Anaerobic Digestion of Kitchen Waste to Produce Biogas

Abstract

Kitchen waste (KW) can be utilized to produce biogas due to its high biodegradability, calorific value and nutritive value to microbes, which will reduce our dependency on fossil fuels. The research work was conducted to investigate the production ability of biogas as an alternative energy from KW with co-digestion of cow manure (CM) through anaerobic digestion (AD). Firstly, three digesters were prepared to observe the individual degradation rate of KW, CM and co-digested KW with CM at room temperature (25°C~30° C) and at temperature of 37°C (mesophilic digestion) respectively and observed the degradation rate for co-digested KW with CM was higher than KW and CM alone. Secondly, three digesters were constructed to observe the effect of alkalinity at temperature 37° C and loading rate 200 gm/L. Three alkali (NaOH) doses 1.0%, 1.5% and 2.0% on wet matter basis of kitchen waste were applied to improve biodegradability and biogas production. The highest degradation rate was 6.8 ml/gm which was obtained from 1.5% NaOH and also observed that biogas production was almost doubled from treated KW than untreated KW. Finally, a portable biogas reactor was fabricated for pilot-scale biogas production which included an agitator and heating system. This reactor was operated at both 37° C and room temperature at a loading rate of 200 gm/L and observed that the digestion rate was faster at 37°C than room temperature. The prime object of this work was to investigate the prospect of kitchen waste for biogas production and ultimate protection of environment from the bad effect of methane gas that would be produced by uncontrolled anaerobic digestion.

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“…By comparison, the volume of biogas formed from slurry of cattle dung was less than that formed from kitchen food waste in cattle urine probably due to kitchen food waste providing a better nutrient balance for carbon to nitrogen than cattle dung which was largely lignified cellulose [40]. The microbes survive better in media containing more nitrogen than those containing less because nitrogen is an essential element for their life.…”

“…As shown on Figure 3, the rate of evolution of biogas from mixed aqueous slurry of cd and kwf was higher than single substrate because the combination brought together the positive characteristic of feed stocks and potentially bringing better digestion performance as well as more rapid growth of microbial population in the mixed substrate than in the single substrate [40,44].…”

“…The production of biogas started by day 3 of experiment showing that the time between set up of experiment and initial formation of gas was not utilized by the anaerobes to act on the slurry. This has been explained as time used by the anaerobes to use up oxygen present in the slurry; and after oxygen is depleted, acid forming anaerobes became active so gas production started [40].…”

“…Production of biogas increased steadily at first and then sharply after day 9 until it attained its peak on day 18. When gas production had just begun, the microbes in the slurry had just become active and began increasing their population [40]; and the microbes needed acclimatization period [41].. The steady increase in biogas was explained by the fact that the microbes' population was fully established in large enough numbers and were therefore progressively acting on more and more substrate as their numbers increased [40].…”

Assessment of Economical Biogas Production From Chilean Municipal Solid Waste in a Decentralized Off-Grid Strategy

“…In addition, it must be mentioned that co-digestion of FW with other household waste streams has not been considered. In spite of literature has demonstrated that specific biogas yield (SBY) is certainly improved by co-digestion (Iqbal et al, 2014) the potential inhibition of AD (e.g. detergents or papers towels) would make the proposal less reliable (Chen et al, 2008).…”