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This document discusses various bioenergy crop plants that can be used as sources of renewable energy. It defines bioenergy and describes traditional, first, second, and third generation bioenergy crops. It also discusses potential bioenergy crop sources like algae, sugarcane, maize, wheat, edible and non-edible vegetable oils. The objectives are to identify bioenergy crop plants and evaluate their potential for bioremediation, nutrient/metal uptake, emissions, and impacts on biodiversity.
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- 1. DEBRE MARKOS UNIVERSIY COLLEGE OF NATURAL AND COMPUTATIONAL SCIENCE DEPARTMENT OF BIOTECHNOLOGY BIO ENERGY CROP PLANTS
- 2. Abstract Bioenergy is a renewable source of energy that is produced from plants and animals. Unlike bioenergy, fossil fuels, such as crude oil and coal, are not renewable. Because they are created over thousands to millions of years, fossil fuels are limited. Some forms of bioenergy have been around for a long time. Examples include burning wood to create heat, using biodiesel and ethanol to fuel vehicles, and using methane gas and wood to generate electricity. More recently, developed forms of bioenergy use materials called “biomass,” such as sugar cane, grasses, straw, soybeans, and corn. Biomass is any plant or animal matter that uses sunlight to store energy. Plants do this through photosynthesis. Animal waste, which is comprised mainly of plant material, is also biomass. Bioenergy crop plants that function as solar energy collectors and thermo-chemical energy storage systems are the basis for biological systems that are expected to contribute to renewable energy production, help stabilize the rising levels of green house gases (GHG), and mitigate the risk of global climate change (GCC). Wide genetic resource bases, especially of wild and semi- domesticated perennial grasses and woody species of starch-, oil, and lingocellulose- producing plants, are available to select, breed, genetically-modify, and develop environmentally-friendly bioenergy crops. Plant species, They contribute to the reduction of greenhouse gas emissions and thus the slowing of climate change and its negative impacts. Bioenergy can be used to produce fuel for the transport sector or through biomass combustion to produce heat and/or power. With rising energy costs and uncertainty of fossil fuel reserves, it’s important to oversee cheaper, safer, and more renewable forms of bio-energy. As a supplemental alternative energy to coal, bio-energy crops could play an important role as environmentally safe . Introduction Bioenergy is defined as a renewable energy that is manufactured from biomass. Organic materials such as trees,plants and waste materials come under the broad area of biomass. Bioenergy has received a great interest during the recent times because of rapid growth of fuel prices, fast fossil fuel depletion,environmental degradation by fossil fuel and an alteration in global climate. A feedstock refers to a
- 3. material that serves as the basis for manufacturing another product. For the production of bioenergy,biomass feedstocks serve as key inputs. Biomass feedstocks can be made available from various sources such as agricultural or energy crops,waste fuels, etc. These biomass feed stocks serve as the source of organic matter (Yuan et al., 2008; Zych,2008; Chum et al., 2011) Bioenergy development is intended, in part, to offset greenhouse gas (GHG) emissions to the atmosphere, but analyses of the GHG balances of bioenergy crops have concluded vastly different magnitudes of this benefit(Davis et al., 2009). Some analyses indicate that theGHG emissions associated with bioenergy agriculture can be significant, thus negating the intended mitigation(e.g., Crutzen et al., 2008; Searchinger et al., 2008), and others find substantial emissions savings compared with fossil fuel use (e.g., Farrell et al., 2006; Adler et al.,2007). These diverse findings are the result of differing assumptions about the geography, system boundaries,inventories, and land use associated with a given bioen-ergy cropping system (Cherubini et al., 2009; Daviset al., 2009), but real differences among species and management regimes are also clearly evident (Melilloet al., 2009; EPA, 2010; Bird et al., 2011). The large scale land-use changes associated with bioenergy production will have consequences on many aspects of environmental and human health, including food supply, water shed cleanliness, soil quality, and ecological diversity (e.g Service 2007, Dominguez-Faus et al 2009, Ditomasoet al 2010, Pedroli et al 2013). In some cases, theenvironmental costs associated with bioenergy pro-duction and consumption have been estimated tooutweigh the benefits of reduced fossil fuel combus-tion completely (Hill et al 2009, Tessum et al 2014) The use of bioenergy crops to reduce the negative effects and exploit possible positive effects of GCC is set to increase in the developing as well as the developed world.Theoretical biomass resources are poten-tially the world’s largest sustainable bioenergy source comprising about 220 billion oven-dry tons or 4,500 EJ of annual
