On the Effect of Aqueous Ammonia Soaking Pre-Treatment on Continuous Anaerobic Digestion of Digested Swine Manure Fibers

(1) Background: The continuously increasing demand for renewable energy sources renders anaerobic digestion as one of the most promising technologies for renewable energy production. Due to the animal production intensification, manure is being used as the primary feedstock for most biogas plants. Their economical profitable operation, however, relies on increasing the methane yield from the solid fraction of manure, which is not so easily degradable. The solid fraction after anaerobic digestion, the so-called digested fibers, consists mainly of hardly biodegradable material and comes at a lower mass per unit volume of manure compared to the solid fraction before anaerobic digestion. Therefore, investigation on how to increase the biodegradability of digested fibers is very relevant. So far, Aqueous Ammonia Soaking (AAS), has been successfully applied on digested fibers separated from the effluent of a manure-fed, full-scale anaerobic digester to enhance their methane productivity in batch experiments. (2) Methods: In the present study, continuous experiments at a mesophilic (38 °C) CSTR-type anaerobic digester fed with swine manure first and a mixture of manure with AAS-treated digested fibers in the sequel, were performed. Anaerobic Digestion Model 1 (ADM1) previously fitted on manure fed digester was used in order to assess the effect of the addition of AAS-pre-treated digested manure fibers on the kinetics of anaerobic digestion process. (3) Results and Conclusions: The methane yield of AAS-treated digested fibers under continuous operation was 49–68% higher than that calculated in batch experiments in the past. It was found that AAS treatment had a profound effect mainly on the disintegration/hydrolysis rate of particulate carbohydrates. Comparison of the data obtained in the present study with the data obtained with AAS-pre-treated raw manure fibers in the past revealed that hydrolysis kinetics after AAS pre-treatment were similar for both types of biomasses

Efficient Technology for the Pretreatment of Biomass II

Biomass can be used as feedstock for the production of biomaterials, chemicals, platform molecules and biofuels. It is the most reliable alternative to reduce fossil fuel consumption and greenhouse gas emissions. Within the framework of the circular economy, resource recovery from organic waste, including sewage sludge, biowaste, manure and slaughterhouse waste, is particularly useful, as it helps saving resources while reducing environmental pollution. In contrast to energy crops, lignocellulosic biomass and algae do not compete for food production; therefore, they represent an important source of biomass for bioenergy and bioproducts. However, biomass may require a pretreatment step in order to enhance its conversion into valuable products in terms of process yield and/or productivity. Furthermore, a pretreatment step may be mandatory for waste management (i.e., animal by-products).Pretreatment technologies are applied upstream of various conversion processes of biomass into biofuels or biomaterials, including bioethanol, biohydrogen, biomethane, biomolecules or bioproducts. Pretreatments may include mechanical, thermal, chemical and biological techniques, which represent a crucial, cost-intensive step for the development of biorefineries. Thus, research is needed to help identify the most effective, economic, and environmentally friendly pretreatment options for each feedstock. This Special Issue aims to gather recent developments of biomass pretreatments for bioproduct and biofuel production