Valorization of organic wastes by anaerobic digestion for the generation of value-added products
Creators: name: BEGUM, Sameena
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400410
subject: Wastewater treatment processes
classificationCode: 401212
subject: Non-Newtonian fluid flows (incl. rheology)

description: Increased waste generation and energy demand are the consequences of rapid population growth and urbanization in most of the developed and developing countries. Hence, Reuse, Recycle and Recover are the 3 R's that needs effective implementation for strategic waste management system. Landfilling of Municipal Solid Waste (MSW) is the simplest and cost-effective method of disposing of MSW. There has been a rising interest towards the generation of renewable energy in the form of fuel, electricity, and heat from organic wastes. In addition to the solid organic wastes, landfill leachate (LL) generated from an MSW landfill is a major concern that still needs a viable treatment solution. So, the LL could also be valorized for the generation of value-added products (VAP) such as volatile fatty acids (VFA), bioethanol, hydrogen and methane-rich biogas through anaerobic digestion process. However, this study is focussed on the production of VFA and biogas only.

Anaerobic Digestion (AD) is one of the promising methods for waste treatment due to its environmental and economic benefits. Valorization of these wastes through the AD process not only meets the energy demand but also resolves the waste disposal issue. It is noteworthy to mention that the biogas generated during a single-stage AD process could be utilized directly as a cooking fuel or to generate electricity, BioCNG, etc. On the other hand, the market demand and economic value of VFAs is higher in lieu of biogas, therefore extraction of VFAs through different separation techniques is gaining interest. The substrates rich in VFA or the VFAs that are produced during the acidogenic phase could either be extracted with high purity or can be used as precursor feed to methanogens for biogas generation during two-stage AD process.
 
It is known that MSW is a combination of several organic wastes that include cardboard (CB) and food waste (FW) predominantly. It could be contemplated that AD of slowly biodegradable substrates like CB without any pre-treatment step in combination with an easily biodegradable substrate like FW for energy recovery could be the most attractive and remunerative method of waste management.

Due to existing collaboration between India and Australia (IICT and RMIT), an opportunity to work in these two continents, Indian LL and Australian FW was considered as a source of VFA rich waste while CB as another source of solid waste in this study. Australian FW was considered instead of Australian LL because of its low organic matter concentration (COD &lt; 5,000 mg/L).  Due to this matter, no biogas production was observed during batch AD tests. Therefore, the present study is aimed to valorize LL, FW and CB through the AD process for the generation of VAP such as VFA and biogas. Extraction of VFA as it is from LL was also considered.
 
Therefore, this project is investigated with the following three integral scientific objectives:
1. Can the VFAs (eg. in LL) be extracted as it is using any separation method?  
2. Can VFAs (eg. in LL) be utilized efficiently through stage-wise AD systems for the selective production of VFAs and/or biogas generation?
3. Can VFA (eg. in FW) be used as a source for the pre-treatment of poorly degradable substrates like CB (greased or waxed)?