Biomass and energy yield of industrial hemp grown for biogas and solid fuel

This study examined the energy yield of hemp (Cannabis sativa L.) cultivated for energy purposes under cold climate conditions in Northern Europe. Split-plot field trials were carried out over three consecutive years to investigate different nitrogen fertilisation regimes. Dry matter yield per hectare, moisture content, hydrogen content and heating value were determined at roughly monthly intervals from July until the following spring every season. The energy yield was calculated and adjusted for a fair comparison with those of other energy crops commonly grown in the study region.Two harvest periods for optimal energy yield have been determined; harvest in September to October, when the hemp is used for biogas production, yielded 14.4 Mg ha⁻¹ and 296 GJ ha⁻¹; harvest in February to April, when the hemp is used as a solid fuel, yielded 9.9 Mg ha⁻¹ and 246 GJ ha⁻¹. For biogas production, the adjusted biomass energy yield of hemp was similar to that of maize and sugar beet and 24 and 14% greater than that of lucerne and clover-grass ley, respectively. As a solid fuel, the adjusted biomass energy yield of hemp was 120% higher than that of wheat straw and similar to that of reed canary grass. Annual variations in dry matter yield depending on weather conditions and sowing dates exceeded variations due to nitrogen fertilisation.Hemp is suitable as an energy crop in cold climate regions of Northern Europe, as it has similar or often higher energy yields than other common energy crops grown in these regions.     

Anaerobic digestion of maize focusing on variety,harvest time and pretreatment

The methane potential of six varieties of fresh maize (whole plant) harvested at three different times and of maize silage (whole plant) in two particle size distributions was experimentally determined in batch assays. Fresh maize gave the highest methane yield/hectare at late harvest (6270 m³ CH₄ (10⁴ m²)⁻¹). The methane yield/wet weight (WW) increased from 80 (early harvest) to 137 m³ CH₄ (t WW)⁻¹ (late harvest). Maize harvested at different times, or different varieties of maize had similar specific methane production/volatile solids content (m³ CH₄ (kg VS)⁻¹). The measured yield m³ CH₄ (kg VS)⁻¹ was 84% of the theoretical methane potential. The estimated ethanol yield was between 2.5 and 3.5 t ethanol (10⁴ m²)⁻¹. The energy yield was 62 and 19–22 MWh (10⁴ m²)⁻¹ if fresh maize (whole plant) is used for methane or ethanol production respectively. Reducing the particle size of maize silage to an average size of approximately 2 mm increased the methane yield m³ CH₄ (kg VS)⁻¹ by approximately 10%.     

Impact of genotype, harvest time and chemical composition on the methane yield of winter rye for biogas production

Rye (Secale cereale L.) is an ideal crop for the agricultural biogas production in regions with less fertile and sandy soils. Maximum methane yield per hectare is the main aim of the farmer. Objectives were to establish differences by the Hohenheim Biogas Test among (1) 25 genotypes (experiment 1) and (2) three harvest dates (early heading, early and late milk ripening) and three plant fractions (ears, leaves and stems, stubbles) for four genotypes including an analysis of their nutrient composition (experiment 2). Significant (P < 0.05) genotypic variation was found for dry matter yield, specific gas yield and methane yield among the 25 genotypes, but no differences for methane content and specific methane yield. Broad ranges were achieved for dry matter yield (0% water content) and methane yield amounting to 2.9 t ha⁻¹ and 840 m³ ha^-1 respectively, combined with moderate to high heritabilities (0.71-0.98). Both traits were highly correlated (r = 0.95, P < 0.01). Compared to population and forage rye, hybrid rye achieved significantly higher methane yields. The latest harvest date at late milk ripening resulted in the highest dry matter yield on a whole plant level with an average of 16.0 t ha⁻¹. Accordingly, methane yield was reaching a mean of 4424 m³ ha^-1 and a maximum of 4812 m³ ha^-1. No correlations between content of crude nutrients or cell-wall fractions and specific gas or methane yield were evident neither for the plant fractions nor for the whole plant. In conclusion, harvesting at late milk ripening was clearly superior in dry matter and methane yields although specific methane yield was higher at early heading. A selection for maximum dry matter yield in rye breeding should indirectly improve also methane yield.     

