Energieonderzoek

Biomass as a sustainable energy source: environmental load, cost-effectiveness and public acceptance

(2001-2007)

Aanvragers:
prof.dr. C.J.H. Midden, Technische Universiteit Eindhoven
dr. A.L. Meijnders, idem
prof. ir. C. Daey Ouwens, idem
prof.dr.ir. F.J.J.G. Janssen, idem

Overall aim

The aim of the research program was to carry out academic research that contributes to overcoming barriers to the large-scale introduction of biomass as a sustainable energy source. The primary aim was to deliver high-quality research in both the beta (i.e. Chemical Engineering) and gamma (i.e. Technology Management) disciplines, so that both PhD students could obtain a Ph.D. degree in their respective discipline. However, since the problems that arise in a large-scale introduction of biomass partly are technical, partly economical, and partly related to the acceptance of a new energy source and energy technology in society, another objective was to encourage multi-disciplinary cooperation between beta- and gamma-researchers.

The project has been successful in producing meaningful research results and answering the research questions formulated in the research proposal. Two dissertations have been produced and the list of publications in peer reviewed national and international journals will be supplemented with several contributions which are in preparation.

The research has provided important insights in public reactions to specific biomass feeding materials. The research has resulted in a better understanding of the reactions and perceptions of different groups within the general public. For instance, results have highlighted the influence of the proximity to biomass plants on people's perceptions of biomass in general as well as their perceptions of specific types of biomass. Important insights have been gained into the processes underlying the formation of attitudes and by that the acceptance of biomass. Each part of the research conducted within this project has applied relevance as well as significance for the fundamental scientific literature. For instance, our research on contextual influences on attitudes has implications both for the way biomass is positioned on the energy market relative to other energy sources, as well as for fundamental theories on attitude formation.

Dissemination of results

Considerable effort has been invested in presenting the research results on scientific conferences as well as meetings with representatives from industry, policy makers, environmental organisations, and others with a more applied interest . 
Regarding the second objective, we have been invited several times to give a presentation about the interdisciplinary cooperation within our project on beta-gamma meetings organized by NWO/Novem, because this was considered relatively successful.

Project 1: Public acceptance of biomass as a sustainable energy source: consequences for development and implementation

Wouter van den Hoogen, Ph.D. student
Dr. Gundula Hübner, Post doc
Dr. Anneloes Meijnders, Assistant Professor
Prof. dr. Cees Midden, Professor

Lees het artikel van Anneloes Meijnders 'Biomassacentrales vanuit het perspectief van omwonenden', april 2005

Nederlands factsheet

Survey among neighbours

In 2003 a survey has been conducted among neighbours of biomass installations and a start was made with the data analysis. In 2004 the data analysis has been completed and a data report has been written. The results of the neighbours survey have been presented at a number of scientific conferences and a beginning has been made with writing journal articles. We organized a 'klankbordgroep' meeting to present the results of the neighbours survey and to receive feedback on our findings and the results were presented to the biomass communication group (part of action plan biomass). Some highlights of the results are presented below.

The neighbours survey aimed to increase insight in the experiences, perceptions and attitudes of neighbours living in the vicinity of different types of biomass power plants. Specifically, the impact of living distance to the plant on attitudes towards the use of biomass, as well as the structure and strength of these attitudes was examined. Questionnaires were completed by a total of 370 neighbours of 6 plants. Half of the sample lived within 1 km distance of the plants, the other half lived at more than 3 km distance.

The results showed that attitudes towards the use of biomass in the plant generally were moderately positive, with significant attitudinal differences between the neighbours of different plants. Annoyance levels generally were low, though again there were significant differences between the neighbours of different plants. According to the neighbours the use of biomass as an electricity source has both positive and negative consequences. Relatively frequently mentioned types of positive consequences were: environmental benefits, usefulness of recycling waste, waste reduction, financial benefits, saving fossil fuels, and an alternative to grey energy. Relatively frequently mentioned types of negative consequences were: annoyance, emissions, financial disadvantages, environmental disadvantages, and negative consequences for health. The most striking difference between neighbours who lived within 1 km distance and those who lived farther away, was that while they reported equal levels of positive emotions and positive consequences, the neighbours living close-by reported higher levels of negative emotions and negative consequences. As appears from the extensive literature on ambivalence, mixed thoughts and feelings have important consequences for the predictability of behaviour and responses to communication.

