Development of standardized evaluation methods for harvesting machines and systems

Biomass 22 (1990) 195-209

Development of Standardized Evaluation Methods for Harvesting Machines and Systems W. B. Stuart School of Forestry and Wildlife Resources, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0324, USA

ABSTRACT This effort, supported by Canada, New Zealand, Sweden, and the US, pursued three approaches to the problem of evaluating harvesting machines in terms which could serve international clientele. The first, rationalizing work study and reporting processes, documented and compared measures of interest among a varied set of countries. The second focused on modeling and analytical approaches" to develop comparable criteria. The third brought together 40 specialists from around the world in two workshops to discuss the impact of 10 factors which shape national perspectives. Key words: harvesting systems, evaluation, fuelwood.

INTRODUCTION

The problems of translating harvesting research findings across regional and national boundaries has confounded the development of international cooperation in machine and systems development, testing and application in conventional forestry. Initial expectations were that energy wood systems might avoid this complexity because this was a new wood assortment emerging in the market at a later stage in technological evolution than the more prosaic pulpwood, veneer and sawlog products. However, early reports on the production of this new product built on the established base of harvesting research and reporting procedures. Harvesting research is an applied science, responding to the needs of the clientele of the agency or associations performing the analysis. 195 © 1990 International Energy Agency

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Consequently, only that information necessary for an informed evaluation in the local environment is dealt with. Many factors which would be critical in determining the suitability of a design, machine, system or process in another environment are taken as fixed and not discussed. The result, for those not familiar with the local environment, is reports which provide considerable technical information but little insight concerning the hows and whys that support the machine and activity. This project has been directed at ways of correcting these deficiencies. Three separate approaches have been attempted during the life of the project -- rationalizing work study and reporting processes, modeling and analytical approaches and, finally, gaining a perspective of the origin and strengths of national and regional prerogatives which determine local approaches. The first stage involved reviewing published reports from around the world, identifying common and disparate measures or methods and attempting to develop a methodology for data collection and reporting which satisfied the needs of most parties. ~ The general summary of reviewers' comments was that, while the approach was interesting, the only information deserving serious treatment was that which met their own local needs. The methodology was tested in a series of trials in New Zealand and the US. The New Zealand effort was in collecting support information for a study of wide-tired equipment on steep slopes. The US trials used the procedure as a basis for documenting the physical, operating, and business environments for small-tree handling and harvesting systems in the southern US 2 and a study comparing the productivity, costs, environmental impacts and damage to residual stands of large and small grapple skidders in southern pine thinning applications3 The latter applications demonstrated that the data collection procedure captured information concerning machines and systems which would have escaped more conventional documentation efforts but which were key to job performance. These included equipment purchase strategies, labor stability and job management. The second approach, modeling and analysis, met a similar fate. A cooperative project with the integrated harvesting activity was undertaken to compare the performance of various harvesting systems across national boundaries using simulation. The performance of British, Canadian, New Zealand, Swedish and US systems were simulated in the stands and working environment of the other four countries. Reviewers' comments on the final report again demonstrated the strength of national and regional perspectives. 4

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The third activity, exploring the origins and strengths of these perspectives, involved identifying a subset of 10 of the forces shaping these viewpoints, discussing and comparing them in two workshops. Forty specialists in harvesting, drawn from government, research associations, universities, the forest industry and the equipment industry, presented papers, published in workshop proceedings, which discussed national perspectives and constraints. These conferences demonstrated that even among a selected set of highly developed countries producing similar products, the working and business environments differed greatly. These differences, not the mechanical, productivity or cost characteristics of the machine or a system, were the final determinants of successful adaptation and evolution. 5 WORK STUDY, RATE SETTING AND CONTRACT PRICING The forest industry world-wide is increasingly turning to contractors to perform harvesting activities, yet the meaning of 'contractor' differs widely: (a) In some environments, contractors can work closely with and be buffered by either the landowner or the purchasing firm; rates are established based upon an extensive set of work studies. Contracts are let for multi-year terms with annual re-negotiations. 6 (b) Functional contracts, one-man/one-machine contracts which are independent of other activities in harvesting, are common in other environments. These contract agreements generally span a year or more and often represent only a labor payment plus an allowance for the use of the associated machine. 7 (c) In others, the contractor/contractee role is rigorously defined by law, buffering by any party is severely limited; rates are negotiated on an open-market basis using recent historical performance as a guide, on a tract-by-tract or pro-object basis. 8 (d) A variety of alternative agreements exist, each differing in the ability of the contractor to re-negotiate and in the ability of the contractor to influence the selection and application of equipment. The method and timing of payment also differs widely: (a) At one extreme, the contractor is paid on the basis of work in progress; a functional contractor cutting and piling wood is paid on the basis of field measurement of his output, v

