2.17.1 Potential of food processing waste

In this chapter, the example of Thailand is given to show the utilization of food processing waste. As one of the agricultural based countries, food industry sector plays an important role in Thai economy and also is worth a great fraction of Thai export value each year. The processing of food and its related commodity often involves thermal, mechanical and chemical treatment, which reluctantly poses environmental problems on proper treatment of the food processing waste. Broadly, food processing waste can be categorized into two types, according to its physical states, namely solid and liquid wastes. Solid waste varies from empty oil palm bunches, baggase, rice straw/stubble/husk, waste from cassava starch factory and corncob. On the other hands, liquid waste mainly comes from any food processing that involves washing, cleaning, extracting with water or any other solvents.

Conventionally, solid wastes have often been thrown back into the boiler in order to generate steam for the plant processing itself or power generation. With biomass technology like gasification, solid wastes find higher efficiency conversion to energy than simply uncontrolled burning. On the other hand, since liquid wastes are regulated for environmental concern, processing plants are required to install wasted water treatment system. Often such system is of an anaerobic digestion technology, from which biogas can also be produced and used as energy source in the plants.

From the Ministry of Energy evaluation back in 2000, the first nine industries of high potential for biogas production are of cassava, sugar, palm oil, canned seafood, frozen product, slaughterhouse, canned pineapple, carbonated soda and liquor, respectively. Recent investigation on the wasted water from cassava, sugar, oil palm, canned pineapple and ethanol plants to assess the biogas potential was conducted by TRF (http://www. trf. or. th). The results are shown in Table 2.17.1. Cassava plant has the highest potential to produce biogas, more than twice the runner-up ethanol plant. Some reasons for seemingly low potential of biogas production in certain industries are the better management of waste water treatment system and also better by-product utilization.