Research Article Cite This: ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
pubs.acs.org/journal/ascecg
Evaluation of Biobased Lighter Fluids Edit Cséfalvay* Department of Energy Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3, Budapest H-1111, Hungary S Supporting Information *
ABSTRACT: γ-Valerolactone that can easily be obtained from renewable resources or by valorization of biomass wastes, as proposed was a sustainable liquid by István T. Horváth. Because it was suggested as igniting liquid and lighter fluid, ignition and combustion tests on charcoal briquettes, THC emission, and sustainability calculations were performed. Besides γ-valerolactone, ethyl-levulinate, γ-valerolactone (90% v/v)−ethanol (10% v/v) mixture, and ethyl-levulinate (90% v/v)−ethanol (10% v/ v) mixture were tested as biobased lighter fluid candidates. It was revealed that the addition of a small amount of ethanol improved the ignition and combustion properties, helped to ignite the lighter fluids, increased volatility, and shifted the combustion to more complete state; moreover, it lowered the THC emission compared to those of pure compounds. On the basis of the charcoal combustion tests, ethyl-levulinate (90% v/ v)−ethanol (10% v/v) mixtures provided the most attractive results. Considering sustainability calculations, all biobased lighter fluids provided lower ethanol equivalent values than those of the commercial hydrocarbon-based lighter fluids; in addition, γvalerolactone possessed the lowest ethanol equivalent, corn equivalent, and land equivalent values of the biobased fluids, justifying Horváth’s suggestion. KEYWORDS: Biobased lighter fluids, γ-Valerolactone, Ethyl-levulinate, THC emission, Flame properties, Ethanol equivalent
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INTRODUCTION Biomass has a key role and a strategic position in sustainable carbon atom management and therefore sustainable production of carbon-based consumer end-products. Efforts have been made to replace conventional fossil-based raw materials with renewable ones, and some of them are proven to be industrially viable.1−3 However, volume has to be considered as a crucial factor in commercialization of biomass-based chemical production technologies.4 Comparing the consumptions of lighter fluids (LFs) with commodity chemicals, LFs are consumed only on a kiloton scale, while ethylene as the main representative of petrochemical industry is used on a million ton scale. Recent data about barbecue manufacturing including hydrocarbon-based LFs that are dominantly available on the market was published in 2016; however, no recent consumption data are available for the United States.5 The European Chemicals Agency (ECHA) published an assessment of possible restrictions on lamp oils and grill LFs, from which the consumption of the latter in Norway and Finland, respectively, were reported as follows: 1125−1478 t/yr and 234−373 t/yr.6 These data clearly indicate that charcoal LFs represent a small volume against commodity chemicals. Consequently, the production of LFs based on biomass are proposed as a viable and even environmental friendly alternative. Charcoal materials, such as charcoal briquette, are commonly used for cooking. Because conventional charcoal briquettes are © XXXX American Chemical Society
difficult to ignite and burn slowly or stop burning after they appear have been ignited, LFs have been used to facilitate ignition and burning. To enhance the combustion of wood, coal, or charcoal,7 LFs are distributed over their surface evenly, ignited and the heat is transferred into the solid to initiate the combustion. After the LF is burnt, the remaining solid fuel is suitable for cooking. Formerly, LFs were made from vegetable oils or lard, but nowadays, they typically represent a flammable hydrocarbon mixture originating from crude oil. Hydrocarbonbased LFs are typically mixtures of C10−C13 alkanes and alkenes. Traces of volatile C5 and C6 compounds are also usually utilized as additives, because they facilitate fast ignition. Solid igniters are also commercially available, which are typically hydrocarbon-impregnated materials; paraffin wax cubes and alcohol-based gels can also be utilized for this purposes. Electric charcoal starter, chimney starter, or Looftlighter is also used on charcoal to get fire.8 Focusing on LFs, the ease of ignition could be referred to the flammability of compounds, which corresponds to their volatility. However, volatile organic compounds (VOC) are known to contribute to the ozone formation and concomitant smog formation; therefore, VOC emission of LFs raised the attention of environmental agencies. Per procuration of U.S. Environmental Received: February 2, 2018 Revised: May 13, 2018
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DOI: 10.1021/acssuschemeng.8b00546 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
Research Article
ACS Sustainable Chemistry & Engineering Table 1. Composition of Biobased Lighter Fluids biomass-derived compounds
year published
water content
additives
0.5−90 wt % terpene, 0.5−98.5 wt % short-chain alcohol
0.5−60 wt %
0.05−10 wt % surfactant, 0.1−10 wt % thickening agent
0.5−90 wt % terpene or terpenoid oil, 0.5−98.5 wt % short-chain alcohol GVL 50−100 wt %, ethanol 0−50 wt % 70−50 wt % n-butanol, 30−50 wt % biodiesela GVL 90% v/v, ethanol 10% v/v
0.5−60 wt %
0.5−10 wt % thickening agent
2009
no no no
no no no
2009 2014, 2015 2015
a
2005
ref 28 29 17 13,14 24
Long-chain alkyl esters produced by transesterification of vegetable oil or animal fat (tallow).
