Anaerobic Digestion of Digested Manure Fibers: Influence of Thermal and Alkaline Thermal Pretreatment on the Biogas Yiel
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Anaerobic Digestion of Digested Manure Fibers: Influence of Thermal and Alkaline Thermal Pretreatment on the Biogas Yield Muhammad Usman Khan 1,2 & Birgitte K. Ahring 1,2,3 Received: 26 June 2020 / Accepted: 27 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Anaerobic digestion (AD) of animal manure converts only half of the organic material into biogas due to the presence of a significant amount of lignocellulosic materials in manure. In this study, alkaline thermal pretreatment was used for improving anaerobic digestion of residual manure fibers after AD. Anaerobic digestion of pretreated manure fibers was done in batch culture under mesophilic and thermophilic conditions. The results of the study showed that degradation of manure fibers was improved ca. 43.6% as a result of alkaline thermal pretreatment with 3% w/w NaOH added. Methane yield improved by 143.5 and 180.2% under mesophilic and thermophilic conditions, respectively. Compositional analysis of the effluent after AD showed the percentile conversion of 50.8% of cellulose, 59.5% of hemicellulose, 39.9% of acid-soluble and 21.7% of acid-insoluble lignin to methane under mesophilic conditions. Under thermophilic conditions, 57.3% of cellulose, 70.1% of hemicellulose, 39.4% of acid-soluble and 19.4% of acid-insoluble lignin were converted to methane. The result showed that alkaline thermal pretreatment of manure fibers can enhance the performance of AD while shortening the time needed to recover the maximum amount of biogas from AD. Keywords Lignocellulosic materials . Biogas . Biodegradability . Pretreatment . Cellulose . Hemicellulose . Lignin
Introduction The interest in producing and using renewable energy (solar, hydro, wind, biomass, and geothermal) is increasing throughout the world as a way to reduce greenhouse gas emission from fossil fuels [1, 2]. Hence, energy recovery from biomass has attracted global research interest. Lignocellulosic substrates are the most abundant biomass resource available and, therefore, are considered an ideal feedstock for the production of bioenergy and second-generation biofuels [3]. Besides producing biogas, which can offset the use of fossil fuel, AD is an excellent process for upcycling of wet organic waste, which today often ends in landfill or as a low-value compost [4].
* Birgitte K. Ahring [email protected] 1
Bioproducts, Sciences and Engineering Laboratory, Washington State University, Tri-cities, 2710 Crimson Way, Richland, WA 99354, USA
2
Biological Systems Engineering, Washington State University, Pullman, WA, USA
3
Voiland School of Chemical and Bioengineering, Pullman, WA, USA
AD has been exploited throughout the world and biogas can be used for electricity production or purified to natural gas quality and supplied to the natural gas grid. This utilization of biogas as an energy source is dependent on local factors ranging from infrastructural availability for CH4 delivery and distribution, availability of feedstock, collection and transportation of waste, skille
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