Polycyclic Aromatic Hydrocarbons in Birch Wood Slow Pyrolysis Products

Fagernäs, Leena; Kuoppala, Eeva; Simell, Pekka

doi:10.1021/ef3010515

Cited by 45 publications

(44 citation statements)

References 16 publications

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“…Since PAHs are reported to be mostly formed at the gas-solid interphase [6,8,10,13,33], most PAHs created are easily vaporised at typical pyrolysis temperatures (>99% end up in pyrolysis liquids / gases) [14,38]. Naturally, increasing pyrolysis temperature leads to higher PAH vaporisation from pyrolysis solids which counteracts the increasing amount of PAH yield at higher temperatures.…”

Section: Effect Of Highest Treatment Temperature (Htt) On Pahs In Biomentioning

confidence: 99%

“…However, a plausible explanation of this unit-specific effect, is that it is caused by the pyrolysis unit design and operation, resulting in distribution of temperatures that allowed cooling of volatiles at the discharge end of the unit. Due to the pyrolysis unit design, where pyrolysis vapours (containing >99% of the produced PAHs [14,38]) travel concurrently through the pyrolysis chamber and into a discharge chamber where biochar is separated, extensive contact between biochar and vapours is possible. Therefore, if at any point the reactor or material temperature drops below dew point of the tars, including PAHs in the pyrolysis vapours, these would condense onto the biochar.…”

Section: Effect Of Highest Treatment Temperature (Htt) On Pahs In Biomentioning

confidence: 99%

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Strategies for producing biochars with minimum PAH contamination

Buss¹,

Graham²,

MacKinnon

et al. 2016

Journal of Analytical and Applied Pyrolysis

108

101

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With the aim to develop initial recommendations for production of biochars with minimal contamination with polycyclic aromatic hydrocarbons (PAHs), we analysed a systematic set of 46 biochars produced under highly controlled pyrolysis conditions. The effects of the highest treatment temperature (HTT), residence time, carrier gas flow and typical feedstocks (wheat / oilseed rape straw pellets (WSP), softwood pellets (SWP)) on 16 US EPA PAH concentration in biochar were investigated. Overall, the PAH concentrations ranged between 1.2 and 100 mg kg -1 . On average, straw-derived biochar contained 5.8 times higher PAH concentrations than softwood-derived biochar. In a batch pyrolysis reactor, increasing carrier gas flow significantly decreased PAH concentrations in biochar; in case of straw, the concentrations dropped from 43.1 mg kg -1 in the absence of carrier gas to 3.5 mg kg -1 with a carrier gas flow of 0.67 L min -1 ; for woody biomass PAHs concentrations declined from 7.4 mg kg -1 to 1.5 mg kg -1 with the same change of carrier gas flow. In the temperature range of 350-650°C the HTT did not have any significant effect on PAH content in biochars, irrespective of feedstock type, however, in biochars produced at 750°C the PAH concentrations were significantly higher. After detailed investigation it was deduced that this intensification in PAH contamination at high temperatures was most likely down to the specifics of the unit design of the continuous pyrolysis reactor used. Overall, it was concluded that besides PAH formation, vaporisation is determining the PAH concentration in biochar. The fact that both of these mechanisms intensify with pyrolysis temperature (one increasing and the other one decreasing the PAH concentration in biochar) could explain why no consistent trend in PAH content in biochar with temperature has been found in the literature. AbbreviationsHTT, highest treatment temperature; I.D., inner diameter

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Section: Effect Of Highest Treatment Temperature (Htt) On Pahs In Biomentioning

confidence: 99%

Section: Effect Of Highest Treatment Temperature (Htt) On Pahs In Biomentioning

confidence: 99%

Strategies for producing biochars with minimum PAH contamination

Buss¹,

Graham²,

MacKinnon

et al. 2016

Journal of Analytical and Applied Pyrolysis

108

101

View full text Add to dashboard Cite

show abstract

“…Typically, the pH of wood biochar at produced at midpyrolysis temperatures is between 6.7-7.9 (Calvelo Pereira et al, 2011;Mukome et al, 2013;Ronsse et al, 2013), but in one instance, a pine biochar (<450°C, fast pyrolysis) was stated to have a pH of only 3.9 (Smith et al, 2013). The acidic nature of the re-condensed pyrolysis liquids are the reason for the low pH of contaminated biochars (Fagernas et al, 2012), which originated from the degradation of cellulose, hemicellulose and lignin and the formation of acetic acid and other organic acids during pyrolysis (Fagernas et al, 2012;Spokas et al, 2011).…”

