Developing a biogas centralised circular bioeconomy using agricultural residues - Challenges and opportunities.

Anaerobic digestion (AD) can be used as a stand-alone process or integrated as part of a larger biorefining process to produce biofuels, biochemicals and fertiliser, and has the potential to play a central role in the emerging circular bioeconomy (CBE). Agricultural residues, such as animal slurry, straw, and grass silage, represent an important resource and have a huge potential to boost biogas and methane yields. Under the CBE concept, there is a need to assess the long-term impact and investigate the potential accumulation of specific unwanted substances.

Effect of different feeding management on the respiratory methane emission and feces-derived methane yield of goat.

Objective: This study aimed to evaluate the respiratory methane emission and ultimate methane yield ( ) of goat feces that fed roughage consisted of and ) and fed roughage and concentrate with different protein source in the ration (fish meal and soybean meal).

Materials And Methods: Fifteen Kacang bucks were allocated to the control group (T0): goats were fed roughage only, T1: goats were fed roughage and concentrate with fish meal as protein sources, and T2: goats were fed roughage and concentrate and the protein source in the ration was soybean meal.

Results: The protein content of feces from T0 was significantly lower ( < 0.

Methane emission during on-site pre-storage of animal manure prior to anaerobic digestion at biogas plant: Effect of storage temperature and addition of food waste.

This study investigated the temperature dependency of CH emission from pre-storage of animal manure prior to anaerobic digestion at 15, 20, 25 and 30 °C using lab-scale anaerobic digesters. The manure was added and removed daily to simulate the pre-storage process at biogas plants. CH emission accounted for 1-46% of total CH potential from pig manure (PM) and 1-2% of that from cattle manure (CM) at the investigated temperatures, with significant increases above 25 °C.

Influence on anaerobic digestion by intermediate thermal hydrolysis of waste activated sludge and co-digested wheat straw.

This paper analyses time (30 and 60 min) and temperature (120-190 °C) effects of intermediate thermal hydrolysis (ITHP) in a two-step anaerobic digestion of waste activated sludge (WAS) with and without wheat straw as a co-substrate. Effects were analyzed by measuring biochemical methane potential for 60 days and assessing associated kinetic and chemical data. Compared to non-treatment, ITHP increased the secondary step methane yield from 52 to 222 L CH kg VS and from 147 to 224 L CH kg VS for pre-digested WAS and pre-co-digested WAS respectively at an optimum of 170 °C and 30 min.

Exogenous addition of H for an in situ biogas upgrading through biological reduction of carbon dioxide into methane.

Biological reduction of CO into CH by exogenous addition of H is a promising technology for upgrading biogas into higher CH content. The aim of this work was to study the feasibility of exogenous H addition for an in situ biogas upgrading through biological conversion of the biogas CO into CH Moreover, this study employed systematic study with isotope analysis for providing comprehensive evidence on the underlying pathways of CH production and upstream processes. Batch reactors were inoculated with digestate originating from a full-scale biogas plant and fed once with maize leaf substrate.

Identification of syntrophic acetate-oxidizing bacteria in anaerobic digesters by combined protein-based stable isotope probing and metagenomics.

Inhibition of anaerobic digestion through accumulation of volatile fatty acids occasionally occurs as the result of unbalanced growth between acidogenic bacteria and methanogens. A fast recovery is a prerequisite for establishing an economical production of biogas. However, very little is known about the microorganisms facilitating this recovery.

Biogas potential from forbs and grass-clover mixture with the application of near infrared spectroscopy.

This study investigated the potentials of forbs; caraway, chicory, red clover and ribwort plantain as substrates for biogas production. One-, two- and four-cut systems were implemented and the influence on dry matter yields, chemical compositions and methane yields were examined. The two- and four-cut systems resulted in higher dry matter yields (kg [total solid, TS] ha(-1)) compared to the one-cut system.

The effect of mixed-enzyme addition in anaerobic digestion on methane yield of dairy cattle manure.

This study investigates the effect of applying a mixture of enzymes (ME) to dairy cattle manure (DCM) as substrate in anaerobic digestion (AD). The aims of this study were to evaluate different methods of ME application to DCM at different temperatures and to investigate the effect of adding ME during the pre-treatment of the solid fractions of dairy cattle manure (SFDCM). The results showed that there was no positive effect of direct ME addition to substrate at either mesophilic (35 degrees C) or thermophilic (50 degrees C) process temperatures, but there was a significant 4.

Quantifying contribution of synthrophic acetate oxidation to methane production in thermophilic anaerobic reactors by membrane inlet mass spectrometry.

A unique method was developed and applied for monitoring methanogenesis pathways based on isotope labeled substrates combined with online membrane inlet quadrupole mass spectrometry (MIMS). In our study, a fermentation sample from a full-scale biogas plant fed with pig and cattle manure, maize silage, and deep litter was incubated with 100 mM of [2-(13)C] sodium acetate under thermophilic anaerobic conditions. MIMS was used to measure the isotopic distribution of dissolved CO2 and CH4 during the degradation of acetate, while excluding interference from water by applying a cold trap.

