Plants as Sources of Energy

Through the process of photosynthesis, plants have the capacity to capture and utilize energy, derived from the Sun, along with carbon from the Earth’s atmosphere and nutrients from our soils to generate biomass. This biomass, in the form of roots, stems, leaves, fruits and seeds, is also consumed by animals and microorganisms, which in turn, generate their own forms of biomass. Manure, leaf litter, wood, garden waste, and crop residues are all common examples of biomass. Consequently, one definition of biomass is any organic/biological material which contains stored sunlight in the form of chemical energy.

Bioenergy is energy made available from organic materials and is often used as a synonym to biofuel. However, an important distinction between bioenergy and biofuel is that biomass is the fuel/biofuel and bioenergy is the energy contained in that fuel. Biofuel can be broadly defined as any solid, liquid, or gas fuel derived from recently dead organic/biological material. This distinguishes it from fossil fuels such as coal, oil, and natural gas, which are derived from long dead, subterranean deposits of biological material. Unlike fossil fuel resources, which have an inevitable finite supply, biofuels are largely renewable energy sources based on a balance within the Earth’s carbon cycle.

Agriculturally produced biomass fuels, such as biodiesel, bioethanol, and bagasse (often a by- product of sugarcane cultivation) can be burned in internal combustion engines and cooking stoves. However, there are many criticisms and concerns surrounding current practices for the production of biofuels. This chapter examines some of the pros and cons in the current methods used for generating various types of bioenergy, namely, energy derived from solid biomass, bioalcohol, biodiesel, biogas, and presents a critical look at how biotechnology can help to solve the world’s current and future energy needs.

Energy Crisis and the Balance of Carbon Biofuels were the first form of fuel used by human cultures around the world. Even up to the discovery of electricity and the start of the industrial revolution, fuels such as wood, whale oil, manure, and even alcohol were the primary sources of energy for heating, cooking, and lighting. However, the discovery and use of fossil fuels, including coal, oil, and natural gas dramatically reduced the emphasis on biomass fuel in the developed world (Peters and Thielmann, 2008). In the United States, for example, large supplies of crude oil were discovered in Pennsylvania and Texas in the mid- and late 1800s. This allowed petroleum-based fuels to become inexpensive. Because of these low costs, fossil fuels were widely used to promote the growing industrial age, especially for the production of power used to run factories and automobiles. Despite the huge increase in the use of fossil fuels, most of the world continued to depend upon and make use of biofuels. Even in the United States, during the highenergy demand seen during wartime periods of World War II, biofuels were valued as a strategic alternative to imported oil. However, during the peacetime postwar period, inexpensive oil from the Middle East helped to trigger a worldwide shift away from biofuels. Since then, there have been a number of “energy crises” around

the world, caused by a variety of social and political factors. An energy crisisis any large-scale bottleneck (including price rises) in the supply of energy resources to an economy. Two of the best known ones occurred in 1973 and 1979, when geopolitical conflicts in the Middle East caused OPEC (Organization of Petroleum Exporting Countries) to cut exports. Consequently, non-OPEC nations experienced a very large decrease in their oil supply. This crisis resulted in severe shortages and a sharp increase in the prices of high-demand oil-based products, most notably gasoline. Throughout history, the fluctuations of supply and demand, energy policy, military conflict, and environmental impacts have all contributed to a highly complex and volatile market for energy and fuel. On the other hand, such problems always resurrect the principles of green energy and sustainable living. This has led to an increasing interest in alternate power/fuel research such as bioethanol, biodiesel, biogas, fuel cell technology, hydrogen fuel, solar/photovoltaic energy, geothermal energy, tidal energy, wave power, wind energy, and fusion power. Heretofore, only hydroelectricity and nuclear power have been significant alternatives to fossil fuels, which still dominate as energy sources (Fig. 9.1).

Although technology has made oil extraction more efficient, the world is having to struggle to provide oil by using increasingly costly and less productive methods, such as deep sea drilling and developing environmentally sensitive areas such as the Arctic National Wildlife Refuge. In addition, the world’s population continues to grow at a rate of ∼ 250,000 people/day, and while a small part of the world’s population consumes most of the resources, the people of developing nations continue to

Estimated world energy use from different sources