Kinetic of
decomposition of composting in household organic management system
Composting of organic wastes has several benefits for the
environment which includes:
·
Less than half greenhouse gases (carbon dioxide
equivalent –CO2-equiv) released compared to landfiling—415 kg of CO2-equiv per
ton waste in composting kg versus 927 kg in landfilling. The figures for
comparison has been taken to account for short term decomposition, processing
emissions and long term decomposition (up to 100 years); the processing
emissions are assumed for centralized composting system and are strongly
suggested to be much lower if composting is conducted at the household level.
Figures are cited based on data from: see footnote [1].
·
Organic wastes in landfill are the main cause of
acidic leachate which aggressively dissolve many compounds resulted in highly
toxic leachate which contaminates groundwater. Diverting organic wastes from
landfill reduces leachate toxicity. Modeling study has shown reduced toxicity
of leachate with the reduction of organic wastes loads in landfill[2].
·
Better handling characteristics in waste
management, i.e. reduced volume and weight, and becomes a stable material.
Reduced volume and weight is caused mainly by[3]
o
loss of carbon (mainly carbon dioxide and very
small amount of methane)—lost of carbon is estimated to be 63-077%
o
Loss of nitrogen (N) during composting was
51-68% and the nitrous oxide (N(2)O) made up 2.8-6.3% of this loss. The NH(3)
losses were very uncertain but small.
o
Loss of water in the form of leachate.
The study is part of setting up a household organic waste
management system to avoid its landfilling. The system aims to be efficient and
low maintenance in managing waste. To realize the aims, a system with
components of bokashi fermentation and passive aerobic composting was chosen.
In order to stabilize the wastes, fermented wastes from the kitchen is loaded
into the aerobic composting facility after adequate fermentation has been
reached—a stage which maybe termed pre-composting. The aerobic composting
facility is assisted by effective microorganisms inoculation.
Kinetic in household composting
The household organic waste management system is a
combination of bokashi fermentation and aerobic in-vessel composting with
effective microorganism innoculation.
Decomposition of organic wastes in composting is typically
described as a first order reaction. A study (see reference)[4]
had found that passive aeration and turning of organic wastes composted (compared
to decomposition without aeration and turning) can increase the rate of
decomposition by a factor of 1.8 to 2.8 at different parts of the compost bins.
Addition of innoculum effective microorganism (EM1) further increases the
kinetic by 28% to 40%[5].
The casual investigation studies the kinetic of household
composting and data are fitted to the following pseudo first-order kinetic
model equation:
where C is the mass of wastes, k is the degradation rate
constant (day-1) and t is the time (days).
Integrating the above equation and letting C = C0 initially
when t = 0, it gives
The reaction rate constant (k) was obtained by plotting ln
(C/C0) versus time.
Materials & Methods
Composting wastes:
Garden wastes mostly leaves shed by trees, kitchen wastes.
Kitchen wastes were
treated with bokashi fermentation using effective microorganism (EM4) and rice
bran and which had been fermented for 5-7 days. The effective microorganisms
are activated with sugar in the mixture of 20 ml of EM4, 15 grams of water and 1.5
liter of water. 1.5 liter + 20 ml of EM4 mixture treat about 40 – 50 liter of
kitchen wastes produced over about one week. EM4 mixture dosage applied is 17
milliliter per 1 liter of kitchen wastes. Rice bran dosage applied is 4 grams
per liter of kitchen wastes. Thus with assumed daily kitchen waste generation
of 7 liter, daily applications are:
· EM4 mixture applied is 119 ~ 120 milliliter
and
· rice bran applied is 28 ~ 30 grams.
The ratio of the
wastes garden to kitchen is 10 : 1 by volume. Garden wastes and kitchen wastes are
relatively homogenously mixed with the aid of a compost turner. The wastes are
sprayed with effective microorganism (EM4) activated with sugar in the
volumetric ratio of water and EM4 20 : 1, and 15 grams of sugar for every 20 ml
of EM4. The application rate is suggested at 3 liter EM-water mixture per 1 m3
of waste to be composted (https://www.emnz.com/industries/horticulture/composting-with-em),
which is 3 milliliter per 1 liter of waste to be composted.
The daily
generation of wastes are: 1) kitchen waste = 7 liter, 2) garden waste = 3
liter, 3) once every week the garden is cleaned more thoroughly thus generating
waste = 10 liter. Therefore daily application of EM4 mixture except for a day
of larger waste generation is,
3 (ml EM4 mixture/ liter waste ) X
(7+3)
(liter waste) = 30 ml EM4 mixture
On the day of large
waste generation, daily application of EM4 mixture is,
3 (ml EM4 mixture/ liter waste )
X [(7+10) (liter waste) = 51 ml EM4
mixture
Composting bin
which was used was a 200 liter drum with passive aeration: pipes air intake
numbering 64, on the side and bottom of drum, plastic grate, chimney in the
center of the drum to create positive draft in the drum, and 2 T-pipes at the
top of the drum to assist the creation of draft.
Nett weight of
wastes and composted wastes were weighed on day 0 and weekly for 6 weeks.
[1] http://communitycompost.org/CCN_documents/GHG_compost.pdf
[3] https://www.researchgate.net/publication/51206438_Mass_balances_and_life_cycle_inventory_of_home_composting_of_organic_waste
[4] (PDF)
Drum Composting of Food Waste: A Kinetic Study. Available from: https://www.researchgate.net/publication/305892566_Drum_Composting_of_Food_Waste_A_Kinetic_Study
[accessed Jul 10 2018].
[5] Ibid.
(Ref. 3)
Tidak ada komentar:
Posting Komentar