High-yielding Energy Crops Research Articles

Second Generation Biofuel – An Alternate Source of Energy

The use of fossil fuels in the current situation has been increased. These fossil fuels do not come under the category of sustainable sources due to its depleting nature. Fossil fuels also pollutes the environment by increased emission of Greenhouse Gases (GHG). In order to produce an alternate renewable energy and to reduce the percentage of environmental pollution caused, many technologies like solar energy, tidal energy, wind energy etc. came into existence. But all these forms of energy can be produced in terms of electricity. To meet the increasing fuel demand, renewable biofuels came into the field where biomasses are utilized to produce biofuels. Second generation renewable biofuels are produced from conventional plant sources with higher oil content whose efficiency is determined by the amount of Green House Gases (GHG) emitted and the life cycle cost whether positive, neutral or negative. High yielding energy crops such as sugarcane, corn, switchgrass, wheat etc. are subjected to various processes / fermentation to yield biofuels like bioethanol, biobutanol, biohydrogen, biodiesel etc. The US and Brazil are replacing the demand for gasoline with around 15% of bioethanol and it has a higher octane rating, increased engine’s compression ratio, increased thermal efficiency and ultimately reduces atmospheric pollution emissions. In future biofuels will be recognized as alternative fuel in transportation, energy generation, heat producer, charging electronics, environmental friendly cleaners, cooking, lubricants, adhesives etc. This review provides a brief outline about the second generation biofuels which would serve as an alternative energy in the near future.

Assessment of Miscanthus Yield Potential from Strip-Mined Lands (SML) and Its Impacts on Stream Water Quality

Strip-mined land (SML) disturbed by coal mining is a non-crop land resource that can be utilized to cultivate high-yielding energy crops such as miscanthus for bioenergy applications. However, the biomass yield potential, annual availability, and environmental impacts of growing energy crops in SML are less understood. In this study, we estimated the yield potential of miscanthus (Miscanthus sinensis) in SML and its environmental impacts on local streams using the Soil and Water Assessment Tool (SWAT). After calibration and validation of the SWAT model, the results demonstrated that miscanthus yield potentials were 2.6 (0.8−5.53), 10.0 (1.3−16.0), and 16.0 (1.34−26.0) Mg ha−1 with fertilizer application rates of 0, 100, and 200 kg-N ha−1, respectively. Furthermore, cultivation of miscanthus in SML has the potential to reduce sediment (~20%) and nitrate (2.5−10.0%) loads reaching water streams, with a marginal increase in phosphorus load. The available SML in the United States could produce about 10 to 16 dry Tg of biomass per year without negatively impacting the water quality. In conclusion, SML can provide a unique opportunity to produce biomass for bioenergy applications, while improving stream water quality in a highly dense mining area (the Appalachian region) in the United States.

Biofuels technology development in Southern Africa

ABSTRACT The benefits of biofuels depend on the feedstock, conversion pathway and local context. This paper assesses biofuels technology readiness and developments to provide foresight to biofuels development in Southern Africa. Efficient conversion pathways, coupled with biomass from waste or high-yielding energy crops, will reduce both the costs of biofuels production, and the environmental impacts. Compared to petroleum fuels, the current commercial biofuels (ethanol, biogas and biodiesel) typically offer carbon emission reductions of 30–50% but are marginally more expensive. The extent of biofuels market penetration will therefore be influenced by mandates (blending targets) and subsidies (green premium). Advanced biofuels promise greater efficiencies and carbon emission reductions at reduced cost but will require further research and development to reach commercialisation. If developed appropriately, biofuels can reduce carbon emissions and improve energy security, while enabling sustainable agriculture and improved natural resources management.

