Above-ground biomass functions for Scots pine in Lithuania

This study presents biomass functions applicable to Scots pine (Pinus sylvestris L.) on Arenosols in Lithuania, and exemplifies the potential biomass removal from Scots pine stands during thinnings. Scots pine is the most common tree species on Arenosols in Lithuania. Stands of ages 10, 20, 40, 50 and 65 years were chosen for the biomass study. We sampled 5 Scots pine trees per plot (in total 25 trees) that were stratified according to the basal area. The sampling was performed in April 2003, before the vegetative period. The following components of each tree were sampled for the above-ground biomass measurements: (1) 5 stem discs, (2) 1 branch with needles from each whorl and (3) 1 dead branch per tree.Observed biomasses of above-ground components were examined using a non-linear regression model, using stem diameter (D), tree height (H) and D²H as independent variables.For stemwood biomass, the best approximation was D²H. However, D²H was not the best parameter for crown biomass because it does not allow evaluation of the opposite effects of diameter and height on crown biomass. The calculations at stand level showed that crown biomass changed insignificantly with the increase in stand age. However, the total stand biomass increased with age due to the growth of the stem. The removal of all logging residues from the Scots pine stand over a 100-year rotation could increase extraction of forest fuel by 15–20% compared with conventional harvesting.     

Estimating biomass of individual pine trees using airborne lidar

Airborne lidar (Light Detection And Ranging) is a proven technology that can be used to accurately assess aboveground forest biomass and bio-energy feedstocks. The overall goal of this study was to develop a method for assessing aboveground biomass and component biomass for individual trees using airborne lidar data in forest settings typical for loblolly pine stands (Pinus taeda L.) in the southeastern United States. More specific objectives included: (1) assessing the accuracy of estimating diameter at breast height (dbh) for individual pine trees using lidar-derived individual tree measurements, such as tree height and crown diameter, and (2) investigating the use of lidar-derived individual tree measurements with linear and nonlinear regression to estimate per tree aboveground biomass. In addition, the study presents a method for estimating the biomass of individual tree components, such as foliage, coarse roots, stem bark, and stem wood, as derived quantities from the aboveground biomass prediction. A lidar software application, TreeVaW, was used to extract forest inventory parameters at individual tree level from a lidar-derived canopy height model. Lidar-measured parameters at individual tree level, such as height and crown diameter, were used with regression models to estimate dbh, aboveground tree biomass, and tree-component biomass. Field measurements were collected for 45 loblolly pine trees over 0.1- and 0.01-acre plots. Linear regression models were able to explain 93% of the variability associated with individual tree biomass, 90% for dbh, and 79–80% for components biomass.     

Carbon and nutrients of Scots pine stands on sandy soils in Lithuania in relation to bioenergy sustainability

Sustainable forestry is based on the principle that harvesting practices should avoid negative influence on soil fertility, wood production and long-term soil carbon (C) stocks. We examined C and nutrient concentrations and stocks of Scots pine (Pinus sylvestris L.) stands on Arenosols in south-western Lithuania. The stands were 10, 20, 40, 50 and 65 years of age. C concentrations were relatively constant, while the concentrations of N, P, K, Ca, Mg and S often varied between compartments and stand ages.The total aboveground stocks of nitrogen (N) were estimated to be in the range of 185–260 kg ha⁻¹, and 78–189 kg ha⁻¹ for calcium (Ca), 75–104 kg ha⁻¹ for potassium (K), 22–33 kg ha⁻¹ for phosphorus (P), 21–41 kg ha⁻¹ for magnesium (Mg) and 16–28 kg ha⁻¹ for sulphur (S). Corresponding stocks of the crown alone were 139–207 kg ha⁻¹ of N, 54–88 kg ha⁻¹ of Ca, 44–79 kg ha⁻¹ of K, 15–26 kg ha⁻¹ of P, 15–23 kg ha⁻¹ of Mg, and 11–15 kg ha⁻¹ of S. Biomass, C and nutrient stocks in the crown did not change with age, whereas the stemwood stocks increased with stand age. The total removals of C and N over a whole 100-year rotation were simulated to be 129 Mg ha⁻¹ and 449 kg ha⁻¹, respectively. An example scenario was created to compare the magnitude of potential nutrient removals with the atmospheric influx, soil stocks, and the internal litterfall flux. We suggest that intensified utilisation of these stands for bioenergy may be sustainable.     

