Biofuels Glossary

Algaculture - A form of aquaculture involving the farming of species of algae. Some high-lipid forms of algae are thought to hold great promise as feedstock for biodiesel. Because algae grows quickly and densely, the yield per acre of energy is potentially an order of magnitude greater than the energy yielded by even the very best terrestrial crops. Better yet, the algae can be grown in wastewater. But, despite the promise, significant hurdles remain in reliably cultivating and harvesting large volumes of algae.

Bagasse – The leftover parts of the sugarcane plant that, today, are not directly used to produce ethanol. Bagasse is often burned as a heat source to brew and distill sugarcane ethanol and also to generate electricity. Ethanol plants that use agricultural waste as the heat and electricity source for the plant are said to practice CHP (combined heat and power). In cellulosic ethanol production, the bagasse can be used with the sugarcane as primary fuel feedstock.

Biodiesel – Biodiesel is renewable diesel fuel that can be derived from algae, vegetable oils (soy beans, sunflowers, peanuts, rapeseed, palm oil, jatropha etc.) and even old restaurant greases. Blends of 20 percent biodiesel with 80 percent petroleum diesel (B20) can generally be used in unmodified diesel engines. Biodiesel can also be used in its pure form (B100), but may require slight engine modifications to avoid maintenance and performance problems. Production from algae is particularly intriguing because the yields (the ultimate conversion of sunlight into useable energy) are an order of magnitude greater than for other feedstocks and the algae can grow in wastewater.

Biofuels – Biofuels are derived from biomass — recently living organisms or their metabolic byproducts. They are a renewable energy source, unlike other natural resources such as petroleum, coal, and nuclear fuels. Like coal and petroleum, biomass is a form of stored solar energy. The energy of the sun is captured through the process of photosynthesis in growing plants. Agricultural products specifically grown for use as biofuels include corn, soybeans, flaxseed, rapeseed, sugarcane, palm oil, jatropha and increasingly many other plants – energy crops such as switchgrass and miscanthus – that are being investigated for their relatively high, accessible sugar content. Biodegradable outputs from industry, agriculture, forestry and households can also be used; examples include straw, sawdust, manure, rice husks, sewage, and even tires and tennis shoes. Cellulosic ethanol production aims to produce ethanol from the "woody" parts of plants that are today viewed as waste (e.g., leftover corn stalks and cobs); or,from energy-dense, energy crops such as switchgrass and miscanthus. Ethanol, butanol, and biodiesel are the most commonly talked about biofuels.

Brazilian Miracle – After the 1973 oil crisis, Brazil undertook a crash program to become "energy independent" by making use of sugarcane ethanol. Today, it is estimated that more than 40% of the energy Brazil needs for transportation comes from ethanol. But for the petroleum needed to make plastics and fertilizers, Brazil would not import oil.

Butanol – Long produced from petroleum feedstocks, butanol can also be produced from biomass (corn, sugarcane, etc). It is formed by ABE (acetone, butanol, ethanol) fermentation a slightly different process than currently used to produce ethanol. Experimental modifications of the process show potentially high EROEI (energy returned on energy invested). Butanol has other potential advantages in that it may be more compatible with existing gasoline engines (so, no flex fuel vehicles required) and, butanol is less corrosive than ethanol meaning it can be distributed via existing pipelines. But, butanol is also more viscose (thicker) and can gel in cold weather. BP and Dupont have announced a big push into bio-butanol production and their efforts are being closely watched as most ethanol plants can be modified to produce butanol if the economics – including the field-wheel environmental externalities – warrant.

Carbon-neutral – When a fossil fuel is burned it releases carbon (as carbon dioxide - CO2) that was used by plants millions of years ago. This CO2 trapped (or, as scientists call it "fixed") by the ancient plants as part of photosynthesis is released when fossil fuels are burned and is added to the CO2 currently in the atmosphere. Humans have added a huge amount of "new" CO2 to Earth’s atmosphere by aggressively burning fossil fuels over the past 150 years. This CO2 is now widely understood to be the cause of global warming.

Biofuels are said to be "carbon-neutral" because the next crop of biofuel feedstock (corn, sugar, etc.) grown captures the same amount of CO2 from the prior crop of biofuel feedstock that was produced and burned as fuel.

If, however, a fossil fuel is used as the heat source to brew and distill a biofuel (as is commonly the case today), then unwanted "new" or incremental CO2 emissions creep into the picture. To be optimally "carbon-neutral," the entire biofuel production process must be considered: the heat used to brew and distill the biofuel should be derived from biomass like sugarcane bagasse or corn stover; the farm machinery used to plant, maintain and harvest the feedstock should be running on biofuels; the trains and/or trucks used to transport the feedstock to the plant and later to the end-users should be running on biofuels; and, even the fertilizer used to help grow the feedstock should be a bi-product of the biofuel production.

