Composting of kitchen waste using different

ratio of bulking agent

A Report on CSIR-HARIT

Submitted By: Arfin Imam

Enrolment No: 10BB17A19012 C/O Dr. Pankaj Kanaujia

& Sandhya Saini

Enrolment No: 10CC17A19004 C/O Dr. Suman Lata Jain

CSIR-INDIAN INSTITUTE OF PETROLEUM Mohkampur, Dehradun, UK – 248005

Purpose of study

Indian Institute of Petroleum is one of the constituent laboratories of Council of Scientific and

Industrial Research, India. The campus of this lab is spread over 257.57 acres (1.04 km2) and lies

adjacent to Rajaji National Park, in Dehradun region on National Highway NH-72. The campus

comprises residential colony for staff, guest house and canteens as well. The household waste

generated from these places was 40-50 Kg per day. Also dry waste mainly plastic were 15-20 Kg

per day. Hence, proper disposal must be done for the kitchen waste generated from these places.

CSIR-IIP campus is a zero waste zone and has proper waste segregation channels for both

biodegradable as well as non biodegradable wastes monitored by Eco-campus team. All the

household waste is segregated at the source and the biodegradable waste collected from every

household are subjected to composting. This study was performed in order to enhance the

composting process carried out at the CSIR-IIP campus. The present study was conducted for

composting of a small volume of organic household waste at home with low environmental risk,

i.e., its biotransformation by aerobic microorganisms under controlled conditions for obtaining

the product which is compost that can be utilized as fertilizer. Also to investigate how different

ratios of bulking agent and organic household waste can affect the progress and outcome of the

composting process. The household wastes were collected from the campus, and the experiment

was carried out in CSIR-IIP residential campus.

Relevance of the Study

In the present scenario, increasing population growth, industrialization, urbanization leads to an

increasing number of municipal solid. Adequate waste management is a serious problem faced

by all developing countries. Hence, waste Management cannot be ignored. There has been a

growing emphasis on the three R's: Reduce, Reuse, and Recycle. Composting provides a way

of accomplishing all three of the R's. Composting allow reduced landfill, the organic matter i.e.,

compost is reused and recycled rather than dumped. The compost is used for soil amendments.

Composting is a method for saddling the common procedure of decomposition to accelerate the

decay of waste. Recent concern about waste management in an environmentally friendly manner

has prompted recharged enthusiasm in small-scale, garden composting as well as an interest in

developing large-scale, commercial and municipal composting systems. The study of waste

production and management provide awareness among individuals for waste production and

waste reduction. Thus solve the real world problem using composting approach.

Introduction

Kitchen waste is defined as leftover matter from restaurants, hotels, and households (Li et al.,

2009). It is a significant part of the domestic waste. Food waste is an unwanted raw material or

cooked food discarded during or after food preparation that is no longer fit for consumption or

desirable. Toxics Links at New Delhi surveyed in May 2002 and prepared a fact file on solid

waste which stated that about 0.1 million ton of solid waste is generated in India every day. So,

annual production of solid waste reaches approximately 36.5 million tons (Kaur and Arora,

2012).

Tones of kitchen waste are produced daily in highly populated areas. An Indian city produces

about 0.8 to 1 kg of solid waste per day (Sarkar et al., 2011). These wastes are collected and

dumped into the landfills, causing major pollution (Bouallagui et al., 2005). This results in the

loss of potentially valuable materials that can be processed as fertilizers, fuel, and fodder (Baffi

et al., 2005). The Bulk of organic kit comprises mainly carbohydrates, amino acids, peptides and

proteins, volatile acids, fatty acids, and their esters are easily biodegradable.

Composting is a natural process of decomposition of organic matter by microorganisms under

controlled conditions. Composting helps to reduce the amount of waste that is being directed into

landfills. That means a reduction of concentrated, toxic leachates and methane gas that is being

released into the atmosphere, which equates to a decrease in overall pollution. Composting also

cuts down on the usage of chemical fertilizers, which are harmful to waste supply. Compost used

to improve soil physical and biological properties i.e., water retention capacity, drainage, Ph,

better availability of the soil micro-organism and reducing the negative impact of chemical based

pesticides and fertilizers in the ecosystems.

There is a large variety of microorganisms present in waste such as bacteria, protozoa, fungi, etc.

Thus, the present work mainly focused on the degradation of kitchen waste by employing

different ratios of bulking agent along with the liquid and solid cultures. In this study, we have

taken 7 different reactors by varying the amount of kitchen waste along with liquid culture, solid

culture and analyzed the effect of physicochemical factors.

