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Journal Article•DOI•

A comparison of product yields and inorganic content in process streams following thermal hydrolysis and hydrothermal processing of microalgae, manure and digestate.

U. Ekpo1, Andrew B. Ross1, Miller Alonso Camargo-Valero2, Paul T. Williams1•
University of Leeds1, National University of Colombia2
01 Jan 2016-Bioresource Technology (Elsevier)-Vol. 200, pp 951-960
TL;DR: This study compares the behaviour of microalgae, digestate, swine and chicken manure by thermal hydrolysis and hydrothermal processing at increasing process severity to show promise for converting biomass into higher energy density fuels.
About: This article is published in Bioresource Technology.The article was published on 2016-01-01 and is currently open access. It has received 185 citations till now. The article focuses on the topics: Hydrothermal liquefaction & Chicken manure.

Summary (3 min read)

Jump to: [1. Introduction 24] – [2.1 Materials 15] – [2.2 Hydrothermal processing 5] – [2.3 Product recovery and analysis 17] – [3.1 Characterisation of feedstock 4] – [3.2 Product yields during hydrothermal processing 5] – [3.3 Characterization of the solid product 6] – [3.4 Characterization of the aqueous product (AP) 14] – [3.4.2 Total Organic Carbon (TOC) 29] – [3.4.3 Distribution of Nitrogen 8] – [3.4.4 Distribution of Phosphorus 10] and [3.4.5 Distribution of Potassium 5]

1. Introduction 24

  • There is a growing 3 interest in the recovery of nutrients from wet wastes such as manures and bio-solids and 4 hydrothermal processing has been proposed to facilitate the extraction of nitrogen, 5 phosphorus and potassium from these materials (Biller et al., 2012; Heilmann et al., 2014).
  • He e al., (2000) 23 performed HTL of swine manure at temperatures between 275 and 350 °C and observed that 24 the reaction conditions had little influence on the distribution of nitrogen, phosphorus and 25 potassium species (NPK) which was mainly found in the aqueous product (He et al., 2000).
  • The levels of phosphate recovery in the process water 5 were found to vary with feedstock (Lopez Barreiro et al., 2014) and once again are linked to 6 the inorganic content of the feedstock.

2.1 Materials 15

  • The four biomass feedstocks used in this study were obtained from different sources.
  • 16 Chlorella vulgaris was obtained as dry powder from a commercial source.
  • The poultry and swine manure were 18 collected from the University of Leeds farm.
  • 22 23 Ultimate analyses was performed using a CE Instruments Flash EA 1112 series elemental 24 analyser to determine the percentage composition of carbon, hydrogen, nitrogen, sulphur and 25 oxygen of the dry unprocessed biomass samples.
  • All measurements were performed in duplicate and the mean values 1 have been reported.

2.2 Hydrothermal processing 5

  • In each case the residence time was taken from the 11 point the reactor reached the desired temperature.
  • The heating rate was 10 °C min-1 and the 12 cooling rate was in a similar range.
  • The heating and cooling rates are the same for each 13 feedstock as the same reactor was used for all the experiments.

2.3 Product recovery and analysis 17

  • Following hydrothermal treatment, the reactor was allowed to cool to room temperature 18 before emptying.
  • The solid residues and the aqueous products were separated by filtration using a pre-20 weighed Whatman filter paper.
  • Significant quantities of bio-crude 24 were produced during the HTC and HTL process.
  • Metals such as potassium, calcium, magnesium, sodium, iron and 6 aluminium were analysed using atomic absorption spectroscopy (AAS) while nickel and 7 cobalt were analysed using inductively coupled plasma mass spectrometry (ICP-MS).
  • After complete digestion (as indicated by a greenish 15 colour) the samples were left to cool before the distillation step.

3.1 Characterisation of feedstock 4

  • The proximate and ultimate analyses of the four feedstock investigated are listed in Table 1. 5.
  • The microalgae and manure contained the higher carbon and hydrogen content at 47 13 wt.% and 6-7 wt.% respectively.
  • The digestate on the other hand contained significantly 16 lower levels of carbon (18 wt.%).
  • 21 22 Table 2 lists the nutrient and metal content of the four unprocessed biomass feedstocks.