Compositional changes in industrial hemp biomass (Cannabis sativa L.) induced by electron beam irradiation Pretreatment

The effects of electron beam irradiation on chemical decomposition of industrial hemp biomass were evaluated at doses of 150, 300, and 450 kGy. The quantity of decomposed components was indirectly estimated by measuring changes in alkaline extraction. The more severe degradation of structural components induced by higher irradiation doses resulted in larger amounts of alkaline extract. Carbohydrate compositional analysis using ¹H-NMR spectroscopy was applied to quantitatively investigate changes in the polysaccharides of the industrial hemp. The xylose peak intensity in the NMR spectra decreased with increasing electron irradiation dose, indicating that xylan was more sensitive to electron beam irradiation than cellulose.     

Effects of energy conservation in major energy-intensive industrial sectors on emissions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in China

China has set an ambitious target of increasing energy efficiency by 20% and reducing pollution discharges by 10% over the period 2006–2010. Promoting advanced technologies and closing outdated facilities are widely recognized as important measures to achieve these targets. These actions can also indirectly decrease release of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). The objectives of this paper are to identify and quantify reductions of PCDD/F emissions to air due to measures such as phasing out of obsolete facilities in the four most energy-intensive industrial sectors. Reductions in PCDD/F emissions from power generation were estimated to be 7, 33 and 38 g I-TEQ in 2006, 2007 and 2008, respectively. For the cement industry, reductions were estimated to be 680 g I-TEQ between 2007 and 2008, and 740 g I-TEQ between 2009 and 2010. For the iron and steel industry, the reduction was estimated to be 113.3 g I-TEQ over the period 2007–2010, which includes 76.6 g I-TEQ in 2007. For the coke industry, the reduction was estimated to be 68 g I-TEQ in 2007 and 62 g I-TEQ in 2008.     

Slow expansion and low yields of willow short rotation coppice in Sweden; implications for future strategies

About 16 000 ha of commercial willow Short Rotation Coppice (SRC) fields for production of biomass for energy were planted in the early 1990s in Sweden. The cultivated with SRC area has remained almost stable and was slightly decreased during the last years despite the incentives and predictions for drastic increases. Similar incentives and predictions in other countries have been lately launched. The bioenergy produced in the planted SRC areas in Sweden has been lower than anticipated, partly due to the lower than expected biomass yields and the termination of some willow SRC plantations. Explanations for the low yields are depicted based on analyzing the results of a survey where 175 willow SRC growers participated. Lower biomass yields are attributed to: (i) the low input in management activities; (ii) the choice of land for the willow SRC plantation; (iii) and the level of personal involvement of the farmer. Understanding the reasons to earlier years’ performance of willow SRC is important for development of better performing systems in the future, in Sweden as well as in other countries.     

Environmental impacts and energy demand of rapeseed as an energy crop in Chile under different fertilization and tillage practices

The implementation of energy crops in Chile is an option that requires prior environmental studies within the framework of a sustainable national policy of energy security. The aim of this study is to assess the environmental performance of rapeseed crop (Brassica napus L.) in Chile in view of its potential use for the production of biodiesel. Using Life Cycle Assessment (LCA), the study quantifies the energy demand and the environmental impacts associated with the main tillage systems of Chilean rapeseed production on a national level: conventional tillage and zero tillage, and with four mineral fertilisation trials on a local level (combination of N, P and K rates). In the inventory, the agricultural inputs are obtained from national sources; international databases processes are partially adapted to Chilean conditions. For the impact assessment, the CML 2 baseline 2001 method is applied. The results indicate that the two tillage systems present similar energy demand and environmental impacts profile, with the exception of the categories photochemical ozone creation and freshwater aquatic ecotoxicity. In both systems, the use of mineral fertilisers has the greatest energy demand, with a contribution of over 75%, and the greatest environmental impacts. In contrast, fungicides and seeds have a minimum contribution, all together, less than 3%. The results of LCA of fertilisation trials show that higher fertilisation rates require an increase in seed yield to compensate additional impacts and to be environmentally favourable.     

