Types of Coal PDF

## Types of Coal - **Peat:** The first stage in the formation of coal from wood. It contains a huge amount of moisture and therefore must be dried for about 1 to 2 months before it is put to use. It is used as a domestic fuel in Europe and for power generation in Russia. In India, it is generally n...

## Types of Coal - **Peat:** The first stage in the formation of coal from wood. It contains a huge amount of moisture and therefore must be dried for about 1 to 2 months before it is put to use. It is used as a domestic fuel in Europe and for power generation in Russia. In India, it is generally not considered a good fuel. - **Lignites and brown coals:** Intermediate stages between peat and coal. They have a woody or clay-like appearance and are usually associated with high moisture, high ash, and low heat content. Lignites are typically amorphous in character and can break easily, making transportation challenging. They burn with a smoky flame and are suitable for local use only. - **Bituminous coal:** Burns with long yellow and smoky flames and has a high percentage of volatile matter. The average calorific value of bituminous coal is about 31350 kJ/kg. It can be of two types, namely caking or non-caking. - **Semi-bituminous coal:** Softer than anthracite. It burns with a very small amount of smoke. It contains 15 to 20 percent volatile matter and has a tendency to break into small sizes during storage or transportation. - **Semi-anthracite:** Has less fixed carbon and less luster compared to true anthracite. It gives out longer and more luminous flames when burnt. - **Anthracite:** A very hard coal with a shining black luster. It ignites slowly unless the furnace temperature is high. It is non-caking and has a high percentage of fixed carbon. It burns either with very short blue flames or without flames. Its calorific value is high (about 35500 kJ/kg) making it suitable for steam generation. ## Types of Coal and its Composition | Type of Coal | Carbon % mass | Hydrogen % mass | Age | |---|---|---|---| | Anthracite | | | | | Carbonaceous | | | | | Bituminous | | | | | Sub-bituminous | | | | | Lignitous | | | | | Peat | | | | | Wood | | | | ## Coal Properties The basis of a coal analysis defines the conditions under which the coal is tested. * **As-mined basis:** Freshly taken from the mine. * **As-fired basis:** Resided in a coal pile for months and analyzed just before burning. * **As-received basis:** Examined immediately after transport from the mine. ### a. Moisture content The moisture content of coal ranges from about 5% to almost 70%. Moisture is undesirable because it reduces the heating value (water does not burn!) and increases transportation costs. It is determined by heating an air-dried coal sample at 104-110 °C for 1 hour until a constant weight is obtained. Generally, moisture content increases with decreasing rank and ranges from 1 to 40 percent for the various ranks of coal. ### b. Volatile Combustible Material (VCM) When a coal sample is heated in the absence of air, it loses weight due to the expulsion of volatile matter. The volatile matter content of coals ranges from 2% to about 50%. Volatile matter is material that is driven off when coal is heated to 900 °C in the absence of air for 7 minutes in a closed crucible. It is measured practically by determining the loss of weight and includes volatile carbon, combined water, net hydrogen, nitrogen, and sulfur. ### c. Mineral (Ash) content Coal contains a variety of minerals in varying proportions that are transformed into ash when burned. The amount and nature of the ash affect the design and type of ash-handling system used in coal utilization plants. Ash is the residue that remains when a weighed sample of coal is slowly heated in an open crucible for 2 hours at 500-815 °C. ### d. Fixed carbon content (FC) Fixed carbon is the solid combustible residue that remains after a coal particle is heated and volatile matter is expelled. It is determined by subtracting the percentages of moisture, volatile matter, and ash from a sample. Since gas-solid combustion reactions are slower than gas-gas reactions, a high fixed-carbon content indicates that the coal will require a long combustion time. Fixed carbon content of coals, not including moisture and ash, ranges from 50% to about 98%. Anthracites, which contain a high proportion of fixed carbon, are popular domestic heating fuels. While they may be difficult to ignite, they burn steadily for a long time with a short, clean flame. ### e. Calorific Value The amount of chemical energy stored in a coal that is released as thermal energy upon combustion is known as