CN4218 project

Production of Biochar from Co-Gasification of water hyacinth and sludge

for plant growths Presented by Group 1: Rachel (A0185344B), Zuo Ming

(A0190150U), Kum Shan (A0185764N), Desmond (A0184142L),

Berlian (A0170774Y), Zhi Kai (A0200363X)

TABLE OF CONTENTS

Waste Problem The current food waste management issues singapore face

01Literature ReviewsKey points of gasification process, feedstock composition and desired target

02

Our Proposal solutionIntroduction of AD sludge and water hyacinth feedstock and alternative methodology

03

Food waste and Semakau● In 2019, Singapore generated a total food waste of 744 thousand tonnes and 18% is only

recycled.

● 90% of food sources imported from overseas and is thus vulnerable to food supply,

quality and price fluctuations.

● Semakau landfill receives up to 1000 tonnes of waste each day, which consist of 76%

incinerated ash

● It is estimated to be fully utilised by 2035 due to the substantial amount of solid waste

Solution & policy● Gasification and Anaerobic Digestion are use

to increase recycle rate and reduce incinerated bottom ash

● 30 by 30 goal

What is Anaerobic digestion ● Anaerobic digestion (AD) convert biodegradable waste into energy by breaking down

organic matter through a series of biochemical reactions in the absence of oxygen.

● AD produces biogas, which is a mixture of mainly methane (CH4) and carbon dioxide

(CO2).

● Biogas can supply heat, electricity and biofuels for vehicles.

● There are some limitation when utilising AD process

- Post-treatment is still require

- Certain component are not easily broken down by bacteria

Advantages and disadvantages of Gasification

Waste to Energy Application - Biomass Gasification

● Biomass gasification is effective in solving the three interconnected problems of landfill

capacity limitation, environmental pollution, and unsustainable energy production

● A 10 kW gasifier can convert 1 kg of wood chips waste to produce about 2 m3 syngas (15%

CO and 15% H2), or equivalent to 0.75 kWh electricity (able to power a 100-watt light bulb

for 7.5 hours), in the range of cost 0.024 SGD to 0.06 SGD per kWh (much lower than the

electricity produced from natural gas at 0.133 SGD per kWh)

● The solid residue obtained from the gasification process can also be transformed into a

valuable product, in the form of biochar

Biochar from Co-Gasification of Food Waste and Wood Waste

● Biochar can be used to rehabilitate the nutrient-poor, acidic soil in adinandra belukar,

which is commonly found in Singapore, Indonesia and Malaysia

● With its highly porous structure, biochar can also increase the cation exchange capacity

and reduce the tensile strength of compacted soil

● Modified biochar has shown enhanced CO2 adsorption and is nearly ten times cheaper

than other CO2 adsorbents

Literature review

Steam co-gasification of horticultural waste and sewage sludge: Product distribution, synergistic

analysis and optimization

Objective

Investigate the product distribution, gas synergistic interaction, and optimal design for gas products from the co-gasification process.

Method

Horticultural waste (HW) and sewage sludge (SS) with different mass ratios were co-gasified with steam at different temperatures

Results and Discussion

Syngas and Bottom Ash yield

● The increase of gasification temperature from 750 to 900 °C, the solid yield was decreased while the gas yield was increased.

● The increase of SS ratio in the sample would increase the ash content and then resulted in more solid part after reaction and reduce the gas yield.

Solid char composition

● The increase of temperature, the carbon content was decreased.

● The increase of SS ratio in gasification samples result in increasing carbon retention.

Synergistic Analysis

● Interaction between the components of lignocellulose biomass and sewage sludge.

● The catalysis effect of the ash in SS part may largely influence the synergistic gasification results.

● Synergistic effect between HW and SS during steam co-gasification was analyzed by comparing the experimental and calculated results.

Synergistic Effect on Overall yield

● A more drastic interaction happened between HW and SS at gasification temperature higher or equal to 850 °C.

● The synergistic effect within HW and SS during steam co-gasification favours gas production and promotes the solid char conversion.