Life cycle assessment of Jatropha biodiesel as transportation fuel in rural India

Since 2003 India has been actively promoting the cultivation of Jatropha on unproductive and degraded lands (wastelands) for the production of biodiesel suitable as transportation fuel. In this paper the life cycle energy balance, global warming potential, acidification potential, eutrophication potential and land use impact on ecosystem quality is evaluated for a small scale, low-input Jatropha biodiesel system established on wasteland in rural India. In addition to the life cycle assessment of the case at hand, the environmental performance of the same system expanded with a biogas installation digesting seed cake was quantified. The environmental impacts were compared to the life cycle impacts of a fossil fuel reference system delivering the same amount of products and functions as the Jatropha biodiesel system under research. The results show that the production and use of Jatropha biodiesel triggers an 82% decrease in non-renewable energy requirement (Net Energy Ratio, NER = 1.85) and a 55% reduction in global warming potential (GWP) compared to the reference fossil-fuel based system. However, there is an increase in acidification (49%) and eutrophication (430%) from the Jatropha system relative to the reference case. Although adding biogas production to the system boosts the energy efficiency of the system (NER = 3.40), the GWP reduction would not increase (51%) due to additional CH₄ emissions. For the land use impact, Jatropha improved the structural ecosystem quality when planted on wasteland, but reduced the functional ecosystem quality. Fertilizer application (mainly N) is an important contributor to most negative impact categories. Optimizing fertilization, agronomic practices and genetics are the major system improvement options.     

A case study of energy use and economical analysis of irrigated and dryland wheat production systems

Current conventional agricultural systems using intensive energy has to be re-vitalized by new integrated approaches relying on renewable energy resources, which can allow farmers to stop depending on fossil resources. The aim of the present study was to compare wheat production in dryland (low input) and irrigated (high input) systems in terms of energy ratio, energy efficiency, benefit/cost ratio and amount of renewable energy use. Data were collected from 50 irrigated and 50 dryland wheat growers by using a face-to-face questionnaire in 2009. The results showed that the total energy requirement under low input was 9354.2 MJ ha⁻¹, whereas under high input systems it was 45367.6 MJ ha⁻¹. Total energy input consumed in both dryland and irrigated systems could be classified as direct, indirect, renewable and non-renewable energies which average in two wheat production systems were 47%, 53%, 24% and 76%, respectively. Energy ratios of 3.38 in dryland and 1.44 in irrigated systems were achieved. The benefit–cost ratios were 2.56 in dryland and 1.97 in irrigated wheat production systems. Based on the results of the present study, dry-land farming can have a significant positive effect on energy-related factors especially in dry and semi-dry climates such as Iran.     

The analysis of security cost for different energy sources

Global concerns for the security of energy have steadily been on the increase and are expected to become a major issue over the next few decades. Urgent policy response is thus essential. However, little attempt has been made at defining both energy security and energy metrics. In this study, we provide such metrics and apply them to four major energy sources in the Korean electricity market: coal, oil, liquefied natural gas, and nuclear. In our approach, we measure the cost of energy security in terms of supply disruption and price volatility, and we consider the degree of concentration in energy supply and demand using the Hirschman–Herfindahl index (HHI). Due to its balanced fuel supply and demand, relatively stable price, and high abundance, we find nuclear energy to be the most competitive energy source in terms of energy security in the Korean electricity market. LNG, on the other hand, was found to have the highest cost in term of energy security due to its high concentration in supply and demand, and its high price volatility. In addition, in terms of cost, we find that economic security dominates supply security, and as such, it is the main factor in the total security cost. Within the confines of concern for global energy security, our study both broadens our understanding of energy security and enables a strategic approach in the portfolio management of energy consumption.     

