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Urease inhibitors are in general known as potential measure for reducing ammonia emissions in dairy and cattle housing systems. Due to the application of the urease inhibitor on the exercise areas within a housing system the inhibitor is “mixed” with cattle manure and this “mixture” remains unchanged during manure storage. In Germany, a large part of the total stored cattle manure is utilized as a substrate in biogas plants. Therefore, the aim of the current study was to test if different concentrations of urease inhibitor mixed with typical cattle slurry will have any (negative) effects on the biogas and methane yield. The Hohenheim Biogas Yield Test (HBT) was used to determine if the biogas and methane production of cattle manure is influenced by the admixture with urease inhibitor. Altogether, four urease inhibitor concentrations (0%, 0.1%, 1% und 10% of total Kjeldahl nitrogen) were tested in the HBT experiments with two different substrates, cattle manure and cellulose, as a reference, in repetitions each. The average biogas and methane production of cellulose was 740 L N /kg ODM and 403 L N /kg ODM and of cattle manure 471 L N /kg ODM and 295 L N /kg ODM. Both substrates treated with urease inhibitor showed no significant change in the biogas and methane production compared to the untreated ones. The use of urease inhibitors to reduce ammonia is harmless from the view of biogas plants. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to apply near-infrared spectroscopy (NIRS), available biogas plant data and lumped degradation kinetics to predict biogas production (BPr) of maize silage. A full-scale agricultural biogas plant was equipped with NIRS-metrology at the feeding station. Continuously NIR-spectra were collected for 520d. Substrate samples were analyzed by means of feedstuff analysis. Biogas potential of the samples was calculated from the laboratory analysis results and for a sample-subset practically assessed by “Hohenheim biogas tests”. NIRS-regression-models for all mentioned parameters were calibrated. Continuously gathered spectra, NIRS-models, actual plant-feeding data and degradation kinetics were used to calculate time-series of theoretically expectable BPr. Results were validated against measured gas quantity. Determination coefficients between calculated and measured BPr were up to 58.2%. This outcome was mainly due to the positive correlation between BPr and input amount since the substrate was very homogeneous. The use of NIRS seems more promising for plants with stronger substrate heterogeneity. [Copyright &y& Elsevier]

Highlights: [•] N-leaching risk evaluated after biogas residue application to maize and grass. [•] Biogas residue showed similar nitrate-leaching potential as animal slurry. [•] Methane hectare yield, but also nitrate-N loss, was higher for maize than grass. [•] Lower eco-efficiency of maize, i.e. higher nitrate-N loss per unit methane produced. [ABSTRACT FROM AUTHOR]

Abstract: The promotion of electricity generation from renewable energy sources has led to a substantial expansion of biogas production in Germany, with most biogas plants co-digesting slurry and crops, and maize being by far the most dominant substrate. At present only limited information is available on the agronomic and environmental performance of biogas cropping systems, and on the fertilizer value of biogas residues. In a two-year field experiment at two sites in northern Germany differing in soil quality, we analyzed the dry matter (DM) yield, N yield, methane yield, and the N balance of different cropping systems: (i) maize monoculture (R1), (ii) maize–whole crop wheat followed by Italian ryegrass as a double crop (R2), (iii) maize–grain wheat followed by mustard as a catch crop (R3), and (iv) perennial ryegrass ley (R4). Rotations R1, R2 and R3 were grown at Site 1 (sandy loam), whereas R1 and R4 were tested at Site 2 (humus sand). Crops were supplied with varying amounts (0–360kgNha−1, ryegrass: 0–480kgNha−1) of biogas residue, cattle slurry, pig slurry, or mineral N fertilizer, which allowed quantifying their N use efficiency in terms of apparent N recovery (ANR) and relative N fertilizer value (RNFV). No significant interactions of crop rotation and fertilizer type on DM and methane yield, plant N recovery, as well as N balance, were detected at Site 1, where R1 (19.3tDMha−1; 6750m3 N CH4 ha−1; N: norm conditions, i.e. 273K, 1024hPa) clearly out-yielded R2 (16.8tDMha−1; 5351m3 N CH4 ha−1) and R3 (12.8tDMha−1), while R2 had a higher plant N recovery. At Site 2, the perennial ryegrass ley achieved substantially lower maximum DM and methane yield (13.9tDMha−1; 4251m3 N CH4 ha−1) than maize monoculture (17.3tDMha−1; 6038m3 N CH4 ha−1). Fertilizer type affected grass performance: application of biogas residue resulted in lower yield and N recovery, but higher N balance than mineral fertilizer and cattle slurry. The N use efficiency of biogas residue application depended on the crop rotation. Biogas residue resulted in higher ANR and RNFV compared to pig slurry in R1, whilst in R2 the reverse occurred, and effects were similar to cattle slurry in R4. The results revealed that, except for grassland, substrate cropping based on biogas residues can exploit the yield potential without causing high N surplus. [Copyright &y& Elsevier]