Transcriptomics and proteomics reveal genetic and biological basis of superior biomass crop Miscanthus

Miscanthus is a rhizomatous C4 grass which is considered as potential high-yielding energy crop with the low-nutrient requirements, high water-use efficiency, and capability of C mitigation. To better understand the genetic basis, an integrative analysis of the transcriptome and proteome was performed to identify important genes and pathways involved in Miscanthus leaves. At the transcript level, 64,663 transcripts in M. lutarioriparius, 97,043 in M. sacchariflorus, 97,043 in M. sinensis, 67,323 in M. floridulus and 70,021 in M. × giganteus were detected by an RNA sequencing approach. At the protein level, 1964 peptide-represented proteins were identified and 1933 proteins differed by 1.5-fold or more in their relative abundance, as indicated by iTRAQ (isobaric tags for relative and absolute quantitation) analysis. Phylogenies were constructed from the nearly taxa of Miscanthus. A large number of genes closely related to biomass production were found. And SSR markers and their corresponding primers were derived from Miscanthus transcripts and 90% of them were successfully detected by PCR amplification among Miacanthus species. These similarities and variations on the transcriptional and proteomic level between Miscanthus species will serve as a resource for research in Miscanthus and other lignocellulose crops.

SRC willow as a bioremediation medium for a dairy farm effluent with high pollution potential

Dairy farm dirty water (FDW), consisting of parlour washings contaminated with cattle faecal matter, urine and agri-nutrients was used to irrigate a 5 ha short rotation willow coppice planted with six genotypes of commercially available, high yielding energy crop willows in an experiment conducted over 5 years. The willow genotypes selected were chosen primarily for their disease and pest resistance properties though they also differed in yield potential, dry matter, energy and nutrient content; factors critically important for growers and end users. Throughout the duration of the trial the pH, conductivity, nitrogen, phosphorus and potassium concentrations of the FDW were consistent and without significant differences, although biochemical oxygen demand (BOD) levels did differ significantly between years (2753 ± 259 mg L−1). Soil, ground and drainage waters were generally not seen to be adversely affected by application of the FDW, with nutrients found to remain at pre-irrigation concentrations or similar to waters from non-irrigated catchments. Soil phosphorus content remained relatively stable at the lower treatment rates but did rise significantly at the highest irrigation rate. Biomass dry matter yields, harvested after a 3-year growth rotation, ranged from 26.7 to 42.9 Mg ha−1 3yr −1 and showed significant differences (P < 0.05) in yields between genotypes but not treatments. Three year old harvested stem tissues and leaves had significant differences in nutrient concentrations that were related more to genotype than treatment. Off-takes of nitrogen, phosphorus and potassium (average 0.22 ± 0.04, 0.04 ± 0.01 and 0.09 ± 0.01 Mg ha−1 3y−1 respectively) found in harvested biomass showed significant differences between genotypes but not treatments. The results indicated that this particular type of farm effluent, with a particular range of nutrient concentrations, was applied at specific rates to SRC willow without detriment to soil, ground and drain waters, site soils and biomass yields. Genotype was the major influence on crop yield and nutrient off-take.

Dynamic modelling of cut-and-store systems for year-round deliveries of short rotation coppice willow

Short rotation coppice willow (SRCW) is a high-yielding energy crop that can be used to produce solid, liquid or gaseous biofuels. The crop is harvested during the winter, when the leaves have dropped. For economic reasons, however, most fuel processing plants require continuous year-round delivery of raw material. Thus, SRCW should be harvested as stems or in larger pieces in order to be storable, and not chipped directly at harvest for immediate use in large-scale heating plants, which is common practice at present. The aim of the project within which this study was conducted is to find cost-effective whole-stem harvesting and handling systems for year-round deliveries of natural-dried SRCW. A discrete event simulation model for such systems was developed in this study, taking weather, soil trafficability, geographical conditions, natural drying of the material and storage losses into account. The model was applied to a fictitious processing plant in Uppsala, Sweden. Machine performance and costs for a system with one stem harvester and up to three in-field shuttles, together with one chipper truck for chipping and transport, were investigated. The simulations showed that field trafficability had a crucial impact on total quantity harvested. The total cost was € 40 t −1 dry matter. Yield of SRCW and harvest productivity were important factors regarding costs. The model can be used to design cost-effective harvesting and handling systems for year-round deliveries of SRCW.