The carbon sequestration potential of unmanaged forest stands in Finland under changing climatic conditions

Changes in stand-level carbon (C) storage and C flows in biomass, litter and soil organic matter in the humus layer were studied under current and changing climatic conditions in Finland with the help of a gan-type simulation model. The changing climate scenario assumed increases in mean annual temperature of 0.4°C per decade for the first one hundred years and 0.2°C per decade for the second hundred years. Warming was assumed to be larger during the winter than during the other seasons.

In southern Finland, the long term average (over 200 years) net forest ecosystem production (NEP) at the stand level was 0.4–1.0 Mg C/ha/a under the current climatic conditions, and 0.1–0.9 Mg C/ha/a under changing conditions, depending on the tree species. Under the climate change scenario, NEP decreased in Scots pine, Norway spruce and Pubescent birch stands, but increased in Pendula birch stands. During the first 25–50 years, however, NEP was found to be larger both in Scots pine and Pubescent birch stands. In northern Finland, the long term average NEP increaed, regardless of tree species, from 0.3–0.8 Mg C/ha/a to 0.4–1.0 Mg C/ha/a. The biggest changes took place in Norway spruce and Pendula birch stands.

During the early and late phases of stand development, the stands were C sources, since emissions from decaying litter and soil organic matter in the humus layer exceeded the growth of vegetation. Stands became C sources earlier under the changing climatic conditions than under the current conditions. In southern Finland, the long term average C storage was 107–201 Mg C/ha under the current climatic conditions, and 88–142 Mg C/ha under the changing conditions, depending on tree species. In northern Finland, the long term average C storage was 77–151 Mg C/ha under the current climatic conditions and 89–177 Mg C/ha under the changing conditions.     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

Aboveground tree biomass in a recovering tropical sal (Shorea robusta Gaertn. f.) forest of Eastern Ghats,India

Aboveground biomass of individual tree species by component and total biomass per unit area for four different stages of a recovering tropical dry deciduous forest stands, dominated by sal (Shorea robusta Gaertn. f.) of the Eastern Ghats, India were investigated during 2001–2002. Different periods of recovering (2, 4, 6, and 10-year) forest stands (84°13′E, 20°29′N) were selected in the Kandhamal district of Orissa, India and sample trees of all species were harvested. Tree species diversity was 23, 23, 21 and 22 in 2, 4, 6, and 10-year recovering stands, respectively. Species-wise Ixora pavetta showed the highest biomass in 2 and 4-year stands while Shorea robusta in 6 and 10-year stands. Component-wise, in all species, bole–wood contribution ranged between 22.6% and 60.9%. Aboveground tree biomass, in all the stands, was dominated by Shorea robusta, which ranged between 12.68 and 231.91 Mg ha⁻¹. Total aboveground tree biomass was 30.12, 49.21, 107.54 and 261.08 Mg ha⁻¹ in 2, 4, 6 and 10-year stands, respectively.     

生物质灰化学特性的研究

采用灰成分分析及X-ray衍射方法,对甘蔗渣、松木屑、花生壳及谷壳四种常见的生物质灰特性进行了研究。研究表明：在气化过程中,甘蔗渣和松木屑的积灰、结渣倾向严重,花生壳次之,谷壳相对轻微。对其灰中碱金属的固留研究,分析了甘蔗渣和松木屑的积灰、结渣倾向严重的原因。     

Biomass and energy production in Casuarina equisetifolia plantation stands in the degraded dry tropics of the Vindhyan plateau, India

Two age groups of Casuarina equisetifolia (Forst.) plantation stands in the Renukoot forest division of the Vindhyan plateau were investigated over the span of three years for total and component biomass, annual net primary production, energy storage and annual net energy fixation. A high range of biomass (44–81 t ha⁻¹) was recorded in a densely populated stand at ages 5–7 years in comparison to a sparsely populated stand at ages 8–10 years. The contribution of the hole component gradually increased with increasing diameter class while foliage and branch components had a large proportion of biomass in the lower diameter classes. Maximum litterfall occurred in May and foliage litter contributed 87–95% of total litterfall. The energy content and storage in component parts were higher than some other promising tree species for energy plantation in the dry tropics. Production estimates of 19–29 t ha⁻¹ yr⁻¹ showed that the performance of Casuarina is good for dry tropical conditions. The biomass accumulation ratio and production efficiency showed a significant positive and negative (logarithmic) relationship, respectively with plantation age. The energy conserving efficiency of the 5-year old stand was more than twice that of the 8-year old stand.     

