Residential use of firewood in Northern Sweden and its influence on forest biomass resources

Firewood is society’s oldest source of household energy and is still extensively used around the world. However, little is known about firewood usage in technologically advanced countries with high energy consumption. Some key issues include quantities of firewood currently used and future trends, as well as the influence of this usage on available biomass resources. This study addresses those issues through a postal questionnaire to 1500 of the firewood using households in a region in Northern Sweden. One-third of households produced 11-20 solid m³ of firewood per year. Three-fourths expected their production to be unchanged or increase during the coming five years. A large proportion of young producers indicated long-term continuation of firewood usage. Half (53%) of the firewood producing households owned forest and thereby had free access to wood. Produced firewood volume corresponded to 4-8% of the region’s roundwood volume harvested for industrial purposes. The use of firewood is suggested to influence decisions of private forest owners about management and harvest of forest biomass, and, thus, affect supply for bioenergy and other uses. With further incorporation of firewood usage into forest biomass management regimes, larger biomass quantities are likely to be available for industrial uses.     

Growing trade of bioenergy in the EU: Public acceptability, policy harmonization, European standards and certification needs

Since 2000, the consumption of bioenergy in the European Union has grown, along with a concurrent growth in the trade of biomass for energy purposes (though traded volumes still remain small). Bioenergy production and trade will likely continue to increase into the future, driven by climate change concerns, emissions reduction targets, increasing concerns about domestic energy security and favourable policies. The harmonization of European standards and the development of certification systems are key issues to resolving potential negative effects of increased biomass trade. Certification systems not only address the issue of environmental sustainability from production to end-use, but also allow for product differentiation while adding value to sustainably produced products, which can ultimately enhance a competitive and sustainable bioenergy market. In addition to analyzing bioenergy trade growth in the European Union, a questionnaire survey of 92 bioenergy experts from eight member states within the European Union was conducted. Survey results show that bioenergy is highly accepted in the European Union but that there is a lack of European standards and policy harmonization, along with the absence of a competitive market or a certification system, all of which are necessary for sustainable production and trade of bioenergy. A large majority (63 percent) of the total respondents agreed that the certification of bioenergy is necessary to promote the sustainable use of biomass.     

Converting Eucalyptus biomass into ethanol: Financial and sensitivity analysis in a co-current dilute acid process. Part II

The technical and financial performance of high yield Eucalyptus biomass in a co-current dilute acid pretreatment followed by enzymatic hydrolysis process was simulated using WinGEMS^® and Excel^®. Average ethanol yield per dry Mg of Eucalyptus biomass was approximately 347.6 L of ethanol (with average carbohydrate content in the biomass around 66.1%) at a cost of $0.49 L⁻¹ of ethanol, cash cost of ∼ $0.46 L⁻¹ and CAPEX of $1.03 L⁻¹ of ethanol. The main cost drivers are: biomass, enzyme, tax, fuel (gasoline), depreciation and labor. Profitability of the process is very sensitive to biomass cost, carbohydrate content (%) in biomass and enzyme cost. Biomass delivered cost was simulated and financially evaluated in Part I; here in Part II the conversion of this raw material into cellulosic ethanol using the dilute acid process is evaluated.     

Experimental study about the effects of disc chipper settings on the distribution of wood chip size

Nowadays wood should be of principal sources of biomass. This wood is transformed into chips in order to increase automatic operations and to decrease the technical effort needed at the energy conversion plant. Typical high quality chips, which are used to feed small woodchip boilers, vary in size from 10 × 10 × 5 mm to 15 × 15 × 8 mm. Chips that are relatively square and flat are easily conveyed, augured, and fed into the system smoothly. We are mainly interested in the raw material of inferior quality. A disc chipper test bench was constructed in our laboratory to study the chipping process in cutting conditions which are similar to those used in the industry. The test bench design allows many factors to be varied include cutting speed, feed per tooth, cutting angles, anvil height and cutting direction. In this paper, we attempt to understand the effect of several factors on chip size distribution. Four feeds per tooth, four cutting angles, two sharpness angles and three cutting speeds were chosen to cut wet logs of oak and fir wood, while the other factors remained constant. The results are similar for both oak and fir. The proportion of small chips decreases when we increase the feed per tooth, the cutting angle and the sharpness angle, whereas it increases when the cutting speed is increased. The feed per tooth and the cutting speed have a linear effect on the variations in the size distribution, while the cutting angle has a non-linear effect on these variations.     