Evaluation the potential economic impacts of Taiwanese biomass energy production

The Taiwanese rice paddy land set-aside program diverts a substantial land area. Given today’s high energy prices and interests in energy security, that set-aside area could be converted to produce bioenergy feedstocks. This study evaluates the economic and environmental impacts of such a policy change using a Taiwanese agricultural sector model. The results show that such a strategy provides increased farm revenue, increased rural employment, increased energy sufficiency and reduced greenhouse gas emissions but also increased government expenditures. These outcomes indicate that the agricultural sector could play a positive role by producing renewable energy.     

Evaluation of biomass and thermal energy utilization efficiency of oilseed Brassica (Brassica juncea) under altered microenvironments

Changes in within-canopy microenvironments may significantly influence the physiological response pattern of the crop eventually influencing biomass, seed yield and their heat utilization behavior. Therefore, energy use efficiency in oilseed crop Brassica juncea was evaluated to have better understanding of impact of microenvironments on plant characteristics. Linear and non-linear regression analysis showed significant and positive response of Brassica towards time variable leaf area index (LAI), dry biomass accumulation and their heat utilization efficiencies. Linear and third order polynomial regression models indicated 81 and 94% variation in LAI and dry biomass production respectively as a function of time (t) while about 85-93% variation in thermal energy use efficiency (THUE) was observed which might be due to differential thermal heat accumulation at its various phenological stages. Its quantification was done with second order regression equations using accumulated thermal heat (TI) (R² = 0.93∗∗) and solar energy (PTI) (R² = 0.85∗∗). THUE was predicted as 0.1616 × LAI - 0.0294; R² = 0.74∗∗ using TI and 0.0179 × LAI - 0.0044; R² = 0.75∗∗ using PTI and 0.0378 + 0.0012 × (DM) -3E-07 × (DM)²; R² = 0.97∗∗ using TI and 0.0042 + 0.0001 × (DM)−3E-08 × (DM)²; R² = 0.96∗∗ using PTI. The significant changes in seed yield heat use efficiency of the order 80-87% were attributed to differential thermal energy utilization capacities. We conclude that the prediction models developed from this study could be used in predicting energy use efficiency in other related species of oilseed Brassica.     

Efficiency model for photovoltaic modules and demonstration of its application to energy yield estimation

A new method has been proposed [W. Durisch, K.H. Lam, J. Close, Behaviour of a copper indium gallium diselenide module under real operating conditions, in: Proceedings of the World Renewable Energy Congress VII, Pergamon Press, Oxford, Elsevier, Amsterdam, 2002, ISBN 0-08-044079-7] for the calculation of the annual yield of photovoltaic (PV) modules at selected sites, using site-specific meteorological data. These yields are indispensable for calculating the expected cost of electricity generation for different modules, thus allowing the type of module to be selected with the highest yield-to-cost ratio for a specific installation site. The efficiency model developed and used for calculating the yields takes three independent variables into account: cell temperature, solar irradiance and relative air mass. Open parameters of the model for a selected module are obtained from current/voltage (I/V) characteristics, measured outdoors at Paul Scherrer Institute's test facility under real operating conditions. From the model, cell and module efficiencies can be calculated under all relevant operating conditions. Yield calculations were performed for five commercial modules (BP Solar BP 585 F, Kyocera LA361K54S, Uni-Solar UPM-US-30, Siemens CIS ST40 and Wuerth WS11003) for a sunny site in Jordan (Al Qawairah) for which reliable measured meteorological data are available. These represent mono-crystalline, poly-crystalline and amorphous silicon as well as with copper–indium-diselenide, CuInSe₂ PV modules. The annual yield for these modules will be presented and discussed.     