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(b) In other environments, payment is required when wood is 'uplifted' from forest landings; the costs of carrying in-woods inventories falls on the contractor. 6 (c) In others, the contractor is paid on deliveries to the market, usually on a weekly or bi-weekly basis, but sometimes a check is cut for each individual load. 9 The basis for payment is uniformly scaled volume or weight. However, the responsibility for separating out the quality assortments and expediting scaling differ widely. Systems and machines, to survive in an environment, must accommodate local practice. As the project progressed, an awareness arose that there are essentially two separate administrative strategies for logging operations, one based on measurement, the other on management. The m e a s u r e m e n t approach incorporates measurement points in the job layout where material is aggregated, identified by producer and held for measurement. Each individual or crew in the work force is then paid on the basis of their production over the measurement period. The m a n a g e m e n t approach relies on an on-site supervisor managing the operation and attempting to optimize production. The supervisor has the responsibility to re-assign men, machines and operations to resolve production problems or to take advantage of an opportunity. Crew rewards may be based on straight wages, wages plus production bonuses or piece rate, depending upon individual agreements with the contractor.

MACRO-ECONOMIC AND SOCIAL ISSUES Forest policy and social policy are nearly inextricably entwined in most countries. Forest employment, especially in harvesting, is often regarded as a means of maintaining population distribution, providing appropriate land use and moderating shifts in employment in rural economies. As a consequence, harvesting is shaped by cultural, political, social and economic forces. An interesting contrast exists between countries such as Canada, Sweden, and the US, where timber has been an integral part of local economics for centuries, and New Zealand and Ireland, which are currently afforesting areas from which timber has been gone for generations in the case of New Zealand, or centuries in Ireland. The problems encountered in re-establishing a forest culture, developing a labor pool for forest or mill workers and establishing the necessary infrastructure to support a modern industry are quite complex."', J]

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Forestry escapes few of the broader social movements within a country. Urbanization, changes in agricultural policy, technological changes in the larger industrial base, the health of the national economy, the strength of the national currency and the environmental ethic adopted by local and national governments all influence the type and rate of development. Political forces, whether in the form of land use debate, labor legislation, direct economic development incentives, water and air quality standards, road construction and maintenance budgets or simply public image, further complicate the process. The ingenuity of cultures is expressed in the diverse ways they react to a seemingly similar set of stimuli. These reactions then form the basis for future development. The southern US and Sweden both entered the post-WW2 era under similar circumstances: an increasing market for forest products, extensive acreages of merchantable timber, a diminishing rural labor force and an active forest industry. Development was parallel through the introduction of the chain saw; then national prerogatives entered, leading one country toward the development of sophisticated shortwood systems, the other toward sophisticated tree-length harvesting. A variety of reasons have been offered, each of which partially explains the enigma. A full understanding will likely find the final explanation is more in the domain of macro-economics and social issues than in the technical capabilities of either harvesting approach.

MECHANICAL AND ERGONOMIC DESIGN The level of mechanical and ergonomic design demanded and supported by a local forest industry is the product of the broader base of industrial technology within the country, the hostile or benign nature of the working environment, the availability and expectations of the forest work force, the ability to support technology through a parts and service network and legal constraints. A machine feature, such as a climate-controlled operator's compartment, which is considered a necessity in one country, may be considered an unsupportable luxury in another. Local environments may require machines to be designed from the 'ground up' in one country, while a second may find attachments to base machines from the construction or agricultural industries a suitable alternative for performing the same task. Design philosophies of both manufacturers and purchasers impact directly on machine acceptability. The philosophies often derive from a combination of past experience, the relative scarcities or cost of capital

