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Biomass role in Energy consumption
Figure 4-1: Biomass Role in U.S. Energy Consumption
Figure 4-2: Photosynthesis
Figure 4-3: Greenhouse Gas Emissions
Biomass is renewable. Properly managed, new fuel sources can be planted to replace those that are harvested.
It is virtually carbon neutral. The crop planted to replace the crop converted to fuel (ethanol in this example) will in theory absorb the greenhouse gas emissions generated by burning the biofuel.
There are significant advantages as well as concerns raised when biomass is harvested as a fuel source. Advantages include:
(continued)
Biomass is relatively inexpensive. Biofuels can be manufactured at costs comparable to fossil fuel sources.
It reduces dependency on non-renewable imported oil and gas.
There are significant advantages as well as concerns raised when biomass is harvested as a fuel source. Advantages include: (continued)
(continued)
Biomass supports the growth of agriculture, forestry and other rural economic development.
It helps to stabilize commodity prices by providing a consistent and large demand source.
Biofuels are non-toxic and biodegradable.
There are significant advantages as well as concerns raised when biomass is harvested as a fuel source. Advantages include: (continued)
Often no modifications to conventional internal combustion engines are required to use biofuels.
It takes advantage of wasted potential energy by harvesting waste products that otherwise would simply end up in a landfill.
Figure 4-4: The Biofuel Carbon Cycle
Food versus Fuel. There is a concern that if the growing of biofuels proves more lucrative than the growing of food, farmers will convert their land to producing fuel and food production will decline. It is feared that this will lead to massive food shortages and higher prices. In 2008, over a six-month period of time, the price of corn increased 67% largely due to a perception that ethanol production would consume a significant amount of the corn production. Berkley Perspective
The disadvantages of biomass as a fuel source include:
(continued)
Not enough biomass. There are concerns that there simply is not enough biomass on the planet to meet current and anticipated energy demands. A 2003 study found that it would require 22 percent of all the plant matter grown each year worldwide to supply biofuel to meet the needs of current energy demands (this is roughly twice what is currently utilized to supply the agricultural needs of the planet). For example, if ALL the corn produced in the U.S. was converted to ethanol, it would only supply 10% of the energy currently supplied by gasoline. GeneratorSpirulina Algae. At Home
The disadvantages of biomass as a fuel source include: (continued)
(continued)
Not carbon neutral. Depending on the crop used in the biofuel conversion, the process may not be carbon neutral as it often takes a significant amount of fossil fuels to grow the crop. Studies in the UK have found that biofuels in their current form save only about 50-60% of the carbon emissions as compared to burning fossil fuels. This is significant, but not the 100% claimed by many proponents of biofuels. The U.S. Environmental Protection Agency (EPA) has found that when land use conversion is factored into the production of ethanol (forests, for example, cut down to plant corn) - using ethanol actually INCREASES greenhouse gas emissions by 5% over a 30-year period of time.
The disadvantages of biomass as a fuel source include: (continued)
(continued)
Fear of impact. There is a fear that if a significant portion of the agricultural land is dedicated to crops to support biofuels, biodiversity will suffer (for example, rain forests may be cut down to support biofuel “plantations.”) Deforestation currently accounts for about a fifth of the world’s greenhouse-gas emissions, according to Greenpeace.
The disadvantages of biomass as a fuel source include: (continued)
(continued)
Soil Erosion. Intensive land management for increased crop yields has resulted in significant soil erosion. The Iowa Natural Resources Inventory has found that land used to produce crops for ethanol loses about 4.9 tons of soil per acre. This is the equivalent of 21 pounds of soil for every gallon of fuel (2.5 kilograms per liter).Proper Cropping for conservation
The disadvantages of biomass as a fuel source include: (continued)
(continued)
Airborne Pollution. The burning of biomass releases a large number of airborne particulates. This can be a major health concern, especially in developing nations where biomass is a major source of fuel for cooking and heating.What is Black Carbon?
The disadvantages of biomass as a fuel source include: (continued)
20 in 10: In 2007 U.S. President George W. Bush announced an initiative targeting a 20% reduction in fossil fuel consumption within 10 years (2017) primarily through the use of biofuels.
Many powerful groups have lobbied government officials to incorporate biofuels as a significant component in a national energy policy. Some of these initiatives include:
(continued)
25 x ‘25: A non-partisan lobbying effort (promoted primarily by agricultural and forestry industry interests) began in 2004 to promote a national policy resulting in 25% of all fuel consumption in the U.S. obtained from managed agricultural and forestry sources by the year 2025.
Many powerful groups have lobbied government officials to incorporate biofuels as a significant component in a national energy policy. Some of these initiatives include: (continued)
(continued)
The Biomass Technical Advisory Committee: A committee established by the U.S. Congress to determine the future direction of federal biomass funding. A report published in 2005 envisioned a domestic energy market where 30% of energy consumption was supplied from biomass.
Many powerful groups have lobbied government officials to incorporate biofuels as a significant component in a national energy policy. Some of these initiatives include: (continued)
Yields per acre for corn, wheat and other small grains will increase by more than 50% over the coming years
The technology for recovering crop residue (materials left behind when harvesting) improves to become 75% efficient (currently less than 40% efficient)
In order to achieve U.S. government projected goals, however, a number of assumptions were made. These include:
(continued)
All cropland (100%) will be managed using no-till methods (a process of harvesting where crop residue is left on the surface of the soil - no plowing - to ensure consistent soil moisture and temperature for future planting), up from about 13% today
55 million acres of cropland and pasture will be converted to growing perennial biomass crops (such as switchgrass, willow and other woody materials)
In order to achieve U.S. government projected goals, however, a number of assumptions were made. These include: (continued)
(continued)
No significant increase or reduction in farming acreage (from current agricultural inventories of 455 million acres to 448 million acres in 2030)
All manure except that which is applied on the farm where it is produced for soil embellishment will be used as biomass
In order to achieve U.S. government projected goals, however, a number of assumptions were made. These include: (continued)
All available residuals (zero waste) will be used as biomass
Figure 4-6: Potential Sources for Biomass
Logging and other timber residues (branches, stumps, etc.) through forest management (Silviculture)
Anticipated sources for biomass include:
(continued)
Fuel treatment (removing excess brush and trees to manage forests in an effort to avoid damaging forest fires)
Firewood (for wood stoves, furnaces, etc.)
