogen produced via:
Steam reforming of natural gas
Electrolysis using solar power
Thermal cracking of biomass
Gasification of biomass followed by water‑gas shift
Explanation - Biomass gasification yields syngas (CO + H₂); the water‑gas shift reaction converts CO to additional H₂, producing bio‑hydrogen.
Correct answer is: Gasification of biomass followed by water‑gas shift
Q.35 Which of the following is NOT a typical waste product from a large‑scale biomass power plant?
Fly ash
Bottom ash
Slag
Petroleum coke
Explanation - Petroleum coke is a by‑product of oil refining, not biomass combustion.
Correct answer is: Petroleum coke
Q.36 In the context of biomass energy, the abbreviation 'LCA' stands for:
Low‑Carbon Analysis
Life‑Cycle Assessment
Liquid Carbonate Approximation
Linear Combustion Algorithm
Explanation - LCA evaluates the environmental impacts of a product or process from cradle to grave, commonly applied to biomass pathways.
Correct answer is: Life‑Cycle Assessment
Q.37 Which of the following processes converts biomass directly into electricity using high‑temperature plasma?
Plasma gasification
Fluidized‑bed combustion
Anaerobic digestion
Fermentation
Explanation - Plasma torches generate temperatures >3000 °C, breaking down biomass into syngas without oxygen, which can be used for power generation.
Correct answer is: Plasma gasification
Q.38 A major environmental concern associated with large‑scale wood pellet production is:
Increased nitrogen fixation
Deforestation and biodiversity loss
Elevated ozone formation
Acid rain generation
Explanation - Unsustainable harvesting for pellets can lead to forest degradation, affecting habitats and carbon storage.
Correct answer is: Deforestation and biodiversity loss
Q.39 Which of the following is a characteristic of a thermophilic anaerobic digester?
Operates at 30‑40 °C
Produces less biogas than mesophilic digester
Faster reaction rates and higher biogas yields
Requires extensive cooling systems
Explanation - Thermophilic digestion (≈55‑65 °C) accelerates microbial activity, increasing biogas production, albeit with higher energy input for heating.
Correct answer is: Faster reaction rates and higher biogas yields
Q.40 In a biomass‑fired power plant, the term 'stack gas' refers to:
The air supplied to the furnace
The flue gases exiting the chimney
The steam exiting the turbine
The fuel being fed into the boiler
Explanation - Stack gas is the mixture of combustion products (CO₂, CO, NOₓ, SO₂, particulates) discharged through the plant's stack.
Correct answer is: The flue gases exiting the chimney
Q.41 Which type of reactor is most commonly used for the production of bio‑ethanol from sugarcane juice?
Fixed‑bed reactor
Stirred‑tank (batch) fermenter
Fluidized‑bed reactor
Plug‑flow reactor
Explanation - Batch fermenters provide controlled, homogeneous conditions ideal for yeast fermentation of sugarcane juice to ethanol.
Correct answer is: Stirred‑tank (batch) fermenter
Q.42 Which of the following gases is most likely to be formed as a pollutant during incomplete biomass combustion?
Carbon monoxide (CO)
Neon (Ne)
Sulfur hexafluoride (SF₆)
Helium (He)
Explanation - Incomplete oxidation of carbon results in CO, a toxic pollutant commonly emitted from low‑temperature combustion.
Correct answer is: Carbon monoxide (CO)
Q.43 What is the typical carbon content (by weight) of dry wood biomass?
10‑20 %
30‑40 %
45‑55 %
65‑80 %
Explanation - Dry wood is composed of roughly 45‑55 % carbon, the main source of energy upon combustion.
Correct answer is: 45‑55 %
Q.44 Which of the following conversion technologies can produce renewable diesel directly from waste oil?
Hydrotreating
Gasification
Fermentation
Pyrolysis
Explanation - Hydrotreating (hydrodeoxygenation) removes oxygen from triglycerides, yielding renewable diesel (hydrotreated vegetable oil).
Correct answer is: Hydrotreating
Q.45 The term 'biomass densification' most commonly refers to:
Increasing the moisture content of biomass
Compressing biomass into briquettes or pellets
Converting biomass into liquid fuels
Drying biomass to below 5 % moisture
Explanation - Densification improves handling, transport, and combustion characteristics by forming compact fuel forms.
Correct answer is: Compressing biomass into briquettes or pellets
Q.46 Which of the following best explains why bio‑char can act as a carbon sink?
It is highly soluble in water
It decomposes quickly, releasing CO₂
Its stable aromatic structure resists degradation in soils
It contains high levels of nitrogen
Explanation - Bio‑char’s graphitic carbon persists for centuries, sequestering carbon when applied to soil.