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and labor, worker capacity and training and an undefinable perception of 'what a piece of woods machinery should look like'. Broad design parameters have evolved within the cultural and industrial context of a nation. 'Successful' designs, knowingly or unknowingly, incorporate these concepts into special-purpose machines. Machines and systems based upon individual operators working long hours in even the most advanced ergonomically designed cab will not survive in a culture where crews are accustomed to frequent, even brief, interaction with other crew members. Agriculture-based economies often begin the process of forest mechanization relying upon farm equipment and concepts. Mining, railroads and longshore industries have contributed to the logging culture adjacent to areas where they were common.~2 The influence can also be manifested in the attitude toward equipment and the desirability of obtaining specific skills. A labor pool comfortable with acquiring the skills necessary to operate and maintain a variety of rather straightforward, robust machines is most comfortable with and receptive of the base machine plus attachment design approach for single-function machines. A society which regards specialization as a key to job success and longevity will be more receptive to more complex machines requiring special training. Safety and comfort requirements vary with the forest type and operating environment. Basic requirements such as rollover and fallingobject protection are reasonably common across national boundaries, while local requirements for limb risers, screens, perspex, lighting, cab interior design and control layout are determined by local needs. Whether the operator's compartment is expected to provide only partial modification of the ambient environment or to approach a home or office condition is a function of the operator's expected period of residency. A cab which will be occupied by the same individual for periods of 8-12 h per day must be different from one occupied for uninterrupted periods of minutes or a few hours, t3

UTILIZATION AND RELIABILITY Machine utilization is a composite measure that includes the effects of machine reliability, job organization and the working environment. Reliability or availability reflects the quality of the machine design and components, parts and service back-up and on-the-job maintenance. Machine and job-related influences are difficult to separate to the extent that the terms are often used interchangeably. 14

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Acceptable limits on these parameters and strategies for achieving these limits vary according to machine environment, application, support services and accounting philosophy. Acceptable levels of reliability may be achieved in one environment by selecting the simplest, most robust machine available at the expense of productivity or operator comfort. An operation working with minimal support services in a location far from parts or service back-up may find a strategy based on simple, robust, easily maintained but less productive machines most desirable. A different environment may determine that sophisticated, highly productive equipment may compensate for the additional training and support necessary to sustain the operation.~5 Utilization and reliability are often judged by 'rules of thumb' or general guidelines which have evolved with industry. Meeting these guidelines is no guarantee of success for a new machine. Failure to meet the guidelines, however, enhances the probability of failure, j6 Strategies for achieving a high level of reliability have also evolved along similar lines without the necessary assessments to determine the efficiency of a particular approach. Alternate strategies to the traditional shift-based preventative maintenance are emerging which may prove more efficient. Utilization is often a culturally based parameter, a function of job administration, acceptance of work patterns and market forces. Weather conditions, quotas, 'hot' or 'cold' logging strategies, single- or multipleshift work, roadside inventories and labor legislation all influence utilization limits that can be sustained. The diversity in form and interpretation of utilization and reliability measures demonstrate the lack of commonality of purpose for these measures and how easily the objectives of measuring machine mechanical performance and system economic performance become mixed. In some environments they are synonymous: the machine is the system; if any component fails, the process stops. Multiple machine systems tend to be more organic. If one limb or member fails, others can adapt to allow the total organism to continue functioning. The occurrence of the failure is important, but equally important is whether the organism can continue to function effectively until the system is 'healed'. Utilization also reflects the owner's personal business philosophy. One owner may be satisfied if a piece of capital equipment is returning a reasonable rate of return on investment at a 50% utilization because the temporal life of the machine will be extended. Another is not satisfied unless the utilization and hence the profitability of the machine is optimized. The arguments that an airline attempts to maximize load factors and air time on a plane are offset by the fact that an undertaker does not on his hearse.

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ENVIRONMENTAL CONSIDERATIONS Environmental considerations are emerging as a major issue in most forested countries. The forces behind these rising concerns are both local and global. These concerns are gaining strength as local actions, such as deforestation in the Amazon, are attributed with global impacts. Harvesting, by its very nature, must have environmental consequences. The nature and extent of these consequences are imperfectly understood and appreciated. The effects are a function of soils, topography, rainfall patterns, species, type and timing of the harvest, equipment used and operator skills. Environmental considerations of broad public interest, such as water and air quality, erosion and flooding, as well as aesthetics, are commonly dealt with through regulation or legislation. Authors of these often have limited understanding of forestry, forest ecology and forest industry and may or may not have proof that the activity being proscribed is actually harmful. Machinery manufacturers must strive to serve the largest possible market to recover development costs and achieve economies in manufacturing. This increasingly implies international rather than regional and local markets. Unfortunately, the research base for defining the impact of machine and systems on foreign environments is very limited. A machine feature or capability that is beneficial in one environment may be detrimental in another. Harvesting machines and systems have been attempting to accommodate the environment during the period of mechanical evolution. The motivation for this has not been to meet an altruistic environmental ethic, but because wasting energy and abusing the ecosystem is costly. The adaptations are often subtle and not apparent to those unfamiliar with local or regional conditions and operating practices, and seldom explained except in special reports. A common practice is for the reader to interpret or overlay statements onto his biological, geological, climatic and cultural environment. Environmental considerations are going to become more constraining on harvesting activities. Those activities which affect public attitudes toward timber harvesting and those which affect post-harvest site productivity must be identified, documented and dealt with locally. International efforts toward a greater understanding of the derivation and mechanics of these impacts are required to support future development.

