[en] Solar irradiance is a major environmental factor governing biological and physiological processes in a vegetation canopy. Solar radiation distribution in a canopy and its effect are three-dimensional in nature. However, most of the radiation models up to now have been one-dimensional. They can be successfully applied to large-scale studies of forest functioning. The one-dimensional modelling technique, however, does not provide adequate interpretation of small scale processes leading to forest growth. In this article we discuss a modelling strategy for the simulation of three-dimensional radiation distribution in a vegetation canopy of a small area (about 0.25–0.3 ha). We demonstrate its realisation to predict the three-dimensional radiative regime of phytosynthetically active radiation in a real coniferous stand located on hilly surroundings. Our model can be used to investigate the influence of different climatic conditions, forest management methods and field sites on the solar energy available for forest growth in small heterogeneous areas. Further, a three-dimensional process-oriented model helps to derive global variables affecting bio-physiological processes in a vegetation canopy shifting from small scale studies of the functioning of forests to regional, continental, and global scale problems. (author)

[en] Rangeland models that simulate hydrology, soil erosion and nutrient balance can be used to select management systems which maximize profits for producers while they minimize adverse impacts on water quality. Values are needed for parameters that describe the growth of invading woody species in order to allow simulation of their competition with grasses. Three attributes useful for describing and quantifying plant growth are: the potential leaf area index (LAI) or ratio of leaf area divided by ground area; the light extinction coefficient (k) that is used to calculate the fraction of light intercepted by leaves, applying Beer’s law; and the radiation-use efficiency (RUE) or amount of dry biomass produced per unit of intercepted light. Objectives in this study were to measure LAI, k, and RUE for eastern red cedar (Juniperus virginiana L.) and honey mesquite (Prosopis glandulosa Torr. var. glandulosa), without competing plants, as a first step toward simulating their growth. Seedlings were planted in the field at Temple, Texas, USA in early 1992 and kept free of competition from herbaceous plants. During 1993, 1994 and 1995 data were collected on biomass, leaf area and intercepted photosynthetically active radiation (PAR) for individual trees. Both tree species showed exponential biomass increases. At the end of the 1995 growing season, mean LAI values were 1.16 for cedar and 1.25 for mesquite. Mean k values were 0.34 for mesquite and 0.37 for cedar. Radiation use efficiency for aboveground biomass was 1.60±0.17 (mean±standard deviation) g per MJ of intercepted PAR for cedar and 1.61±0.26 for mesquite. The rapid growth in 1995 was accompanied by greater leaf area and thus greater summed intercepted PAR. These values are critical for quantifying growth of these two species. (author)

[en] Biodiesel, a non-toxic biodegradable fuel from renewable sources such as vegetable oils, has been developed in order to reduce dependence on crude oil and enable sustainable development. The knowledge of phase equilibrium in systems containing compounds for biodiesel production is valuable, especially in the purification stage of the biodiesel. Nonetheless, the refining process of biodiesel and by-products can be difficult and can elevate the production costs considerably unless it has an appropriate knowledge about the phase separation behavior. In addition, the transesterification reaction yield for producing biodiesel depends upon several operation parameters e.g. the feed molar ratio oil-to-alcohol and the temperature. These parameters were analyzed through a thermodynamic analysis by direct Gibbs energy minimization method in this paper, with the purpose of calculating the chemical and phase equilibrium of some mixtures containing compounds found in biodiesel production. For this, optimization techniques associated with the GAMS^® 2.5 software were utilized and the UNIQUAC and NRTL models were applied to represent the non-idealities of the liquid phases. Also, binary interaction parameters of studied compounds were correlated for NRTL and UNIQUAC models by using the least squares principle. The results showed that the use of optimization techniques associated with the GAMS software are useful and efficient tools to calculate the chemical and phase equilibrium by minimizing the Gibbs energy. Moreover, a good agreement was observed in cases in which calculated data were compared with experimental data. - Highlights: • Gibbs energy minimization method was employed to calculate chemical and phase equilibrium. • We perform a thermodynamic modeling in different systems for biodiesel production. • Parameters fitting of UNIQUAC and NRTL models were carried out by least square method. • Based on simulations, molar ratio of 1:6 and 1:9 at 30 °C were capable of reaching equilibrium conversions.

