Abstract
Alkali and acid chemical pre-treatment for lignocellulosic biomass can affect the amount of energy harvested from it during the anaerobic digestion process. This study aimed to assess the biogas production of dairy cattle manure subjected to acid and alkaline pre-treatment. This assay was performed in two phases, which consisted of 10 days of pre-treatment and 120 days of anaerobic digestion. The substrates for pre-treatment and anaerobic digestion phase were calculated to attain 5% of total solids (TS). Pre-treatment phase was conducted during 10 days and the following experimental treatments were used: Control (Water); 2.5% of hydrochloric acid (HCl-2.5%), 2.5% of dolomite limestone (DI-2.5%), 5.0% of hydrochloric acid (HCl-5.0%) and 5.0% of dolomite limestone (DI-5.0%). After this phase, pH of all substrates had their values corrected to the start of the anaerobic digestion phase. Higher volatile solids reduction was attained by treatment Dl-5.0% whose biogas production and biogas yield per kg of waste was significantly higher compared to control treatment. Cattle manure pre-treated with 5.0% of dolomite limestone for 10 days incremented the biogas yield per kg of waste.
Highlights
Anaerobic digestion has been widely used as a wastewater treatment method in livestock production systems mainly due to growing environmental problems such as air, soil and water pollution caused by gaseous emissions and uncontrolled disposal of waste
Might be noticed that TS values ranged from 13.29 to 18.53%, there was no statistical difference (P>0.05) for total solids reductions between all treatments compared to the control
This may be explained by the highest destruction of degradable components and biogas production attained by that treatment (Table 1) in which was used an alkaline pre-treatment
Summary
Anaerobic digestion has been widely used as a wastewater treatment method in livestock production systems mainly due to growing environmental problems such as air, soil and water pollution caused by gaseous emissions and uncontrolled disposal of waste. During the process of anaerobic digestion (AD), microorganism breakdown biomass in absence of oxygen transforming it in a mixture of gases that typically consist in 60-65% of methane (CH4), 3540% of carbon dioxide (CO2), and traces of ammonia (NH3), hydrogen sulfide (H2S) and nitrogen (N2) (TAUSEEF et al 2013). Cattle manure can yield low biogas production since it has lignocellulosic structures of low degradability rate (VANHOLME et al 2010). These structures are basically compound by cellulose, hemicellulose and lignin (CARRERE et al 2016), this last, branch biopolymers of complex phenolic nature that confers resistance to the vegetal cell has low degradability rate by enzymatic and microbial action
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