The unified Sudan has been producing oil since the 1990s. Most of the producing assets are near or extend across the de facto border between Sudan and South Sudan. When South Sudan became independent in July 2011, it gained control over most of the oil production. However, South Sudan is landlocked and remains dependent on Sudan because it must use Sudan's export pipelines and processing facilities. Total primary energy supply in Sudan is largely dependent on oil, yet, oil production in Sudan and South Sudan is declining because of natural declines at maturing fields. The unified Sudan generated 8.1 billion kilowatthours (KWh) of electricity in 2010. Almost all was generated from oil (3.8 KWh) and hydroelectricity (3.8 KWh), with the remaining 6 percent from biomass and waste (0.5 KWh).