[en] Eighteen biochar samples were produced from the pyrolysis of Douglas fir wood (DFW), Douglas fir bark (DFB), and hybrid poplar wood (HP) at six temperatures (623, 673, 723, 773, 823 and 873 K) in a lab scale spoon reactor. Changes in the bulk composition of the biochar produced were examined by elemental and proximate analyses. The mass fraction of volatiles, oxygen and the ratios of oxygen to carbon (O/C) and hydrogen to carbon (H/C) decreased linearly with pyrolysis temperature. Surface properties of all the biochars produced (SEM morphology, CO₂ and N₂ adsorption, XPS analysis, Boehm titration, cation exchange capacity (CEC) and ζ-potential) were also studied. The removal of volatiles resulted in the gradual creation of microporosity detectable by CO₂ adsorption but which was difficult to detect with N₂ adsorption, suggesting that the chars contain micropores mostly less than 1 nm in entrance dimension. The XPS and Boehm titration confirmed that most oxygenated surface functional groups (presence of carbonyl, carboxyl and hydroxyl groups) are gradually removed as pyrolysis temperature increases. The changes in surface charge were studied by ζ-potential measurements and were found to vary directly with the content of oxygenated functional groups. Properties that depend on both surface area and the surface oxygenated functional groups, such as the cation exchange capacity, showed a more complex behavior. The composition of the ash and associated properties such as pH and electric conductivity (EC) were also measured. The total alkaline content increases with pyrolysis temperature leading to higher pHs and ECs. - Highlights: • Biochar surface increases gradually with pyrolysis temperature. • Small pore size in biochars produced below 500 °C cannot be studied by N₂ adsorption. • Biochars produced below 500 °C should be analyzed by CO₂ adsorption. • Oxygen bulk and surface content decreases linearly with pyrolysis temperature. • Biochars with high surface oxygen content are more negatively charged.

[en] Growing biomass crops for energy production on low productivity lands not used for food production has been suggested as an alternative to reduce dependence on fossil fuels and to mitigate greenhouse gas emissions from transportation fuel. Switchgrass is considered a potential feedstock in various states, including Tennessee, given its high biomass content in a wide range of environments. However, its low density relative to energy value and resulting high logistics costs impede the profitability of switchgrass-based bioenergy. The objective of this study is to determine the optimal logistics configuration for a collection/distribution hub to market Tennessee-produced switchgrass for bioenergy production. A mathematical programming model integrated with a geographic information system is used to maximize the net present value of profit from a hub that serves switchgrass producers and bioenergy markets. Six logistics configurations delivering switchgrass to local or international bioenergy markets are evaluated. The results highlight the economic challenges of penetrating energy markets for a switchgrass collection/distribution hub – only one logistics configuration that targets the local market is profitable. However, serving local and international markets becomes more feasible as investment risk declines. The results imply that a clear direction for national bioenergy policy is crucial to developing a biomass feedstock for the U.S. bioenergy industry. - Highlights: • We study the economics of supplying Tennessee-produced switchgrass for bioenergy. • Six switchgrass logistics pathways proposed by a collection hub are evaluated. • Only one logistics configuration that targets the local market is profitable. • Serving international markets becomes more feasible as investment risk declines.

[en] This study examined the diverse environmental impacts of domestic biogas technology in rural Ethiopia. It employed a cross-sectional survey approach involving a total of 358 sample biogas-user and non-user households. The results of the analyses showed that the substitution of traditional biomass fuels and kerosene with biogas energy enabled the biogas-user households to reduce greenhouse gas (GHG) emissions on average by about 1.9 t of CO₂ equivalents per digester per year. The reduced use of chemical fertilizer also assisted GHG emission reductions. Moreover, the technology helped in reducing depletion of woody biomass through improving efficiency of energy use and energy substitutions. It assisted in improving the fertility of soil via reducing biomass removals as fuel and the direct use of nutrient enriched bio-slurry. Furthermore, the reduced biomass removals contributed to carbon sequestration. To further enhance the diverse environmental benefits of the technology, proper and uninterrupted operation and utilization of the biogas technology should be ensured; skillful and standby biogas technicians should be present at reasonable distances to provide maintenance and aftersales services. An operational platform for joint stakeholders' actions should also be in place to assist in exploiting its full potential, and seeking and realizing the carbon reduction financial incentive for the households. - Highlights: • We studied the environmental benefits of biogas technology in rural Ethiopia. • The use of the technology assisted in reducing emissions of greenhouse gases. • The technology also helped in reducing depletion of woody biomass. • Reduced biomass removals and use of bio-slurry helped improving the soil fertility. • Ensuring proper and sustained operation can enhance its diverse eco-benefits.

[en] Occurrence of calcium oxalate (CaC₂O₄ – CaOX) crystals has been observed in more than 215 plant families. However, very little is known about the effects of calcium oxalate on biomass pretreatment and saccharification. Agave bagasse (AGB) was used as a model material due to its natural high levels of CaOX. To understand the physicochemical changes in function of biomass pretreatment, both raw AGB and CaOX-extracted agave bagasse (EAB) were subjected to ionic liquid (IL) with 1-Butyl-3-methylimidazolium chloride [C₄C₁Im][Cl] and alkaline hydrogen peroxide (AHP) pretreatments. Physicochemical changes were monitored by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and wet chemistry methods. Results show that free CaOX crystals affected negatively (by ca 39%) the saccharification of AHP-pretreated EAB compared to AGB. On the other hand, IL pretreatment achieved higher sugar yield (7.8 g dm⁻³) and lower crystallinity (14%) with EAB than for AHP (5.4 g dm⁻³ and 29%, respectively). - Highlights: • Calcium oxalate (CaC₂O₄ – CaOX) effects on biomass pretreatment is assessed. • Agave bagasse (AGB) and CaOX-extracted agave bagasse (EAB) were used as models. • Ionic liquid (IL) pretreatment with EAB produce a high sugar yield (7.8 g dm⁻³). • Alkaline hydrogen peroxide (AHP) and IL removed lignin from untreated samples. • AHP-pretreated AGB produced less sugars than EAB due to free CaOX crystals.

