WO2014039613A1

WO2014039613A1 - Methods and system for converting heterogeneous waste stream of fats, oils, and grease (fog) into biodiesel

Info

Publication number: WO2014039613A1
Application number: PCT/US2013/058148
Authority: WO
Inventors: Paul Marshall; Arthur Jonas RAGAUSKAS; Matthew J. REALFF
Original assignee: Fogfuels, Inc.
Priority date: 2012-09-05
Filing date: 2013-09-05
Publication date: 2014-03-13

Abstract

The present invention is directed to production of alternate burning fuels, and more particularly to the conversion of renewable resources such as fats, oils, and grease (FOG) that are typically present in residential and industrial waste streams into clean burning bio-degradable, non-toxic alternative fuels, a/k/a biodiesel. The lipid rich material present in the waste water of cooking and food processing operations is frequently referred to as FOG (i.e., Fats, oils and Greases) and is present in grease trap waste (GTW).

Description

METHODS AND SYSTEM FOR CONVERTING HETEROGE OUS WASTE STREAM OF FATS, OILS, AND GREASE (FOG) INTO

BIO I S L

CROSS-REFERENCE TO REi .ATED APPLICATIONS

The present application claims priority to provisional, patent application.∞·. 61 /697,162, filed September 5, 2012

BACKGROUND OF THE INVENTION

The present disclosure relates generally to production of alternative burning fuels, and more particularly to the eon-version of renewable resources such as fats, oils, and grease {FOG) that are typically present in residential and Industrial waste -streams into clean burning bio- egradable, imiHnxie alternative fuels, a/k/a biodiesei.

The lipid rich material resent in the waste water of cooking and food processing operations is frequeritly referred to as p^'OO (be,, Fats, Oils and Greases) and is present in grease imp waste (GTW), In marr developed countries, the direct release of this material into municipal collection systems i illegal and. causes numerous problems due to its accumulation on pipes^■ which may lead to a- eduction ia eonveyan.ee capacity and eventually sanitar sewer overflows that in turn cost municipalities rnllJIoris of dollars each year in. cleaning, repairing, and maintenance lees, Indeed, m EPA report cited that of the numerous sani ar sewer overflows that occur each year i the US approximately 8% are d ue to line block ages and 47% o f these events are due to FOG deposits constricting sewer pipes.

T preclude these difficulties, many ^'municipalities- have required the use of grease abatement devices to remove grease from kitchen waste streams which is then periodically pumped out and disposed of, A i 99% National Renewable Energ Laboratory ( .REL) survey Indicated that In 30 US metropolita areas, FOG was generated at a. rate of approximately 1.9 gallons FOG/person/year, Research Fas revealed that FOG is approximatel 0 - i 5% of GTW with, typical values ranging Rom 2 - 3%, Further, the separation of FOG from water yields an energy rich process stream, (approx matel 7,000™ 9,000 BTUs/pormd) that has been proposed t r use in biodiesei produetiom Incineration, and anaerobic co-digestion.

The coiivm a of FOG to biodiesei has seen increasing interest in the Hterature, and there have en numerous approaches to converging cooking oils Into biodiesei. Biodiesei is usu lly defined as mono-alkyl esters of long chain fatty acids derived t¼m vegetable oils or

speeifkadons for use in diesel engines. Fuel-grade biodiesei typically has to meet industry specifications (ASTM 06751} k order to ensure proper performance, Biodiesei is now a. widely accepted alternative ibeh at least in par because of its com liance with t e health, effects testing recphrenients of the 1 90 Clean Air Act Amendments,

Biodiesel that meets AS^'IM D6751 and. is legally registered with the Environmental Protection Agency, and is a legal motor feel for sale and. distribution. Neat (i.e., 1.00 percent) biodiesei has been designated as an alternative fuel by the Department of Energy (DOE) and the US Department of Transportation (DOT). On the other hand, raw vegetable oil cannot mee biodiesei fuel specifications, is not registered with the EPA, and. is not a legal, motor foci

Overall, biodiesei is an attractive fuel resource as it has a higher eetane numbe than diesel fuel has no aromaties, and is approximately 10% oxygen by weight. Hence, biodiesei has been repotted to reduce the emissions of carbon monoxide, hydrocarbons, and particulate matter in the exhaust ga : when compared to diesel fuel exhausts. Biodiesei generally refers to the pure fuel before blending with diesel fuel Biodiesei blends are dene ted as "B X" whh "XX" representing the percentage of biodiesei contained in the blend (i.e., 20 is 20% biodiesei, 8(1% petroleum diesel).