Dynamic changes of lignin contents of MT-1 elephant grass and its closely related cultivars

Elephant grass (Pennisetum purpureum Schum.) is a tropical C₄ bunchgrass with high rates of growth and biomass production. It has been considered as a new alternative for energy crop in some countries, and expected to provide abundant and sustainable resources of lignocellulosic biomass for the production of solid biofuels. But in addition to cellulose, plant cell walls contain lignin that hinders the degradation of cell wall polysaccharides to simple sugars destined for fermentation to ethanol and biogas. In this paper, five elephant grass cultivars, such as ‘MT-1’ new line (P. purpureum cv. MT-1), ‘Mott’ (P. purpureum cv. Mott), ‘Huanan’ (P. purpureum cv. Huanan), ‘N51’ (P. purpureum cv. N51) and ‘Guimu-1’ ((Pennisetum americanum × P. purpureum) × P. purpureum cv. Guimu No.1) were tested to determine the lignin content using the acetyl bromide method. The lignin contents increased with the growth development for all five cultivars, but the increasing range was different with the difference of cultivar. In particular, the biggest increasing range was between July and August for ‘Huanan’, ‘N51’, ‘Mott’ and ‘MT-1’. At seedling stage, the contents of five cultivars were not significantly different, but the differences were demonstrated at internode elongation stage. At ripening stage, the upper internode of flowering culm had the lowest lignin content, and the basal internode had the highest content for all the five cultivars. The lignin content was very different at different development stage for different cultivars, indicating the differentiations among the five genotypes. As far as the flowering culm (in December) was concerned, the order of lignin content from the highest to the lowest was ‘Huanan’ (22.04% FW) > ‘N51’ (19.65% FW) > ‘Guimu-1’ (17.45% FW) > ‘Mott’ (15.43% FW) ≥ ‘MT-1’ (14.63% FW). In NJ and UPGMA dendrograms, the five cultivars could be divided into two groups, one for ‘MT-1’, ‘Mott’ and ‘Guimu-1’, one for ‘Huanan’ and ‘N51’. This result is consistent with the pedigree relationships among the five cultivars.     

Variation on biomass yield and morphological traits of energy grasses from the genus Miscanthus during the first years of crop establishment

This study presents the results of investigations of variation, genotype × year interactions and genotype × year × location interactions for the yield and morphological traits of several selected clones of energy grasses of the genus Miscanthus. The analyses were performed on the best clones of selected hybrid plants, which were obtained within the species M. sinensis or are the result of interspecific hybridization of M. sinensis and M. sacchariflorus. Analyses were conducted on the basis of three-year field trials at two locations. The young plants produced from in vitro cultures were planted at a density of one plant per m². The early stages of plant development, from planting until peak yield in the third year of cultivation, were analysed. Statistical analyses performed on the yield and morphological traits as well as changes in these characteristics over the successive years of the study showed considerable genotypic variation for traits under study. Moreover, significant genotype × year interactions as well as genotype × year × location interactions were observed in terms of yield and morphological traits. Based on the collective results of the study, we suggest that apart from M. x giganteus particularly hybrids of M. sinensis × M. sacchariflorus, should be taken into consideration in genetic and breeding studies on the improvement of yield from energy grasses of the genus Miscanthus.     

Environmental assessment: (LCA) and spatial modelling (GIS) of energy crop implementation on local scale

Environmental analysis tools as LCA and GIS have been combined to provide an integrated methodology able to determine suitable areas for cultivating Brassica spp. (B. carinata and B. napus) and Populus spp and for proposing local and decentralised energy production and consumption scenario. The methodology is applied and verified in a Catalonia (southern Europe) case study area but it can be extrapolated to other Mediterranean regions with similar agroclimates.The results obtained show that a high impact reduction in potential global warming category can be achieved annually (annual reduction of 1,954,904 Mg of CO₂ eq.) in a local scale scenario.Environmental integration such as GIS and LCA provide a methodology capable of giving enough information and results to determine an energy crop implementation strategy for reducing energy consumption and CO₂ eq. emissions.     

