Biomass and energy production of catch crops in areas with deficiency of precipitation during summer period in central Bohemia

The biomass production dynamics of catch crops, volunteers and weeds in dependence on precipitation and air temperature, was studied in central Bohemia from 2004 to 2006. The cover of individual components of the growth was monitored during the same period. Also measured were energy and efficiency of utilization of global radiation by catch crops and volunteers. The catch crops included the following species: Brassica napus, Lolium multiflorum, Lolium perenne, Phacelia tanacetifolia, Sinapis alba, Trifolium incarnatum, Raphanus sativus var. oleiformis and Trifolium subterraneum. The highest biomass production and the highest cover of catch crops were observed in treatments with S. alba (1382.0 kg ha⁻¹, 47.8%). The average biomass production (sum of catch crops, volunteers and weeds) was highest in treatments with S. alba, R. sativus, and P. tanacetifolia and lowest in treatments with B. napus, L. multiflorum and L. perenne. It was demonstrated that an increase in the percentage share of volunteers caused a decrease in the biomass production of catch crops. The average energy production ranged from 0.31 to 2.37 MJ m⁻² in treatments with catch crops, and from 0.25 to 0.89 MJ m⁻² in treatments with cereal volunteers. The highest effectivity of global radiation utilization, was determined in treatments with S. alba (0.11-0.47%). Based on regression analysis the closest dependence between biomass production from all treatments on the experimental site and precipitation was observed from 1st May till the time of sowing and the average air temperatures from the sowing period till the time of the last biomass production assessment.     

山东省秸秆资源储量及其分布特征评价

利用文献统计、因子分析和聚类分析等方法,对山东省农作物秸秆资源量及其区域分布特点进行分析评价。结果表明,2009年全省可收集利用的秸秆资源量为5.86×107 t,其中玉米秸秆最为丰富,约占总量的47.11%,小麦秸秆、棉花秸秆分别占29.19%和14.6%。秸秆资源总量区域分布呈现自西向东递减的特征,单位播种面积资源分布呈现自北自南、自西向东递减的趋势,人均秸秆资源分布由北向南逐渐递减。利用因子分析、聚类分析方法进行综合评价,可将全省分为4个类型区:资源丰富区、资源较丰富区、资源一般区和资源不足区,整体呈现"西密东疏、西丰东贫"的资源分布特点。     

Bioethanol production from tuber crops using fermentation technology: a review

Bioethanol, an alcohol produced by fermentation of plant biomass containing starch and sugars by micro-organisms, considered as a dominant form of fuel for future. Production of this renewable fuel, especially from starchy materials such as tuber crops, holds a remarkable potential to meet the future energy demand because of its high production and comparitively less demand for use as food and fodder. This review focuses on the world bioethanol production scenario from various tuber crops, namely cassava, sweet potato, potato, yam, aroids, sugar beet, etc., fermentation techniques and micro-organisms used in fermentation process along with its future prospects. The advances in metabolic pathway engineering and genetic engineering techniques have led to the development of micro-organisms capable of efficiently converting biomass sugars into ethanol. Several biotechnological tools that are also available for the improvement of microorganisms to meet the harsh environments typically met with certain industrial fermentation process are also discussed.     

Biogas production from thermophilic codigestion of air‐dried rice straw and animal manure

In order to evaluate the effects of organic loading rate (OLR) on thermophilic codigestion of air‐dried rice straw (RS) with pig manure (PM), cow manure (CM), and chicken manure (CHM), continuous bench experiments (40 L) were carried out at OLRs of 3.0, 3.6, 4.2, 4.8, 6.0, 8.0, and 12.0 kg VS/(m³ · d). Stable biogas production without inhibition by volatile fatty acids (VFA) or ammonia and foaming was achieved at OLRs of 3–12, 3–6, and 3–4.8 for the codigestions of RS + PM, RS + CM, and RS + CHM, respectively. Maximum average volumetric biogas production rates of 4.98, 2.64, and 2.03 m³/(m³ · d) were obtained at OLRs of 12, 6, and 4.8 kg VS/(m³ · d) for the codigestions of RS + PM, RS + CM, and RS + CHM. Foaming was occurred at OLRs of 8 kg VS/(m³ · day) for the codigestions of RS + CM. The codigestion of RS + CHM was inhibited by the accumulation of ammonia instead of VFA when the OLR was ≥6 kg VS/(m³ · d). This study provided references for the engineering application of codigestion of RS and animal manure. Copyright © 2016 John Wiley & Sons, Ltd.     

