revalorization of solid waste microalgae biomass from pig manure water treatment towards fertilizers production

Revalorization of solid waste microalgae biomass from pig manure water treatment

towards fertilizers production

J. Martín-Juárez1_{, A. Lorenzo-Hernando}1 _{and S. Bolado-Rodríguez}1

1_{Department of Chemical Engineering and Environmental Technology, University of Valladolid, Valladolid,}

47011, Spain

Keywords: pretreatment, fertilizer, microalgae, anaerobic, wastewater Presenting author email: [email protected]

The use of microalgae is growing in different applications in the last decades. Pharmaceuticals, cosmetics, animal feed, biofuels, chemicals, wastewaters treatment and fertilizers production are several fields that they are being applied. This is not only due to the current oil crisis, but also to the necessity of new energy sources with the aim of having feasible and environmental friendly processes. The microalgae seem to be an effective option for the agro-food wastewater treatment with high nutrient contents. The wastewater is treated and converted into an effluent that could be returned with minimal environmental issues or reused. The nutrients accumulation (N and P) in the biomass, which was produced in this process of treatment, becomes an attractive residue for its possible valorization (Singh et al., 2016).

The production of biogas is one of the tendency for this biomass, and the maximum theoretical yield is 0.40L CH4/g SV, considering the whole microalgae biomass. This reduced digestibility is attributed to the strong

structure of its cell wall and to the presence of recalcitrant compounds, hence, it is necessary to apply different pretreatments to break the cell wall and increase the biomass biodegradability. The use of obtained digestate solid (after the anaerobic digestion) as a fertilizer is an interesting alternative. Europe requires annually of 11 Mton N, 2.8 Mton phosphorus and 2.6 Mton of potassium, of which a significant percentage is imported. The use of microalgae for the fertilizers production could generate new business opportunities and would be an important advantage for the European economic sector (BBI, 2016).

Therefore, this work aims at implementing the biorefinery concept by valorizing the microalgae biomass produced from pig manure wastewater treatment as a substrate for biogas production through anaerobic digestion. Furthermore, several pretreatments are applied to improve the CH4 methane production. The obtained

digestate solid is used in a new subsequent revalorization for fertilizer production.

The microalgae biomass was obtained from pig manure treatment in thin layer reactor and Scenedesmus sp. was the principal microalgae specie. The biomass content was 47% C, 7% N and 0.5% P. The pretreatments that are used for the sugars release and cell wall rupture are: ball mill (three ball sizes, 5 to 60 min), alkaline (1M a 5M de NaOH, 5 to 60 min in autoclave), peroxide-alkaline (1 a 5% H2O2, pH 11.5 adjusted with 2M NaOH,

50ºC, 120 rpm, 60 min) and steam explosion (130 to 170ºC, 5 to 30 min, in 5L reactor and another tank to perform the decompression suddenly). All experiments were performed with 5% dry weight of algal biomass. The pretreated biomass is cooled to room temperature and the solid fraction is separated by centrifugation (10 min, 10000 rpm). The liquid and the solid are maintained at 4 °C. The mass loss of solids by solubilization and the composition in terms of sugars, alcohols, organic acids, furfural, hemifurfural and acetone of the liquid pretreatment fraction are analyzed. Humidity, ash, carbohydrates, lipids and proteins are also analyzed in the pretreated solid phase.

Methane production tests have been carried out with the pretreated solid fraction and pretreated solid and liquid fractions under the same conditions at 35 °C in a laboratory thermostatic chamber, maintaining a ratio of 0.5 g VSsubstrate/g VSinoculum. The serum bottles used for this tests were 160 mL with a useful volume of

approximately 100 mL (adding water if necessary). The digestate of the wastewater plant of Valladolid was used as inoculum. The bottles were passed through helium and incubated at 35 °C until the biogas production remained constant. The biogas production is periodically determined by measuring the increment in pressure through a PN 5007 manometer (IFM, Germany), after each measurement the bottles are left at atmospheric pressure. To determine the biogas composition, head space volumes are sampled by gas chromatography using Varian CP-177 3800 GC-TCD equipped with CP-Molsieve 5A and CP-Pora BOND Q columns using helium as gas. A blank is made using only inoculum to quantify the amount of methane produced by endogenous respiration.