Furthermore, biodiesei has been shown, to have fuel properties very close to diesel fuel and thus can be used, in diesel engines with little or no modifications to die engine or (he fuel system. Biodiesei has a solvent effect that may release deposits accumulated on tank walls and pipes from, previous diesel fuel storage. The release of deposits m clog filters initially and precautions should be taken to ensure that only fuel meeting the biodiesei specification is used.

Scientific research confirms that biodiesei exhaust has a. less harmful impact on human health than petroleum diesel fuel. Biodiesei emissions have decreased levels of polycyclic aromatic hydrocarbons (PAH) and nitrited. PAH compounds, which have been identified as potential cancer causing compounds. Test results indicate PAH compounds were reduced by 75 to 85 percent, with the exception, of benzo(a)anthracene, which was reduced by roughly 50 percent. Targeted nPAH compounds were also .reduced dramatically with biodiesei fuel, with 2- nitmtluorene and 1 untropyrene reduced by 90 percent,, and the rest of the nPAlI om ounds reduced to onl trace levels.

In 2009, the US produced S45 million gallons of biodiesoL 6% of which was from yellow grease/used restaurant fryer oil. As the availability of additional sources of yello grease h decreased and/or its cos has increased, the biodiesei. industry has continued to search tor new low-cost Fioresourees to be used, for the productio of biodiesei. One so.ch resource that is seeing increasing interest Is FOG< Examples of varions FOG bioresources melade (hot are not limited to) trap grease_* municipal slodge/seurn, dissolved air fiotatiotxT!otation grease, waste fats, brown pease, animal grease, skimmings, or generally any FOG hioresouree comprising up to 100% FFA (free fa tty acid) con e t - even if the POO bioresource is watery and eontammated.

SUMMARY OF THE INVENTION

Aspects of the present disclosure include methods to convert animal fats, tallo and waste vegetable oil, and other bioresources into biodiesei. In other aspects, such processes ar optimised for municipal and industrial waste stream byproducts that are typically highl contaminated, watery, and have very high FFA levels. In contrast to the limitations of traditional esteriifcshon, the disclosed methods can directl process up to 100% FFA and remove suilhr to ensure the resultant fuel is fully ASTM quality for on-road use. It will be appreciated that benefits of the disclosed met hods incl ude elimination, (or redaction) of caustic ehernieals, inexpensive preprocessing., etc. Eve further, the methods render economically- viable biodiesei production achievable and durable.

One embodiment of the Invention contemplates a system and method lor converting a waste stream comprising an admixture of fats, oiL and/or grease (FOG), water, and waste solids into hiodiese! fuel, comprising:

(a) a first stage comprising apparatus for at least partially dewatering the FOG waste stream and apparatus for removing solids remo val of the FOG waste stream, the first stage comprising a succession of first, stage processing stages comprising one or more of a solids removal stage, a water/oil separation stage, (an optional acid deguouning stage), and a fiUerin_;g/porificatio stage, producing a concentrated FOG stream:

at least one of said first stage processing stages involving the introduction of water, heat, and/or an alcohol;

(b) a second s ate for processing the concentrated FOG stream for estedikatiott ofthe waste st e m, into biodiesel, the second stage com rising an este iiieatioo stage nd iransesteri.fi cation stage, at least one of said esterification an transesteri leation stages Involving the removal of water, beat, or an alcohol; and

(e) an intermediate byproduct reuse stage f r .recycling one or more of the water, heat, and/or alcohol from the second stage to the first stage,

whereby the energy and other byproducts .from the second stage are reused in. the first stage to reduce the utilizatio of water and heat and/or to minimize the generation of other waste 'byproduct from biodtesei generation.

The present invention further contemplate embodiments, wherein excess heat from a. di still ation column in the second stage may be milke in. a dryer in the first stage.

The present invention also contemplate- embodiments wherein, further comprising, a heat exchanger for collecting excess eat from components in the second stage for use in the first stage.

The present invention also contemplate embodime ts wherein water collected from a nretharml/water distillation process In stage 2 is used to feed water washes in the first stage.

