Anaerobic Digestion of Organic Waste in UMS Campus …
137
of Mg
2+ was obtained using Atomic Absorption Spectrometer (AAS), at 285.2 nm
of wavelength (λ). Five (5) standard solutions with different concentrations (0.5,
1.0, 1.5, 2.0 and 2.5 ppm) were prepared from 1000 ppm of Mg standard solution
and used to generate a calibration curve. The concentration of NH 4
+ was determined
using Kjeldahl method (Buchi), where the concentration of PO 4
3− was determined
using UV-Vis Spectrophotometer (Cary 60), λ = 800 nm, using five (5) standard
solutions with different concentrations (1, 2, 3, 4 and 5 ppm) which were prepared
from 100 ppm of PO 4
3− stock solution. The chemical characteristics were carried
out using FWRL and FWDL according to the method described by APHA (2005).
3 Results and Discussion
3.1 Composition of Food Waste Samples
Figure 1 shows the percentage (%) of different components of food waste used in this
study, where vegetables and fruit peels comprised the highest percentage (45.73%)
followed by chicken and fish bones (19.68%), while unused part of meats contributes
the lowest percentage (0.62%). Other components were between 3.28 and 12.59%.
The sampling points and sampling period are the important factors, which may affect
the percentages. The unused vegetable parts such as stem and spoiled leaves that are
produced during food preparation stage may be the reason for its highest percentage.
In addition, the café may also produce a huge amount of vegetable leftovers as most
students refused to eat vegetables (Griffin et al. 2009). The unused part of meats such
as chicken skins and fats has contributed the lowest percentage because most people
consumed those parts of meat (Y-Sing 2007).
3.2 Physical Characterisation of Food Waste
The pH values of FWRL and FWDL fell in the range of 6.30–7.10, contrary to the
previous study done by Griffin et al. (2009) which between pH 3.0–4.0. The sample
in this study has undergone neutralisation due to the presence of calcium carbonate,
CaCO 3 , contributed by eggshell. CaCO 3 is an alkali, which when reacting with acidic
medium (food waste) will change properties to neutral (Hamer 2003). The TS and
VS of FWRL and FWDL were 42.9% and 94.29%, respectively, indicate that the
food waste was very high in organic content. These high values also suggest that
food waste is not suitable to be disposed on landfill, due to the high potential of
greenhouse gases (GHGs) release and odour problem.
The determination of TS and VS was done in order to determine the organic
loading rate of the substrate to be used in the AD process. According to Zhang et al.
(2005), AD process can be proceeded if the TS and VS values were approximately
137
of Mg
2+ was obtained using Atomic Absorption Spectrometer (AAS), at 285.2 nm
of wavelength (λ). Five (5) standard solutions with different concentrations (0.5,
1.0, 1.5, 2.0 and 2.5 ppm) were prepared from 1000 ppm of Mg standard solution
and used to generate a calibration curve. The concentration of NH 4
+ was determined
using Kjeldahl method (Buchi), where the concentration of PO 4
3− was determined
using UV-Vis Spectrophotometer (Cary 60), λ = 800 nm, using five (5) standard
solutions with different concentrations (1, 2, 3, 4 and 5 ppm) which were prepared
from 100 ppm of PO 4
3− stock solution. The chemical characteristics were carried
out using FWRL and FWDL according to the method described by APHA (2005).
3 Results and Discussion
3.1 Composition of Food Waste Samples
Figure 1 shows the percentage (%) of different components of food waste used in this
study, where vegetables and fruit peels comprised the highest percentage (45.73%)
followed by chicken and fish bones (19.68%), while unused part of meats contributes
the lowest percentage (0.62%). Other components were between 3.28 and 12.59%.
The sampling points and sampling period are the important factors, which may affect
the percentages. The unused vegetable parts such as stem and spoiled leaves that are
produced during food preparation stage may be the reason for its highest percentage.
In addition, the café may also produce a huge amount of vegetable leftovers as most
students refused to eat vegetables (Griffin et al. 2009). The unused part of meats such
as chicken skins and fats has contributed the lowest percentage because most people
consumed those parts of meat (Y-Sing 2007).
3.2 Physical Characterisation of Food Waste
The pH values of FWRL and FWDL fell in the range of 6.30–7.10, contrary to the
previous study done by Griffin et al. (2009) which between pH 3.0–4.0. The sample
in this study has undergone neutralisation due to the presence of calcium carbonate,
CaCO 3 , contributed by eggshell. CaCO 3 is an alkali, which when reacting with acidic
medium (food waste) will change properties to neutral (Hamer 2003). The TS and
VS of FWRL and FWDL were 42.9% and 94.29%, respectively, indicate that the
food waste was very high in organic content. These high values also suggest that
food waste is not suitable to be disposed on landfill, due to the high potential of
greenhouse gases (GHGs) release and odour problem.
The determination of TS and VS was done in order to determine the organic
loading rate of the substrate to be used in the AD process. According to Zhang et al.
(2005), AD process can be proceeded if the TS and VS values were approximately