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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Exploratory study into possible applications of Asian knotweed
    Dijk, C.J. van; Meer, I.M. van de; Vos, R.C.H. de; Werf, A.K. van der - \ 2020
    Wageningen : Stichting Wageningen Research, Wageningen Plant Research (Report / Stichting Wageningen Research, Wageningen Plant Researchs WPR-1004) - 41
    Verkennende studie toepassingsmogelijkheden Aziatische duizendknoop
    Dijk, C.J. van; Meer, I.M. van de; Vos, R.C.H. de; Werf, A.K. van der - \ 2020
    Wageningen : Stichting Wageningen Research, Wageningen Plant Research (Rapport / Stichting Wageningen Research, Wageningen Plant Research WPR-1003) - 49
    Development of offshore seaweed farming: ecology & cultivation : Synthesis report 2019
    Bernard, M.S. ; Jansen, H. ; Werf, A. van der; Meer, I. van der; Tonk, Linda - \ 2020
    Yerseke : Wageningen Marine Research (Wageningen Marine Research report C054/20) - 31
    The upscaling of offshore wind farms in the North Sea creates opportunities for seaweed aquaculture that has the potential to meet part of future resource needs, provided that it is done sustainably. Here a follow-up study of the MIP project in 2018 “Development of Offshore Seaweed Cultivation: food safety, cultivation, ecology and economy” with a focus on ecology and cultivation is presented. In order to ensure a sustainable development of seaweed farming in Dutch offshore and coastal regions in the future, it is essential to collect empirical data on the interaction of seaweed cultivation with marine ecosystems for realistic impact assessments. In subproject 1 “Ecology – Fauna associated with seaweed aquaculture in the North Sea Farm” ecosystem services and impacts of seaweed farming in the North Sea were investigated on the basis of biodiversity, a key parameter for the functioning of ecosystems. Therefore in 2019 the associated fauna on growing seaweed biomass (Saccharina latissima) and cultivation ropes was assessed at the North Sea Farm. A high number of individuals was detected on the seaweeds and cultivation ropes in general (up to 7679 individuals per rope), but species richness was low. Abundance in fauna increased from May to June and all detected species are also known from other hard substrates in the North Sea. Compared to previous assessments of biodiversity with eDNA metabarcoding at the same site, the biodiversity detected in 2019 was very low. However, biodiversity levels may differ from year to year. Moreover, the samples were not taken at the same time points and are therefore not directly comparable and the methodology only included organisms that could be collected by hand (visible to the eye) with a focus on fauna attached to the rope and kelp. It is advised to combine classical morphological biodiversity assessment and eDNA metabarcoding in future assessments to compare results in order to determine the best-suited methodology for biodiversity assessments. Biodiversity in the seaweed farm should be assessed repeatedly every 5 years to check for temporal alterations in fauna composition, especially when cultivation structures, such as anchors, are deployed throughout several years. In subproject 2 “Cultivation” seasonal variation in biomass productivity and chemical composition of kelp was evaluated in order to determine the optimal time point for harvesting in relation to the desired end product. Biomass production at the test-farm was very low in 2019, compared to previous years and a seaweed farm test location near Helgoland in the North Sea. Below 4m environmental conditions for growth were unfavourable (mainly light limitation) for Saccharina latissima. Both in 2018 and 2019 large differences in standing crops over time and depth were observed. Contrary, true protein levels varied only slightly over time. If protein is the target product, final biomass yield of S. latissima will determine the profitability of the mariculture. A combination of economic analyses and growth experiments may assist in determining the optimal cultivation technique. The 2018 experiments performed at the North Sea Farm showed large seasonal variability in the chemical composition of seaweed tissue, and high amounts of nitrogen-containing compounds besides proteins variations. Therefore in 2019, nitrogen, starch and nitrate content in the seaweed tissue were analysed. Nitrate content in S. latissima varied throughout the season and could not fully explain the difference between N measured by Dumas and true protein content in the 2019 samples. Therefore, other seaweed components containing nitrogen must explain this variation, e.g. its accumulation in cellular nitrate pools. As a final note, in order to improve the understanding of environmental conditions in the farm it is recommended that nitrate and phosphate concentrations, two essential macronutrients for growth in seaweeds, should be assessed in the water column at different depths and time points.