Embodiments of the present invention also contemplate systems and methods wherein a component in the second stage generates crude glycerin, and wherein the crude glycerin is used I» the first stage instead of an alcohol,

BRIEF DESCRIPTION OF THE FIGURES

PIG. I illustrates the basic chemistry Involved in the processing of plant arid animal triglycerides to hiodiesel.

FIG. 2 illustrates one embodiment of a first stage aud/or process of a FOG- to-biodiesel conversion process according to the present disclosure,

FIG. 3. illustrates another embodiment of a first stage and/or process of a FOG-io- hiodicsel con ersion process according to the present disclosure,

FIG. 4 illustrates a embodiment of a second stage and/or process of a FOG-to-^'biodlesel conversion process according to the present disclosure. DETAILED DESCRIPTION OF THE IN VENTION

For simplicity and illustrati ve purp ses, the principles of the present invention are described by jeife rm t various exeaipiary et«lx>dimeo.ts thereof Although the preferred embodiments of the invention are particularly disclosed herein, one of ordinary skill m the art will, readily recognize that die s me rima pies are e ually applicable to, an can be implemented i ether systems, ami thai any such variation would be within such aiodlEcaiioas that d not part from the scope ox the present invention. Before explaining the disclosed embodiments of the present nvention in detail, it is to be understoo that the invention is not limited in its application to the details of any particular arrangement shown, since the in vention is capable of other embodhneuts, l re terminology used . herein is for the purpose of description and not of limitation. Further_* although certain methods are described with reference to certain steps (hat are p esented herein in certain order, in many instances, these steps ma be performed in any order as would be appreciated by one skilled in the art, and the methods are not limited to the particular arrangemen of steps disclosed herein.

it will, be appreciated that the conversion, of FOG to biodiesel generally Involves a refinery process called imnsesterl icadon. This process is a. reaction of the oil with an alcohol to remove the glycerin, which is a by-product of biodiesel production. Traditional

traasesterificadon. technologies Irnve often encountered roadblocks processing this F0O material, not only doe to limited purification, capabilities but because the ceiling for free fatty acid (FFA) content is only 1-2%,

Aspects of the present, disclosure include method to convert animal fats, tallow and waste vegetable oil, and other bioresoorces into biodiesel In other aspects, suc processes are optimized .for municipal and industrial waste stream byproducts that a e: typically highl contaminated, watery, and have very high FFA levels, in contrast to die limitations of traditional, esterification, die disclosed methods can directly process u to 100% FFA and remove sulfur to ensure the resultant fuel is folly AST quality for on-road use, it wit! be appreciated that benefits of the disclosed methods include elimination (or reduction) of caustic chemicals, inexpensive preprocessing, etc. Even farther, the methods render economically-viable biodiesel production achievable and. durable.

In one embodiment, the biodiesel. is produced in a micto-rellnery that is co-located with Waste Water Treatment Plants (W WTPs), wherein the FOG bioresources are collected and processed, Ϊ» alternate e b dime ts, a kro-refmery can be constructed as a ortable anil (e.g. deployed on a flat-bed taikr) so that the bkxiiesei production can be deployed rapidly_* allowing for reduced transportation, costs and localized .fuel production. Even farther, fne disclosed methods itsrther eliminates the need for diluting hkh-FFA waste grease with costly v rgin ops to reduce f FA eoneeniraftoa (as is needed for traditional transesieriSeation. The gene a! conversion chemistry of processing plant and. animal triglycerides to blodiesei is relatively well established and is summarized in FIG. 1. Details of relating to the conversion chemistry are not addressed herein, as it is -assumed that knowledge relatin to suc will be knows to those skilled in the art,

FOG bioresources as received from various sources typicailyeontain several mm- triglyceride components (e.g,, phosphatides, tree fatty acids, etc.} which most be removed prior to conversion to biodiesei The primary process for FOG-to-biodleael involves a first stage tor solids removal and de watering* wuh a resultant. grease stream and certain byproducts (solids, water„ and a second stage that processes the grease stream into biodiesel and certain byproducts (additional solids, methanol water, glycerin).