Urban wood residues (such as tree trimmings, wood from demolished homes, etc.)
Pulp residues (black liquors from paper processing contain chemicals and unprocessed pulp. Technology to gasify these liquors may provide a more efficient energy source than simply burning them.)
Anticipated sources for biomass include: (continued)
(continued)
Bark, slabs and sawdust from wood processing
Grains (factoring in increased yields)
Perennial crops such as switchgrass, poplar and willow
Crop residues (corn stalks, etc)
Anticipated sources for biomass include: (continued)
Process residues (waste material collected when plant material is used in the production cycle). These include manure from animals, municipal waste, industrial waste (for example, about 20% of the corn kernel is wasted when corn is converted to ethanol), and others.
Reduce soil erosion
Achieving U.S. government projected targets envisions a significant increase in the harvesting of residual crop materials. However, these materials serve some very useful purposes when left in the field. They:
(continued)
Reduce soil compaction
Increase the organic content of the soil
Increase moisture holding capacity of the soil
Reduce the need for pesticides and fertilizers
Achieving U.S. government projected targets envisions a significant increase in the harvesting of residual crop materials. However, these materials serve some very useful purposes when left in the field. They: (continued)
Provide food and habitat for wildlife, including beneficial soil enhancing organisms
Accessibility to forests. Much of the available biomass contained within forests is simply not accessible (no roads, steep terrain, etc).
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include:
(continued)
Public resentment. If large swaths of timber were harvested to provide energy, public sentiment may quickly turn against biomass as an alternative fuel source.
Transportation costs. Moving timber can cost between $.20-.60 per mile per ton. Unless conversion facilities are located close to the source, this transportation cost will add significantly to the cost of utilizing biofuels as an energy source.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Labor availability. A significant portion of the biomass from woodlands is obtained through reducing the fuel load to prevent forest fires. This requires skilled forestry workers in numbers that are likely not available.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Federal policy. Forest management is a long-term process. Government policies currently do not provide significant incentives for programs such as tree planting and woodlands management (less than ½ of one percent of agricultural payments to farmers).
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Contamination of materials. Recovered wood products (from urban residue and industrial residue) can add significantly to the cost of processing. These materials often contain non-biomass components (plastics, asbestos, oil paints, etc) that must be cleaned or removed during processing.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Changing farming habits. Utilizing crop residues, no-till farming, and conversion to perennials require significant changes in the culture of farming. These farming practices are slow to change unless there are significant financial incentives.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Damage to the soil. Removing residuals from the soil will likely lead to lower soil quality (need for additional fertilizers) as well as increased soil erosion. Raising corn, for instance, erodes the soil about 12 times faster than it can naturally be replenished.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Water. Increasing production will almost certainly require additional water resources - many of which are already unreliable and stretched to capacity. Again, the production of corn depletes ground water 25% faster (on average) than it can be recharged.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Crop Storage. Farming is seasonal, with periods of plenty and periods of low production. During times when harvests are good, there may be need for significant storage facilities to handle the excess production. These infrastructure needs add cost and complexity to the system.
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
(continued)
Concentration of Resources. Many fear that biofuel production will increasingly concentrate control of food resources and prices within large agri-business producers and processors (accelerating the trend away from small family farm production).
Other concerns in achieving U.S. government projected targets by a significant increase in the harvesting of residual crop materials include: (continued)
Marginalize small-scale agriculture and lead to the widespread conversion of forests and other sensitive ecosystems
In 2005 a group of about 100 non-profit non-governmental organizations (NGOs) wrote to the United Nations warning that increased use of biofuels will:
(continued)
Lead to very high food prices and cause hunger, malnutrition and impoverishment amongst the poorest sectors of society
Lead to rural unemployment and depopulation
In 2005 a group of about 100 non-profit non-governmental organizations (NGOs) wrote to the United Nations warning that increased use of biofuels will: (continued)
(continued)
Destroy the traditions, cultures, languages and spiritual values of indigenous peoples and rural communities
Lead to a more extensive use of agro-chemicals, which will affect human health and sensitive ecosystems
Lead to the destruction of watersheds and the pollution of rivers, lakes and streams
In 2005 a group of about 100 non-profit non-governmental organizations (NGOs) wrote to the United Nations warning that increased use of biofuels will: (continued)
Cause droughts and other local and regional climatic extremes (due to deforestation)
Put the food system at risk through the extensive use of genetically modified organisms (in an effort to boost crop production).
Access: All producers, large and small must have access to the biomass marketplace
Initiatives such as the 25 x ‘25 publish a list of goals that are incorporated into biomass proposals to address concerns such as:
Air Quality: Use of biomass must improve air quality, not damage it. Use of biomass must also result in a net decrease in greenhouse gas emissions.
(continued)
Biodiversity: Native, rare and threatened plant and animal species must be protected.
Initiatives such as the 25 x ‘25 publish a list of goals that are incorporated into biomass proposals to address concerns such as: (continued)
Invasive and Non-Native Species: Invasive species must not be introduced in an effort to increase biomass yields.