Impacts of changing the minimum diameter of roundwood on the accumulation of logging residue in first thinnings of Scots pine and Norway spruce

The aim of this study was to examine the impacts of different minimum top diameters of roundwood on the accumulation of logging residue in first thinnings of Scots pine and Norway spruce. The aim was also to compare estimates of residue accumulation calculated by tree-specific models with field measurements from thinnings. Felling experiments were performed in young pine and spruce stands to evaluate the model calculations. The felling was performed by a harvester with a single-grip harvester head. Sample trees were felled and processed to a minimum diameter of 12, 10, 8 and 6 cm and the delimbed branches and stem wood between these cutting points were weighed. The mean relative masses of the tree tops of spruce were nearly doubled with each increment of 2 cm in the top diameter. Respectively in pine, the mean relative tree top mass was increased by 50-60% when the top diameter was increased by 2 cm. The mass of total residue (tree top and all delimbed branches) was similarly increased, but the differences were not as large. Compared to pine, smaller variation in the crown mass of the spruce sample resulted in a more accurate model prediction of the mass of tree tops and total residue. The results of this study suggest that the biomass quantity and distribution of a small amount of trees cannot be predicted very reliably, but when these results are generalized to stand-level, the model predictions can be improved to a practicable level.     

Emission of trace toxic metals during pulverized fuel combustion of Czech coals

A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd.     

生物质颗粒燃料灰行为研究进展

本文综述生物质颗粒燃料产业现状及生物质颗粒燃料的灰行为研究现状,分析了生物质颗粒燃料灰行为的研究前景,指出随着生物质颗粒燃料的灰行为问题的解决,生物质颗粒燃料必将成为我国未来新型能源的重要组成部分。     

Carbon stock estimates for forests in the Castilla y León region, Spain. A GIS based method for evaluating spatial distribution of residual biomass for bio-energy

Analysis of aboveground biomass and carbon stocks (as equivalent CO₂) was performed in the Castilla y León region, Spain. Data from the second and third Spanish Forest Inventories (1996 and 2006) were used. Total aboveground biomass was calculated using allometric biomass equations and biomass expansion factors (BEF), the first method giving higher values. Forests of Castilla y León stored 77,051,308 Mg of biomass, with a mean of 8.18 Mg ha⁻¹, in 1996 and 135,531,737 Mg of biomass, with a mean of 14.4 Mg ha⁻¹, in 2006. The total equivalent CO₂ in this region’s forests increased 9,608,824 Mg year⁻¹ between 1996 and 2006. In relation to the Kyoto Protocol, the Castilla y León forests have sequestered 3 million tons of CO₂ per year, which represents 6.4% of the total regional emission of CO₂. A Geographic Information System (GIS) based method was also used to assess the geographic distribution of residual forest biomass for bio-energy in the region. The forest statistics data on area of each species were used. The fraction of vegetation cover, land slope and protected areas were also considered. The residual forest biomass in Castilla y León was 1,464,991 Mg year⁻¹, or 1.90% of the total aboveground biomass in 1996. The residual forest biomass was concentrated in specific zones of the Castilla y León region, suitable for the location of industries that utilize biomass as energy source. The energy potential of the residual forest biomass in the Castilla y León region is 7350 million MJ per year.     

Primary energy and greenhouse gas implications of increasing biomass production through forest fertilization

In this study we analyze the primary energy and greenhouse gas (GHG) implications of increasing biomass production by fertilizing 10% of Swedish forest land. We estimate the primary energy use and GHG emissions from forest management including production and application of N and NPK fertilizers. Based on modelled growth response, we then estimate the net primary energy and GHG benefits of using biomaterials and biofuels obtained from the increased forest biomass production. The results show an increased annual biomass harvest of 7.4 million t dry matter, of which 41% is large-diameter stemwood. About 6.9 PJ/year of additional primary energy input is needed for fertilizer production and forest management. Using the additional biomass for fuel and material substitution can reduce fossil primary energy use by 150 or 164 PJ/year if the reference fossil fuel is fossil gas or coal, respectively. About 22% of the reduced fossil energy use is due to material substitution and the remainder is due to fuel substitution. The net annual primary energy benefit corresponds to about 7% of Sweden's total primary energy use. The resulting annual net GHG emission reduction is 11.9 million or 18.1 million tCO_2equiv if the reference fossil fuel is fossil gas or coal, respectively, corresponding to 18% or 28% of the total Swedish GHG emissions in 2007. A significant one-time carbon stock increase also occurs in wood products and forest tree biomass. These results suggest that forest fertilization is an attractive option for increasing energy security and reducing net GHG emission.     