According to one embodiment of a first stage, the overall process ( an embodiment of which Is shown In FIG, 2) comprises four stages: a solids removal stage, a water/oil separation stage, an acid degummmg stage, and a filteritig/porihcation stage. According to one aspect, the conversion process separates the FOG bioresouree Into a solids stream, a water stream, and a grease stream, t will be understood tha the solids stream is generally an unusable byproduct (at least for biodiesel production), that the water stream Is there-after treated by a municipal water treatment process, and the grease stream used tor biodiesel. production..

In this regard, PKF 2 is one embodiment of a first stage that for solids removal, de atering to provide a grease .stream for use in a second ester ipestioo slage.

in one aspect, a solid removal stage comprises junk screening, grinding,

cooking/hydrolysis, and decanting. Generally, junk screening Involves predicating trap grease which is then passed through a traveling screen to remove large solids. According to one exemplary embodiment, the temperature of the FOG bioresouree (e.g., trap grease shown flowing into point A in FIG, 2) is maintained below a. predetermined termperatnte (e.g., 85^! F). Further, according to one embodiment, a magnetic trap removes ferrous metals. Typically, a grinding process involves grinding tire solids that remain after the junk screening process Into a i iforai size via a grinde pum . These solid are primarily food waste. Afte the grinding process and. according to one en:rbodlmeni these .remaining solids undergo a

cooking/hydrolysis proces wherein they are heated, to coagulate proteins and promote separation of tats and solids. According to one as ect, a caustic may be added to hyrlrolyxe hair and other proteins. After cooking/hydrolysis and accordin to one embodiment a horizontal centrifuge decanter is used to separate solids irons liquids daring a typical decanting process. Finally, according to certain embodiments, separated solids are dried to a..meal In. a dram dryer.

Generally, after the solids .removal stage, the liquid stream resulting from the decanting process undergoes; a water/oil. separation process, according to one embodiment Accordin to one aspect, the liquid stre m is separated through a series of two disc centrifuges into a water stream and a grease stream.

Once the liquid stream has been separated into a water stream and a grease stream, the grease stream typically undergoes a degurmning process. According to one embodiment, a degiuuming process in volve the removal of gums and phospholipids from the oil. through an acid degurnming process. As will be understood by one skilled In the arc a typical acid degnm ing process Involves removal of phosphatide content, be, ums and phospholipids, thereb leading to lower residual phosphorus content

According to another and alternative em odiments of the first stage, the grease stream ma not undergo an acid deguunning process. One such, embodiment is illustrated by FIG. a.

It will be noted that the first stage of both mbod me ts Involve the introduction of beat si: various locations, e.g. in FIG. 2 a dram dryer 210, a cooker between streams C and D, a reactor vessel between streams 0 and F, and the siearn heater between streams J and M as well as the introduction of additional water, e.g. at step 230, and in FIG. 3 re-melier at the initial entry point, a. vacuum dryer. According to aspects of the disclosure excess heat and/or water from later process steps e.g. from stage 2 are introduced to stage 1 to effect energy and water savings, in accordance with inventive aspects of the disclosure.

Various other inventive aspects associated with the processes and associated components will be better understood In the discussions of at least the embodiments that follow. Refer now m this regard now to FIG. 4, which illustrates an. embodiment of a second stage and/or process of a FfXi-to-biodiesei conversion, process according to the present disclosure. As will be understood by one skilled, in the art, the second stage of the. process shown, i n FIG . - begins after (lie dewatermg process at step 1, which corresponds to the first stage as described herein. The grease stream ai step 4 is fir provided to an. esterifkatiors stage, which comprises a reactor that Introduces sulphuric acid at step 6 arid an alcohol ai step 5, such as .methanol or glycerol, Alterirati vely, cra.de glycerine could be used. This step of methauoiysis or glycolysis converts the free fatty acids into their ester form.

The reactor output is provided at 7 to a water wash at 9 where add tional water is introduced, whose output 1.0 is provided to a centrifuge. The centrifuge output is an acidic waste stream 12 that is provided, with other waste byproducts; at 17 to neutralization stage at 18, where NaOH is introduced, ^'Ore concentrated FOG components f om the centrifuge ate provided at 1 1 to a first evaporator, which, boils off volatile^■materials at 13 which are introduced into the acidic waste stream at 17. In accordance with an aspect of the disclosed system, stream 13 is condensed before it Is mixed with stream 16 to form stream 17, As is known, condensation requires remo val of heat and is another benefit to the disclosed aspects of heat integration (otherwise other means of removing the heat such, as cooling water would be required) . The same will he true for streams 34 and 41. The FOG remaining in the evaporator i provided at 14 in a reactor.