    Raising the steaks: How one city in the Netherlands wants to feed the world
    Barbosa, M.J. ; Meer, I.M. van der; Dicke, M. ; Werf, A.K. van der; Goot, A.J. van der; Wichers, H.J. - \ 2019
    Development of Offshore Seaweed Cultivation : food safety, cultivation, ecology and economy : synthesis report 2018
    Jansen, H.M. ; Tonk, Linda ; Werf, A. van der; Meer, I. van der; Tuinen, S. van; Burg, S. van der; Veen, J. ; Bronswijk, L. ; Brouwers, E. - \ 2019
    IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C012/19) - 17
    Technical upscaling of seaweed cultivation : Proseaweed Dossier (project AF-16202)
    Werf, A.K. van der - \ 2018
    Wageningen University & Research - 3 p.
    De waarde van zeewier (KennisOnline in beeld 2018)
    Werf, A.K. van der; Jansen, H.M. - \ 2018
    Kennisonline (WUR)
    Performance of five ulva strains: productivity, chemical composition and nutrient dynamics and selection criteria for farming practices and ecosystem interactions
    Jansen, H.M. ; Nederlof, M.A.J. ; Meer, I.M. van der; Werf, A.K. van der - \ 2018
    - 1 p.
    Growing Azolla to produce sustainable protein feed: The effect of differing species and CO2 concentrations on biomass productivity and chemical composition.
    Brouwer, Paul ; Schluepmann, Henriette ; Nierop, K.G.J. ; Elderson, J. ; Bijl, P.K. ; Meer, I.M. van der; Visser, W. de; Reichart, Gert Jan ; Smeekens, S. ; Werf, A.K. van der - \ 2018
    Journal of the Science of Food and Agriculture 98 (2018)12. - ISSN 0022-5142 - p. 4759 - 4768.
    Background: Since available arable land is limited and nitrogen fertilizers pollute the environment, cropping systems ought to be developed that do not rely on them. Here we investigate the rapidly growing, N2 -fixing Azolla/Nostoc symbiosis for its potential productivity and chemical composition to determine its potential as protein feed. Results: In a small production system, cultures of Azolla pinnata and Azolla filiculoides were continuously harvested for over 100 days, yielding an average productivity of 90.0-97.2 kg dry weight (DW) ha-1  d-1 . Under ambient CO2 levels, N2 fixation by the fern's cyanobacterial symbionts accounted for all nitrogen in the biomass. Proteins made up 176-208 g kg-1 DW (4.9 × total nitrogen), depending on species and CO2 treatment, and contained more essential amino acids than protein from soybean. Elevated atmospheric CO2 concentrations (800 ppm) significantly boosted biomass production by 36-47%, without decreasing protein content. Choice of species and CO2 concentrations further affected the biomass content of lipids (79-100 g kg-1 DW) and (poly)phenols (21-69 g kg-1 DW). Conclusions: By continuous harvesting, high protein yields can be obtained from Azolla cultures, without the need for nitrogen fertilization. High levels of (poly)phenols likely contribute to limitations in the inclusion rate of Azolla in animal diets and need further investigation. © 2018 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
    Metabolic adaptation, a specialized leaf organ structure and vascular responses to diurnal N2 fixation by nostoc azollae sustain the astonishing productivity of azolla ferns without nitrogen fertilizer
    Brouwer, Paul ; Bräutigam, Andrea ; Buijs, Valerie A. ; Tazelaar, Anne O.E. ; Werf, Adrie van der; Schlüter, Urte ; Reichart, Gert Jan ; Bolger, Anthony ; Usadel, Björn ; Weber, Andreas P.M. ; Schluepmann, Henriette - \ 2017
    Frontiers in Plant Science 8 (2017). - ISSN 1664-462X
    Aquatic ferns - Azolla/nostoc azollae symbiosis - Clock evolution - Diel cycling - Dinitrogen fixation - Heterocystous cyanobacteria - Rna-seq - Vasculature
    Sustainable agriculture demands reduced input of man-made nitrogen (N) fertilizer, yet N2 fixation limits the productivity of crops with heterotrophic diazotrophic bacterial symbionts. We investigated floating ferns from the genus Azolla that host phototrophic diazotrophic Nostoc azollae in leaf pockets and belong to the fastest growing plants. Experimental production reported here demonstrated N-fertilizer independent production of nitrogen-rich biomass with an annual yield potential per ha of 1200 kg-1 N fixed and 35 t dry biomass. 15N2 fixation peaked at noon, reaching 0.4 mg N g-1 dry weight h-1. Azolla ferns therefore merit consideration as protein crops in spite of the fact that little is known about the fern’s physiology to enable domestication. To gain an understanding of their nitrogen physiology, analyses of fern diel transcript profiles under differing nitrogen fertilizer regimes were combined with microscopic observations. Results established that the ferns adapted to the phototrophic N2-fixing symbionts N. azollae by (1) adjusting metabolically to nightly absence of N supply using responses ancestral to ferns and seed plants; (2) developing a specialized xylem-rich vasculature surrounding the leaf-pocket organ; (3) responding to N-supply by controlling transcripts of genes mediating nutrient transport, allocation and vasculature development. Unlike other non-seed plants, the Azolla fern clock is shown to contain both the morning and evening loops; the evening loop is known to control rhythmic gene expression in the vasculature of seed plants and therefore may have evolved along with the vasculature in the ancestor of ferns and seed plants.
