Modeling stump biomass of stands using harvester measurements for adaptive energy wood procurement systems

The value and volumes of industrial stump fuel supply are increasing for energy production. Accurate estimates of aboveground and belowground biomass of trees are important when estimating the potential of stumps as a bioenergy source. In this study two stump biomass equations were adapted and tested using them as calibrated stump biomass models computed as the cumulative sum by a local stand. In addition, variables derived from stem measurements of the forest harvester data were examined to predict stump biomass of a stand by applying regression analysis. The true stump yield (dry weight) was used as the reference data in the study. Both biomass models performed well (adjusted R² ˜ 0.84) and no advance was found in using other stem dimensions as independent variables in the model. The stand-level model can be used in innovative stump biomass prediction tools for increasing efficiency of energy wood procurement planning to stands within a certain area. In practice, wood procurement managers would need to adapt developed system and decide whether the degree of accuracy/precision provided by the models is acceptable in their local stand harvesting conditions.     

Comparing solar energy alternatives

This paper outlines a computational procedure for comparing the merits of alternative processes to convert solar radiation to heat, electrical power, or chemical energy. The procedure uses the ratio of equipment investment to useful work as an index. Comparisons with conversion counterparts based on conventional fuels are also facilitated by examining this index. The procedure is illustrated by comparisons of (1) photovoltaic converters of differing efficiencies; (2) photovoltaic converters with and without focusing concentrators; (3) photovoltaic conversion plus electrolysis vs photocatalysis for the production of hydrogen; (4) photovoltaic conversion plus plasma arcs vs photocatalysis for nitrogen fixation. Estimates for conventionally-fuelled processes are included for comparison. The reasons why solar-based concepts fare poorly in such comparisons are traced to the low energy density of solar radiation and its low stream time factor resulting from the limited number of daylight hours available and clouds obscuring the sun.     

Renewable energy alternatives for developed countries

This paper examines renewable energy alternatives in developed countries: environmental mechanisms; future energy alternatives; green electricity marketing and its potential; pricing; and limitations on the eve of open access. It discusses objectives in electricity restructuring; the role of resources planning in forming long range energy environmental policies; feasibility of electricity trading mechanisms; green marketing in the United States and Australia; green energy offers in Canada; and the results of green pricing programs in Europe and the United States. The role of existing and planned mechanisms to achieve environmental benefits in restructured electricity markets are reviewed. Technological and institutional challenges of achieving real, long-term reductions in carbon dioxide and other emissions from the electric sector are discussed. Factors associated with infrastructure turnover together with technology development and deployment are addressed, where attention is given to policies which promote highly integrated and coordinated reductions in emissions. The paper then focuses on the green pool and trends in power marketing where status of competitive markets, green pricing programs for franchise customers, green power products for contestable customers, credibility of green power marketing, and public policy for renewable energy technologies in competitive markets are discussed. It then reviews green energy in Ontario on the eve of open access, and shows there is a market for green energy if customers have a choice     

Economics of wood energy supply systems

Summaries of papers presented at a conference on Bioenergy Supply Systems 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

     

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.     

Bioenergy from forest thinning: Carbon emissions,energy balances and cost analyses

The growing demand for bioenergy in Sweden has drawn attention to the potential of forest thinning as bioenergy feedstock. There are, however, concerns regarding the cost effectiveness and environmental challenges of harvesting and processing forest thinnings into bioenergy. It is against this background that cost, energy and carbon balances were analysed to evaluate some of the economic and environmental sustainability issues of forest thinning based bioenergy systems. Primary data was collected from two thinning operations in two forest plots comprising spruce and birch stands. One operation involved the use of the conventional two machines (one separate machine for cutting or felling and another for forwarding felled trees) for the thinning work. The second operation involved a harwarder, which combines tree felling/cutting and forwarding in one unit machine. The results showed that forest thinnings provide a potential resource for the sustainable production of bioenergy.     

木废料资源及其作为能源利用的前景

对木废料的来源，生成比例以及我国的木废料资源情况进行了,并从能源利用和环境保护两个方面，分析和展望了木废料作为能源利用的前景。如能充分利用木废料能源，则在一定程度上可以缓解能源供需矛盾，减轻环境污染，同时可以提高木材加工企业的能源自给率。     