Experimental setup and analysis

The study was conducted in IIP campus Dehradun (Latitude: 30.2701° N; Longitude: 78.0780°

E) and lasted for 30 days in the month of November during the winter season. The experiment

was carried out in a sheltered area away from sun and rain in a closed reactor. The reactor was

cone shaped, made of polyethylene. The reactor was chosen by the ease of availability and

designed to perform composting efficiently unlike composter bins. The reactor capacity of 20

kg, was optimum for the operation. The working volume was 5 kg in order to leave a headspace.

This headspace helps in manual turning. The reactor also comprises holes for proper aeration,

also help in exchange of gases generated during the composting process. The reactor comprises

of 30 holes at the height of 3 cm, 6 cm, 18 cm, from the base of the reactor. These holes were 5

cm apart with 1mm diameter.

Feedstock for composting

Kitchen waste used in this study was collected from different residential quarters and canteens of

CSIR-IIP. They were qualitatively characterized. The main categories of kitchen waste include

peels and leftover of vegetables like onion, potato, cabbage, spinach, apple, orange, carrot, etc.

kitchen waste also includes eggshells. These wastes were then chopped into a size of

approximately 1 cm. All the waste was then mixed properly for even distribution. Finely

chopped kitchen wastes were then mixed with the different ratio of bulking agent in order to

check the outcome of the composting process. Lantana camara (LC) was used as a bulking

agent for composting. The reason for choosing this bulking agent is due to its wide availability in

the campus. Also, it is toxic to livestock because it secretes a toxic substance called pentacyclic

triterpenoids which results in liver damage. Along with this, it shows allelopathic behavior. The

physicochemical parameters of bulking agent were shown in table 1.

Table 2: Physicochemical parameters of bulking agent:

S.No. Bulking agent Moisture

content

Total organic

carbon

(TOC)

Nitrogen

content (NC)

Carbon-to-

nitrogen

ratio (C/N)

1. Lantana camara 4.89% 44.87% 0.31% 45:0.31

2. Wheat bran 8.45% 42.63% 2.89% 42:2.89

3. Tea leaves 6.10% 49.15% 0.07% 49:0.07

The whole experimental lasted for 30 days. The composting was performed in seven

containers/reactors with varying composition of the bulking agent as shown in table 2.

Table 2: Different compositions of kitchen waste in the reactors with varying ratio.

S.No

.

Reactor

name

Composition Ratio

1. R1 Kitchen waste +bulking agent +solid culture

(1:1)

2. R2 Kitchen waste +bulking agent + liquid culture

(1:1)

3. R3 Kitchen waste +bulking agent +solid and liquid

culture

(1:1)

4. R4 Kitchen waste +bulking agent +solid and liquid

culture (1:2)

(1:2)

5. R5 Kitchen waste +bulking agent +solid and liquid

culture

(0.5:1)

6. R6 Kitchen waste +bulking agent (leafy biomass) +solid

and liquid culture

(1:1)

7. R7 Kitchen waste (control)

Nil

Different Physicochemical parameters like total organic carbon (TOC), pH, temperature,

moisture content, carbon content, nitrogen content, Ash content were analyzed for a period of 30

days.

Temperature

The temperature of all the seven reactors and the experimental site was measured on every

alternate day throughout the experiment. The temperature was recorded using a digital

thermometer with stainless steel probe and an accuracy of ±0.1°C. The temperature was

monitored at the half depth of material in the reactor, and always before manual turning.

Analysis of flies and leachate

Analysis of flies and leachate was monitored quantitatively by the same observer. The presence

and absence of the flies marked on the linear scale of 0-10. “0” designated as absence and “10”

designated as the extreme presence of flies. The leachate quantity was measured once in a week

using a measuring cylinder.

Analysis of physicochemical parameters

Composting material was analyzed for its physicochemical changes. The sample of composting

material was taken and was mixed to ensure its homogeneity. 100 mg of the sample was taken

from each reactor and were analyzed for its physicochemical changes. The analysis of pH change

was monitored in duplicates using pH meter (Thermo Fisher Scientific, EUTECH

INSTRUMENTS pH 510). Moisture content (MC) was analyzed using electronic moisture

analyzer (Sartorius moisture analyzer Model MA 160). Total organic carbon (TOC) of the

samples was estimated using TOC analyser. Nitrogen content (NC) content was analyzed by the

Kjeldahl method. Elemental analysis was done using EDX. Ash content was also calculated.

“However Nitrogen analysis and EDX analysis was not done due to non-functioning of

instruments”.