Chemical properties of solid biofuels—significance and impact

The chemical composition of solid biofuels (as defined in [Directive 2000/76/EC of the European Parliament and of the Council on the Incineration of Waste. In: European Commission, editor. Official Journal of the European Communities, vol. L 332; 2000. p. 91–111] and [CEN/TC 335—WG2 N94. Final draft. European Committee for standardization, editor. Solid biofuels—fuel specifications and classes. Brussels, Belgium; 2003.] has manifold effects on their thermal utilisation. C, H and O are the main components of solid biofuels and are of special relevance for the gross calorific value, H in addition also for the net calorific value. The fuel N content is responsible for NO_x formation. NO_x emissions belong to the main environmental impact factors of solid biofuel combustion. Cl and S are responsible for deposit formation and corrosion and are therefore relevant for a high plant availability. Furthermore, Cl causes HCl as well as PCDD/F and S SO_x emissions and both elements are involved in the formation of aerosols (submicron particle emissions). The ash content influences the choice of the appropriate combustion technology and influences deposit formation, fly ash emissions and the logistics concerning ash storage and ash utilisation/disposal. Major ash forming elements (Al, Ca, Fe, K, Mg, Na, P, Si, Ti) are of relevance for the ash melting behaviour, deposit formation and corrosion. In addition, volatile elements such as Na and K are main constituents of aerosols. Volatile minor elements (As, Cd, Hg, Pb, Zn) play a major role in gaseous and especially aerosol emissions as well as in deposit formation, corrosion and ash utilisation/disposal. Either partly or non-volatile minor elements (Ba, Co, Cr, Cu, Mo, Mn, V) are of special relevance for ash utilisation. The present paper discusses the influence of chemical fuel properties on biomass combustion plants as well as possibilities and recommendations for controlling them.     

Bioenergy potentials of three Euphorbia species from Western Ghats in India

Bioenergy constituents of three Euphorbia species viz., Euphorbia vajravelui, E. tortilis, and E. trigona, were evaluated. These Euphorbia species showed moisture (79.5–91.9%), ash (4.06–6.80%), latex (0.08–0.26 g), oil (5.45–5.59%), polyphenol (3.12–8.39%), hydrocarbon (0.28–0.41%), carbon (42.40–44.5%), hydrogen (6.22–8.40%) contents and gross heat values (17.51–18.71 MJ/kg) comparable to other reported Euphorbia plants, energy crops and biomass sources. Thermal analyses (TG/DTG, DTA, DSC) produced comparable results. Trace elements such as Fe, Mg, K, Ca, P, Zn, Mn, Ba, Sr, Cu, Sc, and As were detected in these Euphorbia specimens. This study reveals the biomass/bioenergy potentials of these three Euphorbia species from Western Ghats, India.     

Factors affecting nonindustrial private forest landowners' willingness to supply woody biomass for bioenergy

Bioenergy is a renewable form of potential alternative to traditional fossil fuels that has come to the forefront as a result of recent concerns over high price of fuels, national security, and climate change. Nonindustrial private forest (NIPF) landowners form the dominant forest ownership group in the southern United States. These forests often tend to have large quantities of small diameter trees. Use of logging residues and non-marketable small diameter trees for bioenergy production can create economic opportunities for NIPF landowners. The results demonstrated that landowners’ willingness to harvest woody biomass was influenced by their ownership objectives, size of the forest, structure and composition of tree species, and demographic characteristics. The model found that relatively younger landowners who owned large acres of forestland with pine plantations or mix forests had the potential to become a preferable choice for contractors, extension foresters and bioenergy industries as they were more likely to supply woody biomass for bioenergy. Findings of this study will be useful to bioenergy industries, extension foresters, nonindustrial private forest landowners and policy makers.     

