Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Harvesting and cell disruption of microalgae
Lam, Gerard Pieter 't - \ 2017
University. Promotor(en): Rene Wijffels; Michel Eppink, co-promotor(en): Marian Vermue. - Wageningen : Wageningen University - ISBN 9789463431736 - 206
algae - harvesting - flocculation - polymers - chlorella vulgaris - biorefinery - electric field - organelles - algen - oogsten - uitvlokking - polymeren - bioraffinage - elektrisch veld - organellen

Microalgae are a potential feedstock for various products. At the moment, they are already used as feedstock for high-valuable products (e.g. aquaculture and pigments).

Microalgae pre-dominantly consist out of proteins, lipids and carbohydrates. This makes algae an interesting feedstock for various bulk-commodities. To successfully produce bulk-commodities, a multi-product biorefinery should be adopted that aims on production of both bulk- and high value co-products. In the downstream process, however, harvesting- and cell disruption are technological hurdles for cost effective multi-product biorefinery.

Flocculation is considered as a low-cost harvesting process. Flocculating microalgae at high salinities used to be not feasible We demonstrated that marine microalgae can successfully be flocculated and harvested by using cationic polymers.

In the second part of this thesis we studied Pulsed Electric Field (PEF) as potential cheap and non-disruptive technology to open microalgae. PEF-treatment evokes openings/’holes’ in micro-organisms. PEF in combination with a pre-treatment to weaken the cell wall resulted in release of proteins from microalgae at low energy consumption.

Recent advances in technology development learned that harvesting of micro-algae is no longer a bottleneck. Future research and development should focus on cell disruption and mild extraction technologies. Costs for the biorefinery will decrease by process simplification. For that unit operations for cell disruption and extraction need to be integrated.

This project was part of a large public private partnership program AlgaePARC biorefinery ( Objective of this program is to develop a more sustainable and economically feasible microalgae production process. For that all biomass components (e.g. proteins, lipids, carbohydrates) should be used at minimal energy requirements and minimal costs while keeping the functionality of the different biomass components. Biorefining of microalgae is very important for the selective separation and use of the different functional biomass components.

Robotic harvesting of fruit vegetables
Bontsema, Jan - \ 2015
horticulture - greenhouse horticulture - cucumis - sweet peppers - fruit vegetables - robots - harvesting - sensors
Witte asperges worden niet meer groen
Marcelis, L.F.M. - \ 2015
Bionieuws 25 (2015)8. - ISSN 0924-7734 - p. 10 - 10.
vollegrondsteelt - asparagus - kleuring - oogsten - lesmaterialen - outdoor cropping - staining - harvesting - teaching materials
Witte asperges moeten wit zijn, en niet lichtpaars of zelfs groen. Telers, winkeliers en ook hobbytuiniers doen daarvoor alle moeite. Zo ook microbioloog Rob de Jonge. Omdat hij de lerarenopleiding volgt geeft hij les in Waddinxveen, en behandelt daar met de eerste klas planten. Ook heeft hij een volkstuin, compleet met aspergebed. ‘Tel alles bij elkaar op, en je komt op mijn vraag.’ Vraag: Waardoor blijven asperges gewoon wit na het steken?
CROPS : Clever Robots for CROPS
Bontsema, Jan - \ 2015
agriculture - forestry - harvesting - robots - automation - automatic control - instrumentation - spraying - engineering
Improving obstacle awareness for robotic harvesting of sweet-pepper
Bac, C.W. - \ 2015
University. Promotor(en): Eldert van Henten, co-promotor(en): Jochen Hemming. - Wageningen : Wageningen University - ISBN 9789462571808 - 186
robots - oogsten - paprika's - obstructie - detectie - spectraalanalyse - beeldverwerking - simulatie - kassen - harvesting - sweet peppers - obstruction - detection - spectral analysis - image processing - simulation - greenhouses


Obstacles are densely spaced in a sweet-pepper crop and they limit the free workspace for a robot that can detach the fruit from the plant. Previous harvesting robots mostly attempted to detach a fruit without using any information of obstacles, thereby reducing the harvest success and damaging the fruit and plant. The hypothesis evaluated in this research is that a robot capable of distinguishing between hard and soft obstacles, and capable of employing this knowledge, improves harvest success and decreases plant damages during harvesting. In line with this hypothesis, the main objective was to develop a sweet-pepper harvesting robot capable of distinguishing between hard and soft obstacles, and of employing this knowledge.

