Predictive models of forest logging residues in Romanian spruce and beech forests

Forest logging residues are systematically left after exploitation. In Romania, logging residues were traditionally used by population for fuel but have not been considered at large scale for industrialization. The estimation of the resource needed a more accurate assessment and the development of devoted biomass models for large-scale applications. Our study aims at estimating the amount of logging residues based on direct biomass measurements for the two main species of Romanian Carpathian forests: Norway spruce and beech. A country-scale field measurement campaign resulted in the sampling of 100 Norway spruce and 74 beech trees. Models of logging residues biomass were developed for both species. The amount of potential logging residues per tree was greater in beech than in Norway spruce. The models developed, nonlinear by essence, showed that diameter-based equations enable the evaluation of individual logging residues potential. Using tree height as an additional independent variable did not improve the models. The models fitted were applied to yield tables in order to estimate the resource potential in spruce and beech stands for each productivity class, and its dynamic during the production cycle. The calculations proved that the potential amount of logging residue is larger in spruce stands. The amount in beech is very sensitive to the productivity class, unlike in spruce stands. The potential biomass produced during early thinnings is however greater in beech stands than in spruce ones. A more systematic and organized collecting of residues could offer a fast answer to the need of increasing renewable energy share.     

Hydrothermal pretreatment of fresh forest residues: Effects of feedstock pre-drying

Hydrothermal pretreatment has become an attractive method for upgrading biomass fuel because of its capacity to work effectively with various types of low cost wet feedstock. However, most of the past studies in the field dried the feedstock prior to the pretreatment without being aware of the effect of high temperature drying. In this study, fresh forest residues (Norway spruce and birch branches) were used as feedstocks to utilize the advantage of the hydrothermal pretreatment method. More importantly, the present work aims at investigating the effects of the pre-drying process on the solid product via a direct comparison on the fuel and physicochemical properties of hydrochars produced from fresh and dried forest residues. This assessment helps to identify differences when fresh and dried feedstocks are used for hydrothermal pretreatment study. The results showed that these differences were considerable with respect to solid and energy yields; and the use of dried feedstocks will be less representative for a commercially feasible hydrothermal process, using wet feedstock directly.     

Extracting whole short rotation trees with a skidder and a front-end loader

We time-studied a Caterpillar 950F front-end loader and a Caterpillar 528 grapple skidder used to extract bunched whole trees to a landing in a short rotation Eucalyptus plantation. The loader was 40–60% more productive than the grapple skidder, depending on extraction distance. Alternatively, the single loader could both extract trees and handle the landing duties, such as moving residues from the flail-chipper, whereas the skidder required a second machine (skidder or small loader) to handle landing activities. Front-end loaders appear to be very promising as extraction devices for short rotation plantations where tree characteristics, terrain and soil conditions allow them to be used.     

Exploring Norwegian forest owner's intentions to provide harvest residues for bioenergy

The large biomass resource in the Norwegian woods may contribute considerably to the development of a more sustainable energy system. A more complete tree harvest is being promoted, where harvest residues are utilised to provide bioenergy. Little research has addressed the intentions of forest owners towards harvesting forest residues.A survey of non-industrial private forest owners in two municipalities located in the south east of Norway was conducted in order to understand their attitudes and intentions to provide harvest residues for bioenergy production. The results showed that forest owners would be willing to supply harvest residues: about 40% of the respondents were highly in favour and almost 70% expressed a positive opinion.A factor analysis of the attitudinal statements resulted in four main factors of which three were found to significantly affect the intention in a regression analysis. The first factor was related to the beneficial effects of harvest residues, the second covered negative (mainly environmental) effects, and the third covered the positive effects upon forest management.The social influences seemed to have two distinct dimensions: personal relationships (e.g., other forest owners, neighbours and family) and professional interactions (e.g., governmental authorities). While the former had a significant effect on intentions, the latter did not. Finally, socioeconomic variables (gender, age, and municipality) did not influence the intention to deliver harvest residues.     

A method for integrated extraction of logging residues and soil scarification on a small scale

A new method for integrated haulage of logging residues and soil scarification on a small-scale has been evaluated. The base machine was a farm tractor to which a grapple loader trailer was attached. The grapple loader had an attachment on the grapple used for the integrated recovery of forest energy from logging residues and soil scarification. The machine was in this case, when hauling the logging residues fresh, also used for hauling round wood. It may even be used for, e.g. spreading wood ashes (only simulated). Conventional machine systems with special machines for all four types of work result in very high fixed costs for moving, etc. which makes cost unacceptable for many small sites.

