IEA joint trials: New lessons from old plantations

Two international trials of potential biomass species families and clones planted in 1985 have been analyzed to determine changing patterns in growth, diseases, and insects. In the Swedish trial, with close spacing and short rotations, Salix viminalis clones gave the best average yield of 17.4 Mg/Ha/yr on the first coppice rotation. In the Minnesota, USA trial, with wider spacings and a longer rotation Populus alba hybrid clones gave the best average yields of 5.5 Mg/Ha/yr. The most important disease and insect problems encountered were Septoria musiva stem cankers on some Populus clones; frost die back in some Salix clones; and the leaf blotch miner, Fenusa dohrnii, on most Alnus families. Recommendations for future international cooperation in field trials are presented.     

Farm wood fuel and energy project

This paper describes the findings of the Farm Wood Fuel and Energy Project. It began in 1991 and ended in 1997 and was undertaken to provide a commercial demonstration for the establishment of 50 hectares of short rotation coppice (SRC) on six farms in southern England and the development of associated marketing activities. The Project:

• — taught farmers how best to grow the crop and will enable them to teach others;

• — determined that winter conditions in the UK are unsuitable for most harvesting equipment trialled and that both harvesting and chip storage need to be re-examined;

• — demonstrated that SRC has the potential to be competitive with fossil fuels;

• — gave confidence to Government to include a Band for energy crops under the NFFO electricity generating procedures

     

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.     

Hydrogen production using sono-biohydrogenator

Hydrogen production in a novel sonicated biological hydrogen reactor (SBHR) was investigated and compared with a continuous stirred tank reactor (CSTR). The two systems were operated at a hydraulic retention time (HRT) of 12 h and two organic loading rates (OLRs) of 21.4 and 32.1 g COD/L.d. The average hydrogen production rates per unit reactor volume for the conventional CSTR were 2.6 and 2.8 L/L.d, as compared with 4.8 and 5.6 L/L.d for SBHR, at the two OLRs, respectively. Hydrogen yields of 1.2 and 1.0 mol H₂/mol glucose were observed for the CSTR, respectively, while for the SBHR, the hydrogen yields were 2.1 and 1.9 mol H₂/mol glucose at the two OLRs, respectively. The hydrogen content in the SBHR’s headspace was higher than that in CSTR by 10% and 31% at OLRs of 21.4 and 32.1 g COD/L.d, respectively. Both glucose conversion efficiency and HAc/HBu ratio in the SBHR were higher than in the conventional CSTR at both OLRs. The biomass yield of about 0.32 g VSS/g COD observed in the CSTR and 0.23 g VSS/g COD in the SBHR substantiate the higher H₂ yield in the SBHR. DGGE analysis confirmed the specificity of the microbial hydrogen-producing culture in the SBHR, with two different hydrogen producers (Clostridium sp. and Citrobacter freundii) detected in the SBHR and not detected in the CSTR.     

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.     

Cultivation studies of Taiwanese native Miscanthus floridulus lines

Four Taiwanese native Miscanthus floridulus lines, collected at altitudes of 260, 500, 1000, and 1500 m were cultivated in 2009 and 2010. The plant height and tiller numbers of four M. floridulus lines increased gradually along with the growing time. These M. floridulus lines had the tallest plant height and most tiller number after these species were planted 210 days. Line 3, which was collected at the altitude of 1000 m, had the ability to grow at low temperature. Line 3 M. floridulus had the highest plant height, tiller number, fresh and dry yields than other three lines. Fresh and dry yields of Line 3 were positively correlated to the plant height, tiller number, and leaf width, but showed no correlation with the leaf length. The correlation between agronomic traits and climatic data was also studied. Results can be used as a model for developing a non-food crop-based energy production system in the future.     