Consumer survey

To set up the consumer survey in 2002 a pilot study was conducted. Aim of this pilot study was to analyze laypeople’s mental representation of biomass input materials. Crucial for biomass electricity’s social acceptance is that the public shares and positively evaluates the categories declared by technical and marketing experts. To understand how biomass materials are represented in the peoples’ mind, we confronted 38 laypeople with 28 specific biomass materials. The participant’s were asked to categorize these materials according to similarity. Six dominant input material categories were observed: 1. crops, 2. organic household waste, 3. cadavers and carcass meal, 4. manure, 5. farmed wood, 6. used wood. These materials can be described on two dimensions – the materials position on the life cycle (from fresh to waste) and the floristic order (from plants to wood/trees). Based on the pilot study’s results the questionnaire for the consumer survey was developed.

The consumer survey was conducted in 2003. Participants were 330 electricity consumers from 10 different rural and urban districts. These participants were selected randomly out of a Dutch energy supplier’s customer lists. Professional interviewers contacted the consumers and conducted fully structured interviews. The data analyses were completed in 2003. The results were presented at a number of scientific conferences and have been published in two peer reviewed journals. Further publications are in preparation. These results gave hints that consumers do not distinguish between clean and dry (as wood) or dirty and wet (as waste) materials, but look for practical solutions not necessarily environmentally motivated. For example, using manure as a biomass input materials seems attractive because is saves waste and energy problems simultaneously. Secondly, consumers of grey as well as consumers of green electricity showed little preferences for farmed wood as an energy source. Contrary, using farmed wood as an energy source was evaluated critically and negatively associated with cutting trees. Furthermore, rather frequently wood was rejected as an energy source since it could be used for a better purpose, e.g. producing furniture. Similarly, in people's perception crops represent feeding materials not to be misused as an electricity source. Farmed wood and crops were the least preferred and most frequently rejected biomass input materials. Unexpected, the results revealed organic household waste as the most preferred biomass input material. Opposite, using organic household waste is associated with solving waste problems, and therefore as a positive cascade use of materials. Additionally, consumers had a relative strong preference for manure. This result underlines the positive evaluation of cascade use of waste. However, this positive evaluation of waste is limited: animal remains such as manure, carcass meal and cadavers were evaluated less positively. Overall, animal powder and cadavers belonged to the least preferred input materials. It can be concluded, that the semantic qualification as ‘waste’ is not automatically evaluated negatively but depending on the type of waste positively as cascade use. These results give hints that consumers do not make distinctions between clean and dry (as wood) or dirty and wet (as waste) materials, but look for practical solutions not necessarily environmentally motivated.

The results of the consumer survey suggest recommendations for the design and implementation of biomass electricity. First, under the perspective of social acceptance, technical research on the possibilities of using organic waste streams such as organic household waste should be intensified. Second, in communication strategies instead of focusing on 'clean' materials, cascade use of accepted waste materials could be featured. If farmed wood is used, it might not be enough to stress its natural origin but to prove it stems from a forest managed with good stewardship, e.g. certification by the Forest Steward council. Future development and strategies promoting biomass electricity should take into account consumers' preferences for specific biomass input materials.

Experimental research

Dissertation 'From "bio-what?" to "bio-watt!", contextual influences on the formation of attitudes towards novel energy technologies' by W. van de Hoogen (27 June 2007)
Nederlandse samenvatting lang / Nederlandse samenvatting kort / Nederlands factsheet

The aim of this thesis is to increase our understanding of the processes underlying public acceptance of novel (energy) technologies. Especially when people know little about an issue, which typically is the case with new technologies, subtle differences in the way the issue is introduced may influence their attitudes. In seven experiments (with a total of 855 participants) the boundary conditions for the occurrence of context effects were investigated, as well as the processes underlying these effects. The focal topic was the use of biomass for electricity generation.

The results show that people only are sensitive to context effects when their prior attitudes towards biomass are weak. When attitudes were weak and another energy source was mentioned casually just before people were asked to evaluate biomass, they assimilated their judgment towards this other energy source: They evaluated biomass more positively following solar energy than following coal. Under specific circumstances however, the opposite effect was found. That is, when the contextual object was made distinct by having people evaluate it explicitly before evaluating the target object, contrast occurred. Judgments about biomass then turned out to be more negative when made in the context of solar energy, than when made in the context of coal. Contrast was found to only occur in the case of unlimited cognitive capacity. In addition, contrast appeared to be dimension specific. Assimilation, on the other hand, was found to occur regardless of cognitive capacity and issue involvement.