Current and future financial competitiveness of electricity and heat from energy crops: A case study from Ireland

It has been demonstrated that Miscanthus and willow energy-crop cultivation could be economically competitive with current agricultural land uses at a farm-gate biomass price ranging from €70 to €130 t⁻¹ dry matter [Styles, D., Thorne, F., Jones, M.B., in review. Energy crops in Ireland: An economic comparison of willow and Miscanthus production with conventional farming systems. Biomass and Bioenergy, May 2006]. This paper uses the same farm-gate prices to calculate the economic competitiveness of energy crop electricity and heat production, using a net-present-value (NPV) approach (20-year period, 5% discount rate). Direct and gasified co-firing of willow wood with coal would result in electricity generation 30% or 37% more expensive than coal generation, at current coal and CO₂ allowance prices and a farm-gate biomass cost of €100 t⁻¹. ‘Break-even’ CO₂ allowance prices are €33 and €37 t⁻¹, respectively. However, co-firing of Miscanthus with peat is close to economic competitiveness, and would require a CO₂ allowance price of €16 t⁻¹ to break-even (against a current price of €12 t⁻¹). NPV analyses indicate that wood heat is significantly cheaper than oil, gas or electric heat, excluding existing wood-boiler installation subsidies. Discounted annual savings range from €143 compared with gas to €722 compared with electric heating at the domestic scale and from €3454 to €11,222 at the commercial scale. Inclusion of available subsidies improves the comparative economics of domestic wood heat substantially. The economic advantage of wood heat is robust to variation in fuel prices, discount rates and heat loads. The greatest obstacles to energy-crop utilisation include: (i) a reluctance to consider long-term economics; (ii) possible competition from cheaper sources of biomass; (iii) the need for a spatially coordinated supply and utilisation network.     

Life cycle assessment of different bioenergy production systems including perennial and annual crops

Energy crops are expected to greatly develop in a very short-term bringing to significant social and environmental benefits. Nevertheless, a significant number of studies report from very positive to negative environmental implications from growing and processing energy crops, thus great uncertainty still remains on this argument. The present study focused on the cradle-to-grave impact assessments of alternative scenarios including annual and perennial energy crops for electricity/heat or first and second generation transport fuels, giving special emphasis to agricultural practices which are frequently surprisingly neglected in Life Cycle Assessment studies despite a not secondary relevance on final outcomes. The results show that cradle-to-farm gate impacts, i.e. including the upstream processes, may account for up to 95% of total impacts, with dominant effects on marine water ecotoxicity. Therefore, by increasing the sustainability of crop management through minimizing agronomic inputs, or with a complementary use of crop resides, can be expected to significantly improve the overall sustainability of bioenergy chains, as well as the competitiveness against fossil counterparts. Once again, perennial crops resulted in substantially higher environmental benefits than annual crops. It is shown that significant amount of emitted CO₂ can be avoided through converting arable lands into perennial grasslands. Besides, due to lack of certain data, soil carbon storage was not included in the calculations, while N₂O emission was considered as omitted variable bias (1% of N-fertilization). Therefore, especially for perennial grasses, CO₂ savings were reasonably higher that those estimated in the present study. For first generation biodiesel, sunflower showed a lower energy-based impacts than rapeseed, while wheat should be preferred over maize for first generation bioethanol given its lower land-based impacts. For second generation biofuels and thermo-chemical energy, switchgrass provided the highest environmental benefits. With regard to bioenergy systems, first generation biodiesel was less impacting than first generation bioethanol; bioelectricity was less impacting than first generation biofuels and second generation bioethanol by thermo-chemical hydrolysis, but highly impacting than Biomass-to-Liquid biodiesel and second generation bioethanol through enzymatic hydrolysis.     

