The aim of this study was to evaluate the agricultural use of digestates obtained from laboratory-scale experiments of anaerobic co-digestion of different organic wastes (glycerol, compost from landfill, fish farm sludge, and catering waste and their mixes with sewage sludge) and from full-scale biogas plants (cattle slurry). The concentration of nitrogen, phosphorus, and heavy metals and presence of Salmonella spp. in digestates were monitored.
The co-digestion trials were performed using laboratory-scale reactors. The microbiological analyses of digestate showed the presence of Salmonella spp. in both the laboratory-scale reactors and samples taken from full-scale biogas plants. Some digestate samples highlighted the importance of the microbiological quality evaluation of the digestate in studying the possible health risks for consumers. The heavy metals concentrations did not exceed the maximum levels permitted by the Estonian Minister of the Environment Regulation No. 78 of 01.02.2003 ‘Requirements for the application of sewage sludge in agriculture, landscaping, and recultivation’. Although Cd concentration showed values lower than 3 mg/kg TS and Hg was only found in catering digestate, environmental contamination would be possible if digestates were used for agricultural purposes.
This work can be considered as a preliminary study in evaluating the possible agricultural use of the digestate obtained from the co-digestion of different organic wastes.
1. Nasir, M. I., Mohd Ghazi, T. I., and Omar, R. Production of biogas from solid organic wastes through anaerobic digestion: a review. Appl. Microbiol. Biotechnol., 2012, 95, 321–329.
https://doi.org/10.1007/s00253-012-4152-7
2. EREC. Renewable Energy Technology Roadmap: 20% by 2020. European Renewable Energy Council, 2008.
3. Bonetta, S., Bonetta, S., Ferretti, E., Fezia, G., Gilli, G., and Carraro, E. Agricultural reuse of the digestate from anaerobic co-digestion of organic waste: microbiological contamination, metal hazards and fertilizing performance. Water Air Soil Pollut., 2014, 225, 2046.
https://doi.org/10.1007/s11270-014-2046-2
4. Deublein, D. and Steinhauser, A. Biogas from Waste and Renewable Resources. An Introduction. WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008.
https://doi.org/10.1002/9783527621705
5. Kuusik, A., Loigu, E., Sokk, O., and Kuusik, A. Enhancement of methane productivity of anaerobic reactors of wastewater treatment plants. In World Academy of Science, Engineering and Technology, No. 65: WASET 2012 Tokyo, Japan, International Conference, May 29–30, 2012. WASET, 2012, 1191–1193.
6. Kuusik, A., Pachel, K., Kuusik, A., and Loigu, E. Assessment of landfill wastewater pollutants and efficiency of different treatment methods. Proc. Estonian Acad. Sci., 2016, 65, 452–471.
https://doi.org/10.3176/proc.2016.4.10
7. Yufang Wei, Xiujin Li, Liang Yu, Dexun Zou, and Hairong Yuan. Mesophilic anaerobic co-digestion of cattle manure and corn stover with biological and chemical pretreatment. Biores. Technol., 2015, 198, 431–436.
https://doi.org/10.1016/j.biortech.2015.09.035
8. Bonmatí, A. and Flotats, X. Pig slurry treatment strategy in a high livestock concentration area: anaerobic digestion as the key process. http://www.bvsde.paho.org/ bvsacd/unam7/pigslurry.pdf (accessed 2016-09-15).
9. Alkaya, E., Hande Erguder, T., and Demirer, G. N. Effect of operational parameters on anaerobic co-digestion of dairy cattle manure and agricultural residues: a case study for the Kahramanmaras, region in Turkey. Eng. Life Sci., 2010, 10, 552–559.
https://doi.org/10.1002/elsc.201000037
10. Søndergaard, M. M., Fotidis, I. A., Kovalovszki, A., and Angelidaki, I. Anaerobic co-digestion of agricultural byproducts with manure for enhanced biogas production. Energy Fuels, 2015, 29, 8088−8094.
https://doi.org/10.1021/acs.energyfuels.5b02373
11. Murto, M., Bjornsson, L., and Mattiasson, B. Impact of food industrial waste on anaerobic co-digestion of sewage sludge and pig manure. J. Environ. Manage., 2004, 70, 101–107.
https://doi.org/10.1016/j.jenvman.2003.11.001
12. Kuusik, A., Pachel, K., Kuusik, A., and Loigu, E. Anaerobic co-digestion of sewage sludge with fish farming waste. In 9th International Conference “Environmental Engineering”: Water Engineering. Vilnius, Lithuania. VGTU Press “Technika”, 2014, 1–8.
https://doi.org/10.3846/enviro.2014.084
13. Pitk, P., Kaparaju, P., and Vilu, R. Methane potential of sterilized solid slaughterhouse wastes. Biores. Technol., 2012, 116, 42–46.
https://doi.org/10.1016/j.biortech.2012.04.038
14. Kuusik, A., Loigu, E., Kuusik, A., and Sokk, O. Possibility of enhancing methane productivity in anaerobic reactors in the treatment of excess sludge from wastewater treatment plants. IJSEI, 2013, 2(12), 33–36.
