Mikko Havimo

A literature-based study on the loss tangent of wood in connection with mechanical pulping

In mechanical pulping, wood is dynamically loaded, which causes large heat losses due to wood viscoelasticity. The heat losses depend on the loss tangent (tan δ) of wood. The loss tangent has a temperature-dependent behaviour, especially in the lignin glass transition region. The glass transition softens wood, and is therefore necessary for gentle mechanical pulping, but at the same time, the loss tangent shows a maximum called the α-peak. The transient peak depends on temperature, loading frequency and moisture content. The temperature where the peak is found can be lowered with chemical treatments, but they also increase the magnitude of the peak. Thermal treatment in the presence of water also increases the magnitude. The loss tangent of wood depends, amongst other things, on the chemical structure of lignin, width of cellulose crystals, microfibril angle, and extractives in the cell wall.

Synthesis, characterisation and application of novel self-assembled comb-like liquid crystalline biphenyl-cellulose as UV absorber for paper

A novel cellulose derivative was designed and synthesised to investigate its liquid crystalline as well as self-assembly properties leading to supramolecular structures. The cellulose derivative was characterised with NMR, TGA, DSC, XRD and polarizing optical microscopy (POM). It was shown that the cellulose derivative behaves as a thermotropic liquid crystal exhibiting strong birefringence even at room temperature. A highly orientated morphology was observed under polarizing optical microscopy showing some novel textures. In the XRD diffractogram, the derivative showed a regular repeating supramolecular layered structure. The compound proved to be a potential UV absorber for paper showing enhanced reflectance in the visible region and absorbance in the UV region.

Sorption properties of torrefied wood and charcoal

Abstract Pre-treating biomass by torrefaction is assumed to improve the materials storage properties because of reducing hydrophilicity. In order to assess the effect of sorption on storage properties, the adsorption of water vapour and capillary absorption of liquid water in torrefied and charred spruce and birch were studied. In addition, the chemical changes were evaluated through Fourier Transform Infrared (FT-IR) spectroscopy. Adsorption decreased notably as severity of treatment increased, as was expected due to degradation of the wood constituents, namely hemicelluloses and amorphous cellulose. Capillary absorption increased with increasing severity in spruce samples while birch showed less change, but the maximum volume for absorption increased with both species. FT-IR results showed an increase in aromatic structures that have a role in forming crystalline structures, possibly leading to increased porosity. Torrefied and charred material should not be stored outside, as liquid water absorbs readily into the material, turning it into a suitable substrate for fungi.

Newtonian boreal forest ecology: The Scots pine ecosystem as an example

Isaac Newtons approach to developing theories in his book Principia Mathematica proceeds in four steps. First, he defines various concepts, second, he formulates axioms utilising the concepts, third, he mathematically analyses the behaviour of the system defined by the concepts and axioms obtaining predictions and fourth, he tests the predictions with measurements. In this study, we formulated our theory of boreal forest ecosystems, called NewtonForest, following the four steps introduced by Newton. The forest ecosystem is a complicated entity and hence we needed altogether 27 concepts to describe the material and energy flows in the metabolism of trees, ground vegetation and microbes in the soil, and to describe the regularities in tree structure. Thirtyfour axioms described the most important features in the behaviour of the forest ecosystem. We utilised numerical simulations in the analysis of the behaviour of the system resulting in clear predictions that could be tested with field data. We collected retrospective time series of diameters and heights for test material from 6 stands in southern Finland and five stands in Estonia. The numerical simulations succeeded to predict the measured diameters and heights, providing clear corroboration with our theory.

Dynamics of Carbon and Nitrogen Fluxes and Pools in Forest Ecosystem

Metabolism of trees, ground vegetation and microbes generate carbon and nitrogen fluxes in forest ecosystems. Carbon flows through the system, and nitrogen circulates between vegetation and soil. Trees synthesise sugars in photosynthesis and take nitrogen from soil. The biochemical regulation system allocates the annual amounts of synthesised sugars and nitrogen taken up to the growth of needles, wood and fine roots. The regularities in tree structure, generated by the action of the biochemical regulation system, determine the allocation to different tree components.

