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Influence of Anaerobic Digestion Processes on the Germination of Weed SeedsEinfluss anaerober Gärprozesse auf die Keimung von Unkrautsamen

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Anaerobic digestion (AD) produces bioenergy and bio-fertilizer. However, weed seeds can contaminate the substrates for biogas production. This work assesses seed viability of four weeds species origin from Germany and China under AD conditions at 37, 42 and 52 °C with different retention times. All investigated seeds were inactivated after 12 h at 52 °C, 128 h at 42 °C and 512 h at 37 °C under AD treatment. Inactivation duration varying between species and a global test showed that the countries of seeds origin have a significant effect on inactivation times. For two species, by contrast, short treatment times increased the germination rate which increases the risk of weed dispersal. An anoxic water bath treatment with identical temperatures resulted in longer deactivation times, indicating that other factors also play a role in the weed seeds elimination. The results indicate that the risk of weed seed spreading through digestate application can be minimized by an adequate retention time.
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ORIGINAL ARTICLE
https://doi.org/10.1007/s10343-020-00500-y
Gesunde Pflanzen (2020) 72:181–194
Influence of Anaerobic Digestion Processes on the Germination of
Weed Seeds
Lijun Zhou1,2 · Benedikt Hülsemann1·WolfgangMerkle
1· Jianbin Guo2·RenjieDong
2·Hans-PeterPiepho
3·
Roland Gerhards4· Joachim Müller5· Hans Oechsner1
Received: 29 October 2019 / Accepted: 12 February 2020 / Published online: 18 February 2020
© The Author(s) 2020, corrected publication 2021
Abstract
Anaerobic digestion (AD) produces bioenergy and bio-fertilizer. However, weed seeds can contaminate the substrates for
biogas production. This work assesses seed viability of four weeds species origin from Germany and China under AD
conditions at 37, 42 and 52 °C with different retention times. All investigated seeds were inactivated after 12h at 52°C,
128h at 42 °C and 512 h at 37 °C under AD treatment. Inactivation duration varying between species and a global test
showed that the countries of seeds origin have a significant effect on inactivation times. For two species, by contrast, short
treatment times increased the germination rate which increases the risk of weed dispersal. An anoxic water bath treatment
with identical temperatures resulted in longer deactivation times, indicating that other factors also play a role in the weed
seeds elimination. The results indicate that the risk of weed seed spreading through digestate application can be minimized
by an adequate retention time.
Keywords Biogas plant · Digestate application · Seed germination · Inactivation · Retention time
Einuss anaerober Gärprozesse auf die Keimung von Unkrautsamen
Zusammenfassung
Die anaerobe Vergärung (AD) produziert Bioenergie und Biodünger. Im Biodünger können Unkrautsamen mit dem Substrat
in den Gärprozess gelangen und auf die Felder verteilt werden. In dieser Arbeit wird die Lebensfähigkeit der Samen von
vier Unkrautarten aus Deutschland und China unter anaeroben Bedingungen bei 37, 42 und 52°C mit unterschiedlichen
Verweilzeiten bewertet. Alle untersuchten Samen wurden nach 12h bei 52 °C, 128h bei 42°C und 512 h bei 37°C inaktiviert.
Die Inaktivierungsdauer zwischen den Samen aus unterschiedlichen Herkunftsländern variiert statistisch signifikant. Die
Keimrate von zwei Arten wurde bei einer kurzen Verweildauer erhöht, was das Risiko der Unkrautausbreitung kurzzeitig
erhöhte. Eine anaerobe Wasserbadbehandlung mit identischen Temperaturen führte zu längeren Deaktivierungszeiten, was
darauf hinweist, dass auch andere Faktoren bei der Eliminierung von Unkrautsamen eine Rolle spielen. Die Ergebnisse
zeigen, dass das Risiko der Ausbreitung von Unkrautsamen im Gärrest bei ausreichender Verweilzeit deutlich verringert
wird.
