A survey of Italian chipping operations

We observed over 100 wood chipping operations, using time-and-motion methods to quantify their productivities, and interviews and observations to subjectively evaluate the factors that affect their existence and character. Productive time per green tonne decreased with increases in both chipper power and piece size. In Italy, chipping has evolved from a primary business for contractors who processed whole trees, to a secondary activity for loggers who dispose of residues by chipping them for particleboard. In recent years, biomass-fueled district heating plants in northern Italy have been added to the mix of users, and larger electric power plants may expand the chipping industry in the near future. Operators who heavily utilize chippers prefer self-propelled machines. Tractor-powered and towed chippers are used in a wide range of conditions, but the latter are restricted to landings while the former are employed at landings and within stands. Disc chippers have dominated the industry, but drum chippers are making inroads, especially in fuel supply operations. Chips are transported by farm tractors and powered trailers when distances are short (up to 3–4 km), by high-speed tractors for intermediate distances, and by trucks for distances over 30 km.     

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.     

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.     

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.     

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.     

Availability of logging residues and potential for electricity production and carbon displacement in the USA

This study assessed the abundance and regional distribution of logging residues and their potential for electricity generation and CO₂ emission displacement in the USA. Based on the 1997 Forest Inventory and Analysis (FIA) data, a 70% residue recovery rate, and a minimum viable power plant capacity of 10 MW, annually recoverable logging residues in the USA were estimated at 13.9 million dry t from growing stock and 36.2 million dry t from both growing stock and other sources. Most logging residues were located in the eastern USA; the Southeast and South Central regions accounted for approximately two-thirds of the national total from growing stock and about 50% of that from both growing stock and other sources. The recoverable residues from both growing stock and other sources could generate 67.5 TWh electricity annually. This would displace 17.6 million t carbon emitted from coal-fueled power plants (about 3% of total carbon emissions from the US electricity sector in 1997) at a cost ranging from US$60 to 80 t⁻¹ C.     

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.     

Pore structure classification and logging evaluation method for carbonate reservoirs: A case study from an oilfield in the Middle East

Based on the data of 121 thin sections, 24 mercury injection and physical properties of the carbonate reservoir in A oilfield of the Middle East, the reservoir in the study area is divided into four pore-throat systems by analyzing the pore-throat volume verses permeability-contribution curve of core mercury injection and corresponding depth NMR logging data. Taking into account the contribution of each pore-throat system to the rock, a new pore structure parameter P based on NMR logging data is proposed. On this basis, the P and flow porosity calculated from NMR logging data are used as variables, and the pore structure of carbonate reservoirs is divided into four types by using the K-means clustering method in combination with the characteristics of capillary pressure curves and thin sections. With the input of NMR logging data and conventional logging data, the classification model of pore structure is established by Rotation Forest algorithm. The accuracy of the classification model based on NMR logging is 98.56%, and the accuracy of the classification model based on conventional logging is 89.9%. Compared with the Random Forest algorithm and the Fisher discriminant method, the Rotation Forest algorithm has high prediction accuracy and strong stability. The research shows that the pore structure classification method proposed in this paper is in good agreement with the interpretation results, which can provide some reference value for finding effective reservoirs in the future.     

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.     

Isothermal and non-isothermal kinetic study on CO2 gasification of torrefied forest residues

CO₂ gasification of torrefied forest residues (birch and spruce branches) was investigated by means of a thermogravimetric analyser operated non-isothermally (400–1273 K) and isothermally (1123 K) under the kinetic regime, followed by kinetic analyses assuming different models. For the non-isothermal gasification, the distributed activation energy model (DAEM) with four or five pseudo-components was assumed. It is found that the severity level of torrefaction had great influences on gasification behaviour as well as devolatilization step. The activation energy of non-isothermal gasification step of three samples varied in the range of 260–290 kJ/mol. The char reactivity decreased with increased torrefaction temperature. For the isothermal gasification, the random pore model (RPM), shrinking core model (SCM), and homogeneous model (HM) were tested. The result has confirmed the trend of decrease in char reactivity with increased torrefaction temperature observed from the non-isothermal gasification. However, different trends in char reactivity due to different wood types were observed by the two methods of gasification.     

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.     

A case study on the costs and the fuel consumption of harvesting,transporting, and chipping chains for logging residues in Japan

The objective of this study is to examine the feasibility of a harvesting and transporting system for logging residues including the cost, energy, and carbon dioxide (CO₂) effectiveness of fossil energy substitution with logging residues in Japan. “A harvesting and transporting system for logging residues” was constructed with reference to some European countries, where the utilization of bioenergy is making steady progress, and examined based on field experiments in Japanese forestry. The feasibility of the system was discussed from the standpoints of cost, energy, and CO₂, and the system was compared with those of European countries. Concerning the system, it is desirable that the process of chipper comminuting should be incorporated into the system as early as possible. Although such a system is not particularly feasible in Japan from the standpoint of cost, it is suggested that it should be possible for Japan to reduce the domestic CO₂ emissions by utilizing logging residues as alternative energy resources. A comparison with the European countries and a preliminary sensitivity analysis to the system demonstrate that the technical development to reduce the total cost, e.g., improving the forwarding and transporting efficiency, is essential for realizing bioenergy utilization in Japan.     