Economics of herbaceous bioenergy crops for electricity generation: Implications for greenhouse gas mitigation

This paper examines the optimal land allocation for two perennial crops, switchgrass and miscanthus that can be co-fired with coal for electricity generation. Detailed spatial data at county level is used to determine the costs of producing and transporting biomass to power plants in Illinois over a 15-year period. A supply curve for bioenergy is generated at various levels of bioenergy subsidies and the implications of production for farm income and greenhouse gas (GHG) emissions are analyzed. GHG emissions are estimated using lifecycle analysis and include the soil carbon sequestered by perennial grasses and the carbon emissions displaced by these grasses due to both conversion of land from row crops and co-firing the grasses with coal. We find that the conversion of less than 2% of the cropland to bioenergy crops could produce 5.5% of the electricity generated by coal-fired power plants in Illinois and reduce carbon emissions by 11% over the 15-year period. However, the cost of energy from biomass in Illinois is more than twice as high as that of coal. Costly government subsidies for bioenergy or mandates in the form of Renewable Portfolio Standards would be needed to induce the production and use of bioenergy for electricity generation. Alternatively, a modest price for GHG emissions under a cap-and-trade policy could make bioenergy competitive with coal without imposing a fiscal burden on the government.     

Predictive models for dry weight estimation of above and below ground biomass components of Populus deltoides in India: Development and comparative diagnosis

This article concentrates on development of statistical models for prediction of biomass components (above and below ground) of standing trees of Populus deltoides. Twenty seven trees (three each from age one to nine years) were destructively harvested, separated, sorted, sub-sampled, dried to constant weight at 60 °C and weighted for biomass components (leaf, twig, branch, bole, stump root, lateral root, fine root). Harvesting in a similar manner, was continued annually up to nine years of tree age and thus in all 27 sampled trees were available for analysis and fitting of models. Diameter at breast height (dbh) alone was a very good predictor of dry weight and accordingly the height was not included in the model. Various functions viz (linear, allometric, logistic, gompertz and chapman-richards), were attempted for dry weight estimation. The linear model, though easiest to fit, suffered from the ‘negative estimation problem’, specifically for the lower range of explanatory variate. Of the remaining non-linear models, the allometric model outperformed the others on the basis of validation criterions. The value of R² ranged from 0.95 to 0.99, for the allometric models fitted on various biomass components. The proposed models can be used for prediction of component wise dry biomass of P. deltoides for a wide range of dbh values (1-50 cm) at one end and can also help farmers in the choice of economical harvest rather than the traditional physical rotation. In addition, they can be used in carbon sequestration studies, which needs complete biomass estimation.     

Characterisation of the torrefaction of beech wood using NIRS: Combined effects of temperature and duration

A new approach is proposed to retrace the combined effects of temperature and duration within the thickness of heat-treated Fagus sylvatica wood. Torrefaction is a mild pre-treatment of biomass carried out at 200-300 °C to improve its properties for pulverized systems such as gasification. The properties of wood treated at high temperature are closely related to chemical modifications induced by temperature levels and treatment duration. This study involved the spectral analysis of solid wood in the near infrared range with the aim of developing a predictive model for process assessment. Samples of beech wood were used for calibration under high temperature conditions of 220, 250 and 280 °C for 1 and 8 h. For prediction, a 50-mm thick solid piece of wood was treated at 250 °C for 3 h. It was demonstrated that it is possible not only to distinguish between wood samples that have undergone different heat treatments, but also to retrace the thermal history of a piece of wood. Statistical processing showed the compensatory effects of temperature and duration, along with the existence of an exothermal reaction in the solid piece of wood. It should thus be possible to ensure cheaper and faster quality control in continuous torrefaction processes.     

