Enhanced biogas production from spirulina plantensis: pretreatment and co-digestion with cassava pulp | |
| Author | Wagle, Nisha |
| Call Number | AIT Thesis no.EV-16-11 |
| Subject(s) | Biogas Biomass energy Renewable energy sources Spirulina. |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-16-11 |
| Abstract | Renewable energy can be generated from microalgae from biogas generation or generation of other biofuels. Anaerobic digestion of algae generates a clean and renewable energy biogas, but faces problem due to resistant cell wall and inappropriate C/N ratio. Spirulina plantensis, blue green microalgae was used for biogas generation in this study. The optimum pretreatment and appropriate C/N ratio is important for the success of overall process. In this study, batch assay was conducted to assess the effectiveness of pretreatment and balanced nutrient ratio on the biogas production. Spirulina plantensis was subjected to thermal(<100°C), chemical (H2SO4) and thermochemical (H2SO4, 120°C) pretreatment. Biomass solubilisation after pretreatment was evaluated in terms of sCOD. Increase in sCOD due to increase in pretreatment temperature and concentration was achieved, with 49% increase in sCOD was obtained from the biomass pretreated with 2.5% H2SO4 and 120°C. Increased solubilisation did not lead to proportional increase in biogas production. Maximum biogas volume was achieved from biomass subjected to thermal pretreatment at 60°C, which is 24% increase as compared to the untreated biomass. Inhibitory ammonia concentration was not recorded in a batch test. The energy ratio for thermal pretreatment, Eo/Ein ranged from 0.61 to 0.81, while for thermochemical pretreatment Eo/Ein ranged from 0.08 to 0.35.C/N ratio in Spirulina plantensis was very less (4.3), hence C/N ratio was adjusted using cassava pulp as co-substrate with pretreated biomass (60°C), in order to enhance biogas production. Three C/N ratio’s 15, 20 and 25 was evaluated in a batch test. The appropriate C/N ratio for anaerobic co-digestion was found to be 25 with 56 % increase in biogas compared to untreated biomass. Co-digestion maintains the nutrient requirement for Anaerobic Digestion and enhances biogas yield. Interest in bio-refinery approach has increased nowadays. Lipid extracted residue after biodiesel production still contains carbohydrates and proteins, as a result, lipid extracted residue was also investigated in batch test for biogas production. Result shows 7% increase in biogas compared to control biomass. Thus, lipid extraction can be pretreatment prior to biogas generation step. |
| Year | 2016 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Annachhatre, Ajit P.; |
| Examination Committee(s) | Nguyen, Thi Kim Oanh;Loc, Thai Nguyen; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2016 |