Effective time per dry ton of logging residues was 28.4 min in the integrated method, of which soil scarification was 14.3 min. Average load size was about 1.3 ton dry matter (about 2.9 m³ solid). The soil scarification plots covered 12% of the surface.

Cost calculations show that the integration of several activities results in substantially lower costs for small harvesting sites. For sites of about 1.5 ha the cost is about the same as for conventional machines. The studied method creates new possibilities for self-employed forest owners to do the work themselves and, in case of lower personal cost and no moving cost, reduce cost further.     

Strategic optimization of forest residues to bioenergy and biofuel supply chain

Forest residues are renewable materials for bioenergy conversion that have the potential to replace fossil fuels beyond electricity and heat generation. A challenge hindering the intensified use of forest residues for energy production is the high cost of their supply chain. Previous studies on optimal design of forest residue supply chains focused on biofuel or bioenergy production separately, mostly with a single time period approach. We present a multi‐period mixed integer linear programming model that optimizes the supply chain of forest residues for the production of bioenergy and biofuels simultaneously. The model determines (i) the location, type and size of the technologies to install and the period to install them, (ii) the mix of biofuel and bioenergy products to generate, (iii) the type and amount of forest residues to acquire and the sourcing points, (iv) the amount of forest residues to transport from sources to facilities and (v) the amount of product to transport from facilities to markets. The objective of the model is to maximize the net present value of the supply chain over a 20‐year planning horizon with yearly time steps. We applied the model to a case study in British Columbia, Canada, to investigate the production of heat, electricity, pellets and pyrolysis bio‐oil from available forest harvesting residues and sawmill wastes. Based on current energy generation costs in the region and the predicted operating costs of new conversion plants, the results of our model recommended the installation of small biomass boilers coupled with steam turbines for electricity production (0.5 and 5 MW) and pyrolysis plants with a capacity of 200 and 400 odmt day^?1. We performed a sensitivity analysis to evaluate the sensitivity of the optimal result to changes in the demand and price of products, as well as the availability and cost of forest residues. Copyright © 2014 John Wiley & Sons, Ltd.     

A GIS-based analysis on the relationship between the annual available amount and the procurement cost of forest biomass in a mountainous region in Japan

The feasibility of utilization of forest biomass for energy in a mountainous region in Japan is discussed based on analyses with a geographic information system (GIS). In this study, ‘forest biomass’ denotes logging residues, thinned trees, and trees from broad-leaved forests. First, using the GIS, the distribution map of biomass resources was completed, and the topographical information of each sub-compartment was prepared. Second, harvesting and transportation systems were classified into six types by fraction of tree for energy (two types) and by topographical conditions (three types). Equations for cost calculation were developed and included the variables slope, skidding/yarding distance, and transportation distance. Finally, the relationship between the mass and the procurement cost of forest biomass in the region was analyzed. The results show that logging residues (the available amount was 4.035 Gg y⁻¹ on a dry-mass basis) were the least costly followed by broad-leaved forests (20.317 Gg y⁻¹) while thinned trees (27.854 Gg y⁻¹) were the most costly. The analysis may support operational planning, especially the decision of selecting sub-compartments to be felled. For instance, the amount of biomass needed to supply a power-plant covering 24.8% of the regional household need was calculated to 30.106 Gg y⁻¹. This amount of forest biomass could optimally be harvested from sub-compartments whose procurement costs were lower than 108.6 US$ Mg⁻¹.     

Bioenergy potential of agricultural and forest residues in Uganda

Biomass is the major source of energy in most developing countries. However, there are concerns about the sustainability of biomass supplies and the environmental impacts resulting from their use. Use of residues could contribute to ensuring sustainable supply of biomass energy. This study presents findings of an evaluation of the energy potential of agricultural and forest residues in Uganda using census data of the year 2008/2009. Annual productions of crop and forest residues were estimated using residue-to-product ratio (RPR) method. Energy potential of each residue class was then determined basing on their respective lower heating values. The biogas generation potential of each animal category was used to evaluate the energy potential of animal manure. Results showed that the total energy potential of the residues amount to 260 PJ y⁻¹, which is about 70% of gross biomass energy requirement of Uganda for the year 2008. Crop residues had the highest contribution of about 150 PJ y⁻¹, followed by animal residues with a potential of 65 PJ y⁻¹. Maize residue is the predominant crop residue with energy potential of 65 PJ y⁻¹ followed by beans and banana, each at 16 PJ y⁻¹. This study indicates that agricultural and forest residues can be a major renewable energy source for Uganda. When sustainably utilised, biomass residues could contribute to reduction in environmental degradation in the country.     