Enhanced volatile fatty acids production during anaerobic digestion of lignocellulosic biomass via micro-oxygenation

A series of batch experiments were conducted to investigate the effects of inoculum type, oxygen (O2) dosage, and incubation time on volatile fatty acids (VFAs) production during anaerobic digestion (AD) of Napier grass (Pennisetum purpureum), a high yielding energy crop. The results showed that anaerobically digested cattle manure (ADCM) as an inoculum generated significantly higher VFAs compared to that of anaerobically digested waste activated sludge (ADWAS) as an inoculum. Additionally, the incubation time of 3days and O2 dosage of 15mL/g volatile solidsadded showed the highest VFAs production when ADCM was used as an inoculum. Moreover, the VFAs production had a quadratic correlation with O2 dosage with R2 of 0.86. The Scanning Electron Microscopy (SEM) images of the digested fiber showed rough and crumbled surface structures as opposed to that of the undigested fiber, which was further confirmed by changes in structural composition of the digested fiber.

Imaging for High-Throughput Phenotyping in Energy Sorghum

The increasing energy demand in recent years has resulted in a continuous growing interest in renewable energy sources, such as efficient and high-yielding energy crops. Energy sorghum is a crop that has shown great potential in this area, but needs further improvement. Plant phenotyping—measuring physiological characteristics of plants—is a laborious and time-consuming task, but it is essential for crop breeders as they attempt to improve a crop. The development of high-throughput phenotyping (HTP)—the use of autonomous sensing systems to rapidly measure plant characteristics—offers great potential for vastly expanding the number of types of a given crop plant surveyed. HTP can thus enable much more rapid progress in crop improvement through the inclusion of more genetic variability. For energy sorghum, stalk thickness is a critically important phenotype, as the stalk contains most of the biomass. Imaging is an excellent candidate for certain phenotypic measurements, as it can simulate visual observations. The aim of this study was to evaluate image analysis techniques involving K-means clustering and minimum-distance classification for use on red-green-blue (RGB) images of sorghum plants as a means to measure stalk thickness. Additionally, a depth camera integrated with the RGB camera was tested for the accuracy of distance measurements between camera and plant. Eight plants were imaged on six dates through the growing season, and image segmentation, classification and stalk thickness measurement were performed. While accuracy levels with both image analysis techniques needed improvement, both showed promise as tools for HTP in sorghum. The average error for K-means with supervised stalk measurement was 10.7% after removal of known outliers.

Mix of First- and Second-Generation Biofuels to Meet Multiple Environmental Objectives: Implications for Policy at a Watershed Scale

Biofuel mandates are being widely used by countries to achieve multiple objectives of energy security and climate change mitigation. The Renewable Fuel Standard (RFS) in the US specifies arbitrarily chosen volumetric targets for different types of biofuels in the US based on their greenhouse gas intensity only. Cellulosic biofuels from high yielding energy crops like miscanthus have the potential to co-generate multiple environmental impacts, including reducing nitrate runoff, being a sink for Greenhouse Gas (GHG) emissions and providing a given volume of biofuel with less diversion of land from food crop production than corn ethanol, but at a significantly higher cost. This paper quantifies the tradeoffs between profitability, food and fuel production, GHG emissions and nitrate runoff reduction with different types of biofuels in the Sangamon watershed in Illinois and analyzes the optimal mix of biofuels as well as the policies that should supplement the mandate to achieve multiple environmental outcomes. We find that a two-thirds share of cellulosic biofuel in the mandated level could reduce nitrate run-off by 20% while reducing GHG emissions by 88–100% but would reduce profits by 15–27% depending on whether a GHG policy or a Nitrate policy is used relative to the case where the mandate is met by corn ethanol alone. Additionally, the ratio of corn stover to miscanthus used to produce cellulosic biofuels is higher under a GHG policy compared to a Nitrate policy that achieves the same level of nitrate reduction. Our results show that the optimal mix of different types of biofuels and the policy to induce it depend on the environmental objectives and the tradeoffs that society is willing to make between low cost energy security, food production and various environmental benefits.