(continued)
Soil Quality: Biomass production should seek to enhance soil quality and avoid erosion.
Initiatives such as the 25 x ‘25 publish a list of goals that are incorporated into biomass proposals to address concerns such as: (continued)
Water Quality and Quantity: Production of biomass should not adversely impact available water resources or water quality.
Municipal waste
There exist a number of alternative sources that hold promise in producing significant quantities of fuel. These include:
Food and crop waste
Animal waste
Algae
Switchgrass
Figure 4-7: Inexpensive Biodigestor
Figure 4-8: Mature Switchgrass
Combustion: Biomass can simply be burned to generate heat and/or electricity. Since the dawn of time, wood has been used as a primary heat source. Today about 3% of the U.S. electrical energy is obtained through the burning of wood, wood waste and municipal waste.
All organic material contains the potential for energy which can be extracted in a number of ways. These include:
(continued)
Gasification: Biomass can be heated to form a synthetic gas call Syngas. Syngas can then be used to generate electricity or can be converted into fuels such as ethanol, methanol or hydrogen.
All organic material contains the potential for energy which can be extracted in a number of ways. These include: (continued)
(continued)
Fermentation and Biodigestion: The sugars contained within plant material can be broken down by yeast to produce carbon dioxide and alcohol. This process is known as Fermentation and is the basis for ethanol production. Similarly, the organic material in biomass can also break down to form methane and carbon dioxide. This process (known as biodigestion), as well as fermentation, are both anaerobic processes (taking place in oxygen-free environments).
All organic material contains the potential for energy which can be extracted in a number of ways. These include: (continued)
Figure 4-9: Pellet Stove
The price of woodchips is relatively stable or they can often be obtained for free from wood trimming activities (such as clearing for power lines).
Advocates of the Woodchip Boiler technology point to the following advantages of woodchips:
(continued)
The energy required to create wood chips is a fraction of that required to produce wood pellets.
Green chips can be used, eliminating the need to dry or season wood.
Chips can be transported by dump truck (reducing handling and cost) and are typically produced from local sources.
Advocates of the Woodchip Boiler technology point to the following advantages of woodchips: (continued)
Wood chips can be produced from waste material or brush.
Figure 4-10: Reliance on Biomass in Developing Nations
Direct-firing
Biopower system technologies include:
Co-firing
Pyrolysis
Gasification (syngas)
Anaerobic digestion
Table 4-1: Average Heat Content from Various Biomass Sources
Table 4-2: Energy and Bulk Densities Characteristics of Selected Materials
Figure 4-11: Wood-to-gas Converted Vehicle
Biogas - a mixture of carbon dioxide (CO2) and methane (CH4)
The anaerobic digestion process generates three main products:
Fiber - can be used as a nutrient-rich soil conditioner
Liquor - can be used as liquid fertilizer
Mesophilic
The two major anaerobic digestion process:
Thermophilic
Methanol, ethanol and other alcohols
Officially recognized alternative fuels (by the U.S. Government) include:
Blends of 85 % or more alcohol with gasoline
Domestically produced natural gas
Liquefied petroleum gas (propane)
Coal-derived liquid fuels
Hydrogen
Electricity
Biodiesel (B100)
Green Diesel (fuels other than alcohol derived directly from biological materials)
Figure 4-12: Annual U.S. Ethanol Production
Lower emissions: Ethanol contains oxygen, making the combustion process within the engine more efficient. As a result, the fuel burns cleaner with less carbon monoxide, nitrogen oxides and other greenhouse gases emitted.
Alcohol fuels offer significant advantages over gasoline. These advantages include:
Higher octane: Ethanol boosts the octane content of the fuel mix (113 versus 87 for regular unleaded gasoline) without toxic chemicals such as benzene, toulene and xylene (which are often used for this purpose).
(continued)
Biodegradable: If accidentally spilled, ethanol will naturally degrade, leaving no lasting environmental impact.
Alcohol fuels offer significant advantages over gasoline. These advantages include: (continued)
Domestic supply: Supports a domestic agricultural economy
Proven technology: The production of alcohol is a time-tested technology and the resulting product can be used in existing internal combustion engines without significant modification.
Food versus Fuel: In 2006, 17% of the U.S. corn crop was used in the production of ethanol. During that same year, the price of corn shot up 66%, largely based on increasing ethanol production demands. Producing a significant portion of domestic fuel production from food crops raises serious concerns. It is estimated that the amount of corn necessary to produce enough ethanol to fill an SUV one time will feed a person for a year.
Disadvantages of alcohol fuels include:
(continued)
Disadvantages of alcohol fuels include: (continued)
(continued)
Available resources: Critics argue that there simply is not enough suitable farmland to produce the amount of grains necessary to manufacture ethanol in the quantities required. The amount of farmland in the U.S. has actually declined during the past 50 years, as shown in Figure 4-13.
Figure 4-13: U.S. Cropland
Disadvantages of alcohol fuels include: (continued)
(continued)
Production energy costs: Some scientists have argued that it requires up to six times the amount of fossil fuels to produce ethanol than the energy contained within the final product. Industry proponents counter that these estimates are flawed and/or are based on older production techniques.
Disadvantages of alcohol fuels include: (continued)
(continued)
Lower energy content: Ethanol contains less energy for a given volume than does gasoline (83,333 Btu per gallon versus 124,800 Btu). As a result, vehicles will experience lower mileage per gallon.
Disadvantages of alcohol fuels include: (continued)
(continued)
Distribution issues: Ethanol-blended fuels are corrosive and tend to separate when transported in pipelines. Therefore, ethanol blends cannot be shipped by pipeline - adding significantly to transportation costs. Additionally, grain production is rural in nature. Grain-based fuels will incur considerable costs moving the product to population centers.