3.2 Product yields during hydrothermal processing 5

  • The product yields (i.e, solid, liquid, gas and oil) following hydrothermal processing of each 6 feedstock are shown in Figure 1.
  • Thermal 15 hydrolysis at 170 °C typically produced the highest yields of solid residue for all the 16 feedstock.
  • The gas yield is more significant than in thermal hydrolysis and 1 ranges from 6-12%.

3.3 Characterization of the solid product 6

  • Table 3 lists the proximate and ultimate analysis of the residues produced from the different 7 hydrothermal processes together with their higher heating value (HHV).
  • The volatile matter is 10 significantly reduced with reaction severity producing a more carbonised product.
  • The carbon content of the hydrochar recovered 13 from the HTC of swine manure and chicken manure increases from 43-46 wt.% to 56 wt.% 14 and 60 wt.% respectively.
  • The level of 25 phosphorus in the residue increase with reaction severity.
  • High levels of 8 nickel have previously been observed in the process waters following SCWG and is a result 9 of nickel leaching from the reactor walls (Lopez Barreiro t al., 2014).

3.4 Characterization of the aqueous product (AP) 14

  • The aqueous products derived from each of the hydrothermal routes have been analysed 15 quantitatively for each feedstock to determine the concentrations of nitrogen (N), phosphorus 16 (P), total organic carbon (TOC) and other metals.
  • The pH of the aqueous products was also 17 monitored and the results are listed in Table 5. 18 19.

3.4.2 Total Organic Carbon (TOC) 29

  • The TOC level in SCWG water phase was the lowest compared to HTL, HTC or 31 thermal hydrolysis for all feedstock processed.
  • The presence of organic carbon in the SCWG 1 water phase implies that not all the organic content was converted to gas during the process.
  • The addition of catalysts during SCWG has been shown to reduce the TOC levels of the 3 aqueous product (Stucki et al., 2009).
  • The highest levels of TOC were in the 4 aqueous phase from hydrothermal processing of microalgae followed by the chicken manure, 5 swine manure and digestate.

3.4.3 Distribution of Nitrogen 8

  • Hydrothermal processing at different temperatures affects the distribution of nitrogen.
  • The 28 results show that 75% of the total nitrogen in the aqueous phase after thermal hydrolysis is 29 organic.
  • The reason for this is not obviously 1 apparent but will be investigated further later.

3.4.4 Distribution of Phosphorus 10

  • Figure 2 b shows the extraction of phosphorus into the aqueous phase for each of the 11 different conditions.
  • The aqueous phase from thermal hydrolysis has the highest 13 levels of total phosphorus (TP) which reduces significantly as the process severity increases.
  • At the lower temperatures, approximately 40% of the P was extracted from microalgae and 15 chicken manure although the levels are lower for digestate and swine manure.
  • This was confirmed with scanning electron microscopy and energy dispersive spectroscopy 4 which indicated the presence of Ca3(PO4)2 and Mg3(PO4)2.
  • After SCWG, the P is mainly associated 30 with the solid product with low levels of extraction into the aqueous phase.

3.4.5 Distribution of Potassium 5

  • The results in Figure 2c indicate that potassium is almost completely extracted under all 6 conditions.
  • At lower temperature processing, significant 22 levels of organic phosphorus and nitrogen are observed in the aqueous phase.
  • A summary and discussion of chemical mechanisms for process engineering, Biofuel Bioprod, also known as Hydrothermal carbonization of biomass.
  • Cultivation of microalgae with recovered nutrients after hydrothermal liquefaction.

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Citations
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Journal Article•DOI•
Distribution of nutrients and phosphorus recovery in hydrothermal liquefaction of waste streams

[...]

Aisha Matayeva, Stephanie R. Rasmussen, Patrick Biller
01 Jan 2022-Biomass & Bioenergy
TL;DR: In this article , the fate of P and other nutrients has been studied by performing hydrothermal liquefaction of four P-rich wastes and the effect of temperature on the distribution of the HTL products and nutrients was investigated.
Abstract: Hydrothermal liquefaction (HTL) of phosphorus (P) rich wastes is a promising technology to recover P in solid form. For the applicability as fertilizer, the HTL solids should contain nutrients, in particular P, in plant available form and low concentrations of heavy metals. In the present study, the fate of P and other nutrients has been studied by performing HTL of four P-rich wastes. The effect of temperature on the distribution of the HTL products and nutrients has been investigated. It was found that up to 100% of the total P can be accumulated in the solid phase. However, the bioavailability of P decreased to 0.6–1% and the concentrations of heavy metals exceeded threshold values for fertilizers. Due to the limited P bioavailability and high contents of heavy metals, the reclamation of P as struvite is also calculated. Based on these estimations, between 42 and 93% of P can be recovered as struvite.

