• Energy Research

Catalytic fast pyrolysis of biomass offers an opportunity for upgrading of pyrolysis bio-oils using mono- and bimetallic-supported catalysts, which have been demonstrated to improve the bio-oil qua...

Abstract Increasing global energy demand and concerns of carbon emissions have driven the utilisation of renewable sources such as biomass. Biomass pyrolysis in the presence of catalyst, i.e., biomass catalytic pyrolysis (CP), is one of the most efficient routes for generating renewable hydrocarbon fuels or commodity chemicals. Most previous review papers on biomass CP focused on the summary of catalyst classification, properties and performance based on product yields and oil quality. Information on biomass CP process especially effects of different reaction atmospheres has not been reviewed or discussed in sufficient detail. This paper aims to provide a review and insights of the essential process factors and system structure of the lignocellulosic biomass CP with emphasis on process performance indexes such as bio-oil’s effective hydrogen to carbon ratio, deoxygenation degree, carbon efficiency and energy efficiency. The paper sections are organised in order of biomass CP catalysts, biomasss CP assessment, modification of essential process factors (e.g., biomass pre-treatment, co-feeding with other materials, atmosphere and temperature) and variations in the system structure (e.g., heat source alternatives, staged catalysis and process integration). Variations in process factors and system structure can possibly tailor the products and improve the economic attraction. A number of questions about biomass CP are still unclear. The current status, challenges and future research directions of biomass CP are also discussed in the paper. The comprehensive review and insights of the biomass CP process in this work will provide reference for the research and industrialisation of biomass CP for renewable fuel production.

Abstract Pyrolysis is one of the significant technologies that can utilize lignocellulose biomass to produce different bioenergy fuels, such as bio-oil, pyrolytic gases and bio-char. The application of pyrolysis has been extensively studied to produce bio-oil, which is foreseen as the potential transportation fuel in the near future. However, the presence of oxygenated compounds, such as phenols and alcohols in bio-oil makes it highly acidic and unstable for a suitable transportation fuel. These oxygenated compounds can be converted to refinable hydrocarbons by using different catalysts. Therefore, this study aimed to prepare a catalyst that is Cu10%-zeolite and investigated its deoxygenation activity for bio-oil produced from pyrolysis of pine wood sawdust. The catalyst was prepared by a wet-impregnation method. Subsequently, the catalyst was characterized by X-ray diffraction and transmission electron microscopy. Furthermore, the catalyst was applied for in-situ (catalyst: biomass=5) and ex-situ catalytic pyrolysis (catalyst: biomass=3) and the results were compared with those from sole zeolite support. The pyrolysis process was carried out at a heating rate of 100 °C/min to a final temperature of 700 °C and the composition of bio-oil was examined by gas chromatography-mass spectroscopy. The results revealed that Cu-zeolite showed significant deoxygenation activity for bio-oil as compared to zeolite or without any catalyst. Evidently, Cu-zeolite after in-situ pyrolysis produced bio-oil with 20.9% aromatic hydrocarbons and 7.5% aliphatic hydrocarbons, which were approximately 80% and several times higher than with only zeolite, respectively. Meanwhile the concentration of alcohols was reduced from 47.5% to 5%. On the other hand, bio-oil produced from ex-situ catalytic pyrolysis was enriched with 41.6% aromatic hydrocarbons while only 1% alcohols were present in bio-oil. This promising deoxygenation activity can be ascribed to Cu-zeolite’s catalytic activity that converted phenol and alcohols to refinable hydrocarbons via various reactions, such as dehydration, decarboxylation and decarbonylation.

The metal(loid)-enriched Avicennia marina biomass obtained from phytoremediation was impregnated with two ferric salts (FeCl3 and Fe(NO3)3) prior to pyrolysis at 300-700 °C, aiming to study the influence on pyrolytic product properties and heavy metal(loid) deportment. Results showed that the impregnated ferric salts increased the fixed carbon content of biochars, hydrocarbon fractions in bio-oils, and the evolution of CO and H2 in gases. Cd in biomass could be effectively removed from the biomass by FeCl3 impregnation. During pyrolysis, the ferric salts enhanced the elemental recovery of As, Cr, Ni and Pb in the biochars and decreased their distribution in gases. Notably, the ferric salt pre-treatment inhibited the mobility and bio-availability of most elements in the biochars. This study indicated that ferric salt impregnation catalysed the pyrolysis process of metal(loid) contaminated biomass, enabled the operation temperature at 500-700 °C with minimal environmental risks, providing a safe and value-added way to the phytoremediation-pyrolysis scheme.