Schlüsselwörter Biogasanlage · Gärrestausbringung · Samenkeimung · Inaktivierung · Verweilzeit
Lijun Zhou
lijun.zhou@uni-hohenheim.de
1State Institute of Agricultural Engineering and Bioenergy,
University of Hohenheim, Stuttgart, Germany
2College of Engineering, China Agricultural University,
Key Laboratory for Clean Renewable Energy Utilization
Technology, Ministry of Agriculture and Rural Affairs,
100083 Beijing, China
3Biostatistics Unit (340c), Institute of Crop Science, University
of Hohenheim, 70599 Stuttgart, Germany
4Institute of Phytomedicine (360), University of Hohenheim,
70599 Stuttgart, Germany
5Institute of Agricultural Engineering, Tropics and Subtropics
Group (440e), University of Hohenheim, 70599 Stuttgart,
Germany
K
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... Most studies of seed survival in AD have used lab-scale, experimental reactors, or similar systems. Methods ranged from bottles with a capacity of about 0.5 L operated in batch mode (e.g., [29,30]) to 400 L completely stirred tank reactors (e.g., [31,32]). In full-scale, commercial biogas reactors, providing facilities and farm activities for potential seed contamination under real conditions, nine seed survival studies have been conducted to date [14,15,17,[25][26][27][33][34][35]. ...
... [23]). Finally, six studies have compared the effects of two or more AD systems on seed survival [14,15,[25][26][27]32]. However, even in these, the mode of operation and process temperature often differed between the systems compared. ...
... In the ER and CR treatments, the inactivation curves had a similar shape as in the WB treatment and were only shifted towards faster inactivation. The shifts occurred particularly in C. album and were also found by Zhou et al. [32] when comparing the survival of Digitaria sanguinalis (purple crabgrass, Poaceae) in anoxic water baths and lab-scale reactors. These shifts in the course of inactivation between WB and reactor treatments indicate the involvement of additional mortality factors in the reactors, which include microorganisms contributing to AD and biochemicals such as organic acids, enzymes and alcohols [23]. ...
Article
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When plant biomass is anaerobically digested, seeds may survive the energy production process and contaminate the digestate. Hard-seeded (HS), i.e., physically dormant, species were found to be difficult to inactivate. Here, we aimed to verify this finding from lab-scale experimental reactors (ERs) in a full-scale commercial reactor (CR). In addition, we tested seed survival in a pH-buffered water bath (WB). Seeds were exposed to CR, ER and WB treatments at 42 °C for a maximum of 36 days. The viability of seeds was checked by measuring germination and response to tetrazolium staining and modeled as a function of exposure time using a dose–response approach. CR killed seeds more effectively than ER and WB treatments. The non-HS reference species, Chenopodium album, was completely inactivated by all treatments. Responses of the HS species ranged from complete inactivation to complete insensitivity. The most resistant was Malva sylvestris. The least resistant species were inactivated mainly by temperature, while additional mortality factors were effective in the more resistant species. We concluded that mesophilic AD in CRs can reduce the risk of seed contamination in the digestate for non-HS but not for HS species. Moreover, WB treatments seem suitable to estimate the minimum mortality of non-HS species in CR.
... Most available studies on seed survival in AD dealt with weeds (e.g., Jeyanayagam and Collins, 1984;Šarapatka et al., 1993;Schrade et al., 2003;Eckford et al., 2012;Westerman et al., 2012a;Johansen et al., 2013;Zhou et al., 2020). Of the plants whose biomass is (intended to be) used as biogas feedstock, only 14 species have been studied to date (Heiermann et al., 2010;Strauß et al., 2012;van Meerbeek et al., 2015;Baute et al., 2016;Sölter et al., 2016;Starfinger and Sölter, 2016;Hassani et al., 2021). ...
... In general, seed viability decreases exponentially with time, with the seeds remaining unaffected by AD during an initial lagphase (Westerman and Gerowitt, 2013). In addition, higher temperatures result in a greater decrease in seed viability (reviewed by Westerman and Gerowitt (2013) and confirmed by Johansen et al. (2013);Oechsner et al. (2018), and Zhou et al. (2020). In particular, ADs under thermophilic conditions (approx. ...
... 45-55 • C) appear to be significantly more effective in killing seeds than mesophilic ones (approx. 30-45 • C) (Šarapatka et al., 1993;Lorenz et al., 2001;Schrade et al., 2003;Westerik and Kleizen, 2006;Leonhardt et al., 2010;Johansen et al., 2013;Zhou et al., 2020). This implies that ADs in the mesophilic temperature range pose a higher risk of unintended seed spread -as pointed out by Westerman and Gerowitt (2013); Alsanius et al. (2021), andHassani et al. (2021). ...