Disadvantages of alcohol fuels include: (continued)
Infrastructure: Higher ethanol blends (such as E85) require custom pumps and storage tanks. As a result, E85 is available at less than 1% of gasoline retail stations.
Flex-fuel vehicles: In order to burn fuel blends greater than 10% ethanol, vehicles must be specially adapted. Flexible fuel vehicles can burn blends up to 85% ethanol (E85). While numbers are growing, E85 vehicles still represent a minority of cars on the road.
Figure 4-14: Projected Biofuel Feedstocks
The Cellulosic Biofuel technology advantages include:
(continued)
Available resources: Cellulosic biofuel production offers perhaps the only viable solution to large production demands based on available resources. Studies indicate that an efficient conversion process could produce significant amounts of biofuel from currently available waste materials and perennial crops that can be produced on marginally productive farmland.
The Cellulosic Biofuel technology advantages include: (continued)
No fertilizers and pesticides: A major energy input in traditional biofuel production is the need for fertilizers and pesticides in the production of grains. Most of these fertilizers are fossil-fuel based. Cellulosic materials require little or no fertilizers or pesticides.
Lignin: Cellulosic biomass contains Lignin, a natural fiber that can also serve as an energy-rich fuel to run biofuel processing plants. These plants might operate solely on the energy supplied by this byproduct of production.
The Cellulosic Biofuel Technology disadvantages include: (continued)
High cost: The cost of producing cellulosic ethanol is much higher than costs associated with traditional production methods. It is hoped that as the technology matures, these costs will decline.
Biodiversity damage: Increased production demands may lead to the introduction of invasive species, and damage to biodiversity (diverse environments converted to mono-crop production).
The Butanol advantages include:
(continued)
Vehicle modifications: Butanol can be blended at higher rates with gasoline without the need for modifications to the vehicle. It is considered “substantial similar” to gasoline and some advocates claim it can be substituted up to 100% as a total replacement to gasoline in unmodified vehicles.
The Butanol advantages include: (continued)
Transportation: Butanol does not break down in pipelines, so it can be transported using traditional methods, reducing costs.
Higher energy content: The energy contained in butanol (110,000 Btu per gallon) is much closer to gasoline (124,800 Btu per gallon) than ethanol. So vehicle miles-per-gallon would not be affected as dramatically.
The Butanol disadvantages include:
Untested: This technology is not commercially available, so all benefits are theoretical at the present time.
Low yields: Industrial production of butanol produces relatively low yields (in the 15-25% range) of fuel.
Costs: As an experimental technology, butanol production is very expensive when compared to alternative fuels.
Figure 4-15: World Biodiesel Production
Table 4-3: Average Vegetable Oil Yields (per acre) from Common Biodiesel Crops
Biodiesel advantages include:
(continued)
Compatibility: Biodiesel can be used in any modern diesel engine without modification.
Cleaner burning: Biodiesel burns cleaner within a diesel engine than does traditional diesel fuel and possesses excellent lubricating properties - which can extend the life of the engine.
Higher efficiency: Biodiesel burns more efficiently than does Petrodiesel (diesel fuel from petroleum). This results in lower emissions.
Biodiesel advantages include: (continued)
(continued)
Lower carbon emissions: As with all biofuels, the energy from biodiesel comes from plant material, the growing of which (theoretically) offsets the carbon emissions from burning the product. The U.S. Department of Energy estimates that biodiesel emits 78% less carbon dioxide than does petrodiesel.
Odors: Diesel fuel and diesel engine emissions produce an odor most find unpleasant. The burning of biodiesel, however, produces a odor that smells faintly of french fries if produced with recycled cooking oil.
Biodiesel advantages include: (continued)
(continued)
Biodegradable: Like ethanol, biodiesel spills will degrade naturally, leaving no lasting impact on the environment.
Higher flash point: Biodiesel has a flash point twice as high as petrodiesel, making it less likely to ignite when the diesel vehicle is involved in an accident.
Biodiesel advantages include: (continued)
Heating oil: Number 2 heating oil is essentially the same a petrodiesel. Biodiesel blends up to 20% (20% biodiesel) can be used in conventional fuel oil furnaces (just as in diesel engines) with no modification to the equipment. Residential consumption of No. 2 heating oil in the U.S. was 6.6 billion gallons (25 billion liters) in 2001. Blending heating oil (with 20% biodiesel) would result in an additional 1.3 billion gallons (5 billion liters) of biodiesel production.
Biodiesel disadvantages include:
(continued)
Lower energy: The energy content of biodiesel is lower than that of traditional petrodiesel (121,000 Btu per gallon as compared with 129,000 Btu per gallon). This lower energy content results in about a 5% decrease in power and fuel efficiency for biodiesel.
Bacteria: In warmer climates, bacteria may grow within fuel tanks, clogging filters and fuel lines. This occurs with both petrodiesel and biodiesel - although tests indicate that adding biodiesel may accelerate the problem. Fuel additives (biocides) are available to eliminate this problem.
Biodiesel disadvantages include: (continued)
(continued)
Cold weather: Diesel engines are often difficult to start in cold climates. This is because petrodiesel forms paraffin wax crystals (“clouds”) when the operating temperature falls below 20°F (-7°C). When temperatures fall to 5°F (-15°C) the fuel can reach a Pour Point, where it thickens and will not flow through fuel lines. Biodiesel clouds and gels at warmer temperatures than does petrodiesel. Complicating matters, biodiesel made with different oil feedstock will gel at different temperatures.
Biodiesel disadvantages include: (continued)
Dissolves rubber: In older vehicles, low quality plastics and natural rubber can be dissolved by biodiesel. This is likely not a problem on vehicles produced after 1994.