Production and quality analysis of pellets manufactured from five potential energy crops in the Northern Region of Costa Rica

Modifications to a pellet manufacturing process must be made based on the characteristics of raw material used. The purpose of this work was to determine the alternations required to a wood pellet manufacturing process and the quality of the pellets produced using this process from five energy crops. Quality measurements include: the caloric value, the loss of moisture content in each production stage, the efficiency index of particle-pellet, ash content and quality as defined using the quantity of cracks and the transversal density and longitudinal density determined using X-ray radiography. The crops analyzed were rhizomatous plants, with caloric values ranging between 17.1 and 20.3 MJ kg⁻¹. This work determined that it was possible to produce pellets with Gynerium sagittatum and Phyllostachys aurea using the same production process for wood; however, Arundo donax and Pennisetum purpureum needed pre-air-drying and the Sorghum bicolor required mechanical dewatering before drying. A. donax, P. purpureum and G. sagittatum provided the highest efficiency index. When evaluating the pellet quality P. aurea and G. sagittatum hard a large quantity of cracks, unlike A. donax, P. purpureum and S. bicolor. The transversal and longitudinal pellet density varied from 1129 to 1294 kg m⁻³. The highest values of bulk density were obtained in A. donax and P. purpureum, followed by G. sagittatum and P. aurea, and the lowest bulk density was obtained in S. bicolor. Althogh out, some species produced cracks and high ash content, this work demonstrated that it is possible to produce pellets with moderate quality.     

Biological hydrogen production from steam-exploded straw by simultaneous saccharification and fermentation

Hydrogen was produced by simultaneous saccharification and fermentation from steam-exploded corn straw (SECS) using Clostridium butyricum AS1.209. Effect of various process parameters, such as solid to liquid ratio, enzyme loading and initial pH, etc., were examined with respect to maximum hydrogen productivity which was obtained by fitting the cumulative hydrogen production data to a modified Gompertz equation. Maximum specific hydrogen production rate and maximal hydrogen yield were 126 ml/g VSS d and 68 ml/g SECS, respectively. The yield of soluble metabolites was 197.7 mg/g SECS. Acetic acid accounted for 46% of the total was the most abundant product and this shows that hydrogen production from SECS was essentially acetate-type fermentation. Hydrogen production by simultaneous saccharification and fermentation of SECS has the predominance of short lag-stage and high maximum specific hydrogen production rate and it was a promising method for hydrogen production and straw biomass conversion.     

Energy crops and pesticide contamination: Lessons learnt from the development of energy crop cultivation in Germany

Biomass provides two thirds of the total energy produced from renewables in Europe. The share of bioenergy from energy crops is growing rapidly. Given the environmental pressures arising from pesticide pollution from current agricultural food production, a substantial increase in energy crop cultivation might put additional pressure on biodiversity and soil and water resources. In the present study, we examine the potential of energy crops for pesticide contamination and develop general conclusions and recommendations for the future large-scale expansion of agricultural bioenergy. We base our analysis on the development of energy crop cultivation in Germany, the European country with the largest share of energy crops. Our findings reveal that there will not necessarily be an increase or decrease in the amounts of pesticides released into the environment. Due to the great variety of energy crops, the potential effects will depend rather on the future design of the agricultural systems. Possible risks are associated with the increased cultivation of pesticide-intensive energy crops, such as rapeseed, especially when grown in monocultures or on formerly set-aside land or converted grassland. Instead, energy crops should be integrated into the existing food production systems. Financial incentives and further education are needed to encourage the use of sustainable crop rotations, innovative cropping systems and perennial energy crops, which may add to crop diversity and generate lower pesticide demands than intensive food farming systems. Optimised cultivation systems with diverse crop rotations could help to improve monotonous agricultural landscapes, increase biodiversity and minimise pesticide exposure.     