Correct answer is: Its stable aromatic structure resists degradation in soils
Q.47 In a biomass gasifier, the zone where the solid fuel is partially oxidized to produce syngas is called:
Combustion zone
Char oxidation zone
Reduction zone
Drying zone
Explanation - The reduction zone has limited oxygen, allowing partial oxidation that yields CO and H₂ (syngas).
Correct answer is: Reduction zone
Q.48 Which of the following is a key parameter to monitor in a biogas reactor to avoid process failure?
pH
Wind speed
Solar irradiance
Water hardness
Explanation - Methanogenic microbes are sensitive to pH; optimal range is 6.8‑7.4, and deviations can inhibit biogas production.
Correct answer is: pH
Q.49 Which of the following fuels has the highest theoretical methane content when derived from biomass?
Wood chips
Algae oil
Sugarcane bagasse
Corn stover
Explanation - Algae can accumulate up to 50‑60 % lipids, which can be upgraded to methane‑rich biogas with higher CH₄ content.
Correct answer is: Algae oil
Q.50 What is the main purpose of a scrubber in a biomass power plant?
To increase steam pressure
To remove acidic gases such as SO₂ and HCl from flue gas
To dry the biomass feedstock
To cool the turbine blades
Explanation - Wet or dry scrubbers absorb acidic pollutants, reducing corrosion and meeting emission standards.
Correct answer is: To remove acidic gases such as SO₂ and HCl from flue gas
Q.51 Which of the following is an advantage of using a two‑stage gasifier over a single‑stage gasifier?
Higher moisture tolerance
Reduced tar formation
Elimination of ash handling
Lower capital cost
Explanation - The second stage promotes further cracking of tars, resulting in cleaner syngas.
Correct answer is: Reduced tar formation
Q.52 In the context of biomass energy, the term 'energy crop' refers to:
A crop grown primarily for food
A plant cultivated specifically for high biomass yield
A genetically modified organism
A crop that requires no fertilizers
Explanation - Energy crops (e.g., switchgrass, miscanthus) are selected for rapid growth and large dry matter production for fuel.
Correct answer is: A plant cultivated specifically for high biomass yield
Q.53 Which of the following conversion routes typically yields the highest overall energy efficiency for converting woody biomass into liquid fuels?
Fermentation to ethanol
Direct combustion
Pyrolysis followed by hydroprocessing
Anaerobic digestion
Explanation - Fast pyrolysis produces bio‑oil, which can be hydrotreated to drop oxygen and improve energy density, achieving higher efficiencies than fermentation.
Correct answer is: Pyrolysis followed by hydroprocessing
Q.54 Which of the following is a major factor limiting the direct use of algae as a solid fuel?
Low hydrogen content
High ash content
Low carbon density and high water content
Excessive nitrogen oxides emissions
Explanation - Algal biomass is ~80‑90 % water, resulting in low calorific value unless dewatered and dried.
Correct answer is: Low carbon density and high water content
Q.55 Which of the following is the primary driver for the formation of NOₓ in biomass combustion?
Fuel nitrogen content
High combustion temperature
Low oxygen supply
High ash content
Explanation - Thermal NOₓ is produced when atmospheric nitrogen reacts at temperatures above ~1300 °C.
Correct answer is: High combustion temperature
Q.56 What is the purpose of a heat exchanger in a biomass‑based CHP system?
To generate electricity directly from biomass
To recover waste heat from exhaust gases for district heating
To separate methane from biogas
To compress flue gases
Explanation - Heat exchangers transfer thermal energy from hot streams (e.g., flue gas) to a secondary fluid used for heating.
Correct answer is: To recover waste heat from exhaust gases for district heating
Q.57 Which of the following is a characteristic of a 'drop‑in' biofuel?
It can be used without any modifications to existing engines or infrastructure
It must be blended at >50 % with petroleum fuel
It requires a new type of combustion chamber
It is only suitable for aircraft turbines
Explanation - Drop‑in fuels are chemically compatible with conventional petroleum fuels, allowing direct substitution.
Correct answer is: It can be used without any modifications to existing engines or infrastructure
Q.58 Which of the following processes is used to remove water and volatile organics from bio‑oil to improve its stability?
Catalytic cracking
Hydrotreatment (hydrodeoxygenation)
Steam reforming
Fermentation
Explanation - Hydrotreatment reacts bio‑oil with hydrogen over a catalyst, reducing oxygen, water content, and improving fuel quality.