Assessment of wood fuel use for energy generation in Lithuania

The paper investigates possibilities to use solid biomass (wood) resources. It provides detailed analysis on distribution of Lithuanian wood resources and evaluates possibilities to develop the use of above resources for heat and power generation. European Union as well as Lithuanian legislation declares promotion measures for wood as fuel for energy generation. Legal documents suggest implementation via subsidizing of raw material for production of wood chips for boiler-houses and adopting specific promotion program for the use of forestry biomass for boiler-houses according to which the difference between price and costs should be subsidized for producers of such raw material.Directive 2009/28/EB obligates separate countries to develop National Renewable Energy Action Plans (NREAP), which would provide specific promotion schemes and target indicators for each year (up to year 2020). According to this Directive the EU RES share in final energy consumption should reach 20%, and for Lithuanian this share should be no less than 23%, while district heating systems should use no less than 70%. At present the total capacity of wood-chip-fueled boilers reached above 476.1 MW. No series obstacles can be seen for extension of wood fuel use. The renewable energy compromise 18.1% of primary energy annual gross inland consumption and cut of the CO₂ emissions about 6% compared with the level on 1990. According to the Kyoto Protocol Lithuania must reduced green gas emissions 8% in the period 2008–2012. These goals can be realised by increasing of the use of biomass as fuel for the energy production.     

Interest in energy wood and energy crop production among Finnish non-industrial private forest owners

EU targets and regulations regarding energy production and the reduction of greenhouse gas emissions have been tightening in the 2000s. In Finland the targets are planned to be achieved mainly by increasing the use of biomass. Wood already accounts for a marked proportion of Finnish energy production, but additional reserves are still available. Energy crop production also has considerable potential. Practically all Finnish farmers are also forest owners. Therefore, private forest owners are in a decisive position regarding the supply of energy wood and crops in Finland. In this paper the future supply of biomass is examined according to their past behaviour, intentions and attitudes. Finnish forest owners have a positive attitude towards the use of wood and crops in energy production. Price is becoming more critical as a motive for the supply of energy wood. Recreation and nature conservation play a smaller role than factors related to wood production and forest management as for motives for harvesting energy wood. However, almost a half of forest owners in this study were uncertain of their willingness to supply biomass. This is partly due to limited knowledge of the issues involved in energy wood and agricultural energy crop production and the underdeveloped markets for energy biomass. In order to achieve the targets, supply should be activated by further developing market practices, information, guidance and possibly other incentives for landowners. In general, there is interest among landowners in increasing the supply of energy biomass. However, the growth of supply presumes that production is an economically attractive and competitive alternative, that the markets are better organized than at present, and that more comprehensive information is available about bioenergy and biomass markets and production techniques.     

西藏薪柴能源替代战略与总体规划的探讨

通过对西藏薪柴能源消耗中存在问题的分析,提出了薪柴替代能源的主要方式,及这些替代能源在生态、经济、社会上的效益,对比替代能源具有的优势,指出实施西藏薪柴能源替代战略势在必行。最后依据全面规划、因地制宜的原则,对西藏薪柴替代能源在总体上的部署规划作一些探讨。     

Multi-criteria evaluation of cooking energy alternatives for promoting parabolic solar cooker in India

The policy formulation for cooking energy substitution by renewables is addressed in multi-criteria context. A survey is conducted to know the perceptions of different decision making groups on present dissemination of various cooking energy alternatives in India. Nine cooking energy alternatives are evaluated on 30 different criteria comprising of technical, economic, environmental/social, behavioral and commercial issues. Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE), a multi-criteria decision making method of outranking nature is used to rank the alternatives. It is found that liquefied petroleum gas (LPG) stove is the most preferred device, followed by kerosene stove, solar box cooker and parabolic solar cooker (PSC) in that order. A sensitivity analysis is also carried out for identifying potential areas for improvement for PSC. On the basis of results, strategies for promoting wide spread use of PSC are formulated.     

Recovery of logging residues for energy from spruce (Pices abies) dominated stands

Vast quantities of logging residue are left behind on clearcut areas. Given the suitable transportation distance, environmental and economic circumstances, they provide a possible alternative for fossil fuels. However, distribution of residual biomass over large areas during the logging operation and trampling by machines hinders the recovery. The recovery enhancing effect of three single-grip harvester work techniques on the productivity of logging residue recovery for energy was studied. Forwarder productivity, distribution of effective work time, forwarding distance, load size and the residue yield were studied.A heavy forwarder with an enlarged 22 m³ load space was used. The average load size was 9 tonnes. More than 50% of the forwarder's work time was spent on loading the residues. The recovery output of the trampled residues from the strip road after a conventional harvesting method was 11.4 t/E₀-h for a 9 tonnes load and a 300 m transportation distance. In contrast, the single-grip harvester methods that aimed at the post-logging residue recovery increased the recovery output to 12.0–13.3 t/E₀-h. The load size was a more significant factor than the forwarding distance in terms of machine productivity. The yield of residue recovery after the conventional roundwood harvesting method was 58.4% and from 66.8% to 78.7% for the alternative single-grip-harvester methods.     