Tau method for the numerical solution of a fuzzy fractional kinetic model and its application to the oil palm frond as a promising source of xylose

The Oil Palm Frond (a lignocellulosic material) is a high-yielding energy crop that can be utilized as a promising source of xylose. It holds the potential as a feedstock for bioethanol production due to being free and inexpensive in terms of collection, storage and cropping practices. The aim of the paper is to calculate the concentration and yield of xylose from the acid hydrolysis of the Oil Palm Frond through a fuzzy fractional kinetic model. The approximate solution of the derived fuzzy fractional model is achieved by using a tau method based on the fuzzy operational matrix of the generalized Laguerre polynomials. The results validate the effectiveness and applicability of the proposed solution method for solving this type of fuzzy kinetic model.

Climate Impact of Willow Grown for Bioenergy in Sweden

Short-rotation coppice willow (SRCW) is a fast-growing and potentially high-yielding energy crop. Transition to bioenergy has been identified in Sweden as one strategy to mitigate climate change and decrease the current dependency on fossil fuel. In this study, life cycle assessment was used to evaluate and compare the climate impacts of SRCW systems, for the purpose of evaluating key factors influencing the climate change mitigation potential of SRCW grown on agricultural land in Sweden. Seven different scenarios were defined and analysed to identify the factors with the most influence on the climate. A carbon balance model was used to model carbon fluxes between soil, biomass and atmosphere under Swedish growing conditions. The results indicated that SRCW can act as a temporary carbon sink and therefore has a mitigating effect on climate change. The most important factor in obtaining a high climate change-mitigating effect was shown to be high yield. Low yield gave the worst mitigating effect of the seven scenarios, but it was still better than the effect of the reference systems, district heating produced from coal or natural gas.

Spatially and Temporally Optimal Biomass Procurement Contracting for Biorefineries

This paper evaluates the optimal composition of annual and perennial biomass feedstocks for a biorefinery. A generic optimization model is built to minimize costs – harvest, transport, storage, seasonal, and environmental costs – subject to various constraints on land availability, feedstock availability, processing capacity, contract terms, and storage losses. The model results are demonstrated through a case study for a midwestern U.S. location, focusing on bioethanol as the likely product. The results suggest that high-yielding energy crops feature prominently (70 to 80%) in the feedstock mix in spite of the higher establishment costs. The cost of biomass ranges from 0.16 to 0.20 $ l-1 (US$ 0.60 to $0.75 per gallon) of biofuel. The harvest shed shows that high-yielding energy crops are preferably grown in fields closer to the biorefinery. Low-yielding agricultural residues primarily serve as a buffer crop to meet the shortfall in biomass requirement. For the case study parameters, the model results estimated a price premium for energy crops (2 to 4 $ t-1 within a 16 km (10-mile) radius) and agricultural residues (5 to 17 $ t-1 in a 16 to 20 km (10 to 20 mile) radius.

Yield and Nitrogen Management of Irrigated Switchgrass Systems in Diverse Ecoregions