Correct answer is: Hydrotreatment (hydrodeoxygenation)
Q.59 The main reason for using a 'dual‑fuel' system (biomass + natural gas) in some power plants is:
To increase CO₂ emissions
To improve load flexibility and reduce fuel cost
To eliminate the need for ash handling
To produce more bio‑char
Explanation - Dual‑fuel operation allows quick ramp‑up with natural gas while maintaining a renewable base load with biomass.
Correct answer is: To improve load flexibility and reduce fuel cost
Q.60 Which of the following best describes the concept of ‘carbon capture and storage’ (CCS) when applied to biomass power plants?
Capturing CO₂ from the atmosphere and storing it underground
Capturing CO₂ from the plant’s flue gas and storing it to achieve negative emissions
Storing biomass in carbon‑neutral landfills
Using CO₂ to enhance plant growth
Explanation - When CO₂ from biomass combustion is captured and sequestered, the system can result in net removal of atmospheric CO₂.
Correct answer is: Capturing CO₂ from the plant’s flue gas and storing it to achieve negative emissions
Q.61 Which of the following is a key challenge for scaling up municipal solid waste (MSW) to bio‑energy conversion?
Uniform feedstock composition
Low moisture content
Heterogeneous composition leading to variable calorific value
Absence of ash formation
Explanation - MSW contains diverse materials; inconsistent fuel quality complicates combustion and emissions control.
Correct answer is: Heterogeneous composition leading to variable calorific value
Q.62 What is the typical temperature range for the catalytic cracking of bio‑oil in a hydrocracking unit?
150‑250 °C
300‑400 °C
500‑600 °C
700‑800 °C
Explanation - Hydrocracking operates at moderate temperatures (300‑400 °C) with high hydrogen pressure to break long‑chain molecules.
Correct answer is: 300‑400 °C
Q.63 In a biomass‑based district heating system, the term 'thermal storage' typically refers to:
Electrical batteries
Large water tanks or phase‑change material tanks storing heat
Compressed air vessels
Hydrogen storage tanks
Explanation - Thermal storage buffers excess heat, allowing supply during peak demand periods.
Correct answer is: Large water tanks or phase‑change material tanks storing heat
Q.64 Which of the following is a common method for reducing the sulfur content in biomass before combustion?
Washing with water
Steam explosion pretreatment
Alkali treatment
Mechanical shredding
Explanation - Water washing can leach soluble sulfates and other inorganic contaminants, lowering sulfur emissions.
Correct answer is: Washing with water
Q.65 Which of the following statements about the 'energy balance' of a biomass system is correct?
It compares the total electricity generated to the total CO₂ emitted.
It evaluates the net energy output after subtracting energy used for cultivation, harvesting, and processing.
It measures the ratio of ash to fuel.
It is the same as the plant’s thermal efficiency.
Explanation - Energy balance accounts for all energy inputs across the lifecycle to determine net energy gain.
Correct answer is: It evaluates the net energy output after subtracting energy used for cultivation, harvesting, and processing.
Q.66 Which of the following is NOT a typical product of the catalytic conversion of syngas derived from biomass?
Methanol
Dimethyl ether (DME)
Ammonia
Synthetic diesel
Explanation - Ammonia production requires nitrogen; typical syngas conversion routes produce methanol, DME, or hydrocarbons, not ammonia.
Correct answer is: Ammonia
Q.67 The primary reason for employing a 'blowdown' system in a biomass boiler is:
To increase steam pressure
To remove dissolved solids and prevent scaling
To add more water to the system
To vent excess biogas
Explanation - Blowdown discards a portion of boiler water containing concentrated minerals, protecting heat exchange surfaces.
Correct answer is: To remove dissolved solids and prevent scaling
Q.68 Which of the following is a major advantage of using a 'fluidized‑bed' gasifier over a 'fixed‑bed' gasifier for heterogeneous feedstocks?
Lower operating temperature
Better fuel flexibility and uniform temperature distribution
Higher ash production
Simpler design with no moving parts
Explanation - Fluidization provides intense mixing, handling variable particle sizes and moisture levels more effectively.
Correct answer is: Better fuel flexibility and uniform temperature distribution
Q.69 Which of the following is a common indicator of feedstock quality for solid biofuel applications?
High nitrogen content
Low heating value
High ash and moisture content
Uniform particle size and low moisture
Explanation - Consistent size and low moisture ensure stable combustion and efficient handling.
Correct answer is: Uniform particle size and low moisture
Q.70 In a biomass combustion system, the term 'slagging' refers to:
The formation of liquid ash that adheres to furnace walls
The generation of sulfuric acid in the flue gas
The production of excessive CO₂
The rapid cooling of exhaust gases
Explanation - Slagging occurs when ash melts at high temperature and deposits on surfaces, impairing heat transfer.