Intensive culture of European black alder in central Indiana, U.S.A.: Biomass yield and potential returns to farmers

Growing interest in woody biomass for energy in the midwestern U.S. will require information on species and site productivities. We investigated 3, 6 and 14 year yields of the nitrogen-fixing tree species. European black alder, at three spacings on a marginally productive soil in central Indiana, U.S.A. The highest yield was 10 Mg ha⁻¹ yr⁻¹ at age three at the closest spacing of 0.5 × 1 m. Other spacings and ages provided smaller yields. Fertilization with phosphorus and potassium only provided a response in the initial 3 year rotation. Whole-tree and stem-only harvests removed varying levels of nutrients from the site. However, on these marginally productive sites where N and sometimes P are limiting, sustainable harvesting could be maintained due to the nitrogen-fixing capability of this species and the effects of N fixation on P availability. Preliminary economic analyses indicated that growing biomass on farms could be profitable, but only with farm or forestry program cost-sharing assistance. Where establishment expenses could be reduced by wider spacings, the use of seed rather than seedlings, or farmer-substituted labor, returns to the farmer were competitive with row-crop and timber production.     

Biomass equations and estimation for Gmelina arborea and Nauclea diderrichii stands in Akure forest reserve

Biomass estimation was carried out for even-aged stands of Gmelina arborea and Nauclea diderrichii in Akure forest reserve. Linear and allometric regression equations for biomass prediction were developed for trees of both species. The yield of each species and total above-ground biomass (TAGB) were estimated and compared. The various equations developed were assessed based on high coefficient of determination (R²), significant F-ratio, and small Furnival index (FI) to select appropriate equation for prediction. The t-test shows a significant difference when the total volume and total dry weight of both species were compared, Gmelina arborea having a greater value than Nauclea diderrichii in both cases. The total volume of Gmelina arborea per hectare was 721.40 m³ and 265.18 m³ for Nauclea diderrichii. The TAGB for Gmelina arborea was 264,762 kg/ha and 88,293 kg/ha for Nauclea diderrichii.     

Experimental comparison of biochar species on in-situ biomass tar H2O reforming over biochar

Experimental investigations of in-situ tar H₂O reforming over various biochar species were carried out in the two-stage fluidized bed/fixed bed reactor. The physicochemical structures of biochar were studied by SEM, mercury intrusion porosimetry and FTIR methods. The mechanism of tar H₂O reforming over biochar was studied through the results of tar yields and quantitative analysis of typical tars by GC/MS. According to the theory of organic mass spectrometry and current mechanisms of tar transformation, the reaction path of typical tar H₂O reforming over biochar was constructed. The results show that the tar reforming rate over sawdust biochar is the most significant among the three kinds of biochar samples (i.e., rice husk, sawdust and cornstalk). The metallic species contribute greatly to the weight loss of biochar in 15 vol% H₂O atmosphere at 800 °C, while they are not the only determinants of tar H₂O reforming. The selectivity of biochar on the in-situ tar H₂O reforming is determined by the coupling effects of its physical and chemical characteristics. The biochar, with the porous surface structures, a certain amount of metallic species and the carbon structure with low polymerization, would be effective on in-situ tar H₂O reforming.     

Effects of competition between short-rotation willow and weeds on performance of different clones and associated weed flora during the first harvest cycle

In order to assess the ability of willow clones to compete with weeds, willow shoot biomass and plant mortality were measured over the first harvest cycle for 10 commercial and two breeding clones at three different sites in southern Sweden. Two levels of weed pressure (weeded and not weeded) were employed and the effects of cutback or not after the first growing season were compared for willow clones under weed pressure. There were significant differences between clones in their ability to compete with weeds, measured as willow shoot growth reduction in plots with weeds, at two of the three sites. However, shoot biomass reduction due to weeds was large in all the clones, with Stina and SW Inger among the least affected. Mean shoot growth reduction after the first harvest cycle for the commercial clones was 68.3%, 91.2% and 94.3% at the three sites and the corresponding plant mortality was 9.8%, 57.3% and 56.2% under weed pressure. Significant clonal differences in yield, under weed-free conditions, were found at all three sites. Significant clone-site interactions were found for both growth reduction and biomass production. Cutting back shoots after the establishment season, under weed pressure, resulted in higher mean plant mortality and lower mean willow shoot biomass after one harvest cycle at two of the three sites. The weed flora was initially dominated by annuals, but became dominated by perennial weeds during the first harvest cycle.     

