Performance of Liquids from Slow Pyrolysis and Hydrothermal Carbonization in Plant Protection

Abstract

The feasibility of thermochemical biomass conversion technologies can be improved if value-added applications for all fractions can be developed. One of such approaches is the use of liquid by-products from slow pyrolysis and hydrothermal carbonization (HTC) in plant protection. Liquids produced from slow pyrolysis of pine bark, pine forest residues, wheat straw, and willow, and from hydrothermal carbonization of willow, were analyzed in this study. In particular, potential active compounds were analyzed, covering the main volatile, simple organic compounds and numerous phenolic substances. Effectivity tests of the liquids as pest repellent (Arianta arbustorum), herbicide (Brassica rapa), and insecticide (Rhopalosiphum padi) indicated that slow pyrolysis liquid from willow was the most effective pesticide, followed by the liquid from wheat, bark, and forest residues. HTC liquid did not show any pesticidal activity due to low concentration of organic compounds. High content of acetic acid and other carboxylic acids, and the presence of dozens of different phenolic compounds seem to be the main reason for the higher pesticidal activity of willow-derived pyrolysis liquid. Temperature-separated slow pyrolysis liquids proved to be suitable to be used as pesticides. Consequently there is possibility to improve the feasibility of thermochemical biomass conversion technologies remarkably by developing the liquid factions to value-added pesticides.

Efficiency of a novel biodegradable pyrolysis liquid‐amended mulch in weed control

“…As we predicted, the efficiency of PLM on weeds increased with increasing PL concentration and the results from the glasshouse, onion field and city park environments were consistent with each other. Hagner et al (2018) recently monitored the effectiveness of various slow pyrolysis liquids (pine, forest residues, wheat, willow) against snails, weeds and aphids and suggested that acids, and in particular the acetic acid, were the main reason for the observed pesticidal effects. In addition to the acetic acid, which has long been applied in plant protection as a herbicide (EPA, 2017; EU, 2017), other PL compounds such as furfural, formic acid, valeric acid, propanoic acid and some phenols were also reported to be effective in pest and weed control (Yatagai et al , 2002; Hensley and Burger, 2006; Hagner et al , 2018).…”

“…Hagner et al (2018) recently monitored the effectiveness of various slow pyrolysis liquids (pine, forest residues, wheat, willow) against snails, weeds and aphids and suggested that acids, and in particular the acetic acid, were the main reason for the observed pesticidal effects. In addition to the acetic acid, which has long been applied in plant protection as a herbicide (EPA, 2017; EU, 2017), other PL compounds such as furfural, formic acid, valeric acid, propanoic acid and some phenols were also reported to be effective in pest and weed control (Yatagai et al , 2002; Hensley and Burger, 2006; Hagner et al , 2018). Hence, although the solid cover formed by the sticky PL and peat fibres likely suppressed weed growth by acting as a mechanical obstacle in our study, the weed‐inhibiting effect of PLM was most likely also based on the PL compounds.…”

“…The overall feasibility, environmental sustainability and industrial usability of thermochemical conversion technologies, like slow pyrolysis, depend on whether all produced fractions can be realistically utilised. Currently, liquid and gaseous products are either partly or fully utilised as energy sources at the production site, but fractionating the liquids into specific compounds (Rasrendra et al, 2011; Žilnik & Jazbinšek, 2012) and using them as pesticides (Hagner et al , 2018) or for animal slurry acidification (Keskinen et al, 2018) have been suggested. The chemical composition of PLs can vary significantly depending on the feedstock material and production conditions and their effectiveness in weed management might therefore differ significantly.…”

“…One promising material for residue‐free weed control is the pyrolysis liquids (Hagner, 2013; Hagner et al , 2018). Pyrolysis liquids are by‐products of slow pyrolysis, where various biomass materials can be converted at elevated temperature sand in an oxygen‐poor atmosphere into fuel gases, chemicals and carbon‐rich products (Fagernäs et al , 2012).…”

“…After drying, the mixture of pyrolysis liquids and fibres forms a biodegradable cover that is impenetrable to weeds, but permeable to moisture. Earlier studies have shown that pyrolysis liquids can be used as nail repellent (Lindqvist et al , 2010; Tiilikkala et al , 2011; Hagner et al , 2018) and as a pesticide against insects, bacteria and fungi (Ibrahim et al , 2013; Hossain et al , 2015), but the efficiency of pyrolysis liquid mulch (PLM) in weed control has not been examined even though the mulching technology was recently patented (Finnish patent no. FI127775 [B], international application WO2018108681 [A1]).…”