Assessment of the degradation efficiency of full-scale biogas plants: A comparative study of degradation indicators.

Increasing popularity and applications of the anaerobic digestion (AD) process has necessitated the development and identification of tools for obtaining reliable indicators of organic matter degradation rate and hence evaluate the process efficiency especially in full-scale, commercial biogas plants. In this study, four biogas plants (A1, A2, B and C) based on different feedstock, process configuration, scale and operational performance were selected and investigated. Results showed that the biochemical methane potential (BMP) based degradation rate could be use in incisively gauging process efficiency in lieu of the traditional degradation rate indicators.

Evaluating the influences of mixing strategies on the Biochemical Methane Potential test.

Mixing plays an important role in the Biochemical Methane Potential (BMP) test, but only limited efforts have been put into it. In this study, various mixing strategies were applied to evaluate the influences on the BMP test, i.e.

The effects of pre-aeration and inoculation on solid-state anaerobic digestion of rice straw.

Pre-aeration was investigated for enhancing biodegradation of recalcitrant lignocellulosic structure of rice straw under various low temperatures regimes (25, 35 and 45°C) and aeration durations (0, 2, 4, 6 and 8days). It was demonstrated aerated rice straw for 2days at 35°C resulted in highest hydrolytic efficiency and biochemical methane potential (BMP) (355.3±18.

Impacts of inoculum pre-treatments on enzyme activity and biochemical methane potential.

Biochemical methane potential (BMP) tests were carried out to investigate the influence of inoculum pre-treatments (filtration and pre-incubation) on methane production from cellulose and wheat straw. First-order model and Monod model were used to evaluate the kinetic constants of the BMP assays. The results demonstrated that fresh inoculum was the best option to perform BMP tests.

Production of raw starch-degrading enzyme by Aspergillus sp. and its use in conversion of inedible wild cassava flour to bioethanol.

The major bottlenecks in achieving competitive bioethanol fuel are the high cost of feedstock, energy and enzymes employed in pretreatment prior to fermentation. Lignocellulosic biomass has been proposed as an alternative feedstock, but because of its complexity, economic viability is yet to be realized. Therefore, research around non-conventional feedstocks and deployment of bioconversion approaches that downsize the cost of energy and enzymes is justified.

Effects of substrate concentration on methane potential and degradation kinetics in batch anaerobic digestion.

In this study, two experiments were conducted to evaluate the impact of substrate concentrations on methane potential and degradation kinetics of substrate. The biochemical methane potential (BMP) tests in Experiment I were performed at a constant inoculum to substrate ratio (ISR), whereas, different ISRs were applied in Experiment II. Results obtained from Experiment I revealed that methane potential of substrate increased at a saturating trend with higher substrate concentrations, and could differ by up to 30% between the lowest and highest investigated concentrations.

Cryogel-supported titanate nanotubes for waste treatment: Impact on methane production and bio-fertilizer quality.

By reducing the cadmium (Cd(2+)) content in biomass used for bio-based products such as biogas, a less toxic bio-based fertilizer can be obtained. In this work, we demonstrate how a macroporous polymer can support titanate nanotubes, and we take advantage of its known selective adsorption behavior towards Cd(2+) in an adsorption process from real nutrient-rich process water from hydrolysis of seaweed, a pollutant-rich biomass. We show that pretreatment steps involving alteration in area-to-volume ratio performed in aerated and acidic conditions release the most Cd(2+) from the solid material.

Determination of methane yield of cellulose using different experimental setups.

In this work, biochemical methane potential (BMP) tests with cellulose as a model substrate were performed with the aid of three manually operated or conventional experimental setups (based on manometer, water column and gas bag) and one automated apparatus specially designed for analysis of BMP. The methane yields were 340 ± 18, 354 ± 13, 345 ± 15 and 366 ± 5 ml CH4/g VS obtained from experimental setups with manometer, water column, gas bag, and automatic methane potential test system, which corresponded to a biodegradability of 82, 85, 83 and 88% respectively. The results demonstrated that the methane yields of cellulose obtained from conventional and automatic experimental setups were comparable; however, the methane yield obtained from the automated apparatus showed greater precision.

Impact of bioaugmentation on biochemical methane potential for wheat straw with addition of Clostridium cellulolyticum.

Hydrolysis is usually the rate-limited step for methane production from lignocellulosic substrate. Two bioaugmentation strategies, using the cellulolytic anaerobic bacteria Clostridium cellulolyticum, were adopted to enhance the hydrolysis of wheat straw with the purpose of improving the biochemical methane potential (BMP). Namely, the 24-h-incubated seed (C24S) with cellobiose as carbon source and the 60-h-incubated seed (WS60S) with wheat straw as carbon source were respectively used as the bioaugmentation agents.

Improved utilization of fish waste by anaerobic digestion following omega-3 fatty acids extraction.

Fish waste is a potentially valuable resource from which high-value products can be obtained. Anaerobic digestion of the original fish waste and the fish sludge remaining after enzymatic pre-treatment to extract fish oil and fish protein hydrolysate was evaluated regarding the potential for methane production. The results showed high biodegradability of both fish sludge and fish waste, giving specific methane yields of 742 and 828 m(3)CH(4)/tons VS added, respectively.

Stable operation during pilot-scale anaerobic digestion of nutrient-supplemented maize/sugar beet silage.

Biogas production from maize/sugar beet silage was studied under mesophilic conditions in a continuous stirred tank reactor pilot-scale process. While energy crop mono-digestion is often performed with very long hydraulic retention times (HRTs), the present study demonstrated an efficient process operating with a 50-day HRT and a corrected total solids (TS(corr)) based organic loading rate of 3.4 kg/m(3)d.

Ensiling of crops for biogas production: effects on methane yield and total solids determination.

Background: Ensiling is a common method of preserving energy crops for anaerobic digestion, and many scientific studies report that ensiling increases the methane yield. In this study, the ensiling process and the methane yields before and after ensiling were studied for four crop materials.

Results: The changes in wet weight and total solids (TS) during ensiling were small and the loss of energy negligible.

Benefits of supplementing an industrial waste anaerobic digester with energy crops for increased biogas production.

Currently, there is increasing competition for waste as feedstock for the growing number of biogas plants. This has led to fluctuation in feedstock supply and biogas plants being operated below maximum capacity. The feasibility of supplementing a protein/lipid-rich industrial waste (pig manure, slaughterhouse waste, food processing and poultry waste) mesophilic anaerobic digester with carbohydrate-rich energy crops (hemp, maize and triticale) was therefore studied in laboratory scale batch and continuous stirred tank reactors (CSTR) with a view to scale-up to a commercial biogas process.