**4. Renewable biomass sources**

Like any developing country, the Philippines is facing a formidable challenge of promoting sustainable energy options to support the energy requirements of its economic and social development goals with minimal adverse effects on the environment. The Philippines utilizes renewable energy sources including hydropower, geothermal and solar energy, wind power and biomass resources. In 2015, these sources contributed 20,963 GWh of electrical energy, out of which, 41% is hydropower while 53% is geothermal power. Solar energy, wind power and biomass energy application accounts for around 6% of the primary use in the country. These renewable energy sources represent 25.44% of the country's energy needs [19].

#### **4.1. Coconut leaf, cogongrass and rice husks as a renewable source of energy**

Among the coconut farm wastes such as husks, shell, coir dust and coconut leaves, the latter is considered either the most grossly under-utilized or completely un-utilized, only to be utilized by in situ burning at the coconut farm in order to dispose. A study conducted by Banzon [20] considered only the petiole to assess the fuel potential of the coconut leaf. Banzon reported that 376.9 million trees each producing at least 12 leaves a year or a total of 45 × 108 leaves with a total weight of 4000 kcal/kg (16.7 MJ/kg) makes the energy available from the coconut petiole equal to 39 × 1012 kcal [20, 21].

*Imperata cylindrical*, or cogongrass grows all around the world, including the Philippines. In general, cogongrass is composed of three main components: **C**ellulose, hemicellulose, and lignin [22]. Cellulose and hemicellulose can be converted into fermentable sugars and produce a large amount of fuels and chemicals by fermentation and chemical processes [23]. *Imperata*

is being considered as a feedstock for bioethanol. Very few studies have reported the use of cogongrass as a renewable energy source.

Agricultural wastes such as rice husks are now used as a source of energy that helps advance the agriculture industry, particularly on rice mechanization and post production operations. The Philippines produces an average of 2 million metric tons of rice husks annually. A kilo of rice husk basically contains about 3000 kcal of heat energy and can provide sufficient amount of clean gaseous fuel when gasified. Converting this available biomass waste into energy by gasification can provide about 25 pJ of energy which can be utilized for various heat and power applications, especially in rice farming and rural-based operations [24].