Results and discussion

Reduction in weight (W) and volume (V)

The total weight of the material added in the reactor was 3 kg in R1, 4 kg in R2, R3, R5, 5 kg in

R4, 3.8 Kg in R6, 3 kg in R7. The final weight after 30 days was 2.8 kg in R1, 3.6 kg in R2,

3.4kg in R3, 4.9 kg in R4, 3.6 kg in R5, 3.5 kg in R6, 2.5 kg in R7. The results corresponds to

weight reduction of 6.66% in R1, 10.0% in R2, 15.0% in R3, 2.0% in R4, 10.0% in R5, 7.8% in

R6 and 14.28% in R7 as shown in table 3. The weight loss can be justified by an appropriate

condition provided to microorganism for the transformation of organic waste. The factors like

porosity, moisture, temperature, appropriate nutrients when provided adequately to microbiota

lead to appropriate biotransformation. When these conditions are meeting adequately fast

degradation takes place in a short period of time. Also, the homogenized size of kitchen waste

also affects the composting process. In R7 reactor weight reduction was found at 14.28%. This

weight reduction is due to leachate formation as no bulking was used in this reactor. This also

leads to the production of odor during the composting process and become difficult to handle

hence bulking played a significant role in composting.

Table3. Data are showing a reduction in weight during composting after 30 days of

treatment.

Initial weight (Wi) Final weight (Wf) Reduction in Weight (W)

W= (Wi-Wf/ Wi)×100

3 kg 2.8 kg 6.66%

4 kg 3.6 kg 10.0%

4 kg 3.4 kg 15.0%

5 kg 4.9 kg 2.0%

4 kg 3.6 kg 10.0%

3.8 kg 3.5 kg 7.8%

3 kg 2.5 kg 14.28%

Moisture content (MC) and leachate accumulation

MC is another important parameter in during the composting process. Varying ratio composting

agent along with kitchen waste is justified using moisture content data as shown in fig. 1. High

moisture content leads to exceeding in absorption capacity. This results in accumulation of

leachate. The ratio of bulking agent is a main governing factor during composting. Low moisture

content also hampers the composting process. MC of 40% to 60% is optimum during composting

(Liang et al., 2003). MC of R1 was found 38.72% initially later found 45% for the majority of

operations. In R2 MC was 50.92% and later found 55% for rest of the experiment. Similarly, MC

in other reactors was observed. Like 61% in R3, 50% in R4, 65% in R5, 58% in R6, 82% in R7

for most of the operations. As observed form data, R7 highest MC, this is because no bulking

agent is used in this reactor. This generates leachate and bad odor due to development of

anaerobic condition during the composting process. The bulking agent provides porosity and

structure to the material. Hence, appropriate ratio of the bulking agent is significant during the

process.

Leachate formation was also observed in R6. This may be justified as; the bulking agent (leafy

biomass) used in this reactor has less absorptive capacity than the other. The excess amount of

leachate was drained from the base of the reactor.

Fig. 1. MC during composting using different ratio of bulking agent.

Flies

The presence of flies during the composting process was marked on the scale of 0 to 10. The

flies were observed to be highest on 12th day in the reactors. Afterwards there number gradually

decreases. This observation implies that the vector is not required once degradation is initiated.

R7 were given a maximum score throughout the experiment.

0

10

20

30

40

50

60

70

80

90

100

0 4 8 12 16 20 24 28 30

Mois

ture

(%

)

Time (days)

R-1

R-2

R-3

R-4

R-5

R-6

R-7

Total organic carbon (TOC) and pH

TOC content was found to be decreasing from 0th day to 20th day. The TOC content of control

sample was also found decreased during the successive day. The organic carbon was utilized by

microorganism for its metabolism when the degradation is initiated hence TOC content gradually

decreased as shown in fig. 2. However the in R7 (control sample) the TOC content on 20th day

was higher than the initial days. This is due to increased pH upon degradation of organic acids,

which further reacted with alkaline elements and raise the pH. Thus making R7 lesser acidic than

earlier and leads to increased TOC on 20th day.

Fig. 2. TOC profile during composting for seven reactors

The initial pH values was recorded between 6.72 to7.29 for R1, 6.75 to 7.27 for R2, 6.94 to 7.63

for R3, 6.69 to 7.36 for R4, 6.67 to 8.06 for R5, 6.07 to 8.06 for R6, 5.87 to 6.91 for R7 as shown

in fig.3. These result showed that the pH value increased due to the degradation of organic acids

when reacted with alkaline elements. The pH value maximum found in the reactor R5 and R6 on

30th day and it was found to be 8.06, which was basic due to the less ammonia volatilization and

leachate formation.

0

5

10

15

20

25

30

35

40

45

50

R-1 R-2 R-3 R-4 R-5 R-6 R-7

TO

C (

%)

0 day

10 day

20 day

0 5 10 15 20 25 30

5.5

6.0

6.5

7.0

7.5

8.0

pH

Time

R1

R2

R3

R4

R5

R6

R7

Fig. 3. pH profile of home composting with bulking agent.