definitive but acceptable smell, so it can be easily recognized and provide a pleasant odor during its use. The same research group compared the relative VOC emissions of GVL, GVL− ethanol, and a hydrocarbon mixture and revealed that 10% v/v ethanol added to GVL positively affects the emission, while pure GVL resulted in a similar VOC emission as that of a hydrocarbon mixture.24 Ethyl-levulinate (EL) can be produced either from biobased levulinic acid via esterification with ethanol or directly from lignocellulosic biomass.25,26 Because it was successfully tested as diesel blend component,27 it could also be proposed as LF or LF component. Recently patented biobased LFs are summarized in Table 1. Volatility of LF enhances fast ignition controversially causing in increased emission. Several possibilities exists aiming to reduce emission by (i) raising the flash point of volatile organic solvents by addition of given extent of a combination of two or more terpineols;30−33 (ii) replacement of hydrocarbons with green solvents;30 (iii) combination of both (i) and (ii);34,35 and (iv) modification of LF composition and use of biomass-based liquids.13,14,17 This study is focused on approach (iv). Herein, the detailed investigations of biomass-based lighter fluids are presented. My aims were to test biomass-based lighter fluid candidates and their mixtures with ethanol under real “barbecue” conditions, use a representative soaking time, compare their combustion characteristics after evenly distribution on a charcoal briquette pile, measure absolute concentrations continuously (1 s interval flue-gas sampling) during combustions (since relative concentrations have been demonstrated in a previous study), differentiate the emissions of lighter fluid and charcoal origin, and compare the lighter fluids’ emission related to total hydrocarbon. We intend to demonstrate the positive effect of ethanol blends on the total emission. Finally, a comparison of tested charcoal lighter fluids from sustainability point of view is addressed.
Protection Agency (EPA), Campbell and Stockton compiled a report focusing on VOC emissions from charcoal LFs. They lined up different methods used for emission estimations,9 which resulted in a wide range of VOC emission estimates (220−6300 t) caused by evaporation. However, the best estimate of evaporative emission was 1000 t/yr assuming 5 min soaking time before ignition. Considering a combined VOC emission from evaporation and combustion, 13 150−15 600 t of VOC/yr was estimated.9 The excess use of petroleum-based LFs can have effects on air quality as well, for example, scenting the surrounding air with unwanted odors. Flammability and volatility are key properties of a LF, and their high values are desired for a successful ignition. Odor can act as an unwanted side effect. To avoid unpleasant odors, scenting LF with liquid smoke flavor compounds at a concentration of 0.5−5 wt % was proposed.10 As a scented LF, the base mixture of methyl-laurate, methylstearate, and ethyl alcohol was mixed with a fragrance of apple wood, mesquite, cilantro, herbal, and/or citrus blends. By increasing the flash point of the proposed scented LF to about 93 °C, the VOC emission is supposed to decrease, and the unwanted odor could be eliminated by other fragrances.11 Aiming biodegradable and easily disposable LF that burn with a pleasant aroma, Stephanos proposed a novel LF. It comprises terpene or terpenoid oil as a main component as well as shortchain alcohol(s) (C1−C3) that can be partially replaced by aliphatic hydrocarbon, surfactants, and thickening agents dissolved in water as minor components. Testing mixtures having different ratios of ingredients revealed that a mixture of cold-pressed orange oil (∼30 wt %), methanol (∼40 wt %), surfactant (∼0.1 wt %), and thickening agent (∼30 wt %) showed the lowest emission fulfilling the requirements set by South Coast Air Quality Management District (SCAQMD) (limit is 0.02 lb VOC/start = 9.072 g CH2/start).12 Biodiesel was also suggested as a new LF candidate. Because it consists of long-chain alkyl-esters, which are difficult to ignite, short-chain (C1−C5) alcohols are added to facilitate ignition.13 It was revealed that a 70 wt % n-butanol−30 wt % soybean