Correct answer is: The formation of liquid ash that adheres to furnace walls
Q.71 Which of the following is a key environmental benefit of converting agricultural residues into bio‑energy?
Increasing the use of chemical fertilizers
Reducing open-field burning and associated air pollution
Depleting soil organic matter
Increasing water consumption
Explanation - Utilizing residues for energy prevents harmful open burning, improving air quality and health.
Correct answer is: Reducing open-field burning and associated air pollution
Q.72 Which of the following statements about the 'Water–Gas Shift (WGS)' reaction in biomass gasification is correct?
It converts CO₂ to CO and water.
It converts CO and H₂O to CO₂ and H₂, increasing hydrogen yield.
It produces methane directly from syngas.
It removes sulfur from the gas stream.
Explanation - The WGS reaction (CO + H₂O → CO₂ + H₂) is used to boost H₂ content in syngas.
Correct answer is: It converts CO and H₂O to CO₂ and H₂, increasing hydrogen yield.
Q.73 What is the typical range of the Higher Heating Value (HHV) for dried wood chips?
5‑8 MJ/kg
12‑14 MJ/kg
18‑20 MJ/kg
25‑30 MJ/kg
Explanation - Dry wood chips exhibit HHV values around 18‑20 MJ per kilogram of dry matter.
Correct answer is: 18‑20 MJ/kg
Q.74 Which of the following is a primary reason for integrating a biomass plant with a district heating network?
To increase flue gas temperature
To provide a use for waste heat, improving overall efficiency
To eliminate the need for a turbine
To increase ash production
Explanation - District heating captures low‑grade waste heat, raising the combined heat‑and‑power (CHP) efficiency.
Correct answer is: To provide a use for waste heat, improving overall efficiency
Q.75 In the context of biomass conversion, the term 'thermochemical' refers to processes that:
Use microorganisms to break down biomass
Employ heat and chemical reactions without biological agents
Rely on photosynthesis
Only produce solid fuels
Explanation - Thermochemical routes (combustion, gasification, pyrolysis) use heat and chemistry, unlike biochemical methods.
Correct answer is: Employ heat and chemical reactions without biological agents
Q.76 Which of the following fuels derived from biomass typically has the lowest sulfur content?
Wood pellets
Coal-derived fuel oil
Heavy fuel oil
Petroleum diesel
Explanation - Biomass contains negligible sulfur, so wood pellets emit very low SO₂ compared with fossil fuels.
Correct answer is: Wood pellets
Q.77 What is the primary purpose of a 'steam trap' in a biomass boiler system?
To remove condensate while preventing steam loss
To increase boiler pressure
To inject fuel into the boiler
To control flue gas composition
Explanation - Steam traps discharge water condensate, preserving the energy contained in the steam.
Correct answer is: To remove condensate while preventing steam loss
Q.78 Which of the following feedstocks is most commonly used for the production of biodiesel via transesterification?
Corn stover
Soybean oil
Wood chips
Rice husk
Explanation - Soybean oil is a high‑oil-content vegetable oil, widely used for biodiesel production through transesterification.
Correct answer is: Soybean oil
Q.79 In a biomass gasification plant, the 'char' produced can be utilized for:
Direct combustion in a gas turbine
Manufacture of activated carbon and soil amendment
Cooling the syngas
Electrolyzing water
Explanation - Char's porous structure makes it suitable for activated carbon production or as bio‑char for soil improvement.
Correct answer is: Manufacture of activated carbon and soil amendment
Q.80 Which of the following is an essential factor for achieving high carbon capture efficiency in a biomass CCS plant?
Low pressure in the capture unit
High concentration of CO₂ in the flue gas
Use of high‑temperature steam turbines
Operating at low ambient temperature
Explanation - Higher CO₂ partial pressure improves absorption efficiency, reducing energy penalties of capture.
Correct answer is: High concentration of CO₂ in the flue gas
Q.81 Which of the following statements accurately describes the term 'negative emissions' in the context of biomass energy with CCS?
Emissions are lower than zero because no CO₂ is released.
More CO₂ is removed from the atmosphere than is emitted during the lifecycle.
The plant emits only nitrogen oxides.
The system consumes more fuel than it produces energy.
Explanation - Biomass combustion releases CO₂ that was recently captured by plants; capturing and storing it results in net atmospheric CO₂ removal.
Correct answer is: More CO₂ is removed from the atmosphere than is emitted during the lifecycle.