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EQUIPMENT MANUFACTURING AND MARKETING These activities are as reflective of national cultures as any of the components discussed previously. The status of a country as a net importer or exporter of equipment is a function of its industrial history, which in turn is a product of its natural resources, social development, the size of the internal market, success of national innovations and location with respect to the world's trade routes. These coalesce into a national attitude or perception which shapes the growth of the industry. This process is further complicated by preferences for items as diverse as hydraulic pressures and bolt dimension. Forestry, in most countries, does not provide a sufficiently large market to support major initiatives in machinery development without significant government support. The four common strategies are: (a) adapting equipment from other industries; (b) developing a basis of local job shops which provide equipment for local markets; (c) importing purpose-built equipment and modifying it; and (d) developing a forest equipment industry which is dependent on national and international sales for survival. The first two strategies, adaptation and local manufacturing, are often successful during the nascent stages of forestry development. The most critical international exchanges during this period are concepts and components. The interchange of concepts is important, because directions taken at this stage may determine the direction of industry development and the future markets for equipment. Marketing components serve a similar strategy by providing brand-name recognition and establishing standards. These tasks can be accomplished with tolerable expenditures and risks on the manufacturer's part. Product applications specialists and local industrial supply houses require support, but major outlays in engineering and market development are avoided. 16 The import/export mode is more risky for all parties involved in this era of increasingly refined technology. The situation of one manufacturer graphically illustrates the manufacturer's quandary. For the firm to compete effectively for the hydraulic log loader market in 1977, it required a line of seven different loader types or series, with 24 model variations and no special adaptations. In 1986 the number of series had increased to eight and the model variations had grown to 134, with an

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extensive list of add-ons and specials. In 1986, 44 other companies were competing in the loader market in the US. Twenty companies were building loaders for self-loading trucks, 18 were building specialized turntable loaders for forestry applications, and 14 were manufacturing excavators with loader modifications. The competition for a relatively small market leaves little room for marketing error or cushion to support the expense of penetrating foreign markets. Import duties, exchange rate fluctuations, licensing and permit systems and the cost of translating marketing service and other material into different languages can be overwhelming for a short-line manufacturer.~7 When the technical, legal, and financial morass has been conquered, the manufacturer must then deal effectively with cultural constraints. The fit with local working methods, timber, product type, parts and service expectations and labor skill levels must be uncomplicated. Few organizations are willing to alter their feet to fit a new pair of shoes. The increased internationalization of the forest products industry is expected to bring with it increased internationalization of the forest equipment industry through expanded marketing efforts, purchasing local firms, cooperative marketing agreements and creating subsidiaries. This process may result in a gradual dissolution of regional or national preferences and, hence, in a greater homogeneity of forest equipment and operations.~8

ENTREPRENEURIAL EVOLUTION AND INPUT Entrepreneurial evolution in most of the participating countries depends upon ingrowth from the conventional forest harvesting force or from individuals providing energy wood for their own use and using the market to dispose of surpluses. In both instances, the producer survives as a price taker rather than a price setter. All participating countries reported excess production capacity given the current market size. Entrepreneurial survival will be a more significant concern than entreprenurial development for the immediate future. One study demonstrated that, for the southeastern US at least, biomass supplies could be increased at least cost in areas of intensive forest harvesting activities. The availability of entrepreneurs, equipment, labor skills and harvesting infrastructure in these areas would expedite the production of fuels from an energy wood only or integrated operation. The analysis also indicated that the current production levels could

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be increased several-fold before the production of energy wood would have any significant effect on conventional stumpage prices.~9 The regions with the greatest standing inventory, the mountains and the wetlands, also had the highest development and production costs, indicating that the cost of alternative energy would have to rise considerably before the full potential of the resource would be realized.

