Anaerobic digestion of organic solid poultry slaughterhouse waste – a review

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<ul><li><p>Review paper</p><p>Anaerobic digestion of organic solid poultryslaughterhouse waste a review</p><p>E. Salminen 1, J. Rintala *</p><p>Department of Biological and Environmental Science, University of Jyvaaskylaa, P.O. Box 35, FIN-40351 Jyvaaskylaa, Finland</p><p>Accepted 23 October 2001</p><p>Abstract</p><p>This work reviews the potential of anaerobic digestion for material recovery and energy production from poultry slaughtering by-</p><p>products and wastes. First, we describe and quantify organic solid by-products and wastes produced in poultry farming and poultry</p><p>slaughterhouses and discuss their recovery and disposal options. Then we review certain fundamental aspects of anaerobic digestion</p><p>considered important for the digestion of solid slaughterhouse wastes. Finally, we present an overview of the future potential and</p><p>current experience of the anaerobic digestion treatment of these materials. 2002 Elsevier Science Ltd. All rights reserved.</p><p>Keywords: Anaerobic digestion; Ammonia; Inhibition; Long-chain fatty acids; Nutrients recovery; Renewable energy; Solid poultry slaughterhouse</p><p>waste</p><p>1. Introduction</p><p>In the past decades, the consumption of poultry inFinland and in many other countries has been on theincrease, reaching about 10 kg per capita in Finland in1999 and even more elsewhere (Finnish Food and DrinkIndustries Federation, 1999, Fig. 1).</p><p>As a result of the growing poultry industry, poultryslaughterhouses are producing increasing amounts oforganic solid by-products and wastes. On the otherhand, legislation on the recovery of organic materialsfor animal feed is becoming tighter (Commission of theEuropean Communities, 2000) and more restrictive oftheir landlling (Commission of the European Com-munities, 1999). In this regard, anaerobic digestion is apromising alternative for the treatment of these mate-rials, as the process combines material recovery andenergy production (DeBaere, 2000; Hulsho Pol et al.,1997).</p><p>Little literature is available on the characteristics andquantication of organic solid by-products and wastesfrom poultry slaughterhouses, though such informationis needed to evaluate treatment options for these mate-</p><p>rials. Bull et al. (1982), Cooper and Russel (1992), andJohns (1995) have reviewed the characteristics andtreatment of wastewater in slaughterhouses, whereasTritt and Schuchardt (1992) present the most recentsummary on the characteristics and treatment of solidwaste and wastewater streams from cattle and pigslaughtering.</p><p>The objective of the present study was to review rel-evant information necessary to determine the applica-bility of anaerobic digestion to energy production andmaterial recovery from poultry slaughterhouse wastes.Accordingly, we will describe and quantify organic solidby-products and wastes produced in poultry farmingand poultry slaughterhouses and discuss their recoveryand disposal options. We will also review certain aspectsof anaerobic digestion considered essential in digestingsolid slaughterhouse wastes. In addition, we present anoverview of experience with anaerobic digestion treat-ment of these materials.</p><p>2. Quantities and characteristics of organic solid by-</p><p>products and wastes from poultry farming and slaughter-</p><p>ing</p><p>In this section, we quantify and characterise organicsolid by-products and wastes produced in broiler farm-ing and slaughtering (Table 1). Broiler was chosen as anexample because of its importance among all poultry</p><p>Bioresource Technology 83 (2002) 1326</p><p>*Corresponding author. Tel.: +358-14-260-1211; fax: +358-14-260-</p><p>2321.</p><p>E-mail address: jukka.rintala@cc.jyu. (J. Rintala).1 Present address: SCC Viatek Ltd., Piispanmaaentie 5, P.O. Box 3,</p><p>FIN-02241 Espoo, Finland.