The results are in line with the theory that assimilation is due to the use of a contextual object as an interpretation frame, to make sense of an unfamiliar target object; contrast on the other hand happens when the contextual object is used as a standard with which the target object is compared. The findings substantiate the notion that contrary to the interpretation process, the comparison process is effortful. The alternative explanation that context effects would be due to a simple correction process is challenged by the results.

People will often form attitudes towards new technologies based on limited information, due to the complexity of the issue, a lack of involvement, or time limitations. The research provides reasons to assume that people’s attitudes towards novel energy sources are related to each other. That is, communication about one energy source can influence the evaluation of another, novel, energy source. For instance the contextual presence of a positively evaluated energy source may result in more positive attitudes towards a novel object. Alternatively, the contextual presence of a positively evaluated energy source may also result in the opposite effect. As a result of comparison with a positively evaluated energy source biomass may be more negatively evaluated. This implies that promotion of one energy source can reduce the acceptance of other (novel) energy sources.

Given that in the Netherlands multiple energy sources are introduced and are communicated about, this research stresses the importance of an integrated communication strategy for the acceptance of all these energy sources. The research sheds more light on the processes underlying attitude formation under these circumstances and on the subtle influences of the contextual embeddedness of technologies.

Project 2: Design of a small-scale biomass gasifier in view of technical, economical and psychological parameters

M.J. Prins, Ph.D. student
Dr.ir. K.J. Ptasinski, Associate Professor
Prof.dr.ir. F.J.J.G. Janssen, Professor

Dissertation 'Towards more efficient biomass gasification - Thermodynamic analysis and integration with torrefaction' by M. Prins (16 Feb 2005)
Nederlandse samenvatting / Nederlands factsheet 

This thesis addresses the question how biomass may be used more efficiently and economically than it is being used today. Biomass already plays a large role in the energy supply, especially in developing countries, but it is often used inefficiently. Rather than combustion of biomass, it could be gasified, and the gas subsequently used in modern energy devices such as gas turbines, fuel cells, and catalytic reactors. Gasification of biomass has been practiced since World War II but technical bottlenecks (e.g. tar formation) and non-technical bottlenecks (e.g. cost and availability of biomass) are still hampering large-scale implementation.

The thesis is presented in two parts. In the first part, the thermodynamic efficiency of gasification processes is analysed. Many possible biofuels are evaluated, such as wood, straw, manure, vegetable oils, etc. These biofuels differ in their suitability for thermal bioenergy processes, and also provoke very different reactions and attitudes, both for the electricity consumers as well as neighbours of bioenergy plants. As a general conclusion, the public seems to prefer the use of waste streams such as organic waste and manure, whereas the engineers in companies active in biomass gasification focus on wood and straw as the technically most favourable biofuels. There exists a field of tension between the public preference and current reality.
Another conclusion from the first part of this thesis is that it may be advantageous to improve the heating value of biomass prior to gasification, which enables higher gasification temperatures and higher thermodynamic gasification efficiency. The second part is thus aimed at improving the properties of biomass prior to gasification using torrefaction, a thermal pretreatment in the range of 230-300°C in the absence of oxygen. In this process, mainly the hemicellulose fraction (which amounts to 20-35 wt% of the wood) decomposes, whereby deciduous wood types, such as beech and willow, were found to be more reactive than coniferous wood types, such as larch, due to different compositions of their hemicellulose fractions. The reaction kinetics of the process and products formed have been studied, as well as possibilities for integrating the torrefaction and gasification processes.
The thesis recommends that the integrated processes of torrefaction and gasification be demonstrated in practice, as this presents a novel method to convert biomass more efficiently to synthesis gas than conventional gasification processes.

Output

Proefschriften

  • Hoogen, van den W. M. (2007) . From "bio-what?" to "bio-watt!": Contextual influences on the formation of attitudes towards novel energy technologies. Technische Universiteit Eindhoven
  • Prins, M. J. (2005) Thermodynamic analysis of biomass gasification and torrefaction. Technische Universiteit Eindhoven.

