Abstract
Energy is a crucial input for the development and improving livelihoodof any nation.
Anaerobic co-digestion, which is largely lacking in Bangladesh,could be one of the best
solutions for mitigating energy crisis. The objectives of this study were (i) to
investigate the potentials, status, problems, barriers and future needs for
implementation and dissemination of biogas plants in Bangladesh and (ii) to find out
the optimal conditions for maximal biogas and bio-methane production.A baseline
survey and 5 lab based experiments were carried out for three consecutive years from
June 2015 to June 2018 to fulfill the objectives and find out the best solution of
anaerobic co-digestion of locally available biomassesin Biogas plants. The survey
results revealed that poultry and dairy industry is an increasingly growing and a
promising sector and the total poultry and dairy wastes have the theoretical biogas
potential of 39 TJ per annum which can solve a big portion of deficit energy. The smart
use of poultry and dairy wastes (biogas production and or electricity generation along
with organic fertilizer through anaerobic digestion (AD)) can be a sustainable energy
solution for Bangladesh. The results indicate that the initial total solid (TS) influenced
the AD performance significantly and modeling showed that the optimal initial TS
content for AD of poultry dropping (PD), press mud (PM) and sugarcane bagasse (SB)
ranged between 12-13%.The only exception was sugar beet roots and tops (SRT),
where atinitial TS content of 8% performed better. Augmented simplex centroid
design was used to design the mixture composition for the anaerobic codigestion. The maximum volumes of methane were obtained 48.5 NL CH4 kg-1 VS at
mixture proportion of 66.67% of PM, 16.665% of PD and 16.665% of SB for set A and 44
NL CH4 kg-1 VS at mixture proportion of 50 % of PM and 50% of PD for set B.
Synergistic effectsof methane productivitywere observed by adding a greater
proportion of PM for both the sets of A and B. The suitable operating temperatures
were found to be 35°C to 45°C for co-digestion of PD+PM and optimum operating
temperature was found 44°C at which the maximum specific methane yield and
percent volatile solid destruction(PVSD) were 260 NL kg-1VS and 57.52%,respectively.
The highest methane contents were 330 and 340 NL kg-1 VS after digestion for 90 days
at a mixing ratio of, respectively, 70:30 (PD:WS) with a C:N ratio of 32.02 and a mixing
ratio of 50:50 (PD:MG) with a C:N ratio of 31.52. The increases of methane were 1.14
and 1.13 times those of the LCSs alone, respectively. Co-digestion of PD with
briquetted wheat straw (BWS)add at thermophilic temperatures resulted in a higher
methane volumetric yield per kg substrate compared to mesophilic conditions. With
and without additive, co-digestion with BWS produced 8% and 11% higher yields at
thermophilic conditions than at mesophilic conditions. Co-digestion of PD with
BWSadd resulted in, respectively, 14% and 27% more methane produced at mesophilic
and thermophilic conditions over mono-digestion of PD. Successful implementation of
the findings of the study may improve the production of biogas or bio-methane to
mitigate the challenges of energy crisis.