</p><p>0960-8524/02/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved.PII: S0960-8524 (01 )00199-7</p></li><li><p>products. The slaughtering of broilers does not essen-tially dier from the slaughtering of other poultry spe-cies, though the amount of by-products and wastes doesdepend on the species. Organic solid waste may be de-ned as organic biodegradable waste with moisturecontent below 8590% (Mata-Alvarez et al., 2000).</p><p>Litter, i.e., excreta and peat or wood chip, is pro-duced at about 2 kg/broiler in deep litter broiler growingfacilities where the birds are allowed to roam freely(Saksala, T., personal communication), and it may varyconsiderably in its characteristics (Table 1) dependingon how long it remains on the ground (Webb andHawkes, 1985a). Its nitrogen content generally increases</p><p>with increasing poultry manure deposits, but uric acidmay degrade to ammonia and then volatilise from thelitter (Webb and Hawkes, 1985a). In comparison, cagedpoultry produce only manure (Table 1).</p><p>Broilers are grown for 56 weeks to a weight of about1.81.9 kg before they are slaughtered. Their naturaldeath rate is about 23%, being highest during the rst 2weeks of their growth with bodies averaging in weightabout 1015 g/broiler (Saksala, T., personal communi-cation). Breeding produces waste which contains peat,eggshells, stillborn, unborn, and dead birds. In slaugh-terhouses the excreta from vehicles, crates, and cages areusually washed into the sewer.</p><p>In the past few decades, poultry slaughtering hasmarkedly changed as the industry has sought to improveits processing eciency. Today broilers are often pro-cessed in highly automated purpose-designed plants,which typically slaughter and process tens of thousandsof birds per day. In these plants, broilers are removedfrom crates and cages, hung from shackles (Papinaho,1996), electrically stunned, and then bled (Fig. 2). Bloodaccounts for about 2% of the live weight of a broiler,about 40 g/broiler (Rinne, K., personal communica-tion), whereas dried blood contains about 95% protein(Table 1) (Cooper and Russel, 1992). After bleeding andto ease feather removal, broilers are scalded by im-mersing them in hot water (Fig. 2) (Papinaho, 1996).Feather removal may be performed by rubbing thescalded carcass with rotating rubber ngers and usingpressurised water jets (Fig. 2) (Papinaho, 1996). Feathercontributes about 10% to the broilers live weight(Rinne, K., personal communication), while driedfeather contains 8599% proteins (Table 1) (Papado-poulos, 1985). Subsequent evisceration produces, inpercentage of live weight, head (ca. 6.9%), feet (ca. 4.4%)and viscera (ca. 10%) (Rinne, K., personal communi-</p><p>Table 1</p><p>Quantities and characteristics of organic solid wastes produced in poultry (broiler) farming and poultry slaughterhouses</p><p>TS</p><p>(%)</p><p>VS</p><p>(% of TS)</p><p>Kjeldahl-N</p><p>(% of TS)</p><p>Protein</p><p>(% of TS)</p><p>Lipids</p><p>(% of TS)</p><p>Methane potential</p><p>(m3=kg VSadded)</p><p>Methane potential</p><p>(m3=kg wet weight)</p><p>Carcass 37c Na Na Na Na Na 0.200.25b ;c</p><p>Litter 5281h 6165h 3.25.7h Na Na 0.140.22h 0.100.15h</p><p>Manure 2047d ; i 6076d;i 4.66.7d;i Na 1.52.1e 0.20.3d ;f 0.040.06d;f</p><p>Feather 24.3g 96.7g 15g 91g 110a 0.2g 0.05g</p><p>Blood 22g 91g 7.6g 48g 2g 0.5g 0.10g</p><p>Oal, feet, and head 39g 95g 5.3g 32g 54g 0.70.9g 0.3g</p><p>Trimmings and bone 22.4g 68g 68.6g 51g 22g 0.60.7g 0.150.17g</p><p>Na: not available.a Bourne (1993).b Chen (1999).c Chen and Shyu (1998).dHuang and Shih (1981).eMackie et al. (1991).f Saey et al. (1987).g Salminen et al. (submitted).hWebb and Hawkes (1985a).iWebb and Hawkes (1985b).</p><p>Fig. 1. Pork, beef, and poultry consumption. (a) In Finland from 1985</p><p>to 1999. (b) Per capita in dierent countries in 1997 (Finnish Food and</p><p>Drink Industries Federation, 2000).