Article
Full-text available
The use of wildflower species as biogas feedstock carries the risk that their seeds survive anaerobic digestion (AD) and cause weed problems if spread with the digestate. Risk factors for seed survival in AD include low temperature, short exposure and hardseededness (HS). However, it is not possible to predict how AD will affect seed viability of previously unstudied species. In laboratory-scale reactors, we exposed seeds of eight species from a mixture of flowering wild plants intended as biogas feedstock and three reference species to AD at two mesophilic temperatures. Half of the species were HS, the other was non-HS (NHS). Viability was determined using a combination of tetrazolium and germination tests. Viability and germinability were modeled as functions of exposure time using a dose-response approach. Responses to AD varied considerably among species, and none of the considered influencing factors (time, temperature, HS) had a consistent effect. Seed lots of a species differed in inactivation times and seed-killing efficacy. The HS species Melilotus officinalis, Melilotus albus, and Malva sylvestris were particularly AD-resistant. They were the only ones that exhibited biphasic viability curves and tended to survive and germinate more at 42°C than at 35°C. Viability of the remaining species declined in a sigmoidal curve. Most NHS species were inactivated within a few days (Cichorium intybus, Daucus carota, Echium vulgare, and Verbascum thapsus), while HS species survived longer (Malva alcea). AD stimulated germination in the HS species A. theophrasti and its AD-resistance overlapped with that of the most resistant NHS species, C. album and tomato. In all seed lots, germinability was lost faster than viability, implying that mainly dormant seeds survived. After the maximum exposure time of 36 days, seeds of HS species and Chenopodium album were still viable. We concluded that viability responses to mesophilic AD were determined by the interplay of AD-conditions and species- and seed-lot-specific traits, of which HS was an important but only one factor. For the use of wildflowers as biogas feedstock, we recommended long retention times and special care with regard to HS species.
... Therefore, factors that affect seed survival in AD might also affect it in digestate. The most important being exposure time and temperature (e.g., Johansen et al., 2013;Zhou et al., 2020;Hahn et al., 2022). In particular, the duration of AD should be considered. ...
... effect, whereas high doses cause inhibition (Calabrese and Baldwin, 2002;Kozumbo and Calabrese, 2019). In fact, hormesis-like responses of seed viability were not only described by Hahn et al. (2022), but also earlier for treatments in AD and water baths (e.g., Schrade et al., 2003;Tanke et al., 2019;Zhou et al., 2020). For the case of M. sylvestris in DS, the increase in seed viability continued until the end of the observation period, resulting in a negative seed-killing efficacy V max : maximum proportion of V; defined to be identical for both treatments. ...
Article
Full-text available
Introduction Plant seeds from weeds and energy crops have the potential to survive anaerobic digestion (AD). Species able to form physically dormant, i.e., hardseeded (HS) seeds seem particularly resistant. However, it is not yet known to what extent the storage of the digestate after AD affects seed viability. Methods Seed survival of five HS and six non-HS (NHS) species was investigated in three combinations of digestate storage (DS) and AD. First, untreated seeds were exposed to DS for maximum 12 weeks. To simulate short-circuited AD (ADshort) in biogas reactors, seeds were second subjected to lab-scale AD for 1 day before DS. Third, seeds of six species were exposed to full-scale AD (ADfull) followed by DS. Seed viability was determined using a combination of germination tests and tetrazolium staining. Viability was modeled as a function of exposure time. Results and discussion Seed viability was affected by DS, AD and AD + DS, but responses varied greatly between species and treatments. With increasing exposure time, viability decreased after a lag-phase, remained stable or even increased. The NHS species Cichorium intybus, Daucus carota, Echium vulgare, and Verbascum thapsus were most susceptible, with seed-killing close to 100% if DS was involved. The HS species Malva sylvestris, Melilotus albus and Melilotus officinalis were most resistant. They survived all treatments and were alive after 35 days of ADfull plus 3 months of DS. The resistance potential of the HS species Abutilon theophrasti and Malva alcea and of the NHS species Chenopodium album and two tomato varieties was intermediate. None of them survived ADfull + DS, but except A. theophrasti they were viable after ADshort + DS. With few exceptions, seed-killing by AD + DS was higher than that by AD alone. In conclusion, DS and AD + DS have the potential to reduce seed viability, but do not completely inactivate all species. Therefore, digestate can be contaminated with viable seeds and may lead to the spread of weeds, especially after a short-circuited AD. In order to ensure the sustainable use of digestates in terms of weeds, we recommend to investigate the factors contributing to seed inactivation and the quantity of seed introduced to AD.