15 citations

Journal Article•DOI•
Optimize hydrogen production from chicken manure gasification in supercritical water by experimental and kinetics study

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Wenhan Cao, Wenwen Wei, Hui Jin, Lei Yi, Le Wang 
01 Mar 2022-Journal of environmental chemical engineering
TL;DR: In this paper , a quantitative kinetic model was employed to study the reaction mechanism and optimize the H2 production from supercritical water gasification (SCWG) of chicken manure in a high heating rate batch reactor under different temperatures (500-620 °C) and residence times (1-12 min).
Abstract: In this work, H2 production from supercritical water gasification (SCWG) of chicken manure in a high heating rate batch reactor under different temperatures (500–620 °C) and residence times (1–12 min) was studied, and a quantitative kinetic model was employed to study the reaction mechanism and optimize the H2 production. The H2 yield, hydrogen gasification efficiency (HE) and carbon gasification efficiency (CE) were promoted with the growth of temperature and residence time. The maximum H2 yield, HE and CE reached 22.47 mol/kg, 174.53% and 81.34% at 620 °C and 12 min, respectively. The results of kinetic model indicated that higher temperature accelerated the reaction rate and more intermediates were converted into gas products. H2 was mainly produced by the steam reforming reaction and the generation rate of each gas decreased to be negligible after 10 min. High temperature from nearly 580 °C was preferred to accelerate water gas shift reaction (WGSR) to promote H2 production in SCWG of chicken manure. Hydrolysis reaction of chicken manure has a very important effect on H2 production.

14 citations

Journal Article•DOI•
Cultivation of Microalgae in Municipal Wastewater and Conversion by Hydrothermal Carbonization: A Review

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Benjamin Hupfauf, Michael Süß1, Alexander Dumfort, Heidrun Fuessl-Le•
University of Calgary1
01 Aug 2016
TL;DR: In this paper, the authors focus on Hydrothermal Carbonization (HTC) as a processing strategy to produce an energy-rich biochar and a liquid fraction that can be further processed to higher-value substances.
Abstract: The idea of growing microalgae in wastewaters emerges from the idea of resource conservation and the recovery of nutrients. In fact, microalgae are able to take up nitrogen, phosphorus and carbon from wastewaters, even adsorb metals, and in many cases, can be co-cultivated with various bacteria that are prevailing in municipal wastewater treatment plants. The cultivation of microalgae in municipal wastewater has been known for about half a century and investigated accordingly. Despite this long history, there are still many questions to answer before this technology will be ready for implementation in large-scale projects. In this review, recent developments are presented. One crucial point in developing a viable process out of wastewater grown algae is the downstream processing of the accumulated algal biomass. The authors decided to focus on hydrothermal carbonization (HTC) as a processing strategy. HTC uses wet biomass and relatively mild process conditions to produce an energy-rich biochar and a liquid fraction that can be further processed to higher-value substances. The latest findings in the carbonization of microalgae are highlighted in the second part of this article.

14 citations

Journal Article•DOI•
Valorization of livestock manure for bioenergy production: A perspective on the fates and conversion of antibiotics

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Libin Yang, Buchun Si, Xiaobo Tan, Jiao Xu, Wen-Guo Xu, Li Zhou, Jian Chen, Yawei Zhang, Xuefei Zhou 
01 Aug 2022-Resources Conservation and Recycling
TL;DR: In this paper , the authors explored the research implications and proposed new avenues in the field of bioenergy conversion of livestock manure from a perspective of fates and conversion of antibiotics, and discussed the removal mechanisms of antibiotics by different treatment technologies as well as their challenges and prospects.
Abstract: Land application of livestock manure is a common waste utilization process that improves soil fertility and increases food production, while antibiotics in livestock manure posed potential threat to human and ecological health when applied to agricultural fields. Biological, thermochemical and bioelectrochemical technologies have been widely investigated to stabilize livestock manure and produce bioenergy. However, systematic information on the fates and conversion of antibiotics is still unclear. Therefore, this review first estimated the distribution of antibiotics in livestock manure. Additionally, the recent advances on the fates and degradation of antibiotics in livestock manure during the bioenergy production processes were summarized. Furthermore, the removal mechanisms of antibiotics by different treatment technologies, as well as their challenges and prospects were discussed. This review explored the research implications and proposed new avenues in the field of bioenergy conversion of livestock manure from a perspective of fates and conversion of antibiotics.

