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International Poultry Expo International Rendering Symposium
January 29, 2016 Atlanta, GA, USA
A Comparison of the Safety and Sustainability of Three Methods Used to
Process Meat By-Products
Charles H. Gooding, PhD, PE Emeritus Professor ∙ Clemson University
Clemson, South Carolina USA Chemical Engineering Consultant
Purpose Examine three alternative methods of handling fallen animal carcasses and meat by-products from food animal slaughter.
Anaerobic Digestion Composting Rendering
Scope: consider these key factors
Biosecurity
Environmental
sustainability
Resource recovery
Biosecurity and other HSE issues • Rendering is an established industrial process,
operated and controlled carefully under a Code of Practice1 developed by the Animal Protein Producers Industry (APPI). Audits and certification of compliance with the code are conducted by a third party, the Facility Certification Institute2.
• Every rendering plant is regulated by local and/or state health, safety, and environmental (HSE) agencies to insure that employees, the public, and the environment are protected.
Biosecurity and other HSE issues • The rendering industry and individual rendering
facilities are regulated at the federal level by the Food and Drug Administration3 (FDA), the Animal and Plant Health Inspection Service4 (APHIS), and other components of the US Agriculture Department (USDA).
• The Food Safety Modernization Act expanded FDA regulatory control over all animal food, including rendered ingredients. Requirements include hazard controls, good manufacturing practices, and extensive recordkeeping.5
Biosecurity and other HSE issues
• Current health and environmental regulations applicable to composting and anaerobic digestion (AD) vary considerably from state to state.6-8
• Most composting and AD regulations do not address co-processing of meat by-products (MBP) because it is not common practice. Research has shown that co-composting and anaerobic co-digestion of MBP with manure and other materials are possible, but challenging.
Biosecurity and other HSE issues • AD and composting require strict control of
temperature-time conditions to insure that pathogens are destroyed. 9-13 This is especially difficult to achieve in composting due to the heterogeneous nature of the material.
• Addition of MBP complicates the operation of anaerobic digesters because ammonia released from proteins in MBP inhibits microbial growth.14
• Leachate from compost windrows can harm plants, animals, and humans if it is not collected and treated properly.10,12
Greenhouse gas (GHG) emissions • Rendering requires burning of fossil fuels to produce
steam for heating, but nearly all of the carbon in the meat by-products (MBP) is retained in the fats and proteins produced.
• Compared to aerobic degradation of meat by-products, rendering avoids 75% of potential GHG emissions.16,19,20
• Energy requirements and GHG emissions from co-digesting MBP anaerobically are relatively small if CH4 losses are minimized,25-27 but storage of digestate slurry in open tanks can multiply GHG emissions by a factor of 10.28
Greenhouse gas (GHG) emissions Co-composting of MBP with manure and bulking materials requires minimal electricity, and GHG emissions from equipment used to turn the windrows
are also small. 22 But 45 to 75% of the carbon in co-composted MBP is released as carbon dioxide (CO2) 17,18 and 4 to 20% is released as methane (CH4), 17,18 which has 25 times the global warming potential (GWP)23 of CO2. In addition, 6 to 9% of the nitrogen in MBP proteins is emitted as nitrous oxide (N2O),17,18 which has 300 times the GWP23 of CO2. Overall co-composting of MBP emits 3 to 5 times as much GHG as converting all carbon in the material directly to CO2.
Resource recovery • Rendering converts about 99% of the fats, proteins,
and nutrients in meat by-products into valuable ingredients of animal feeds.12,16,21 Alternatively, rendering and subsequent chemical processes can be used to convert MBP into biofuels and higher-value industrial materials.12,16
• Anaerobic co-digestion of MBP with manure produces only low-value fuel gas (60-80% methane) and a digestate that can be used as fertilizer.11,12
• Co-composting of MBP with manure and bulking materials converts a small fraction of the MBP into a nitrogen-enriched soil amendment material12,17,18
that has relatively low economic value24.
Resource recovery For reasons cited on the previous slide, the US EPA Food Recovery Hierarchy15 ranks animal feeds produced by rendering above products of anaerobic digestion and composting in terms of effectiveness of resource recovery.
Summary comparison of GHG emissions and economic value of products
1000 kg
Process Meat Process
Utility GHG fuel by-products GHG
Utility Plant Electricity
Energy source
Conversion Process
Process products
Basis: 1000 kg of MBP processed Process Composting Rendering
Electricity, kWh <1 70
Process fuel, MJ 100 to 400 2300
Utility GHG, kg CO2e <1 40
Process GHG, kg CO2e 2500 to 4000 160
Total GHG, kg CO2e 2500 to 4000 200
800 800
Product 1 N in compost fat
amount, kg 10 to 20 200
value, $ 10 to 20 170
Product 2 none protein
amount, kg - 220
value, $ - 130
Total product value, $ 10 to 20 290 to 31040 to 70
CH4 in biogas
100 to 180
20 to 40
N in digestate
20 to 30
20 to 30
60 to 500
800Potential GHG if all C in meat by-products were converted to CO2
10
50 to 500
600
15 to 20
Anaerobic Digestion
Implications and conclusions
• Small farmers might favor composting as a method of disposing of carcasses along with manure because constructing and operating a compost pile costs less than constructing and operating an anaerobic digester and perhaps less than sending carcasses to an off-site rendering facility.
