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Three common pretreatments (mechanical, steam explosion and chemical) used to enhance the biodegradability of rice straw were compared on the basis of bio-hydrogen production potential while co-digesting rice straw with sludge under mesophilic (37˝C) and thermophilic (55˝C) temperatures. The results showed that the solid state NaOH pretreatment returned the highest experimental reduction of LCH (lignin, cellulose and hemi-cellulose) content and bio-hydrogen production from rice straw. The increase in incubation temperature from 37˝C to 55˝C increased the bio-hydrogen yield, and the highest experimental yield of 60.6 mL/g VS removed was obtained under chemical pretreatment at 55˝C. The time required for maximum bio-hydrogen production was found on the basis of kinetic parameters as 36 h-47 h of incubation, which can be used as a hydraulic retention time for continuous bio-hydrogen production from rice straw. The optimum pH range of bio-hydrogen production was observed to be 6.7˘0.1-5.8˘0.1 and 7.1˘0.1-5.8˘0.1 under mesophilic and thermophilic conditions, respectively. The increase in temperature was found useful for controlling the volatile fatty acids (VFA) under mechanical and steam explosion pretreatments. The comparison of pretreatment methods under the same set of experimental conditions in the present study provided a baseline for future research in order to select an appropriate pretreatment method.

Abstract. The effect of temperature on bio-hydrogen production by co-digestion of sewerage sludge with food waste and its two derivatives, i.e. noodle waste and rice waste, was investigated by statistical modelling. Experimental results showed that increasing temperature from mesophilic (37 • C) to thermophilic (55 • C) was an effective mean for increasing bio-hydrogen production from food waste and noodle waste, but it caused a negative impact on bio-hydrogen production from rice waste. The maximum cumulative biohydrogen production of 650 mL was obtained from noodle waste under thermophilic temperature condition. Most of the production was observed during the first 48 h of incubation, which continued until 72 h of incubation. The decline in pH during this interval was 4.3 and 4.4 from a starting value of 7 under mesophilic and thermophilic conditions, respectively. Most of the glucose consumption was also observed during 72 h of incubation and the maximum consumption was observed during the first 24 h, which was the same duration where the maximum pH drop occurred. The maximum hydrogen yields of 82.47 mL VS −1 , 131.38 mL COD −1 , and 44.90 mL glucose −1 were obtained from thermophilic food waste, thermophilic noodle waste and mesophilic rice waste, respectively. The production of volatile fatty acids increased with an increase in time and temperature in food waste and noodle waste reactors whereas they decreased with temperature in rice waste reactors. The statistical modelling returned good results with high values of coefficient of determination (R 2 ) for each waste type and 3-D response surface plots developed by using models developed. These plots developed a better understanding regarding the impact of temperature and incubation time on bio-hydrogen production trend, glucose consumption during incubation and volatile fatty acids production.

In urban areas, management of solid waste is a big and serious issue because of high amount of waste generated from different sources (industries, domestic etc.). In Lahore solid waste generated daily is about 5000 ton comprising of around 60% biodegradable and 40% non-biodegradable waste. About 70% of waste is collected which is then disposed of in unmonitored dumping sites. It causes severe environmental problems. The present study is for minimizing the solid waste being collected. Composting technique was adopted from Municipal solid waste and garden waste. The aerated composting technique made results more efficient by using an effective microbe's solution which acts as an activator to enhance microbial activity and reduced the composting period. The results demonstrated that compost was good in organic content 25% and carbon-nitrogen ratio 26:1. It was planned to convert organic waste into compost thus substantially reducing the MSW loads being generated in Lahore.