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In the Brigalow Belt bioregion of Australia, clearing of brigalow (Acacia harpophylla) scrub vegetation for agriculture has altered nutrient cycling over millions of hectares. In order to quantify the effect of this vegetation clearing and land use change on soil fertility, the Brigalow Catchment Study commenced in 1965. Initial clearing and burning of brigalow scrub resulted in a temporary increase of mineral nitrogen, total and available phosphorus, total and exchangeable potassium and total sulfur in the surface soil (0-0.1 m) as a result of soil heating and the ash bed effect. Soil pH also increased, but did not peak immediately after burning. Soil fertility declined significantly over the subsequent 32 years. Under cropping, organic carbon declined by 46%, total nitrogen by 55%, total phosphorus by 29%, bicarbonate-extractable phosphorus by 54%, acid-extractable phosphorus by 59%, total sulfur by 49%, total potassium by 9% and exchangeable potassium by 63% from post-burn, pre-cropping concentrations. Fertility also declined under grazing but in a different pattern to that observed under cropping. Organic carbon showed clear fluctuation but it was not until the natural variation in soil fertility over time was separated from the anthropogenic effects of land use change that a significant decline was observed. Total nitrogen declined by 22%. Total phosphorus declined by 14%, equating to only half of the decline under cropping. Bicarbonate-extractable phosphorus declined by 64% and acid-extractable phosphorus by 66%; both greater than the decline observed under cropping. Total sulfur declined by 23%; less than half of the decline under cropping. A similar decline in total potassium was observed under both land uses, with a 10% decline under grazing. Exchangeable potassium declined by 59%. The primary mechanism of nutrient loss depended on the specific land use and nutrient in question.

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Management of solid waste is one of the major challenges faced by the municipalities. Solid waste mainly comprises of organic waste. Proper management of organic waste helps minimize solid waste problem. This study was carried out to assess the production of biogas from canteen’s organic waste as a solution for management of organic waste in Solid Waste Management Technical Support Centre, Lalitpur using innovative urban biogas plant with capacity 1,275 liters for 48 days. The physicochemical parameters of canteen’s waste and bio-slurry were analyzed. Similarly, volume of biogas, volume of methane and carbon dioxide in biogas produced were measured and CO2 reduction from biogas plant was identified. The average values of physicochemical parameters of canteen’s waste lied within the optimum range for biogas production. The biogas plant produced 22.03 liters/kg of waste and 120.47 liters/day of biogas. The produced biogas contained 48.89% methane and 39.11% carbon dioxide on average. The biogas plant could reduce 3.20 tones of CO2 equivalent per annum from 262.50 kg of waste fed for 48 days. The values of nitrogen, phosphorus and potassium of bio-slurry indicated it as a better fertilizer. Shapiro-Wilk test showed that the p-value of collected data were greater than 0.05 indicating normal distribution. Linear regression between ambient temperature and biogas production showed that the p-value less than 0.05 indicating significant relationship between them (r2=0.08). The estimated return period of the invested money was 9.5 months in kerosene substitution or 9.7 months in firewood substitution or 9.5 months in LPG substitution. Similarly, the estimated average rate of return was 125.26% in kerosene substitution or 123.72% in firewood substitution or 125.01% in LPG substitution. These results indicated that biogas production using innovative urban biogas plant is better solution for organic waste management. Further extensive and large scale research need to be carried out for the optimization of the biogas plant.

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