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The use of sustainably sourced biomass is an important tool for mitigating the effects of climate change; but biomass is far from being a homogeneous resource. The aim of this study was to examine the decision-making process of industrial end-users considering biomass procurement. An online, two-part survey generated responses from 27 experienced professionals, representing a portfolio of facilities varying in size, technology, and biomass types, across Australia, Canada, Finland, and Sweden. A PAPRIKA conjoint analysis approach was used to analyze the data so that the attributes that influenced procurement decisions could be weighted and ranked. The results provided an insight into end-users' views on factors including facility location, size, and biomass storage, handling, and procurement for different wood-based industrial services. The most important decision-making attribute appeared to be the type of biomass assortment, at individual, national, and aggregated levels. Of seven sub-categories of biomass assortments, sawdust (35%) was the most preferred type followed by stem wood chips (20%) and energy wood (15%). We concluded that, from the end-user's perspective, a pre-defined biomass assortment is the most important factor when deciding on feedstock procurement at a bioenergy facility. These results help us better understand end-users' perceptions of biomass properties in relation to their conversion processes and supply preferences and can inform product development and the securement of new niches in alternative business environments by existing and future biohubs.

The rising throughput of log-yards imposes new constraints on existing equipment and increases the complexity of delivering an optimal and uninterrupted supply of pulpwood to pulp mills. To find ways of addressing these problems by reducing log cycle times, this work uses a discrete-event mathematics model to simulate operations at a log-yard and study the impact of three different log-yard inventory strategies and two alternative machine systems for log transportation between main log-yard and buffer storage. The yard&rsquo, s existing inventory strategy of last load in and first out limits access to older logs at the main storage site. By allocating space for 89,000 m 3 and 99,000 m 3 of pulpwood at the buffer storage it is possible to keep the log cycle time at the main storage to a maximum of 12 and 6 months. Additionally, the use of an alternative log transportation machine system comprising a material handler with a trailer increased the work time capacity utilization relative to the yard&rsquo, s current machine system of two shuttle trucks and a material handler for transporting logs between the main and buffer storage areas. Compared to the currently-used last in first out inventory strategy and purposely emptying the main storage area once or twice per year did reduce the total work time of both machine systems by 14% and 30%. Consequently, the volume delivered from the buffer to the log-yard decreased on average by 17% and 37% when emptying the main storage area once and twice per year. Even with reduced work time when emptying the main storage area, both machine systems could fulfil given work load for transporting logs from the buffer storage to the main log-yard without interrupting operations of the log-yard.

This article deals with the topic of modelling the log-yard of one of our industry partners. To this end, our framework is based on discrete-events modelling (DEM), as consequence that many stages of the process run as a sequence of events. The sequence starts when trucks, trains or ships arrive loaded with logs to the log-yard. A machine unloads these logs and accumulates them in different storage areas. Consequently, a machine transports logs from these areas to the pulp mill, thus finishing the process. As using probability density functions is the core concept of DEM, the necessary process data to build these PDFs have been partly provided by the company. Other necessary data have been acquired through time studies, and by defining operational requirements. The company data tell when trucks, trains, or ships arrive to the log-yard, and the amount of volume they carry. The objective is to develop the necessary formulations, model calibration techniques, and software, such that computer simulations reproduce the quantities observed in these data. To this end, this work suggests two alternatives to analyse the data itself. These two alternatives lead to two different models: (1) The first being a hybrid model, in the sense that it involves the events in the process, and the logic decisions taken by machine operators for handling the incoming load, and (2) the second containing only the main mathematical essence of the process. After running 100 simulations, both mathematical models show that the simulated values for input and output, in terms of transport units and their volume, differ only by less than 3% compared to company data. The first model has also shown the ability to replicate the decision making that a machine operator undergoes for driving the logs to the storage areas, and from there to the mill. Therefore, the framework adopted provides the necessary mathematical tools and data analysis to model the log-yard and obtain highly reliable results via simulations.