Crop residues as raw materials for biorefinery systems – A LCA case study

Our strong dependence on fossil fuels results from the intensive use and consumption of petroleum derivatives which, combined with diminishing oil resources, causes environmental and political concerns. The utilization of agricultural residues as raw materials in a biorefinery is a promising alternative to fossil resources for production of energy carriers and chemicals, thus mitigating climate change and enhancing energy security. This paper focuses on a biorefinery concept which produces bioethanol, bioenergy and biochemicals from two types of agricultural residues, corn stover and wheat straw. These biorefinery systems are investigated using a Life Cycle Assessment (LCA) approach, which takes into account all the input and output flows occurring along the production chain. This approach can be applied to almost all the other patterns that convert lignocellulosic residues into bioenergy and biochemicals. The analysis elaborates on land use change aspects, i.e. the effects of crop residue removal (like decrease in grain yields, change in soil N₂O emissions and decrease of soil organic carbon). The biorefinery systems are compared with the respective fossil reference systems producing the same amount of products/services from fossils instead of biomass. Since climate change mitigation and energy security are the two most important driving forces for biorefinery development, the assessment focuses on greenhouse gas (GHG) emissions and cumulative primary energy demand, but other environmental categories are evaluated as well.Results show that the use of crop residues in a biorefinery saves GHG emissions and reduces fossil energy demand. For instance, GHG emissions are reduced by about 50% and more than 80% of non-renewable energy is saved. Land use change effects have a strong influence in the final GHG balance (about 50%), and their uncertainty is discussed in a sensitivity analysis. Concerning the investigation of the other impact categories, biorefinery systems have higher eutrophication potential than fossil reference systems. Based on these results, a residues-based biorefinery concept is able to solve two problems at the same time, namely find a use for the abundant lignocellulosic residues and ensure a mitigation effect for most of the environmental concerns related to the utilization of non-renewable energy resources.Therefore, when agricultural residues are used as feedstocks, best management practices and harvest rates need to be carefully established. In fact, rotation, tillage, fertilization management, soil properties and climate can play an important role in the determination of the amount of crop residue that can be removed minimizing soil carbon losses.     

Woodland owners' attitudes towards energy from forest biomass in a carbon-intensive jurisdiction: Case study of Nova Scotia,Canada

The use of forest biomass in thermal generation processes has been recognized by the Government of Nova Scotia (NS) as one option that could help meet its renewable electricity goals (25% by 2015 and 40% by 2020). Over half of the woodland in NS is owned by small-private woodland owners (51%), indicating that they could significantly influence the future of NS forests and its potential use for energy purposes. This paper presents the results of a survey of small-woodland owners on their attitudes towards using energy from forest biomass. 489 small-woodland owners responded to mail-out surveys and 14 rural community members participated in three focus groups. Three major findings emerged. First, it was found that the acceptability of using forest products varied depending on multiple factors – the source of biomass, harvesting methods, and [predicted] end-use. Second, forest sustainability and keeping resources local were the two most important concerns amongst respondents. Finally, respondents felt that better collaboration with other stakeholders and education around the issues would be the best strategies for overcoming these concerns. The paper also highlights the barriers and drivers as perceived by the woodland owners as they relate to the possibility of using more biomass for energy in the future.     

Costs and CO2 benefits of recovering,refining and transporting logging residues for fossil fuel replacement

There are many possible systems for recovering, refining, and transporting logging residues for use as fuel. Here we analyse costs, primary energy and CO₂ benefits of various systems for using logging residues locally, nationally or internationally. The recovery systems we consider are a bundle system and a traditional chip system in a Nordic context. We also consider various transport modes and distances, refining the residues into pellets, and replacing different fossil fuels. Compressing of bundles entails costs, but the cost of chipping is greatly reduced if chipping is done on a large scale, providing an overall cost-effective system. The bundle system entails greater primary energy use, but its lower dry-matter losses mean that more biomass per hectare can be extracted from the harvest site. Thus, the potential replacement of fossil fuels per hectare of harvest area is greater with the bundle system than with the chip system. The fuel-cycle reduction of CO₂ emissions per harvest area when logging residues replace fossil fuels depends more on the type of fossil fuel replaced, the logging residues recovery system used and the refining of the residues, than on whether the residues are transported to local, national or international end-users. The mode and distance of the transport system has a minor impact on the CO₂ emission balance.     