A good solvent: Biodiesel is an excellent solvent that will break down and loosen deposits left in the fuel tank and fuel system by conventional diesel fuel. This is a good thing (as they fuel system will be cleaned) but is also a bad thing in that fuel filters may become clogged with loosened material.
Straight Vegetable Oil disadvantages include:
Conversion: The burning of SVO requires extensive conversion of the vehicle. Adapting a vehicle (even for a do-it-yourself mechanic) will cost between $300-$1,500.
Engine damage: SVO as a fuel requires switching between fuel sources. Any miscalculations may result in severe engine damage.
(continued)
City driving: This system is not practical for short trips, as the SVO does not reach temperatures necessary to operate within the engine.
Straight Vegetable Oil disadvantages include: (continued)
Filters: SVO systems require the yellow grease be extensively filtered, both before it is put in the tank and after. Fuel filters typically must be changed every 200-300 miles.
Approvals: SVO is not an EPA-approved fuel. Use will void engine manufacturer’s warranties.
(continued)
Straight Vegetable Oil disadvantages include: (continued)
Glycerine: The glycerine which is the waste product in the production of biodiesel is still present in SVO. As the fuel burns, the glycerine may leave deposits within the system, reducing the life of the engine.
New engine damage: Newer diesel engines equipped with catalytic converters were never intended to run on SVO and can very quickly be damaged or “poisoned”.
Green Diesel advantages include:
(continued)
Better performance: Green diesel is essentially identical to petrodiesel, but with a few advantages. It has a lower cloud point, so cold weather performance is actually better than traditional diesel fuels (and much better than biodiesel). It also has a higher energy content than biodiesel (123,000 Btu/gallon vs 121,000 Btu/gallon) but is still lower than petrodiesel (129,00 Btu/gallon).
Green Diesel advantages include: (continued)
All the advantages of biodiesel: As green diesel is still derived from vegetable oils, it possesses all the environmental and sustainable advantages of biodiesel.
Oil Refinery technology: Hydro-processing capacity is already incorporated into most oil refineries. This capacity can be leveraged to produce large quantities of green diesel in existing refineries with only modest modifications.
Green Diesel disadvantages include:
Experimental: Like so many green technologies, this process has not been tested on a commercial scale. Many of the cost and production estimates are therefore theoretical.
Food vs. Fuel: This process still relies on oils produced from food stock sources. Large-scale production again raises the issues associated with “best-use” concerns for food production and distribution.
Biomass-to-Liquid advantages include:
Biofuel: As this fuel source is derived from biomass rather than fossil fuels, it possesses all the benefits of other biofuel sources (renewable, low-emissions, etc).
Food vs. Fuel: As the fuel source is cellulosic in nature, it does not utilize potential food as a source of energy.
Biomass-to-Liquid disadvantages include:
Cost: BTL diesel costs about 10% more than petrodiesel.
Lower energy and performance: Energy content and performance issues are similar to those of other biodiesel fuels.
Energy intensive: The U.S. Dept of Energy has raised concerns that the F-T process is quite energy intensive.
Technical
Future growth of the biomass fuel industry (which includes biopower, biofuels and biogas production) will be dependent upon a number of factors:
Economic
Infrastructure
Resource Limitations
If resource limitations are to be overcome, the industry must:
Significantly increase yields from existing crops and farmland.
Find more land to convert to biomass production.
Change the resource required, moving from food stock to cellulosic biomass such as perennials, waste, woodlands and dedicated oilseed crops.
As the biomass energy market expands, changes within the existing energy infrastructure will be required.
Fuel pumps: There are currently only a small number of pumps (currently less than 1%) in use that are capable of dispensing high concentration ethanol biofuel.
Flex Fuel Vehicles: While a significant number of new vehicles are designed to run on fuels containing a higher concentration of ethanol, they still represent a very small portion of the existing vehicle stock.
(continued)
As the biomass energy market expands, changes within the existing energy infrastructure will be required. (continued)
Pipelines: Currently ethanol cannot be shipped via existing pipelines. A cost-effective distribution system will need to be developed if demand is to expand dramatically. Most U.S. biodiesel production facilities are located in the mid-west (where the grain crops are produced), as shown in Figure 4-16. Most demand (population centers) is located along the coasts.
Figure 4-16: U.S. Biofuel Production Facilities
The acceptance of any technology is ultimately governed by economics. These constraints include:
Cost of fossil fuels: Low fossil fuel prices have limited the expansion of alternative energy in recent decades. When fossil fuel prices soar, so does interest in biomass fuel. Inconsistent and low fossil fuel prices will dampen the expansion of biofuels.
(continued)
The acceptance of any technology is ultimately governed by economics. These constraints include: (continued)
Feedstock prices: 57% of the cost of ethanol and 78% of the cost of biodiesel production is the cost of feedstock. As fuel prices increase, so do the costs of energy-intensive feedstock (such as corn and soy). The result is that as fossil fuel costs rise, the cost of producing biofuels also rises. This lowers the economic competitiveness of biofuels.
(continued)
The acceptance of any technology is ultimately governed by economics. These constraints include: (continued)
Saturation of co-product markets: The economic viability of biofuel production is dependent upon the sale of valuable co-products (such as glycerine and germ-meal animal feed). Large-scale production will saturate these specialized markets, lowering the price and therefore decreasing the profitability of biofuel production.
(continued)
The acceptance of any technology is ultimately governed by economics. These constraints include: (continued)
Governmental tax policy: Government has attempted to encourage the development of biofuels through tax policies such as tax credits ($0.51/gallon for ethanol, $1.00/gallon for biodiesel for virgin oil stocks) and import tariffs on biofuels from other countries (for example, a $0.54/gal tariff on ethanol imported from Brazil). However, these policies are often inconsistent and typically short-term in scope. The lack of a long-term consistent alternative fuels public policy has tended to constrain biofuel production in the United States.