    Effects of micronutrients micnobit and salt fertilization on lettuce
    Blom-Zandstra, M. ; Visser, W. de; Werf, A.K. van der; Lee, Martijn van der; Vos, Ric de; Jongschaap, R.E.E. ; Dimkpa, Christian ; Bindraban, P.S. - \ 2016
    Washington : Virtual Fertilizer Research Centre (VFRC Report 2016/1) - 42
    SPARK-UP; Seaweed Production And Refining of Kelp, Ulva and Palmaria : 2013-2016
    Wald, J. ; Visser, W. de; Brandenburg, W.A. ; Jongschaap, R.E.E. ; Werf, A.K. van der; Deelman, Berth-Jan ; Helmendach-Nieuwenhuize, Carola - \ 2016
    Plant Research International - 144
    seaweeds - biobased economy - seaweed culture - biomass production - biomass conversion - aquatic biomass - biorefinery - seaweed products - applications - applied research - cropping systems - marketing channels - zeewieren - biobased economy - zeewierenteelt - biomassa productie - biomassaconversie - aquatische biomassa - bioraffinage - zeewierproducten - toepassingen - toegepast onderzoek - teeltsystemen - marketingkanalen
    In het SPARK-UP project, waarin de partners Arkema, PRI-WUR en North Seaweed samenwerkten aan de ontwikkeling van toepassing van zeewier in de biobased economy, is de afgelopen jaren veel werk verzet. In een bassin op het terrein van Arkema, heeft PRI een teeltsysteem opgezet en in gebruik genomen, om onder gecontroleerde omstandigheden zeewier te telen in Westerscheldewater dat in het bassin was ingenomen. Arkema heeft gewerkt aan de raffinage van wieren, met name gericht op de suikers. North Seaweed heeft zich geconcentreerd op het ontwikkelen van businesscases van geraffineerde eiwitten en alginaten uit zeewier en bij het gebruik van de hele wieren als plantversterkers.
    Kweekvlees, insecten, zeewier - wat ligt er over vijf jaar op ons bord?
    Dicke, Marcel ; Ende, Ernst van den; Woltering, Ernst ; Werf, Adrie van der - \ 2016

    De groeiende wereldbevolking moet op zoek naar alternatieve voedselbronnen. NRC-redacteur Carlijn Vis bespreekt vier toekomstbestendige voedselsoorten.

