Utilization of woody biomass for energy is expected to increase rapidly and logging residues are a likely feedstock to meet increased demands. Potentials for increased biomass utilization have created concerns regarding possible impacts of using logging residues for energy. The overall goals of this project were to characterize biomass harvesting operations and to evaluate potential impacts on soil erosion and implementation of Best Management Practices (BMPs) for water quality on biomass harvesting sites. Results indicate that biomass harvesting was integrated into a wide range of logging businesses. Existing biomass harvesting businesses reported total production levels ranging from 6 to 250 loads per week. The majority (98%) of biomass harvesting operations utilized integrated harvesting techniques where roundwood and fuel chips were produced concurrently. Potential erosion rates and BMP implementation scores were evaluated on ten biomass and ten conventional harvest sites in the Piedmont of Virginia. This study of 20 sites found no significant differences in overall estimated erosion rates between biomass harvests (0.7 tons ac-1 yr-1) and conventional harvests (0.8 tons ac-1 yr-1) (p=0.8282). Additionally, there were no significant differences observed in overall BMP implementation scores for biomass (85.2%) and conventional (81.3%) harvests (p=0.5930). A separate, but related study evaluated BMP implementation over a three year period on 88 biomass and 284 conventional harvests in the Piedmont of Virginia. Within the seven logging related BMP categories, only the Streamside Management Zones (SMZs) category had significant differences between biomass (83.1%) and conventional harvests (91.4%) (p=0.0010). Implementation score differences were not caused by insufficient residues for stabilization of bare soil but were apparently the result of operational decisions which resulted in lower implementation of BMPs related to SMZs. Overall, these findings indicate that existing BMPs appear adequate to protect water quality on biomass harvesting operations in the Virginia Piedmont when appropriately implemented. / Ph. D.

Forests cover a large portion of the global land area and provide critical resources such as timber, food, and medicine in addition to playing a significant role in the global carbon cycle. As such, sustainable forest management practices are required to balance forest economies and climate change mitigation with other non-timber objectives. A key aspect of many sustainable forest management programs is forest monitoring, for which technological and methodological development has led to enhanced forest inventory (EFI) methods, many of which rely on remote sensing data from high-resolution light detection and ranging (LiDAR) and optical imagery. However, to date, current applications of EFI methods have mostly focused on timber attributes with limited research on non-timber attributes or analyses regarding multi-temporal monitoring, method scaling, or method transferability. The objective of this thesis is to expand applications of EFIs in monitoring and analysis through two distinct studies, first evaluating the utility of LiDAR-based EFI methods in multi-temporal silvicultural treatment assessment and secondly in the pre-harvest estimation of merchantable wood and non-merchantable wood left as logging residues. The first study evaluates a process that expands the sampling of fertilization treatment effects on forest stands to the wider treatment area by utilizing paired LiDAR blocks made up of raster cell estimates from a multi-temporal area-based model. Results showed promise for detecting treatment impacts on stand volume, biomass, and height and highlights the potential for the methods to be used as a means to rapidly expand analysis from sample plots to the entire treatment area. The second study focuses on the use of a hybrid area-based and individual tree EFI approach to model merchantable and non-merchantable forest wood volumes while exploring the scalability of these models to harvest blocks and the transferability to additional blocks without prior training. Results from this study indicated that models for both volume attributes are successfully scalable and transferable to harvest blocks. Overall, the research results presented in this thesis demonstrate the potential of enhanced forest inventory methods for the monitoring and assessment of timber attributes, such as wood volume or biomass, as well as alternative attributes, such as stand height, or non-merchantable wood volume, over multiple years. This work further demonstrates the potential for these methods to expand areas of assessment and increase prediction accuracies. / Graduate / 2022-08-17

