With global climate change, some researchers are exploring sources other than petroleum for fuel. Organic matter is one such source. Materials like corn and soybeans have oil extracts that can be converted to ethanol or biodiesel. These and many other organic materials are more sustainable than petroleum, meaning they can be regrown and remain productive with less negative impact on our ecosystem. With the different types of biofuels at varying stages of research, it is important to remember that no two biofuels are created equally. Troy Runge, director of the Wisconsin Bioenergy Initiative, explained that every source has its pros and cons. Some biofuels that provide more long-term benefits may prove too expensive to pursue. Others already in production might not have the potential to fulfill our energy needs by themselves. "I think they all should be investigated," Runge said. "We don’t want to make decisions to eliminate a technology or feedstock too early because we might be discarding something that, with just a few more years of research, could really be good." Difficulties like competition for land, high costs of processing and developing technologies have slowed some resources from finding a place in the market, as well. Ranking these different possibilities depends on a variety of aspects such as economic factors, how well developed the technology to produce the fuel is, the amount of material that could be used, and several other factors, according to Runge. The 10 sources for biofuels listed here all have potential, and when used in combination could go a long way toward meeting our energy needs in the coming decades.
Runge estimated that in the United States alone, some 1.3 billion tons of cellulose material could be harvested for biofuel use. Cellulose is basically fiber, and can be found in things ranging from switchgrass to trees such as hybrid poplar and willow. Even materials from other industries, like corn stalks after harvest, could be used for cellulose fuel. While there is some debate over devoting land to growing crops specifically for fuel, the sheer volume of cellulosic material still makes it a tremendous source for biofuel. With so much material to work with, why isn’t cellulose biofuel flooding the market? To use cellulose as a fuel, it must be broken down into sugar. This may not seem like much of a problem, but Runge explained cellulose is engineered specifically to prevent this process. “If you think about it, nature -- the trees and the grass -- they were built to withstand microbial attacks that want to take it down to sugar so they can eat it,” Runge said. “Nature’s got all kinds of defense mechanisms to make sure that doesn’t happen.” There are currently no commercial producers of cellulosic fuel, but Mark Knaebe and his fellow technologists at the U.S. Forest Products Laboratory in Madison, WI, are attempting to develop the technology. Because cellulose is so abundant, can be continuously regrown and harvested, and is one of the cleanest burning materials, Runge rated it the number one fuel, despite this slight lag in technology.
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2. Algal Oil
Because algae are grown in water, they overcome one of the major problems faced by other biofuels -- competition for land with agricultural crops. Some common forms of algae are seaweed and pond scum, which aren’t true plants but do perform photosynthesis. Algae can store up to 50 percent of their body weight in fat, just waiting to be rendered into oil for ethanol production. They also grow amazingly fast, so it’s a crop that could meet high demands for energy over the long term. However, their productivity can be algae’s own worst enemy. The algae can grow so fast, they overcrowd each other. This blocks light and doesn’t allow the algae to perform photosynthesis, causing massive die-offs. There are currently no commercial producers of algal oil because no technology has been able to control and maintain the algae growth. “When you are growing them, they can grow so fast they kind of out compete themselves,” Runge explained. “There’s huge potential. If you look at how fast you can grow these and the amount of oil you can get, it’s just a matter of getting the process down.” This potential is what brings algae in at number two on our list.
The biggest biofuel in the United States right now, corn sometimes gets a bad wrap. Corn ethanol is more sustainable than petroleum, but it has been a centerpiece for debates on using agricultural crops for fuel. It’s true that corn used for fuel is corn that could have been someone’s dinner, but Runge explained that even once the corn oil has been extracted for ethanol, there is still a byproduct of distiller corn that can be fed to animals. “It is taking food and putting it into fuel, but there is a byproduct of doing that that still can go to animals. It’s not one to one, but it’s not all bad,” Runge said. Even given the possible by-products it seems that corn is, at best, a short-term solution. Much like sugar cane, corn is one of the best options we have available now, but because the process is expensive and has high energy consumption rates, Runge felt it should be high on the list, but may fade from use over time.
Soy has been a popular biofuel for several years now. In a process called trans-sterification, producers squeeze the oil from seeds and use it in products such as biodiesel and jet fuel. It is a relatively easy and inexpensive rendering process, according to Runge. “You could make it in a bathtub if you really wanted to,” Runge said. “I don’t encourage it because there’s methanol involved and methanol can make you blind. But it’s very easy to do.” As is the case with many agricultural crops, there is debate over the extent to which soy could be utilized. Crops like soybeans are dietary staples to many people, and researchers are reluctant to rely too heavily on traditional food crops as fuel sources. The seed oil that goes in a gas tank could have gone to someone’s stomach, and it may prove difficult to say one destination is more valuable than the other. While soy is used widely, it is not as popular as corn or sugar cane, nor does it have the amount of resources that cellulose or algae provide. This makes it a short-term solution that deserves attention, but not a higher spot on the list.