Q.82 What is the main purpose of a 'dry scrubber' (or dry sorbent injection) in a biomass power plant?
To remove particulate matter only
To absorb acidic gases such as SO₂ and HCl using solid alkaline materials
To cool the exhaust gases
To increase the humidity of the flue gas
Explanation - Dry sorbents (e.g., limestone) react with acidic gases, forming solid salts that can be removed with ash.
Correct answer is: To absorb acidic gases such as SO₂ and HCl using solid alkaline materials
Q.83 Which of the following is a typical operating pressure range for a biomass‑fed gas turbine in a combined‑cycle plant?
0.1‑0.5 MPa
1‑3 MPa
5‑10 MPa
15‑20 MPa
Explanation - Industrial gas turbines often operate at inlet pressures of 1‑3 MPa to achieve high efficiency.
Correct answer is: 1‑3 MPa
Q.84 In a bio‑ethanol production process, the step that converts starch into fermentable sugars is called:
Hydrolysis
Fermentation
Distillation
Catalytic cracking
Explanation - Enzymatic or acid hydrolysis breaks down starch polymers into glucose, which can then be fermented to ethanol.
Correct answer is: Hydrolysis
Q.85 Which of the following best describes a 'closed‑loop' biomass system?
Biomass is burned and the ash is dumped in landfills.
Biomass residues are reused as fertilizer after combustion, completing a nutrient cycle.
Biomass is exported to other countries for processing.
The system uses only imported biomass.
Explanation - Closed‑loop systems aim to recycle nutrients (e.g., ash as fertilizer), minimizing waste.
Correct answer is: Biomass residues are reused as fertilizer after combustion, completing a nutrient cycle.
Q.86 Which of the following is the most common method for measuring the calorific value of a solid biomass sample?
Gas chromatography
Bomb calorimeter
Thermogravimetric analysis (TGA)
Fourier‑transform infrared spectroscopy (FTIR)
Explanation - A bomb calorimeter combusts a known mass of fuel in an oxygen‑rich environment and measures the heat released.
Correct answer is: Bomb calorimeter
Q.87 Which of the following is the main advantage of using a 'pressurized' (or 'high‑pressure') water‑gas shift reactor in a biomass gasification plant?
It reduces the need for downstream cooling
It increases the equilibrium conversion to hydrogen
It eliminates the formation of tar
It allows direct feeding of syngas to a turbine
Explanation - Higher pressure shifts the WGS equilibrium toward more H₂ production, improving hydrogen yield.
Correct answer is: It increases the equilibrium conversion to hydrogen
Q.88 Which of the following is a typical characteristic of the 'biomass–to–hydrogen' (BTH) route?
Direct electrolysis of water
Gasification followed by water‑gas shift and hydrogen purification
Fermentation of sugars to hydrogen
Combustion in a boiler
Explanation - BTH processes generate syngas via gasification, convert CO to CO₂ and H₂, then purify the hydrogen stream.
Correct answer is: Gasification followed by water‑gas shift and hydrogen purification
Q.89 In a biomass‑based power plant, the term 'auxiliary power consumption' refers to:
The electricity generated by the plant
The power used by auxiliary equipment such as pumps, fans, and controls
The power sold to the grid
The heat lost in the exhaust
Explanation - Auxiliary consumption reduces net output; minimizing it improves overall plant efficiency.
Correct answer is: The power used by auxiliary equipment such as pumps, fans, and controls
Q.90 Which of the following best explains why torrefied biomass is often termed 'bio‑coalfuel'?
It contains high amounts of metallic ash
It has a high moisture content
It exhibits a coal‑like appearance, density, and calorific value
It is made from actual coal mixed with biomass
Explanation - Torrefaction yields a brittle, low‑moisture, high‑energy solid resembling coal, facilitating transport and handling.
Correct answer is: It exhibits a coal‑like appearance, density, and calorific value
Q.91 The main environmental benefit of using a 'dry‑flue‑gas' system in a biomass plant is:
Higher combustion temperature
Reduced water consumption and lower corrosion
Increased ash production
Higher CO₂ emissions
Explanation - Dry‑flue‑gas systems avoid steam injection for cooling, saving water and minimizing corrosion in heat exchangers.
Correct answer is: Reduced water consumption and lower corrosion
Q.92 Which of the following is a key factor influencing the choice between using wood chips versus agricultural residues as a biomass feedstock for a power plant?
Color of the fuel
Availability, logistics, and seasonal variation
Magnetic properties
Electrical conductivity
Explanation - Feedstock choice depends on supply chain reliability, transport distance, and storage considerations.
Correct answer is: Availability, logistics, and seasonal variation