limiting step. There are several models of the kinetic analysis of biogas production process; it all depends on the types of substrate used for anaerobic digestion and the controlling step. The Gompertz model considers inhibition behavior of the anaerobic digestion process, and estimates the kinetic parameters; biogas yield potential, duration of the lag phase, and maximum biogas production rate. Nevertheless, the first order model is used when the hydrolysis reaction is the rate limiting step of the overall process, and estimate the extent of the reaction, and the hydrolysis constant. Moreover, the model parameters are calculated by minimizing the least square difference between observed and predicted values (Passos et al., 2015).

𝐵 = 𝐵 · [1 − exp (−𝑘 · 𝑡)] (Eq. 1)

𝐵 = 𝐵 · exp −exp · (𝜆 − 𝑡) + 1 (Eq. 2)

In these equations, B represents the cumulative methane production (mL CH4/gVS) and t is the assay

length of the assay (d). These models estimate the methane production potential B0 (mL CH4/g VS, related to the

substrate biodegradability), the hydrolysis coefficient kH (d-1), the maximum biogas production rate Rm (mL

CH4/g VS·d), and the lag time  (d).

The results are reporting an increase of the biodegradability up to 60% when the pretreatments are applied compared with the control (untreated biomass) and around 400 mL CH4/g VS microalgae. The obtained

digestate solid has approximately 70-80% dry solid content and humidity between 20-30%. The main parameters that determine its quality are pH, TOC, humidity, total solids, total nitrogen, total phosphorus, Mg and K content, heavy metals (Ni, Cd, Hg, Pb), biuret (C2H5N3O2), polychlorinated biphenyls (PBCs) and the pathogen

content (Escherichia coli, Salmonella) (Dogan-Subasi E. and Demirer G.N.).

ACKNOWLEDGEMENTS

This work was supported by the research unit UIC 071 of the regional government “Junta de Castilla y León – JCyL”, Spain. The authors thank “Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria – INIA”, “Ministerio de Economía y Competitividad – MINECO” (RTA2013-00056-C03-02) supported by FEDER program, and “Junta de Castilla y León – JCyL” (VA094U14) for the financial support of this work. Judit Martin wish to thank “Junta de Castilla y León – JCyL” for providing her Doctorate Scholarship and Ana Lorenzo wish to thank “Universidad de Valladolid - UVa” for her Doctorate Scholarship.

REFERENCES

BBI. Bio-Based Industries Public-Private Partnership. [http://www.bbi-europe.eu/], consulted in December 2016 (2016).

Dogan-Subası, E., Demirer, G.N. Anaerobic Digestion of Microalgal (Chlorella vulgaris) Biomass as a Source of Biogas and Biofertilizer. Environmental Progress and sustainable Energy 35, pp 936-941. (2016).

Passos, F., Carretero, J. Ferrer, I. Comparing pretreatment methods for improving microalgae anaerobic digestion: Thermal, hydrothermal, microwave and ultrasound. Chemical Engineering Journal, 279, pp.667–672. (2015).

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REVALORIZATION OF SOLID WASTE

MICROALGAE BIOMASS

FROM PIG

MANURE WATER TREATMENT TOWARDS

BIOGAS

AND

FERTILIZERS

PRODUCTION

Judit Martín Juárez, Ana Lorenzo Hernando, Silvia Bolado Rodríguez

Dpto. Chemical Engineering and Environmental Technology University of Valladolid

ATHENS2017. 5th International Conference on Sustainable Solid Waste Management. Athens. 21-24 June 2017

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Index

•

Introduction

•

Objectives

•

Materials and Methods

•

Results and Discussion

•

Conclusions

1

1.Introduction

2

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2.Objectives

3

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•

Valorization of microalgae biomass from different

wastewater treatment

•

Novel revalorization of the solid waste after anaerobic

digestion

BIOFERTILIZER

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3.Materials and Methods

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1. Biochemical analysis of raw and pretreated materials

2. Pretreatments

Alkaline-peroxide Alkali Bead Mill

Steam explosion Ultrasound

Acid

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6. Fertilizer quality

Heavy metals Pathogen COT, N, P, Mg, K….

