Pyrolysis of Algal Biomass Obtained from High-Rate Algae Ponds Applied to Wastewater Treatment

Fernanda Vargas E Silva,Luiz Olinto Monteggia

doi:10.3389/fenrg.2015.00031

Fernanda Vargas E Silva, Luiz Olinto Monteggia

Open Access

https://doi.org/10.3389/fenrg.2015.00031

Copy DOI

Abstract

This work presents the results of the pyrolysis of algal biomass obtained from high rate algae ponds treating sewage. The two high-rate algae ponds (HRAP) were built and operated at the Sao Joao Navegantes Wastewater Treatment Plant. The HRAP A was fed with raw sewage while the HRAP B was fed with effluent from an Upflow Anaerobic Sludge Blanket (UASB) reactor. The HRAP B provided higher productivity, presenting total solids concentration of 487.3mg/l and chlorophyll a of 7735mg/l. The algal productivity in the average depth was measured at 41,8 gm-2day-1 in pond A and at 47.1 gm-2day-1 in pond B. Algae obtained from the HRAP B were separated by the process of coagulation/flocculation and sedimentation. In the presence of alum, a separation efficiency in the range of 97% solids removal was obtained. After centrifugation the biomass was dried and comminuted. The biofuel production experiments were conducted via pyrolysis in a tubular quartz glass reactor which was inserted in a furnace for external heating. The tests were carried out in an inert nitrogen atmosphere at a flow rate of 60ml/min. The system was operated at 400°C, 500°C and 600°C in order to determine the influence of temperature on the obtained fractional yields. The studies showed that the pyrolysis product yield was influenced by temperature, with a maximum liquid phase (bio-oil and water) production rate of 44% at 500°C, 45% for char and around 11% for gas.

Highlights

Biomass is considered worldwide as an important source of renewable energy, including electricity, automobile fuel, and as a source of heat for industrial equipment.Cultures commonly used for energy production are sugarcane, corn, beans, beets, and many others
The high-rate algae ponds were operated under two feeding conditions: pond A was fed with raw sewage after pretreatment and pond B was fed with effluent from an upflow anaerobic sludge blanket (UASB) reactor
We considered the concentration of solids present in effluents and turbidity caused only by the presence of algae

Summary

Introduction

Biomass is considered worldwide as an important source of renewable energy, including electricity, automobile fuel, and as a source of heat for industrial equipment.Cultures commonly used for energy production are sugarcane, corn, beans, beets, and many others. There are two main factors that define when a culture is appropriate for this process: good dry matter yield per unit of land (dry ton/ha), low area requirement for cultivation, and low costs of energy production from biomass (Dermibas et al, 2009). Among the aquatic biomass feedstocks, are considered one of the most promising sources of biofuels due to their unique characteristics. They can accumulate lipids that can be converted into biofuels, present fast proliferation, have the ability to sequester CO2 from the atmosphere for growth and do not require agricultural land or freshwater for growth or higher water consumption, and the whole plant matter can be used in converting biofuels processes

Methods

Results

Conclusion