Production of hydrogen energy through biomass (waste wood) gasification

Biomass gasification, conversion of solid carbonaceous fuel into combustible gas by partial combustion, is a prominent technology for the production of hydrogen from biomass. The concentration of hydrogen in the gas generated from gasification depends mainly upon moisture content, type and composition of biomass, operating conditions and configuration of the biomass gasifier. The potential of production of hydrogen from wood waste by applying downdraft gasification technology is investigated. An experimental study is carried out using an Imbert downdraft biomass gasifier covering a wide range of operating parameters. The producer gas generated in the downdraft gasifier is analyzed using a gas chromatograph (NUCON 5765) with thermal conductivity detector (TCD). The effects of air flow rate and moisture content on the quality of producer gas are studied by performing experiments. The performance of the biomass gasifier is evaluated in terms of equivalence ratio, composition of producer gas, and rate of hydrogen production.     

Productivity and cost of mechanized energy wood harvesting in Northern Scotland

At present, the utilization of timber in the Northern part of the Scottish Highlands is low due to a lack of a wood utilizing industry. As a consequence, the majority of forest owners do not receive any income from timber and in some cases stumpage prices can even be negative. At the same time, increasing prices of oil, gas and electricity pose a great challenge for local industries and homeowners. The establishment of wood fueled heating systems is therefore expected to improve the situation and at the same time create a market for the local timber resources. Consequently, a local energy source to produce heat and electricity at a competitive price would have positive benefits for both local industries and forest owners. Due to the current lack of competition, roundwood could be chipped for fuel, which has many associated benefits compared to the harvesting and chipping of logging residues. It is the aim of this research to apply existing Finnish know-how in regards to wood fuel harvesting in order to develop and investigate the price level of sustainable and local wood fuel supply chains.To determine the most suitable supply chain for forest fuels, various research methods were applied. An estimation of the forest resources in the Wick area was the first step of the research. The different cost components of the supply chain such as cutting, forwarding and chipping were then calculated based on Finnish experiences and adapted to conditions in Northern Scotland. Detailed transportation distance calculations and cost of transportation were calculated using GIS tools.Of the various supply chain designs considered, chipping at the landing seems to be the most suitable option. Chipping the roundwood at a central terminal would also be feasible; however, a suitable site would have to be identified since chipping of the material at the heating plant is not an option. Calculations indicate that forest chips can be delivered starting from approximately 20 € MWh⁻¹ within a 50 km transportation distance when chipping is at roadside. If the transportation distance is 100 km wood chips could be delivered at approximately 23 € MWh⁻¹. Results from the GIS analysis indicate that a sufficient supply of raw material will be available in the future. According to these calculations forest fuels can be a competitive energy source for heat and electricity production in Northern Scotland.     

Economics of short-rotation intensive culture for the production of wood energy feedstocks

We review research and evaluate the economics of short-rotation intensive culture (SRIC) for the production of wood energy feedstocks in six regions of the U.S. The economics of SRIC are evaluated for present conditions under two sets of assumptions about anticipated advances in technology. The results show that delivered SRIC feedstock costs using available technology are likely to range between $3.00 and $4.10/GJ. Based on estimates of technological advances in tree breeding and selection, cultural management, and harvesting, delivered costs could be lowered to under $2.00/GJ. Advances in genetics, cultural management, and harvesting needed to reduce SRIC costs are technically attainable by the year 2000.     

Evaluation of the environmental impact of waste wood co-utilisation for energy production

The need for a practical, economic and environmentally sound solution for waste wood arises from the requirements for resource conservation and recent regulations. Co-firing with coal is a promising option for the thermal recycling of waste wood. The overall environmental impact caused by the co-utilisation of waste wood with coal was evaluated by using life cycle assessment as established by Society of Environmental Toxicology and Chemistry (SETAC) [A technical framework for life cycle assessment. Washington, DC: SETAC, USA; 1991, Guidelines for life cycle assessments: A code of practice. Brussels: SETAC, Europe; 1993]. This provides opportunities to evaluate direct environmental impact, to identify possible improvements, and to reduce energy resource consumption. In this work, the environmental impact of co-utilising lignite and waste wood in an industrial steam boiler was evaluated. Results obtained showed that co-utilisation is technically feasible and can meet strict environmental standards. A net decrease of CO₂ emissions can be achieved by the thermal use of waste wood, as well as conservation of fossil fuel resources, minimisation of waste disposal and reduction of impacts on health.