CAPITAL AND CAPITAL FORMATION Capital and capital formation are significant problems in most of the industrialized countries. Governmental support in the form of grants, tax credits or reduced interest rates for energy production are diminishing. The current or aspiring contractor is therefore forced to compete in the commercial and industrial credit market. Conventional lenders are marginally familiar with normal logging activities and are extremely hesitant about putting money into an even less predictable biomass production industry. 2° The equipment industry is a major source of financing for harvesting equipment, either through a credit arm of larger manufacturers or through financing arranged by local dealers. Biomass harvesting equipment that is an adaptation of conventional logging equipment by a name manufacturer can often qualify for these loans. Financing for specialized equipment, innovative equipment from job shops and small manufacturers and other more exotic machines is difficult to arrange. Consequently, the continued development, refinement and acceptance of even the most promising equipment is impeded because of financing difficulty. An alternative strategy for avoiding financing costs is to use small farm-tractor-based equipment. These machines often require significant inputs of manual labor, are sensitive to weather and timber conditions and have their working season shortened when the tractor is also used in agricultural production. Many biomass harvesting enterprises begin as sole proprietorships, general or limited partnerships. In these business structures, the entrepreneur is assuming considerable personal financial risk when entering into any borrowing arrangement. The lender has recourse in most countries to the contractor's personal as well as business assets if the undertaking is unable to repay the loan on time. Consequently, the availability of financing is a significant real and psychological barrier to business start-up.

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MARKETS, MARKET STABILITY AND MARKET ALTERNATIVES Markets, market stability and market alternatives are potentially limiting factors to further development. The markets which blossomed in the elevated oil prices of the 1970s are withering due to depressed oil prices of the late 1980s. Prospects are promising only in those countries where oil prices are elevated by excise taxes, such as Denmark, in regions where alternate energy forms are expensive because of location or where industries have made and amortized the investments necessary for using woody fuels, such as the Piedmont region of the southeastern US. Each drop in oil prices causes additional markets to become submarginal and, hence, lost. Wood-using industries, district heating plants and institutions remain major consumers. Wood-using industries realize dual savings from reducing solid-waste disposal costs while reducing cash outflows for energy. The refinement of wood burning technology has increased uses and improved economics. Direct-fired dry kilns are usually favored over boiler-powered kilns in the southern pine industry in the US. District heating plants and institutions are public or quasi-public undertakings which can achieve additional benefits from stimulating local economies through the purchase of locally grown and produced fuels. The latter is especially important in regions of plentiful wood supplies and high unemployment rates. 2j The search for alternative markets for biomass was left behind in the pursuit of energy development. High fuel prices provided the stimulus for development of a new forest product -- biomass -- but the full value of this new product is still largely underdeveloped. A few alternate markets are emerging and older, traditional niche markets are expanding. Chunkwood is being used on a trial basis as a road-building material. Sawdust is being converted into cat litter using technology developed for producing pelletized woody fuels. Markets for horticultural mulch have expanded to the point that at least one US pulpmill is selling bark to a mulch processor and replacing it in the boiler with purchased sawdust. The list of these alternate specialty markets is extensive, but unfortunately each only consumes a small portion of the possible production. Expansion is possible in some; others cannot undergo significant expansion without significantly depressing prices and profitability. 22 Some of the energy-related technologies have stimulated interest in expanding markets for biomass components such as dissolving cellulose, lignin, furfurol and hemicellulose, which may develop into important

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chemical products with applications sufficiently extensive to support large markets. Integrated marketing of marginal biomass products will be as crucial to long-term development as integrated harvesting. The biomass harvesting contractor cannot survive in a market place typified by seasonal activity and intense price competition.

LAND USE POLICIES AND LONG-TERM SUPPLY Land use policies and long-term supply issues were not felt to be among the major concerns of participants in the project. Current potential supplies so outstripped markets that scenarios which hinted of shortages were difficult to visualize. Several factors were recognized which could operate to increase or decrease these supplies. International pressures are decreasing agricultural subsidies, a process which will force an increasing number of marginal farms out of business. The net effect will be to increase the amount of easily accessible arable or grazing land available for shortrotation or conventional biomass production. The question remains whether these lands will be aggressively restocked in trees or allowed to reforest more slowly through the vegetation succession process. Pressures are building in developed countries to decrease the amount of forest harvesting taking place and to enforce regulations and practices which minimize short- and long-term environmental impacts of forest operations. The concerns and pressures are real, and the long-term effects are unpredictable. The effect in the US will likely be that harvesting will be restricted on many sites that are currently considered productive forest, thereby decreasing available supply; constraints on equipment and practices will likely increase the cost of operations sufficiently on other sites to force them into a sub-marginal classification. SUMMARY A concept of 'harvesting ecology' has emerged from the project to reflect a recognition that the environment of a harvesting operation is as crucial to its long-term survival as the appropriate light, water, temperature, soil depth and soil pH is to the survival of a growing plant. If anything, the harvesting ecosystem is even more complex. It includes the normal range of natural factors -- weather, soils and plant communities. These are

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further complicated by technological, social, business, financial and political factors. The terminology which describes these latter factors is less discriminating and definitive than that used to describe the natural factors. International cooperation and exchange of technology, methodology and practices requires a greater understanding of these forces. A simple description couched in terms of productivity, availability and simplified costs for a machine provides only the initial explanation of the potential of a machine or system. The full potential cannot be assessed until the full 'fit' with the operating environment is understood.