Terminals and log-yards are becoming increasingly important in Nordic forest supply chains because of the need to support the rising production capacity of pulp mills and heat and power plants. Most modern terminals and log-yards handle multiple assortments, must accommodate multiple incoming and outgoing modes of transport, and have multiple storage areas. This complexity makes it challenging to find ways of increasing their efficiency. The design of more efficient terminals will therefore require a detailed understanding of the current state of forest terminals and the activities that occur within them. The overall objectives of this thesis are thus to provide a general overview of the current state of forest biomass terminals in Sweden, to determine the scope for upgrading biomass fuel at terminals, and to find reliable ways of analyzing log-yard and terminal performance. To achieve these aims, data were gathered by means of surveys, questionnaires, time studies, analyzing fuel-chip quality, and discrete-event modeling. The most pronounced differences were observed between terminals with areas of < 5 ha and those with areas of > 5 ha. Terminals of < 5 ha accounted for 65% of the country’s total terminal area, and terminals of < 2 ha handled half the country’s total terminal biomass output. Comminution activities were performed at 90% of all terminals, creating opportunities to add value to the processed material. By screening fine particles, it was possible to reduce the average ash content of the processed assortments to 0.66-2.17% (corresponding to a 20-31% reduction in total ash content). Screening could thus be used to divide chipped material into various quality classes suited for different applications with different price points. Models developed using production data for log-yards reliably predicted real-world outcomes over the studied time period and highlighted the importance of gathering relevant real-world data for meaningful analysis and improvement of log-yard operations. This thesis provides an overview of Sweden’s forest terminals, energy assortment quality, and potential operational improvements. The discrete-event models presented here are helpful tools for understanding log-yard operations and supporting decision-making by forest businesses.

Om en salixodling innehåller stammar med en diameter i stubbhöjd (dsh) grövre än 5-7 cm får konventionella direktflisande skördemaskiner tekniska problem. I dagsläget finns det i Sverige arealer med salix som växt sig övergrov. I dessa odlingar kan skörd med skogsmaskiner vara ett alternativ. Syftet med denna studie var att mäta produktiviteten på konventionella skogsmaskinsystem, anpassade för skörd av ”klena” stammar i gallringsskog, vid skörd av övergrov salix, samt att jämföra dessa systems kostnadseffektivitet mot konventionella system för salixskörd. Ett skördare-skotaresystem och ett en-maskinsystem (drivare) studerades vid skörd av normal och övergrov salix. Det normala området innehöll 36 ton torrsubstans (TS) per ha, en diameter i stubbhöjd (dsh) i medeltal och maximalt på 2,7 cm respektive 6,1 cm. Det övergrova området innehöll 56 ton TS/ha, en dsh i medeltal på 3,1 cm respektive 10,0 cm. Jämförande systemanalyser utfördes mot både konventionella och teoretiska salixskördesystem (baserades på litteraturdata) i normal, övergrov och mer övergrov (75 ton TS/ha) salix. Fältstudien visade att typ av odling hade störst effekt på skördarens produktivitet (tonTS/timme) vilken i medeltal blev 56% högre i det övergrova området jämfört mot det normala. Produktiviteten på skotaren påverkas främst av skotningsavståndet. Drivaren hade låg produktivitet som dock ökade med 36% i den övergrova odlingen. Drivaren påverkas också kraftigt av skotningsavståndet. Systemanalysen visade att skördare-skotaresystemet gav ett positivt netto i alla typodlingar, men att drivaresystemet gav ett negativt netto i alla typodlingar. Analysen visar tydligt att konventionella system för salixskörd blir mer kostnadseffektiva i alla typodlingar än skogsmaskinsystemen. Salixdirektflisningssystemet gav högst netto i det normala och övergrova området. Ett teoretiskt salixbuntskördaresystem gav högst netto i det mer övergrova området. Trenden är att systemet med salixdirektflisning och ett teoretiskt system med salixhelstamskörd och direktlastning minskar i kostnadseffektivitet med ökad biomassa/ha, men att skogsmaskinsystemen och salixbuntskördaresystemet ökar i kostnadseffektivitet med ökad biomassa/ha. Skogsmaskiner är i dagsläget inte ett kostnadseffektivt val vid skörd av salix, och kommer förmodligen aldrig att bli det heller. Dock utgör skogsmaskiner ett robust alternativ som alltid fungerar oavsett hur gamla och övergrova salixodlingar har blivit.