Harvesting operations and energetics of tall grasses for biomass energy production: A case study

The U.S.A. imports about 50% of its energy needs while Florida imports about 85%. Among the renewable energy sources available, biomass appears promising especially in the southeast which includes Florida because of a favorable environment for production and the available methods to convert biomass to energy. Optimal production of biomass requires the identification and management of high yielding persistent perennial cultivars. Elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spontaneum L.) are two tall grasses that meet these requirements. To optimize the supply of convertible biomass, suitable methods of harvesting the crop must be available. The purpose of this research was to study the feasibility and energetics of harvesting, drying, and baling tall grasses with conventional farm machinery.

A Mathews rotary scythe and a New Holland 849 Auto Wrap large round baler were determined to provide a practical harvesting system for baled biomass averaging 15–27 Mg ha⁻¹. The rotary scythe can be used for harvesting and fluffing or turning a windrow over to expedite drying. This harvesting system requires about 3 kg diesel fuel Mg⁻¹ dry biomass (DB), 25 min of time Mg⁻¹ DB, and a cost of about $10 to 12 Mg⁻¹ DB. Energy requirements of harvesting operations would be about 300–375 MJ Mg⁻¹ DB, and primary energy requirements for production and harvesting are about 1100–1500 MJ Mg⁻¹ DB. For each unit of fossil fuel invested in the total production and harvesting system, 12–15 units would be returned in biomass.     

The effect of increased extraction of forest harvest residues on soil organic carbon accumulation in Sweden

The demand and potential for increasing the use of bioenergy from harvest residues in Sweden are large. However, harvest residue (branches and tops) and stump extraction negatively affect soil organic carbon (SOC) accumulation. The main objective of this study was to assess the effects of increased harvest residue extraction on soil organic carbon (SOC) accumulation at national level. Further, the reduction in CO2 by substituting coal with biofuel from harvest residues and stumps was assessed. Several scenarios with increased harvest residue extraction were simulated with the forest management system HUGIN and the SOC decomposition model Q and the effects on SOC accumulation in Swedish coniferous forest soils were assessed. All scenarios resulted in decreased SOC accumulation. The decrease in SOC accumulation was largest for stump extraction, with 0.15 Mg C ha⁻¹ y⁻¹ loss on average over a 100-year simulation period. In all scenarios, the short-term effects on SOC accumulation were greater than the long-term effects. The effect of substituting coal with bioenergy was an immediate reduction of net CO₂ emissions. An increase in the use of forest residues leads to CO₂ mitigation in the atmosphere, even when SOC losses are accounted for.     

Recovering of forest biomass from Spanish hybrid poplar plantations

Residues recovering from traditional poplar plantations for timber production are a potential relevant biomass source in Spain and other temperate countries. Three different residual biomass harvesting systems have been work-studied in order to characterize the work methods and analyze their productivity and cost. Two were oriented to branches, top and/or energy wood collection, chipping and transport using different work methods, while the other one consisted of after-logging stumps removal and shredding. Different sized and powered chippers worked in the two first cases, besides different farm tractors with trailers for off-road chips transport. Also the trucks and the loading machines were different. In the third site, a backhoe excavator removed the stumps, and a bucket loader collected them to be grinded by a shredding machine. Productivity and cost have been analyzed using IUFRO standards, providing average figures and, when possible, predictive productivity equations. Most capital-intensive equipment option has shown to be most productive, but less investment requiring system is cheaper and may be most interesting for some enterprise and plantation sizes. In addition, logistics of biomass and timber supply has been analyzed, and some indications about equipment sizing, machine annual production and relocation costs related to supply area and average plantation size are provided.     