Recovery rates of logging residue harvesting in Norway spruce (Picea abies (L.) Karsten) dominated stands

A significant amount of logging residues is available for recovery in clear-cut areas. The forest residues’ potential has usually been estimated using biomass models. In Norway spruce (Picea abies) dominated stands, a large share of material is left on site especially due to dropping of needles as residues are left on site to dry in small heaps. In this study, we compared the measured dry weight of logging residues at a power plant with the potential biomass estimations made at a stand level. The study was performed in eight Norway spruce dominated stands, three of which were located in eastern Finland (North Karelia region) with the remainder being in Central Finland. The dry weights of branches, needles and stem tops were estimated using biomass models developed for individual trees by Repola et al. [1]. These dry weights were also compared with Swedish biomass models produced by Marklund [2]. The diameter and tree height information of each harvested tree served as input data in these model-based computations. Tree diameter information was obtained straight from the harvester’s stem value files, while the height information was obtained from models using the data from the stem value files as input. Inventory data before logging was used as a control material for harvester based estimates to spot possible measurement errors on the harvester measurement data. In addition, inventory data were used to get the crown height information, which was not available in the harvester measurement data. It was found that the average recovery rate was approximately 62% when applying Repola’s et al. [1] models and 61% when applying Marklund’s [2] models. However, variation between the logging sites was high. According this study, at least a third of the residues remains on the logging site if they are seasoned during the spring and summertime in small heaps.     

Wood fuel trade in European Union

Wood fuels are the most important alternatives of fossil fuel which is one of the reasons of the climate changes in the world and of global warming. Wood fuels, which have an important role in the cause of both providing energy requirement of production units and heating for household and healing energy deficit, disperse very less CO₂ than fossil fuels to atmosphere. Bio-fuels are used to provide energy requirement among EU countries like using in lots of developed countries. Resources having by lots developed countries and EU countries are not at enough level for bio-fuels. For this reason, trade of bio-fuels has been become in an important situation in recent years. In this study, import and export levels of bio-fuels of EU countries and Turkey, which is a candidate for union, were investigated between 2003 and 2006. The date is obtained from European Forest Institute (EFI) forest products trade flow database. As a result of the study, while rises were determined in years, it is determined that the most important exporters are Germany, Italy, Latvia and Poland and the most important importers are Germany, Italy, Belgium and UK. It is seen that Turkey has a low trade level in selected product groups.     

The first step towards a 100% renewable energy-system for Ireland

In 2007 Ireland supplied 96% of the total energy demand with fossil fuels (7% domestic and 89% imported) and 3% with renewable energy, even though there are enough renewable resources to supply all the energy required. As energy prices increase and the effects of global warming worsen, it is essential that Ireland begins to utilise its renewable resources more effectively. Therefore, this study presents the first step towards a 100% renewable energy-system for Ireland. The energy-system analysis tool used was EnergyPLAN, as it accounts for all sectors of the energy-system that need to be considered when integrating large penetrations of renewable energy: the electricity, heat, and transport sectors. Initially, a reference model of the existing Irish energy-system was constructed, and subsequently three different 100% renewable energy-systems were created with each focusing on a different resource: biomass, hydrogen, and electricity. These energy-systems were compared so that the benefits from each could be used to create an ‘optimum’ scenario called combination. Although the results illustrate a potential 100% renewable energy-system for Ireland, they have been obtained based on numerous assumptions. Therefore, these will need to be improved in the future before a serious roadmap can be defined for Ireland’s renewable energy transition.