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Production of Microalgal Slow-Release Fertilizer by Valorizing Liquid Agricultural Digestate: Growth Experiments with Tomatoes

Authors :
Raquel Jimenez
Giorgos Markou
Saida Tayibi
Abdellatif Barakat
Camille Chapsal
Florian Monlau
Source :
Applied Sciences, Vol 10, Iss 11, p 3890 (2020)
Publication Year :
2020
Publisher :
MDPI AG, 2020.

Abstract

Anaerobic Digestion (AD) is a process that is well-known and fast-developing in Europe. AD generates large amounts of digestate, especially in livestock-intensive areas. Digestate has potential environmental issues due to nutrients (such as nitrogen) lixiviation or volatilization. Using liquid digestate as a nutrient source for microalgae growth is considered beneficial because digestate could be valorized and upgraded by the production of an added value product. In this work, microalgal biomass produced using liquid digestate from an agricultural biogas plant was investigated as a slow-release fertilizer in tomatoes. Monoraphidium sp. was first cultivated at different dilutions (1:20, 1:30, 1:50), in indoor laboratory-scale trials. The optimum dilution factor was determined to be 1:50, with a specific growth rate of 0.13 d−1 and a complete nitrogen removal capacity in 25 days of culture. Then, outdoor experiments were conducted in a 110 dm3 vertical, closed photobioreactors (PBRs) in batch and semi-continuous mode with 1:50 diluted liquid digestate. During the batch mode, the microalgae were able to remove almost all NH4+ and 65 (±13) % of PO43−, while the microalgal growth rate reached 0.25 d−1. After the batch mode, the cultures were switched to operate under semi-continuously conditions. The cell densities were maintained at 1.3 × 107 cells mL−1 and a biomass productivity around 38.3 mg TSS L−1 d−1 during three weeks was achieved, where after that it started to decline due to unfavorable weather conditions. Microalgae biomass was further tested as a fertilizer for tomatoes growth, enhancing by 32% plant growth in terms of dry biomass compared with the control trials (without fertilization). Similar performances were achieved in tomato growth using synthetic fertilizer or digestate. Finally, the leaching effect in soils columns without plant was tested and after 25 days, only 7% of N was leached when microalgae were used, against 50% in the case of synthetic fertilizer.

Details

Language :
English
ISSN :
20763417
Volume :
10
Issue :
11
Database :
Directory of Open Access Journals
Journal :
Applied Sciences
Publication Type :
Academic Journal
Accession number :
edsdoj.129cc03e04334670bc4f2150c440f74e
Document Type :
article
Full Text :
https://doi.org/10.3390/app10113890