Risk of Invasive Lupinus polyphyllus Seed Survival in Biomass Treatment Processes

Abstract

Invasive plant species threaten native species and habitats causing ecologic, economic and social burden. When creating climate friendly solutions by utilizing plant biomasses in biogas and fertilizer production, safety should be ensured concerning the use of residues. This study concentrates on the treatment of biomasses containing invasive plant material by tunnel and windrow composting, and by farm-scale and laboratory-scale anaerobic digestion (AD) in mesophilic conditions. Germination of the nationally settled and harmful invasive species Lupinus polyphyllus Lindl. was investigated after these processes. In addition, the role of the conditions found in the processes that destroyed seeds were studied, such as the time of exposure, temperature and static pressure. Dormant seeds are well protected against harsh conditions and can survive through various stress factors, but also become vulnerable as more factors are combined and time of exposure is extended. Our results suggest that the risks involved for the utilization of harmful invasive species increase with mesophilic temperatures and single treatments if the processing conditions are not stabile. One-month treatment with windrow composting showed a high risk for dormant seeds of L. polyphyllus seeds to survive, whereby extending the processing time reduced it substantially. Hard coated seeds can thus be broken with a combination of thermophilic temperatures, moisture and static pressure.

Viability of Wildflower Seeds After Mesophilic Anaerobic Digestion in Lab-Scale Biogas Reactors

“…(soybean), Lupinus polyphyllus LINDLEY (garden lupin), Trifolium pratense L. (red clover) and Vicia tetrasperma (L.) Schreb. (smooth vetch) had lost substantially more than 9% -36% viability when exposed to similar AD-conditions (35-38 • C, 7-30 days) (Leonhardt et al, 2010;Strauß et al, 2012;Westerman et al, 2012b;Hassani et al, 2021). Among the three members of the genus Malva studied, seed-killing efficacy was higher in M. alcea (this study) and Malva neglecta Wallr.…”

“…The second unique characteristic of the particularly ADresistant HS species was their tendency to lose viability faster and more severely at 35 • C than at 42 • C. Additionally, the range of responses was wider at 35 • C. This was in contrast to all other species studied to date. However, it must be put into perspective that (a) this response was prominent only in M. albus and (b) other Fabaceae and Malvaceae were each exposed to only one temperature in previous studies (Katovich et al, 2004;Leonhardt et al, 2010;Strauß et al, 2012;Westerman et al, 2012a,b;Hassani et al, 2021). Some of our observations in Melilotus sp.…”

“…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). With regard to the use of wildflower species as biogas feedstock, this could be problematic, as they are to be grown mainly in Germany, where 84% of biogas plants are mesophilic (vTI, 2009).…”

“…HS is common in the Fabaceae and occurs in members of the Malvaceae (Baskin et al, 2000), both of which are families of interest for biogas flowering mixtures (Vollrath, 2012). HS as a risk factor for high ADresistance potential and consequently for seed dispersal with the digestate has been explicitly mentioned by Leonhardt et al (2010), Westerman et al (2012a,b), and Hassani et al (2021). However, not all species resistant to AD are HS, so it is suspected that other seed traits may aid seed survival in AD as well (Westerman and Gerowitt, 2013).…”

“…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). Based on weeds studied through 2012, Westerman and Gerowitt (2013) identified plant groups whose seeds might have a higher probability of surviving AD than usual.…”