• Energy Research

Bioenergy is considered a sustainable substitute to fossil-fuel resources and the development of a prudent combination of renewable and innovative conversion technologies are essential for the valorization and effective conversion of biowaste to value-added commodities. Here, a negative pressure-induced carbonization process was proposed for the valorization of lignin-enriched biowaste precursor to bio-oil and environmental materials (biochar) at various temperatures. The high heating values (HHV) of the as-prepared biochars from the lignin enriched precursor under negative pressure (low-medium vacuum) were within 25.9-31.5 MJ/kg, which matched satisfactorily to the commercial charcoal. Whereas, the bio-oils produced from the lignin enriched precursor under vacuum conditions was a blend of complex aromatic and straight-chain hydro-carbons, including aldehyde, ketone, phenol, and furans, exhibiting ability as potential heating-oil with HHV within 21.2-28.2 MJ/kg. Moreover, the biochars produced under vacuum environments at higher temperature showed greater stability (22.5-35.9%) than those produced under N2 atmosphere.

Abstract Biomass, as a renewable and sustainable energy resource, can be converted into environmentally friendly and practically valuable biofuels and chemical materials via pyrolysis. However, the process optimization and pyrolysis efficiency are restricted by the limited perception of the complicated mechanisms and kinetics for biomass pyrolysis. Here, to establish an in-depth mechanism model for biomass pyrolysis, we presented a novel investigation for the thermal evolutions and pyrolysis kinetics of the functional groups in peanut shell matrix by using in-situ Fourier transform infrared spectrometry (in-situ FTIR) and thermogravimetric analysis-Fourier transform infrared spectrometry-mass spectrometry (TG-FTIR-MS). The in-situ FTIR spectrum deconvolution for the solid matrix was innovatively introduced to identify and quantify the real-time evolution and thermal dynamics of the functional groups during peanut shell pyrolysis. The result for the first time proposed that the pyrolysis mechanisms of total OH at 20–380 °C, aliphatic C-Hn groups at 20–500 °C, C O groups at 260–500 °C, and C–O groups at 300–500 °C were dominant by diffusion and order-based chemical reactions. The TG-FTIR-MS analysis was conducted for the online monitoring of the released volatiles and gases, the amounts of which were in the sequence of C O > CO2 > aliphatic C–O-(H) > C–O-(C) in esters > aromatics > H2O > phenolic hydroxyl > aliphatic hydrocarbons > CO. The study established a novel methodology to evaluate the biomass pyrolysis mechanisms at the molecular level, which provided valuable information for developing advanced pyrolysis techniques on a large scale for sustainable ecosystem.

Abstract In terms of net intensification in the greenhouse effect ie., rise of global temperature which has triggered melting of glacier thus increasing sea level and acidification of sea, carbon dioxide alone contributes approximately three-fourth of the net greenhouse radiative forcing by man-made (anthropogenic) greenhouse gases emissions. Carbon dioxide capture and storage (CCS) technology; a promising strategy for capturing of carbon dioxide from point sources before its release to atmosphere by using various sorbents is gaining global interest. In this study, the established carbon capture technologies with methods of carbon dioxide separation along there pros and cons are discussed. Carbon-based adsorbents are considered as the most versatile adsorbents for carbon dioxide due to their extraordinary physical and chemical properties. In this manuscript, recent developments on carbonaceous adsorbents (biochar, activated carbons, and graphene-based adsorbents) and their role in carbon dioxide capture during different combustion processes and conditions have been comprehensively focused.

Abstract Ragweed (Ambrosia artemisiifolia L.), a metal-accumulator invasive species, was pyrolyzed under a range of pyrolytic conditions to investigate their influence on immobilization and environmental safety of potentially toxic elements (PTEs) in the produced biochar. Conditions tested included temperature, retention time, heating rate, gas flow rate and particle size. Temperature and particle size had pronounced effects on product yields and physico-chemical characteristics of the produced biochar. All PTEs were enriched in the biochar, and the effect was more pronounced with higher temperature over 500 °C. However, fractionation of PTEs in biochar by following the sequential extraction process indicates that the mobile (bioavailable) fraction of most of the PTEs was transformed into more stabilized (residual) form (P

The combustion characteristics, kinetic analysis and selenium retention-emission behavior during co-combustion of high ash coal (HAC) with pine wood (PW) biomass and torrefied pine wood (TPW) were investigated through a combination of thermogravimetric analysis (TGA) and laboratory-based circulating fluidized bed combustion experiment. Improved ignition behavior and thermal reactivity of HAC were observed through the addition of a suitable proportion of biomass and torrefied. During combustion of blends, higher values of relative enrichment factors in fly ash revealed the maximum content of condensing volatile selenium on fly ash particles, and depleted level in bottom ash. Selenium emission in blends decreased by the increasing ratio of both PW and TPW. Higher reductions in the total Se volatilization were found for HAC/TPW than individual HAC sample, recommending that TPW have the best potential of selenium retention. The interaction amongst selenium and fly ash particles may cause the retention of selenium.