... A positive aspect of anaerobic digestion in the formation of digestate is that it reduces pathogens, kills viruses, fungi, Listeria, Salmonella, and Escherichia coli bacteria, and inactivates plant seeds (Sassi et al., 2018;Zhou et al., 2020). The digestate can be used as a fertiliser in both liquid and solid form. ...
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The content of heavy metals in soil should be continuously monitored, especially in organic crops. Exceeding the permissible concentrations of these elements may lead not only to inhibition of plant growth but also to ingestion into the organisms of animals that feed on these plants. Heavy metals usually enter the soil via precipitation or manure. There is a noticeable increase in interest in digestate for fields fertilization. Therefore, the authors decided to test the heavy metal content in substrates (slurry and solid input) and digestate. The 15x3 samples tested showed that only trace amounts of heavy metals were present. The study shows that the content of these elements in the digestate is not the sum of the elements supplied to the digester with the substrates. In most of the samples tested, lead concentrations did not exceed 5 mg‧kg ⁻¹ . The lowest amounts of cadmium (an average of 0.28 mg‧kg ⁻¹ ) were observed in the slurry, and the highest (an average of 0.34 mg‧kg ⁻¹ ) in the solid substrate fed to the digester. Slurry had the lowest mercury and cadmium contents (average 0.012 mg‧kg ⁻¹ and 5.8 mg‧kg ⁻¹ ). The highest concentration of chromium was registered in the digestate (average 3 mg‧kg ⁻¹ ) and this was on average 0.3 mg‧kg ⁻¹ higher than the feedstock and 0.5 mg‧kg ⁻¹ than the slurry
... In biogas production, electricity and heat are also obtained, which can cover the farm's energy needs at which the biogas plant is built [12,13]. A positive aspect of anaerobic digestion in creating the digestate is that it reduces pathogens, kills viruses, fungi, Listeria, Salmonella, and Escherichia coli bacteria, and inactivates plant seeds [14][15][16][17]. Digested slurry has a less unpleasant odour and a more favourable consistency for further processing than slurry [18]. ...
Article
Full-text available
Using natural fertilisers in agriculture improves quantity and quality yields. They introduce macronutrients (nitrogen, phosphorus, and potassium) and micronutrients into the soil. Enriching the soil with organic substances through fertilisation with digestates requires the farmer to have considerable knowledge and accuracy in dosing due to the need to comply with permissible concentrations of macronutrients. The availability of nutrients in a digestate is closely dependent on the substrates used in the biogas plant, and it cannot be stated unequivocally that better yields of field crops will be achieved by using it as manure. Therefore, the authors conducted a two-year study of the effect of the fertilisation method on maise yields. Based on the research carried out, the fertiliser suitability of the digest was confirmed. Plants fertilised with it were characterised by the highest (compared to other fertilisation methods) grain yield (of 12.07 Mg per hectare on average). In addition, they were characterised by adequate plant height (3.15 m on average). The observations also indicate good emergence and satisfactory early vigour.
... Additionally, by providing more timely results to livestock farmers, precautions may be taken for contaminated manure such as treatment and/or spreading it on a nearby field and intensively monitoring over the next few years. Treatment options to reduce weed seed viability include composting for solid manure (Larney & Blackshaw, 2003;Tompkins et al., 1998;Wiese et al., 1998) or anaerobic digestion for liquid or slurry manure (Westerman & Gerowitt, 2013;Zhou et al., 2020) if facilities are located nearby. In areas where Palmer amaranth has not become established, rapid testing will be especially important to allow livestock operators to take precautions to reduce the risk of spread. ...