Element budgets of forest biomass combustion and ash fertilisation - A Danish case-study

Harvest of forest biomass for energy production may lead to a significant export of nutrients from the forest. Ash spreading and recycling of nutrients from wood chip combustion to the forest has come into focus as a means for counteracting the nutrient export. This study was carried out to examine the retention of various elements in the different ash fractions and utilise the nutrient recovery to evaluate the fertiliser quality of the examined ash. The mass and element flux of wood chips, bottom ash, cyclone fly ash and condensation sludge at Ebeltoft central heating plant was studied over a four day period in spring 2005. On average, 19 ton wood chips (dry weight) were combusted each day. The combustion of the wood chips produced 0.70% ash and sludge (dry weight). The ash and sludge dry matter was distributed as 81% fly ash, 16% bottom and residual grate ash and 3% sludge solid phase. Substantial amounts of nutrients were retained in the fly ash (P, Ca, Mg, Mn and Cu have a recovery higher than 60% and K, S and Fe have a recovery higher than 30%). The recovery of elements in the bottom ash was smaller. The added recovery of the usable fractions of ashes (both fly ash and bottom ash) exceeded 75% for the nutrients P, Ca, Mn and Mg. Both these ash fractions should be considered for fertilisation.     

Production of solid biomass and investigation of optimum thermal properties

Recognizing the fact that 5% of annual global primary production of biomass should cover 50% of the world’s current primary energy demand, plants widely available in Turkey, such as Astragalus, great mullein and sunflower, have been pelletized mixed in specific amounts to investigate their burning behaviors versus other fuels. Taguchi method was used to obtain a pelletized fuel with maximum calorie, low humidity, and low ash. Results suggested that the pellet has low humidity and ash content, while its caloric value is greater than that of the pomace, lignite, wood, sawdust, or animal and plant wastes used as fuel.     

Cumulative continuous predictions for bole and aboveground woody biomass in Eucalyptus globulus plantations in northwestern Spain

At present there is increasing interest in modelling biomass to estimate carbon sequestration or the availability of forest products for use as bioenergy. The biomass of different tree components can be estimated to provide more detailed information. However, the different components have not been clearly defined. Moreover, the greater the number of components considered, the more difficult it is to fit the system of equations with any guarantee of statistical robustness. To overcome these limitations, we developed a continuous function that predicts cumulative biomass from the stump until any top diameter (including the biomass of branches). We also used two different methods to predict bole biomass: a cumulative continuous biomass function and conversion from volume to biomass by use of a taper equation and average wood density. We used a mixed-effects modelling framework to account for correlated errors in developing the taper equation. We developed a separate equation to estimate the foliar biomass for use in estimating total aboveground tree biomass. The cumulative aboveground woody biomass equation is implicitly additive, and no heteroscedasticity was observed, thereby resolving two of the main modelling goals in the development of biomass equations. For predicting cumulative bole biomass, estimation from volume generated less error, after bias correction, than direct estimation. Moreover, the indirect method also yields useful variables such as volume and height limits. Other variables such as carbon and nutrient contents, calorific power, ash content, etc. can be estimated by multiplying the mean contents by the predicted biomass or, for more accurate predictions, by using equations based on the relative diameter.     

Allocation of five macroelements and quality of fuels derived from Norway spruce wood obtained by thinning operations

The use of forest biomass for energy production is growing in Europe and biomass energy plants market is constantly increasing. However, there is the need to define the environmental sustainability issues dealing with the emerging renewable energy scenario. In particular, the polluting emissions (i.e. PMx, NO_x and ozone) caused by the biomass combustion heavily impact on the air quality. In this context, the elemental characterization of the wood and the element allocation in the different tree organs, can provide important information about the quality of the derived wood fuels and give hints about the choice of the most appropriate combustion technique and/or the right wood fuel for a given combustion technique. Moreover, since elements have different concentrations in the different plant tissues, the preventive knowledge of the elements allocation can lead to the identification of the best harvesting strategy aimed at producing wood fuel with the lowest possible ash forming elements and environmental impact.This work focuses on the allocation in three tree compartments (foliage, branches and stem) of five important macroelements (K, Mg, Ca, N and P) in Norway spruce (Picea abies), and points out the possible effects of different harvesting strategies and tree age on the quality of the wood fuels. Results suggest that the Stem Only Harvesting is preferable to Whole Tree Harvesting system in terms of prevention of mineral content loss, as well as is preferable to avoid forest biomass from young trees because of the poorer fuel quality of the wood chips.