AbstractThe extreme amount of greenhouse gases (GHGs) being released into the atmosphere has proved to be a globally challenging phenomenon that leads to changes in the climate and global warming. The amount of GHGs in the atmosphere has escalated immensely, with a substantial growth of 5.8% in 2010; a similar increase was observed in Pakistan as well. In Pakistan, carbon dioxide (CO2) emissions stand at 54% of total GHG emissions whereas methane, nitrous oxide, carbon monoxide and volatile organic carbon contribute to emissions at 36%, 9%, 0.75% and 0.3%, respectively. One of the key reasons for climatic changes is GHG emission generation from human interventions and activities related to transportation, urban development, industrialization, energy sources, farming and agriculture, waste's improper management, land use and forestry. In 2011, Pakistan's entire GHG emissions were a whopping 347 Mt of CO2‐eq, and by 2050, they are estimated to reach 4621 Mt CO2‐eq. This review evaluates and assesses GHG emissions generating from various sectors in Pakistan, in a socio‐scientific prospect that is caused by human activities and interventions in different economic sectors in Pakistan, endangering the environment across the country. Additionally, the review examines the current level of GHG emissions while accounting for China–Pakistan Economic Corridor–based emissions, abatement strategies including development of a state‐of‐the‐art technique for carbon capture and storage/utilization technologies in Pakistan. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Rapid development in nanotechnology and incorporation of silver nanoparticles (AgNPs) in wide range of consumer products causing the considerable release of these NPs in the environment, leading concerns for ecosystem safety and plant health. In this study, rice (Oryza sativa) was exposed to AgNPs (0, 100, 200, 500 and 1000 mg L-1) in biochar amended (2 %w/v) and un-amended systems. Exposure of plants to AgNPs alone reduced the root and shoot length, biomass production, chlorophyll contents, photosynthesis related physiological parameters as well as macro-and micronutrients in a dose dependent manner. However, in case of biochar amendment, physiological parameters i.e., net photosynthesis rate, maximum photosynthesis rate, CO2 assimilation, dark respiration and stomatal conductance reduced only 16, 6, 7, 3 and 8%, respectively under AgNPs exposure at 1000 mg L-1 dose. Meanwhile, biochar at all exposure level of AgNPs decreased the bioaccumulation of Ag in rice root and shoot tissues, thus alleviated the phyto-toxic effects of NPs on plant growth. Moreover, results showed that biochar reduced the bioavailability of AgNPs by surface complexation, suppressing dissolution and release of toxic Ag+ ions in the growth medium. The presence of biochar at least decreased 2-fold tissue contents of Ag even at highest AgNPs (1000 mg L-1) concentration. These finding suggested that biochar derived from waste biomass resources can be used effectively to prevent the bioaccumulation and subsequent trophic level transfer of emerging Ag nano-pollutant in the environment.

Abstract Thermochemically converted biochar is considered as one of the promising alternative solid-fuel due to its high carbon contents of up to 80%, and has great potential to produce environmentally-friendly green-energy by improved fuel properties and emission-reduction of potentially toxic elements (PTEs). In this study, the biochar fuels, produced from peanut shell (PS) and wheat straw (WS) at 300, 500 and 700 °C, alone and blended with coal at mass ratio of 20% and 50% were systematically investigated for combustion characteristics and their potential to reduce the emission of PTEs including As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, Ni, Pb, Sb, Sn, V and Zn in relation to partitioning, retention and volatilization in the co-combustion systems, using a variety of experimental techniques. Results indicated that the biochar-coal blended fuels in equal proportion showed steady state combustion over broad temperature range resulting increased the combustion efficiency and improved the thermal characteristics in comparison to coal and/or biomass-coal fuels. In addition, soot yield, CO emission and un-burned carbon in fly ash reduced significantly in biochar-blended fuels. However, CO2 emission from biochar-coal co-combustion was comparable to coal and/or biomass-coal fuels. Moreover, the present study illustrated that the volatilization potential of PTEs during combustion of biochar and their blends with coal decreased considerably up to 21% compared to that of coal, and enrichment of these contaminants occurred in the bottom and fly ashes ranged from 15.38–65% and 24.54–74.29%, respectively. Slagging and fouling problems were still found with biochar-coal co-combustion due to the higher inorganic fraction of biochar, which were overcome with the hydrothermal washing of fuels. Thus, it can be concluded that biochar-coal co-combustion is a suitable option for its use in existing coal-fired energy generation system to achieve the sustainable clean-green energy and reduction of gaseous PTEs emission.

Abstract One of the key environmental limitations in coal usage is selenium emission whose removal is focused in this study. We employed hydrothermal treatment to remove Se element and upgrade low rank Huainan coal at 200–300 °C. Pyrolysis temperature given during coal treatment was evaluated to simulate coal transformation into high-rank industrial grade by emphasizing O/C ratio, removal of oxygen functional groups and moisture and chemical structure stability. Following hydrothermal treatment, different characterization techniques including XPS, FTIR, XRD and Raman spectroscopy were used to determine the chemical structure of coal. Findings revealed that hydrothermal treatment process has an important influence on the crystalline structures of low rank coals. The results of XRD and Raman spectroscopy analysis demonstrated much graphitized and aromatic microcrystalline structure. The chemical structure developed was orderly, stable and dense. Selenium XPS spectra comprising of 3D peaks has confirmed several oxidation states including selenide, selenates and oxide species. The removal proportion of Se was significant and increased up to 50.7% with increased HTT temperature (300 °C). This study provides some unique findings pertaining to solubility of sub-critical water and rate of change in pyrolysis temperature as determinant factors in the removal of Se. Our simulation model further concludes that transformation of low rank coal into high rank is a function of temperature treatment coupled with optimization of fixed carbon. We infer that hydrothermal treatment derived coal possesses sufficient lucid attributes to be considered as environmentally safe fuel.