What is Composting?
Composting:
The
controlled decomposition of organic matter (food waste, grass, other organic
municipal wastes) is termed as “Composting”. Organic matter is broken down
through the action of microorganisms in the presence of adequate moisture and
oxygen into nutrient rich soil like material. Composting is dependent upon
temperature and required optimum temperature range. This activity can be
carried out by in controlled conditions which can support a pile. The organic
waste is broken down by earthworms, bacteria and microorganisms in the soil.
Natural composting takes place without any human input however, water and
oxygen is introduced to accelerate the activity. Once the activity id completed
the product is termed humus. (Cunningham, 2016) . This activity maximizes
the recycling of existing materials and reduces load on landfills and incinerators. Composting requires both physical and chemical transformation of
the organic matter.
Types of Composting:
The first step of composting is segregation.
Therefore, different components of waste are segregated to carry out composting
of food waste, yard trimmings, composting of leaves, manures (cow, horse, night
soil, poultry), mushroom composting and vermicomposting etc. are a few types of
composting carries out according to the material present as waste (Types of
Composting, 2015).
Methods of Composting:
The design for the composting activity has two main
units:
1. Composting
units
2. Turning
Units
Composting Units:
Depending
upon the size and nature of the waste, composting can be carried out either
direct addition of waste in to the soil or in specific holding units which
require little or no maintenance. Composting is slower in holding units as it
is difficult to carry out the turning activity however, it may take six months
to two years. (Composting Methods, 2016) . The stages of
decomposition vary from top to bottom as the most finished compost is found
near the bottom of the pile which can be easily removed and used. (Composting
Methods, 2016) The product depends upon the type of bins used. Some holding
units have small doors at the base for the removal of the compost from the bin.
This process can be accelerated by using portable bins usually made up of
polymers, hardware cloth or wire framed in wood. These Light weighted units are
designed to transfer the heaps to near-by locations where mixing and aeration
can be carried out easily. Aeration can be carried improved by using one or more
ventilating stacks made up of PVC pipes, a cylinder of wire mesh. Another way
to improve aeration place the holding unit on a wooden pallet/mat. Unfinished
compost can be removed and kept for longer time.
Things to be avoided during composting:
a. Use
of wood treated with copper arsenate, creosote and penta as these toxic
compounds may leach down the compost.
b. Use
of wood resistant to decay like cedar or untreated pine. They need to be
replaced within a few years and require new designs. (Composting Methods, 2016)
Turning unit:
These
units are required for turning/ aeration of the heaps. They are either in form
of rotating barrel, rolling ball or series of bins. These units are faster than
the holding units as the bacteria present in them have enough oxygen to
carryout decomposition. The rate of composting depends upon the turning
activity as more frequent turning results in accelerated composting. As a
result, Temperature will raise (900-1400F) and the
contamination causing organisms will be killed.
Heaps Composting:
Heap
composting is similar to composting except it doesn’t require a structure. It
takes more space and retains heat better. It requires 5*3 feet dimensions and
its length can vary according to the amount of material being used. It is
affected by the months as more heaps are available in winters. Usually two
heaps are kept side by side and doesn’t require turning. Food scraps and woody
materials may pose a problem (take more time to degrade) (Composting
Methods, 2016)
Sheet Composting:
Sheet
composting is the methods of composting which doesn’t involve composting piles.
A thin layer of organic materials (leaves, weeds, garden debris, grass clipping
and vegetable food scraps) are shredded and tilled into the soil. These
materials are tilled by using a spade, hoe, garden fork spade, or rotary
tiller. The best season for the composting is the fall season. A layer of 2-4
inches of organic matter is spread on the soil and then cultivated.
Disadvantages
of sheet composting:
1. Carbon
containing residues will call upon nitrogen reserves for their decomposition.
2. High
nitrogen materials may release nitrogen in the long form.
3. The
thermophilic conditions may require full season in soil.
Pit/ Trench Composting:
This composting technique
is the most economical way to use kitchen scraps. It is also termed as vertical
composting. One foot deep hole is dug in which food waste is mixed after
chopping. After that the hole is filled with soil again. The rate of
decomposition will depend upon the temperature provided to the microorganisms.
Composting will be completed in time range of one month to one year. (Composting Methods, 2016) . It is divided into
three season rotation/ soil incorporation and growing. The garden is divided
into 3 wide rows.
Year 1: 1 foot wide
trench is made in 1/3rd of the area. After the addition of the
compostable material; the trench is covered with soil. Breakdown of the
nutrients takes place.
Year 2: Crops are planted
in this section
Year 3: In this year ,
the soil becomes ready for plantation.
These partitions are
rotated year after year.
History
of Composting Projects in Pakistan:
Peshawar:
Government took an
initiative to install compost plant of worth Rs. 15 million in Peshawar in
2002. At that time, 350-400 tons of solid waste was collected. Land was provided
by the city government and operation cost was covered by private investors.
This project could not be executed due to unavailability of land.
Islamabad:
In 2002, A Belgian
Company, Menart, signed an agreement with Capital District Government Lahore to
set up a composting plant in Islamabad (Chaudhry, 2004).
Future of Composting in
Pakistan:
Composting is the most
suitable method to tackle organic solid waste in Pakistan however, lack of
awareness, policy framework and insufficient resources have led to failure of
various composting projects in Pakistan. Public- Private partnership and
investments by small and medium enterprises in this sector can contribute to
proper and safe management of municipal solid waste in effective manner.
References:
Chaudhry, B., M. (2004).
Composting: Turning Solid Waste into Solid Gold. Pakistan and Gulf Economist.
Retrieved on November 16, 2017 from
http://www.pakistaneconomist.com/issue2004/issue24/i&e2.php
Composting Methods.
(2016). Retrieved from University of Illinois Extension:
https://web.extension.illinois.edu/homecompost/methods.cfm
Cunningham, M. (2016).
What Is Composting? - Definition and Examples. Retrieved from Study.com:
http://study.com/academy/lesson/what-is-composting-definition-and-examples.html
Types of Composting.
(2015). Retrieved on November 14, 2015 from http://articles.extension.org/pages/62404/different-types-of-compost
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