Different Pathways to Integrate Anaerobic Digestion and Thermochemical Processes: Moving Toward the Circular Economy Concept

Document Type : Review Article


1 School of Environment, College of Engineering, University of Tehran, Tehran, Iran

2 UNESCO Chair on Water Reuse, School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran


As one of the most environmentally friendly and cost-effective method, anaerobic digestion (AD) has been widely studied and developed as a conventional technology to degrade biodegradable materials and produce biogas simultaneously. Various substrate sources are used in this process such as organic fraction of municipal solid waste (MSW), waste activated sludge (WAS), animal manures, agro-industrial wastes, energy crops, micro- and macro-algae and etc. With the aim of process optimization, several publications have recently studied different configurations to integrate AD and thermochemical processes such as pyrolysis and gasification. These linking technologies seeks to optimize the use of products or by-products of thermochemical processes interchangeably. In this regard, this paper aims to review different potential pathways of feasible integration and coupling. Five hybrid pathways including biochar-amended anaerobic digestion, digestate-derived biochar and hydrochar, anaerobic digestion of aqueous phase liquid derived from pyrolysis and gasification of digestate were reviewed and their schematic diagram were presented. Despite several studies to combine AD with thermochemical valorization processes, further studies at the industrial scale are needed to prove the energy efficiency and economic viability of these coupling pathways.


