1
What are biofuels, and what are potential biofuel sources?
INFOGRAPHICS 32.1 AND 32.2
True or False: Direct sources of biomass energy include wood, corn stalks, grass bales, and dried manure.
TRUE
Which of the following best describes a fuel crop?
A crop that is specifically grown to make biofuels
Waste biomass from food crops that is converted to fuel
Waste oil from restaurants used to make biodiesel
Manure patties remaining in a field grazed by herbivores
A
Describe the process of biodiesel production using leftover restaurant oil. Is this possible on a small scale?
The oil is collected from restaurants (saving the restaurants money because they don’t have to pay for waste disposal). It is then filtered to remove water and impurities (that came from the food being cooked) and mixed with a strong base and methanol. This produces biodiesel and glycerin, which are separated. The glycerin is purified, resulting in the recovery of methanol, which is then used again in the process. Glycerin can then be sold for a variety of purposes (for example, it is often an ingredient in soap). The biodiesel is “washed” several times with water to remove impurities and can then be used in a vehicle; the water is reused. This process can be done on a local scale and by private individuals.
What are the advantages of using indirect biomass energy rather than using the biomass material as a direct biomass energy source?
Indirect biomass energy sources are more energy rich and less bulky than the feedstocks that created them — they are essentially concentrated energy forms of the biomass material. These indirect sources may also burn more cleanly, are more portable, and are suitable for internal combustion machines (such as vehicles).
2
What are the trade-offs of using biofuels as an energy source?
TABLE 32.1
True or False: One of the main drawbacks to biofuels is the use of prime farmland to grow fuel crops instead of food crops.
TRUE
Which of the following NOT an advantage of biofuels?
They are versatile and can be used in a variety of ways.
They can be produced locally.
They do not produce pollution when burned.
They can be made from waste material.
C
Describe the environmental issues associated with biofuels. Include issues specifically related to the use of corn.
Corn requires a lot of energy input to grow, including pesticides and fertilizer made from fossil fuels. Pesticides can damage unintended targets, including humans and excess fertilizer is a significant source of pollution, especially if it leaches into aquatic systems. The growth and production processes also require a lot of water. In some places, natural lands are being converted to farmland specifically for the production of crops to make biofuels, threatening biodiversity. Biofuel crops also take up space that could be used to grow food. Clearing land to grow these crops releases more CO2 into the atmosphere, exacerbating the problem of global climate change.
3
How might cellulosic crops or algae address some of the trade-offs of biofuels?
INFOGRAPHICS 32.3 AND 32.4
What is an LIHD biofuel?
Biofuel with a high-density-lipid content
Biofuel produced from waste oil, which has a low impact on the environment
Biofuel produced from algae grown in high density in fertilizer-rich liquid
Biofuel produced from grasslands with high species diversity grown with few inputs
D
Which of the following produces the most oil per acre of crop?
Soybeans
Algae
Sunflowers
Oil palms
B
Compared to gasoline, which of the following produces the smallest amount of greenhouse gases?
Corn grain ethanol
Soybean biodiesel
LIHD biodiesel
LIHD ethanol
C
You are an investor looking to get into the biofuels market, and you plan to choose one source for generating biofuel. Based on the information in this chapter, which source would you choose and why?
Answers may vary but based on the information in the chapter, algae provides the most fuel with the fewest costs. The technology is still being worked out; currently we can’t do this on a large scale. A substantial benefit is that the algae can be grown in salt water, reducing the need for large amounts of fresh water. It is fast-growing, and the fuel contains no sulfur, is non-toxic, and biodegradable. Research and development is also making cellulosic ethanol a more viable option. More development is needed to improve the enzymatic breakdown of cellulose to improve net energy output but this source has the advantage of being able to be grown and produced just about anywhere, making it a truly local biofuel that may be more suitable for lower income areas or areas that do not have the water resources needed for algae.
4
How is bioethanol made, and what are the challenges of making it from cellulose?
INFOGRAPHIC 32.5
Bioethanol is made when ______________ ferment sugars.
bacteria
enzymes
yeast
cellulosic plants
C
Which type of plant material is the hardest to convert to bioethanol?
Corn
Switchgrass
Sugar cane
All of the above are easily converted to bioethanol.
B
Compare and contrast corn and switchgrass as sources of biofuels in terms of the costs and benefits of each.
Corn is an energy and water intensive plant to grow. We also use it as a source of food both directly and indirectly (for our livestock) so many see a conflict of interest between growing corn for fuel and growing it for food. However, the process of producing biofuel from corn is relatively straightforward. Switchgrass has the benefits of being a native plant. It requires little in the way of water and fertilizer, can be grown on marginal soils or poor agricultural lands, and when grown in polycultures, produces a significant amount of biomass (more than corn). It also sequesters carbon, which could help reduce overall greenhouse gases. Producing biofuel from switchgrass is a more involved process than used in corn because it requires the breakdown of cellulose, currently an inefficient process and one that has not been easy to scale up.
Explain, in your own words, why biofuels (especially cellulose and algae) have not replaced fossil fuels.
Biofuels have not replaced fossil fuels for several reasons, including energy efficiency, using food as a source of fuel, and a lack of infrastructure to support the industry. For cellulose, we are still not quite there in terms of being able to make the fuel efficiently. The process is slow and energy intensive, and we have not been able to do it on a large scale, which will be necessary if it is to replace fossil fuels. For algae, we do not yet have the infrastructure required to grow enough algae fast enough to meet fuel demands.
5
What roles do conservation and energy efficiency play in addressing our mobile fuel needs, and what are some ways we can pursue these?
INFOGRAPHIC 32.6
True or False: Using cruise control generally decreases fuel efficiency, so you should not use it if you want to maximize your miles per gallon.
FALSE
At what speed do most cars get the best fuel efficiency?
20–35 mph
40–50 mph
35–55 mph
55–70 mph
C
Identify four driving habits that can help the average driver increase the fuel efficiency of his or her car.
1) avoid jackrabbit starts; 2) drive between 35 and 55, as safety and speed limits allow to maximize fuel efficiency; 3) Use cruise control at highway speeds; 4) avoid idling — turn your car off if you will be parked for more than a few seconds.
32-21