- 4. primary production (if marine phytoplankton resourceis included). Oprovided by bioenergy crops (Smeets et al., 2007) There is a great challenge and concern, that cultivationof energy crops might reduce land availability for feed and food production(FAO 2008). Objective To identify bioenergy crop plants. To review opportunities for bioremediation with energy crops. To evaluate the likely magnitude of available land and waste application rates. To quantify possible nutrient and metal losses, via leaching in soils and water. To quantify nutrient and metal uptake by energy crops. To evaluate the likely magnitude of atmospheric emissions of CH 4 , N 2 O and CO 2 from wastes applied to energy crops. To evaluate the impact of waste application, and/or siting on contaminated soils, on biodiversity associated with energy crops. To identify research requirements. Characteristics of bioenergy crops In addition, the large diversity available in germ plasm of perennial SRC and lignocellulosic grasses for eco-physiological traits such as leaf area (LA), leaf area index (LAI), and specific leaf area(SLA), branching habit, and biomass partitioning patterns has been shown to influence clonal biomass production potential(Tharakan et al., 2001; Carroll and Somerville, 2009), will help develop improved bioenergy crops. Bioenergy crops with vegetative storage organs (e.g., stems in the C 4 sugarcane and roots in the C 3 sugar beet) are able to accept assimilates for storage over longer periods than grain crops. Vegetative storage reduces feed-back restriction to yield accumulation during environmental stress; and sucrose, as the storage product of PS, is the least transformed and therefore subject to smallest losses by subsequent metabolism (Wanget.al 2008)
- 5. Bioenergy crops to combat climate change basid on biomass production and their use energy crop they are classified following categories: Traditional bioenergy crops Biomass has always been a major source of energy for mankind and presently contributes 10-14% of the world’s energy supply. Traditional biofuels derived from natural vegetation or from crop residues are not new, have not always been good for health or for the environment and have competed with food production in developing countries where 70-75% of the energy used is in the form of biomass and almost 90% of it is used for food preparation (Kotchoniand Gachomo, 2008; Lobell et al., 2008). however, they are not sustainable; their exploitation may contribute to land degradation and desertification (Karpand Shield, 2008). First generation bioenergy crops (FGECs) It is generally well understood that FGECs are limited in their ability to achieve targets for oil-product substitution, GCC mitigation, and economic growth (Chhetri et al., 2008; Carroll and Some rville, 2009; Lorenz et al., 2009). For most crops the annual change in above ground C is equal to zero if the whole biomass is taken away for energy production. The cost and sustainability of FGECs, other than sugarcane (Wang et al.,2008), have been criticized as expensive sources to meet environmental goals, and to provide energy alternative. These limitations can be partly overcome by the utilization of lignocellulosic materials from their residues (Eisenbies et al.,2009) Second generation bioenergy crops (SGECs) The SGECs are expected to be more efficient than FGECs and to provide fuel made from cellulose and non-oxygenated,pure hydrocarbon fuels such as biomass-to-liquid (BtL) fuel(Oliver et al., 2009). The use of indigenous perennial grass species is particularly promising, both
- 6. because these are likely to be well adapted to local environment, and because they are less likely to adversely affect biodiversity than are non-native species,which are frequently invasive. On average, increasing species richness in perennial herbaceous poly cultures increased productivity and weed suppression, but well-adapted specie sproduced high biomass yield regardless of richness(Fransworth and Meyerson, 2003; Picasso et al., 2008). Third generation bioenergy crops (TGECs In combination with other strategies including (meta)genomics,biodiversity studies, and system biology, metabolic engineer-ing is a promising approach to the improvement of biofuelyields and the establishment of renewable, non- pollutingenergy