Angelidaki, I., Karakashev, D., Batstone, D. J., Plugge, C. M., & Stams, A. J. (2011). Biomethanation and its potential. Methods Enzymol, 494(16), 327-351.
Antoniou, N., Monlau, F., Sambusiti, C., Ficara, E., Barakat, A., & Zabaniotou, A. (2019). Contribution to Circular Economy options of mixed agricultural wastes management: Coupling anaerobic digestion with gasification for enhanced energy and material recovery. Journal of cleaner production, 209, 505-514.
Appels, L., Baeyens, J., Degrève, J., & Dewil, R. (2008). Principles and potential of the anaerobic digestion of waste-activated sludge. Progress in energy and combustion science, 34(6), 755-781.
Aragón-Briceño, C., Ross, A. B., & Camargo-Valero, M. A. (2017). Evaluation and comparison of product yields and bio-methane potential in sewage digestate following hydrothermal treatment. Applied energy, 208, 1357-1369.
Atkinson, C. J., Fitzgerald, J. D., & Hipps, N. A. (2010). Potential mechanisms for achieving agricultural benefits from biochar application to temperate soils: a review. Plant and soil, 337(1-2), 1-18.
Chen, Y., Cheng, J. J., & Creamer, K. S. (2008). Inhibition of anaerobic digestion process: a review. Bioresource technology, 99(10), 4044-4064.
Chen, S., Rotaru, A. E., Liu, F., Philips, J., Woodard, T. L., Nevin, K. P., & Lovley, D. R. (2014). Carbon cloth stimulates direct interspecies electron transfer in syntrophic co-cultures. Bioresource technology, 173, 82-86.
Chen, G., Guo, X., Cheng, Z., Yan, B., Dan, Z., & Ma, W. (2017). Air gasification of biogas-derived digestate in a downdraft fixed bed gasifier. Waste management, 69, 162-169.
Cooney, M. J., Lewis, K., Harris, K., Zhang, Q., & Yan, T. (2016). Start up performance of biochar packed bed anaerobic digesters. Journal of Water Process Engineering, 9, e7-e13.
Correa, C. R., Bernardo, M., Ribeiro, R. P., Esteves, I. A., & Kruse, A. (2017). Evaluation of hydrothermal carbonization as a preliminary step for the production of functional materials from biogas digestate. Journal of Analytical and Applied Pyrolysis, 124, 461-474.
Fabbri, D., & Torri, C. (2016). Linking pyrolysis and anaerobic digestion (Py-AD) for the conversion of lignocellulosic biomass. Current opinion in biotechnology, 38, 167-173.
Fagbohungbe, M. O., Herbert, B. M., Hurst, L., Li, H., Usmani, S. Q., & Semple, K. T. (2016). Impact of biochar on the anaerobic digestion of citrus peel waste. Bioresource technology, 216, 142-149.
Funke, A., Mumme, J., Koon, M., & Diakité, M. (2013). Cascaded production of biogas and hydrochar from wheat straw: Energetic potential and recovery of carbon and plant nutrients. Biomass and bioenergy, 58, 229-237.
Garlapalli, R. K., Wirth, B., & Reza, M. T. (2016). Pyrolysis of hydrochar from digestate: Effect of hydrothermal carbonization and pyrolysis temperatures on pyrochar formation. Bioresource technology, 220, 168-174.
Geng, Y., Sarkis, J., Ulgiati, S., & Zhang, P. (2013). Measuring China's circular economy. Science, 339(6127), 1526-1527.
Gonzalez-Fernandez, C., Sialve, B., & Molinuevo-Salces, B. (2015). Anaerobic digestion of microalgal biomass: challenges, opportunities and research needs. Bioresource technology, 198, 896-906.
Holm-Nielsen, J. B., Al Seadi, T., & Oleskowicz-Popiel, P. (2009). The future of anaerobic digestion and biogas utilization. Bioresource technology, 100(22), 5478-5484.
Hung, C. Y., Tsai, W. T., Chen, J. W., Lin, Y. Q., & Chang, Y. M. (2017). Characterization of biochar prepared from biogas digestate. Waste Management, 66, 53-60.
Inyang, M., Gao, B., Pullammanappallil, P., Ding, W., & Zimmerman, A. R. (2010). Biochar from anaerobically digested sugarcane bagasse. Bioresource Technology, 101(22), 8868-8872.
Kan, X., Yao, Z., Zhang, J., Tong, Y. W., Yang, W., Dai, Y., & Wang, C. H. (2017). Energy performance of an integrated bio-and-thermal hybrid system for lignocellulosic biomass waste treatment. Bioresource technology, 228, 77-88.
Lee, B., Park, J. G., Shin, W. B., Tian, D. J., & Jun, H. B. (2017). Microbial communities change in an anaerobic digestion after application of microbial electrolysis cells. Bioresource Technology, 234, 273-280.
Lee, J. Y., Lee, S. H., & Park, H. D. (2016). Enrichment of specific electro-active microorganisms and enhancement of methane production by adding granular activated carbon in anaerobic reactors. Bioresource technology, 205, 205-212.
Lehmann, J., & Joseph, S. (Eds.). (2015). Biochar for environmental management: science, technology and implementation. Routledge.
Li, F., Cheng, S., Yu, H., & Yang, D. (2016). Waste from livestock and poultry breeding and its potential assessment of biogas energy in rural China. Journal of Cleaner Production, 126, 451-460.
Luo, C., Lü, F., Shao, L., & He, P. (2015). Application of eco-compatible biochar in anaerobic digestion to relieve acid stress and promote the selective colonization of functional microbes. Water research, 68, 710-718.
McKennedy, J., & Sherlock, O. (2015). Anaerobic digestion of marine macroalgae: A review. Renewable and Sustainable Energy Reviews, 52, 1781-1790.
Mohan, S. V., Nikhil, G. N., Chiranjeevi, P., Reddy, C. N., Rohit, M. V., Kumar, A. N., & Sarkar, O. (2016). Waste biorefinery models towards sustainable circular bioeconomy: critical review and future perspectives. Bioresource technology, 215, 2-12.
