H.I. Petersen , H. Deskur , A. Rudra , S.B. Ørberg , D. Krause-Jensen , H. Sanei
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The biochar, hydrocarbon, and CO + CO<sub>2</sub> yields vary due to different chemical composition of the macroalgal species, but the product yield variations are not related to the brown, red, or green macroalgal groups. The total biofuel yield shows an inverse trend with biochar yield. A slower heating rate produces more biochar and higher CO + CO<sub>2</sub> and lower biofuel yields than the combined flash pyrolysis and faster heating rate. The morphotype composition of the biochar was qualitatively examined by reflected light microscopy while carbon stability was assessed by random reflectance (R<sub>o</sub>) measurements. The diverse morphotype compositions observed in biochar formed under similar pyrolysis conditions likely stem from variations in the original algal composition. While some biochar samples show morphologies resembling the original macroalgal structure, porous morphotypes predominantly characterize the biochar samples overall. Despite a maximum pyrolysis production temperature (PT) of 650 °C, the highest mean R<sub>o</sub> value among all biochar samples is 2.91%, corresponding to a carbonization temperature (CT) of 526 °C. This observation is tentatively related to the less lignocellulosic structure of the macroalgae compared to terrigenous biomass. Four biochar samples have their entire R<sub>o</sub> distribution range above the inertinite benchmark (IBR<sub>o</sub>2%) of R<sub>o</sub> = 2% indicating high carbon stability. Conversely, the remaining four biochar samples exhibit R<sub>o</sub> distributions extending below IBR<sub>o</sub>2%, indicating the presence of a carbon fraction with lower long-term stability in soil. The statistically significant inverse relationship observed between the mean R<sub>o</sub> values and the peak hydrocarbon generation temperature (T<sub>max</sub>) can be attributed to the behavior of residual macromolecules within the biochar. When these macromolecules reach peak biofuel generation at a lower temperature, they undergo carbonization over a more extended time interval during pyrolysis. Consequently, this prolonged exposure to the pyrolysis process leads to higher degrees of carbonization, as reflected by higher R<sub>o</sub> values. In conclusion, the findings from pyrolysis and organic petrography reveal: (1) Macroalgae demonstrate potential for biofuel production, although biofuel yields contingent upon both the species of macroalgal and the heating rate employed, and (2) This study documents for the first time that flash+ramp pyrolysis of macroalgae yields biochar suitable for long-term carbon storage. However, both the carbon stability inferred from R<sub>o</sub> frequency distributions and biochar yields show variations across different macroalgal species and heating rate.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6000,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000557/pdfft?md5=0d65373d62f36defcafced7d9787f013&pid=1-s2.0-S0166516224000557-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Pyrolysis of macroalgae: Insight into product yields and biochar morphology and stability\",\"authors\":\"H.I. Petersen , H. Deskur , A. Rudra , S.B. Ørberg , D. Krause-Jensen , H. 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The biochar, hydrocarbon, and CO + CO<sub>2</sub> yields vary due to different chemical composition of the macroalgal species, but the product yield variations are not related to the brown, red, or green macroalgal groups. The total biofuel yield shows an inverse trend with biochar yield. A slower heating rate produces more biochar and higher CO + CO<sub>2</sub> and lower biofuel yields than the combined flash pyrolysis and faster heating rate. The morphotype composition of the biochar was qualitatively examined by reflected light microscopy while carbon stability was assessed by random reflectance (R<sub>o</sub>) measurements. The diverse morphotype compositions observed in biochar formed under similar pyrolysis conditions likely stem from variations in the original algal composition. While some biochar samples show morphologies resembling the original macroalgal structure, porous morphotypes predominantly characterize the biochar samples overall. Despite a maximum pyrolysis production temperature (PT) of 650 °C, the highest mean R<sub>o</sub> value among all biochar samples is 2.91%, corresponding to a carbonization temperature (CT) of 526 °C. This observation is tentatively related to the less lignocellulosic structure of the macroalgae compared to terrigenous biomass. Four biochar samples have their entire R<sub>o</sub> distribution range above the inertinite benchmark (IBR<sub>o</sub>2%) of R<sub>o</sub> = 2% indicating high carbon stability. Conversely, the remaining four biochar samples exhibit R<sub>o</sub> distributions extending below IBR<sub>o</sub>2%, indicating the presence of a carbon fraction with lower long-term stability in soil. The statistically significant inverse relationship observed between the mean R<sub>o</sub> values and the peak hydrocarbon generation temperature (T<sub>max</sub>) can be attributed to the behavior of residual macromolecules within the biochar. 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引用次数: 0