13 citations

Journal Article•DOI•
The Influence of pH on the Combustion Properties of Bio-Coal Following Hydrothermal Treatment of Swine Manure

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Aidan M. Smith, Ugochinyere Ekpo, Andrew B. Ross
09 Jan 2020-Energies
TL;DR: In this article, swine manure was treated at temperatures ranging from 120 to 250 °C in either water alone or reagents including 0.1 M NaOH, 0.2 M H2SO4, and finally 0. 1 M organic acid (CH3COOH and HCOOH).
Abstract: The application of excessive amounts of manure to soil prompted interest in using alternative approaches for treating slurry. One promising technology is hydrothermal carbonisation (HTC) which can recover nutrients such as phosphorus and nitrogen while simultaneously making a solid fuel. Processing manure under acidic conditions can facilitate nutrient recovery; however, very few studies considered the implications of operating at low pH on the combustion properties of the resulting bio-coal. In this work, swine manure was hydrothermally treated at temperatures ranging from 120 to 250 °C in either water alone or reagents including 0.1 M NaOH, 0.1 M H2SO4, and finally 0.1 M organic acid (CH3COOH and HCOOH). The influence of pH on the HTC process and the combustion properties of the resulting bio-coals was assessed. The results indicate that pH has a strong influence on ash chemistry, with decreasing pH resulting in an increased removal of ash. The reduction in mineral matter influences the volatile content of the bio-coal and its energy content. As the ash content in the final bio-coal reduces, the energy density increases. Treatment at 250 °C results in a more “coal like” bio-coal with fuel properties similar to that of lignite coal and a higher heating value (HHV) ranging between 21 and 23 MJ/kg depending on pH. Processing at low pH results in favourable ash chemistry in terms of slagging and fouling. Operating at low pH also appears to influence the level of dehydration during HTC. The level of dehydration increases with decreasing pH, although this effect is reduced at higher temperatures. At higher-temperature processing (250 °C), operating at lower pH increases the yield of bio-coal; however, at lower temperatures (below 200 °C), the reverse is true. The lower yields obtained below 200 °C in the presence of acid may be due to acid hydrolysis of carbohydrate in the manure, whereas, at the higher temperatures, it may be due to the acid promoting polymerisation.

13 citations

Cites background from "A comparison of product yields and ..."

  • ...The extent to which the phosphorus is extracted is feedstock-dependent, with the inorganic content of the feedstock, particularly calcium content, often a key variable [6]....

    [...]

References
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Journal Article•DOI•
Hydrothermal liquefaction of biomass: A review of subcritical water technologies

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Saqib Toor1, Lasse Rosendahl1, Andreas Rudolf•
Aalborg University1
01 May 2011-Energy
TL;DR: In this paper, the authors present a review of the current status of the hydrothermal liquefaction of biomass with the aim of describing the current state of the technology, which is a medium-temperature, high-pressure thermochemical process which produces a liquid product, often called bio-oil or bi-crude.

1,451 citations

Journal Article•DOI•
Hydrothermal carbonization of biomass: A summary and discussion of chemical mechanisms for process engineering

[...]

Axel Funke1, Felix Ziegler1•
Technical University of Berlin1
01 Mar 2010-Biofuels, Bioproducts and Biorefining
TL;DR: In this article, a review summarizes knowledge about the chemical nature of this process from a process design point of view, including reaction mechanisms of hydrolysis, dehydration, decarboxylation, aromatization, and condensation polymerization.
Abstract: Hydrothermal carbonization can be defined as combined dehydration and decarboxy lation of a fuel to raise its carbon content with the aim of achieving a higher calorific value. It is realized by applying elevated temperatures (180–220°C) to biomass in a suspension with water under saturated pressure for several hours. With this conversion process, a lignite-like, easy to handle fuel with well-defined properties can be created from biomass residues, even with high moisture content. Thus it may contribute to a wider application of biomass for energetic purposes. Although hydrothermal carbonization has been known for nearly a century, it has received little attention in current biomass conversion research. This review summarizes knowledge about the chemical nature of this process from a process design point of view. Reaction mechanisms of hydrolysis, dehydration, decarboxylation, aromatization, and condensation polymerization are discussed and evaluated to describe important operational parameters qualitatively. The results are used to derive fundamental process design improvements. Copyright © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd

1,428 citations

"A comparison of product yields and ..." refers background in this paper

  • ...…processing of wastes such as sewage sludge (Zhu et al., 2011; Xu et al., 2012) and to a lesser extent manures but most have focused on energy densification (He et al., 2001; Theegala and Midgett, 2012; Chen et al., 2014; Titirici et al., 2007; Funke and Ziegler, 2010; Berge et al., 2011)....

