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Free ammonia pretreatment improves anaerobic methane generation from algae
Qilin Wang1, Jing Sun2, Sitong Liu3
1Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Ultimo, NSW, 2007, Australia; Advanced Water Management Centre, The University of Queensland, St Lucia, QLD, 4072, Australia.
Water Research
|July 8, 2019
Summary
Free ammonia (FA) pretreatment significantly enhances anaerobic methane generation from algae by improving biodegradability. This novel closed-loop technology boosts algae solubilization and methane production potential, making algal biomass a more viable energy source.
Area of Science:
- Environmental Science and Engineering
- Biotechnology
- Renewable Energy
Background:
- Algal biomass is a promising feedstock for anaerobic digestion, but its low biodegradability limits methane generation efficiency.
- Pretreatment methods are crucial for overcoming the recalcitrance of algal biomass and enhancing biogas production.
- Free ammonia (FA) has emerged as a potential pretreatment agent for improving the anaerobic digestion of organic matter.
Purpose of the Study:
- To investigate the efficacy of a novel free ammonia (FA) pretreatment technology for enhancing anaerobic methane generation from secondary effluent-cultivated algae.
- To quantify the impact of FA pretreatment on algae solubilization and biochemical methane potential.
- To analyze the effect of FA pretreatment on the hydrolysis rate and methane yield of different biodegradable fractions within the algal biomass.
Main Methods:
- Algae cultivated in secondary effluent were subjected to free ammonia (FA) pretreatment at concentrations ranging from 240-530 mg NH3-N/L for 24 hours.
- Algae solubilization was assessed by measuring soluble chemical oxygen demand (SCOD) and total chemical oxygen demand (TCOD).
- Biochemical methane potential (BMP) tests were conducted to determine the hydrolysis rate (k) and ultimate methane yield (P0) of pretreated and untreated algae.
Main Results:
- FA pretreatment at 240-530 mg NH3-N/L significantly increased algae solubilization to 0.05-0.06 g SCOD/g TCOD, compared to 0.01 g SCOD/g TCOD for untreated algae.
- The hydrolysis rate (k) of algae increased from 0.21 d⁻¹ to 0.33-0.50 d⁻¹, and the biochemical methane potential (P0) increased from 132 L CH4/kg TCOD to 140-154 L CH4/kg TCOD after FA pretreatment.
- FA pretreatment enhanced the hydrolysis rate of both quickly and slowly biodegradable substrates and increased the methane yield of slowly biodegradable fractions, while slightly reducing that of quickly biodegradable fractions.
Conclusions:
- Free ammonia pretreatment is an effective technology for substantially enhancing algae solubilization and anaerobic methane generation.
- The FA pretreatment improves the overall biodegradability of algal biomass, leading to higher methane yields.
- This closed-loop FA technology offers a promising strategy for valorizing algal biomass into biogas.
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