As a start, the thesis describes the crop environment of a harvesting robot, reviews all harvesting robots developed for high-value crops, and defines challenges for future development. Based on insights from this review, we explored the ability to distinguish five plant parts. A multi-spectral imaging set-up and artificial lighting were developed and pixels were classified using a decision tree classifier and a feature selection algorithm. Classification performance was found insufficient and therefore post-processing methods were employed to enhance performance and detect plant parts on a blob basis. Still, performance was found insufficient and a focussed study was conducted on stem localization. The imaging set-up and algorithm developed for stem localization were used to provide real stem locations for motion planning simulations. To address the motion planning problem, we developed a new method of selecting the grasp pose of the end-effector. The new method and the stem localization algorithm were both integrated in the harvesting robot, and we tested their contribution to performance. This research is the first to report a performance evaluation of a sweet-pepper harvesting robot tested under greenhouse conditions. The robot was able to harvest sweet-peppers in a commercial greenhouse, but at limited success rates: harvest success was 6% when the Fin Ray end-effector was mounted, and 2% when the Lip-type end-effector was mounted. After simplifying the crop, by removal of fruit clusters and occluding leaves, harvest success was 26% (Fin Ray) and 33% (Lip-Type). Hence, these properties of the crop partly caused the low performance. The cycle time per fruit was commonly 94 s, i.e. a factor of 16 too long compared with an economically feasible time of 6 s. Several recommendations were made to bridge the gap in performance. Additionally, the robot’s novel functionality of stem-dependant determination of the grasp pose was evaluated to respond to the hypothesis.

Testing the effect of enabling stem-dependent determination of the grasp pose revealed that, in a simplified crop, grasp success increased from 41% to 61% for the Lip-type end-effector, and stem damage decreased from 19% to 13% for the Fin Ray end-effector. Although these effects seem large, they were not statistically significant and therefore resulted in rejection of the hypothesis. To re-evaluate significance of the effects, more samples should be tested in future work.

In conclusion, this PhD research improves the obstacle awareness for robotic harvesting of sweet-pepper by the robot’s capability of perceiving and employing hard obstacles (plant stems), whereas previous harvesting robots either lumped all obstacles in one obstacle class, or did not perceive obstacles. This capability may serve as useful generic functionality for future robots.