    [...]

Journal Article•DOI•
Potential yields and properties of oil from the hydrothermal liquefaction of microalgae with different biochemical content.

[...]

Patrick Biller1, Andrew B. Ross1•
University of Leeds1
01 Jan 2011-Bioresource Technology
TL;DR: Broad agreement is reached between predictive yields and actual yields for the microalgae based on their biochemical composition, and the yields of bio-crude follow the trend lipids>proteins>carbohydrates.

973 citations

"A comparison of product yields and ..." refers background or methods in this paper

  • ...The bio-crude has a higher oxygen and nitrogen content than crude oil (Brown et al., 2010; Biller and Ross, 2011)....

    [...]

  • ...The reason for the high bio-crude yields exhibited by Chlorella is due to the high lipid content in its cell wall (Biller and Ross, 2011)....

    [...]

  • ...A more detailed description of the experimental set up is described elsewhere (Biller and Ross, 2011; Cherad et al., 2016)....

    [...]

  • ...Hydrothermal liquefaction (HTL) is operated at 280–370 C and pressures ranging from 10 to 25 MPa and produces a synthetic bio-crude (Biller and Ross, 2011)....

    [...]

  • ...Studies have shown that the bio-crude produced from HTL of microalgae have high heating values (Minowa et al., 1995; Biller and Ross, 2011; Jena et al., 2011)....

    [...]

Journal Article•DOI•
Hydrothermal liquefaction and gasification of Nannochloropsis sp.

[...]

Tylisha M. Brown1, Peigao Duan1, Phillip E. Savage1•
University of Michigan1
10 May 2010-Energy & Fuels
TL;DR: This article converted the marine microalga Nannochloropsis sp. into a crude bio-oil product and a gaseous product via hydrothermal processing from 200 to 500 °C and a batch holding time of 60 min.
Abstract: We converted the marine microalga Nannochloropsis sp. into a crude bio-oil product and a gaseous product via hydrothermal processing from 200 to 500 °C and a batch holding time of 60 min. A moderate temperature of 350 °C led to the highest bio-oil yield of 43 wt %. We estimate the heating value of the bio-oil to be about 39 MJ kg−1, which is comparable to that of a petroleum crude oil. The H/C and O/C ratios for the bio-oil decreased from 1.73 and 0.12, respectively, for the 200 °C product to 1.04 and 0.05, respectively, for the 500 °C product. Major bio-oil constituents include phenol and its alkylated derivatives, heterocyclic N-containing compounds, long-chain fatty acids, alkanes and alkenes, and derivatives of phytol and cholesterol. CO2 was always the most abundant gas product. H2 was the second most abundant gas at all temperatures other than 500 °C, where its yield was surpassed by that of CH4. The activation energies for gas formation suggest the presence of gas-forming reactions other than steam...

691 citations

"A comparison of product yields and ..." refers background in this paper

  • ...The bio-crude has a higher oxygen and nitrogen content than crude oil (Brown et al., 2010; Biller and Ross, 2011)....

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Journal Article•DOI•
Morphological and structural differences between glucose, cellulose and lignocellulosic biomass derived hydrothermal carbons

[...]

Camillo Falco1, Niki Baccile2, Maria-Magdalena Titirici1•
Max Planck Society1, Centre national de la recherche scientifique2
11 Jan 2011-Green Chemistry
TL;DR: In this paper, the effects of the processing temperature and time on the chemical structure and morphology of the generated HTC carbon were investigated with the help of SEM, elemental and yield analysis and solid-state MAS 13C NMR, allowing the development of a mechanistic model.

603 citations

"A comparison of product yields and ..." refers background in this paper

  • ...That has been observed previously as a consequence of dehydration and decarboxylation reactions (Falco et al., 2011)....

    [...]

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