**1. Introduction**

The increase in population in urban areas results in an increase in the amount of municipal solid waste (MSW) generated. AusAID [1] reported that a total of 38.5 million tons of solid waste were generated annually by the 232 million inhabitants in Indonesia (450 gm per person per day), of the which, 21.2 million tons contributed by the inhabitants of the island of Java. The 26 biggest Cities in Indonesia inhabit a totally 40.1 million people, generating in total an estimated 14.1 million tons per year (about 1 kg per person per day). In this country, municipal waste is composed of 62% of mainly organic waste, 14% plastics, 9% paper, 2% glass, 2% rubber and leather, 2% metals, and 13% of other waste types [1].

These physical characteristics of solid waste are indicated as a potential source of biomass mainly their bioorganic contents. Biomass can be considered as the solar

energy stored in chemical bonds of organic material [2]. If the bond between carbon and hydrogen, and oxygen is broken down through decomposition, combustion, or decomposition process for these materials, the chemical energy stored or potential energy will be released [2]. Therefore, its energy content will be influenced by the elementary composition.

To determine the potential energy stored in the biomass, traditionally by direct measurement or theoretical approach. Direct measurements can be carried out by an experiment using a bomb calorimeter [3] and the theoretical can be determined from their elementary content such as carbon, hydrogen, oxygen, nitrogen, and sulfur [4]. In this, to analyze the potential of energy recovery required adequate biomass characteristics, especially in elemental compositions [4, 5]. In relation to the utilization of solid waste as an energy source, the investigation of their chemical elemental characteristics is beneficial to the suitable choice of energy conversion technologies including bioconversion, incineration, or thermochemical conversion processes.

However, there is lack of data associated with the chemical elemental characteristics of solid waste in Indonesia. Based on their elemental chemical characteristics, the energy content of solid waste fuel can be calculated from the heat of combustion. In the combusting, fuel will release its energy potential. The energy released or the heat of fuel combustion is heat when a fuel undergoes complete combustion with oxygen under standard conditions. It can be calculated as the difference between the heat of the formation of the products and reactants. In this, a chemical equation is required. The heat of the formation of the products and reactants can be obtained through a thermochemical table [4]. This change of the enthalpy approach is a thermochemical conversion process based. Estimation of the potential energy from organic waste fuel can also be determined by using the Buswell equation. Buswell [6] suggested a general equation for the anaerobic bioconversion process of biodegradable organic matter. This second way either requires stoichiometric equations for the bioconversion process or the biodegradability of waste. The biodegradability of organic solid waste can be expected from its volatile solid and lignin content [6].

Besides based on the theoretical way, the elementary characteristics data can also be used to estimate the calorific value or energy content based on their empirical relationship. Researchers in several countries have carried out extensive research to determine the empirical relation between the elemental and calorific value of biomass and solid waste fuel [4, 7–12]. The energy content of the estimation results can then be used to estimate the quantity of energy that can be recovered on fuel. Therefore, both through direct measurement, stoichiometric approach, as well as the empirical relationship can be used as a basis for estimating energy recovery from organic solid waste.

This paper aims to estimate energy content and recovery potential organic component of MSW by using experiment, theoretical, and empirical approaches. The energy recovery potential is determined by the combustion and anaerobic digestion process.