摘要
将生物质残渣热解成生物炭被认为是通过生物碳储存(二氧化碳去除,CDR)减缓气候变化以及用可持续生物燃料替代化石燃料的可行方法。本研究采用闪蒸和斜坡加热热解以及有机岩石学相结合的方法,研究了八种不同组织复杂性的棕色、红色和绿色大型藻类的碳氢化合物(生物燃料)潜力、生物炭稳定性和形态。从大型藻类中提取的生物炭的碳稳定性以前从未使用有机岩石学(反射率测量)进行过评估,也未在地质碳循环的背景下进行过评估。由于大型藻类的化学成分不同,生物炭、碳氢化合物和 CO + CO2 的产量也不同,但产品产量的变化与棕色、红色或绿色大型藻类无关。生物燃料总产量与生物炭产量呈反比趋势。与闪蒸热解和较快的加热速度相比,较慢的加热速度会产生更多的生物炭、更高的 CO + CO2 和更低的生物燃料产量。生物炭的形态组成是通过反射光显微镜进行定性检测的,而碳的稳定性则是通过随机反射率(Ro)测量进行评估的。在类似热解条件下形成的生物炭中观察到的不同形态组成可能源于原始藻类组成的变化。虽然一些生物炭样品显示出与原始大型藻类结构相似的形态,但多孔形态是生物炭样品的主要特征。尽管生物炭的最高热解生产温度(PT)为 650 °C,但所有生物炭样品的最高平均 Ro 值为 2.91%,对应的碳化温度(CT)为 526 °C。这一观察结果可能与大型藻类的木质纤维素结构少于陆生生物质有关。四个生物炭样品的整个 Ro 分布范围都高于 Ro = 2% 的惰性基(IBRo2%),这表明碳的稳定性很高。相反,其余四个生物炭样品的 Ro 分布范围则低于 IBRo2%,表明土壤中存在长期稳定性较低的碳部分。在平均 Ro 值和碳氢化合物生成峰值温度 (Tmax) 之间观察到的统计学意义上的显著反比关系可归因于生物炭中残留大分子的行为。当这些大分子在较低温度下达到生物燃料生成峰值时,它们在热解过程中会在更长的时间间隔内发生碳化。因此,在热解过程中暴露的时间越长,碳化程度越高,Ro 值越高。总之,热解和有机岩石学的研究结果表明:(1) 大型藻类具有生产生物燃料的潜力,但生物燃料的产量取决于大型藻类的种类和所采用的加热速率;(2) 本研究首次证明大型藻类的闪蒸+斜坡热解产生的生物炭适合长期碳储存。然而,从 Ro 频率分布推断出的碳稳定性和生物炭产量在不同的大型藻类和加热速率下都存在差异。
Pyrolysis of macroalgae: Insight into product yields and biochar morphology and stability
Pyrolysis of biomass residues into biochar is seen as a feasible way to mitigate climate change by biological carbon storage (carbon dioxide removal, CDR) and to substitute fossil fuel with sustainable biofuel. This study applies a combination of flash and ramp heating pyrolysis, and organic petrography to investigate the hydrocarbon (biofuel) potential and biochar stability and morphotypes of eight brown, red, and green macroalgal species of different tissue complexity. The carbon stability of biochar derived from macroalgae has not previously been assessed using organic petrography (reflectance measurements) and evaluated in the context of the geological carbon cycle. The biochar, hydrocarbon, and CO + CO2 yields vary due to different chemical composition of the macroalgal species, but the product yield variations are not related to the brown, red, or green macroalgal groups. The total biofuel yield shows an inverse trend with biochar yield. A slower heating rate produces more biochar and higher CO + CO2 and lower biofuel yields than the combined flash pyrolysis and faster heating rate. The morphotype composition of the biochar was qualitatively examined by reflected light microscopy while carbon stability was assessed by random reflectance (Ro) measurements. The diverse morphotype compositions observed in biochar formed under similar pyrolysis conditions likely stem from variations in the original algal composition. While some biochar samples show morphologies resembling the original macroalgal structure, porous morphotypes predominantly characterize the biochar samples overall. Despite a maximum pyrolysis production temperature (PT) of 650 °C, the highest mean Ro value among all biochar samples is 2.91%, corresponding to a carbonization temperature (CT) of 526 °C. This observation is tentatively related to the less lignocellulosic structure of the macroalgae compared to terrigenous biomass. Four biochar samples have their entire Ro distribution range above the inertinite benchmark (IBRo2%) of Ro = 2% indicating high carbon stability. Conversely, the remaining four biochar samples exhibit Ro distributions extending below IBRo2%, indicating the presence of a carbon fraction with lower long-term stability in soil. The statistically significant inverse relationship observed between the mean Ro values and the peak hydrocarbon generation temperature (Tmax) can be attributed to the behavior of residual macromolecules within the biochar. When these macromolecules reach peak biofuel generation at a lower temperature, they undergo carbonization over a more extended time interval during pyrolysis. Consequently, this prolonged exposure to the pyrolysis process leads to higher degrees of carbonization, as reflected by higher Ro values. In conclusion, the findings from pyrolysis and organic petrography reveal: (1) Macroalgae demonstrate potential for biofuel production, although biofuel yields contingent upon both the species of macroalgal and the heating rate employed, and (2) This study documents for the first time that flash+ramp pyrolysis of macroalgae yields biochar suitable for long-term carbon storage. However, both the carbon stability inferred from Ro frequency distributions and biochar yields show variations across different macroalgal species and heating rate.
期刊介绍:
The International Journal of Coal Geology deals with fundamental and applied aspects of the geology and petrology of coal, oil/gas source rocks and shale gas resources. The journal aims to advance the exploration, exploitation and utilization of these resources, and to stimulate environmental awareness as well as advancement of engineering for effective resource management.