Spruce bark beetles as a biological waste that can be processed in a biogas plant

Biogas plays an important role in reducing the amount of biowaste that is converted to methane which is usable by multiple pathways in the energy sector. Bark beetles are among the most important pests of spruce forests in Europe. Principal measures of managing bark beetle populations include trapping them with pheromone traps. Biomass of bark beetles collected by the traps constitutes a waste of forest resources that could potentially be processed in biogas plants. The aim of this study was to provide information about the trapping of bark beetles by pheromone traps in Tatra National Park during 2005-2018 and to verify the energy potential of a combination of liquid digestate and bark beetle biomass collected by pheromone traps. The bark beetle biomass is a seasonal small-volume nitrogen-rich material which could be processed at agricultural biogas plants. The biochemical methane potential batch test performed at 40 degrees C showed a high degree of digestion of milled beetles within 40 days, with a methane production of 0.242 Nm(3) per kilogram of total solids (TS). The single-stage low-solids mesophilic fed-batch anaerobic digestion of untreated beetles was carried out in a lab-scale rotary drum reactor. Within 52 days, the average organic loading rate was 1.019 kg VS m(-3)day(-)(1), where VS stands for volatile solids. The specific biogas and methane production reached 0.218 Nm(3)kg(-1) TS and 0.140 Nm(3)kg(-1) TS, respectively. The cuticles of the beetle bodies were not obviously disturbed by the fermentation process. The digestate was quite rich in nitrogen, but the other element contents did not differ too much from fertilizer made from manure or phytomass.Web of Science44217916

Simple Is Best: Pine Twigs Are Better Than Artificial Lures for Trapping of Pine Weevils in Pitfall Traps

The large pine weevil Hylobius abietis (Linnaeus 1758) is the main pest of coniferous seedlings in Europe and causes substantial damage in areas that have been clear-cut or otherwise disturbed. We compared the efficacy of different attractants for the capture of H. abietis adults in white pitfall traps. The field experiment was performed from mid-April to the end of August 2018 at six plots in Central Europe located in spruce stands that had been clear-cut. At each plot, we compared five attractants: one pine twig with ethanol, Hylodor, alpha-pinene + ethanol, turpentine oil and ethanol (separated), and turpentine oil + ethanol (not separated). Traps without attractant served as a control. Six traps for each attractant or control were distributed at each plot. Of the total number of H. abietis adults trapped, 43.3%, 20.5%, 17.9%, 9.8%, 8.5% and 0.5% were captured in traps with pine twigs with ethanol, alpha-pinene, Hylodor, turpentine, oil + ethanol (separated), turpentine oil + ethanol (combined), and no attractant, respectively. The bottom of each trap contained propylene glycol to kill and preserve beetles. The small number of beetles captured in the control traps confirms that the propylene glycol:water mixture did not influence the trapping of H. abietis. The use of pitfall traps with a suitable attractant (especially pine twigs and ethanol) should be useful for monitoring of H. abietis, because it is simple and cost-effective. The use of such pitfall traps to control H. abietis by mass trapping would require 50 to 100 traps per ha