5. Sugar Cane
In the world of biofuel production today, sugar cane is second to corn as the most widely used, but Runge said this is likely to change in the coming decade. Sugar cane grows in warm parts of the world in abundance, and has helped countries like Brazil to become energy independent. Sugar cane ethanol isn’t the easiest on a car’s internal workings as it can gum up the engines of older cars, but with flex-fuel cars and gasoline blends varying from 20 percent ethanol all the way to 100 percent ethanol, Brazil shows it can work. Sugar cane uses more of the plant than seed-based fuels like corn and soy, but it still does not utilize all of the plant. Also, because it can only be grown in the tropics, there are limits to how much sugar cane can be grown. Still, because sugar cane is a developed technology that is already in wide spread use, it earns a higher place on the list.
6. Camelina and Jatropha
Camelina and Jatropha are both plant-based fuel sources that are found all over the world and are the up and comers for the biofuel revolution, according to Runge. These flowering plants have an advantage over other seed-based fuels like soy because they can be grown in very dry areas. Thus, they aren’t diverting land that could be used for agriculture in the way soybeans are, and can be grown in a wider variety of places. While Jatropha has the added benefit of making even poor soil more fertile over time, Peter Taglia, a scientist with the renewable energy advocacy group Clean Wisconsin, still had some doubts about it and other feedstock fuels. If a fuel is successful, Taglia thinks it could expand beyond marginal land use, and this could create new problems. “If used on more fertile lands, and either displacing food crops or native ecosystems we are, perhaps, creating additional problems in our search to replace petroleum,” Taglia said. Camelina and Jatropha both offer a lot of options that other feedstocks don’t provide, but much of their potential has gone unrealized, leaving them in the middle of this biofuel countdown.
Better known as canola oil, rapeseed oil is rendered from a plant found commonly throughout Canada and the United States. Similar to soy, it is cheap and easy to produce and burns far cleaner than petroleum, making it a seemingly quick fix to energy problems. While easy and cheap, the question remains whether enough could be produced to properly address our needs. Rapeseed will have to compete for land like many other biofuels, and in order to produce a significant amount of fuel; the plant would need a lot of acres. “It makes sense for special products like biodiesel and jet fuel,” Runge said. “But it’s hard to imagine we’re going to have fleets and fleets of canola, that we’re going to the fuel the nation.”
In Stockholm, Sweden, an entire fleet of busses is already running on the natural gas methane, and the resource has been gaining popularity as a biofuel in recent months. Microorganisms decomposing organic matter like food, compost and other landfill materials create methane, so it is already being produced in dumps around the world. The gas also burns cleaner than many of the fuels in use now, according to Mark Knaebe, a forest products technologist with the U.S. Forest Products Laboratory in Madison, Wisc. While methane is being implemented as vehicle fuel in Europe and some U.S. cities like San Francisco and Washington D.C., most car designs would have to undergo major changes to utilize the fuel. Because of the effort required to adapt cars and gas stations to handle methane, Knaebe didn’t think methane would ever gain wide acceptance as a fuel in America. “It requires quite a bit of additional infrastructure,” Knaebe said. “It could work in large fleets like taxis and busses, where you’ve only got a few ports, but I don’t think it will make it to public use.” Because of the technological complications that have proved to be less of a problem for sources like sugar cane and corn, combined with the huge financial costs of developing methane-friendly engines and gas stations, methane is considered a possible solution, but not one of the best.
9. Animal Fat
Pigs, chickens, and cows -- all are fairly common in everyday life, but they could have uncommon potential for biofuel. Leftover fat from animal food products can be rendered into oil and then used as a fuel for cars and trucks. It may seem like an odd source, but Taglia believes the benefits of animal fat are large. “Any time you can use something that was either going to a landfill or was going to be
, and that’s not necessarily the best use of it, then that’s something we really want to be used efficiently to produce fuel,” Taglia said. But gathering fat isn’t as easy as picking it up from the landfill or your local fast food restaurant. Animal fat is used in many industrial products, so there would be competition for resources. This combined with the natural limit on the resource means animal fat could never displace petroleum by itself, Taglia said, and this placesk animal fat low of the list of biofuels.
10. Paper Waste
Recycled paper, paper sludge from production and even sawdust from the early processing stages of paper have all been examined as possible sources of biofuel. While producers would have to compete with paper companies -- who use the waste in their own recycling programs --researchers believe that some waste could be diverted for fuel production. However, many of these materials might be more trouble than they are worth. Knaebe explained that paper is difficult to convert to liquid fuel because of its waxy coating and how the paper is made. “Have you ever tried to light up a newspaper?” Knaebe asked. “It will burn but then goes out right away because of the form of the paper. It’s a complex system; it’s a lot harder [to burn] than wood or corn stalks.” Paper waste rounds out the bottom of the countdown because it’s a source that is already being widely used for products other than biofuel. Combined with the fact that it is difficult to process and somewhat expensive makes this biofuel a limited opportunity.