A numerical study on the effect of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames

This paper investigates the effects of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames by numerical simulation. The results reveal that flame temperature changes due to the combined effects of adiabatic temperature, fuel Lewis number and radiation heat loss, when hydrogen/reformate gas is added to the fuel of a methane/air diffusion flame. The effect of Lewis number causes the flame temperature to increase much faster than the corresponding adiabatic equilibrium temperature when hydrogen is added, and results in a qualitatively different variation from the adiabatic equilibrium temperature as reformate gas is added. At some conditions, the addition of hydrogen results in a super-adiabatic flame temperature. The addition of hydrogen/reformate gas causes NO formation to change because of the variations in flame temperature, structure and NO formation mechanism, and the effect becomes more significant with increasing strain rate. The addition of a small amount of hydrogen or reformate gas has little effect on NO formation at low strain rates, and results in an increase in NO formation at moderate or high strain rates. However, the addition of a large amount of hydrogen increases NO formation at all strain rates, except near pure hydrogen condition. Conversely, the addition of a large amount of reformate gas results in a reduction in NO formation.     

Interactions and implications of renewable and climate change policy on UK energy scenarios

As a response to the twin challenges of climate change mitigation and energy security, the UK government has set a groundbreaking target of reducing the UK’s economy-wide carbon emissions by 80% from 1990 levels by 2050. A second key UK energy policy is to increase the share of final energy consumption from renewables sources to 15% by 2020, as part of the wider EU Renewable Directive. The UK’s principle mechanisms to meet this renewable target are the Renewable Obligation (RO) in the electricity sector, the Renewable Transport Fuel Obligation (RTFO), and most recently the Renewable Heat Programme (RHP) for buildings. This study quantifies a range of policies, energy pathways, and sectoral trade-offs when combining mid- and long-term UK renewables and CO₂ reduction policies. Stringent renewable policies are the binding constraints through 2020. Furthermore, the interactions between RO, RTFO, and RHP policies drive trade-offs between low carbon electricity, bio-fuels, high efficiency natural gas, and demand reductions as well as resulting 2020 welfare costs. In the longer term, CO₂ reduction constraints drive the costs and characteristics of the UK energy system through 2050.     

Lifecycle assessment of the economic, environmental and energy performance of Jatropha curcas L. biodiesel in China

Due to issues relating to the sustainability of biofuel production, second generation biofuel has attracted much attention. As a promising feedstock of second generation biodiesel, Jatropha curcas L. (JCL) is being massively planted on marginal land in China, but its viability as a biofuel source has not been systematically assessed. This paper performed a lifecycle assessment of the economic, environmental and energy (3E) performance of the JCL biodiesel, assuming JCL oil is either used for direct blending with diesel or further processed into JCL methyl ester (JME). The results show that, at the current technical levels, the production of JCL biodiesel is financially infeasible, but has positive environmental and energy performance. Despite the additional cost incurred in the transesterification process, the net present value of JME is slightly higher than that of JCL oil when a part of the cost is allocated to the co-product, i.e., glycerin. As compared with that of diesel, the production and consumption of per liter JCL oil and JME can reduce 7.34 kg and 8.04 kg CO₂ equivalent, respectively. The energy balances of both JCL oil and JME are 1.57 and 1.47, respectively, in terms of the ratio of the heat value of biodiesel and that of energy input. The main factors affecting the 3E performance of JCL biodiesel are seed yield, co-product output, and farm energy input.     

Development of energy efficient porous medium burners on surface and submerged combustion modes

Two compact premixed LPG burners based on submerged and surface combustion modes in porous medium (abbreviated as MSB and SSB respectively) are developed and their combustion and emission characteristics are compared to those of the CB (conventional burner). The preheating and reaction zones of MSB are made from porcelain form and Alumina spheres of 30 mm size, respectively, and the corresponding zones in SSB are made from Alumina (Al₂O₃) foams of pore densities 26 ppcm and 8 ppcm. NO_x emission is reduced by 76% and 75% by the use of MSB and SSB, respectively, compared with the CB, with acceptable CO and SO₂ emissions. For a thermal load of 0.62 kW, the thermal efficiencies of CB, MSB and SSB are estimated to be 47%, 59% and 71%, respectively.