calorific value. It is measured in British thermal units or megajoules per kilogram. Of the components determined by proximate analysis, only the volatile matter and fixed carbon actually burn and liberate thermal energy. Since the moisture and ash contents of coals can be quite variable from one coal to another, and will further depend on whether the coal was partially dried or cleaned, any comparison of coals based on the combustible material must be corrected for the presence of moisture and ash. Similarly, the heating value is lowered by the presence of non-combustible moisture and ash. The formula to calculate Fixed Carbon is as follows: $FC = 100 - N - VCM - Ash$ ### Comparing Coal: - Comparing only the combustible part of coals requires that we know the heating value unaffected by moisture or ash. To make such comparisons, we correct the values of fixed carbon, volatile matter and calorific values to a moisture and ash-free basis. - Knowing the properties of coals on a moisture- and ash-free basis allows us to classify (or rank) coals. ## Testing Analysis of Solid Fuels ### 1. Proximate analysis The proximate analysis determines the moisture, volatile combustible matter, fixed carbon, and ash content of the coal. This analysis of coal gives a good indication about heating and burning properties of coal. ### 2. Ultimate analysis A more precise analysis that identifies the chemical composition of coal with respect to the elements like carbon, hydrogen, oxygen, nitrogen, sulfur, and ash. - **Carbon and hydrogen** are the principal combustible elements in coal. On a weight basis, carbon is the predominant one. It constitutes about 60% to about 95% of the total. For most coals of 90% or less carbon, hydrogen content is generally in the range of 5%; it drops to about 2% for coals having 95% carbon. - **Nitrogen** content of almost all coals is in the range of 1-2%. - **Oxygen** content is inversely related to carbon content. For example, coals of 65% carbon may contain 30% oxygen, while coals of 95% carbon may contain only 2-3% oxygen. This is significant because the more oxygen a coal contains, the easier it is to start to burn it, or to achieve its ignition. - **Sulfur** content of coals is seen to be quite variable. - A **precise chemical determination of the % by weight of the six basic components of coal:** - Carbon - Hydrogen - Nitrogen - Sulfur - Ash - Oxygen ## Classification of Coal by Ranks | Class and group | Fixed carbon (%) | Volatile matter (%) | Heating value (BTU/lbs) | |---|---|---|---| | **I. Anthracite** | | | | | 1. Meta anthracite | >98 | <2 | | | 2. Anthracite | 92-98 | 2-8 | | | 3. Semi anthracite | 86-92 | 8-14 | | | **II. Bituminous** | | | | | 1. Low volatile | 78-86 | 14-22 | | | 2. Medium volatile | 69-78 | 22-31 | >14,000 | | 3. High volatile A | <69 | >31 | 13,000-14,000 | | 4. High volatile B | | | 10,500-13,000 | | 5. High volatile C | | | | | **III. Subbituminous** | | | | | 1. Subbituminous A | | | 10.500-11.500 | | 2. Subbituminous B | | | 9500-10.500 | | 3. Subbituminous C | | | 8300-9500 | | **IV. Lignite** | | | | | 1. Lignite A | | | 6300-8300 | | 2. Lignite B | | | <6300 | ## Coal Utilization There are three major pathways for coal utilization. The principal process by which coal is used is combustion as shown in the figure below. **Pathways to Coal Utilization** - **Mining** - **Processing** - **Transport** - **Combustion** - **Carbonization** - **Conversion** ### 1. Combustion Combustion involves burning the coal in air to liberate thermal energy (heat). The heat is used as such for comfort or to carry out many industrial processes that require high temperatures; it is also used to generate steam for use in electric power plants. ### 2. Carbonization The heating of coal to high temperatures in the absence of air, it is used in manufacturing coke for the metallurgical industry. ### 3. Conversion Various chemical processes to transform coal into gaseous or liquid fuels, called synthetic fuels. Common to all these processes is prior mining of the coal, its preparation (processing) and its transportation to the consumers. ## Manufactured Solid Fuels ** 1. Charcoal and its characteristics:** - Derived from destructive distillation of wood, being left in the shape of solid residue. - Burns rapidly with a clear flame, producing no smoke and developing heat of about 6,050 cal/kg. **2. Coke and its characteristics:** - Obtained from destructive distillation of coal, being left in the shape of solid residue. - Soft coke is obtained as the solid residue from the destructive distillation of coal in the temperature range of 600-650°C. It contains 5 to 10% volatile matter & burns without smoke. - Hard coke is obtained as solid residue from the destructive distillation of coal in the temperature range of 1200-1400°C. It burns with smoke and is a useful fuel for metallurgical processes. **3. Briquettes and their characteristics:** - The term briquettes are used in respect of the dust, culm, slack and other small size waste remains of lignite, peat, coke, etc. compressed into different shapes of regular form, with or without binder. ## Liquid Fuels **Advantages** - **Higher calorific value** per unit mass than solid fuels. - **Burn without dust, ash, clinkers, etc.