Food and Scientific Reports
February 2021│Volume: 2, Issue: 1│Page23
Amrit Lal Meena1, Minakshi Karwal2, Raghavendra KJ3 and Ekta Narwal4
1&3ICAR-Indian Institute of Farming Systems Research, Modipuram, Meerut-250110; 2KIET group of Institutions, Ghaziabad, Delhi-NCR,
India-201206; 4ICAR-Indian Agricultural Research Institute, New Delhi, India-321303.
In recent decades the increased harmful effects of agro-chemicals and synthetic fertilizers both in plant and animal health
have created awareness about the use of organic inputs in agriculture. These increased demands of organic inputs have raised
concern about the management of waste material through different composting techniques. Therefore, to meet out the
demand for organic produces, there is a need for better understanding of composting methods. In this article, comparisons
between aerobic and anaerobic composting processes have been discussed. Also, a comparative analysis of both the methods
in terms of microbes involved, decomposition process, gaseous emission and superiority in pathogen suppression under both
the processes have been discussed.
Keywords: Aerobic, Anaerobic, Compost, Decomposition, Gaseous emission, Pathogens.
In recent decades, expansion of agricultural area
and increased pollution level in agricultural produces due
to unbalanced use of agro-chemicals and synthetic
fertilizers has lead to the use of compost in agriculture.
Composting can be defined as decomposition/
mineralization followed by partial humiliation of organic
materials by the biological metabolic action of
microorganisms i.e. bacteria, fungi, actinomycetes etc.
under optimum conditions over a period of time to a stable
end product. The end product is known as compost. Many
types of organic matter, such as leaves, straw, fruit and
vegetable peelings and manures can be used to make
compost. The degraded end product is completely
different from the original organic materials which have
characteristics of dark brown colour, crumbly in nature
with a pleasant smell (Mehta and Sirari, 2018; Meena et
al., 2021). Being easily available, cost-effective and easy
to prepare, compost is an important source for
improvement of soil and crop quality. Compost improves
the structure of the soil. It allows more air into the soil
improves drainage and reduces erosion. Compost helps to
stop the soil from drying out in times of drought by
holding more water. Compost helps in improvement of
soil physico-chemical properties as it adds the nutrients to
the applied soils as well as acts as a binding agent for the
soil particles; thus, increase the nutrient availability for
the plants. Based on the nature of microorganisms
involved in the decomposition process of organic wastes,
composting can be divided into two broad categories i.e.
aerobic and anaerobic.
Decomposition of organic matter using microorganisms
that require oxygen is known as aerobic composting.
These microorganisms are inhabited naturally in the
moisture surrounding organic matter. The oxygen diffuses
in the moisture from the air is utilized by the aerobic
microorganisms for their respiration and other metabolic
activities. As a result of aerobic decomposition carbon
dioxide (CO2), water and heat are released as by-products.
Production of heat in aerobic decomposition accelerates
creation of micro-environments within the compost heap
which helps in killing catastrophic pathogens and bacteria
due to non-adaptability of these harmful organisms to
these environmental conditions. These environmental
conditions also help in proliferation of diverse bacterial
species i.e. psychrophilic, mesophilic and thermophilic.
These microorganisms are basically classified as: First
level decomposers, second level decomposers and third
level decomposers (fig. 1).
Fig.1. Types of different organisms involved in composting process (Source: compost.css.cornell.edu/On Farm
First level Decomposers eat
organic material Second level Decomposers
eat level one organisms Third level Decomposers Eat
level two organisms
Ants, beetles, centipedes,
worms, flies, milipedes,
slugs, snails, spiders,
Aerobic composting versus Anaerobic composting:
Comparison and differences
Food and Scientific Reports
February 2021│Volume: 2, Issue: 1│Page24
First level Decomposers
The first level decomposers consist of the small
size microorganisms that shred the organic material and
eat the shredded organic matter, basically, the bacteria
(Bacillus coagulans, B. megaterium, B. subtilis, B.
sphaericus, B. licheniformis, B. circulans, Arthrobacter,
Alcaligenes faecalis, Bacillus brevis, B. pumilus,
Pseudomonas sp., Streptococcus sp., Thermus sp.), fungi
(Aspergillus fumigatus, Basidiomycetes sp.,
Humicoligrisea, H. insolens, H. lanuginosa, Malbranchea
pulchella, Myriococcum thermophilium, Paecilomyces
variotii, Papulaspora thermophilia, Penicillium dupontii,
Scytalidium thermophilim, Termonmyces sp., Tricoderma
sp.) and actinomycetes (Streptomyces, Frankia,
Actinomycetes micromonospora and other 14 species)
which play a crucial role in composting process. These
microorganisms through their metabolic chemical
reactions breakdown the complex organic materials into
different simple organic materials (Fig. 2) (Mehta et al.,
Fig. 2. Stepwise degradation of various organic matter
components by different level of microbes
Second level Decomposers:
The second level decomposers inherited by
nematodes, mold mites, beetle mites, springtails and
protozoa which decompose the organic material and eat
the organisms of first level decomposers. These organisms
are small in size and use of stereoscopic microscope or
hand lens is useful to scrutinize them in details.
Third level Decomposers:
The larger creature generally known as macro-
organisms i.e. beetles, ants, centipedes, millipedes, flies,
snails, slugs, composting worms and woodlice (sow bugs)
physically break down the composting materials into
small pieces through their tearing, chewing and sucking
actions. These organisms can be seen through naked eyes
(Bernal et al., 2009).