15. Iqbal, S. A., Rahaman, S., Rahman, M., and Yousuf, A. Anaerobic digestion of kitchen waste to produce biogas. Procedia Engineering, 2014, 90, 657–662.
https://doi.org/10.1016/j.proeng.2014.11.787
16. Makádi, M., Tomócsik, A., and Orosz, V. Digestate: a new nutrient source – review. In Biogas (Kumar, S., ed.), InTech, 2012, 295–310, http://www.intechopen.com/ books/biogas/digestate-a-new-nutrient-source-review (accessed 2016-09-15).
17. Bernal, M. P., Alburquerque, J. A., de la Fuente, C., Clemente, R., Caravaca, F., Díaz-Pereira, E., et al. The probiogas project: an integrated approach of the anaerobic co-digestion of agricultural wastes for production of biogas and fertilisers. In Pre-Processing of Manure and Organic Waste for Energy Production, 2010.
18. Venglovsky, J., Martinez, J., and Placha, I. Hygienic and ecological risks connected with utilization of animal manures and biosolids in agriculture. Livestock Science, 2006, 102, 197–203.
https://doi.org/10.1016/j.livsci.2006.03.017
19. Engeli, H., Edelmann, W., and Fuchs, J. K. Survival of plant pathogens and weed seeds during anaerobic digestion. Water Sci. Technol., 1993, 27(2), 69–76.
20. Martens, W., Fink, A., Philipp, W., Weber, A., Winter, D., and Boehm, R. Inactivation of viral and bacterial pathogens in large scale slurry treatment plants. In Ramiran 98: Proceedings; International Conference on Management Strategies for Organic Waste Use in Agriculture, Sess. 8, Rennes (France), 26–29 May 1998 (Martinez, J. and Maudet, M.-N., eds). FAO, Rome (Italy). Agricultural Services Div., 1999, 529–539.
21. Carrington, E. G. Evaluation of sludge treatment for pathogen reduction – Final Report, WRc Ref: CO 5026/1, 2001. http://ec.europa.eu/environment/waste/ sludge/pdf/sludge_eval.pdf (accessed 2016-09-15).
22. Al Seadi, T. and Lukehurst, C. Quality Management of Digestate from Biogas Plants Used as Fertiliser. IEA Bioenergy, 2012.
23. Lukehurst, C. T., Frost, P., and Al Seadi, T. Utilisation of Digestate from Biogas Plants as Biofertiliser. IEA Bioenergy, 2010.
24. Riigikogu. Veeseadus [Water Act]. Riigi Teataja I, 27.12.2016, 6.
25. Holm, P. E., Jensen, L. S., and McLaughlin, M. J. Utilization of Biologically Treated Organic Waste on Land. Solid Waste Technology and Management (Christensen, T., ed.). Blackwell Publishing Ltd, 2010.
26. Handreichung. Biogasgewinnung und -nutzung. 3., revised edition. Fachagentur Nachwachsende Rohstoffe e. V., Gülzow, 2006.
27. Nyord, T., Søgaard, H. T., Hansen, M. N., and Jensen, L. S. Injection methods to reduce ammonia emission from volatile liquid fertiliser applied to growing crops. Biosystem Engineering, 2008, 100(2), 235–244.
https://doi.org/10.1016/j.biosystemseng.2008.01.013
28. Nutrient Value of Digestate from Farm-Based Biogas Plants in Scotland. Report for Scottish Executive Environment and Rural Affairs Department – ADA/009/06. July 2007.
29. Regulation (EC) No 1069/2009 of the European Parliament and of the Council of 21 October 2009. Official Journal of the European Union, 14.11.2009, L 300/1. http://data.europa.eu/eli/reg/2009/1069/oj (accessed 2016-09-15).
30. Al Seadi, T. Good practice in quality management of AD residues from biogas production. Report. University of Southern Denmark (SDU), Bioenergy Department Niels Bohrs Vej 9, DK-6700 Esbjerg, Denmark, IEA Bioenergy, 2001.
31. Keskkonnaministri 01.02.2003 määrus nr 78 “ Reoveesette põllumajanduses, haljastuses ja rekultiveerimisel kasutamise nõuded” [Minister of the Environment. Regulation No. 78 of 01.02.2003 ‘Requirements for the application of sewage sludge in agriculture, landscaping, and recultivation]. Riigi Teataja L, 2003, 5, 48 (in Estonian).
32. Keskkonnaministri 10.05.2016 määruse nr 12 “Nõuded biolagunevatest jäätmetest biogaasi tootmisel tekkivale kääritusjäägile” lisa 2 Kääritusjäägi ohutus- ja kvaliteedinäitajad [Minister of the Environment. Regulation No. 12 of 10.05.2016 ‘Requirements for the digestate from biogas production from biodegradable waste’, Annex 2: Digestate safety and quality indicators]. Riigi Teataja I, 19.05.2016, 9 (in Estonian).
Reoveesette töötlemise strateegia väljatöötamine, sh ohutu taaskasutamise tagamine järelevalve tõhustamise, keemiliste- ja bioloogiliste indikaatornäitajate rakendamise ning kvaliteedisüsteemide juurutamise abil. III ETAPP [Development of the strategy for the treatment of sewage sludge, including raising the effectiveness of monitoring safe recycling, application of chemical and biological indicators, and introduction of quality assessment systems. Stage III]. OÜ Eesti Keskkonnauuringute Keskus, 2012 (in Estonian).
