User:Jiankai Wu/Sandbox

Energy crop is one of the common feedstocks in producing biofuels. It is normally planted on degraded lands that abandoned from agricultural use (6). Energy crop is renewable energy biomass. It is made up with existing plants, such as switch grasses and legumes, but was available for producing bioenergy within the decade.

Benefits Planning energy crop offers potential benefits in both environmental and public areas. Environmental benefits: Carbon is a significant compound in life cycle. The process of planting energy crop can be considered as carbon negative because nergy crops fixes carbon dioxide from atmosphere by photosynthesis and release equal or even less carbon in later use (5). Plantation of energy crop riches the C containing in soil in the same time. Soil and biomass are the two largest biologically active stores of carbon on earth (1). Moreover, planning energy crops on degraded lands avoid additional land deterioration. At the same time, it contributes to increase the wildlife habitat and improve water quality (6). Public benefits: Perennial energy crops supply plenty feedstock for bioenergy production which enlarge the energy security for industry and daily life consumption. On the other hand, reuse the degrade lands for energy crops reduces the competition with agricultural lands and the use of food crops (corns) for energy production. Also it maintains the sustainability of food supply (6). In addition, energy crops offer the support to rural economies (6). Although the cost of producing bioenergy through energy crops still high and prevent large scale production, technology improvement would solve the problems soon.

Ways to improve yield of energy cropsBetter functional composition Poor nutritious level of these degraded lands highly limited the harvest of energy crop. To increase the energy crop’s yield but not bring in more energy, one major source is to apply Low-Input High-Diversity (LIHD) system into energy crop plantation (1). In which, high diversity refers to selected species richness in creating better yielding functional composition. Current studies indicated that legume/C4 bicultures composition gains the maximum yield for energy crop at the moment (2) (3) (7). The complementary effect caused by C4 grasses and legumes is the key in LIHD system. In such degraded lands, nutritious level, especially levels of C and N containing, are extremely low after long term agriculture. It takes more than decades for C and N to accrual in soil (2). Monoculture plantation is not able achieve the increasing yield. However, legumes are in high litter quality (low C : N) and high litter decomposition rate, they do not efficiently use nutrition, such as C, in their life cycle (2). Indeed, because of the symbiotic relationship in N-limited environment, the bacteria in legumes’ root allow large amount of N been accumulated in soil and supply for other plats using (2). In contract, C4 grasses have high root biomass which is the major product in this functional composition. They grow in soil with low mineralization and decomposition rates (2). But they consume nutrient very except N (2). With opposite consumptions of nutrient in life cycle, C4 grasses and legumes combining plant spots have more efficiency use in limited nutrient and space than monoculture or other species compositions which lack of either C4 grasses or legumes. Moreover, C4 grasses and legumes do not share identical growth schedule. The C4 – legumes interaction enlarges C accumulation in the soil via cool-season by C4 grasses (2) (3). Then the legumes store N in warm-season via N fixation. C4 grasses are high N immobilization which creates a low NO3 environment. This leads legumes to fix more N in growing (2) (3). The legume/C4 bicltures composition contributes in maximizing energy crop’s biomass yield.

Genetic engineering apply Most biofuels are made by fermentation of plant sugars (8). Cellulose, the major crystalline in plants cell wall, is the major sugar used in producing biofuels (4). A cellulose enzyme breaks down the sugars into single glucoses which will be fermented into biofuels by microbes (8). This sugar is fully filled in energy crop. However, lignin is other compound of the cell wall which has negative impact in cellulosic biofuel production (4). In that case, engineering feedstock crop with degrading lignin and polysaccharide might be a solution. The key is to remove or minimize the quantity and quality of lignin by genetic transformation techniques without changing other compounds’ formation of the plant and allow C to accumulate from plants into soils (9). Research approves that the biosynthesis of lignin is related to a complex enzyme regulation (9). In most plants, coniferyl and sinapyl would synthesis to form syringyl (S)-guaiacyl (G)monolignols, which can become lignin (9). The gene encoding 4-coumarate: CoAligase (4CL) regulates this pathway. Modification of this gene allows reducing lignin up to 45% with 15% of increase of cellulose concentrations in plants (9). Technology of genetic engineering applies in plants cells allow to modify the genes in the selected energy crop. The crop with genetic modification reduce amount of lignin genes in cell wall, in the same time, the containing of cellulosic has the tendency in increase.

Reference 1.	Tilman D, Hill J, and Lehman C. Carbon-Negative biofuels from Low-Input High-Diversity grassland biomass. Science 2006; 314:1598-1600 2.	Fornara DA and Tilman D. Plant functional composition influences rates of soil carbon and nitrogen accumulation. Journal of Ecology 2008; 96. 314-322 3.	Adler PR, Sanderson MA, Weiemr PJ, and Vogel K. Plant species composition and biofuel yiekds of conservation grassland. Ecological Application 2009; 19(8), 2202-2209 4.	Li X, Weng JK, and Chapple C. Improve of biomass through lignin modification. The Plant Journal 2008; 54 569-581 5.	Demirvas A. Combustion of biomass 2007; Energy Sources, part A, 29; 549-561 6.	Tilman D, Socolow R, Foley JA, Hill J, Larson E, Lynd L, Pacala S, Beilly J, Seachinger T, Somerville C, Williams R. Beneficial biofuels – the food, energy, and environment trilemma. Science 2009; 325 270-271 7.	Dehaan LR, Weisbery S, Tilman D, Fornara D. Agriculture and biofuel implication of a species diversity wxperiment with native perennial grassland plant. Ecosyst 2009; 8.	Alternative & Renewable Energy. Web, http://www.bantrel.com/markets/renewableenergy.aspx 9.	Hancock JE, Loya WM, Giardina CP, Li L, Chiang VL, and Pregitzer KS. Plant growth, biomass partitioning and soil carbon formation in response to altered lignin biosynthesis in populous tremuloides. New Phytologist 2007; 173 732-742