In a society where fossil fuels will still be used for decades to come, a truly carbon neutral position is hard to achieve, but smart biofuel processes can greatly reduce the amount of new CO2 entering our atmosphere and are humankind’s best available weapon to fight Global Warming.

Carbon sequestration – This refers to a set of technologies also referred to as carbon capture and storage (CCS) that, most often, pumps the CO2 released by an industrial plant (including, of course, biofuels plants) into a deep, well-sealed geological reservoir effectively preventing the CO2 from entering the atmosphere.

CHP - CHP or "combined heat and power" is also referred to as cogeneration. Ethanol plants that use agricultural waste (e.g., bagasse or corn stover) as the heat and electricity source for the plant are said to practice CHP.

Cellulosic Ethanol – Even the best agricultural feedstocks like sugarcane have much of their biomass’ potential energy locked up in the "woody" parts of the plant. The sugars in this part of the plant – the cellulose – are complex (known as polysaccharides) and are protected by an even tougher substance known as lignin. The fermentation organisms and process widely used today cannot convert the polysaccharides in cellulose to useable sugars. Several promising new cellulosic technologies are being tested and rapidly commercialized. By making uses of plant material once viewed as waste, EROEI (energy returned on energy invested) improves, food prices are not bid up and, carbon-neutral goals are advanced (limited new CO2 is released). Cellulosic technologies also catalyze the use of energy-dense, cellulose rich energy crops such as switchgrass and miscanthus.

Corn Ethanol – Corn ethanol is ethanol produced from corn. Unlike sugarcane where a relatively high percentage of the plant’s mass contains sugars that can readily be turned into fuel, today only the corn kernels can be converted into ethanol. The goal of cellulosic ethanol production is to use more of the biomass from corn – or, any number of feedstocks –to make fuel. Today, approximately 2.8 gallons of ethanol (10 liters) are produced from one bushel of corn (35 liters). So, the economics of ethanol production depend not only on the competitive price of petroleum, but also on the price of corn. Today, corn ethanol economics are improved by the fact that ethanol is exempted from 51-cents per gallon federal tax on gasoline until 2010. As corn is widely grown in North America, corn ethanol is the most commonly produced ethanol in the United States and it will make an important contribution to our alternative energy needs for decades to come. Among other things, critics of corn ethanol bemoan its EROEI (energy returned on energy invested) or net energy gain despite the fact that it is widely recognized to be 21% better than the same calculations for converting oil into gasoline. Corn ethanol producers are busily streamlining their processes to save water and reduce new CO2 emission by burning corn stover (leftover leaves, stalks and cobs) as the heat source to brew and distill the ethanol. The bi-products of corn ethanol production make excellent animal feed.

Corn stover – The leftover parts of the corn plant that, today, are not directly used to produce ethanol. A number of ethanol producers are planning to burn corn stover as a heat source to brew and distill corn ethanol and also to generate electricity. Ethanol plants that use agricultural waste as the heat and electricity source for the plant are said to practice CHP (combined heat and power). In cellulosic ethanol production, the corn stover can be used with the corn as primary fuel feedstock.

E85 – This is the fuel used by "flex fuel" cars that is comprised of 85% ethanol and 15% gasoline. Distribution for E85 is starting to appear in the U.S. Midwest and the production of flex fuel cars (that can run on really any combination of ethanol and gasoline) is being increased. The two biggest challenges in bringing E85 to market are: 1) securing distribution from service stations that are often owned by big oil companies; and, 2) increasing the number of vehicles that can run on E85. Without regulatory intervention and/or consumer incentives E85’s chicken-and-egg problem will be slow to resolve though, perhaps the most helpful development is gasoline in the $4 range.

Energy crops – This evolving term collective refers to plants that are grown primarily as feedstock for biofuels and are not, typically, used as food for humans or livestock. That said, some of the plants being termed as energy crops such as sorghum, flaxseed and rapeseed (canola) have long been cultivated and used by humans. Others such as miscanthus, hybrid poplar trees and switchgrass are relatively new to large-scale agriculture. And, others still are yet to be discovered in nature (providing more reasons than ever to value biodiversity).

Energy crops do not uniformly require cellulosic ethanol technologies to be useful. But, some of the more promising, energy-dense crops such as switchgrass, miscanthus and hybrid poplar trees do. These crops are high in cellulose (and so appear "grassy" or "woody"), but are low in lignin (the even woodier substance that makes many crops/plants impractical for use as biofuels feedstocks). And, of course, some energy crops such as jatropha and microalgae (e.g., Botryococcus braunii) are cultivated not to produce ethanol but biodiesel.

Many energy crops are drought-tolerant and/or are "nitrogen fixing" meaning that they are well suited for use in rotation with food crops that tend to deplete nitrogen and require heavy applications of fertilizers.

The term energy crops is really most useful when applied within the context of the criticism that biofuels trade food for fuel and threaten the world’s poor. In this way, energy crops are best understood as biofuels feedstocks that do not compete with food crops, often help food crops (nitrogen fixing); and, are not fertilizer, fresh water or land intensive (i.e., they produce lots of energy per acre tilled).