Skogen har under lång tid använts som värmekälla. Genom att ta tillvara på grot (GRenar Och Toppar) vid slutavverkningar bidrar skogsägaren med förnybar energi som minskar beroendet av fossila bränslen. Denna studie behandlar attityder gällande uttag av grot vid slutavverkningar. Studien utfördes som en enkätundersökning bland skogsägare och skogsinspektorer anställda inom Södra. Studien visar att det är oron för näringsuttag från skogen och risk för körskador som är de största faktorer som gör att skogsägare har en negativ attityd gällande grotuttag vid slutavverkning. Studien påvisar vikten av att  kunskapsnivån behöver öka hos skogsägarna gällande grotuttag och dess effekter. En attitydförändring gällande grotuttag behövs för att säkra framtida potentiella uttag. De konsekvenser som attityderna kan ge är att det inte blir tillräckliga mängder grotuttag och att de mål Sverige sätter upp i framtiden därmed inte kan nås. / Forests have been used as an energy source for a long time. By taking advantage of logging residues at final harvesting, the forest owners contribute with renewable energy that reduces dependence of fossil fuels. This study concerns the attitudes regarding the collection of logging residues. The study was conducted as a survey which was answered by forest owners and employees that work with counseling regarding forestry. The survey shows that the major obstacles that gives negative attitudes of logging residues is the concern about the nutrient removal from the forest and damage dealt by machinery. The study demonstrates the importance of knowledge, and the needs to increase the forest owners knowledge about logging residues and its effects. A change of attitude concerning logging residues is needed to secure the future collection of logging residues. The impact that attitudes can give is that there will be insufficient quantities of logging residues in the future.

Abstract. The objectives of this thesis are to evaluate (1) the influence of slope aspect on boreal plant responses to clear-cutting and (2) the effects of post-harvest extraction of bioenergy (logging residues or slash) on plant composition, richness and performance in clear-cuts. Such insight is essential for understanding changes in species composition and richness in response to clear-cutting and application of intensified harvesting systems. The focus is on productive and managed spruce dominated forests and focal organisms are mosses, liverworts (i.e. bryophytes) and vascular plants. Space-for-time substitution studies were performed in south- and north-facing slopes located in 10 forests and 10 adjacent clear-cut stands in central Sweden. Differences between forests and clear-cuts were interpreted as effects of clear-cutting. The results show that the response of all three focal groups differed between aspects. More species were lost in south-facing slopes and clear-cutting reduced species richness of liverworts as well as of bryophytes and vascular plants associated with sheltered habitats. By contrast, clear-cutting caused no reduction in any group and more species were added in north-facing slopes. As a result north-facing clear-cuts generally had higher species richness than their forest counterparts. The disparate patterns in species’ response between aspects were most likely caused by initial microclimatic differences and a greater microclimatic change in south-facing slopes, in response to clear-cutting. A paired comparative study of conventionally harvested (i.e. slash left) and slash-harvested clear-cut stands was performed 5-10 years after clear-cutting in south-central Sweden. Both the species composition and the richness of mosses and liverworts were affected by slash harvest, whereas the composition of vascular plants was not. Slash harvest also reduced richness of mosses and liverworts associated with forests and organic substrates (e.g. dead wood and litter). Species richness of vascular plants and bryophytes associated with inorganic substrates (i.e. mineral soil) was unchanged. Differences between conventionally harvested stands and slash-harvested stands were most likely a result of reduced cover of organic material reducing substrate availability and shelter in the latter. Increased mechanical disturbance in slash-harvested stands that destroys remnant forest vegetation and favours pioneers may also play a role. A bryophyte transplant experiment was performed in seven clear-cuts in central Sweden and monitored over one vegetation period. The results show that logging residues (or slash) and forest edges may shelter ground-dwelling bryophytes by buffering the clear-cut microclimate. In conclusion, both slope aspect and extraction of forest bioenergy affect plant survival in clear-cut boreal forests. As surviving plant populations facilitate re-colonisation, north-facing slopes and conventionally harvested clear-cuts (i.e. slash left) may potentially recover faster than south-facing slopes and slash-harvested clear-cuts.

