Page 477 - Refining Biomass Residues for Sustainable Energy and Bioproducts

434 Refining Biomass Residues for Sustainable Energy and Bioproducts

19.2.2.1 Landfill

This is the most common approach for disposing of solid waste. Different stages
involved in landfill process are

1. aerobic phase,
2. anaerobic phase,
3. initial methanogenic phase, and
4. final methanogenic phase.
Kjeldsen et al. (2002) reported that additional oxidation phase is also required in
landfilling processes. Although the landfill is cheap to process and suitable for all
waste, the harmful gaseous emission is a major disadvantage.

19.2.2.2 Anaerobic digestion
Anaerobic digestion is an excellent practice to lessen food waste. It involves waste
degradation in the absence of oxygen. The product obtained in this process is biogas
such as methane, ammonia, and carbon dioxide along with a liquid product such as
fertilizers. This process involves the following steps:

1. Hydrolysis step
2. Acidogenesis step
3. Acetogenesis step
4. Methanogenesis step
Two types of a reactor can be used in the anaerobic digestion method, namely,
single phase and two-phase. In the two-phase reactor, hydrolysis and acidogenesis
steps occur in the first chamber, and methanogenesis occurs in the second chamber.
In single phase reactor, all the steps occur in one chamber. Many types of research
confirm that two-phase digestion system is better over a single one (Ren et al.,
2018).

19.2.2.3 Composting
It is the commonest approach used by the farmer to improve quality of the soil and
to increase the nutrient content in the soil. Composting follows two phases, namely,
thermophilic and mesophilic. According to Schaub et al., reports composting do
volume reduction up to 40% to get the solid product (Schaub and Leonard, 1996).

19.2.2.4 Incineration

It is a waste-management approach under which the waste undergoes temperature
up to 1200 C. The waste undergoes complete combustion to give carbon dioxide,

water, carbon monoxide, and other traces of gases. The heat released in the inciner-
ation process is used in heat exchangers. Although this process has advantages, it
applies to the type of waste where water content is low. As food waste has a high
amount of water, this process is not appropriate (Otles and Kartal, 2018).