** - **Easy to transport through pipes.** **Disadvantages** - **Higher cost** compared to solid fuels. - **Require special storage tanks.** - **Increased risk of tire hazards** due to volatile and inflammable properties. ### Petroleum or crude oil A basic fossil fuel, petroleum is a dark greenish brown, viscous mineral oil, found deep in earth's crust. It is mainly composed of various hydrocarbons (like straight chain paraffins, cycloparaffins or napthenes, olefins, and aromatics) together with small amounts of organic compounds containing oxygen, nitrogen, and sulfur. An average crude oil can yield to 20 to 30% of gasoline, 30 to 45% of intermediate fractions, and 25 to 50% of residual fuel oil. ### Classification of Petroleum - **Paraffinic Base Type Crude Petroleum::** Mainly composed of the saturated hydrocarbons from CH4 to C35H72 and a little of the napthenes and aromatics. The hydrocarbons from C18H38 to C35H72 are sometimes called waxes. - **Asphaltic Base Type Crude Petroleum:** Contains mainly cycloparaffins or napthenes with smaller amounts of paraffins and aromatic hydrocarbons. - **Mixed Base Type Crude Petroleum:** Contains both paraffinic and asphaltic hydrocarbons and are generally rich in semisolid waxes. ### Petroleum Products - A fractional distillation column is used to separate petroleum into its various constituents. The heavier fractions have higher boiling points and condense out at the higher temperatures in the lower part of the column, while the lighter fractions condense out at the lower temperatures in the upper portion of the column. - Some common fuels produced in this manner are gasoline, kerosene, jet engine fuel, diesel fuel, and fuel oil. ### The products refined from the liquid fractions of crude oil can be placed into ten main categories: - **Asphalt:** A colloid of asphaltenes and maltenes is commonly used to make roads. It is separated from the other components of crude oil by fractional distillation. It goes through a process called "blowing" where it is reacted with oxygen to make it harden. It is usually stored and transported at around 300° Fahrenheit. - **Diesel:** Produced by fractional distillation between 392° Fahrenheit and 662º Fahrenheit. Diesel has a higher density than gasoline, it is simpler to refine from crude oil and is most commonly used in transportation. - **Fuel Oil:** Any liquid petroleum product that is burned in a furnace to generate heat. The six classes of fuel oil are: - Distillate fuel oil - Diesel fuel oil - Light fuel oil - Gasoil - Residual fuel oil - Heavy fuel oil. - Residual fuel oil and heavy fuel oil are commonly known as navy special fuel oil and bunker fuel; both are often called furnace fuel oil. - **Gasoline:** Almost half of all crude oil refined in the United States is made into gasoline. It is mainly used as fuel in internal combustion engines, like the engines in cars. Gasoline is a mixture of paraffins, naphthenes, and olefins, although the specific ratios of these parts depend on the refinery where the crude oil is processed. - **Kerosene:** Collected through fractional distillation at temperatures between 302° Fahrenheit and 527° Fahrenheit. It is a combustible liquid that is thin and clear and is used as jet fuel and as heating fuel. In the early days of oil, kerosene replaced whale oil in lanterns. In the early 21st century, kerosene was used to power New York City Transit buses. Now, kerosene is used as fuel in portable stoves, kerosene space heaters, and in liquid pesticides. - **Liquefied Petroleum Gas:** A mixture of gases that are most often used for heating appliances, aerosol propellants, and refrigerants. Different kinds of liquefied petroleum gas, or LPG, are propane and butane. At normal atmospheric pressure, liquefied petroleum gas will evaporate, so it needs to be contained in pressurized steel bottles. - **Lubricating Oil:** Manufactured by special processes such as solvent extraction, catalytic dewaxing, hydrocracking, and isohydromerization. Different lubricating oils are classified as paraffinic, naphthenic, or