Many of the Biomass energy techniques are still experimental and have not been tested in commercial conditions. A significant number of technical barriers still exist:
Crop yield efficiencies. Growth projections assume a tremendous increase in the yield per acre of traditional food crops. It is unclear, however, how these efficiencies are to be achieved.
(continued)
Many of the Biomass energy techniques are still experimental and have not been tested in commercial conditions. A significant number of technical barriers still exist: (continued)
Cellulosic biofuels: Key to the expansion of the biofuels industry is the converting of cellulosic plant matter into fuel. These processes are still experimental and it is unclear if they will provide an economically viable method of fuel production.
(continued)
Many of the Biomass energy techniques are still experimental and have not been tested in commercial conditions. A significant number of technical barriers still exist: (continued)
Refining efficiencies. The refining of fossil fuels is a mature and relatively efficient industry. Biofuel refining technologies will need to be improved if they are to compete.
(continued)
Many of the Biomass energy techniques are still experimental and have not been tested in commercial conditions. A significant number of technical barriers still exist: (continued)
Distribution infrastructure. It remains unclear whether the existing fuel infrastructure can simply be modified to accept biofuels, or if there will be the need for significant investment in a new infrastructure to support an emerging biofuel supply chain. The answer to this question will greatly impact the cost and availability of biofuels in the short term.
WARNINGWARNING
THE WOOD GAS PRODUCTION PROCESS PRODUCES CARBON MONOXIDE WHICH CAN BE FATAL IF INHALED.
A wood generator to produce gas from solid fuels.
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A filter to remove soot and ash from the gas.22
A cooling unit to condense tars and other impurities from the gas.
33
A valve to mix the resulting wood gas with air, and then direct this mixture into the engine’s intake manifold.
44
Today, wood gas generator systems typically incorporate four main components:
Figure 4-17: Imbert Wood Gas Production System
There are three main designs for wood gas generators, differing primarily on the relative positions of the air inlet and the gas outlet (although many variations to these basic designs exist).
Updraft generators
Downdraft generators
Cross-draft generators
Figure 4-18: Updraft Wood Gas Generator
The advantages of updraft generators include:
Ease of use: This design is perhaps the simplest to construct and operate.
High efficiency: Higher internal heat leads to a more efficient burn process and results in a cooler gas leaving the unit.
Flexible: Many types of biomass can be used with this unit.
The disadvantages of updraft generators include:
Channeling: The top-feeding of biomass can lead to the flow of fuel to the burning grate being disrupted when some of the material forms a bridge (or blockage). This results in very high operating temperatures that can lead to explosion. For this reason this design requires an agitator or some other method to shake the material to ensure it flows smoothly to the burn area.
Figure 4-19: Downdraft Wood Gas Generator
The advantages of downdraft generators include:
Cleaner fuel: This design results in a wood gas that contains less impurities. This in turn releases fewer potentially damaging chemicals into the atmosphere.
The disadvantages of downdraft generators include:
More ash: While producing a cleaner gas, downdraft generators produce more waste ash that must be removed from the unit.
Limited fuel sources: This design does not work well with lighter density biomass. Typically fuels must be pelletized when used with this type of wood gas generator.
Figure 4-20: Cross-Draft Wood Gas Generator
The advantages of cross-draft generators include:
Small Scale: This design is very flexible for small applications.
The disadvantages of cross-draft generators include:
No Wood: This type of generator requires a dry, low tar fuel source such as charcoal. Wood and many other biomass sources are not suitable for this design.
There are significant limitations to the wood gas system when compared with fossil fuels or other biofuel sources:
Less power: Compared with natural gas, wood gas contains only about 1/7th the energy by volume (150 Btu/cubic foot versus 1,000 Btu/cubic feet).
Larger storage space: Given its lower energy content, wood gas requires seven times the storage capacity for the same amount of energy supplied by natural gas.
(continued)
There are significant limitations to the wood gas system when compared with fossil fuels or other biofuel sources: (continued)
Weight: When incorporated in a vehicle, the considerable weight of a wood gas generator (and wood fuel) will dramatically reduce the performance of the vehicle.
Refueling: It takes about 20 minutes to refuel the generator (adding biomass, cleaning ash, etc). Typically vehicles powered by wood gas must be refueled every 125 miles (200 kilometers) or so.
The use of wood gas generators poses a number of health and safety concerns. These include:
Toxic Hazards
Fire Hazards
Risk of Explosion
Figure 4-21: Early Pot Still
Figure 4-22: Condensation Points within a Still’s Column
Figure 4-23: Reflux Still
The major parts of the reflux still system include:
The Boiler: Basically a stainless steel tank (stainless steel will not corrode and does not add impurities to the process) in which the fermented mash (a mixture of grain or sugar, water and yeast) is placed. This mash is then boiled, beginning the distillation process.
(continued)
The major parts of the reflux still system include: (continued)
The Column: Typically columns for small reflux stills are constructed using copper tubing. They are typically 2 – 4 feet in length (590 – 1200 mm). To increase the surface area upon which the vapors can condense, these columns are typically filled with small heat-resistant items such as marbles, glass beads or hollow ceramic cylinders (such as a product called Raschig Rings). At the top of the column, a small hole is drilled and a thermometer attached so that temperature readings can be monitored at the point furthest from the boiler.