The. acidic waste stream at 1.7 from the esterifleation stage, after neutralisation ai 1 , is provided at 20 to a distiller, which is heated in the kn wn manner to distill alcohol (methanol) at 21 >, and. additional waste water at 22, These waste byproducts are re-used i accordance with inventive aspects as described herein.

The concentrated. FOG from the evaporator at 14 is introduced to a O¾«sesterifeation stage, which initially comprises a reactor that, introduces sodium methoxide at 25 nd methanol at 24, Again, advantageously, rite methanol r m the distillation ai 21 may he reintroduced at 24 for process efficiency. Although, methanol, recycling is known in the art, a Is recycling of water wi thin the scope of FIG, 4,. inventive aspects of the disclosed process rela te to the point at which recycled water is introduced into earlier stages of the FOGAo-biodksei process a described herein. The output, from the reactor at 26 is provided to a glycerin settling tank, fire settled glycerin byproduct is removed at 28 and treated with sulphuric acid at 23, to provide a glycerin byproduct, a 40. The glycerin is provided to a second evaporator, which provides crude glycerin at 42 and vokdl.es at 41 , whic are processed by the neuiraika&ou at 18, 19.

The FOG from the settling tank, now .from which glycerin has been removed, is provided with ano her water wash at 27, where additional water k introduced at 29, Excess water is removed at 30 and provided to the neutralization at 18, 19. The snore purified FOG is provided at 1 to a second centrifuge, which removes heavier constituems at 33 to tire acidic water rseitarallzatlon at 1 1 . Hie rem a sg FOG is then provided to a third, evaporator at 32» which removes volatdes at 34 to the acidic waste stream and. neuiraiizatioo ai I S, 1% md puri ied FOG at 35 to aa ion exch n e process. The ion exchange process output is provided at 36 to a biodiesei distillation vessel, which, produces the desired hiodiesel output at 37 and additional waste residue at 3S,

Given the above-described processing steps to generate hiodiesel at 37, it will aow be appreciated that certain energy and waste b oducts developed at various points in the first- stage and second stage may be reused / reprocessed to achieve energy savings, as well as minimize the quantity white improving the quality of the waste water generated in the production of the biodiesei, thereby achieving one of the primary objectives of the process to reduce the introduction of undesirable FOG in the municipal wastewater stream.

fju.a av Savings (^"omre ts 210, .220, 420

It will be understood thai the evaporators ilked in. the process shown in FIG. 4 necessarily mvolve eventual condensation of the e vaporator outputs so as to obtain a stream of volatile byproducts. Suc condensation, results .fro t the removal of heat from the overhead stream, torn distillation columns which, is a vapor, e,g, stream 21 or stream 37. This results in output byproduct streams 21 and 37, a portion: of which are reiksxed to the dlstdla!ion columns. According to an aspect, the Drum Dryer (shown ia FIG. 2), which is itsed in the solids drying process described above, is co igured to utihxe heat energy that is provided by condensation f om: one or more of components {evaporators) 41, 13, and 34 m conjunction with condenser / disdllatioiu specificall the condenser heat in 430 (alt of which are shown, in FIG. 4),

According to another aspect, the beat required to produce the steam shown in FIG. 2 as provided to the heat exchanger between streams J and M i collected from the heat energy thai is provided by condensation from one or mere of components 41, 13, and 34 in conjunction wi th condenser / distillation 21 , 22 (all of which are shown in FIG. 4). According to anpther as ect, water collected from, the methaooi/wa er distillation, process shown as 22 FIG, 4 is be used to Iced the w^:ater washes a 8 and 2 , also shown i« FIG. 4. The integration cap also be made with the water stream fed to the mixer, situated between streams N and 0, prior to the degmnmifcg reaction vessel l beled 2 0 OP f 10. 2, Advantageously, the reuse / recycling of water results in lowered overall water usage, as well as improved ultimate wafer quality when water Is eventuall removed from the process and introduced into municipal wastewater treatment

