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

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.

Biogas Production from Organic Wastes: Integrating Concepts of Circular Economy

“…These strategies may aid in improving the performance of high-solid digestion and solid-phase reactors, given the high tendency of accumulating an excessive amount of inhibitors because of the lower volume of the diluting agent. Petracchini et al [102] reported the performance of HSAD of food waste and cow manure when adding natural zeolite to the reactor, obtaining biogas yields of 680-920 mL/g VS. Adsorbents have the capacity of reducing inhibitory levels of ammonia and total VFA concentration, thus allowing stable digestion to proceed [103,104]. Cuetos et al [105] demonstrated this better performance when evaluating the digestion of poultry blood.…”

High-Solid Anaerobic Digestion: Reviewing Strategies for Increasing Reactor Performance

“…The addition of adsorbents and carbon conductive materials to anaerobic reactors has been evaluated with success to decrease the impact of inhibitory compounds [87,88]. Adding this type of supplement to digestion allows for the enhancement of biogas productivity without greatly affecting the energy demands of the process [89].…”

Bio-Electrochemical Enhancement of Hydrogen and Methane Production in a Combined Anaerobic Digester (AD) and Microbial Electrolysis Cell (MEC) from Dairy Manure

“…Following Call and Logan (2008), the energy dissipation in the 10 Ω resistor (W E ) was accounted for in order to determine the actual energy supplied [23]. Gibbs' free energy equation was used to calculate the energy production from CH 4 (∆G CH4 = 890.4 kJ/mol) and H 2 (∆G H2 = 237.1 kJ/mol) [4,24,25].…”

“…Similarly, the calculated electricity and heat production from a CHP generator was more than double with MEC inclusion compared to AD-only. Previous studies have found the potential electricity production for dairy manure digestion to be between 0.08 and 1.8 kWh/m 3 /d over the entire digestion period [25,50]. By adding an MEC system to just the last 11 days of digestion, the dairy manure electric output went from the lower part of this range to the upper part of this range, while accounting for the electric input needed to operate the MEC.…”