Biobränsle är viktigt för vår gröna omställning då det ger möjlighet att ersätta fossilt bränsle med förnyelsebart. Det finns en stor potential för att ökat uttag av grot, som är en form av biobränsle, i det svenska skogsbruket. I skogsbranschen har ett ökat fokus på minskade markskador förändrat skördarförarnas arbetssätt. Ris används i större omfattning till markförstärkning, vilket påverkar uttag av grot negativt. Anledning till att grot lämnas kvar på hugget kan vara både påverkbart och ej påverkbart. Genom att intervjua en fokusgrupp visar resultatet att en anledning till minskat uttag är att det inte i något beslutsled får någon konsekvens eller blir ifrågasatt om uttaget av grot inte blir som planerats. Det innebär att en stor mängd förnyelsebar energi i form av grot lämnas kvar i skogen.

En av de saker som avgör hyggesresters värde som bränsle är dess fukthalt. Det vore bra om det gick att uppskatta fukthalten hos hyggesrester som lagras utomhus i högar, utan att någon undersökning av materialet behöver göras. Syftet med detta examensarbete var att finna ett sätt att uppskatta fukthalten med hjälp av information om vädret, exempelvis nederbördsmängd, temperatur och molnighet, på den plats på vilken hyggesresterna lagras. Examensarbetet har inte lett fram till någon metod som på ett tillförlitligt sätt kan uppskatta fukthalten med kännedom endast om var (och därmed kännedom om ungefärlig väderlek) som hyggesresterna lagras. Fukthalten tycks i hög grad styras av andra faktorer än de som är kända i denna studie. De okända faktorerna är exempelvis trädslag, kvistarnas tjocklek, markbeskaffenhet och placering i förhållande till omgivande terräng.

Increased markets for renewable energy feedstocks have led to increased energywood production in the Southeastern United States. Energywood requires additional processing and is often the lowest value product generated, making profitability difficult. Additionally, numerous environmental concerns surround energywood harvesting, such as potential increased erosion, applicability and adequacy of conventional water quality best management practices (BMPs), increased area in road network features due to increased machine trafficking, and reduced quantities of residual woody debris. Energywood harvesting operations have been established in the lower Mid-Atlantic region of the U.S. for several decades, and research examining these operations provides insight into various aspects of the sustainability of the practice in this region and similar locations elsewhere. Therefore, this research provides a literature review on the practice of energywood harvesting, followed by four studies on energywood harvesting operations in the lower Mid-Atlantic region of the U.S. The first study evaluated the productivity and costs of two Appalachian Mountain and three Coastal Plain energywood harvests, providing stakeholders with a comparison of harvesting operations that can be used to make better-informed decisions regarding the efficient and economical harvest of energywood. The second study compared estimated erosion, operational feature areas, BMP implementation rates, ground cover characteristics, and downed woody debris quantities following 10 energywood and 10 conventional harvests in the Mountains of Virginia. The third study detailed a survey conducted among energywood business owners in Virginia designed to characterize harvesting operations and markets, assess business owner opinions related to the current and future state of the industry, and update/expand the results of a previous survey from 2014. The fourth study combined data from the second study with data from two other independent studies, comparing site impact metrics from energywood and conventional harvests across the Mountain, Piedmont, and Coastal Plain regions of Virginia. In the first study, cut and haul costs averaged $32.07/tonne and ranged from $26.19 to $38.28/tonne. Hauling consistently comprised the largest function cost at an average of $12.24/tonne. Harvesting system analysis also highlighted the importance of ensuring a balanced equipment mix to lower costs and ensure efficiency. In the second study, conventional harvests had higher estimated erosion contributions from skid trails (P = 0.089) and averaged more estimated erosion mass overall than energywood harvests, despite being significantly smaller in size (P = 0.054). There was significantly less area in heavy slash (P = 0.076) and lower estimated mass of residual downed woody debris (P = 0.001) on energywood sites than conventional sites (10.98 and 27.95 tons/acre, respectively). Site-wide BMP implementation scores (P = 0.041), as well as those for Streamside Management Zones (SMZs) (P = 0.024), and skidding (P = 0.063) were significantly higher on energywood sites than conventional sites. BMP implementation scores were significant predictors of estimated erosion rates (P < 0.001, R² = 59%), indicating that adequate levels of existing water quality BMPs are effective for erosion control on both conventional and energywood harvests. The third study indicated that energywood harvesting operations in Virginia were generally conventional single-crew roundwood operations utilizing their own residues for energywood. Production levels varied widely with energywood comprising an average 31% of total production. Material was comminuted utilizing large (650 median horsepower) older (13.2 years average) whole-tree chippers fed by a single