A study of energy production from cork residues: Sawdust,sandpaper dust and triturated wood

In the present work the gasification process of cork residues sourced in an industrial procedure in the regions of Extremadura (Spain) and Alentejo (Portugal) was studied. These by-products were classified as black agglomerates (low and high granulate), sandpaper dust (white agglomerate) and triturated wood. Samples of several residues obtained through different phases of the cork manufacturing process were collected and next quantified. In order to test their ability to produce energy, all the referred residues were gasified. The air flow was varied, ranging from 50 up to 400 cm³ min⁻¹. The thermal treatment temperature was also varied from 650 °C up to 800 °C. The experimental results indicate that the optimal conditions in terms of energy production were an air flow equal to 200 cm³ min⁻¹ and a treatment temperature of 800 °C.     

Reinforcement learning for electricity dispatch in grids with high intermittent generation and energy storage systems: A case study for the Brazilian grid

Intermittent energy sources such as wind and solar have recently been growing a lot faster than dispatchable energy sources in Brazil, which made investments in energy storage systems become an attractive possibility in the country. Current operational policies for energy dispatch do not consider storage systems and need adjustments to fit this technology. With this motivation, we use reinforcement learning techniques to develop policies for managing storage systems in a grid that can handle time-varying inputs and loads, with rolling forecasts. We use a deterministic lookahead (DLA) policy which has been parametrically modified to perform well in the presence of uncertain forecasts. For realistic simulations, the base model considers important characteristics in a grid that influence the interaction between scheduling and real-time operation such as power and ramping capacities, notification times, and stochastic forecasts. The parametric modification with tunable parameters allows an optimal balance between two conflicting services provided by the storage system: time-shifting and spinning reserves. Optimal reserves ranged from 35% to 100%, depending on the tested dataset, which shows the importance of tuning. Differently from stochastic lookahead policies, which are computationally expensive, parameterized DLA policies can be applied to real-time operation after being optimized in a stochastic base model.     

Life cycle impacts of waste wood biomass heating systems: A case study of three UK based systems

With increasing renewable energy targets and the use of biomass for energy production, questions arise about the sustainability of differing types of bioenergy. Much has been made about the renewable transport fuel obligations and the impact the production of biofuel can have on the environment, but there has been less consideration of more small scale biomass heating systems. This work examines the life cycle impacts of the production and use of three such systems using waste wood in the South West of England. Burning of wood in the UK was reduced after the introduction of legislation to reduce smog in the 1950s, and so the impact of the emissions from the boilers has been examined. Whilst the boilers studied complied with UK emissions legislation, the emissions were the most significant impact found. However, there were differences in the emission levels depending on the loading of the boiler. In all cases the energy payback of the systems was under one year, ranging from approximately four to ten months.     

Potential of bio-hydrogen production from dark fermentation of crop residues: A review

This study provided an estimate of the potential of bio-hydrogen production from dark fermentation of crop residues on a worldwide scale. The different crop residues reviewed included sugarcane tops, leaves and bagasse, corn straw, corn cob and corn stover, wheat straw, rice straw and husk, soybean straw, oil palm trunk and empty fruit bunch, sugar beet pulp, cassava residue, barley straw and sweet sorghum bagasse. Among these crop residues, wheat and rice straws are produced in the highest amount although sugarcane dominates crop production on a worldwide scale. Based on the bio-hydrogen yields reported in literature, estimated worldwide bio-hydrogen potential is highest for untreated rice straw at 58,002 Mm³/year followed by untreated wheat straw at 34,680 Mm³/year. This corresponds to a bio-energy potential of 623 PJ/year and 373 PJ/year for raw rice straw and wheat straw respectively while pre-treatment of the crop residues significantly increases the bio-hydrogen and bio-energy potential. While dark fermentation of crop residues offers a huge bio-energy potential, the process suffers from several constraints that hinder its implementation. As such, coupling of the dark fermentation process with the anaerobic digestion process as a two-stage process seems the most economically viable option for large-scale implementation.     

Network benefits of embedded solar systems: A case study from western Sydney

This paper presents a simulation study based on actual load, sunshine and wind data. A distribution feeder simulation model was constructed using this data to determine what potential benefit embedded wind, solar and storage elements could give to the distribution network. The results were compared to earlier studies. It was discovered that over the past 5–10 years, the hot weather peak load has extended from 3 pm to 6 pm and that a more northwesterly orientation of solar panels is of assistance. It was also found that wind is of little assistance in hot weather peaks, in contrast to data for the NSW central tablelands region; however solar contributes at least 50% of its nominal peak capacity. As hot weather peaks are now extending into the early evening, it was found that storage would be of great benefit and would enhance the use of renewable energy sources. As part of the feeder model, the optimal method of Var control from the embedded sources was also studied.