aromatic are used between two surfaces to reduce friction and wear. Motor oil, which protects moving parts inside an internal combustion engine is a well-known example. - **Paraffin Wax:** A white, odorless, tasteless, waxy solid at room temperature. The melting point of paraffin wax is between 117° Fahrenheit and 147° Fahrenheit. It is an excellent electrical insulator, second only to Teflon. Used in drywall to insulate buildings and is also an acceptable wax used to make candles for the Jewish Menorah. - **Bitumen:** A thick, black, sticky material also known as tar. It is obtained in the bottom fraction when crude oil is refined. Its boiling point is high (977° Fahrenheit), which is why it does not rise in the distillation chamber. It is used in paving roads and waterproofing roofs and boats. It is also used in thin plates and used to soundproof dishwashes and hard drives in computers.. - **Petrochemicals:** The chemical products made from the raw materials of petroleum. - Ethylene: used to make anesthetics, antifreeze, and detergents. - Propylene: used to produce acetone and phenol. - Benzene: used to make other chemicals and explosives. - Toluene: used as a solvent and in refined gasoline. - Xylene: used as a solvent and cleaning agent. ## Jet Fuel A type of aviation fuel designed for use in aircraft powered by gas-turbine engines. Jet A and Jet A-1, which are produced to a standardized international specification, are most commonly used for commercial aviation. Jet fuel is a mixture of a large number of different hydrocarbons. Their sizes (molecular weights or carbon numbers) is restricted by the requirements for the product, for example, freezing point or smoke point. - **Kerosene-type jet fuel (including Jet A and Jet A-1)** has a carbon number distribution between about 8 and 16 carbon numbers. - **Wide-cut or naphtha-type jet fuel (including JetB)**, between about 5 and 15 carbon numbers. ## Properties of Petroleum The elemental composition of petroleum is much less variable than that of coal: 83-87% carbon, 11-16% hydrogen, 0-4% oxygen plus nitrogen, and 0-4% sulfur. Note that most crude oils contain substantially more hydrogen than coals. ## Properties of Liquid Fuels - **Density:** The ratio of the mass of the fuel to the volume of the fuel at a reference temperature of 15°C. Measured with an instrument called a hydrometer and used for quantity calculations and assessing ignition quality. The unit of density is kg/m3. - **Specific Gravity:** The ratio of the weight of a given volume of oil to the weight of the same volume of water at a given temperature.. The specific gravity of water is 1 and measured using a hydrometer. - **Viscosity:** A measure of a fluid’s internal resistance to flow. Depends on temperature and decreases as temperature increases. Measured in Stokes / Centistokes. viscosity is also quoted in Engler, Saybolt or Redwood. Each type of oil has its own temperature - viscosity relationship. Measured by an instrument called a Viscometer. An important characteristic in the storage and use of fuel oil. affects atomization, the degree of pre-heat required for handling, storage and pump, and ignites the burner. - If too viscous, it can become difficult to pump, hard to light the burner, and tough to operate. Poor atomization can lead to the formation of carbon deposits on the burner tips or on the walls. Therefore, pre-heating is necessary for proper atomization. - **Flash point:** The lowest temperature at which the fuel can be heated so that the vapor gives off flashes momentarily when an open flame is passed over it. The flash point of furnace oil is 66°C. - **Pour point:** The lowest temperature at which it will pour or flow when cooled under prescribed conditions. A rough indication of the lowest temperature at which fuel oil is readily pumpable. - **Specific Heat:** The amount of kcals needed to raise the temperature of 1 kg of oil by 1°C. The unit of specific heat is kcal/kg/℃. It varies from 0.22 to 0.28 depending on the oil specific gravity. The specific heat determines how much steam or electrical energy it takes to heat oil to a desired temperature. Light oils have a low specific heat, whereas heavier oils have a higher specific heat. - **Calorific value:** The measurement of heat or energy produced, and is measured either as gross calorific value or net calorific value. The difference being the latent heat of condensation of the water vapor produced during the combustion process. - **Gross calorific value (GCV):** Assumes all vapor produced during the combustion process is fully condensed. - **Net calorific value (NCV):** Assumes the water leaves with