Mumme, J., Eckervogt, L., Pielert, J., Diakité, M., Rupp, F., & Kern, J. (2011). Hydrothermal carbonization of anaerobically digested maize silage. Bioresource technology, 102(19), 9255-9260.
Mumme, J., Srocke, F., Heeg, K., & Werner, M. (2014). Use of biochars in anaerobic digestion. Bioresource technology, 164, 189-197.
Nakason, K., Panyapinyopol, B., Kanokkantapong, V., Viriya-empikul, N., Kraithong, W., & Pavasant, P. (2018). Characteristics of hydrochar and hydrothermal liquid products from hydrothermal carbonization of corncob. Biomass Conversion and Biorefinery, 8(1), 199-210.
Nuchdang, S., Frigon, J. C., Roy, C., Pilon, G., Phalakornkule, C., & Guiot, S. R. (2018). Hydrothermal post-treatment of digestate to maximize the methane yield from the anaerobic digestion of microalgae. Waste management, 71, 683-688.
Peng, B., Chen, L., Que, C., Yang, K., Deng, F., Deng, X., ... & Wu, M. (2016). Adsorption of antibiotics on graphene and biochar in aqueous solutions induced by π-π interactions. Scientific reports, 6, 31920.Rajagopal, R., Massé, D. I., & Singh, G. (2013). A critical review on inhibition of anaerobic digestion process by excess ammonia. Bioresource Technology, 143, 632-641.
Reza, M. T., Mumme, J., & Ebert, A. (2015). Characterization of hydrochar obtained from hydrothermal carbonization of wheat straw digestate. Biomass Conversion and Biorefinery, 5(4), 425-435.
Salman, C. A., Schwede, S., Thorin, E., & Yan, J. (2017). Enhancing biomethane production by integrating pyrolysis and anaerobic digestion processes. Applied Energy.
Shen, Y., Linville, J. L., Urgun-Demirtas, M., Schoene, R. P., & Snyder, S. W. (2015). Producing pipeline-quality biomethane via anaerobic digestion of sludge amended with corn stover biochar with in-situ CO2 removal. Applied Energy, 158, 300-309.
Shen, Y., Linville, J. L., Ignacio-de Leon, P. A. A., Schoene, R. P., & Urgun-Demirtas, M. (2016). Towards a sustainable paradigm of waste-to-energy process: Enhanced anaerobic digestion of sludge with woody biochar. Journal of Cleaner Production, 135, 1054-1064.
Singlitico, A., Dussan, K., Oshea, R. (2017). Techno-economic Optimisation of Combined Anaerobic Digestion and Gasification of Food Waste as part of an Integrated Waste Management and Energy System. 25th European Biomass Conference and Exhibition.
Schnurer, A., & Jarvis, A. (2010). Microbiological handbook for biogas plants. Swedish Waste Management U, 2009, 1-74.
Stefaniuk, M., & Oleszczuk, P. (2015). Characterization of biochars produced from residues from biogas production. Journal of Analytical and Applied Pyrolysis, 115, 157-165.
Sun, L., Wan, S., & Luo, W. (2013). Biochars prepared from anaerobic digestion residue, palm bark, and eucalyptus for adsorption of cationic methylene blue dye: characterization, equilibrium, and kinetic studies. Bioresource Technology, 140, 406-413.
Sunyoto, N. M., Zhu, M., Zhang, Z., & Zhang, D. (2016). Effect of biochar addition on hydrogen and methane production in two-phase anaerobic digestion of aqueous carbohydrates food waste. Bioresource Technology, 219, 29-36.
Taghizadeh-Toosi, A., Clough, T. J., Sherlock, R. R., & Condron, L. M. (2012). Biochar adsorbed ammonia is bioavailable. Plant and Soil, 350(1-2), 57-69.
Torri, C., & Fabbri, D. (2014). Biochar enables anaerobic digestion of aqueous phase from intermediate pyrolysis of biomass. Bioresource technology, 172, 335-341.
Ward, A. J., Lewis, D. M., & Green, F. B. (2014). Anaerobic digestion of algae biomass: a review. Algal Research, 5, 204-214.
Yang, Y., Heaven, S., Venetsaneas, N., Banks, C. J., & Bridgwater, A. V. (2018). Slow pyrolysis of organic fraction of municipal solid waste (OFMSW): Characterisation of products and screening of the aqueous liquid product for anaerobic digestion. Applied energy, 213, 158-168.
Yao, Z., Li, W., Kan, X., Dai, Y., Tong, Y. W., & Wang, C. H. (2017). Anaerobic digestion and gasification hybrid system for potential energy recovery from yard waste and woody biomass. Energy, 124, 133-145.
Yao, Y., Gao, B., Inyang, M., Zimmerman, A. R., Cao, X., Pullammanappallil, P., & Yang, L. (2011). Biochar derived from anaerobically digested sugar beet tailings: characterization and phosphate removal potential. Bioresource technology, 102(10), 6273-6278.
Yenigün, O., & Demirel, B. (2013). Ammonia inhibition in anaerobic digestion: a review. Process Biochemistry, 48(5), 901-911.
Yin, Q., Zhu, X., Zhan, G., Bo, T., Yang, Y., Tao, Y., ... & Yan, Z. (2016). Enhanced methane production in an anaerobic digestion and microbial electrolysis cell coupled system with co-cultivation of Geobacter and Methanosarcina. Journal of Environmental Sciences, 42, 210-214.
Zhang, J., Fan, C., & Zang, L. (2017). Improvement of hydrogen production from glucose by ferrous iron and biochar. Bioresource Technology, 245, 98-105.
Zhao, Z., Zhang, Y., Holmes, D. E., Dang, Y., Woodard, T. L., Nevin, K. P., & Lovley, D. R. (2016). Potential enhancement of direct interspecies electron transfer for syntrophic metabolism of propionate and butyrate with biochar in up-flow anaerobic sludge blanket reactors. Bioresource technology, 209, 148-156.