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J. Jayaprakash and H. Jagadeesan
consisting of decomposition of organic matter by microorganisms into compost that
is stable, free of pathogens and can be used as soil amendment. In general, there are
three types of composting—aerobic (with oxygen), anaerobic also known as trench
composting (without oxygen) and vermicomposting (Sinha and Sinha 2016). Generally, composting process occurs in three phases such as mesophilic, thermophilic
and curing. In the first phase, acid-producing bacteria such as Lactobacillus spp. and
Acetobacter spp. metabolize carbohydrates, sugars and proteins. During this phase,
the temperature of the composting increases from ambient to 40 °C. In the second
phase, thermophilic bacteria such as Bacillus spp. and Actinobacteria are involved
in the protein and lipid metabolism, and it reaches the temperature of 40–70 °C. The
last curing phase (cooling phase) composting is a long time process where the nutrients in the compost become depleted, and simultaneously slows down the metabolic
activity of microorganisms (Epstein 1996). As a result, heat generation is gradually
decreased, and the compost becomes dry and crumbly texture. Several factors such
as oxygen, temperature, moisture, C:N ratio, particle size, pH, aeration rate, etc. are
affecting the growth of microorganisms (Makan et al. 2013), and thereby the optimization of these parameters has a great influence on the rate of composting and
quality of composts.
The current study was conducted in an educational institution with a footfall of
12000 persons/day in Anna University, Chennai, India. This study aimed to determine the feasibility of in-vessel composting to treat yard waste generated inside the
campus and also evaluates the effect of additives (food wastes and paper waste) in cocomposting. Yard waste was prepared by mixing browns and greens at an arbitrary
ratio of approximately 1:1 (dry content basis), respectively. Browns include dried
fall leaves and wooden debris in the ratio 2:1. Greens includes fresh plant materials
and grass clippings. Other additives were mixed with yard waste (CY) in proportions
(2:1) that resulted in acceptable C: N ratios (5:1–25:1). The feedstock combinations
were as follows:
• Yard wastes (dried fall leaves: grass clippings: wooden debris, 1:1:1) (CY).
• Yard wastes + vegetable waste (2:1), (CYV).
• Yard wastes +fruit wastes (2:1) (CYF).
• Yard wastes + spent coffee grounds (2:1) (CYCo).
• Yard wastes + spent tea leaves (2:1) (CYT).
• Yard wastes + paper waste (2:1) (CYP).
Three kg of feedstock in various combinations as described above was chosen as
feedstock. The experiments were run in closed, perforated cylindrical vessel (30L
capacity) in three replicates per treatment. The drums are of diameter 50 inches and
height 48 inches approximately ensuring to hold a capacity of 3 kg of waste with
head space for good aeration (Fig. 2). They were watered as required, and no extra
fertilization was applied. Aeration was facilitated by perforation of diameter about
0.5 cm. The composts were characterized in terms of total solids, volatile solids,
pH, electrical conductivity (EC), total organic carbon (TOC), total Kjeldahl nitrogen
(TKN), carbon: nitrogen ratio (C:N ratio), micronutrients like Fe, K, Mg, Ca, P, Na,
microbial population, stability index, seed germination test, heavy metal content and
J. Jayaprakash and H. Jagadeesan
consisting of decomposition of organic matter by microorganisms into compost that
is stable, free of pathogens and can be used as soil amendment. In general, there are
three types of composting—aerobic (with oxygen), anaerobic also known as trench
composting (without oxygen) and vermicomposting (Sinha and Sinha 2016). Generally, composting process occurs in three phases such as mesophilic, thermophilic
and curing. In the first phase, acid-producing bacteria such as Lactobacillus spp. and
Acetobacter spp. metabolize carbohydrates, sugars and proteins. During this phase,
the temperature of the composting increases from ambient to 40 °C. In the second
phase, thermophilic bacteria such as Bacillus spp. and Actinobacteria are involved
in the protein and lipid metabolism, and it reaches the temperature of 40–70 °C. The
last curing phase (cooling phase) composting is a long time process where the nutrients in the compost become depleted, and simultaneously slows down the metabolic
activity of microorganisms (Epstein 1996). As a result, heat generation is gradually
decreased, and the compost becomes dry and crumbly texture. Several factors such
as oxygen, temperature, moisture, C:N ratio, particle size, pH, aeration rate, etc. are
affecting the growth of microorganisms (Makan et al. 2013), and thereby the optimization of these parameters has a great influence on the rate of composting and
quality of composts.
The current study was conducted in an educational institution with a footfall of
12000 persons/day in Anna University, Chennai, India. This study aimed to determine the feasibility of in-vessel composting to treat yard waste generated inside the
campus and also evaluates the effect of additives (food wastes and paper waste) in cocomposting. Yard waste was prepared by mixing browns and greens at an arbitrary
ratio of approximately 1:1 (dry content basis), respectively. Browns include dried
fall leaves and wooden debris in the ratio 2:1. Greens includes fresh plant materials
and grass clippings. Other additives were mixed with yard waste (CY) in proportions
(2:1) that resulted in acceptable C: N ratios (5:1–25:1). The feedstock combinations
were as follows:
• Yard wastes (dried fall leaves: grass clippings: wooden debris, 1:1:1) (CY).
• Yard wastes + vegetable waste (2:1), (CYV).
• Yard wastes +fruit wastes (2:1) (CYF).
• Yard wastes + spent coffee grounds (2:1) (CYCo).
• Yard wastes + spent tea leaves (2:1) (CYT).
• Yard wastes + paper waste (2:1) (CYP).
Three kg of feedstock in various combinations as described above was chosen as
feedstock. The experiments were run in closed, perforated cylindrical vessel (30L
capacity) in three replicates per treatment. The drums are of diameter 50 inches and
height 48 inches approximately ensuring to hold a capacity of 3 kg of waste with
head space for good aeration (Fig. 2). They were watered as required, and no extra
fertilization was applied. Aeration was facilitated by perforation of diameter about
0.5 cm. The composts were characterized in terms of total solids, volatile solids,
pH, electrical conductivity (EC), total organic carbon (TOC), total Kjeldahl nitrogen
(TKN), carbon: nitrogen ratio (C:N ratio), micronutrients like Fe, K, Mg, Ca, P, Na,
microbial population, stability index, seed germination test, heavy metal content and