Effects of high-temperature isochoric pre-treatment on the methane yields of cattle, pig and chicken manure.

Cattle manure, dewatered pig manure and chicken manure were pre-treated in a high-temperature reactor under isochoric conditions for 15 min at temperatures between 100 and 225 degrees C with 25 degrees C intervals to study the effect on their methane yield. After 27 days of batch incubation, cattle manure showed a significant improvement in its biochemical methane potential (BMP) of 13% at 175 degrees C and 21% at 200 degrees C. Pig manure showed improvements at temperatures of 125 degrees C and above, with a maximum 29% increase in yield at 200 degrees C.

Anaerobic digestion of acidified slurry fractions derived from different solid-liquid separation methods.

Batch assays investigating the ultimate methane yields (B(0)) of acidified slurry fractions produced with different solid-liquid slurry separation techniques were done. The result showed that the anaerobic digestion (AD) process was inhibited when raw and liquid fractions of sow, pig and dairy cow acidified slurry are digested, but AD treating solid fractions (SF) acidified slurry showed no sulphide inhibition. The B(0) of SF acidified sow slurry increased significantly with increasing screen size in the screw press.

Thermophilic anaerobic co-digestion of separated solids from acidified dairy cow manure.

This study examined the potential for partly substituting dairy cow manure (DCM) with solids from solid to liquid separation of acidified dairy cow manure (SFDCM) during thermophilic anaerobic digestion. Three different substituting levels with a maximum of 30% substitution were tested. All digesters substituting DCM with SFDCM showed a stable biogas production with low volatile fatty acid concentrations after a short transition period.

NIR monitoring of ammonia in anaerobic digesters using a diffuse reflectance probe.

The feasibility of using a diffuse reflectance probe attached to a near infrared spectrometer to monitor the total ammonia nitrogen (TAN) content in an anaerobic digester run on cattle manure was investigated; as a previous study has indicated that this probe can be easily attached to an anaerobic digester. Multivariate modelling techniques such as partial least squares regression and interval partial least squares methods were used to build models. Various data pre-treatments were applied to improve the models.

Comparison of near infra-red spectroscopy, neutral detergent fibre assay and in-vitro organic matter digestibility assay for rapid determination of the biochemical methane potential of meadow grasses.

This paper investigates near infra-red spectroscopy (NIRS) as an indirect and rapid method to assess the biochemical methane potential (BMP) of meadow grasses. Additionally analytical methods usually associated with forage analysis, namely, the neutral detergent fibre assay (NDF), and the in-vitro organic matter digestibility assay (IVOMD), were also tested on the meadow grass samples and the applicability of the models in predicting the BMP was studied. Based on these, regression models were obtained using the partial least squares (PLS) method.

Real time monitoring of a biogas digester with gas chromatography, near-infrared spectroscopy, and membrane-inlet mass spectrometry.

Four methods of monitoring the anaerobic digestion process were studied at pilot scale. The methods employed were Micro Gas Chromatography (μ-GC) and Membrane Inlet Mass Spectrometry (MIMS) for measurements in the gas phase, Near Infrared Spectroscopy (NIRS) and pH in the liquid phase. Micro Gas Chromatography accurately measured H(2), CH(4), H(2)S, N(2) and O(2) in the headspace whereas the MIMS accurately measured CH(4), CO(2), H(2)S, reduced organic sulfur compounds and p-cresol, also in the headspace.

Evaluation of near infrared spectroscopy and software sensor methods for determination of total alkalinity in anaerobic digesters.

In this study two approaches to predict the total alkalinity (expressed as mg L(-1)HCO(3)(-)) of an anaerobic digester are examined: firstly, software sensors based on multiple linear regression algorithms using data from pH, redox potential and electrical conductivity and secondly, near infrared reflectance spectroscopy (NIRS). Of the software sensors, the model using data from all three probes but a smaller dataset using total alkalinity values below 6000 mg L(-1)HCO(3)(-) produced the best calibration model (R(2)=0.76 and root mean square error of prediction (RMSEP) of 969 mg L(-1)HCO(3)(-)).

A novel acoustic sensor approach to classify seeds based on sound absorption spectra.

A non-destructive and novel in situ acoustic sensor approach based on the sound absorption spectra was developed for identifying and classifying different seed types. The absorption coefficient spectra were determined by using the impedance tube measurement method. Subsequently, a multivariate statistical analysis, i.

Optimisation of the anaerobic digestion of agricultural resources.

It is in the interest of operators of anaerobic digestion plants to maximise methane production whilst concomitantly reducing the chemical oxygen demand of the digested material. Although the production of biogas through anaerobic digestion is not a new idea, commercial anaerobic digestion processes are often operated at well below their optimal performance due to a variety of factors. This paper reviews current optimisation techniques associated with anaerobic digestion and suggests possible areas where improvements could be made, including the basic design considerations of a single or multi-stage reactor configuration, the type, power and duration of the mixing regime and the retention of active microbial biomass within the reactor.