The global rapid population growth and increase in energy consumption has caused the reduction of fossil fuels and non-renewable energy resources. Furthermore, the environmental problems caused by the fossile fuels consumptions make the production and use of clean and renewable energy more necessary. On the other hand, a large amount of waste is produced by agricultural industries, making severe environmental problems. Citrus wastes containing different soluble and insoluble carbohydrate polymers, is a suitable substrate for production of valuable materials such as limonene oil, pectin, and biofuels. Separation of valuable substances from orange peel is examined in the present study. In order to separate and reduce the amount of limonene in orange peel and prevent environmental pollution, simple distillation system was applied. In this approach, pretreatment with sulfuric acid, sodium hydroxide, and water pretreatment (auto hydrolysis) was used to improve the extraction efficiency. After pretreatment and limonene oil extraction, the pectin of orange peel was extracted from the liquid sample produced by pretreatment. The results show that acidic pretreatment was the most effective method for pectin extraction and biogas production. In this type of pretreatment,distillation of the wastes supplemented with 0, 0.5, 1 and 2% acid was used for 30, 60 and 90 min. Limonene was extracted with the amount of 30 ml oil/1 kg of fresh substrate with a purity of 83%. Among pretreated samples, the maximum amount of pectin extraction was 23.5% of dried solid with 69.3% purity. According to the achieved purity, 124 gr pure pectin per each kilogram of dried substrate can be extracted. Afterwards, citrus waste residue was used for biogas production in order to produce energy. The results of biogas production samples showed that pretreatment increased the amount of biogas production. The highest methane production was achieved by the acidic treatment (liquid sample produced by pretreatment) with the 1% sulfuricacid for 60 minutes, resulted in the methane yield of 349 ml /g. VS. According to the results of different experiments, it was observed that there is an increasing trend in the extraction of pectin and biogas production with increaseing time and acid concentrations. Destruction of carbohydrates in high concentration of acid and long exposure time caused a decreasing trend in the extraction of products. In order to evaluate the effect of treatment, SEM and FTIR analyses were performed on the optimum samples. SEM images of the samples showed increased levels of available surfaces and also the increased porosity and roughness due to the pretreatment. Moreover, FTIR results showed the similarity of produced pectin and commercial pectin. . Keywords : citrus waste, pectin extraction , acidic pretreatment, biogas