Hydrogen production by supercritical water gasification of biomass: Explore the way to maximum hydrogen yield and high carbon gasification efficiency

Supercritical water gasification (SCWG) is a promising technology for wet biomass utilization. In this paper, orthogonal experimental design method, which can minimize the number of experiments compared with the full factorial experiments, was used to optimize the operation parameters of SCWG with a tubular reactor system. Using this method, the influences of the main parameters including pressure, temperature, residence time and solution concentration on biomass gasification were also investigated. Simultaneously, in order to further improve the gasification efficiency of biomass, acid hydrolysis pretreatment of feedstock, oxidizers addition and increasing reaction temperature were employed. Results from the experiments show that in the range of experimental parameters, the order of the effects of the factors on H₂ yield of corn cob gasification in SCW is temperature > pressure > feedstock concentration > residence time. Temperature and pressure have a significant and complicated effect on biomass gasification. Hydrogen yield increases by the acid hydrolysis pretreatment of feedstock, and oxidizer addition reduces the hydrogen yield but it promotes the increase in carbon gasification efficiency. Biomass feedstock with high concentration was gasified successfully at high reaction temperature.     

Productivity, aboveground biomass, nutrient uptake and carbon content in fast-growing tree plantations of native and introduced species in the Southern Region of Costa Rica

Early growth performance of four native and two introduced tree species was studied during six years at 13 sites in the southern region of Costa Rica. Selected study sites represent a wide environmental gradient.The selected species were: Pinus caribaea Morelet var hondurensis (Barret y Golfari) and Gmelina arborea Roxb as the introduced species, and Terminalia amazonia (J.F. Gmelin) Exell, Vochysia ferruginea Mart., Vochysia guatemalensis Donn. Sm. and Hieronyma alchorneoides Fr. Allemao. A study about the distribution of aboveground biomass, nutrients and total carbon content of these young plantations by compartments (branches, stem, bark and leaves) was also conducted. Biomass equations for tree compartments were fitted simultaneously using the data corresponding to 24 trees felled. Total export quantities of nutrient from stem and bark biomass were estimated in order to conduct an evaluation of the potential effect of harvesting these species on soil nutrient reserves. The data presented in this study related to plantation growth, aboveground biomass and nutrient concentration and C content by tree compartment, aboveground biomass equations by tree compartment, soil nutrient reserves, stability indices can be used as a reference for: a) selection of tree species vs site characteristics, b) estimation of nutrient export by stem + bark harvesting, c) planning for a second rotation, c) maintenance of site productivity and d) generate better carbon sequestration estimations.     

Where to produce rapeseed biodiesel and why? Mapping European rapeseed energy efficiency

Rapeseed is widely used to produce biodiesel, especially in Europe. In several studies, it has been shown that there is a good potential for growing this crop across the continent. However there is still little awareness that the energy efficiency of biofuel production from rapeseed is very low. Energy efficiency can be expressed in terms of Energy Return for Energy Invested (EROEI). We mapped EROEI values for all EU countries plus Switzerland based on expected yields derived from rapeseed suitability maps. We find that EU countries produce rapeseed biofuel with EROEI values of 2.2 and lower. We suggest that plans for biofuel cropping have to be supplemented by maps of EROEI. It is not only relevant to show where rapeseed can be grown, but we should also look at where its use for bioenergy can be efficient. In the area theoretically suitable for growing rainfed rapeseed (excluding unsuitable areas and water), 37.6% of the area can produce rape methyl ester (RME) biofuel only with an energy loss. We conclude that the energy efficiency of rapeseed biodiesel is low and spatially heterogeneous, and unless there are major technological improvements in the production process, replacing fossil fuels by biofuels from rapeseed is hardly a feasible option.