TY - JOUR
T1 - Ash-extracts from plant residues can provide sufficient buffering alkalinity and trace elements required to prevent operation instability to guarantee optimum methane yield during anaerobic digestion of agricultural residues
AU - Egwu, Uchenna
AU - Uchenna-Egwu, Beatrice
AU - Ezeokpube, Gregory Chukwuemeka
N1 - Funding information: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Nonetheless, in this manuscript, we duly acknowledged the financial support from TETFund Nigeria.
PY - 2021/10/10
Y1 - 2021/10/10
N2 - In this study, continuously stirred tank reactors (CSTR) operated at mesophilic temperatures were used to study the effectiveness of low-cost plant ash-extracts from plant residues in providing sufficient buffering alkalinity and trace elements required to prevent operational instability during an AD process to optimize methane productivity. The mean specific methane production (SMP) obtained from the unsupplemented CSTR was 79.3 N mL CH4/gVS fed, while supplemented reactors were 258.1 and 297.3 N mL CH4/gVS fed, respectively, corresponding to methane contents of 24.6 %, 56.7 % and 57.0 %, respectively. The unsupplemented CSTR failed when VFA accumulation occurred with acetic acid ranging between 2262–8917 mg/L, propionate-to-acetate (P: A) ratio 1:2.1–1:3.2 and a FOS: TAC ratio 0.2–1.4. Supplementation of the failed CSTR with ash-extracts increased the buffering potential of the reactors by decreasing VFA concentration leading to positive signs of recovery and a gradual increase in biogas production (p < 0.005). The soluble trace elements content in the ash-extracts and strong buffering alkalinity stabilized AD processes, improved SMP and facilitated the recovery of the failing CSTR. Thus, ash-extract supplements can increase the profitability of the AD process. The production and sale of ash can also support economic activities by creating a new business opportunity as the pathway to impact.
AB - In this study, continuously stirred tank reactors (CSTR) operated at mesophilic temperatures were used to study the effectiveness of low-cost plant ash-extracts from plant residues in providing sufficient buffering alkalinity and trace elements required to prevent operational instability during an AD process to optimize methane productivity. The mean specific methane production (SMP) obtained from the unsupplemented CSTR was 79.3 N mL CH4/gVS fed, while supplemented reactors were 258.1 and 297.3 N mL CH4/gVS fed, respectively, corresponding to methane contents of 24.6 %, 56.7 % and 57.0 %, respectively. The unsupplemented CSTR failed when VFA accumulation occurred with acetic acid ranging between 2262–8917 mg/L, propionate-to-acetate (P: A) ratio 1:2.1–1:3.2 and a FOS: TAC ratio 0.2–1.4. Supplementation of the failed CSTR with ash-extracts increased the buffering potential of the reactors by decreasing VFA concentration leading to positive signs of recovery and a gradual increase in biogas production (p < 0.005). The soluble trace elements content in the ash-extracts and strong buffering alkalinity stabilized AD processes, improved SMP and facilitated the recovery of the failing CSTR. Thus, ash-extract supplements can increase the profitability of the AD process. The production and sale of ash can also support economic activities by creating a new business opportunity as the pathway to impact.
KW - Biomass ash-extracts
KW - Continuously stirred tank reactors
KW - Process stability
KW - Specific methane production
KW - Supplementation
UR - http://www.scopus.com/inward/record.url?scp=85113263019&partnerID=8YFLogxK
U2 - 10.1016/j.jclepro.2021.128369
DO - 10.1016/j.jclepro.2021.128369
M3 - Article
AN - SCOPUS:85113263019
SN - 0959-6526
VL - 318
JO - Journal of Cleaner Production
JF - Journal of Cleaner Production
M1 - 128369
ER -