Comparison of suspended versus immobilized digested sludge for 2-stage anaerobic digestion of algae. (15th June 2023)

• Record Type: Journal Article
• Authors: Abimbola, Tobi; Christodoulatos, Christos; Lawal, Adeniyi
• Is Part Of: Chemical engineering science. Volume 274(2023)
• Publication Date: 2023-06-15
• Subjects: Biohythane -- Calcium-alginate beads -- Diffusivity -- Partition coefficient -- Digested-sludge-loaded gels; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2023.118694
• Languages: English
• ISSNs: 0009-2509

Abstract

Graphical abstract: Highlights: Immobilized reactor improved bioCH4 yield by 2.6 times compared to suspended system. Recovered digestate produced 72% of bioCH4 released from single-stage digestion. Extra H2 produce in the 1st stage of 2-stage AD can improve overall fuel quality. Diffusion of glucose into beads was longest in beads generated from 4%w/v Na-alg. Uptake of glucose took about 35 mins to equilibrate for all cases of beads tested. Abstract: A 2-stage anaerobic digestion (AD) approach to extract biogas from algae using microbes immobilized in calcium-alginate (CA) beads is demonstrated here for the first time. The biomethane released from the 2nd stage of AD is 61% and 72% of the yield from single-stage AD, digesting whole alga and Post-Extracted Algae Residue (PEAR) of S.obliquus, respectively. However, additional 56scc/gVS and 32scc/gVS of biohydrogen produced from the 1st stage of AD makes the 2-stage AD more energy efficient. Adopting glucose as a model compound, the mass transfer behavior of the substrates in CA was studied. Diffusion time and diffusivity of glucose increased with increase in sodium alginate concentration while higher diffusivities of glucose were obtained in digested-sludge-loaded beads due to exclusion effect. The AD reaction is rate-limiting. The data in this work can be used to predict the residence time of substrates in packed bed reactors filled with microbes encapsulated in CA.