Article
Full-text available
One pathway by which Palmer amaranth (Amaranthus palmeri S. Watson) invades new areas is through importation of contaminated livestock feed, which then contaminates land‐applied manure. If contaminated feed is suspected, detection tools are needed to test manure, but traditional methods are time consuming and often inconclusive. Although new genetic seed testing is making detection easier, methods to separate seed from contaminated manure are needed. Six methods were compared for their ability to recover 100 Palmer amaranth seeds added to bedded or nonbedded cattle manure: dry sieving, rinse sieving, manure saturation sieving without blending and with blending, and dispersion sieving without blending and with blending. Seed recovery was highest (>90%) with the rinse sieving method regardless of manure type. The dispersion methods are not recommended as they recovered <24.7% of seeds. Following each method, genetic testing successfully identified Palmer amaranth presence, indicating no interference of recovery method with DNA extraction.
... Still, only little information is available on the effect of temperature and exposure time on the most decisive factors, i.e. the infection potential and the reproductive rate of pest organisms. A study of the germination of seeds of E. crus-galli after AD showed that the origin of the seed lot could influence the time-temperature requirement (Zhou et al., 2020). Confounding results can also be obtained due to the absence of reliable pathogenicity tests, as in the case of Synchytrium endobioticum, where the latest recommendation is to microscopically examine samples, rather than conduct pathogenicity tests/bioassays (Schleusner et al., 2019). ...
Book
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2021). Assessment of treatment methods and validation criteria for composting and biogas facilities in relation to plant health risks and the risk of spreading alien organisms. Scientific Opinion of the Panel on Plant Health of the Norwegian Scientific Committee for Food and Environment. Assessment of treatment methods and validation criteria for composting and biogas facilities in relation to plant health risks and the risk of spreading alien organisms Preparation of the opinion The Norwegian Scientific Committee for Food and Environment (Vitenskapskomiteen format og miljø, VKM) appointed a project group to draft the opinion. The project group consisted of four VKM members and one project manager from the VKM staff. Two external referees commented on and reviewed the draft opinion. The Panel on Plant Health evaluated and approved the final opinion.
... Biogas is produced by the anaerobic microbiological degradation of organic compounds, and it usually contains two major components: methane and carbon dioxide; it can also include other gases such as hydrogen sulfide and nitrogen (N 2 ) [6]. The positive aspect of anaerobic digestion is the fact that it reduces pathogens, kills viruses, fungi, bacteria of the genus Listeria, Salmonella and Escherichia coli and inactivates plant seeds [7][8][9][10][11]. The secondary product of this wet fermentation is digestate [12]. ...
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In a two-year vegetation field experiment, the fertilizing effects of by-products from the agricultural biogas plant—a solid phase of digestate (SPD) and a liquid phase of digestate (LPD)—were studied and compared with mineral fertilization (NPK) on the biomass yield, content and nutrient uptake by Cannabis sativa L. plants. Furthermore, the agrochemical properties of the soil were evaluated at the end of the experiment. In all variants of the experiment, a uniform nitrogen dose of 150 kg/ha was applied. The dose of other nutrients corresponded to the fertilizer used. The biggest fertilizing effect, and therefore the greatest hemp biomass yield and nutrient uptake, was demonstrated when combining SPD and LPD fertilization in one treatment. However, the differences were statically insignificant (p ≤ 0.05). The applied amount appeared to be sufficient for the nutrition of hemp plants and was comparable to mineral fertilization. The distribution of nutrients between leaves and stems varied depending on the nutrient monitored. Analyses after the end of the experiment did not show different contents of accessible nutrients in the soil on the studied variants. The content of accessible risk elements in the soil was not affected by the application of the SPD and the LPD. The experiment showed that cannabis plants are able to achieve equivalent biomass yields (8.68 t/ha) using the combination of LPD and SPD by-products from a biogas plan compared to commercial mineral fertilizer (7.43 t/ha). Therefore, we can recommend a split application of LPD and SPD as a suitable alternative to mineral fertilization. Due to prolonged nutrient release from SPD, we can expect a smaller negative environmental impact than current fertilization practices.
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This updated and much revised third edition of Seeds: Physiology of Development, Germination and Dormancy provides a thorough overview of seed biology and incorporates much of the progress that has been made during the past fifteen years. With an emphasis on placing information in the context of the seed, this new edition includes recent advances in the areas of molecular biology of development and germination, as well as fresh insights into dormancy, ecophysiology, desiccation tolerance, and longevity. Authored by preeminent authorities in the field, this book is an invaluable resource for researchers, teachers, and students interested in the diverse aspects of seed biology. © Springer Science+Business Media, LLC 2013. All rights are reserved.