● Effect is more significant at higher temperature due to the reduction of water gas shift and tar cracking reaction when the temperature increases.

Conclusion

● Syngas yield was increased with the increase of temperature and HW ratio in blends.

● Syngas yield and H2 production were largely promoted by synergistic interaction at higher temperature due to the catalytic effect.

● These findings would be crucial to our proposal due to its similarity to this study.

Anaerobic digestion and gasification hybrid system for potential energy recovery from yard waste and

woody biomass

Feedstock

● Anaerobic Digestion (AD)○ Yard Waste - NUS○ Anaerobic Sludge - PUB Ulu Pandan Water Reclamation Plant

Co-gasification of AD residue and Wood chips● Gasification

○ AD Residue○ Wood Chips - The Clorax Company, USA

Process of 2 stage hybrid system

Effect of mixing ratio of ad residue and wood chips● Moisture Content of AD Residue:

10.1% - 10.3%● Distinct drop in concentration of

H2 and CO when mixing 30% AD residue○ Agglomeration in reactor

Overall most energy efficient moisture content● Increase composition of CO2, H2

and CH4

● Decreased composition of CO● Higher LHV despite lower CO

because of increased CH4

● Energy used to overcome heat of vaporization of water at 50% moisture○ Lower temperature, slower

thermal conversion of biomass to syngas

Overall most efficient moisture content● Comparable Energy Efficiency● Moisture content improves quality of syngas and saves energy for

drying AD residue

Conclusion● Anaerobic Digestion (AD)

○ SCOD value indicate considerable organic matter left in AD residue → Potential for gasification

○ Higher I/S ratio improve performance● Gasification

○ Mixing Ratio → Agglomeration● Two-Stage Hybrid System

○ Drying process plays an important role in overall energy efficiency

● Optimum condition in terms of energy efficiency○ Moisture Content of AD Residue: 30%○ Mass Ratio of Wood Chips to AD Residue: 80:20○ 70.79% overall efficiency

Biochar for urban agriculture: Impacts on soil chemical characteristics and on water spinach growth, nutrient content and metabolism over

multiple growth cycles

Food Waste and Wood Waste Feedstock Characterization

● The composition of food waste and wood waste in one of the experiment is shown in the table on the left

● The carbon and hydrogencomposition in the food waste is higher than pure wood waste

● This could lead to a higher HHV(Higher Heating Value) of the feedstock and indicates that addition of food waste could enhance the energy production during gasification process

Biochar and Adindra Belukar Characterization

Item Biochar Adindra Belukar

soil

pH 9.0 4.0

Elemental

Analysis

N (ppm) 12,100.0 1120.0

P (ppm) 873.4 3.2

K (ppm) 4833.3 29.9

C : N 8.0 14.0

Surface Area (m2/g) 77.2 4.0

● Biochar has a lower C-to-N ratio (8:1), a higher pH (9.0), and Kalium, Phospor, and Nitrogen values approximately 10 – 100 times more compared to those in adinandra belukar soil.

● The large surface area of biochar could promote the absorption and capture of minerals for to the plant

Effect of Using Biochar in The Growth of Water Spinach● Plants grown in

substrate mixtures (2:1, 1:1, and 1:2 soil-biochar mixtures) shows a better growth progress compared to those in pure soil or pure biochar

● Water spinach cultivated in the 2:1 mixture had the best growth, with its plants reaching an average height of 193.8 mm

Energy Performance of an Integrated bio-and-thermal hybrid system for lignocellulosic biomass

waste treatment

Objective

Compare energy performance of 2 stage AD-gasification and 1 stage gasification,

and how OLR affects energy performance of the 2 stage system based on 3 types of

lignocellulosic wastes

Method

3 types of lignocellulosic wastes: Brewer’s spent grain (BSG)Sugarcane brasse (SCB)Horticulture waste (HW)

Anaerobic digestion performed and compositions analysed, before using a numerical model to predict energy

performance after gasification

Results and Discussion

Gasification modelling - INPUTS● Model input from experiment, thermogravimetric and elemental analysis:

