Thermogravimetric and kinetic analysis to discern synergy during the co-pyrolysis of microalgae and swine manure digestate

Abstract

Background Co-pyrolysis of wastes with other feedstock can synergistically improve the rate of biomass decomposition and also help to resolve the issues related to limited availability feedstock. In this regards, synergistic interaction between feedstock during co-pyrolysis is an important aspect of research. As the constituents of aquatic and lignocellulosic biomass are different, and the decomposition pattern of aquatic biomass is dissimilar when compared to lignocellulosic biomass, it is important to understand whether these two biomasses interact during co-pyrolysis. Results Synergism in the co-pyrolysis of microalgae (MA), swine manure digestate (SWD), and their blends (MA/SWD) (w/w %), 2.5/7.5 (MD-1), 5/5 (MD-2), and 7.5/2.5 (MD-3), was evaluated based on decomposition behavior, gas yields, extent of thermal degradation, and kinetics. Extractives and volatiles in biomass enhanced the reaction kinetics and products yields, as indicated by the reduction in apparent activation energy of the blends, accompanied by an increase in H 2 , total gas yield, and extent in degradation. Thermogravimetric data, via isoconversional methods, were interpreted to achieve the apparent activation energies for the thermal degradation of the MA, SWD, and their blends. The best fit reaction models were identified using compensation effect and generalized master plots methods. Semi-quantitative method was used to quantify the evolved gas species. H 2 , CO, and CO 2 were noted to be the dominant gases, implying that tar cracking and reforming reactions were predominant. Conclusions Overall, synergy was noticed with respect to the pyrolysis of SWD biomass to gas products in the presence of MA biomass, whereas synergy was witnessed up to 50 w/w % MA in view of kinetic parameters as evaluation criteria.

Pyrolysis of Solid Digestate from Sewage Sludge and Lignocellulosic Biomass: Kinetic and Thermodynamic Analysis, Characterization of Biochar

“…No data for E α of digestates composed of SS and lignocellulosic biomass can be found in the literature. Nevertheless, some correlations could be made with swine manure digestate [45], corn stover digestate [88], roadside grass digestate [85], and other lignocellulosic rich digestates [25,44]. As shown in Table 4, the E α varied greatly with the type of feedstock.…”

“…The A values for digestates D1 and D2 were at lower conversion levels <10 9 1/s, while at conversion levels above 0.4 they were >10 9 1/s. This behavior indicates a multi-phase reaction due to the complex nature of these feedstocks, where degradation is slower and the reactions require more energy and a higher rate of molecular collisions [45]. Therefore, higher values of A indicate a simple complex [86].…”

“…The feedstock with the highest ∆H was digestate D2 (65-397 kJ/mol, calculated by the FWO method). For comparison, the ∆H of the swine manure digestate in one of the earlier studies ranged between 179 and 219 kJ/mol [45]. Otherwise, ∆H represents the total energy required for pyrolysis of biomass and its conversion into final products such as biogas, bio-oil and biochar [41].…”

“…The nth-order reaction model was used to calculate the activation energy and pre-exponential factor for sewage sludge digestate pyrolysis and combustion [34]. In contrast to sewage sludge digestates, kinetic studies dedicated to lignocellulosic digestates [25,44] and swine manure digestate [45] are more widely available.…”

Influence of microalgae on synergism during co-pyrolysis with organic waste biomass: A thermogravimetric and kinetic analysis

“…[1] Owing to facts such as depletion of fossil fuels, rises in greenhouse gases emissions, the research in the last few decades has been directed to identify alternative energy resources [2]. Biofuels generated from sources like biomass are considered to be ideal substitutes to traditional fossil-based fuels and are extensively studied in the recent past [3][4][5]. Additionally, legislation of biofuels, in many developed countries, as renewable fuel standard and renewable portfolio standard has been done to promote their early adoption [6].…”