</p><p>14 E. Salminen, J. Rintala / Bioresource Technology 83 (2002) 1326</p></li><li><p>cation, Table 1, Fig. 2). After slaughtering, the broilerweighs an average of 1.4 kg (Rinne, K., personal com-munication), and the carcasses are chilled upon evis-ceration to control microbial growth. Furtherprocessing produces trimmings and bones in varyingamounts, depending on practices and processes and thedegree of processing, about 140 g in live weight (Rinne,K., personal communication). Poultry slaughterhousesproduce also a variety of spoiled meat and condemnedmaterials, and their wastewater treatment yields wastessuch as screenings, fat from grease traps, settlings, excessactivated sludge, and otation tailings (Bull et al., 1982;Johns, 1995).</p><p>Poultry by-products and wastes may contain several100 dierent species of micro-organisms in contami-nated feather, feet, intestinal contents, and processingequipment, including potential pathogens such as Sal-monella sp., Staphylococcus sp., and Clostridium sp.(Chen, 1992). Compared to many other countries,Finnish meat products contain considerably lesspathogens (Ministry of Agriculture and Forestry, 2000).For example, in 1997, positive Salmonella samples inbroiler and turkey meat in slaughtered ock and meatfrom cutting plants rated 0.6% and 3.1%, respectively(Ministry of Agriculture and Forestry, 2000). In com-parison, in the US, about 30% of chicken products arecontaminated with live Salmonella, and 6080% ofchickens are contaminated with Campylobacter, many</p><p>strains of which are resistant to common antibiotics(Haapapuro et al., 1997).</p><p>In addition, animals may accumulate various metals,drugs, and other chemicals added in their feed for nu-tritional and pharmaceutical purposes (Haapapuro et al.,1997). Veterinary drugs and other chemical contami-nants are also present in poultry in varying concentra-tions; e.g., zinc and copper concentrations in poultryfeeds in England and Wales range from 284030 to5234 mg/kg TS, respectively, whereas zinc and copperconcentrations in poultry manure were ca. 400 and ca.80 mg/kg TS, respectively (Nicholson et al., 1999).Poultry litter in Israel has been shown to contain vary-ing levels of testosterone (up to 700 ng/g) and esterogen(up to 500 ng/g), which can interfere with reproduction(Shore et al., 1993).</p><p>3. Recovery and disposal of organic solid by-products and</p><p>wastes produced in poultry farming and poultry slaugh-</p><p>terhouses</p><p>This section reviews the current recovery and disposalpractices and requirements for organic solid wastesproduced in poultry farming and poultry slaughter-houses (Fig. 3). Council Directive 90/667/EEC (Com-mission of the European Communities, 1990) speciesthe animal and public health requirements for the</p><p>Fig. 2. Organic solid materials (per broiler) produced in broiler farming and slaughtering (Papinaho, 1996; Rinne, K., personal communication;</p><p>Saksala, T., personal communication; adapted from Shai, 1992; Tyooppoonen, P., personal communication).</p><p>E. Salminen, J. Rintala / Bioresource Technology 83 (2002) 1326 15</p></li><li><p>disposal and processing of animal waste to destroy po-tential pathogens present in the waste. Animal wastemay be dened as carcasses or parts of animals, in-cluding products of animal origin not intended for directhuman consumption (Commission of the EuropeanCommunities, 1990). Animal waste is classied either ashigh-risk material, if it is suspected to present serioushealth risks to people or animals, or as low-risk mate-rial, if it does not. High-risk material includes animalsdied on the farm, stillborn and unborn animals, andspoiled and condemned materials. The Commission iscurrently working on a new Directive for health rulesconcerning animal by-products not intended for humanconsumption (Commission of the European Communi-ties, 2000; Rantajaarvi, P., personal communication).