(continued)
The major parts of the reflux still system include: (continued)
The Cooling System: Early pot stills utilized a coil of tubing to air-cool the vapors. Most reflux stills incorporate a water-cooling system to assist in lowering the temperatures within the column. A simple cooling system circulates water around a tube, lowering the temperature to the point where ethanol vapor condenses into liquid ethanol, as shown in Figure 4-24.
Figure 4-24: Cooling Tube
Fermentation is a series of anaerobic (without oxygen gas present) processes that break down sugar (glucose) into alcohol and carbon dioxide. The resulting chemical equation(in very basic terms):
CC66HH1212OO66 2 CH 2 CH33CHCH22OH + 2 COOH + 2 CO22
(glucose)(glucose) (alcohol)(alcohol) (carbon dioxide)(carbon dioxide)
In commercial ethanol production facilities, the process of unlocking the sugars from the grain is done in one of two ways:
Dry Milling: This process is the least expensive and produces higher yields of ethanol, but the value of the byproducts is considerably less. In this process, the grain is cleaned and ground into a powder. It is then mixed with water, cooked (with added enzymes), fermented and then distilled.
(continued)
In commercial ethanol production facilities, the process of unlocking the sugars from the grain is done in one of two ways: (continued)
Wet Milling: The wet milling process is more elaborate and expensive so the grain must be separated into its component pieces before undergoing fermentation. The grain is heated (for 24-48 hours) in a solution of water and sulfur dioxide to loosen the husk and the germ. The germ is then removed from the kernel and oil is removed. The germ meal is then added to the husk fibers to create a high-protein animal feed. Only the starch portion of the grain is subjected to fermentation. The oil and animal feed byproducts can add considerably to the profitability of the production facility.
The distillation of ethanol creates a number of potential safety hazards:
Explosion: Alcohol vapors are combustible and can explode if they leak from the still and come in contact with an open flame or spark. The still apparatus should be tested for leaks and should always be operated in a well-vented location. Electric (rather than gas) heat is often incorporated into these systems to avoid the potential of escaping gas coming in contact with an open flame.
(continued)
The distillation of ethanol creates a number of potential safety hazards: (continued)
Fire: There is always a risk of fire when working with heat and combustible materials. Alcohol vapor as well as liquid ethanol will burn if spilled. Extreme caution should be exercised.
Implosion: The distilling process takes place under heat in a sealed container. Once the process is complete and the apparatus is allowed to cool, a vacuum may develop if air is not allowed to enter the still (contracting air within the system may implode the boiling tank as illustrated in Figure 4-25 as it cools).
Figure 4-25: An Imploding Still
In the making of biodiesel, three products are used. These include:
Vegetable oil or animal fats (petroleum products such as used motor oil cannot be used)
A catalyst (sodium hydroxide, also known as lye)
Methanol
Heat the oil. If using used oil, it should be heated to at least 240°F (116°C) to boil off any water that might be present. Then let it cool to about 130°F (54°C). If new oil is used, preheat the oil to 130°F (54°C).
11
Creating biodiesel is a fairly simple process. Steps include:
(continued)
Mix the NaOH with the Methanol (creating methoxide) in a sealed container and allow it to mix thoroughly. This is an exothermic reaction, so the mixture will generate heat as the NaOH dissolves. The mix can be agitated (shaken or stirred - speeding up the process). It may take as little as 30 minutes or as much as 12 hours for the NaOH to completely dissolve.
22
Creating biodiesel is a fairly simple process. Steps include: (continued)
(continued)
Once the NaOH is completely dissolved, carefully add the methoxide mix to the preheated vegetable oil. These should be mixed in a sealed container.
33
Creating biodiesel is a fairly simple process. Steps include: (continued)
SAFETY WARNINGSAFETY WARNING
DO NOT BREATHE METHANOL OR METHOXIDE FUMES. THEY ARE DANGEROUS AND CARTRIDGE RESPIRATORS WILL NOT BLOCK METHANOL VAPORS.
SAFETY WARNINGSAFETY WARNING
AVOID METHOXIDE SPILLS. THIS MIX IS EXTREMELY CAUSTIC TO SKIN AND SURFACES.
Shake or agitate the mixture for about 60 seconds.
After about 10 minutes, the mixture will begin to separate into two distinct layers. The bottom layer will be a dark liquid comprised of glycerine (actually at this point it is about 50% pure glycerine, 40 % methanol and about 10% soap and catalyst) and a lighter top layer (about 80% of the mix) of biodiesel. Let the mix settle completely for 12-24 hours.
Creating biodiesel is a fairly simple process. Steps include: (continued)
(continued)
The biodiesel can now be decanted from the mix (or the glycerine drained away from the bottom).
44
Creating biodiesel is a fairly simple process. Steps include: (continued)
(continued)
The biodiesel at this point will still contain some glycerine, so the fuel will need to be washed. This is done by mixing the biodiesel with about half its volume of warm water (one gallon of biodiesel is mixed with one-half gallon of water). After mixing, the water will quickly settle out, pulling glycerine with it (during the first wash, the water will appear milky in color). This process is repeated 3-5 times, each time resulting in a more “pure” biodiesel fuel.
55
Creating biodiesel is a fairly simple process. Steps include: (continued)
(continued)
Finally the biodiesel will need to “dry”. Venting the mix will allow any remaining water to evaporate from the mix. When the fuel is translucent (no longer cloudy), it is ready to be used in any diesel engine.
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Creating biodiesel is a fairly simple process. Steps include: (continued)
Figure 4-26: Commercial Cone Bottom Biodiesel Processor
The methanol-ladened glycerine can be:
Taken to a large biodiesel facility where they will (hopefully) dispose of it for a fee.
Taken to a company that specializes in biodiesel waste disposal.
Taken to a toxic waste dump facility.
Converted to methane in a biodigestor.