loader. Coastal Plain operations were larger scale than Piedmont operations, though those in the Piedmont had been in business longer. Businesses had a median of $400,000 USD invested in energywood production equipment, which was double their median investment in the previous survey. Logging businesses that had produced energywood longer were significantly (P = 0.0391) more likely to report profitability. In addition, loggers reported deriving numerous non-market benefits from energywood production (e.g., improved aesthetics and cleaner sites, leading to increased landowner satisfaction), with most business owners planning to continue production in the future. The fourth study revealed that estimated erosion was higher in the Mountains due to steep slopes and operational challenges. BMP implementation varied by region and harvest type, with energywood sites having better implementation than conventional sites, and conventional Mountain sites having lower implementation than other regions. Sufficient woody debris remained for BMPs on both harvest types in all regions, with conventional Mountain sites retaining twice that of Coastal Plain sites. BMPs effectively reduced potential erosion on both site types; therefore, increased implementation could likely lower erosion potential in problematic areas. Collectively, this research provides a wholistic representation of energywood harvesting operations in the lower Mid-Atlantic region of the U.S., allowing stakeholders in the region and other similar locations to make informed decisions regarding its sustainable harvest. / Doctor of Philosophy / Additional markets for renewable energy feedstocks have led to increased energywood (biomass) production in the Southeastern United States. Energywood is wood that is often used in the place of coal for renewable energy production. This includes wood of insufficient size, poor form, or with no other higher market value at the time of harvest. It also includes both residues from logging operations as well as stands planted to be harvested specifically for bioenergy production. Energywood requires additional processing steps and is often the lowest value product on harvesting sites, making profitability difficult to achieve. Additionally, energywood harvests may result in negative environmental impacts, such as increased erosion, increased area in road network features, and reduced quantities of residual woody debris. Finally, Best Management Practices (BMPs) have been created for conventional forest harvesting operations, but their applicability to energywood harvests has not been verified. Therefore, this research provides a literature review on the practice of energywood harvesting, followed by four studies on energywood harvesting operations in the lower Mid-Atlantic region of the U.S. The first study evaluated the productivity and costs of two Appalachian Mountain and three Coastal Plain energywood harvests, providing stakeholders with a comparison of harvesting operations that can be used to make better-informed decisions regarding the efficient and economical harvest of energywood. It also highlighted the importance of ensuring a balanced equipment mix to lower costs and ensure efficiency, and the high costs associated with hauling. The second study compared estimated erosion, operational feature areas, BMP implementation rates, ground cover characteristics, and downed woody debris quantities following 10 energywood and 10 conventional harvests in the Mountains of Virginia. Conventional harvests were more potentially erosive and had lower BMP implementation rates than energywood harvests, despite energywood harvests resulting in lower quantities of residual woody debris. The third study presents a survey conducted among energywood business owners in Virginia designed to characterize harvesting operations and markets, assess business owner opinions related to the current and future state of the industry, and update/expand the results of a previous survey from 2014. Energywood harvesting operations in Virginia were generally conventional single-crew operations utilizing chippers with energywood comprising an average 31% of total production. Loggers reported deriving numerous non-market benefits from energywood production (e.g., improved aesthetics and cleaner sites, leading to increased landowner satisfaction), with most business owners planning to continue production in the future. The fourth study combined data from the second study with data from two other independent studies, comparing site impacts from energywood and conventional harvests across the Mountain, Piedmont, and Coastal Plain regions of Virginia. Estimated erosion was higher in the Mountains due to steep slopes and operational challenges. BMP implementation varied by region and harvest type, with energywood sites having better implementation than conventional sites, and conventional Mountain sites having lower implementation than other regions. Sufficient woody debris remained for BMPs on both harvest types, regardless of region. Finally, BMPs reduced estimated erosion on both site types, suggesting increased implementation could lower erosion potential in problematic areas. Collectively, this research provides a wholistic representation of energywood harvesting operations in the lower Mid-Atlantic region of the U.S., allowing stakeholders in the region and other similar locations to make informed decisions regarding its sustainable harvest.