Experimental study of gasification of biomass residues for electrical energy generation

In the present work the gasification process of different types of biomass residues (cork residues) generated by industries in Spain has been studied. These sub products are classified as black agglomerates (low and high granulate). Samples of several residues obtained through different phases of the production process were collected, following a subsequent quantification of each of the four types obtained. First the sandpaper dust was tested, varying the air flow from 50 to 400 cm³ min^?1 and the temperature of the reaction from 650 to 800°C. A preliminary study of a pilot installation of gasification of 50 kWe using these residues was made taking into account the experimental results obtained in the laboratory. A thermal power of 220 kW was predicted for the installation, taking into account the energetic characteristics of the residues for 50 kg h^?1 of raw material, with installation efficiency of 22.5%. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrogen and methane production from lipid-extracted microalgal biomass residues

A two-stage process to produce hydrogen and methane from lipid-extracted microalgal biomass residues (LMBRs) was developed. The biogas production and energy efficiency were compared between one- and two-stage processes. The two-stage process generated 46 ± 2.4 mL H₂/g-volatile solid (VS), and 393.6 ± 19.5 mL CH₄/g-VS. The methane yield was 22% higher than the one in the one-stage process. Energy efficiency increased from 51% in the one-stage process to 65% in the two-stage process. Additionally, it was found that repeated batch cultivation was a useful method to cultivate the cultures to improve the methane production rate and reduce the fermentation time. In the repeated batch cultivation, the methane yield slightly decreased if the ammonia levels rose, suggesting that the accumulation of ammonia could affect methane production.     

Assessment of the availability of agricultural and forest residues for bioenergy production in Romania

This paper provides a resource-based assessment of availability of biomass resources for energy production in Romania, at NUTS-3 level. The estimation of available biomass includes the residues generated from crop production, pruning of vineyards and orchards, forestry operations and wood processing. The estimation of crop residue availability considers several site-specific factors such as crop yields, multi-annual yield variation, environmental constraints and competitive uses. The evaluation of agricultural residues was based on specific residue to product ratios, depending on crop type and crop yield. An estimate of pruning residues is proposed, based on current orchard and vineyard areas and specific ratios of residues. Woody biomass considers forest and forestry residues (including firewood) and wood processing by-products, taking into account the type and share of the unused part of the tree biomass and technical and economic aspects, including availability and competitive use. The amount of agricultural and forest residues available for bioenergy in Romania was estimated at 228.1 PJ on average, of which 137.1 PJ was from annual crop residues, 17.3 PJ residues from permanent crops and 73.7 PJ/year from forestry residues, firewood and wood processing by-products. The biomass availability shows large annual and spatial variations, between 135.6 and 320.0 PJ, due to the variation in crop production and forestry operations. This variation, which is even larger at the NUTS-3 level, if not properly considered may result in shortages in biomass supply in some years, when biomass is available in a lower amount than the average.     

Biohydrogen production from forest and agricultural residues for upgrading of bitumen from oil sands

In this study, forest residues (limbs, tops, and branches) and straw (from wheat and barley) are considered for producing biohydrogen in Western Canada for upgrading of bitumen from oil sands. Two types of gasifiers, namely, the Battelle Columbus Laboratory (BCL) gasifier and the Gas Technology Institute (GTI) gasifier are considered for biohydrogen production. Production costs of biohydrogen from forest and agricultural residues from a BCL gasification plant with a capacity of 2000 dry tonnes/day are $1.17 and $1.29/kg of H₂, respectively. For large-scale biohydrogen plant, GTI gasification is the optimum technology. The delivered-biohydrogen costs are $2.19 and $2.31/kg of H₂ at a plant capacity of 2000 dry tonnes/day from forest and agricultural residues, respectively. Optimum capacity for biohydrogen plant is 3000 dry tonnes/day for both residues in a BCL gasifier. In a GTI gasifier, although the theoretical optimum sizes are higher than 3000 dry tonnes/day for both feedstocks, the cost of production of biohydrogen is flat above a plant size of 3000 dry tonnes/day. Hence, a plant at the size of 3000 dry tonnes/day could be built to minimize risk. Carbon credits of $119 and $124/tonne of CO₂ equivalent are required for biohydrogen from forest and agricultural residues, respectively.     