source from TGECs that can mitigate GCC (Bush,2007; Ehrlich and Pringle, 2008; Rubin, 2008). There is a large reservoir of boreal plant species that can be harnessedin CH 4 production. These plants are easy to cultivate, harvest and store, are tolerant to weeds, pests, diseases, drought and frost, and have good winter hardness and able to grow on poor soils with low nutrient inputs (Finckh, 2008). Dedicated bioenergy crops The development and deployment of dedicated energy crops have been proposed as a strategy to produce energy without impacting food security or the environment (Lobell et al.,2008; Jessup, 2009). The dedicated energy crops are mainly perennial herbaceous and woody plant species. Genetic resources for the development of dedicated energy crops with low requirements for biological, chemical or physical pretreatment are more environmentally friendly and will contribute more to GCC mitigation (Petersen, 2008;Taherzadeh and Karimi, 2008). Sources of bioenergy crop plants Algae as a bioenergy source Microalgae are unicellular orsimple multicellular organisms and can beprokaryotic or eukaryotic in nature.Microalgae have the capability to grownaturally in fresh or
- 7. salt waters. Due to thesimple cellular structure of microalgae, theycan efficiently convert solar energy.Microalgae are considered among the oldestliving organisms onour planet earth.Microalgae canserve as the energy sources for theproduction of biodiesel with renewablenature and apart from that microalgalbiofuels can help in overcoming thelimitations of first and second generation ofbiofuels (Htet et al., 2013;Saifullah et al.,2014) Sugarcane as a bioenergy source. Sugarcane comes under one of the mosteffective crops in the collection of solar energy and its conversion to chemicalenergy. The potential of sugarcane as abiomass feedstock is widely acknowledged.When sugarcane is given for processing,there is the production of large amounts ofsugarcane bagasse which is nowadays usedfor steam and electricity generation byburning in boilers(Cushionet al., 2009; Weijde et al., 2013) Maize as a bioenergy source. Maize is one of the largest crops that is cultivated worldwide and it has the property of playing an important role in biofuel development. If maize is to be used for the production of biofuels, then it needs to be cultivated for two purposes viz: for grain production as well as for the production of stem-biomass and that too in higher yields. Because of the availability of resources such as those of agronomic and genomicre sources, maize can be cultivated as a dual crop with ease. Due to the presence of all these qualities and availability of resources,maize can be considered as a best model crop for biomass quality in the field of research (Weijde et al., 2013). Wheat as a bioenergy source. Wheat has the potential to become a major biofuel crop. Using fermentation as a process to produce ethanol from wheat provides a fuel that can be used to runvehicles. Wheat comes under the category of C3 species of plants i.e. plants performing C3 photosynthesis. These species of plants have enough potential of accumulating carbon dry mass which provides enough biomass for energy
- 8. conversion (McKendry, 2002) Edible vegetable oils as a bioenergy source Edible oils have a great potential to be used as a feedstock for the production of biofuels. Palm oil, soybean oil and rapeseed oil represent the main edible oils which are produced worldwide and together they constitute 75% of the total edible oil production in recent times. In spite of the enormous potential that biodiesel possesses, the limitations come on the way in case edible oils as feed stocks because of their growing demands and their high cost (Calle et al., 2009). Non-edible vegetable oils as abioenergy source Non-edible oils have a great capability to be used as feed stocks for biofuel production particularly biodiesel. Non-edible oils as feed stocks for biodiesel production can help in reducing the cost of biodiesel production. Jatropha, Pongamia,Palm, Mahua, etc. are the various sources that are present in nature in excess amounts and can serve as a great feedstock. When compared to edible oils, these plants are very economical and are readily available in developing countries. In order to decrease the viscosity of vegetable oils and to make them use as fuels, there are several methods available that can carry out this processnamely: micro- emulsification, pyrolysis,transesterification, etc. For the commercialproduction of biodiesel, the mostcommonly used method employed istransesterification because within a shorterreaction time and the use of lowtemperature and high pressure it gives ahigh yield (Shikha and Rita, 2012; Liaquatet al., 2012).