the combustion products without fully being condensed. - Fuels should be compared based on the net calorific value. - **Sulfur:** The amount of sulfur in the fuel oil depends mainly on the source of the crude oil and to a lesser extent on the refining process. The normal sulfur content for the residual fuel oil (furnace oil) is in the order of 2- 4 percent. The main disadvantage of sulfuric is the risk of corrosion by sulfuric acid formed during and after combustion, and condensing in cool parts of the chimney or stack, air pre heater and economizer. - **Ash Content:** Related to the inorganic material in the fuel oil. The ash levels of distillate fuels are negligible. Residual fuels have more of the ash-forming constituents. The salts (sodium, vanadium, calcium, magnesium, silicon, iron, aluminum, nickel, etc.) can cause fouling deposits in the combustion equipment. Excessive ash in liquid fuels can cause fouling deposits in the combustion equipment. Ash has erosive effect on the burner tips, causes damage to the refractories at high temperatures and gives rise to high temperature corrosion and fouling of equipment. - **Carbon residue:** Indicates the tendency of oil to deposit a carbonaceous solid residue on a hot surface, such as a burner or injection nozzle, when its vaporizable constituents evaporate. Residual oil contains carbon residue ranging from one percent or more. - **Water content:** Water content of furnace oil when supplied is normally very low as the product at refinery site is handled hot and a maximum limit of 1% is specified in the standard. Water may be present in free or emulsified form and can cause damage to the inside furnace surfaces during combustion especially if it contains dissolved salts. It can also cause spluttering of the flame at the burner tip, possibly extinguishing the flame and reducing the flame temperature or lengthening the flame. - **Octane Number:** Indicates the tendency of gasoline to knock when the compression ratio in a spark ignition engine is raised. - **Cetane Number:** Ranks fuels according to ignition delay when undergoing standard test. - **Smoke Point:** Measures the tendency of a liquid fuel to form soot. - **Ignition Temperature:** Sometimes called 'autoignition temperature' this is the minimum temperature at which the material will ignite without a spark or flame being present. - **Flammability Limits in Air:** The percent concentration in air (by volume) is given for the lower and upper limit. These values give an indication of relative flammability. The limits are sometimes referred to as "lower explosive limit" (LEL) and "upper explosive limit" (UEL). - **Fire Point:** The lowest temperature, corrected to one atmosphere pressure (101.3 kPa), at which the application of a test flame to the oil sample surface causes the vapor of the oil to ignite and burn for at least five seconds. - **Reid Vapor:** The pressure that vapor exerts on its surroundings. It is measured at a reference temperature of 15°C. For volatile petroleum products, vapor pressure is measured by a variety of methods, including Reid, dynamic,, static, isoteniscopic, vapor pressure balance, and gas saturation. - **Hydrogen Sulfide:** Unlike other sulfur compounds in crude oils, which tend to accumulate in the distillation residue, is evolved during distillation or other heating processes. - **Alcohols:** Oxygenated hydrocarbons where a hydrogen atom was replaced by an OH radical. - Methanol: A common alcohol produced as a product of the carbonization of wood, or through a synthesis process ($2H2 + CO → CH_3OH$). The process yields about 75% methanol and 25% heavier alcohols, which are then separated by fractional distillation. - Ethanol: Obtained from fermentation of sugars, followed by fractional distillation. ## Gaseous Fuels Gaseous fuels occur in nature, besides being manufactured from solid and liquid fuels. The advantages and disadvantages of gaseous fuels are given below: **Advantages** - **Conveyed easily through pipelines** to the actual place of need. - **Eliminates manual labor** in transportation. - **Lighted easily.** - **Free from impurities** found in solid and liquid fuels. **Disadvantages** - **Very large storage tanks are needed.