Woody residues are byproducts with high lignocellulosic content, such as mill residues, logging residues, and other woody waste. This study estimated the impact of different mill characteristics, procurement attributes, constraints, and geospatial features on the utilization of woody residues to produce bioenergy by primary forest products manufacturers in the southern United States. Data were collected using a mail survey, and USDA and Esri geodatabases. Data analysis was conducted using analysis of variance, two-stage least squares, binary logit, and spatial logistic regression models. Approximately 70% of mills utilized woody residues for bioenergy purposes and 11% were willing to utilize additional logging residues to produce electricity. Mills were willing to pay US$12 (2012 dollars) per metric ton of logging residues at the mill gate and haul them for up to 93 kilometers. Mills with a larger capacity to utilize woody residues were more willing to utilize additional logging residues, pay a higher gate price, and haul them over longer distances. Regarding a mill type, pulp, paper, and paperboard mills and composite wood products mills were the largest woody residue utilizers and were willing to increase utilization of logging residues, pay higher prices, and haul them over longer distances. Utilization of woody residues increased with a processing capacity increase, equipment upgrades, and lower transportation costs logging residues. Mill willingness to utilize additional logging residues was higher for mills with the larger utilization of woody residues, lower quantities of disposable mill residues, anticipated equipment upgrades, and low importance for lack of storage space. Mills were more likely to utilize additional logging residues within proximity to a sawmill; pulp, paper, and paperboard mill; and a major road system, and less likely if a mill was in the vicinity of a river, forest, and mill producing other forest products. Results will help formulate future bioenergy policies, guide biomass energy investments and financial incentives, and help mill and land managers make more informed decisions regarding production and utilization of woody biomass. Future research is needed to evaluate the feasibility of utilizing logging residues by other facilities such as power plants and bioenergy facilities.

The forest constitutes a very important element of renewable natural resources and makes a significant contribution to the Swedish bioeconomy. Biofuels are Sweden’s largest source of energy; of all the energy we use, 32% comes from biofuels, and of this approximately 85% comes from the forest and the forestry sector. In spite of this, logging residues constitute only a small component, compared to for example byproducts from sawmills and pulpindustry, and there is considered to be great potential for increasing their use. In 2019 the Swedish Forestry Agency issued new recommendations for logging residue harvest and ash recycling. This was a further development of the 2008 recommendations, which formed the foundation for how forest fuel producers work today, and were based on several decades of research into, for example, the impact on forest productivity and technological development of machinery. This practice of logging residue harvest aims to yield a dry and defoliated fuel where the needles are left at the clear felled area. However, if we are to increase the use of green renewable energy from forestry, it is very important to understand how different procurement systems affect the handling and storability of fuels from a quality perspective. It is also of great importance to understand, from the forest owners’ perspective, how removal of additional products from forestry influences nutritional balance and long-term productivity. If harvesting of logging residues does not affect long-term productivity, it is up to small-scale private forest owners to decide if removal of logging residues will be performed on their land. This thesis addresses some of these issues regarding removal of logging residues from the point of tree harvest up to the point of delivery to the energy conversion industry when the fuel chips are measured. Regarding different methods of handling of logging residues, the traditional method – dry-stacking – was compared with the, fresh-stacking method. The logging residues investigated came from stands that mainly consisted of Norway spruce (Picea abies (L.) Karst). The loads investigated in Paper 3 also came from logging of spruce-dominated forests. Both methods aim to dry the logging residues to an acceptable moisture content for delivery to the energyconversion industry. For the later part in the supply chain, moisture content measurements