Thermocatalytic Pyrolysis of Exhausted Arthrospira platensis Biomass after Protein or Lipid Recovery

Elena Spennati,Attilio Converti,Guido Busca,Alessandro Alberto Casazza

doi:10.3390/en13205246

Abstract

Microalgae and cyanobacteria are unicellular microorganism that contain high-added-value compounds. To make their extraction economically feasible, the biorefinery concept is the only solution. In this study, the residues resulting from lipid or protein extraction from Arthrospira platensis biomass were valorized by catalytic pyrolysis using ZSM5 zeolite or amorphous silica–alumina as catalyst. The reaction was performed in a quartz reactor, and the catalysts were placed in a fixed bed, to force the reaction gases to pass through it. The reaction products were analyzed by FTIR and GC–MS analyses. The reaction gases and liquids obtained from the extraction residues had higher hydrocarbon contents compared with the untreated biomass. Moreover, the pyrolysis of biomass after protein extraction led to fractions with lower nitrogenated component contents, while that after lipid extraction to fractions with lower oxygenated component contents. This study showed that the pyrolysis process could be used to valorize the microalgae extraction residues, aiming to make biofuels production and extraction of high-added-value products more economically feasible.

Highlights

The growing industrialization, the high level of pollution, and the reduction of resources have led to an urgent need to find an alternative way to handle entire production chains from raw materials to finished products
The biorefinery concept, according to which biomass is converted into high-added-value products, reaction intermediates, and biofuels, is a sustainable alternative to that of a conventional refinery
G was mainly composed of incondensable gases (light gases and short chain classified as reaction gas (G), light reaction liquid (LL), heavy reaction liquid (HL), liquid residue hydrocarbons); LR of long chain hydrocarbons (C > 6), oxygenates

Summary

Introduction

The growing industrialization, the high level of pollution, and the reduction of resources have led to an urgent need to find an alternative way to handle entire production chains from raw materials to finished products. The zero-waste strategy and the circular economy are the best solutions to remediate the dramatic conditions in which our planet is located In this context, the biorefinery concept, according to which biomass is converted into high-added-value products, reaction intermediates, and biofuels, is a sustainable alternative to that of a conventional refinery. Microalgae and cyanobacteria have in recent years become attractive because of their multiple applications in different fields They are generally used in human or animal nutrition, biofuel production, and extraction of high-added-value components for chemical, cosmetic, and pharmaceutical industries [2]. Due to their multiple applications, they are a promising raw material for biorefinery [3] Such unicellular microorganisms composed mainly of lipids, proteins, and carbohydrates, whose relative proportions depend mainly on the species and growth conditions, have higher growth rates compared to higher plants and can be cultivated in marginal lands, seas, and fresh water. Their capability to grow under drastic conditions and in land not used for agriculture is an answer to the food vs. fuel conflict [4]

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Conclusion