</p><p>3.1. Rendering</p><p>Rendering refers to various heating processes toseparate fat from meat (Swan, 1992). Rendering at 133C for a minimum of 20 min at 3 bars (Commission ofthe European Communities, 1990) or an alternative heattreatment (Commission of the European Communities,1992) is needed for high-risk materials intended for an-imal feed or as an intermediate product for the manu-facture of organic fertiliser or other derived products.Rendering produces meat-bone-meal, which may beused in animal feed or as fertiliser or be further pro-cessed via anaerobic digestion or composting. In addi-tion, rendering produces fat, which may be used foranimal feed, in chemical industry products, or burned asfuel.</p><p>3.2. Use for animal feed</p><p>As rich sources of protein and vitamins, slaughter-house by-products are preserved with formic acid andused as animal feed either as such or together with</p><p>regular feed, e.g. in Finland, for fur animals or for petfood production (Pulsa, 1996). As one among the big-gest fur animal producers in the world, Finland uses anannual 370 million kg of fur animal feed, more than halfof which is by-products from the meat and sh industry(Pulsa, 1996). Poorly degradable in its natural state,feather is not suitable for animal feed, but pre-treatedfeather is sometimes used in animal feed (El Boushy andvan der Poel, 1990; Onifade et al., 1998; Papadopoulos,1985). Legislation, however, is becoming stringent aboutthe use of slaughter by-products for animal feed to re-duce the risk of disease transmission via the feed and thefood chain (Commission of the European Communities,2000; Rantajaarvi, P., personal communication).</p><p>3.3. Incineration</p><p>Incineration refers to technologies of thermal de-struction, apparently among the most eective methodsfor destroying potentially infectious agents (Ritter andChinside, 1995). Air-dried poultry litter is a provencombustible solid fuel with a gross caloric value ofabout 13.5 GJ per tonne, about half that of coal(Dagnall, 1993), whereas materials having a high mois-ture content have little or no energy value. In incinera-tion, the air emission, process conditions, and thedisposal of solid and liquid residues need to be strictlycontrolled. The Commission of the European Commu-nities is currently preparing a new Directive on wasteincineration.</p><p>3.4. Burial and controlled landlling</p><p>Burial of dead birds on the farm is strictly controlledto avoid groundwater contamination. As the operation,monitoring, and control of landlling have also becomemore tightly regulated under Directive 1999/31/EC(Commission of the European Communities, 1999),</p><p>Fig. 3. Current recovery and disposal of organic solid by-products and wastes produced in the poultry farming and slaughterhouses in Finland and</p><p>the option of anaerobic digestion for the recovery of these materials ( ) (Lahtinen, M., personal communication).</p><p>16 E. Salminen, J. Rintala / Bioresource Technology 83 (2002) 1326</p></li><li><p>landlls must prevent or reduce as much as possibletheir adverse eects on the local environment, particu-larly the pollution of surface water, groundwater, soiland air, as well as on the global environment, includingthe greenhouse eect. All these measures increase thecosts of landlling. Furthermore, legislation is restrict-ing landlling of organic wastes but allowing biologi-cally treated material to be used as landll cover(Commission of the European Communities, 1999).</p><p>3.5. Composting</p><p>Composting, an aerobic biological process to de-compose organic material, is carried out in either win-drows or reactors. It is a common method to treatpoultry slaughterhouse wastes, including screenings,otation tailings, grease trap residues, manure, litter,and sometimes also feather. Composting reducespathogens, and composted material may be used as soilconditioner or fertiliser (DeBertoldi et al., 1983...</p></li></ul>