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In international development programs on improvement of energy supply for cooking in remote regions, biomass gasifier cook stoves have a remarkable place. Fuel type and size play a key role on the performance of such stoves. The most abundant woody biomass waste in Iran is apple pruning waste (up to 1.32 Mt a year). This paper reports the result of evaluation of a top lit updraft biomass stove specifically modified to burn apple pruning waste. In addition, the improved biomass cooking stove (ICS) was technically compared with traditional cook stove (TCS) based on Water Boiling Test 4.2.3 and time to boil (TTB) instruction. Water and flame temperature variations were compared with a natural gas stove (GS), as the most common cooking device in Iran. The average TTB was 12, 13, and 20 min for the GS, ICS, and TCS, respectively. The comparison of regression equations indicated that the rate of increase in the flame and water temperature in the both ICS and GS were similar. In general, better thermal efficiency was observed in the ICS (about 35%) in comparison with the TCS (12.6%). The specific and the total fuel consumption in the ICS were 73 and 67% lower than that of the TCS, respectively. Keywords: Biomass waste, Thermal efficiency, Firewood, Regression model

Ultrasonic pre-treatment has been considered as an environmentally friendly process for enhancing the biodegradability of organic matter in anaerobic digestion. However the consumed energy during the pre-treatment is a matter of challenge especially where energy generation is the main purpose of a biogas plant. The aim of the present work was to study the efficiency of ultrasonic pre-treatment in enhancement of biogas production from fruits and vegetable wholesale market waste. Three sonication times (9, 18, 27 min) operating at 20 kHz and amplitude of 80 μm were used on the substrate. The highest methane yield was obtained at 18 min sonication (2380 kJ kg−1 total solids) while longer exposure to sonication led to lower methane yield. This amount of biogas was obtained in 12 d of batch time. The energy content of the biogas obtained from this reactor was two times of the input energy for sonication.