Oogsten : Verwerken van niet houtige biomassa
Holshof, G. ; Schooten, H.A. van; Schoot, J.R. van der; Durksz, D.L. - \ 2014
Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 774b)
grasmaaisel - behandeling na de oogst - ingekuilde planten - oogsten - benodigde machines - oogstmachines - biomassa productie - biobased economy - opslag - grass clippings - postharvest treatment - silage plants - harvesting - machinery requirements - harvesters - biomass production - storage
In deze brochure wordt praktisch beschreven waar bij het oogsten van gras op moet worden gelet. Deze brochure is onderdeel van een aantal brochures met informatie hoe om te gaan met het oogsten en verwerken van niet houtige biomassa, die niet wordt gebruikt als veevoer.
Schone teelt is een absolute voorwaarde om producten af te kunnen blijven zetten : Aardappel Demodag PPO Westmaas
PPO Akkerbouw, Groene Ruimte en Vollegrondsgroente, - \ 2014
Aardappelwereld 68 (2014)8. - ISSN 0169-653X - p. 12 - 13.
aardappelen - akkerbouw - mechanisatie - oogsten - kwaliteit na de oogst - demonstraties (vertoning) - potatoes - arable farming - mechanization - harvesting - postharvest quality - demonstrations
Het thema van de Aardappeldomodag in augustus 2014 zal zijn 'Schone teelt bepaalt de toekomst'
Cucumber harvesting robot
Wageningen UR Glastuinbouw, - \ 2013
Wageningen : Wageningen UR Glastuinbouw
glastuinbouw - komkommers - oogsten - robots - automatisering - rijpheid - innovaties - greenhouse horticulture - cucumbers - harvesting - automation - maturity - innovations
Today, labour is the largest cost factor of a modern greenhouse holding. More than 30% of the total production costs are spent on wages for the grower and his employees. Obviously, to cope with saturating market demands and increasing competition, the grower is looking for ways to improve the over-all efficiency of the production process. Manual labour in a greenhouse is demanding, especially under poor climatic conditions. Because the robots reported in literature were not suited for the high productivity growing systems used in Dutch horticultural practice, in 1996, Wageningen UR Greenhouse Horticulture began research on the development of an autonomous cucumber harvesting robot supported by the Dutch Ministry of Agriculture, Food and Fisheries. The task of designing robots for agricultural applications raises issues not encountered in other industries. The robot has to operate in a highly unstructured environment in which no two scenes are the same. Both crop and fruit are prone to mechanical damage and should be handled with care. The robot has to operate under adverse climatic conditions, such as high relative humidity and temperature as well as changing light conditions. The robot detects individual cucumbers, assesses theri ripeness and harvest the ripe cucumbers. During greenhouse experiments 95% of the ripe cucumbers were detected and 75% were harvested. The project was finished in 2002.
Oogsten van micro-algen : inventarisatie oogstmethoden en praktijkresultaten
Schoot, J.R. van der; Schipperus, R. ; Kootstra, A.M.J. - \ 2013
Lelystad : PPO AGV (PPO rapport 566) - 17
algenteelt - oogsten - technieken - scheidingstechnologie - technologie - biomassa productie - biobased economy - algae culture - harvesting - techniques - separation technology - technology - biomass production
In dit rapport worden de resultaten beschreven van een inventarisatie van verschillende methoden voor het oogsten van micro-algen. Veel van de besproken methoden zijn erop gericht om op een goedkope en min of meer passieve manier een voorconcentratie van de algensuspensie te bewerkstelligen, om zo uiteindelijk door een kleiner te verwerken volume te besparen op de actieve concentratiestap, bijvoorbeeld de centrifuge. Bij de inventarisatie is gebruik gemaakt van wetenschappelijke literatuur en ook van een aantal beschikbare rapporten van praktijkopstellingen.
Reed harvesting from wetlands for bioenergy : technical aspects, sustainability and economic viability of reed harvesting in Ukraine
Sluis, T. van der; Poppens, R.P. ; Kraisvitnii, P. ; Rii, O. ; Lesschen, J.P. ; Galytska, M. ; Elbersen, H.W. - \ 2013
Wageningen : Alterra, Wageningen-UR (Alterra report 2460) - 88
phragmites - oogsten - brandstofgewassen - wetlands - certificering - biomassa productie - indirecte veranderingen van landgebruik - oekraïne - biobased economy - harvesting - fuel crops - certification - biomass production - indirect land use change - ukraine