** - **Highly inflammable** so chances of fire hazards in their use is high. ### Natural Gas - **Generally associated with petroleum deposits** and is obtained from wells dug in the oil-bearing regions. - **Methane is the main constituent** of natural gas, accounting for about 95% of the total volume. - **Other components:** Ethane, Propane, Butane, Pentane, Nitrogen, Carbon Dioxide, and traces of other gases. Very small amounts of sulfur compounds are also present. - **Since methane is the largest component of natural gas,** generally properties of methane are used when comparing the properties of natural gas to other fuels. ### Characteristics of Natural Gas - **Fossil fuel formed from plant and animal remains** millions of years ago. - **Hydrocarbon component** with methane as a major component. - **Colorless and odorless**; a commercial odorant is added to allow users to detect the gas for safety. - **Lighter than air** with a specific gravity of about 0.6-0.8.. - **Disperses upward** and dissipates into the air quickly. It is inflamed during a range of 5-15% by volume of gas in air. - **Self-ignition temperature** of natural gas is 537-540 degree Celsius. - **Clean fuel** with cleaner burning nature; lower environmental impact when compared with other types of fuel. ### Liquefied Petroleum Gas (LPG) A byproduct of natural gas processing or the crude oil refining. It consists mainly of propane and thus is usually referred to as propane. However, it also contains varying amounts of butane, propylene, and butylenes. ### Manufactured Gases - **Important manufactured gaseous fuels** from solid and liquid fuels. - **Coal gas:** Obtained when it is carbonized or heated in the absence of air at about 1300°C in either coke ovens or gas-making retorts. Coal gas is a colorless gas having a characteristic odor. It is lighter than air and burns with a long smoky flame. It is used in metallurgical operations for providing reducing atmosphere. - **Blast furnace gas:** Byproduct flue gas obtained during the reduction of iron ore by coke in the blast furnace. This gas contains much dust and is usually cleaned before use by dust settlers, cyclones or electrolytic precipitators. - **Water gas:** A mixture of combustible gases CO and H2 with a little traction of non-combustible gases. Made by passing alternatively steam and air through a bed of red-hot coal or coke maintained at about 900 to 1000°C in a rector, which consists of a steel vessel - **Producer gas:** A mixture of combustible gases carbon monoxide and hydrogen associated with non-combustible gases N2. CO2. etc. It is prepared by passing air mixed with little steam (about 0.35 kg/kg of coal) over a red-hot coal or coke bed maintained at about 1100°C in a special reactor called gas producer. - **Biogas:** Obtained from the decomposition of organic matter by bacteriological action in closed digesters, in the absence (or nearly) oxygen. It requires a high moisture content Organic matter (provided it has high chamber moisture content) can be of various origins, either plant or animal, being very common the use of organic manure In operation the digesters maintain a temperature around 30 to 40 °C Since the process is not totally anaerobic, the gas has a significant percentage of CO2, but the solid waste is a good fertilizer. - **Town gas:** Also known as low-temperature or lighting gas, obtained at low- and medium temperature coal gasification. - **Coke gas:** Obtained at the high-temperature coal gasification. - **Hydrogen:** Produced on the industrial size by reforming of natural gas (methane). Reforming means acting of water steam on natural gas in the presence of nickel catalyst at the temperature approx. 800 °C. ### Properties of Gaseous Fuels - **Heating Value:** The heat release per unit mass when the fuel initially at 25°C reacts completely with oxygen and products returned to 25°C. The heating value is reported as higher heating value (HHV) when the water is condensed or as the lower heating value (LHV) when the water is not condensed. LHV is obtained by: $LHV = HHV - \frac{mh_{fg}}{m_{fuel}}$ where $h_{fg}$ is the latent heat of vaporization of water at 25 °C which equals 2,140 kJ/kg water. The heating value of gaseous fuel may be obtained experimentally in a flow calorimeter and can be calculated from thermodynamics if the composition is known. - **Higher Heating Value (HHV):** Assumes that the water vapor in the products condenses and thus includes the latent heat of vaporization of the water vapor. - **Lower Heating Value (LHV):** Does not contain the latent heat; the water in flue gas remain in steam form at the initial temperature. - **Relative density:** $d = \frac{density_{gas}}{density_{air}}$ **Ranges:** - d < 0.8 - light gas (e.g. natural gas CH4) - 0.8 < d < 1.2 - medium category (e.g. CO) - 1,2 < d - heavy gas (e.g. LPG - propane-butane) - **Wobbe index (for assessment of gas exchange)** - **Flammability limits (%)** - **Flammability limits:** Also called flammable limits, give the proportion of combustible gases in a mixture, between which limits this mixture