Publicaties in internationale tijdschriften

  • Hübner, G., & Kaiser, F. G. (2006) . The moderating role of the attitude-subjective norms conflict on the link between moral norms and intention. European Psychologist, 11, 99-109.
  • Hübner, G., Meijnders, A.L., Prins, M.J., Midden, C.J.H. & Pohl, J. (in preparation) . Public perception of biomass input types – biomass in the eyes of consumers and neighbours. Biomass and Bioenergy
  • Hoogen, van den W.M., Meijnders, A.L., & Midden, C.J.H. (in preparation) . Contextual Influences on the Evaluation of New Objects: The roles of Distinctness, Salience, and Cognitive Capacity. Journal of Consumer Psychology.
  • Hoogen, van den W.M., Meijnders, A.L., & Midden, C.J.H. (in preparation) . Comparison or correction? Processes underlying context effect for the evaluation of novel objects. Journal of Applied Social Psychology.
  • Kaiser, F. G., Hübner, G. & Bogner, F. X. (2005) . Contrasting the theory of planned behavior with the value-belief-norm model in explaining conservation behavior. Journal of Applied Social Psychology, 35, 10, 2150-2170.
  • Meijnders, A.L. (in preparation) , It is clean but it stinks. Ambivalent emotional and cognitive responses to a bio-energy installation in the backyard. Journal of Applied Social Psychology.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2003) . Thermodynamics of gas-char reactions: first and second law analysis. Chemical Engineering Science 58:13-16, 1003-1011.
  • Prins, M.J., & Ptasinski, K.J. (2006) . Energy and exergy analyses of oxidation and gasification of carbon. Energy 30:7 (2005), 982-1002 & 31:12, 2245-2246.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2005) . Exergetic optimisation of a production process of Fischer–Tropsch fuels from biomass. Fuel Processing Technology 86:4 375-389.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2006) . Torrefaction of wood: Part 1. Weight loss kinetics. Journal of Analytical and Applied Pyrolysis 77:1, 28-34.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2006) . Torrefaction of wood: Part 2. Analysis of products. Journal of Analytical and Applied Pyrolysis 77:1, 35-40.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2006) . More efficient biomass gasification via torrefaction. Energy 31:15, 3458-3470.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2007) . From coal to biomass gasification: comparison of thermodynamic efficiency. Energy, in press.
  • Ptasinski, K.J., Prins, M.J., & Pierik, A. (2007) Exergetic evaluation of biomass gasification. Energy, in press.

Publicaties in Nederlandse tijdschriften

  • Hoogen, W.M. van den, Meijnders, A.L., & Midden, C.J.H. (2006) . De invloed van onderscheidbaarheid en saillantie van contextuele informatie op richting en sterkte van contexteffecten [The influence of contextual information on the evaluation of biomass: The roles of distinctness and salience]. In R.W. Holland, J. Ouwekerk, C. van Laar, R. Ruiter,  & J. Ham (Eds). Jaarboek Sociale Psychologie (pp. 207-214). Groningen: Aspo Pers.
  • Hoogen, W.M. van den, Meijnders, A.L., & Midden, C.J.H. (2007 in press) . Corrigeren of vergelijken? De processen die ten grondslag liggen aan contextuele invloeden op de beoordeling van nieuwe objecten. [Correction or comparison? The processes underlying contextual influences on judgments of new objects]. In C. van Laar, R. Ruiter, J. Karremans, W. van Rijswijk, & F. van Harreveld (Eds.), Jaarboek Sociale Psychologie 2006 (pp. xx-xx). Groningen: Aspo Pers.
  • Hübner, G., (2004). Het ‘attitude-subjectieve norm conflict’ als moderator van de relatie tussen morele normen en de intentie om elektriciteit uit biomassa te gebruiken [The attitude-norm conflict as moderator of the relation between moral norms and the intention to use electricity from biomass]. In D. Wigboldus, M. Dechesne, E. Gordijn, & E. Kluwer (Eds.), Jaarboek Sociale Psychologie 2003 (pp. 153-164) . Groningen: Aspo Pers.

Publicaties in vaktijdschriften

  • Meijnders, A.L. (2005) . Biomassacentrales vanuit het perspectief van omwonenden [Biomass installations from the perspective of neighbours]. 