• For a large farm or feed lot, anaerobic digestion could be an attractive way to produce fuel and dispose of manure and a limited mass of carcasses relative to the mass of manure produced.
Implications and conclusions • With respect to biosecurity, environmental
sustainability, and resource recovery, rendering is clearly preferable to composting and anaerobic digestion as a method of handling large quantities of animal carcasses and meat by-products (MBP).
• To insure the health and safety of workers and the public as well as environmental responsibility, regulatory constraints must in place for all methods of meat by-product disposal that are allowed to exist.
• Within regulatory limitations, cost is likely to be the key factor that determines how individual producers of animal carcasses and MBP handle the material.
References cited 1. www.nationalrenderers.org/biosecurity-appi/code/
2. www.certifiedfacility.org/about_FCI/
3. www.fda.gov/AnimalVeterinary/SafetyHealth/AnimalFeedSafetySystemAFSS/
4. www.aphis.usda.gov/wps/portal/aphis/
5. www.fda.gov/Food/GuidanceRegulation/FSMA/ucm366510.htm
6. www.epa.gov/composting/laws/
7. CIWMB staff. Food waste composting regulations white paper, California Integrated Waste Management Board. 2009.
8. www.epa.gov/agstar/tools/permitting/
9. Gale, P. Risks to farm animals from pathogens in composted catering waste containing meat, Vet. Rec. 155:77-82. 2004.
10. Berge, A. et al. Methods and microbial risks associated with composting of animal carcasses in the United States, JAVMA 234(1): 47-56. 2009.
11. Masse, D. et al. On farm biogas production: A method to reduce GHG emissions and develop more sustainable livestock operations, Anim. Feed. Sci. Tech. 166-67:436-445. 2011.
References cited 12. Gwyther, C. et al. The environmental and biosecurity characteristics of livestock carcass disposal methods: a review, Waste Manag. 31:767-778. 2011.
13. Franke-Whittle, I. and H Insam, Treatment alternatives of slaughterhouse wastes, and their effect on the inactivation of different pathogens: A review, Critical Rev. Microbiology, 39(2): 139–151. 2013.
14. Hejnfelt, A. and I. Angelidaki. Anaerobic digestion of slaughterhouse by-products, Biomass Bioenerg. 33:1046-1054. 2009.
15. www.epa.gov/foodrecovery/
16. Gooding, C. Data for the carbon footprinting of rendering operations, J. Industrial Ecology 16(2): 223-230. 2012.
17. Xu, S. et al. Greenhouse gas emissions during co-composting of cattle mortalities with manure, Nutr. Cycl. Agroecosys. 78: 177-187. 2007.
18. Xu, S. et al. Greenhouse gas emissions during co-composting of calf mortalities with manure, J. Environ. Qual. 36:1914-1919. 2007.
19. www.eia.gov/tools/faqs/
References cited 20. www.nrel.gove/lci/
21. Swisher, K. Market report, Render 44(2): 10-16. 2015.
22. Gulliver, J. and D. Gulliver. On-site composting of meat by-products. Final report: New York State Department of Economic Development, October 2001.
23. Solomon, S. et al. Technical summary of contribution of working group I to the 4th assessment report of the IPCC. Cambridge University Press. 2007.
24. www.ers.usda.gov/data-products/fertilizer-use-and-price.aspx/
25. Angelidaki, I. and W. Sanders. Assessment of the anaerobic biodegradability of macro pollutants. Reviews Environ. Sci. and Bio/Tech. 3:117–129. 2004.
26. Meroney, R. CFD simulation of mechanical draft tube mixing in anaerobic digester tanks, Water Research 43, 1040-1050. 2009.
27. Ek., A. et al. Slaughterhouse waste co-digestion - Experiences from 15 years of full-scale operation, World Renewable Energy Congress Sweden. 2011.
28. Liebetrau, J. et al. Analysis of greenhouse gas emissions from 10 biogas plants within the agricultural sector. Water Sci. and Tech. 76(6), 1370-1379. 2013.
Acknowledgements The work described here was funded by the Fat and
Protein Research Foundation and was facilitated by many helpful discussions with
David Meeker, FPRF and NRA
Ross Hamilton, Darling Intl.
David Kirstein, Darling Intl.
Jessica Meisinger, NRA
David Carey, a 2014 Clemson chemical engineering graduate, did much of the original collection, screening, and analysis of greenhouse gas emission data from composting.