[en] Several European policies have been designed over the last decades to address the challenge of climate change and several measures have been put in place to accelerate the development and deployment of cost-effective low carbon technologies. The domestic nature of the resource and its great potential availability in Europe make biomass conversion technologies relevant mitigation options to be considered. In this context, the project “Logistics for Energy Crops Biomass (LogistEC)” aims to develop new or improve technologies of biomass logistics chain. In this project, the sustainability of different types of biomass is analysed in terms of environmental, economic and social impacts, based on the supply chain of two existing plants. The objective of this paper is to present the main results obtained in the socio-economic analysis of the French case and its climate change consequences. The Input-Output Analysis (IOA) has been seen as the most appropriate method to estimate these impacts using a Multiregional Input-Output Table from the World Input-Output Database project. Socio-economic effects have been estimated in terms of additional economic activity, added value and job creation. By extending the IOA with environmental accounts, greenhouse gas (GHG) emissions have also been estimated. Additionally, the most stimulated sectors have been identified. Results highlight the importance of biomass at a national level. - Highlights: • Miscanthus is a promising grass from the bioenergy perspective. • This work shows socio-economic and environmental consequences of pellets, chips and bales production of miscanthus in France. • MRIO analysis estimates value added, job creation and GHG emissions, identifying countries and sectors that will be affected.

[en] In order to meet the legislative demands of new energy policy, investment in anaerobic digestion and biogas production has increased in recent years, making it a versatile and fully established technology. So as to remain competitive, anaerobic digestion should be optimized not only at the level of the process, but also down and upstream, in which biomass storage prior to digestion is included. Ensiling is a commonly used and promising techniques to store wet biomass before anaerobic digestion. This article reviews the crucial parameters for ensiling agricultural wastes and crops for biogas production, as source properties, storage management and duration, temperature or additives. According to the reported findings in the bibliography, feedstock and its biochemical characteristics will define the course of ensiling and the impact of other parameters during storage as well. Good silage preservation will occur for feedstocks with low moisture content, high accessible carbohydrates and low buffering capacity. High packing density and reduced particle size will contribute to minimize energy losses during ensiling. Additives are widely used but are not always an asset for methane potential conservation and their application should be more appropriate for poorly ensilable biomass. Finally, evidences suggest that under specific conditions, ensiling may increase methane potential despite non-negligible organic matter losses during storage. Exposing the answers given by the literature in terms of impact of different conditions in the course of ensiling and the questions still unresolved, this article highlights the good management practices of substrates for biogas production. - Highlights: • Biochemical properties of feedstock will define the course of ensiling. • Good preservation requires low silage moisture, high water-soluble carbohydrates content and low buffering capacity. • High packing density and reduced particle size minimize energy losses. • Additives should be a potential asset for preservation of poorly ensilable biomass. • Ensiling may be used as methane potential booster before anaerobic digestion.

[en] This paper focuses on the production of furfural from a simulated kraft dissolving pulp mill pre-hydrolysate solution that is rich in pentoses. Presently, this stream at the mill is mixed with the black liquor and then burned to recover some of the energy needed for the process. However, this pre-hydrolysate would have a higher potential if used as a feedstock for furfural production. This work demonstrates a novel approach to produce furfural in high yields by adding the catalyst only when the desired reaction temperature is reached, and by removing the furfural as soon as it is generated in the reactor. By applying this concept on the pre-hydrolysate, a furfural yield of 76% can be obtained at 240 °C and 2.5 kg m⁻³ of sulfuric acid. In other approaches where the acid is initially mixed with the pre-hydrolysate, furfural yield varies between 54 and 65% depending on whether furfural is left in the reaction medium or removed as it is formed, respectively. Maximization of furfural production has also been studied in this work by varying the sulfuric acid dosage (1–5 kg m⁻³) and the reactor temperature (160–260 °C). The highest furfural yield of 77.6% can be obtained when a sulfuric acid concentration of 3.6 kg m⁻³ and a temperature of 240 °C are used for the pre-hydrolysate solution. When lignin is removed from the pre-hydrolysate prior to furfural production, the highest furfural yield is 72.6% at 220 °C and 3.6 kg m⁻³ of sulfuric acid. - Highlights: • The timing of catalyst introduction affects significantly the furfural yield. • The recovery of furfural as soon as it is produced positively affects the furfural yield. • The furfural yield is negatively affected by the presence of lignin. • The furfural yield is higher using the pre-hydrolysate than that using synthetic solution of xylose.