Municipal solid wastes as food wastes, cattle dung and sewage sludge require a proper and environmentally accepted management before final disposal, they are considered a major source of air and water pollution. We can invest the energy generated as biogas and production of high quality compost in addition to free pathogen soil fertilizer while achieving environmental and economic benefits. The objective of this study was to investigate the feasibility of biogas and methane production from food wastes and cattle dung in the first experiment. The second one is the production of biogas and methane from sludge and cattle dung by co-digestion system under mesophilic conditions. The experiment done in the bench scale batch anaerobic digester (vertical type) with 8.5 liter capacity, 6 liter digestion volume, stirrer 80 rpm/min and 85 days hydraulic retention time (HRT) under 36 °C mesophilic conditions and the mixing ratio 50:50%, with total solid (8% TS) after dilution for both experiment. The results showed that, the biogas and methane yield were 0.122 L biogas/g VS and 0.078 L CH4/g VS at 50% TS of in the mixture of food wastes and cattle dung, but this ratio receded in case of sludge and cattle dung where the biogas and methane yield were 0.093 L biogas/g VS and 0.062 L CH4/g VS at 50% TS. On the other hand the produced biogas percentage was higher in case of sludge and cattle dung (66%) than food wastes and sludge which was (63.9%). The equilibrium between carbon dioxide and methane production was dependent on acetogenic, methanogenic bacteria, degradation percent and pH value. When the degradation ratio increased and pH value decreased; the percentages of CO 2 increased and CH 4 % decreased. Also when the degradation% increased and pH value increased, the carbon dioxide decreased while methane content is increased. The methane percentage is influenced by the C:N ratio, which increased and in the same time the average CO 2 % is decreased. Recent research demonstrates that using co-substrates in anaerobic digestion systems improves biogas yields.

Waste is an old dilemma for the environment and societies. This paper aims to propose an integrated method to reduce amount of waste packaging by enhancing reusable packaging in societies and industries. In the first phase, a System Dynamic (SD) method will be used for determining the interaction between the social aspects and reusable behaviour. The second phase will devote to exploring reusable packaging attributes by using Normal Average and Codes and Coding approaches. The last phase will conduct of a case study of a real company which needs to reduce waste packaging. Data was collected by evaluation of consumers' responses and experts' experiences as provided in the questionnaires. The results shown that a Social Behaviour Aspect Model (SBAM) demonstrated the importance of spreading the awareness of environmental behaviour to develop personal, social values and norms within communities. Moreover, a Reusable Packaging Attributes Model (RPAM) proved that the existence environmental packaging can help consumer to behave environmentally and reduce waste packaging. In conclusion, this paper can help government to investigate the most suitable approach for reduce the environmental impact of waste packaging by enhancing the use of reusable packaging within societies and industries. 

The concrete is considered a versatile construction material. The concrete comprises of fine aggregate, coarse aggregate and cement paste (cement and water). The cement paste is the binding material for aggregates in concrete. Local natural pozzolan (LNP) is found in Almadinah Almunawara, KSA. LNP can be used as partial substitution for cement and fine aggregates in lightweight concrete. This paper presents an investigation of the effect of partial replacement of cement with LNP powder in cement mortar cubes to reduce the harmful environmental impact of carbon dioxide emission resulting from cement manufacturing and the effect of partial replacement of fine aggregate in cement mortar cubes with LNP on the mechanical properties of mortar cubes. It was recommended by Saudi Building Code to add pozzolan with cement of special type in the production of concrete exposed to severe sulfate. A fifty-four cement mortar cubes of 50 mm were made (six cubes as control specimens, twenty-four cubes with cement replacement by weight with local natural pozzolan powder at replacement levels of 10, 20, 30 and 40%, and twenty-four cubes with sand replacement by volume with local natural pozzolan at replacement levels of 10, 20, 30 and 40%). The cement mortar cubes were tested at 28 and 180 days. The replacement of sand by volume with local natural pozzolan showed a notable effect on the mechanical properties of cement mortars when compared with the replacement of cement by weight with local natural pozzolan powder.

Solid waste management options require the integration of economic and environmental principles in order to select the best management method. This study analysed municipal solid waste (MSW) generation, composition and collection of Madinah region, as one of largest cities in KSA with the aim of finding a management method with minimum cost. The study aimed to provide an overview of current state of MSW management and recommendations for improving the waste treatment and management system in this area based on the significance of environmental and financial aspects. These recommendations would be not specific to Madinah region, but also would be applied to other cities in KSA or any other regions with similar features. The analysis results showed that the trend of waste generation would be increased as much as two to three folds in 2030. Approximately 30% of total generated waste is disposed to a sanitary landfill, while 70% is sent to normal dumpsites. The results of environmental and finical analyses recommended the recycling and energy recovery managements options for this type of wastes in this area. The results revealed that the worst scenario for solid waste management is just landfilling whereas the money-back is zero and the best scenario is implementation the composting process for the organic portion of the waste and recycling the other items.