Section: Characterisation Of Biocharsmentioning

confidence: 99%

Mobile organic compounds in biochar – A potential source of contamination – Phytotoxic effects on cress seed (Lepidium sativum) germination

Buss

Mašek

2014

Journal of Environmental Management

148

142

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Biochar can be contaminated during pyrolysis by re-condensation of pyrolysis vapours. In this study two biochar samples contaminated by pyrolysis liquids and gases to a high degree, resulting in high volatile organic compound (high-VOC) content, were investigated and compared to a biochar with low volatile organic compound (low-VOC) content. All biochar samples were produced from the same feedstock (softwood pellets) under the same conditions (550 °C, 20 min mean residence time). In experiments where only gaseous compounds could access germinating cress seeds (Lepidium sativum), application amounts ranging from 1 to 30 g of high-VOC biochar led to total inhibition of cress seed germination, while exposure to less than 1 g resulted in only partial reduction. Furthermore, leachates from biochar/sand mixtures (1, 2, 5 wt.% of biochar) induced heavy toxicity to germination and showed that percolating water could dissolve toxic compounds easily. Low-VOC biochar didn't exhibit any toxic effects in either germination test. Toxicity mitigation via blending of a high-VOC biochar with a low-VOC biochar increased germination rate significantly. These results indicate re-condensation of VOCs during pyrolysis can result in biochar containing highly mobile, phytotoxic compounds. However, it remains unclear, which specific compounds are responsible for this toxicity and how significant re-condensation in different pyrolysis units might be.

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“…A related study discussed the presence of polyaromatic hydrocarbons in birch wood slow pyrolysis oil. 31 Another study performed a chemical and toxicological GC-MS screening of three slow pyrolysis oil samples from different feedstocks. A total number of 60 chemical structures were identified, including phenols and polyaromatic hydrocarbons, many of 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 which can be associated with both acute and chronic hazardous health effects.…”

Section: Introductionmentioning

confidence: 99%

Compositional Characterization of Phase-Separated Pine Wood Slow Pyrolysis Oil by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

et al. 2015

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Chemical composition of slow pyrolysis oil made from unbarked Scots pine (Pinus sylvestris) was characterized by negative-ion electrospray ionization Fourier transform ion cyclotron resonance (ESI FT-ICR) mass spectrometry and various bulk analyses. The wood pieces were heated stepwise in a batch pyrolysis reactor to the target temperature of 320 °C. The resulting pyrolysis oil spontaneously separated into aqueous and oily phases. The water content of the aqueous phase was as high as 60.4 wt-%, whereas for the oily phase it was only 8.1 wt-%. The bulk O/C-ratio (on a dry basis) was more than twice as high for the aqueous phase as compared to the oily phase (0.61 vs 0.29), suggesting different chemistry between the two phases. Based on pH and total acid number measurements, the aqueous phase was more acidic than the oily phase. The ESI FT-ICR technique was used to characterize pyrolysis oils' heavier, non-volatile and thermally labile species. The total amounts of the identified chemical formulae were ~540 and ~630 for the aqueous and oily phases, respectively. The majority of the detected compounds were oxygen-containing species, representing heteroatom classes O 2 -O 14 . The O 9 -O 14 class compounds were present only in the aqueous phase.The O 2 -O 4 compounds comprised of different acids, including resin acids and several types of fatty acids, such as hydroxy fatty acids and diacids, which were concentrated in the oily phase. However, saturated fatty acids were more dominant in the aqueous phase possibly due to their increased solubility through micelle formation in a more aqueous environment. Anhydrosugars and other high oxygen-containing compounds were present only in the aqueous phase. Both phases also contained condensed aromatic compounds (pyrolytic lignin), representing heteroatom classes O 3 -O 8 .

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Polycyclic Aromatic Hydrocarbons in Birch Wood Slow Pyrolysis Products

Cited by 45 publications

References 16 publications

Strategies for producing biochars with minimum PAH contamination

Strategies for producing biochars with minimum PAH contamination

Mobile organic compounds in biochar – A potential source of contamination – Phytotoxic effects on cress seed (Lepidium sativum) germination

Compositional Characterization of Phase-Separated Pine Wood Slow Pyrolysis Oil by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

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