Influence Of Low-Lipid Microalgae On Synergism During Catalytic And Non-Catalytic (Co-) Pyrolysis With Organic Solid Wastes

Biomass,next to coal,petroleum and natural gas,biomass is currently the fourth largest primary energy source.A wide range of biomass sources including plant-based materials,aquatic biomass,municipal solid waste(MSW),industrial wastes,manure,sewage are few promising sources in this perspective.In the recent years,much research is being focused on developing algae based biorefinery owing to their numerous advantages.On the other side,solid waste has also been considered as an important resource of bioenergy.In countries like China,it is reported that animal manure is one of the major source of water pollution,mainly through the transfer of nitrogen(N)and phosphorus(P).The use of solid wastes as bioenergy feedstock could reduce waste disposal problems and alleviate pressure on environment by providing clean energy.Pyrolysis is one of the most widely applied method used to convert biomass into high-energy content fuels,which can later be used for internal combustion engines and gas turbines after an intermediate process.However,co-pyrolysis and catalytic pyrolysis help improve the nature,quantity and quality of the end products and can synergistically improve the rate of biomass decomposition.In this regards,synergistic interaction between feedstock during co-pyrolysis is an important aspect of research.In the present study,an attempt has been made to investigate the synergistic influence of microalgae over organic solid waste and vice versa.The composition of aquatic microlage and organic solid waste(OSW)are entirely different and there exist a huge possibility of one feedstock influencing the other either synergistically or antagonistically.Three different species of microalgae,namely Spirulina platensis(SP),Chlorella vulgaris(CV)and Chroococcus sp.(CC),and three varities of organic solid waste(OSWs),namely municipal solid waste(MSW),digested municipal solid waste(DMSW)and digested swine manure(SWD)were pyrolysed from ambient temperature to 800? in a thermogravimetric analyser coupled with mass spectrometer.The initial analysis identified two microalgae,Spirulina platensis(SP)and Chlorella vulgaris to be thermally sensitive and the other microalge Chroococcus sp.to be thermaly resistant.With OSWs,municipal solid waste(MSW)was thermally sensitive while the digested forms of MSW and swine manure(SWD)were thermally resistant.The residues left at the end of pyrolysis for microalgae samples ranged from 20-55%,depending up on the species.For OSW smaples,depending up on the form of OSW,the residues ranged from 19-55%.The activation energies for microalgae samples were in the range of 167.4-170.93,224.6-223.8 and 282.11-283.2 k J mol^-1 for SP,CV and CC,respectively.For OSW sampels,the activation energies were in the range of 172.3-173.02,202.6-202.2 and 215.2-213.8 k J mol^-1 for MSW,DMSW and SWD,respectively.Based on the results from the initial analysis,two microalgae,SP and CC,and two OSWs,MSW and DMSW,were selected and synergy was evaluated at different blending ratios of microalgae,considering thermal and kinetic behavior and gas yields as evaluation criteria.When thermally sensitive microalgae,SP,was co-pyrolysed with MSW and DMSW,the synergy was noticed with blends SM-3 and SD-2,which contained SP:MSW and SP:DMSW at ratios 75:25 and 50:50%wt,respectively.The experimental degradation was higher in either cases and the residue left for SM-3 and SD-2 were 19.7 and 33.4%.When compared to calculated residues for SM-3 and SD-2,which were 27.2 and 39.1%,respectively the experimentally derived residues were significantly low.The experimental activation energy(E_?)for SM-3 and SD-2(144.46 and 157.45 k J mol^-1,respectively),when compared with the calculated E_?(168.63 for SM-3 and 184.97 k J mol^-1for SD-2)were much lower,indicating the possible synergistic effect.In the other case,where CC was co-pyrolysed with MSW and DMSW,the trends of synergy appeared to raise as the proportion of CC was increased from 25 to 75%.However,for blends derived from CC and MSW,there was synergy noticed with CM-3(CC:MSW=75:25 wt.%).For CC with DMSW,synergy existed in all the three blends The calculated and experimental average E_?values for CM-3 and CD-3 were 254.66 and 204.35 and 262.22 and 139.98 k J mol^-1,respectively.Though the TG profiles haven't indicated the presence of synergy with CC-MSW blends,the?W(difference between calculated and experimental results)values were always noticed to be negative,implying a chance for synergy,which was further justified by kinetic analysis.The influence of bifunctional material on further improving the pyrolysis products for the blends,that had significant synergy,was investigated.The results indicated that the additive material had mixed results.The thermal profiles and gas yields were significantly enhanced,but the kinetics of the co-pyrolysis were impeded.