According to y et another aspect., an output of the solids removal mid water/oil separation processes described above (and illustrated m FIGS- 2, 4), can be combined with, crude glycerin produced by coniponent 42 (as shown ia FIGS, 2. 4), such combination used to iced glycerin instead of methanol into component 5 (as shown In FIGs,. 2„ 4),

While the invention has been described with reference to certain exemplar embodiments thereof, those skilled, in the art. may make various modifications to the described, embodiments of the invention without departing from the scope of the invention, The terms and: descriptions used herein are set forth, by way of illustration only and not meant as limitations: In particular, although the present invention h s been, described by way of examples, a variety of compositions and.

processes wpnid practice the inventive concepts described herein. Although the invention has been described and disclosed in various terms and. certain embo iments, the scope of the invention is not. inten ed to be,, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are par ce!ariy reserved, especially as they fail within the breadth and. scope of the claim hem appended. Those skilled in the art will recognize that these and other variation are possible within the scope of the iuvemion as defined in the following claims and their equivalents..

30^'

Claims

What is claimed is:

1. A s stem for converting a waste stream, comprising n admixture of ihts, oil, and/or grease (FOG.), water, and waste solids into hiodissel fuel, comprising:

(a) a first stage comprising apparatus for at least partially dewatering the FOG waste stream and apparatus for emoving solids removal of .the FOG waste stream, the first stage comprising, a. Success on of first stage processing stages .comprising one or more of a solids removal stage, a water/oil separation stage, (an optional acid dcgumnnng stag )_;: and a llltering parificai!OH stage, producing a concentrated FOG stream

at least one of said first stage processing stages invo ving the introduction of water, heat, and/or an alcohol;

(b) a second, stage for processing the concentrated FOG stream tor esteriheation of the waste stream into biodieseh the second st ge comprising an esterificatfon. stage and an transesterification stage, at least one of said esforiikation and t ansesterificaiion stages involving the removal of water, beat or an alcohol; and

(c) an intermediate byproduct reuse stage for recycling one or more of the water, heat, and/or alcohol from the second stage to the first stage,

whereby the energy and other byproducts front the second stage are reused in the first .stage to reduce the uti!i¾atk>n of water and heat, and/or to minimize the generation of other waste byproduct fr m biodiese! generation,

2. The system of claim I , wherein excess heat from a distillation column in the second, stage is udliaed m a dryer In the first stage.

3. The system of claim I _; further comprising a heat exchanger for collecting

excess heat -from components i the second stage for use in the first stage.

4. The system of claim 1, wherein water collected from a methano l/water distillation process in stage 2 is used to iced water washe in the first stage.

ii

5. The s stem of claim 1. wherein a co.mpon.ent m the second stage ener tes c ude ■glycerin, and. wherein the erode glycerin is used in the first stage instead of an alcohol,

6^', A. method for converting a waste stream comprising m\ admixture of als, o l, and/or grease (FOG), water, and waste solids Into hiodiesel fuel, com rising:

(a) a. first stage of at least, partially dewaterlag the FOG waste stream by performing one or more of the steps of solids removal, water/oil separation, optional acid degao¾«i«g, and a flhcring/pur catlon, at least one of said first stage processing steps involving the imrodiietioB of water, heat, and/or an alcohol, thereby producing a concentrated FOG stream;

fb) a second stage for processing the concentrated FOG stream for esleriikation of the waste stream into biodicse!, the second stage comprising the steps of csterliication and an transesterifkation, at least one of said esrerification and transesterirleaxion steps involving the removal of wate , heat, or an alcohol; and

(e) m imermediate byproduct reuse stage for recycling one or more of the water, heat, an4 or alcohol from the .second stage to the first stage,

whereby the energy an other byproducts from, the second stage are reused in the first stage to reduce the utilization of water and heat aad/or to niinunke the generation of other waste byproduct from biodlesel generation,

7. The method of ciami 6, wherein excess heat fmm a distillation column, in the second stage is utilised in a dryer in the first stage,

8. The method of claim 6, farther comprising a heat exchanger for collecting excess heat from components in the second stage for use in the first stage,

9. The method of claim 6, wherein wate collected from, a metharsol/water distillation process in stage 2 is used to teed water washes in the first stage,

1.2

10. The method of claim 6, wherei a component in the second stage generates crude glycerin,, and wherein the erode glycerin Is used in the first stage instead of an alcohol.