Citrus waste for different applications such as production
of pectin, flavonoid, fiber, and animal feed production has
been proposed by several researchers [5–8]. However, a large
amount of this waste is still dumped every year [9], which
causes both economic and environmental problems such as
high transportation cost, lack of dumping site, and accumulation
of high organic content material [10].Therefore, more
effective and sustainable alternatives for using orange peel
wastes such as biogas are highly desirable.