Evaluation of methane production from maize silage by harvest of different plant portions

Biogas production is mainly based on the anaerobic digestion of cereals silages and maize silage is the most utilized. Regarding biogas production, the most important portion of the plant is the ear. The corn ear, due to high starch content, is characterized by a higher biogas production compared to the silage of the whole plant.In this paper, we present the results of experimental field tests carried out in Northern Italy that aim to evaluate the anaerobic methane potential (BMP) of different portions of ensiled maize hybrids. The BMP production is evaluated considering the possibility of harvesting and ensiling: the whole plant; the plant cut at 75 cm of height; the ear only; the plant without the ear. For the different solutions, the results are reported as specific BMP and as average biogas production achievable per hectare. The methane production by harvesting and ensiling the whole plant (10,212 and 10,605 m³ ha⁻¹, for maize class 600 and 700, respectively) is higher than the ones achievable by the other plant portions (7961 and 7707 m³ ha⁻¹, from the ear; 9523 and 9784 m³ ha⁻¹, from the plant cut at 75 cm; 3328 and 3554 m³ ha⁻¹, from the plant without the ear, for maize class 600 and 700, respectively). The harvest of the whole plant, although it is the most productive solution, could not be the best solution under an economic and environmental point of view. Harvesting only the ear can be interesting considering the new Italian subsidy framework and for the biogas plants fed by biomass transported over long distances.     

Development of a method for biohydrogen production from wheat straw by dark fermentation

Lignocellulosic biomass contains approximately 70-80% carbohydrates. If properly hydrolyzed, these carbohydrates can serve as an ideal feedstock for fermentative hydrogen production. In this research, batch tests of biohydrogen production from acid-pretreated wheat straw were conducted to analyze the effects of various associated bioprocesses. The objective of the pretreatment phase was to investigate the effects of various sulfuric acid pretreatments on the conversion of wheat straw to biohydrogen. When sulfuric acid-pretreated solids at a concentration of 2% (w/v) were placed in an oven for 90 min at 120 °C, they degraded substantially to fermentative gas. Therefore, wheat straw that is pre-treated under the evaluated conditions is suitable for hydrolysis and fermentation in a batch test apparatus. Five different conditions were evaluated in the tests, which were conducted in accordance with standard batch test procedures (DIN 38414 S8): fresh straw, pre-treated straw, supernatants derived from acid hydrolyzation, Separate Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF). The SSF method proved to be the most effective and economical way to convert wheat straw to biohydrogen. The hydrogen yield by this method was 1 mol H₂/mol glucose, which resulted from 5% carbon degradation (η_{C, gas}) or the equivalent of 64% of the hydrogen volume that was produced in the reference test (glucose equivalent test). This method also proved to have the shortest lag phase for gas production. The supernatants derived from acid hydrolysis were very promising substances for continuous tests and presented excellent characteristics for the mass production of biohydrogen. For example, a 1.19 mol H₂/mol glucose (76% glucose equivalent) yield was achieved along with a 52% carbon degradation.     

Biogas production from reed biomass: Effect of pretreatment using different steam explosion conditions

Biogas production often competes with food and feed production for the raw materials and cropland required for cultivation. Common reed offers an alternative source of biomass for biogas production, alleviating this conflict. Effective microbiological conversion of this type of lignocellulosic biomass requires a pretreatment process. This study aims to determine the specific methane yields of steam-exploded reed as well as to identify how pretreatment conditions influence its physico-chemical characteristics. For this purpose, reed was pretreated with steam explosion at severity factors ranging from 2.47 to 4.83. The effects on methane yields were analyzed in batch experiments. Scanning electron microscopy (SEM) images were captured and detailed chemical analyses of the substrates carried out. Results show that the digestibility of reed biomass improved remarkably after pretreatment. Compared to the untreated sample, steam explosion increased the specific methane yield up to 89% after pretreatment at 200 °C for 15 min. However, methane yield decreased under harsher conditions, which may be due to the formation of degradation compounds during the pretreatment.     