Conference proceedings

  • Bergman, P.C.A., Boersma, A.R., Kiel, J.H.A., Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2004) Torrefaction for entrained flow gasification of biomass. In: W.P.M. van Swaaij, T. Fjällström, P. Helm, A. Grassi, editors. Proceedings of 2nd World Biomass Conference, Rome, Italy, May 10-14, 2004. p. 679-682.
  • Hoogen, W.M. van den, & Meijnders, A.L. (2006c) . Impact of distance to power plant on preferences for energy sources. In M. Tolba, S. Soliman, & A. Abdel-Hadi (Eds.), Environment, health and sustainable development. IAPS 19 / Bibliotheca Alexandrina International conference, p. 172. Alexandrina, Egypt, September 13-16.
  • Hoogen, W.M. van den, Meijnders, A.L., & Goorix, L.A.L. (2005, January) . Attitude strength and target specificity as moderators of context effects. Poster presented at 6th Annual Meeting of the Society for Personality and Social Psychology, New Orleans, LA, US. Conference proceedings p.94.
  • Hübner, G., & Meijnders, A.L. (2005) . Biomass as a sustainable energy source-comparing attitudes of the general public and neighbors of biomass plants. Contribution at the 6th Biennial Conference of the Environmental Psychology Division of the German Association , Bochum, Germany, September 19-21. On CD.
  • Huebner, G. and Meijnders, A.L. (2004) . Biomass as a sustainable energy source - Comparing attitudes of the general public and neighbors of biomass plants. In B. Martens & A.G. Keul (Eds.). Evaluation in progress. Strategies for environmental research and implementation. 18th conference of the International Organisation for people-environment studies, pp. 133. Vienna: Vienna University of Technology.
  • Meijnders, A.L. (2005) . Emotional underpinnings of attitudes towards potentially risky technology. Contribution at the 14th General Meeting of the European Association of Experimental Social Psychology. Würzburg, Germany, July 19-23. Proceedings, p. 224.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2002) . Exergy analysis of a production process of Fischer-Tropsch fuels from biomass. In: W. Palz, J. Spitzer, K. Maniatis, K. Kwant, P. Helm, A. Grassi, editors. Proceedings of 12th European Biomass Conference, Amsterdam, Netherlands, June 17-21, 2002. p. 1154-1157.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2002) . Thermodynamics of gas-char reactions: first and second law analysis. In: Proceedings of 17th Int. Symp. on Chemical Reaction Engineering, Hong Kong, China, August 25-28.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2003) . From coal to biomass gasification: comparison of thermodynamic efficiency. In: N. Houbak, B. Elmegaard, B. Qvale, M.J. Moran, editors. Proceedings of 16th Int. Conf. on Efficiency, Costs, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2003), Copenhagen, Denmark, June 30-July 2, 2003. p. 1097-1103.
  • Prins, M.J., Ptasinski, K.J., & Janssen, F.J.J.G. (2004) More efficient biomass gasification via torrefaction. In: R. Rivero, L. Monroy, R. Pulido, G. Tsatsaronis, editors. Proceedings of 17th Int. Conf. on Efficiency, Costs, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2004), Guanajuato, Mexico, July 7-9, 2004. p. 1485-1494.
  • Prins, M.J., Pierik, A., & Ptasinski, K.J. (2005) Exergy efficiency of biomass gasification for various biofuels. 18th Int. Conf. on Efficiency, Costs, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2005), Trondheim, Norway, June 20-23, 2005.