In this report the different aspects of reed and reed lands are discussed related to sustainable harvesting of biomass. This is based on a pilot project for Poltava Oblast, funded by Agency NL of the Dutch Ministry of Economic Affairs. Within the ‘Pellets for Power project’ several areas were identified, to test the approach and criteria applied for NTA8080. This report shows that ILUC free reed harvesting is possible. Reed in the project area is harvested on land not used currently for agricultural purposes. The wetland should be maintained as much as possible in its natural state, and protected against fires. Based on this, it is concluded that the requirements for NTA8080 can be met. Biomass harvesting is in support of wetland protection, and can result in increased biodiversity, provided that the necessary precautions are taken, as described in the ‘best practices’. In this way reed harvesting for biofuels also contribute to social wellbeing, increase income for local communities, and at the same time decrease greenhouse gas emissions.
Algenoogst 100 keer energiezuiniger
Salim, Sina - \ 2013
algae - algae culture - harvesting - flocculation - energy saving - biobased economy
Harvesting microalgae by bio-flocculation and autoflocculation
Salim, S. - \ 2013
University. Promotor(en): Rene Wijffels, co-promotor(en): Marian Vermue. - S.l. : s.n. - ISBN 9789461736710 - 152
algen - oogsten - uitvlokking - bioproceskunde - biodiesel - biomassa productie - biobased economy - algenteelt - algae - harvesting - flocculation - bioprocess engineering - biomass production - algae culture
Harvesting in commercial microalgae production plants is generally done by centrifugation, but this requires upto about 50% of the total energy gained from the microalgae. The energy needed for harvesting can be reduced considerably by pre-concentration of the microalgae prior to further dewatering. The focus of this thesis was on development of a controlled pre-concentration step in which bio-flocculation and autoflocculation using oleaginous microalgae is applied combined with gravity sedimentation. This technology was evaluated in terms of energy demand for harvesting microalgae.
Worm blij met natte zomer : Interview met Klaas van Rozen en Mirjam Pulleman
Berg, G.A. van den; Rozen, K. van; Pulleman, M.M. - \ 2012
Boerderij 97 (2012)49. - ISSN 0006-5617 - p. 40 - 43.
aardappelen - oogsten - akkerbouw - aporrectodea caliginosa - aardwormen - potatoes - harvesting - arable farming - earthworms
Het begin van zomer 2012 was nat. Half augustus zitten de wormen boven in de aardappelrug. Als de nazomer droog verloopt, is de kans op rooiproblemen groot.
Veilig landen en stijgen op Schiphol; Vergoedingsregeling graanteelt om ganzen te weren
Rijk, P.J. - \ 2012
Den Haag : LEI, onderdeel van Wageningen UR (LEI-rapport : Onderzoeksveld Regionale Economie & Ruimtegebruik ) - ISBN 9789086155903 - 49
regionale economie - ganzen - graangewassen - oogsten - vergoeding - vogelbestrijding - regional economics - geese - grain crops - harvesting - compensation - bird control
In dit rapport zijn aanbevelingen gedaan voor een toekomstige vergoedingsregeling voor het versneld onderwerken van de graanresten (stoppels en gevallen graankorrels) na de graanoogst in de nabijheid van Schiphol (Haarlemmermeerpolder). Als de regeling wordt uitgevoerd zal deze in de weken na de graanoogst de veiligheid van het vliegverkeer naar en van Schiphol bevorderen. In dit rapport zijn twee vergoedingsregelingen doorberedeneerd en berekend. Bij beide regelingen wordt het stro gehakseld en samen met de graanstoppel ondergewerkt. In de ene regeling wordt het land geploegd en bij de andere regeling wordt een groenbemester ingezaaid. De voorgestelde vergoeding voor beide regelingen ontlopen elkaar niet veel: circa 700 euro per ha. Daarboven op kan voor aanvullende zaken (administratie, monitoren ganzen, overleg) en om het geheel bedrijfseconomisch aantrekkelijker te maken een opslag komen. Voorgesteld wordt om uiteindelijk één regeling aan de graantelers voor te leggen en het verder aan hen over te laten wat men kiest. Als de graanoogstresten (stro en resterende korrels) maar ondergewerkt zijn binnen twee dagen na de oogst.
On seed physiology, biomechanics and plant phenology in Eragrostis tef
Delden, S.H. van - \ 2011
University. Promotor(en): Paul Struik; Tjeerd-Jan Stomph, co-promotor(en): Jan Vos. - S.l. : s.n. - ISBN 9789085859444 - 185
eragrostis - eragrostis tef - teelt - plantenfysiologie - biomechanica - zaadkieming - legering - oogsten - cultivation - plant physiology - biomechanics - seed germination - lodging - harvesting