底物质量浓度对玉米秸秆同步糖化生物制氢的影响

利用HAU-M1光合细菌对玉米秸秆同步糖化生物制氢工艺进行实验研究,提出了同步糖化生物制氢工艺中玉米秸秆底物质量浓度与pH值、还原糖质量浓度、氢气体积分数和累积产氢量等因素之间的相关关系,探讨了底物质量浓度对玉米秸秆同步糖化生物制氢工艺的影响规律。实验结果表明:当玉米秸秆底物质量浓度为25g/L时,玉米秸秆同步糖化生物制氢工艺的累积产氢量达到最高,为186mL;当玉米秸秆底物质量浓度为15g/L时,玉米秸秆同步糖化生物制氢工艺的氢气体积分数达到最高,为48%;玉米秸秆同步糖化制氢工艺的产氢高峰期为12~48h,48h后逐渐停止产氢,可为进一步优化和完善以生物质为基质的同步糖化生物制氢工艺理论与技术提供科学参考。     

Hydrogen production from steam gasification of corn straw catalyzed by blast furnace gas ash

A lab scale gasifier was built to perform the gasification experiment. The effects of temperature and steam flow on the process were investigated, and the effects of the addition of blast furnace gas ash (BFGA) on product composition, the value of H₂/(CO + CO₂), the lower heating value (LHV) of product gas, and productivity are summarized. The experimental results clearly indicate that the addition of BFGA in the steam gasification of corn straw pellets effectively enhances the ability of the downdraft gasifier to produce hydrogen-rich gas. Compared with the non-catalytic gasification process, the addition of BFGA promotes the formation of H₂, inhibits the generation of methane, CH₄, and other hydrocarbon gases, C_nH_m, and increases the H₂/(CO + CO₂) ratio. Unlike the process without the BFGA, the LHV of the product gas with BFGA increases with increasing temperature. When the water vapor volume was 0.75 kg/h, the gas production rate was the same at 850 °C with BFGA and at 950 °C without ash gas. The addition of BFGA clearly leads to a significant improvement in the ability of gasifiers to produce hydrogen-rich gas.     

Energy and economic analysis of traditional versus introduced crops cultivation in the mountains of the Indian Himalayas: A case study

This study analyzed the energy and economics associated with cultivation of traditional and introduced crops in the mountains of the Central Himalaya, India. The production cost in terms of energy for introduced crops such as tomato (Lycopersicon esculentum) and bell pepper (Capsicum annuum) cultivation was 90,358–320,516 MJ ha⁻¹ as compared to between 19,814 and 42,380 MJ ha⁻¹ for traditional crops within Himalayan agroecosystems. For the introduced crops, high energy and monetary input was associated with human labor, forest resources, chemical fertilizer and pesticides. However, energy threshold/projection for farmyard manure in traditional crop cultivation was 80–90% of the total energy cost, thus traditional crop cultivation was more efficient in energy and economics. During the study, the farm productivity of introduced crops cultivation declined with increasing years of cultivation. Consequently, the energy output from the system has been declining at the rate of −y20,598 to y20,748 MJ ha⁻¹ yr⁻¹ for tomato and y12,072 to y15,056 MJ ha⁻¹ yr⁻¹ for bell pepper under irrigated and rain-fed land use in the mountains, respectively. The comparative analysis on this paradigm shift indicates that more research is needed to support sustainable crop cultivation in the fragile Himalayan environment.     

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.     