● After AD (R),○ Fixed carbon content ↓○ Volatility ↑○ Higher Heating Value ↓

Gasification modelling - outputs● Syngas from samples Pretreated with AD had:

○ Slightly lower HHV

○ Lower CO and H2 composition

○ Lower Cold Gas Efficiency

○ Very similar quality

● Despite the downsides, AD produces biogas

○ Much higher quality of gas

○ 10x HHV of syngas produced from gasification

Energy performance comparison1 STAGE VS 2 STAGE

● At lower OLR, SCB and BSG produced higher total gas energy in their biogas + syngas compared to the syngas produced by gasification alone

● At high OLR, HW showed an improvement in overall efficiency in the 2 stage system by around 17.27%compared to the single stage system, despite having similar gas energy

conclusion

For the case of horticultural waste:

1. Gasification after AD is feasible

1. Possible to improve system efficiency by utilising the 2 stage AD-gasification system rather than just a single stage gasification.

Co-Gasification of AD Sludge and Water

Hyacinth to enhance food

productivity

Desired Goal

Utilize Biochar for plant growth

Increase Recycling rate of food wasteCircular food economy

Co-Gasification of AD Sludge and Water Hyacinth to enhance food productivity

Water Hyacinth ● Ranked as the 11th most invasive plant species in Europe as

it is a threat to aquatic biodiversity due to it high

reproduction rate

● High cellulosic, hemicellulosic content and heating value

makes it a suitable candidate for energy recovery.

Methods and approach

1. Preparation of Anaerobic Sludge2. Preparation of Water Hyacinth 3. Gasification approach4. Categorisation of Biochar5. Plant Growth Experiment

Preparation of AD sludge and water hyacinth

1) Food Waste Anaerobic Digester experiment in two different

temperatures, 25oC (FWAD-25) and 37oC (FWAD-37).

1) Liquid will be separated from solid

1) Water hyacinth collected from NEA

1) Solid will then undergo drying at 105oC before grinding it for

gasification

Elemental analysis of feedstockwt% C H N O S P K

FWAD-25 Solid

Digestate (unpublished

data)

45.89 5.69 6.72 - 0.79 2.58 0.61

FWAD-37 Solid

Digestate (unpublished

data)

41.24 5.55 8.13 - <0.5 1.91 1.65

Water Hyacinth [20] 64.11 - - 24.68 0.15 1.23 5.1

Gasification

1) 0.5g of sample gasified

1) Temperature step size: 50°C

1) Reaction Time: 30 mins

1) Yield of biochar and syngas

tradeoff

Hu, Q., Dai, Y., & Wang, C. H. (2020). Steam co-gasification of horticultural waste and sewage sludge: Product distribution,

synergistic analysis and optimization. Bioresource Technology, 301(January), 122780.

https://doi.org/10.1016/j.biortech.2020.122780

Operation condition for gasification

Type of FWAD FWAD-25 FWAD-37

Temperature 300 400 500 600 700

Mass Ratios of

FWAD:WH

0:1 1:9 2:8 3:7 4:6

Categorization of Biochar1) Elemental Analysis

1) TS/VS%

1) ImageJ/SEM - sphericity, shape and

Ferret Diameter

1) X-Ray Diffraction (XRD) - structure

of the biochar

Wang, Hong & Xia, Wen & Lu, Ping. (2017). Study on adsorption characteristics of biochar on heavy metals in soil.

Korean Journal of Chemical Engineering. 34. 1-7. 10.1007/s11814-017-0048-7.

Plant Growth Experiment1) Biochar wt%: 0, 20, 40, 60, 80, 100

1) Pak Choi - Common Vegetables

1) Vertical Farming - multiple grow

1) Dry weight, stem height, weekly growth rate, shoot-to-shoot ratio and specific

leaf area, NPK%

1) Microbial analysis of media

Increase Recycling rate of food waste● With a circular economy of food - this will allow nothing go to waste and increase

its economical value from nothing to something!

● Increase uptake of decentralised FWAD and gasification → increase the recycling rate of food waste.

● Reduces the amount of incinerated ash going into Pulau Semakau

Thank youQuestions?

REFERENCES

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