Climate trends and foreign oil dependency have led to a search for alternative sources of energy, such as biomass energy crops. Switchgrass (Panicum virgatum L.) has shown promise as a high yielding energy crop in the United States. The objectives of this study were to evaluate cultivar Trailblazer switchgrass adaptability, biomass yield potential, and response to N fertilization in different ecoregions. Experiments were established in four ecoregions of California in 2007, with five N fertilizer treatments (0 to 300 kg N ha−1 yr−1) imposed from 2008 through 2010. The northern‐most and coolest temperate continental climate location was terminated after 2009 due to appreciable winter mortality. Yields ranged from 13 to 27.1 Mg ha−1 yr−1 across locations and years, with greatest yields in the warmer Mediterranean and semiarid climates of the Central Valley and the Desert climate region. Yield response to N was limited in 2008. However, in 2009 and 2010, yields increased linearly in three of four locations, indicating that greater yields could have been possible with greater N fertilization rates. On average across locations, the greatest N rate increased yields by 9.7 and 13 Mg ha−1 yr−1 and agronomic N use efficiency averaged 30 and 44 kg biomass kg−1 N applied in 2009 and 2010, respectively. Average crop N removal was 150 kg N ha−1 yr−1 for multi‐harvest systems, with the first harvest representing 70% of annual yields and 75% of crop N removal. Our results showed that in warm ecoregions with greater yield potential Trailblazer switchgrass required great N fertilization to sustain yields.

Kinetic model analysis of dilute sulfuric acid-catalyzed hemicellulose hydrolysis in sweet sorghum bagasse for xylose production

Sweet sorghum is a high-yielding energy crop that leaves a large amount of lignocellulosic residues after the sugar fraction fermented to ethanol. Here, we developed a biphasic kinetic model for the dilute sulfuric acid-catalyzed hemicellulose hydrolysis of sweet sorghum bagasse at temperatures of 110–150°C, and we then calculated the kinetic parameters for xylose production and furfural decomposition. The results indicated that elevated reaction temperatures promote the hydrolysis of hemicellulose and the degradation of xylose. The xylose yield increased in proportion to reaction time in the initial stages and then declined due to the degradation of xylose to furfural. The pre-exponential factors for the ‘easy-to-hydrolyze’ fraction, the ‘hard-to-hydrolyze’ fraction of hemicellulose and xylose degradation were 3.53×106, 1.80×105 and 0.62min−1, respectively, and the activation energies were 60.7, 58.1 and 14.5kJ/mol, respectively. The ideal hydrolysis condition for xylose production was 140°C for 50min, under which the xylose yield reached 60% of hemicellulose weight. This xylose can be used to form bioethanol and produce further downstream products.

A spatially explicit whole-system model of the lignocellulosic bioethanol supply chain: an assessment of decentralised processing potential.

BackgroundLignocellulosic bioethanol technologies exhibit significant capacity for performance improvement across the supply chain through the development of high-yielding energy crops, integrated pretreatment, hydrolysis and fermentation technologies and the application of dedicated ethanol pipelines. The impact of such developments on cost-optimal plant location, scale and process composition within multiple plant infrastructures is poorly understood. A combined production and logistics model has been developed to investigate cost-optimal system configurations for a range of technological, system scale, biomass supply and ethanol demand distribution scenarios specific to European agricultural land and population densities.ResultsEthanol production costs for current technologies decrease significantly from $0.71 to $0.58 per litre with increasing economies of scale, up to a maximum single-plant capacity of 550 × 106 l year-1. The development of high-yielding energy crops and consolidated bio-processing realises significant cost reductions, with production costs ranging from $0.33 to $0.36 per litre. Increased feedstock yields result in systems of eight fully integrated plants operating within a 500 × 500 km2 region, each producing between 1.24 and 2.38 × 109 l year-1 of pure ethanol. A limited potential for distributed processing and centralised purification systems is identified, requiring developments in modular, ambient pretreatment and fermentation technologies and the pipeline transport of pure ethanol.ConclusionThe conceptual and mathematical modelling framework developed provides a valuable tool for the assessment and optimisation of the lignocellulosic bioethanol supply chain. In particular, it can provide insight into the optimal configuration of multiple plant systems. This information is invaluable in ensuring (near-)cost-optimal strategic development within the sector at the regional and national scale. The framework is flexible and can thus accommodate a range of processing tasks, logistical modes, by-product markets and impacting policy constraints. Significant scope for application to real-world case studies through dynamic extensions of the formulation has been identified.