3.4. The Overall Process of Methane Production and Limonene Extraction. One benefit of leaching pretreatment method is
to recover the limonene that is a flavor compound in orange belonging to terpenoid group.As flavor compound, limonene
holds widespread application in food, feed, cosmetic, chemical, and pharmaceutical industry. In themarket of flavor, food
and beverages is the largest which contributes to 47% of total demand in 2003 .