• Key words: Teff (Eragrostis tef (Zuccagni) Trotter), germination, temperature, model, leaf appearance, phyllochron, development rate, lodging, biomechanics, safety factor, flowering, heading, day length, photoperiod.

• Background Teff (Eragrostis tef (Zuccagni) Trotter) is a C4 annual grass species (Poaceae) originating from Ethiopia. Teff cultivation in the Netherlands is thought to be economically feasible because teff grains and flour do not contain gluten and are rich in iron. These two characteristics make teff a desirable ingredient in health products, particularly for celiac disease patients. At the start of this project Dutch teff yields were modest (1.0 - 1.5 Mg•ha-1). The sowing and harvest dates were (too) late in the season and the crop was sensitive to lodging. Here, lodging is defined as the permanent displacement of shoots from their vertical due to root or shoot failure.

• The objective of this research is to detail some processes that underlie the sensitivity to lodging and the late harvest. Therefore we studied seed germination, lodging resistance, day length response, pace of leaf appearance.

• Germination of teff can be described by assuming a normally distributed rate of germination within the seed population. Minimal and maximal temperatures required for germination depend on water availability (water potential). Conversely, the minimal required water potential for germination depends on temperature.

• Lodging was inevitable for teff grown on a Dutch sandy soil. We identified that not only the shoots of teff are prone to lodging, but that the roots are also a major factor in the lodging process. Furthermore, water adhering to the shoots alone, without wind action, could induce lodging in the studied cultivars.

• Flowering in teff is significantly delayed by exposure to long days. Teff is therefore a short day plant; not only panicle initiation, but also development and outgrowth of the panicle were influenced by photoperiod.

• Phyllochron, defined as the time required between the appearance of two successive teff leaves, increased abruptly for the last few leaves on the main stem of teff. After re-evaluation of literature data this abrupt increase in phyllochron seemed to be also present in both wheat and rice. The delay is most likely independent of temperature, but might be related to the moment of panicle initiation.

• In conclusion, the study on teff identified clear targets for breeding towards a high-yielding cultivar in the Netherlands.

