Enhanced Biogas Production of Cassava Wastewater Using Zeolite and Biochar Additives and Manure Co-Digestion

Chibueze G Achi,Amro Hassanein,Stephanie Lansing

doi:10.3390/en13020491

Chibueze G Achi, Amro Hassanein + Show 1 more

Open Access

https://doi.org/10.3390/en13020491

Copy DOI

Abstract

Currently, there are challenges with proper disposal of cassava processing wastewater, and a need for sustainable energy in the cassava industry. This study investigated the impact of co-digestion of cassava wastewater (CW) with livestock manure (poultry litter (PL) and dairy manure (DM)), and porous adsorbents (biochar (B-Char) and zeolite (ZEO)) on energy production and treatment efficiency. Batch anaerobic digestion experiments were conducted, with 16 treatments of CW combined with manure and/or porous adsorbents using triplicate reactors for 48 days. The results showed that CW combined with ZEO (3 g/g total solids (TS)) produced the highest cumulative CH4 (653 mL CH4/g VS), while CW:PL (1:1) produced the most CH4 on a mass basis (17.9 mL CH4/g substrate). The largest reduction in lag phase was observed in the mixture containing CW (1:1), PL (1:1), and B-Char (3 g/g TS), yielding 400 mL CH4/g volatile solids (VS) after 15 days of digestion, which was 84.8% of the total cumulative CH4 from the 48-day trial. Co-digesting CW with ZEO, B-Char, or PL provided the necessary buffer needed for digestion of CW, which improved the process stability and resulted in a significant reduction in chemical oxygen demand (COD). Co-digestion could provide a sustainable strategy for treating and valorizing CW. Scale-up calculations showed that a CW input of 1000–2000 L/d co-digested with PL (1:1) could produce 9403 m3 CH4/yr using a 50 m3 digester, equivalent to 373,327 MJ/yr or 24.9 tons of firewood/year. This system would have a profit of $5642/yr and a $47,805 net present value.

Highlights

Eutrophication and organic pollution resulting from poor management of wastes from food processing industries, such as cassava processing industries, is a major problem in many developing countries [1,2]
Anaerobic digestion of cassava wastewater was shown to be viable, with CH4 production enhanced by additions of zeolite and biochar
Co-digestion with dairy and poultry manure decreased the lag phase of digestion but did not increase overall CH4 production, likely due to the more recalcitrant materials within the manure feedstock compared to cassava wastewater (CW)

Summary

Introduction

Eutrophication and organic pollution resulting from poor management of wastes from food processing industries, such as cassava processing industries, is a major problem in many developing countries [1,2]. More than 70% of cassava production in sub-tropical and tropical regions of the world is conducted by small and medium-scale farmers [7,8]. These small and medium-scale cassava industries lack the capacity to treat the large waste streams resulting from daily cassava roots processing, which can lead to environmental degradation and pollution of nearby water bodies [9].

Objectives

Methods

Results

Conclusion