BIOMASS AND BIOFUELS
The term “biofuel” can be used to include a fuels made from a variety of different processes. Sugar and starch plants can be fermented to produce ethanol. Lignocellulosic materials (such as the stalks of crops) can be converted to a variety of fuels (including methane, methanol, ethanol, diesel, and hydrogen) using several processes (gasification, anaerobic digestion, hydrolysis, and hydrothermal liquefication). Vegetable oil can be converted into biodeisel (IPCC, Document III, 2007).
CORN, SUGARCANE, AND GASOHOL
Biomass can be used as a source for the liquid biofuels ethanol, methanol, and biodiesel or the gaseous biofuels methane and hydrogen. Ethanol and methanol can be used in combustion engines and gasoline may have consist of 15-20% ethanol without degrading engine performance. A modified engine could run on 85% bioethanol. (Propanol and butanol can also be produced but cannot be used in internal combustion engines.) Gasohol and diesohol (gasoline and diesel mixed with ethanol) emit less pollution (including less particulate pollution from diesel) and improve engine performance (Demirbas, 2008).
Gasohol (gasoline which contains about 10-23% ethanol) represents 62%
Between 2000 and 2005, the global production of bioethanol increased from less than 5 billion gallons to more than 12 billion gallons. By 2008, the
Wheat, maize, sugar beets, and potatoes can also be grown to produce biofuel.
If fuel could be produced from the parts of plants which are not used for food, there would be no threat to global food supply by increased biofuel production. In 2006, a few cellulosic plants were planned in the
Vegetable oils from rapeseed, soy, sunflower, and palm can be produced for biodiesel which produces less pollution than conventional diesel. Other sources such as animal fat can also be used. A disadvantage is that it costs about twice the price of diesel to produce. Existing diesel engines do not need to be modified to use biodiesel (Demirbas, 2008). Pongamia pinnata can produce an oil to be used as biodiesel. This plant is not edible and it can grow over a wide range of temperatures, even in salt water (Sureshkumar, 2008).
Each ton of solid municipal waste has the same energy potential as a barrel of oil or a quarter ton of coal. As the waste is heated at high temperature, it combusts and is reduced to a tenth of its former volume. In the process, it converts water to steam. In addition to the energy produced and the reduction of garbage volume, this process has the advantage of not producing methane as a waste gas, as do typical landfills. Methane can absorb far more heat than carbon dioxide and an average landfill loses about half its methane to the atmosphere (Porter, 2008).
When biomass is allowed to ferment without the presence of oxygen, methane is produced which can be used for energy. The biomass which can be used for fuel includes sewage and animal dung (Demirbas, 2008).
Preliminary operations have already begun for the production of ethanol from municipal waste. Given the vast amounts of waste produced in
HYRDOGEN GAS FROM BIOMASS
Active research is investigating biological systems which produce hydrogen gas and produce electricity from foodstuffs or even sunlight. This biofuel cells can utilize a diversity of elements ranging from isolated enzymes to engineered microbes (
High temperatures can break biomolecules into smaller forms (known as pyrolysis or cracking). Various treatments of biomass can produce hydrogen gas or liquid fuels (known as Fisher-Tropsch or FT fuels) (Demirbas, 2008).
While hydrogen gas could be used to generate electricity in fuel cells which are highly efficient, this technology is not yet affordable (Demirbas, 2008).
Microbes are being engineered to enhance their ability to metabolize foodstuffs into potential fuels such as ethanol. As more microbial genomes are sequenced, the potential to augment biosynthetic pathways will increase (Fortman, 2008).
While the top agricultural plants used for the production of biodiesel are only 5% oil, some algae can achieve oil volumes equal to 80% of their mass. The
Improvements on the production of biofuels—the second generation of biofuels—is expected to come from the genetic engineering of potential crops to reduce their lignin content, ability to compete against undesirable species, and remove unwanted proteins from their tissues (Gressel, 2008). Switchgrass is one of the main native grasses of North American plains. It is being hybridized and genetically engineered to improve its potential as a major future biofuel (Bouton, 2007).
ADVANTAGES TO BIOFUELS
There are a number of advantages to biofuels. Biofuels are created from common plant materials rather than petroleum reserves whose availability is limited. The carbon which is released from biofuels is that which was extracted from the air during the plants’ growth so that no additional carbon enters the atmosphere when the biofuel is combusted (as opposed to coal and petroleum which releases carbon which had previously been buried for vast periods of time). Unlike many forms of renewable energy, biofuels produce solid and liquid products which can be stored and transported far from where they were produced (Demirbas, 2008).
The use of biofuels may also contribute to the socioeconomic success of local farmers and industries (as opposed to multinational companies which drill for oil in foreign countries) and decrease national security concerns of military involvement in politically unstable oil-producing regions (Demirbas, 2008).
Fossil fuels contribute to global greenhouse gases and are the major source of urban air pollution, given their release of nitrogen oxides, sulfur oxides, particulates, and unburnt hydrocarbons. Biofuels such as biodiesel reduce air pollution and improve engine performance (Sureshkumar, 2008 ; Demirbas, 2008).
DISADVANTAGES TO BIOFUELS
1) Do Biofuels Really Reduce Carbon Output?
Although the mixture of biofuels with fossil fuels in theory decreases the need for fossil fuels, calculations of the net improvement can give mixed results. Fossil fuel is required to process organic material to make fuel and the net reduction of fossil fuel use may be small or perhaps even result in an increase. Given that the fossil fuels needed to produce bioethanol from corn represent 80-90% of the energy potential of the corn, dedicating the entire corn crop to bioethanol production would only decrease the amount of carbon produced worldwide by 1% (Field, 2008; Von Blottnitz, 2007).
Biofuels have a greater amount of oxygen than petroleum which means that less energy is available during their combustion (Demirbas, 2008). Some crops are better suited for providing fuel than others. Starch-based plants, such as corn and potatoes for example, do not replace as much fossil fuel as sugar based crops, such as sugarcane.
2) Food for the Poor Versus Fuel for the Rich
Many areas of the world experience food shortages and, as human population increases, the number of those who experience hunger will increase. This is aggravated by the increase price of food because of demand for biofuel production.
The 32 million tons of corn which were used to meet 12% of the 2004
3) Many biofuels require a substantial amount of land which might otherwise hold forests which also remove carbon dioxide from the atmosphere. This is not universally true however given that biofuels can be generated from the parts of agricultural crops which are not used (such as cornstalks or molasses) (Von Blottnitz, 2007).
4) Farming new land for biofuels inevitably produces fertilizer and pesticide runoff into waterways
BIOLOGICAL SEQUESTRATION OF CARBON
Given that biofuels require a large input of fossil fuels (for fertilizer, transport, harvest, and other aspects), they add more carbon to the atmosphere than they remove. If a portion of the crop, perhaps a quarter, were converted to biochar, a black residue which could then be added to soil, the crops would become truly carbon negative (removing more carbon from the atmosphere than they add) and even improve the integrity of the soil (Matthews, 2008). Black carbon increases soil fertility, nutrient retention, water retention, and microorganism populations while decreasing acid levels and the release of greenhouse gases (Fowles, 2007).
Long-lived trees, such as sequoias, would be effective in sequestering large amounts of carbon for long periods of time (
CONSERVATION AS AN ENERGY SOURCE
A substantial amount of methane escapes coal mines through ventilation shafts. This contributes to global warming in addition to representing a loss of potential energy. New applications of technologies (such as combustion for heat) are making use of this methane (Warmuzinski, 2008).