Optimising forest road planning to maximise the mobilisation of wood biomass resources in Northwest Russia

ABSTRACT Forest accessibility is a key factor for the effective mobilisation and utilisation of wood biomass. Therefore, obtaining reliable and precise information is crucial concerning forest resources and the appropriate methods of transportation. The main objective of this study was to improve the methodological approaches to forest road planning to improve the transportation of wood biomass in Russia. The results from the present study into the theoretical optimal road density revealed the importance of economic feasibility and cost-effectiveness when considering expansion of the forest road network. Cost reduction could be achieved through effective operational planning, which should also incorporate the costs for harvesting, road construction and transportation. However, no clear evidence was found regarding the best strategy to apply. The construction of high-quality forest roads should be concentrated in the forests with the largest standing volumes. However, in the near term, extended two-step forest transportation with 6*6WD trucks on the lowest quality roads (e.g. the cheapest basic forest roads) will continue to be an important part of the supply chain; it may even be more cost-efficient to maintain and upgrade these roads to allow all-year-round access with ordinary 6*4WD trucks rather than constructing new roads in these areas. Thus, zoning of the procurement area could be used for optimising forest road planning to maximise the mobilisation of wood biomass.

Structural Regularities in Trees

Several processes, such as photosynthesis and water and nutrient uptake, are simultaneously running in plants. Fluxes of processed products, such as sugars, water and nutrient ions connect the processes with each other. Highly specialised structures have developed in evolution for each process and transport phenomenon. According to the basic idea 7 of the cover theory ( Chap. 2), these structures are effective, and basic idea 9 says that the biochemical regulation systems play an important role in the formation of the structures. The water transport within trees generates regularities in the structure of woody components.

How to Utilise the Knowledge of Causal Responses

Our physical and physiological theory provides causal explanations of various phenomena in forests. This causal nature of the theory enables versatile applications in forestry and in the research of the interactions between climate change and forests. We treat the effects of thinnings and whole-tree harvesting on wood production and the responses of forest ecosystem to nitrogen deposition in more detail. The forests react to the increasing CO2 concentration and also to temperature increase generating feedbacks from forests to climate change. The changes in the carbon storages in forest ecosystems and in the emission of volatile organic compounds are evidently the most important feedbacks from forest ecosystems to the climate change.

Introduction to Physical, Physiological and Causal Forest Ecology

H. T. Odum proposed that energy flows are the key factors in understanding the interactions between ecosystems and their environment. He used electric analogue models and analogue computers in his approach. The development of quantitative methods, measurements, dynamic modelling and digital computing, has opened novel possibilities to analyse the energy and material flows between living organisms and their environment. In addition, the applications of ecological knowledge to the responses of forests to present climate change and forestry should be based on causal effects in trees, atmosphere and soil. The conservation principle of mass and energy, a cornerstone of Newtonian physics, results in dynamic models that can utilise physiological and physical background knowledge to provide causal explanations for the theory and models. The aim of our book is to develop and test a quantitative and causal theory of forest ecology that utilises physics and physiology as background knowledge.

Control of tracheid cross-sectional dimensions in Norway spruce and Scots pine wood raw material

Abstract Wood properties, including tracheid cross-sectional dimensions, show a large degree of variation. To improve the properties of products made from wood, different methods to control variation have been developed. This study aims to determine the theoretical efficiency of three control strategies: the fractionation of pulped tracheids into earlywood and latewood, the separation of juvenile and mature wood, and sorting of logs according to tree size. The efficiency of each method was studied by first constructing virtual trees from measured tracheid cross-sectional dimensions, then simulating the efficiency of above-mentioned methods. The tracheid dimension data include Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.). The simulations show that separation into earlywood and latewood classes has the highest theoretical efficiency and yields the lowest variances in raw material. Classification into juvenile and mature wood groups is the second most efficient method, and the sorting of logs according to the size class of the tree is the least efficient method. It was also concluded that the variation in cell-wall thickness and radial diameter mainly originates from differences between earlywood and latewood, whereas the variation in tangential diameter mainly originates from differences between mature and juvenile wood.