Ind. Eng. Chem. Res. 2008, 47, 2849-2854
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APPLIED CHEMISTRY Wet Air Oxidation of Meat-and-Bone Meal and Raw Animal Byproducts Ste´ phane Barbati,* Virginie Fontanier, and Maurice Ambrosio Laboratoire de Chimie & EnVironnement, UniVersite´ de ProVence-3, Place Victor Hugo (case 29), 13331 Marseille cedex 3, France
The oxidation of meat-and-bone meal (MBM) and two different raw animal byproducts (before and after rendering) has been studied by wet air oxidation (WAO) and catalytic wet air oxidation (CWAO), which represents an alternative way of animal byproduct disposal. The degradation of organic compounds was monitored by dissolved organic carbon (DOC) analysis following the subcritical conditions (230-280 °C, 9.9-18.6 MPa), which has led to the degradation of up to 90% of the initial total organic carbon (TOC) and reached 99% within the presence of platinum as a catalyst for the oxidation of a raw non-defatted sample. The oxidation of organic compounds has been studied as a function of pressure and temperature and showed that the TOC removal increased at higher temperature and higher pressure favoring the mass transfer of oxygen and organic compound into the liquid phase. The byproducts of the oxidation were identified; acetic acid was the main refractory organic compounds representing approximately 50% of the final residual TOC. The major inorganic byproduct was identified as ammonia, which was quantitatively removed (98.9%) in presence of platinum catalyst supported over alumina in basic medium. Introduction The recent feed-borne crises in the EU (dioxin in 1999, classical swine fever in 2000, foot and mouth disease in 2001, and EU-wide Bovine Spongiform Encephalopathy (BSE) crisis in 2001) have led to changes in the rules of all animal byproducts not intended for human consumption (EC no. 1774/ 2002). For example, category 1 materials (i.e., animal byproducts, including specified risk materials, presenting the highest risk such as transmissible spongiform encephalopathies or scrapie, residues of prohibited substance) must be completely disposed of as waste. The consequence is that the amount of material that must be eliminated has rapidly increased over the last years across the EU. Actually, the total volume of slaughter byproducts produced in EU rises 17 million tonnes/year and induces the annual production of 3.6 million tonnes of animal meal and 1.5 million tonnes of rendered fat (MEMO/01/378, 2001). The current capacities of treatment of meat-and-bone meal (MBM) are 2.5 million tonnes a year, generating the problem of risks related to their storage. The regulation introduced incineration and co-incineration as outlets for animal byproducts and, for certain categories of material, permitted composting and biogas production. It also provided for alternative outlets to be permitted like hydrolysis processes, biodiesel production process, and Brooks gasification process (EC no. 92/2005). The quasi-exclusive way of elimination of animal byproducts not for human consumption is the incineration/coincineration. This process is actually the most adapted for destruction of these wastes. It must be highlighted that incineration produces toxic fumes containing NOx, sulfur derivatives, and dioxins, which represent a major disadvantage. Concerning the inactivation of BSE prion, which reveals an unusual stability toward temperature and chemicals, animal byproducts rendering * To whom correspondence should be addressed. E-mail: Stephane.
[email protected].
require the preliminary treatment at the following conditions: 133 °C, 0.3 MPa during 20 min, as described in the “animal byproducts regulation” ABPR 1174/2002/EC. The inactivation of BSE using alkaline hydrolysis of animal waste in an autoclave at medium temperatures has been evaluated1,2 and, recently, the treatment of animal waste based on these conditions has been adopted by the commercial company Waste Reduction Europe Ltd. This process has been evaluated by Scientific Steering Committee of EC, which emitted an opinion and a report.3 We describe here a one step process, which directly transforms crude animal byproducts by wet air oxidation (WAO) to a neutral effluent and that deactivate BSE prion.4 Wet air oxidation appears as an effective and alternative process consisting of a flameless combustion process that operates in the liquid phase between molecular oxygen and aqueous substances (organic and inorganic) under a moderate temperature and a high pressure (150-350 °C, 10-20 MPa).5 The reaction time may vary from 20 min to 3h. Under these conditions, the organic matter is quantitatively converted into CO2 and H2O, without any production of NOx, SO2, dioxins, furans, and particles. Its application is particularly adapted for the processing wastes that are too diluted (COD < 300 g/L) to be incinerated or too toxic to be digested biologically. Otherwise, the degradation of organic substrates by WAO becomes autogenic from a COD concentration in the upper 15 g/L and provides energy that may be recovered in thermal, mechanical, or electric form. Concerning hazardous materials, all eventual biological agents and particularly those that are pathogenic, this system presents operational conditions that are more restrictive than the one actually recommended by the EU (ABPR 1174/2002/EC). We present here first applications of WAO to the destruction of MBM and byproducts before and after fat processing. The catalytic effect of platinum was also investigated.
10.1021/ie070947a CCC: $40.75 © 2008 American Chemical Society Published on Web 03/29/2008
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Ind. Eng. Chem. Res., Vol. 47, No. 9, 2008
Experimental Section Substrates and Reagents. Meat-and-bone meal (MBM) and raw animal byproducts were provided by SARIA Industries and used as received. MBM appeared as brown and dehydrated granular particles (