Temperature

The highest temperature was recorded in the R4 on 4th day which was 26°C; it was due to the

highest microbial metabolism activity involved in the degradation. This means the process

increase the rate of organic matter decomposition for the increase in temperature. The lowering

of temperature in the last day was due to the attribution to the exhaustion of readily degradable

carbon sources. Furthermore, the holes in the reactor also affect the temperature because of the

increasing contact between the composting material and the atmospheric air. Also the experiment

was conducted in the month of November therefore the temperature didn’t rise above 26°C. The

temperature profile is shown in fig. 4.

0 5 10 15 20 25 30

12

14

16

18

20

22

24

26T

emp

era

ture

(oC

)

Time

R1

R2

R3

R4

R5

R6

R7

Fig. 4. Temperature profile during composting.

ASH Content

The ASH content in reactor R1 was found in between 4.18 to 3.87, 3.71 to 2.75 in R2, 5.07 to

2.79 in R3, 2.79 to 2.67 in R4, 2.84 to 2.20 in R5, 2.35 to 2.32 in R6, 3.23 to 1.61 in R7 as

represented in table 4. The result showed reduction in ash content.

The ash contents of the following composting materials were calculated by the following

formula:

% ASH

= 𝑊𝑡.𝑜𝑓 𝑡ℎ𝑒 𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑖𝑛𝑔 𝑐𝑜𝑚𝑝𝑜𝑠𝑡𝑖𝑛𝑔 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 − 𝑤𝑡.𝑜𝑓 𝑡ℎ𝑒 𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑖𝑛𝑔 𝑎𝑠ℎ

𝑊𝑡.𝑜𝑓 𝑡ℎ𝑒 𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑖𝑛𝑔 𝑐𝑜𝑚𝑝𝑜𝑠𝑡𝑖𝑛𝑔 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙*100

Table 4: Data representing ash content

Sr. No. Day of Sample

collection

Sample code ASH Content (%)

1. 0th day R01 4.18

2. 0th day R02 3.71

3. 0th day R03 5.07

4. 0th day Ro4 2.79

5. 0th day R05 2.84

6. 0th day R06 2.35

7. 0th day R07 3.23

8. 10th day R101 2.37

9. 10th day R102 3.48

10. 10th day R103 2.84

11. 10th day R104 5.13

12. 10th day R105 2.87

13. 10th day R106 3.20

14. 10th day R107 1.62

15. 20th day R201 5.18

16. 20th day R202 3.78

17. 20th day R203 2.84

18. 20th day R204 2.87

19. 20th day R205 2.47

20. 20th day R206 3.20

21. 20th day R207 1.66

22. 30th day R301 3.87

23. 30th day R302 2.75

24. 30th day R303 2.79

25. 30th day R304 2.67

26. 30th day R305 2.20

27. 30th day R306 2.32

28. 30th day R307 1.61

All the physicochemical data obtained during composting confirms favorable ongoing

composting in the designed vessel/ reactor successfully. Different ongoing stages of

composting are shown in fig 6.

Fig. 6. Images showing different stages of composting in different reactors (A) (B) (C) R1-

10th, 20th, 30th day; (D) (E) (F) R2- 10th, 20th, 30th

day; (G) (H) (I) R3- 10th, 20th, 30th day;

(J) (K) (L) R4- 10th, 20th, 30th day; (M) (N) (O) R5- 10th, 20th, 30th

day; (P) (Q) (R) R6- 10th,

20th, 30th day; (S) (T) (U) R7- 10th, 20th, 30th

day.

Conclusions

Composting of kitchen waste at home is adequate technique of waste management.

Composting using different ratio of the bulking agent helps to maintain compost quality.

The result indicates that ratio of bulking agent affects composting process and also the

quality of compost. In comparison of control sample the compost obtained with bulking

agent were of superior quality. Also the woody biomass namely Lantana camara (LC) is

found to be effective for composting. The use of LC as bulking agent reduces the generation of

leachate and odor during composting.

Suggestions/Recommendation for CSIR-IIP Eco- campus team

➢ The bulking agent used in this experiment namely Lantana camara (LC) can be

added to composing pits for aerobic degradation as LC was found to have

maximum absoption capacity than other leafy biomass.

➢ Also the waste management strategy of household waste done by Eco-campus

team must be added to CSIR-IIP web portal in order to create awareness.

References

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4. Bouallagui, H.; Touhami, Y.; Cheikh, R. B.; Hamdi, M., Bioreactor performance in anaerobic

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