oil-based biodiesel mixture could provide much lower emission14 than the limit set by SCAQMD.12 In a series of biomass-based surrogates, Horváth15 and coworkers proposed γ-valerolactone (GVL) as sustainable liquid. It is renewable and has advantageous physical and chemical properties such as high boiling and flash points, low toxicity, and low volatility. Consequently, several innovative applications have been demonstrated,16,17 from which its utilization as a solvent for synthesis and catalysis18−23 reducing solvent-based emission of VOC should be exemplified. GVL can also be used as an igniting liquid at a concentration of 50−100 wt % and mix with ethanol at a concentration up to 50 wt %, thus decreasing the mixture’s flash point and enhancing fast ignition. GVL has a
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RESULTS AND DISCUSSION First, GVL and EL as biomass-based chemicals were selected. Ethanol (EtOH) as a biofuel is used as blending compound, so mixtures as GVL 90% v/v−EtOH 10% v/v (hereafter GVL− EtOH), and EL 90% v/v−EtOH 10% v/v (hereafter EL− EtOH) were tested. The chemical formulas of selected biomass-based LFs are shown in Scheme 1. Their physicochemical properties are compared with commercially available LFs as confirmation of proper selection (Table 2). EtOH contains 34.8 wt % oxygen, while GVL and EL contain 32 and 33.3 wt % oxygen, respectively. Ronsonol and Zippo lighter fluids are blends of oxygen-free hydrocarbons. It is assumed that bound-oxygen can help in oxidization reaction and more proper combustion could be attained. In spite of MP being a crucial parameter in fuel consumption, it is not fundamentally important for LFs except in storage B
DOI: 10.1021/acssuschemeng.8b00546 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
Research Article
ACS Sustainable Chemistry & Engineering Scheme 1. Chemical Formulas of Biomass-Based Lighter Fluids
Table 3. GHS Classification of Flammable and Combustible Liquids57 flash point range [°C]
GHS category 1 2 3 4
issues. Under continental climate and normal storage conditions, they are all liquids except EL, which is solid at room temperature. FP is a more informative parameter on flammability, and VOC classification is proposed according to chemicals’ or products’ FPs. Although several classifications of indoor pollutants are available, LFs are used outdoors, so classifications of VOC relating to ambient air shall be considered. In this manner the Globally Harmonized System (GHS) of classification and labeling of chemicals (Table 3) shall be straightforward, since it comprises six different classification and rating systems. According to these classifications, EtOH belongs to GHS Category 1, EL GHS is in Category 4, and GVL seems out of this classification (liquids having FP > 93 °C are not categorized). BP is a basic property of a liquid, and the World Health Organization (WHO) classified VOCs depending on their BPs. Of note is that their classification refers to indoor organic pollutants, and the emission of grill activities surely belongs to outdoor pollutants.54 In spite of the fact that EtOH and Zippo lighter fluids belong to very volatile class of organics, GVL, EL and Ronsonol are regarded as normal VOCs. Both GVL and EL have a BP over 200 °C paired with a FP over 85 °C, and these parameters represent advantages during storage. While ethanol’s density is close to those of hydrocarbon mixtures, those of GVL and EL are 1.5-times higher, i.e., over 1000 kg/ m3. Higher and lower heating values (HHV and LHV) are very informative: Commercially available LFs have definitely higher (1.8-times higher) LHV values, which forecast an intensive and quick ignition and intensive combustion, and charcoal is suggested to start red heat earlier than assumed for GVL or EL. Higher VP values indicate the ease of ignition, as well as concern for storage issues. VP of EtOH lays between those of Ronsonol and Zippo, but GVL and EL possess a two or threeorders of magnitude lower VP resulting in ignition difficulties but favorable storage issues. As part of safety issues, toxicity has to be considered during selection of proper chemicals. Petroleum fuels containing carcinogens can be harmful and
flash flash flash flash
point point point point
