Dialog-baseret undervisning i forelæsninger om træ som materiale

My project concerns the development of dialogue-based teaching withinwood materials science for civil engineers. Teaching was done over two course dates at the Technical University of Denmark in Spring 2018 where about 50 students attended each time. Teaching was organised with two hours of lectures in a lecture hall followed by two hours of supervised classroom exercises (calculation assignments). The aim of my project was to improve the learning outcome of students by having teaching revolving around discussions rather than a monologue lecturing. This was particularly challenging as my contribution to the course involved only a small fraction of the teaching and the students were used to traditional lecturing with very little student involvement in the teaching. Thus, a specific aim at the beginning of my first teaching date was to re-negotiate the didactical contract between me and the students by signalling that I expected them to be active and participate in the discussions. While the location and the curriculum for my teaching wereset, I was free to choose how I taught the curriculum. Therefore, I organised my teaching into a string of didactic loops according to the framework of the Theory of Didactic Situations. In each loop, the students were presented a minimal amount of information before they were given a question and time to reflect and discuss with their neighbour. Evaluation of the teaching method was done by the studentsreplying anonymously to an online questionnaire with three questions: 1) Rate the connection between lectures and classroom exercises? (Score 1 to 7), 2) Did discussing with your neighbour aid your understanding of the topic? (Score from 1 to 7), 3) Any further comments? (Written answers, multiple answers possible). The students were generally satisfied with the dialogue-based teaching and they found the teaching useful for classroom exercises based on the ratings of questions 1 and2. However, the third question was the most useful for me in improving my teaching in the future. From my own experience in the lecture hall as well as the students’ input it was clear that the re-negotiation of the didactical contract was not fully successful. As a result I will try to improve my future teaching by being more explicit in informing the students what is going to happen in the next session and why

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

The first drying of wood cell walls from the native state has sometimes been described as producing irreversible structural changes which reduce the accessibility to water, a phenomenon often referred to as hornification. This study demonstrates that while changes do seem to take place, these are more complex than what has hitherto been described. The accessibility of wood cell wall hydroxyls to deuteration in the form of liquid water was not found to be affected by drying, since vacuum impregnation with liquid water restores the native cell wall accessibility. Contrary to this, hydroxyl accessibility to deuteration by water vapour was found to decrease to different levels depending on the drying conditions. Vacuum drying at 60 °C for 3 days reduced the accessibility more than drying for 1 day at 103 °C without vacuum. Drying for 3 days at 103 °C increased the hydroxyl accessibility compared to 1 day. Moreover, the decrease in hydroxyl accessibility to deuteration by water vapour induced by the first drying could be at least partially erased by subsequent vacuum impregnation with liquid water, indicating reversibility. For the drying of solid, non-degraded wood cell walls the results challenge the often supposed process of hornification, understood as a permanent decrease in hydroxyl accessibility to water.ISSN:1572-882XISSN:0969-023

The Mechanisms of Plant Cell Wall Deconstruction during Enzymatic Hydrolysis

Mechanical agitation during enzymatic hydrolysis of insoluble plant biomass at high dry matter contents is indispensable for the initial liquefaction step in biorefining. It is known that particle size reduction is an important part of liquefaction, but the mechanisms involved are poorly understood. Here we put forward a simple model based on mechanical principles capable of capturing the result of the interaction between mechanical forces and cell wall weakening via hydrolysis of glucosidic bonds. This study illustrates that basic material science insights are relevant also within biochemistry, particularly when it comes to up-scaling of processes based on insoluble feed stocks

Negative emission potentials using biogenic building materials:a case study from Denmark

Significant reductions in carbon footprint can be achieved by increasing the use of biogenic materials in construction. In biogenic materials, carbon is embedded as long as the materials are not biologically degraded, and they consequently act as carbon reservoirs that keep CO2 out of the atmosphere. The reservoirs of carbon are maintained if the biogenic materials during maintenance and renovation are replaced by similar ones. Buildings containing more wood, straw, and other biogenic materials and less concrete, steel, and mineral wool are therefore part of the way forward for a sustainable restructuring of the construction industry. Until now, the main focus has been on reducing energy consumption of buildings, while less focus has been on energy consumption and the climate impact from the production of materials and the construction process itself. This paper examines the potential carbon reservoir in the building stock in Denmark for the next 100 years. In detail the paper describes potential building components made from biogenic resources, outlines the necessary amounts and qualities of biogenic materials, and summarizes the available biogenic resources. The article is based on the conditions for construction in Denmark and the opportunities Denmark has as an industrialized agricultural country with a long coastline, which can be utilized in the production of biogenic resources for manufacturing of building materials.Significant reductions in carbon footprint can be achieved by increasing the use of biogenic materials in construction. In biogenic materials, carbon is embedded as long as the materials are not biologically degraded, and they consequently act as carbon reservoirs that keep CO2 out of the atmosphere. The reservoirs of carbon are maintained if the biogenic materials during maintenance and renovation are replaced by similar ones. Buildings containing more wood, straw, and other biogenic materials and less concrete, steel, and mineral wool are therefore part of the way forward for a sustainable restructuring of the construction industry. Until now, the main focus has been on reducing energy consumption of buildings, while less focus has been on energy consumption and the climate impact from the production of materials and the construction process itself. This paper examines the potential carbon reservoir in the building stock in Denmark for the next 100 years. In detail the paper describes potential building components made from biogenic resources, outlines the necessary amounts and qualities of biogenic materials, and summarizes the available biogenic resources. The article is based on the conditions for construction in Denmark and the opportunities Denmark has as an industrialized agricultural country with a long coastline, which can be utilized in the production of biogenic resources for manufacturing of building materials