Medium-chain carboxylates production from plant waste: kinetic study and effect of an enriched microbiome.

Background: The need for addition of external electron donors such as ethanol or lactate impairs the economic viability of chain elongation (CE) processes for the production of medium-chain carboxylates (MCC). However, using feedstocks with inherent electron donors such as silages of waste biomass can improve the economics. Moreover, the use of an appropriate inoculum is critical to the overall efficiency of the CE process, as the production of a desired MCC can significantly be influenced by the presence or absence of specific microorganisms and their metabolic interactions.

Material characterization and conditioning of cattle feedlot manure as feedstock for dry batch anaerobic digestion.

The focus of the study was to determine the suitability of cattle feedlot manure originating from clay-pack feedlots as a possible feedstock material for dry batch anaerobic digestion. Oedometer tests were carried out that measure the permeability and compressibility of the feedstock under practical conditions experienced in large-scale dry batch anaerobic digestion plants. Material characterization tests showed that feedlot manure was impermeable under compression and therefore unsuitable for percolation.

Exploring the combined effect of total ammonia nitrogen, pH and temperature on anaerobic digestion of chicken manure using response surface methodology and two kinetic models.

Ammonia inhibition is the most challenging issue in the anaerobic digestion (AD) of nitrogen-rich substrates. Total ammonia nitrogen (TAN) concentration, temperature and pH are the main operational parameters affecting the chemical equilibrium between free ammonium nitrogen (NH; FAN) and ammonium ions (NH). However, it is still unclear how these parameters together affect digestion performance by influencing this equilibrium.

Methane emissions from the storage of liquid dairy manure: Influences of season, temperature and storage duration.

Methane emissions from livestock manure are primary contributors to GHG emissions from agriculture and options for their mitigation must be found. This paper presents the results of a study on methane emissions from stored liquid dairy cow manure during summer and winter storage periods. Manure from the summer and winter season was stored under controlled conditions in barrels at ambient temperature to simulate manure storage conditions.

Ensiling excessively wilted maize stover with biogas slurry: Effects on storage performance and subsequent biogas potential.

This study evaluated the ensiling performance of excessively wilted maize stover (EWMS) with biogas slurries and the effect on the subsequent biomethane potential. Chicken and pig manure biogas slurries with or without solid-liquid separation were used to amend the stover humidity before ensiling for 60 d. The hetero-lactic-acid fermentative bacteria Atopostipes and Lactobacillus were enriched by the biogas slurry regardless of the solid-liquid separation.

Synergetic effect of combined ensiling of freshly harvested and excessively wilted maize stover for efficient biogas production.

This study investigated the synergetic effects of ensiling freshly harvested maize stover (FHM) and excessively wilted maize stover (EWM) on biogas production. FHM and EWM were mixed in various proportions to obtain dry matter (DM) contents of 30%, 35% and 40%. For reference, FHM alone was ensiled and stored in open-air.

Biomass potential analysis of aquatic biomass and challenges for its use as a nonconventional substrate in anaerobic digestion plants.

Aquatic macrophytes are important components of aquatic habitats. However, the overgrowth of aquatic plants can cause severe problems for the management of bodies of water. As a result, these plants must be removed and disposed of as waste.

The startup performance and microbial distribution of an anaerobic baffled reactor (ABR) treating medium-strength synthetic industrial wastewater.

In this study, an anaerobic baffled reactor (ABR) with seven chambers was applied to treat medium-strength synthetic industrial wastewater (MSIW). The performance of startup and shock test on treating MSIW was investigated. During the acclimation process, the chemical oxygen demand (COD) of MSIW gradually increased from 0 to 2,000 mg L, and the COD removal finally reached 90%.

Optimization of semi-continuous anaerobic digestion of sugarcane straw co-digested with filter cake: Effects of macronutrients supplementation on conversion kinetics.

Anaerobic digestion of sugarcane straw co-digested with sugarcane filter cake was investigated with a special focus on macronutrients supplementation for an optimized conversion process. Experimental data from batch tests and a semi-continuous experiment operated in different supplementation phases were used for modeling the conversion kinetics based on continuous stirred-tank reactors. The semi-continuous experiment showed an overall decrease in the performance along the inoculum washout from the reactors.

Effect of particle size reduction and ensiling fermentation on biogas formation and silage quality of wheat straw.

The effect of ensiling fermentation and mechanical pretreatment on the methane yield of lignocellulosic biomass was investigated in order to determine the optimum pretreatment conditions for biogas production. Wheat straw was treated using the following techniques: mechanical disintegration by chopping and extruder-grinding to particle sizes of 2.0 and 0.

Enhancing biogas production from vinasse in sugarcane biorefineries: Effects of urea and trace elements supplementation on process performance and stability.

In this study, the effects of nitrogen, phosphate and trace elements supplementation were investigated in a semi-continuously operated upflow anaerobic sludge blanket system to enhance process stability and biogas production from sugarcane vinasse. Phosphate in form of KH2PO4 induced volatile fatty acids accumulation possibly due to potassium inhibition of the methanogenesis. Although nitrogen in form of urea increased the reactor's alkalinity, the process was overloaded with an organic loading rate of 6.

Comparison of start-up strategies and process performance during semi-continuous anaerobic digestion of sugarcane filter cake co-digested with bagasse.

The anaerobic digestion of sugarcane filter cake and the option of co-digestion with bagasse were investigated in a semi-continuous feeding regime to assess the main parameters used for large-scale process designing. Moreover, fresh cattle manure was considered as alternative inoculum for the start-up of biogas reactors in cases where digestate from a biogas plant would not be available in remote rural areas. Experiments were carried out in 6 lab-scale semi-continuous stirred-tank reactors at mesophilic conditions (38±1°C) while the main anaerobic digestion process parameters monitored.

Biogas Production from Sugarcane Waste: Assessment on Kinetic Challenges for Process Designing.

Biogas production from sugarcane waste has large potential for energy generation, however, to enable the optimization of the anaerobic digestion (AD) process each substrate characteristic should be carefully evaluated. In this study, the kinetic challenges for biogas production from different types of sugarcane waste were assessed. Samples of vinasse, filter cake, bagasse, and straw were analyzed in terms of total and volatile solids, chemical oxygen demand, macronutrients, trace elements, and nutritional value.

Optimization of hydrolysis and volatile fatty acids production from sugarcane filter cake: Effects of urea supplementation and sodium hydroxide pretreatment.

Different methods for optimization the anaerobic digestion (AD) of sugarcane filter cake (FC) with a special focus on volatile fatty acids (VFA) production were studied. Sodium hydroxide (NaOH) pretreatment at different concentrations was investigated in batch experiments and the cumulative methane yields fitted to a dual-pool two-step model to provide an initial assessment on AD. The effects of nitrogen supplementation in form of urea and NaOH pretreatment for improved VFA production were evaluated in a semi-continuously operated reactor as well.