4.Results and Discussion

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MARCH

Carbohydrates Proteins Lipids Ash

FEBRUARY

Carbohydrates Proteins Lipids Ash 43% 24% 4% 17% 13% 25% 40% 6%

1. BIOCHEMICAL COMPOSITION of RAW MICROALGAE

ALMERÍA

Pig manure treatment

Scenedesmus almerienses + Bacteria Scenedesmus almerienses + Bacteria SB3 SB4 0 10 20 30 40 50 60 70 80 90 100

BeadMill5min BeadMill60min NaOH0.5M NaOH2M

Re le as ed fr ac tio ns yi el ds (% )

Carbohydrates Proteins Lipids VS

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NaOH and Steam explosion solubilizePROTEINS and LIPIDS

4.Results and Discussion

Diapositiva 7

SB3 raw biomass, raw microalgae, ojo recordar que es de tratamiento de pig manure, es esencial.

Almeria, South Spain. Has usado solo estas dos?

Silvia Bolado; 18/06/2017

SB4 Algo sobre ls microalgas o incluso las bacterias

0 10 20 30 40 50 60 70 80 90 100

Ultrasound5min Ultrasound21min HCl0.5M HCl2M

Re le as ed fr ac tio ns yi el ds (% )

Carbohydrates Proteins Lipids VS

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HCl >> NaOH >> Steam explosion >> H2O2>> Ultrasound & Bead Mill

CONCLUSION

2. PRETREATMENTS

4.Results and Discussion

MARCH 0 50 100 150 200 250 300 350 400

0 5 10 15 20 25 30 35 40 45

m L CH 4/ g VS ad de d Time(days)

Exp_SolBeadMill5min Exp_Sol+LiqBeadMill5min Exp_SolBeadMill60min

Exp_Sol+LiqBeadMill60min Exp_SolNaOH0.5M Exp_Sol+LiqNaOH0.5M

Exp_SolNaOH2M Exp_Sol+LiqNaOH2M Exp_Control

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4.Results and Discussion

3. METHANE PRODUCTION

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0 5 10 15 20 25 30 35 40 45

m L CH 4/ gV S ad de d Time(days)

Exp_SolH2O20.5% Exp_Sol+LiqH2O20.5% Exp_SolH2O27.5%

Exp_Sol+LiqH2O27.5% Exp_SolSteamExplosion130 Exp_Sol+LiqSteamExplosion130

Exp_SolSteamExplosion170 Exp_Sol+LiqSteamExplosion170 Exp_Control 10

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4.Results and Discussion

3. METHANE PRODUCTION

0 50 100 150 200 250 300 350 400

0 5 10 15 20 25 30 35 40

m L CH 4/ g VS ad de d Time(days)

Exp_SolUltrasound5min Exp_Sol+LiqUltrasound5min Exp_SolUltrasound21min

Exp_Sol+LiqUltrasound21min Exp_SolHCl0.5M Exp_Sol+LiqHCl0.5M

Exp_SolHCl2M Exp_Sol+LiqHCl2M Exp_Control 11

3. METHANE PRODUCTION

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4.Results and Discussion

SB12 % respecto al control

Silvia Bolado; 18/06/2017

SB13 Yo pondría una resumen, con lag y con % con respecto al control

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4.Results and Discussion

3. METHANE PRODUCTION

Increase of methane production respect to the controls

0 2 4 6 8 10 12 0 20 40 60 80 100 120 140

Sol_NaOH0.5M Sol+Liq_NaOH0.5M Sol_NaOH2M Sol+Liq_NaOH2M Sol+Liq_H2O20.5% Sol_HCl2M

λ % in cr ea se 13

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3. BIOFERTILIZERS QUALITY

4.Results and Discussion

Increase of methane production respect to the controls

5.Conclusions

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1. •FEASIBLE : WHOLE fraction after the pretreatment

2. •HIGHESTMETHANE PRODUCTION: NaOHpretreatment

3. •HIGHQUALITY OF FERTILIZER: NaOHpretreatment

THANK YOU FOR YOUR ATTENTION

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