EROEI or Net Energy Gain – Energy Returned on Energy Invested or Net Energy Gain is a flavor of cost accounting applied to energy production that considers the "well-to-wheel" or in the case of biofuels, the "field-to-wheel" energy inputs required to produce and distribute fuels to end-users. So, for example, the energy inputs used to grow corn including the petroleum based fertilizers, the fuel used by the farm equipment, the fuel used to transport the corn to the ethanol plant, the heat required to brew and distill the ethanol and the energy required to transport the ethanol to market all come to bear in this accounting process. Many consumers are surprised to learn that many fuels – including oil from older fields or far away lands – often exhibit 1:1 or slightly negative net energy gains. In layman’s terms it takes a lot of calories – a lot of work – to produce and deliver the calories we use in our gas tanks. At a 1:1 ratio, it takes an equal mount of energy input to produce and distribute the energy that’s ultimately used (so, more simply still, at a 1:1 ratio it takes the energy in a gallon of gas to produce and distribute a gallon of gas). Today, using relatively inefficient processes, corn ethanol is widely thought to deliver between a 1:1 and a 1:1.2 net energy gain, making it on par or better than most oil. Recent developments in cellulosic ethanol stand to dramatically increase EROEI because using agricultural waste and energy crops improves energy density (the amount of energy that can be produced from an acre of land).

Ethanol – Ethanol is a type of alcohol used as a biofuel. It is also the type of alcohol found in alcoholic beverages,but ethanol used for fuel is denatured (meaning it has chemicals added to it). Interestingly, one reason the chemicals are added (often just scent) is so that ethanol is not taxed as an alcoholic beverage. Ethanol is made in a fermentation process where a feedstock like corn is metabolized by yeast in the absence of oxygen. (If oxygen is present, the fermentation yields vinegar instead of ethanol.) In order to produce ethanol from a starchy material such as corn, the starch must first be broken down into sugars. In the production of alcoholic beverages letting the feedstock grains slightly germinate or "malt" often accomplishes this. For fuel ethanol, the hydrolysis of starch into glucose is accomplished on a more industrial scale by treatment with dilute sulfuric acid, fungal amylase enzymes or other enzymatic processes. Most cars on the road today can run well on gasoline that is mixed with 10% ethanol. Flex fuel cars like those now common in Brazil and increasingly produced in the U.S. can run on any combination of gas and ethanol including 100% ethanol but commonly use a fuel called E-85 (85% ethanol, 15% gasoline). Pure ethanol delivers about 30% less energy per unit than gasoline.

Field-to-wheel – Field-to-wheel is biofuels’ take – and improvement – on oil’s well-to-wheel. Much like EROEI (energy returned on energy gained), field-to-wheel seeks to undertake a through accounting of the energy inputs required to produce biofuel. But, field-to-wheel has evolved beyond EROEI; it has become as much a guiding philosophy as it has a form of accounting. Field-to-wheel now casts an eye toward a variety of important externalities including some that do not explicitly drive costs. Field-to-wheel asks how much water is used? How much fertilizer is used? What types of pesticide are used? How much pesticide is used? What type of land is used? Is it land that is already tilled or is it fallow or unfarmed land that may have been wildlife habitat? Where does the run-off water from the land go? How much new C02 is released? Today, field-to-wheel embodies a set of principles associated with the smart, sustainable production of biofuels.

Flex fuel cars – Most cars sold in the U.S. today cannot run on fuel that is more than 10% ethanol. Flex fuel vehicles run on E85 or really any mixture of ethanol and gas including 100% ethanol. Auto manufactures throughout the world are increasing the production of flex fuel vehicles.

Lignin - Is a complex chemical in plants that makes their cell walls rigid and, much like bones in vertabrates or chitin in insects, helps give plants their structure. While lignin is an incredibly useful substance with many applications, it is undesirable in the production of biofuels because it cannot be economically broken down into simple sugars for fermentation. Energy crops such as switchgrass and miscathus are typically high in cellulose (a semi-rigid polysaccharide that is more readily converted into fermentable sugars) and relatively low in lignin.

Sugarcane ethanol – Sugarcane ethanol is ethanol produced from sugarcane as a feedstock. Sugarcane is an excellent feedstock because the biomass of the sugarcane plant is relatively rich in the sugar that can be readily turned into fuel. Brazil is the world’s leading producer of sugarcane ethanol and it is estimated that upward of 40% of Brazil’s transportation energy needs are met by sugar cane ethanol.

TDP – TDP or thermal depolymerization is yet another promising technology that breaks down complex yet fundamentally organic materials like old tires, sewage and plastic into light crude oil by mimicking the natural process that create hydrocarbons. EROEI (energy returned on energy invested) has steadily improved in this arena such that commercialization is now feasible.

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