糠醛废渣用作秸秆成型粘结剂的试验研究

选用糠醛废渣作为玉米秸秆成型的粘结剂,在糠醛废渣添加量不同的条件下,对秸秆的成型效果进行了试验研究.试验结果表明:在玉米秸秆成型过程中加入适量的糠醛废渣,可以使秸秆在较低的压力下成型,降低了秸秆成型过程中的能量消耗.     

Quantification and use of forest biomass residues in Maputo province, Mozambique

This article describes a study on the quantification and use of forest biomass residues in Maputo province, in Mozambique. The study was performed based on information from the thematic cartography of soils of Maputo province, provided by the National Direction of Forest and Land of Mozambique, and data for the forest growth rates available in the literature. It was estimated that the total production of forest biomass residues in Maputo province is 1,233,412 ton/year, with a corresponding energy potential of 17,267,771 GJ/year. As a way of making the forest biomass residues profitable, the present work proposes the use of part of the residues as fuel in new power plants to be build in Maputo province. In this part of the study aiming at implanting power plants in Maputo province, it was taken into account the risk of forest fires, number of existing consumers of forest residues, residues availability, protected forests, transport infrastructures and existence of national electric network. It was found that the districts of Magude and Moamba are those that have the best conditions to receive the new biomass power plants. Factors such as the cost of the technology and the degree of pre-treatment of the forest residues have been taken into consideration in choosing the combustion technology for the proposed power plants. In this context, the grate burning technology appears to be the most advantageous from costs/benefits viewpoint. The proposed power plants can produce about 236,520 MWh, which is equivalent to 32% of the energy consumed in Maputo province in 2004.     

Activity oriented stochastic computer simulation of forest biomass logistics in Greece

An activity oriented stochastic computer simulation model of forest biomass logistics in Greece, based on SLAMSYSTEM simulation language, has been developed. A SLAMSYSTEM simulation network was built to represent forest biomass units flow from felling to storage at a millyard. A simulation experiment with data collected at the Elatia forest region of Drama in North Greece was executed. Several scenarios of the observed and alternative inventory times, interest rates, and operational systems for forwarding, were used to define the effect of inventory time, interest rate, and loss of value due to fibre deterioration and operational systems, on cost per unit per operational stage, and the final cost at the millyard. The model may be used as a prototype Decision Support System for forest biomass logistics in Greece.     

Renewable energy benefits with conversion of woody residues to pellets

In the frame of an Interreg IIIC Network-Operation named RegEnergy, that unites 18 partners from 11 countries of Europe, the feasibility of using the woody by-products for heating purpose in a typical Mediterranean region was investigated. Focusing on the Abruzzo Region as representative sample area, it came out that a significant amount of the above mentioned renewable energetic material is annually available as a consequence of well-consolidated and economically significant agro-industrial activities, forest maintenance and industrial wood production and transformation. In particular, it was found that the total amount of woody residues, as dry substance, are more than 700 kt/a, with 30% resulting from pruning activities related to the cultivation of about 360 km² of vineyards and 450 km² of olive-groves; these residues are concentrated in the hilly part of the region close to the Adriatic sea coast. Starting by this pleasant situation, the feasibility of a properly localized wood pellets production plant was supported by both the economic and energetic analysis. Additional suggestions related to optimal plant localization and to the best use of the woody pellets as substitute of natural gas for heating purposes were reported along with the positive impact of the whole action on the quality of the environment and on the recovery of soil fertility.     

Enhanced hydrogen production from lipid-extracted microalgal biomass residues through pretreatment

Energy recovery from lipid-extracted microalgal biomass residues (LMBRs) plays a significant role in the sustainable development of the microalgal biodiesel industry. Different methods were used to pretreat LMBRs to improve their solubilization and anaerobic hydrogen production abilities. The pretreatment methods studied included thermal (100 °C and 121 °C), alkaline and thermo-alkaline pretreatments (combinations of alkaline and thermal pretreatments). The results showed that thermo-alkaline pretreatments resulted in remarkable improvements of LMBR solubilization, which led to an increase in hydrogen yield. The highest hydrogen yield of 45.54 mL/g-volatile solid (VS) was achieved from LMBRs pretreated by the thermo-alkaline pretreatment at 100 °C, which was approximately three-fold higher than the yield from untreated LMBRs. The results of this study proved that thermo-alkaline pretreatment at 100 °C is an effective method to improve LMBR solubilization and increase the hydrogen production from LMBRs.