is flammable. The lower flammable limit describes the leanest mixture that is still flammable (mixture with the smallest fraction of combustible gas). The upper flammable limit gives the richest flammable mixture. ## Renewable Fuels Renewable fuels (biomass) are formed in a year or a few years basis (synthetic fuels may come from fossil or from renewable sources): - **Gaseous:** Biogas from anaerobic fermentation or gasogen gas from pyrolysis of biomass. - **Liquid:** Alcohols, ethers (biopetrol), esters (biodiesel). - **Solid:** Wood, charcoal, fuel pellets (from wood or vegetable residues), agriculture residues, cattle manure, urban waste. In comparison with fossil fuels, particularly with oil and gas, renewable fuels are more disperse, have less energy content, more moisture and ash content, and require more handling effort (but they are renewable). ## Biofuels The term biofuels, biomass fuels and renewable fuels, may be used indistinctly if they refer to natural or artificial fuels obtained from renewable sources, although other times distinctions are introduced and then biofuels may refer to biomass derivatives directly substituting fossil fuels for the same combustor, biomass may be restricted to unprocessed biomass (forest waste, crop residues, animal waste, domestic waste), and renewable fuel may include fuels like hydrogen obtained by electrolysis and not from biomass. ### Some disadvantages of biofuels: - **Biomass fuels are mostly solid,** and some pre-processing is needed (gasification, liquefaction) to produce fluid fuels, the kind of fuels best fitted to both engines and stationary combustors. - **Biomass fuels are less energetic** than fossil fuels, because living matter is roughly a water suspension of oxygenated hydrocarbons, and fossil fuels were slowly cooked over the eons to separate water and most of the oxygen. Besides, some biomass fuels have non-fuel components that must be separated (e.g. soil in forest-waste, metals in industrial waste. - **Biomass fuels are contaminant;** not contributing to global warming (because the CO2 produced compensates with that synthesized from the air during the biomass growth), but producing much more particulates and new chemical emissions (e.g. -dioxins) if not properly treated.. ### **The Biofuels Act or Republic Act (RA) 9367** Signed in January 2007 making the Philippines the first country in Southeast Asia to have biofuels legislation in place. Sugarcane and molasses are used in Philippine ethanol production, while coconut oil (CNO), where coconut methyl ester (CME) is derived, is the preferred biodiesel feedstock. The current blend mandates are 10 percent and two percent for ethanol and biodiesel, respectively: - **Bioethanol:** Ethanol (C2H5OH) produced from feedstock and other biomass; - **Biodiesel:** Fatty Acid Methyl Ester (FAME) or mono-alkyl esters derived from vegetable oils or animal fats and other biomass derived oils that shall be technically proven and approved by the DOE for use in diesel engines with quality specifications in accordance with Philippine National standards (PNS); - **Bioethanol Fuel:** Hydrous or anhydrous bioethanol suitable denatured for use as motor fuel, with quality specifications in accordance with the PNS; - **Biofuel:** Bioethanol and biodiesel and other fuels made from biomass and primarily used for motive, thermal and power generation with quality specifications in accordance with the PNS; - **Biofuel blends:** Gasoline or diesel that has been blended with biofuels such as, but not limited to, bioethanol and biodiesel; - **Biomass:** Any organic matter, particularly cellulosic or lignocellulosic matter, which is available on a renewable or recurring basis, including trees, crops and associated residues, plant fiber, poultry litter and other animal wastes, industrial wastes, and the biodegradable component of solid waste: ### Some biofuel production methods considered are: - **Ethanol by fermentation of biomass sugars, starch or cellulose by yeast or bacteria.** In Japan, a bacteria has been bred which produces ethanol from paper or rice-straw without any pre-treatment. - **Methane (actually a biogas mixture) by anaerobic digestion of biomass waste (manure, straw, sewage, municipal solid waste (MSW)).** - **Oils (biodiesel) by reforming oleaginoseous plant seeds (eg. colza, sunflower, soya).** The marine microscopic algae Botryococeus Brauni has been shown to accumulate a quantity of hydrocarbons amounting to 75% of their dry weight - **Methanol from wood-waste distillation.** - **Hydrogen by reforming other biofuels (eg. ethanol or methane), or from water electrolysis by solar or wind energy.**