Anaerobic composting generally takes place in
nature. Composting which progresses without the
entanglement of oxygen is known as anaerobic
composting. In this process, the organic material is
breakdown by the different species of anaerobic
microorganisms. Like aerobic microorganisms, anaerobic
microbes also employ the N, P, K and other nutrients for
their metabolic development. The major differences
between aerobic and anaerobic composting are:
breakdown of organic nitrogen to ammonia and organic
acids; release of methane (CH4) from the decomposition
of carbon compounds (Jiang et al., 2011). Reduction is the
main process of breakdown of organic matter under
anaerobic composting, though for a shorter period of time
oxidation also takes place for preparation of final end
product in anaerobic composting. There are four major
stages of anaerobic decomposition i.e. Hydrolysis,
acidogenesis, acetogenesis and methanogenesis.
In hydrolysis which is the first stage, the
insoluble complex organic materials i.e. cellulose,
hemicelluloses, lignin etc. are hydrolysed into the soluble
simple amino acids, fatty acids and sugars. The hydrolysis
process has a significant stage in anaerobic composting as
it decomposes the raw organic matter with high complex
organic content. The fermentative acidogenic bacteria
further decompose the remaining complex organic matter
into simple molecules under the acidogenesis process
which is the second stage of anaerobic composting. In the
third stage i.e. acetogenesis, simple organic molecules
created by the acidogenesis process are further digested to
acetic acid, carbon dioxide (CO2) and hydrogen. The
microbes involved in acetogenesis process are:
Acetobacter woodii, Clostridium aceticum and
Clostridium termoautotrophicum. Production of methane
gas (CH4) by methane forming microbes i.e.
Methanosarcina takes place in the fourth and final stage
which is known as methanogenesis (Mehta and Sirari,
Aerobic versus anaerobic composting
The consumption and decomposition of organic
matter by the microorganisms have broadly been
categorized into two categories: first one that require
oxygen (aerobic) and those that don’t require oxygen
(anaerobic). Though many studies have considered
anaerobic composting as a suitable alternative to aerobic
composting due to minimized loss of nitrogen in
anaerobic composting (Yu et al., 2015). But the aerobic
composting has considerable advantages over anaerobic
Food and Scientific Reports
February 2021│Volume: 2, Issue: 1│Page25
composting i.e. rise in the temperature of the pile as high
as up to 60ºC-70ºC which helps in killing of weed seeds
and pathogens; aeration increase the decomposition rate of
the organic material; shorter period of time requires for
compost preparation and the intensity and number of
objectionable emissions are distinctly reduced (Gill et al.,
2014). Three main broad categories have been identified
between aerobic and anaerobic composting i.e.
Decomposition; pathogen suppression and emission of
Turning and proper aeration increase the
decomposition rate of organic material in aerobic
composting compared with anaerobic composting. For the
proper decomposition of organic material, it should be
kept at least for six to twelve months in anaerobic
composting while; a time of period of 30 days to 120 days
is far enough for complete decomposition of organic
material in aerobic composting (Tian et al., 2012).
Microbes are the essential component of
composting both in aerobic and anaerobic methods.
Presence of diversified microorganisms in aerobic
composting raises the compost pile temperature up to
60ºC-70ºC which is far enough to kill the harmful
pathogens and weed seeds present in the composting
materials. Whereas, on the other hand, the low
temperature and presence of specific species of
microorganisms in anaerobic compost are unable to kill
the pathogen and weed seeds and they remain in the
composting material. It has been observed by several
studies that presence of 50-70ºC temperature and 35%
moisture level in aerobic composting is high enough to
kill the weed seeds of pigweed, barnyard grass, kochia etc.
Also, several pathogenic fungi species viz. Olpidium
brassicae, Fusarium oxysporum, Plasmodiophora
brassicae, Synchytrium endobioticum, Phytophthora
infestans and various bacterial plant pathogens are unable
to survive at the higher temperature generated during the
aerobic composting (Mehta et al., 2016). Thus, it has been
observed that the optimum exposure of the composting
material at high temperature is required for preparation of
pathogen free compost. All these beneficial effects
support the importance of thermophilic phase of aerobic
composting compared with the anaerobic composting
where the temperature level never reaches up to 65ºC.
In both aerobic and anaerobic composting
processes some unpleasant odours emitted from the
composting materials which are generated due to rapid
microbial degradation of complex organic matter into
simple compounds. The extent and intensity of odours
emission are high in aerobic composting as compare to
anaerobic composting but rapid turning and frequent
supply of oxygen in aerobic composting decrease the
chances of evolution and emission of unpleasant gases
whereas, because of closed systems and low level of
oxygen causes higher formation and emission of
unpleasant gases in anaerobic composting (Jiang et al.,
2015). Application of various chemical and biological
treatments can reduce the emission of these gases from the
composting materials. Thus all the above discussed
benefits support the superiority of aerobic composting
over the anaerobic methods.
The main aim of this article was to discuss the
types of composting, microbes involve in composting
processes and comparison between the aerobic and
anaerobic composting methods. Both aerobic and
anaerobic composting techniques have significant
environmental impacts through management of the waste
materials which include: management of VOC (volatile
organic compounds) and odour emissions and killing of
pathogens and weed seeds. It has been clearly found out
that rapid turning and presence of oxygen fasten the
composting process in aerobic composting compared with
the anaerobic method.
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