    North-Sea-Weed-Chain: sustainable seaweed from the North Sea; an exploration of the value chain
    Groenendijk, F.C. ; Bikker, P. ; Blaauw, R. ; Brandenburg, W.A. ; Burg, S.W.K. van den; Harmsen, P.F.H. ; Jak, R.G. ; Kamermans, P. ; Krimpen, M.M. van; Prins, H. ; Stuiver, M. ; Werf, A.K. van der; Scholl, M.M. ; Wald, J. - \ 2016
    IMARES (Report / IMARES C055/16) - 94
    seaweeds - seaweed culture - seaweed products - feasibility studies - economic viability - public-private cooperation - economic cooperation - projects - biobased economy - zeewieren - zeewierenteelt - zeewierproducten - haalbaarheidsstudies - economische haalbaarheid - publiek-private samenwerking - economische samenwerking - projecten - biobased economy
    Zeewier is een potentieel belangrijke voedselbron en grote duurzame koolstofbron voor de biobased economy. Met de groeiende wereldbevolking is het noodzakelijk om voor ons voedsel meer te kijken naar de zee als ‘landbouwgebied’. Boeren op zee is een grote uitdaging. Het vereist grote investeringen in infrastructuur. Voordat ondernemers hierin kunnen investeren moeten realistische vooruitzichten zijn op kweekmogelijkheden en winstgevende eindproducten. Dit project had tot doel de verschillende schakels in de keten van zeewierproductie tot vermarkting tegen het licht te houden. Duurzaamheid van de productie is hierbij leidend geweest.
    Lipid Yield and Composition of Azolla filiculoides and the Implications for Biodiesel Production
    Brouwer, Paul ; Werf, Adrie van der; Schluepmann, Henriette ; Reichart, Gert Jan ; Nierop, Klaas G.J. - \ 2016
    Bio Energy Research 9 (2016)1. - ISSN 1939-1234 - p. 369 - 377.
    Azolla - Biochemicals - Biodiesel - Feedstock - Fern - Lipids

    The aquatic fern Azolla is one of the fastest-growing nitrogen-fixing plants on Earth and therefore considered as a potential source of biomass for bioenergy production. The lipid fraction from Azolla filiculoides was analyzed to investigate whether it suited biodiesel production. Since the productivity of Azolla is further increased at higher CO2 concentrations, A. filiculoides biomass was produced at 800 ppm CO2 mimicking a cultivation system utilizing CO2 waste from industry. The harvested biomass contained 7.92 ± 0.14 % dry weight (dw) crude lipids. Drying conditions did not significantly affect lipid composition or yields, indicating that drying conditions may be energetically optimized without the risk of product loss. Total lipid extracts contained 4.2 ± 0.38 % free fatty acids. Of the crude lipid fraction, 41 ± 13 % consisted of fatty acids that were converted into fatty acid methyl esters upon saponification in methanol. Unique mid-chain (di)hydroxy compounds constituted 7.2 ± 2.8 % of the crude lipids. Based on the fatty acid profile, it was estimated that Azolla biodiesel meets requirements set by the EN14214 standard on fuel density, cetane number, and iodine value. The cold filter plugging point (CFPP), however, is expected to be too high due to relatively high concentrations of lignoceric acid and the presence of the mid-chain (di)hydroxy compounds. To produce high-quality biodiesel from Azolla lipids, therefore, a fractionation step will be required removing these compounds. As an advantage, the long-chain alcohols and (di)hydroxy fatty acids obtained after fractionation may provide a valuable secondary product stream with applications to chemical industry and nutrition.

    Azolla domestication towards a biobased economy?
    Brouwer, Paul ; Brautigam, A. ; Kulahoglu, C. ; Tazelaar, A.O.E. ; Kurz, S. ; Nierop, K.G.J. ; Werf, A.K. van der; Weber, A.P.M. ; Schluepmann, H. - \ 2014
    New Phytologist 202 (2014)3. - ISSN 0028-646X - p. 1069 - 1082.
    Due to its phenomenal growth requiring neither nitrogen fertilizer nor arable land and its biomass composition, the mosquito fern Azolla is a candidate crop to yield food, fuels and chemicals sustainably. To advance Azolla domestication, we research its dissemination, storage and transcriptome. Methods for dissemination, cross-fertilization and cryopreservation of the symbiosis Azolla filiculoides–Nostoc azollae are tested based on the fern spores. To study molecular processes in Azolla including spore induction, a database of 37 649 unigenes from RNAseq of microsporocarps, megasporocarps and sporophytes was assembled, then validated. Spores obtained year-round germinated in vitro within 26 d. In vitro fertilization rates reached 25%. Cryopreservation permitted storage for at least 7 months. The unigene database entirely covered central metabolism and to a large degree covered cellular processes and regulatory networks. Analysis of genes engaged in transition to sexual reproduction revealed a FLOWERING LOCUS T-like protein in ferns with special features induced in sporulating Azolla fronds. Although domestication of a fern–cyanobacteria symbiosis may seem a daunting task, we conclude that the time is ripe and that results generated will serve to more widely access biochemicals in fern biomass for a biobased economy.