Determination of biomass accumulation in mixed belts of Salix,Corylus and Alnus species in combined food and energy production system

Given the energetic, demographic and the climatic challenges faced today, we designed a combined food and energy (CFE) production system integrating food, fodder and mixed belts of Salix, Alnus and Corylus sp. as bioenergy belts. The objective was to assess the shoot dry weight-stem diameter allometric relationship based on stem diameter at 10 (SD₁₀) and 55 cm (SD₅₅) from the shoot base in the mixed bioenergy belts. Allometric relations based on SD₁₀ and SD₅₅ explained 90–96% and 90–98% of the variation in shoot dry weights respectively with no differences between the destructive and the non-destructive methods. The individual stool yields varied widely among the species and within willow species with biomass yield range of 37.60–92.00 oven dry tons (ODT) ha⁻¹ in 4-year growth cycle. The biomass yield of the bioenergy belt, predicted by allometric relations was 48.84 ODT ha⁻¹ in 4-year growth cycle corresponding to 12.21 ODT ha⁻¹ year⁻¹. The relatively high biomass yield is attributed to the border effects and the ‘fertilizing effect’ of alder due to nitrogen fixation, benefitting other SWRC components. On termination of 4-year growth cycle, the bioenergy belts were harvested and the biomass yield recorded was 12.54 ODT ha⁻¹ year⁻¹, in close proximity to the biomass yield predicted by the allometric equations, lending confidence and robustness of the model for biomass yield determination in such integrated agro-ecosystem.     

Pretreatment of straw for power production by pyrolysis and char wash

Co-firing of straw and coal in existing pulverised coal-fired boilers is an option for biomass based power generation. However, the high chlorine and potassium content of straw may cause problems. Experiments with co-combustion of straw and coal in power plants have shown that when a moderate amount of straw is applied (up to 20% on a thermal basis), the most serious problems are deactivation of SCR catalysts applied for NO reduction and deterioration of the fly ash quality caused by potassium. To prevent these problems a pretreatment process is required in which the heating value of the straw is supplied to the boiler without introducing potassium into the furnace chamber. A pretreatment process based on pyrolysis and char wash was investigated. Straw is pyrolysed at moderate temperatures at which the potassium is retained in the char. Potassium and residual chlorine are then extracted from the char by water, and char and pyrolysis gases may be co-fired with coal. Fundamental laboratory studies and technical investigations were conducted to evaluate the pretreatment concept. The investigations indicate, that the low temperature pyrolysis of straw can be performed in a circulating fluid bed reactor applying only straw and straw char as bed material. With a bed temperature of approximately 550°C no significant amount of potassium is released to the gas phase. Applying a counter current moving bed to the char potassium extraction with water will probably be advantageous.     

Improving methane content and yield from rice straw by adding extra hydrogen into a two-stage anaerobic digestion system

This study was aimed to increase both the methane content and yield from rice straw by adding extra H₂ into a two-stage anaerobic digestion system. The results showed that the efficiency of H₂ utilization was 36.43%. Of the total amount of H₂ used, 47.3% was converted to CH₄, thereby increasing the CH₄ content and yield by 45% and 101%, respectively. This conversion was performed at a H₂/CO₂ ratio of 4/1 and a recycling frequency of two times a day in an up-flow reactor (UR). Due to the different ways of CH₄ production in continuously stirred tank reactor (CSTR) and UR, ethanol and acetate were produced as intermediaries, accounting for 65% and 87% of total intermediaries, respectively. Moreover, the pH values in CSTR and UR were 6.7 and 8.1, respectively. The results of the microbial community structures showed that the archaea genera of Methanosaeta and Methanobacterium were the most dominant in CSTR, whereas, Methanosaeta was the most dominant in UR. In terms of the bacterial community, Clostridia was the most abundant class in UR. Based on the results mentioned above, it is feasible to simultaneously improve both the CH₄ content and yield from rice straw by adding extra H₂ into the two-stage anaerobic digestion system.