High-tech protected cropping holds great potential to improve global food security, but high cooling energy costs in warm climates pose difficulties in propagating the industry. Emerging technologies, such as diffuse glasses fitted with photoselective thin films, have interactions with crops and other cooling technologies which are not well-characterized for warm-climate glasshouses. A light-blocking film (LBF) was chosen as a high-tech, climate-controlled greenhouse cover permitting transmission of 85% of photosynthetically-active light and blocking heat-generating radiation. Two consecutive 7-month trials of two capsicum crops were grown under warm climate conditions partially impacted by bushfire smoke, with 2 cultivars (Gina and O06614) in the first trial, and 2 cultivars (Gina and Kathia) in the second trial. Capsicum fruit yield decreased by 3% in Gina and increased by 3% in O06614 for the first trial, and decreased by 13% in Gina, 26% in Kathia for the second trial. Cooling energy use increased by 11% and 12% for both capsicum crops in AE and SE respectively, with small but insignificant decreases in fertigation demand (2%–5%). Cooling potential was significantly different from material specifications, with indications that convection from LBF interfaces was responsible for higher heat loads. LBF and similar absorptive glasses may still be beneficial for reducing nutrient, water, and energy use in warm climate glasshouses. However, yield is cultivar-dependent and may decrease with below-optimal crop lighting, whereas energy savings are more dependent on LBF orientation and building geometry than outside climate.

AbstractVegetation has successfully been used for cleaning up metal(loid) polluted water bodies and lands through extracting and accumulating of contaminants in their aboveground biomass (phytoextraction). As this remediation technique is approaching extensive demonstration scale application and potential commercialisation, research efforts have been investigating new ways to achieve valorization of its by‐products, the heavy‐metal‐enriched biomass (HMEB). Biomass pyrolysis as an energy conversion technique represents a key step to numerous valorization options of HMEB. During the pyrolysis of HMEB, understanding the thermal decomposition pathways, and the migration and transformation of metal(loid)s are critical for the production of clean, safe and value‐added end‐products. This work performs a state‐of‐the‐art review of the studies conducted on phytoextraction and biomass pyrolysis of HMEB with emphasis on the properties of pyrolysis products as well as the behavior of heavy metal(loid)s during pyrolysis in relation to HMEB feedstock properties and the variables of the process.

The production of tunable syngas from biomass will further establish the role of biomass-derived syngas as a versatile platform for liquid fuels and value-added chemical synthesis. This study introduced steam, Ni–CaO catalyst, and biochar into a proposed two-stage sorption-enhanced catalytical thermochemical conversion process, aiming to obtain the tunable syngas through the in-situ stepwise generation of high purity H2 and CO. The presence of steam and Ni–CaO catalyst shows unprecedented performance in enhancing the H2 generation due to the promotional tar steam reforming/cracking and water-gas shift reactions at the first stage, and the control experiments indicate that the steam performs a higher selectivity to H2 than the Ni–CaO catalyst. The introduction of biochar with a supplementary carbon source, remarkably promotes the CO generation at the second stage, which could be further pronounced by the addition of Ni–CaO catalyst. A synergistic effect of steam, Ni–CaO catalyst, and biochar contributes to a significant enhancement in H2 and CO generation with an inherently separated generation of H2 (88.2 ± 2.3 vol% of purity) and CO (55.6 ± 1.3 vol% of purity). And the combined use of steam, Ni–CaO catalyst, and biochar could lead to a superior syngas quality with high LHVsyngas and energy recovery efficiency.

Abstract Vegetation has successfully been used for phytoremediation of heavy metal(loid) contaminated soils. Previous works found that the metal(loid)-enriched biomass can be converted into biofuels through pyrolysis. However, the potential emission of metal(loid)s at higher pyrolysis temperatures, the leaching potential of minerals in chars, and the quality of the products needs further consideration. In this work, the metal(loid)-enriched biomass was engineered by pre-mixing with magnesium carbonate to study the effect on pyrolytic product properties and metal(loid) deportment. Heavy metal contaminated mangrove grown in a land contaminated with a lead–zinc smelter slags was used as the biomass. The biomass and magnesium carbonate mixture as the feedstock was subjected to pyrolysis at temperatures from 300 to 900 °C under the heating rate of 10 °C/min. Results showed that the feedstock mainly decomposed at temperatures between 176 and 575 °C. Amongst the 10 studied metal(loid)s in this work, most elements exhibited more than 70% of elemental recovery in chars at pyrolysis temperatures up to 700 °C. Pyrolysis also enhanced heavy metal stability in chars produced at temperatures above 300 °C. This study indicated that co-pyrolysis of heavy metal contaminated biomass with magnesium carbonate enabled the pyrolysis temperature up to 700 °C with minimal environmental risks, providing a safe and value-added way of phytoremediation residual management.