of logging residues were compared during a winter and summer season. The results of the studies indicate that the two methods do not create results that differ from what is allowed by the Swedish Forestry Agency and that they are quite similar with respect to dry mass- and nutrient removal from the clearfelled area. The results also show that similar yields and distributions of material are obtained from the logging residues with different stacking methods; in addition, the final felling itself, combined with the work performed by the forwarder operator, has a greater impact on the result than the method chosen for residue stacking of the logging residues. For the individual clear-felled area and the individual forest owner the increased removal associated with freshstacked logging residue has no major impact, however from a national perspective this small increase in removed logging residues may yield a supplement of between 0.5 – 1 TWh of green energy annually. Regardless of treatment, the studies indicated that the delivered fuel chips will have similar characteristics. The moisture content measurement techniques currently in use are sufficiently accurate and reliable. However, if the forest owner is unlucky and an error in measurement occurs or comminution and delivery happens during an especially wet period they may suffer a significant financial loss; indeed, it is generally not under the individual forest owners’ control when the logging residues are comminuted and delivered.

Iron production accounts for substantial shares of global coal use and GHG emissions. LKAB is Europe’s largest iron company and Sweden’s fourth-largest emitter of GHGs. To reduce its emissions, LKAB might implement biomass in iron ore pelletisation. It is therefore important with information on how the biomass demand can be met and what the environmental implications may be, but available research focuses on contexts which are irrelevant for LKAB. This study aims to fill this knowledge gap by investigating the extent to which LKAB can replace coal with biomass in iron ore pelletisation by assessing the availability of biomass as well as its environmental and economic performance relative to coal.  The study includes slash, industrial residues, pellets, and willow. The biomass potential is assessed using statistics and calculations. The environmental performance is assessed based on an LCA combined with a qualitative sustainability assessment, covering land-use change (LUC), biodiversity, toxins, chemicals, eutrophication (toxic-chem-eut), and compliance with EU sustainability criteria. The economic performance is based on price statistics. In general, all assessed biomass sources can meet LKAB’s potential demand, but requires sourcing from different locations, at different prices, with different environmental impacts, and with different market effects. In northern Sweden (“Norrland”) slash is largely unused and has a very good potential to supply LKAB with biomass. Industrial residues have a good potential on the domestic level but lower potential regionally. The potential of domestically produced pellets is limited but the demand can be met by increased production or imports. Willow currently has a low potential, but there is good potential to increase domestic production. In general, the biomass fuels have substantially lower environmental impact than coal. The LCA indicates that slash and industrial residues have the lowest environmental impact, pellets has slightly higher, and willow has higher impact in most categories (also higher than coal in some categories, although lower in general). Slash, industrial residues, and pellets cause no impacts on LUC, biodiversity, and toxic-chem-eut. Industrial residues, pellets, and willow are compliant with EU sustainability criteria, but it is uncertain if slash complies due to a pending criteria revision. Willow has slightly positive impacts on biodiversity and toxic-chem-eut but slightly negative impacts on LUC. The cost for biomass relative to coal is uncertain due to price volatility. In 2020, coal had the lowest price, but its average price the past three years is twice the price for slash and industrial residues and on par with the price for pellets. If all fossil GHGs in iron production would be subjected to the EU emission trading scheme the economic competitiveness of biomass would increase. The study shows that increased use of biomass, both in LKAB and in general, can be achieved with reduced environmental impacts compared to coal. Future studies should map the effects of dynamic factors on environmental impact and costs, and quantify net environmental impacts, including spatial-specific changes. / <p>Betygsdatum 2023-07-07</p>