Title:
Enhancing Carbon Recovery in SCOS and Biomethane Production through Sequential Fermentation and Anaerobic Digestion of Residual Streams
Author(s):
Albergo, R., Limonti, C., Turano, N., Caporusso, A., Valerio, V., Viola, E., De Bari, I.
Document(s):
Paper
Poster
Abstract:
In the framework of circular bioeconomy and integrated biorefinery concepts, the efficient valorisation of residual streams represents a key challenge to improve process sustainability and carbon utilization. In our previous study presented at the last EUBCE, microbial oil production from sugarcane molasses supplemented with crude glycerol was optimized and scaled up, leaving a residual fermentation broth still containing significant amounts of unconsumed carbon sources. In this work, the residual stream, characterized by approximately 50 g/L of crude glycerol and 10 g/L of mannitol, was further valorised through a secondary fermentation step using the oleaginous yeast Rhodosporidium toruloides. The aim of this work was to enhance overall carbon recovery and increase lipid production by exploiting remaining substrates. Batch fermentation experiments demonstrated the complete consumption of crude glycerol, while mannitol remained largely unutilized under the tested conditions, indicating substrate selectivity of the strain. Biomass yields reached approximately 0.31 g/g of crude glycerol, with 25% of intracellular lipid accumulation with a concomitant non-negligible production of carotenoids. Chemical analysis revealed a triglyceride-rich oil, predominantly composed of linoleic (67%), stearic acid (15%) and oleic acid (12%), showing a composition like vegetable oils and indicating its potential suitability for production of HVO. The obtained results confirm the suitability of R. toruloides for the efficient conversion of residual glycerol streams into single cell oils (SCOs), enabling a sequential fermentation strategy. This approach significantly improves overall process efficiency by maximizing carbon valorisation and reducing waste generation. In parallel, the residual stream, is subjected to anaerobic digestion for biogas production, enabling additional energy recovery. To investigate the effect of spent broth on methanogenic activity and overall anaerobic digestion efficiency, a series of batch BMP assays was conducted using three reactors operated at different substrate-to-inoculum (S/I) ratios. The best cumulative biomethane was obtained when S/I ration is 0.6. This integrated approach contributes to a near-complete valorisation of the carbon stream, further enhancing the sustainability of the overall biorefinery process. The proposed integration of primary and secondary fermentation steps, coupled with anaerobic digestion, represents a promising strategy for the development of sustainable and economically viable biorefinery processes based on industrial by-products.
Keywords:
anaerobic digestion, crude glycerol, single cell oils, lipomyces tetrasporus, rhodosporidium toruloides sugarcane molasses
Topic:
Biomass, Bio-based Products and Bioenergy Integration
Subtopic:
Integrated biorefineries for co-production of biofuels, biochemicals and bio-based products
Event:
34th European Biomass Conference and Exhibition
Session:
3CV.4.31
Pages:
500 - 505
ISBN:
978-88-89407-27-1
Paper DOI:
10.5071/34thEUBCE2026-3CV.4.31
Price:
FREE