Zoektocht naar oorzaak wisselende productie Kordia : een mooie kers, maar....
Vlas, M.J. de - \ 2011
De Fruitteelt 101 (2011)14. - ISSN 0016-2302 - p. 16 - 17.
fruitteelt - kersen - steenvruchten - rassen (planten) - cultivars - oogsten - rendement - oogstfactoren - plantenontwikkeling - gewaskwaliteit - fruit growing - cherries - stone fruits - varieties - harvesting - returns - yield factors - plant development - crop quality
Grote, donkerrode, sappige kers met een prima smaak die goed bewaarbaar is. Dat is Kordia, het ras zoete kers dat op de veiling mooie prijzen kan opbrengen. Vrijwel elke kersenteler in Nederland teelt Kordia. Tegenover alle voordelen van het ras staat echter een groot nadeel: de productie kan van jaar tot jaar wisselen. Onderzoek bracht nog geen volledige helderheid hierin. Waarschijnlijk is de wisselende productie te wijten aan een combinatie van factoren.
Concept studie autonoom oogsten van appels en peren
Pekkeriet, E.J. ; Heijerman, G. ; Otten, G.W. ; Tuijl, B.A.J. van; Wigham, M.L.I. ; Jalink, H. - \ 2010
Wageningen : Wageningen UR Glastuinbouw (Rapporten GTB-1012) - 70
oogsten - appels - peren - mechanisch oogsten - robots - arbeid (werk) - haalbaarheidsstudies - proefprojecten - sensors - harvesting - apples - pears - mechanical harvesting - labour - feasibility studies - pilot projects
Bij de oogst van appels en peren is in een korte periode veel arbeid nodig. Het vraagt een forse inspanning om voldoende kwalitatief juiste arbeid te krijgen op het juiste moment tegen de juiste prijs, de kosten voor arbeid zijn hoog. Voor NFO en het PT hebben initiatief genomen om te komen tot robotisering van deze handeling te automatiseren. Doelstelling van dit project is één of meerdere concepten te ontwerpen voor het automatisch oogsten van appels en peren, waarbij kritische deelfuncties op eerste haalbaarheid zijn getoetst om de drempel te verlagen om een vervolg te starten. Aansluitend is het doel ontwikkelingstraject te starten dat binnen een afzienbare periode zal leiden tot implementatie. In het rapport zijn enkele perspectiefvolle concepten uitgewerkt. Verschillende deelfuncties zijn ontworpen en getest op haalbaarheid zoals: het sensorconcept globaal (waar zitten de appels); het sensorconcept lokaal (Is de appel voldoende rijp); manipulatie en end-effector en logistiek en buffering. Voor de verschillende functies zijn goede oplossingen voorhanden. De studie betreft met name een papieren studie. In een vervolg zal moeten blijken of het ook daadwerkelijk technisch haalbaar is. De focus in een vervolg dient te liggen bij de plukhandeling zelf en de daarbij horende sensoriek (de ogen, de arm en het handje). Het afvoeren van de geoogste appels, het bufferen en het transport door de boomgaard lijkt niet het probleem te zijn. Aan het einde heeft een herijking van de businesscase plaatsgevonden. De NFO/PT acht het project voldoende perspectiefvol om te starten met een initiatief voor verdere implementatie als vervolg op de conceptontwikkeling.
Verkorting van de oogstduur bij tulpen
Dam, Martin van - \ 2010
tulips - harvesting - bulbs - timing - organization of work - effects - crop quality
Meer winst uit gewas in biobased economy (interview met J.P.M. Sanders)
Ypma, T. ; Sanders, J.P.M. - \ 2010
Boerderij 95 (2010)41. - ISSN 0006-5617 - p. 18 - 19.
gewassen - oogsten - opbrengsten - recycling - biobased economy - crops - harvesting - yields
Landbouwgewassen bevatten veel verschillende bruikbare onderdelen. Kunst is om de oogst zo te demonteren dat die stoffen maximaal benut worden.
Towards high productivities of microalgae in photobioreactors
Bosma, R. - \ 2010
University. Promotor(en): Rene Wijffels; Hans Tramper, co-promotor(en): Marian Vermue. - [S.l. : S.n. - ISBN 9789085855590 - 133
bioreactoren - algen - fotosynthese - licht - lichtregiem - oogsten - screenen - stammen (biologisch) - ultrageluid - onderwijs - lesmaterialen - fotobioreactoren - bioreactors - algae - photosynthesis - light - light regime - harvesting - screening - strains - ultrasound - education - teaching materials - photobioreactors
The biodiversity of microalgae is enormous and they represent an almost untapped source of unique algae products. Presently, there is a niche market for high-value algal products (e.g. carotenoids and fatty acids). To make commercial production of low-value bulk products possible, still many bottlenecks should be solved. This thesis addresses several of these bottlenecks.
Based on research on the light conversion by the microalgae, a model was developed that predicts the minimal and maximal productivity of the microalgae in a photobioreactor. In addition, a screening method was developed for fast determination of the growth rate of microalgae. This method can be used to optimize the growth medium as well as to optimize cultivation conditions. We used this method to determine the growth inhibiting effects of free fatty acids on a microalga. In addition, the application of ultrasound as harvesting process for microalgae was investigated. It was found that ultrasound could indeed be used to harvest microalgae, but that this process was commercially only feasible for special applications on small scale. Because algal technology is a relatively new research field, learning materials should be developed for appropriate education in this field. This thesis describes the development of a practical in which third year BSc students learn how to cultivate microalgae and to develop a production strategy to achieve as much ß-carotene production as possible using these algae. Finally, the research described above is evaluated and further research strategies are identified to push microalgal technology ahead and to achieve higher productivity of microalgae in photobioreactors in the future.

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