Conference Presentations

  • Hoogen, W.M. van den, Hübner G., Meijnders, A.L., Midden C.J.H. (2002, 17 - 21 June) . Biomass: How people think and feel about it. Poster proceedings of the 12th European Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, Amsterdam.
  • Hoogen, W.M. van den (2004, 22 January). Affect and cognition in attitude formation: Consumers’ view on biomass. Poster presented at the 1st JFS symposium at Eindhoven University of Technology.
  • Hoogen, W.M. van den (2004, 4 november). From bio-what to bio-watt. Presentation at the 2nd JFS symposium at Eindhoven University of Technology.
  • Hoogen, W.M. van den, Meijnders, A.L., & Midden, C.J.H. (2005, 11 March) . Attitudes towards biomass: How emotions and context influence the evaluation of a new energy source. Poster presented at the Biomass symposium at Eindhoven University of Technology. Hoogen, W.M. van den, Meijnders, A.L., & Midden, C.J.H. (2005, 8 - 9 December) . De invloed van contextuele informatie op de beoordeling van biomassa: De rol van onderscheidbaarheid en saillantie [The influence of contextual information on the evaluation of biomass: The roles of distinctness and salience]. Paper presented at the 20 th ASPO conference, Groningen.
  • Hoogen, W.M. van den, Meijnders, A.L., & Midden, C.J.H. (2006 16 – 21 July) . Context effects on public attitudes towards new energy sources, Paper presented at the 26th International Congress of Applied Psychology, Athens, Greece.
  • Hoogen, W.M. van den, Meijnders, A.L. (2006 11 – 16 September) . Impact of distance to power plant on preferences for energy sources, Paper presented at the 19th conference of the International Association of People environment Studies, Alexandria, Egypt.
  • Hoogen, W.M. van den, Meijnders, A.L., & Midden, C.J.H. (2006, 14 - 15 December) . Corrigeren of vergelijken? De processen die ten grondslag liggen aan contextuele invloeden op de beoordeling van nieuwe objecten. [Correction or comparison? The processes underlying contextual influences on judgments of new objects]. Paper presented at the 21 th ASPO conference, Leiden.
  • Hübner, G. (2004) . Moral norms’ differential impact on behavioral intention. International workshop on environmental and social psychology, 24.01.2004, Nagoya, Japan.
  • Hübner, G. (2003, 11 – 12 December) . Wanneer het geweten gehoord wordt [When conscience is being heard]. Paper presented at the 18th ASPO congres, Maastricht.
  • Hübner, G. (2003, August 31- September 3) . The moderating Role of the ‘Attitudinal Dilemma’on the Link between Moral Norms and Intention to use Biomass Electricity. Paper presentation 5th Biennial Conference on Environmental Psychology. Eindhoven.
  • Kaiser, F.G., Hübner, G. & Bogner, F.X. (2003, August 31- September 3) . Contrasting the Theory of Planned Behavior with the Value-Belief-Norm Model in Explaining Conservation Behavior. Paper presentation 5th Biennial Conference on Environmental Psychology. Eindhoven.
  • Meijnders, A.L. (workshop organiser) (2002, 11 December) . Societal implementation of biomass as an energy source. Workshop at the PhD biomass symposium. With contributions by Hübner, G., Meijnders, A.L., Montijn, F.N.H., & Verbong, G.P.J. Eindhoven.
  • Meijnders A.L., & Prins, M.J. (2003, 27 March) . Implementation barriers of energy from biomass: technical and psychological factors. Paper presentation NWO-Novem conference ‘Met kennis op weg naar een duurzame energiehuishouding - Uitwisseling van kennis en ervaring', Utrecht.
  • Meijnders A.L., Roelofs K. (2002, 25 – 29 June) . How to appraise the risks of a power plant: Trusting others or using your own senses. Paper presentation 13th General Meeting of the EAESP, San Sebastian.

Students reports as part of the research programme

  • van Eijk, R. L. J., Gal, R., Geerts, J., & Goorix, L. A. L. (2003) . Beoordeling van energie: Het verband tussen waardeprioriteiten en de beoordeling van groene en grijze energie [Evaluation of energy: The relation between valuepriorities and evaluation of green and gray energy sources] (Rep. No. Student project). Eindhoven: Eindhoven University of Technology, Human Technology Interaction.
  • Goorix L.A.L. (2003) . Contexteffecten bij de beoordeling van biomassa: De modererende rol van attitudesterkte bij assimilatie en contrasteffecten. [Context effects on evaluations of biomass. The moderating role of attitude strength in assimilation and contrast effects]. Masters thesis. Technische Universiteit Eindhoven, Mens-Techniek Interactie.
  • Heijden, P.T.H. van den (2004). Communication on bio-energy : a study on involvement as moderator of the effect of message sidedness on attitude. Masters thesis. Technische Universiteit Eindhoven, Mens-Techniek Interactie.
  • Janse, I. (2006) . Het effect van "hokjesdenken". Een onderzoek naar de modererende van categorisatie bij de beoordeling van biomassa [The effects of narrow mindedness. Research on the moderating role of categorization for the evaluation of biomass]. Masters thesis. Technische Universiteit Eindhoven, Mens Techniek Interactie.