Mixed with 50% kerosene and used as a solvent (makes a great engine cleaner).
Throughout the production of biodiesel process there are hazards that must be understood and avoided. These include:
Caustic Chemicals: The chemicals used as catalyst (either lye or potassium oxide-KOH) within the reaction are extremely caustic, meaning they will burn skin and damage any material they come in contact with. Protective gloves and eye wear should be worn when working with these chemicals.
(continued)
Throughout the production of biodiesel process there are hazards that must be understood and avoided. These include: (continued)
Methanol: Methanol is also caustic in additional to being flammable. While it is safer to handle than gasoline (according to the U.S. Environmental Protection Agency) it can still ignite and its vapors can explode if they come in contact with an open flame or spark. It is also poisonous if consumed. Again, safety equipment should be worn and biodiesel manufacturing should take place in a well-ventilated area away from ignition sources. Methanol should be stored outdoors in sealed and approved containers.
(continued)
Throughout the production of biodiesel process there are hazards that must be understood and avoided. These include: (continued)
Spontaneous Combustion: Rags and other materials often become soaked in biodiesel (or the materials used to create biodiesel). These can spontaneously combust and should be stored in an approved and sealed container.
REVIEW QUESTIONSREVIEW QUESTIONS
How does biofuel differ from biomass?11
REVIEW QUESTIONSREVIEW QUESTIONS
How does the modification of land use affect the carbon cycle?
22
REVIEW QUESTIONSREVIEW QUESTIONS
List three advantages and three disadvantages of utilizing biomass as an energy source.
33
REVIEW QUESTIONSREVIEW QUESTIONS
List four sources of biomass and the advantages and disadvantages of each source.
44
REVIEW QUESTIONSREVIEW QUESTIONS
Define the three major ways that biomass is converted into energy.
55
REVIEW QUESTIONSREVIEW QUESTIONS
Explain two advantages of co-firing biomass in traditional fossil fuel electrical generating plants.
66
REVIEW QUESTIONSREVIEW QUESTIONS
Cite three advantages and three disadvantages of ethanol as a fuel source.
77
REVIEW QUESTIONSREVIEW QUESTIONS
Why have advocates of biofuels pinned a great deal of hope on the future of cellulosic ethanol as compared with ethanol produced from grain-based sources?
88
REVIEW QUESTIONSREVIEW QUESTIONS
Discuss the controversy surrounding the energy required to produce ethanol and why it is important to the future of ethanol production.
99
REVIEW QUESTIONSREVIEW QUESTIONS
Explain the difference between distillation and transesterification and which biofuels are created using each process.
1010
REVIEW QUESTIONSREVIEW QUESTIONS
List the limiting constraints (economic, technical, infrastructure and resource) on the expansion of biofuel as an energy source and suggest how these constraints may be overcome.
1111
REVIEW QUESTIONSREVIEW QUESTIONS
When has the historic use of wood gas generators been widespread and why?
1212
REVIEW QUESTIONSREVIEW QUESTIONS
Discuss how the process of fermentation takes place in grain and why it is important in the manufacture of ethanol.
1313
REVIEW QUESTIONSREVIEW QUESTIONS
What waste products are created in the manufacture of biodiesel and how are they best disposed of?
1414
REVIEW QUESTIONSREVIEW QUESTIONS
What are the legal requirements involved in small-scale production of ethanol and biodiesel?
1515
EXAM QUESTIONSEXAM QUESTIONS
An advantage of using biomass as an energy source is:
a. it prevents soil erosion.b. it allows farmers to produce fuel rather than food.c. it promotes biodiversity.d. it is non-toxic and biodegradable.
11
EXAM QUESTIONSEXAM QUESTIONS
Currently the U.S. obtains what percent of its energy from biomass sources?
a. less than 1%b. about 3%c. just under 12%d. more than 25%
22
EXAM QUESTIONSEXAM QUESTIONS
Which of the following groups would likely push hardest to support legislation supportive of biomass as an energy source?
a. The Farm Bureau b. The American Petroleum Institutec. The American Association of Retired Personsd. The Rainforest Solutions Project
33
EXAM QUESTIONSEXAM QUESTIONS
Which of the following is NOT a potential source for energy from biomass?
a. algaeb. garbagec. grassd. beef
44
EXAM QUESTIONSEXAM QUESTIONS
Converting wood to charcoal is an example of:
a. Pyrolysisb. Biodigestionc. Co-Firingd. Gasification
55
EXAM QUESTIONSEXAM QUESTIONS
Which of the following is NOT an advantage of using biodiesel to fuel vehicles?
a. Most newer diesel engines require no modifications to run on biodiesel.b. Biodiesel burns cleaner than regular diesel fuel.c. Biodiesel smells better than regular diesel fuel.d. Biodiesel contains more energy than regular diesel fuel.
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EXAM QUESTIONSEXAM QUESTIONS
When air passes over a glowing bed of embers in a wood gas engine, the following gases are produced which can then be burned in an internal combustion engine:
a. Oxygen and Methaneb. Methane and Heliumc. Methane and Hydrogend. Hydrogen and Carbon Monoxide
77
EXAM QUESTIONSEXAM QUESTIONS
During the fermentation process, which of the following is necessary to convert glucose to carbon dioxide and alcohol?
a. temperatures in excess of 77°F/25°Cb. yeastc. oxygend. a reflux still
88
EXAM QUESTIONSEXAM QUESTIONS
The process involved in creating biodiesel is known as:
a. distillationb. triglyceridec. transesterificationd. biodigestion
99
EXAM QUESTIONSEXAM QUESTIONS
Which of the following is NOT a by-product of creating biodiesel from vegetable oils?
a. methanolb. glycerinec. ethanold. wash-water
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