REFERENCES 1. Sobhany, H., A method of data collection for the evaluation of forest harvesting systems. PhD dissertation, Industrial Forestry Operations Research Cooperative, Virginia Tech, Blacksburg, VA, 1984. 2. Corwin, M. L., A documentation and analysis of the physical, operating and business environments for small-tree handling and harvesting systems. MS thesis, Industrial Forestry Operations Research Cooperative, Virginia Tech, Blacksburg, VA, 1987. 3. Robe, S. C., Comparison of a large and small grapple skidder in a pine plantation thinning application. MS thesis, Industrial Forestry Operations Research Cooperative, Virginia Tech, Blacksburg, VA, 1988. 4. Beardsell, M. G., Stuart, W. B. & Mitchell, C. P., Harvesting Simulation Studies. Swed. Univ. Agric. Sci., Garpenberg, 1984. 5. Laestadius, L. H., Machines and systems evaluation -- how national perspectives differ. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Dept of Forestry, Virginia Polytechnic Institute, Blacksburg, VA, 1988, pp. 1-7. 6. Johnson, T. W., The evolution and status of work study in New Zealand. In Proceedings, HarvestingMachines and Systems Evaluation Workshop, ed. W. B. Stuart. Research notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 9-24. 7. Liden, E., Contract chippers' work situation: A case study on economics and organization for chippers in Dalarna. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Dept of Forestry, Virginia Polytechnic Institute, Blacksburg, VA, 1988, pp. 9-17. 8. Dodge, D., Forest workers in the Southern United States. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 81-4. 9. Shaffer, R. M., Structure for determining logging contract rates in the Southern United States. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart, Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 35-8. 10. Aldwell, P. H. B., Social and economic effects of forestry in New Zealand: A review of issues and research. In Proceedings, Harvesting Machines and

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Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 51-68. Phillips, H., Evolution of harvesting systems in Ireland. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 69-80. Pierrot, V. C., Improving productivity with ergonomic design. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 127-34. Kelly, K. J., Some factors influencing the development and acceptance of harvesting machines: A manufacturer's viewpoint. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 205-14. Bjerkelund, T. C., Machine utilization considerations for tree harvesting machines and systems evaluation. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 137-42. Sewell, W. D., Manufacturing, marketing, and importation considerations for logging machinery in New Zealand. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 1081987, Swed. Univ. Agric. Sci., Garperrberg, 1986, pp. 215-30. Stephenson, E., Utilization, reliability, and repairability considerations in US timber harvesting systems. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 165-74. Crawford, M., Market and marketing influences: Hydraulic knuckleboom loaders. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 237-45. Elofson, H.-A. (1986). Manufacturing and marketing forestry equipment: A Swedish perspective. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Research Notes 108-1987, Swed. Univ. Agric. Sci., Garpenberg, 1986, pp. 231-6. Young, T. M., Thomas, J. D., Ostermeier, D. M., Brooks Jr, R. T., Mulach, R. W. & Rowland, E. B. (eds), Economic Availability of Woody Biomass Fuel Chips for 13 Southeastern States. Tennessee Valley Authority: Muscle Shoals, AL, 1989. McNeel, J., Capital and capital formation for logging enterprises. In Proceedings, Harvesting Machine and Systems Evaluation Workshop, ed. W. B. Stuart. Dept of Forestry, Virginia Polytechnic Institute, Blacksburg, VA, 1988, pp. 34-42. Owens, E. T., Wood energy markets: Stability and alternatives. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Dept of Forestry, Virginia Polytechnic Institute, Blacksburg, VA, 1988, pp. 53-7. Grace, L., Alternate methods of wood residue utilization. In Proceedings, Harvesting Machines and Systems Evaluation Workshop, ed. W. B. Stuart. Dept of Forestry, Virginia Polytechnic Institute, Blacksburg, VA, 1988, pp. 71-5.