    Rietteelt als mogelijke bouwsteen voor een duurzaam water- en bodembeheer in natte veengebieden
    Korevaar, H. ; Werf, A.K. van der - \ 2014
    Wageningen : Plant Research International, Business Unit Agrosysteemkunde (Rapport / Plant Research International 544) - 48
    phragmites - landgebruik - bodembeheer - waterzuivering - biomassa - ecosysteemdiensten - bodemdaling - veenweiden - haalbaarheidsstudies - utrecht - phragmites - land use - soil management - water treatment - biomass - ecosystem services - subsidence - peat grasslands - feasibility studies - utrecht
    De teelt van riet is één van de mogelijke alternatieven voor het huidige landgebruik en systeem van waterbeheer in de veenweidegebieden en kan helpen de bodemdaling te beperken. In deze haalbaarheidsstudie komen aan bod: de thema's water, bodem, broeikasgassen, natuurwaarden, maatschappelijke aspecten, en economische aspecten. Vervolgens komen de mogelijke functies aan bod: waterzuivering, waterberging, bodemdaling, buffering van natuur, oeverbescherming, biodiversiteit, biomassateelt en recreatie. De marktprijs van rietbiomassa is momenteel te laag om rietteelt rendabel te maken. Een betaling voor ecosysteemdiensten is nog niet genoeg ontwikkeld om daarmee een goede beloning voor o.a. waterzuiverinbg, klimaatadaptaie en bodemdaling te genereren.
    Balancing carbon sequestration and GHG emissions in a constructed wetland
    Klein, J.J.M. de; Werf, A.K. van der - \ 2014
    Ecological Engineering 66 (2014). - ISSN 0925-8574 - p. 36 - 42.
    waste-water treatment - phragmites-australis - methane emission - nitrous-oxide - emergent macrophytes - ecosystem services - restored wetlands - greenhouse gases - fresh-water - denitrification
    In many countries wetlands are constructed or restored for removing nutrients from surface water. At the same time vegetated wetlands can act as carbon sinks when CO2 is sequestered in biomass. However, it is well known that wetlands also produce substantial amounts of greenhouse gasses CH4 and N2O. Especially N2O, resulting from nitrification and denitrification, is a very potent GHG. To assess the environmental sustainability of constructed wetlands the benefit of carbon sink and the downside of GHG emissions have to be evaluated. Since nutrient and carbon cycles in wetlands are complex and variable among wetlands and in time such a balance always contains uncertainties. Several studies have addressed this issue and indicated that CW can be either a sink or a source of CO2 equivalents depending on the time scale of research and the environmental and management conditions involved. Here we balance carbon sequestration with CH4 and N2O emissions in a multi-functional constructed wetland, dominated by emergent Phragmites vegetation. Detailed measurements were combined with a nitrogen budget, and all fluxes were expressed as a range indicating the uncertainties in measurements and extrapolation techniques. Measured methane emissions were variable and showed clear relationship with temperature and density of the emergent vegetation. Average CH4 emissions in the vegetation were 7.8 at 15 °C and 24.5 mg m-2 h-1 at 24 °C. Estimated N2O emissions ranged from 0.5 to 1.9 g m-2 y-1. After converting the fluxes to CO2 equivalents we concluded that the Lankheet constructed wetland is most likely a sink of CO2 in the present conditions. Annual net sequestration of CO2 amounts 0.27–2.4 kg m-2 y-1 which represents 12–67% of the CO2 fixation in the biomass. N2O emissions represent a substantial part of the total effect of GHG emissions (12–29%) and should not be disregarded in budget studies. We acknowledge the limitations and uncertainties of our estimates, however, we are confident that our findings contribute to assessing the environmental sustainability of constructed wetlands.
    Azolla: from floating fern to renewable resource
    Werf, Adrie van der - \ 2013
    azolla - fuel crops - aquatic biomass - biomass production - new crops

    Documentary september 2013

    Azolla aandacht in EenVandaag documentaire “Groene en Republikeinse Dromen voor de Koning”
    Werf, Adrie van der - \ 2013

    Azolla aandacht in “eenvandaag” documentaire “Groene en Republikeinse Dromen voor de Koning”

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