| The amount of kitchen waste and environmental safety issue become the focus of attention with the social and economic development as well as improvement of living standards and environmental awareness. It is very imminent to find a solution to effective kitchen waste disposal. On the other hand, due to the increasing depletion of traditional energy and pollution problem caused by the traditional energy, development of clean and efficient energy get more and more attention around the world. Methane production from kitchen waste by anaerobic digestion, not only can get the organic waste recycling, but also obtain the unification of environment benefit, society benefit and economy benefit.This paper comprehensively studied on methane production from kitchen waste by anaerobic digestion. The basic characteristic of the kitchen waste was investigated. On this basis, the paper studied on influencing factors and preliminary optimized conditions of anaerobic fermentation of kitchen waste. Then the anaerobic fermentation of kitchen waste in laboratory test and pilot test were performed. The main conclusions of this paper are as follows:Kitchen waste is a typical high solid organic substance. The average moisture content was79.82%. Total solid and volatile solid contents were17.10%and15.77%respectively. The average content of oil was3.09%. The average content of C, H, N, C/N, K, Ca, Na, Mg, P were50.65%,8.18%,2.34%,21.84%,0.57%,1.17%,1.32%,0.07%and0.67%respectively. Kitchen waste did not contain heavy metals other than Cu, Zn and Hg outside. The content of crude protein, crude fat and total starch followed by12.87%,20.77%and24.06%. Content of each component was smaller variety with the seasons.Compared with the manure and anaerobic sludge, fermented cow dung is more suitable as inoculum. In the batch fermentation experiments, the cumulative gas production of reaction systems of different inoculation rates (90%,85%,80%,75%,70%and65%) followed by1762mL,3233mL,4111mL,6132mL,6466mL, and8467mL. The reaction system of75%inoculation rate was the best, the biogas yield reached to426.2mL·g-1TS and the methane yield reached to811mL·g-1VS. The cumulative gas production, gas production rate of dry matter and the removal rate of total solid increased with the oil content of kitchen waste. But the digestion period was longer with the smaller inoculation rate and the larger oil content. It would have adverse impact on the continuous feeding of anaerobic digestion. Salts had more pronounced inhibition on anaerobic digestion. The influence of hydrolysis acidification was less on the treatment. But at room temperature should not be put more than four days.The average daily gas production were17.38L·d-1,24.56L·d-1and28.31L·d-1respectively when the organic load of2.45gVS·L-1d-1,3.67gVS·L-1d-1and4.28gVS·L-1d-1under conditions35℃, continuous feeding. The gas production rates were0.71L·g-1(VS) d-1,0.67L·g-1(VS) d-1and0.66L·g-1(VS) d-1. When the feed load was4.89gVS·L-1d-1, the reaction can not carry out stably by acidosis.It was found that the maximum feed organic load of digestion with kitchen waste was4.28gVS·L-1d-1, the gas production rate of the system was0.66L·g-1VS, and the proportion of dry matter of kitchen waste and fermented liquid controlled by1:6.2. The methane content in biogas is63%averagely. The removal rate of TS and VS were49.6%and53.4%respectively. As a result, about80m3of methane could thus be generated corresponding to1ton kitchen waste (removal of oil) with86.64%moisture content,91.56%VS.Through the analysis of biogas slurry, VS (dry basis) was55%to60%, carbon and nitrogen ratio of10:1and pH was6.8to7.2. The heavy metal content were in line with the requirements of bio-organic fertilizer. So biogas slurry can be used as raw material of bio-organic fertilizer. |
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