Search Results (5)

Anaerobic digesters fed with dairy cow slurry struggle to achieve economic viability, particularly when animals are housed seasonally, so additional feedstocks are usually required. This study applied experimentally derived data from the co-digestion of cow slurry (CS) and food waste (FW) to the UK dairy herd as a whole, and at average (AH) and large (LH) herd sizes of 160 and 770 animals, respectively. The experimental data confirmed stable operation at an organic loading rate (OLR) of 5 g VS L⁻¹ day⁻¹ at CS:FW ratios of 3:1 and 6:1 on a wet weight basis, and these parameters were considered for both AH and LH by herd size and country (Scotland, England, Wales, Northern Ireland) in order to provide energy production and policy observations. The results showed that these scenarios could provide between 959 to 23,867 GJ per year, and that a targeted policy intervention could affect slurry treatment from a significant number of animals in a relatively small number of large herds across the UK. For a more detailed analysis, better data are required on non-domestic FW arisings and FW transportation needs. Full article

Livestock digestate provides nutrients and organic matter to the soil while increasing agricultural sustainability. Nevertheless, nitrogen (N) losses due to the nutrient surplus in regions characterized by intensive animal farming activities still represent an unsolved issue. For this purpose, digestate needs proper treatment and management to avoid N losses in the environment. In the livestock farming context, anaerobic digestion (AD) can be accompanied by an ammonia stripping (AS) process for N recovery. This paper aims to investigate the feasibility AS prior to and after AD of the manure, focusing on two different livestock farms, representative of dairy cattle and pig breeding in southern Italy. AS was performed at a lab scale by injecting microbubbles of air, which allowed the pH to increase, and thus the removal of ammonia. The results show that treating a dairy raw slurry with high intermediate alkalinity (IA) (6707 mg CaCO₃ L⁻¹) with AS may not be convenient in terms of total ammonia nitrogen (TAN) reduction. As a matter of fact, the loss of buffering capacity during the stripping process resulted in a pH never exceeding the value of 9, which could not promote free ammonia volatilization, whereas integrating AD with AS allowed us to obtain a 34% higher TAN reduction under the same stripping conditions at a temperature (T) of 38 °C and a gas-to-liquid ratio (G/L) of 1:1. Therefore, the AS removal efficiency strongly depends on the characteristics (mainly IA) of the treated matrix. High IA values suggest a possible high concentration of volatile fatty acids, which hinders pH increases and, thus, enables ammonia stripping. Despite the initial matrix origin, a low IA compared to the total alkalinity (TA) (<20% of TA) ensures a greater ammonia removal efficiency, which could be similar between digestate and raw manure in the same operative process conditions. Nonetheless, the amount of ammonia stripped is related to the initial TAN concentration of the specific matrix. Full article

Mono anaerobic digestion (AD) of dairy cow manure (DCM) is constrained by high moisture, ash and crude fibre content. Anaerobic co-digestion DCM and other biomass is one of the methods to overcome this drawback. This study aimed to evaluate: methane production from different parts of Pistia stratiotes (PS), methane production from the mixed substrate of PS and DCM in different proportions of PS in terms of volatile solids (VS) (0%, 7.99%, 14.91%, and 20.94%) using continuous digesters, and the potency of biogas yield from the digested slurry. Methane production from the whole plant, shoot system, and root of PS was 405.68, 416.82, and 326.42 L/kg VS, respectively. The highest methane production was obtained from the shoot system because that part contained higher crude protein and hemicellulose contents. Utilization of PS as a co-substrate for AD of the DCM can increase methane production by 28.65–56.98% compared to the control digester. No effect on pH, total ammonia nitrogen and total volatile fatty acid indicated that PS was suitable as a co-substrate of DCM and can significantly increase methane yield of the mixed substrate. AD of digested slurries showed that to recover the biogas production from the mixed substrate, the post-digestion treatment should be applied before the slurries are used as organic fertilizer. Full article

This study was designed to assess the suppressive effects of various anaerobically digested slurries (ADSs), and the microorganisms inhabiting them, against Fusarium wilt in spinach. We used five different ADSs from a range of source materials (dairy cow manure, sewage sludge, food garbage, pig manure, night soil sludge), combined in different proportions. All five raw ADSs suppressed the growth of Fusarium oxysporum f. sp. spinaciae (Fos) on agar plates using a co-culture test. In contrast, filtrate ADSs did not suppress the growth of Fos. In total, 32 bacterial strains were isolated from five ADSs, and eight isolates showed antagonistic activities against Fos. Based on 16S rDNA sequences, the strain AD-3 isolated from ADS from dairy cow manure belonged to Bacillus velezensis. Genome analysis revealed that AD-3 had two kinds of genes related to the production of the non-ribosomal lipopeptides, fengycin/plipastatin (pps genes), and surfactin (srf genes). In pot assays, inoculation of AD-3 (1.0 × 10⁶ CFU·g⁻¹ dry soil) into Fos-infected soil (1.0 × 10⁵ bud-cells·g⁻¹ dry soil) significantly reduced the severity of Fusarium wilt disease at 28 d after seedling. The percentage reductions in disease severity in two replicates were 64.3% and 44.3%, respectively. Thus, bacterial strain AD-3 could be applied to reduce Fusarium wilt in spinach. Full article

This paper presents the results of an interdisciplinary study aimed at assessing the possibility of using duckweed to purify and recover nutrients from the effluent remaining after struvite precipitation and ammonia stripping from a liquid fraction of anaerobic digestate in a biorefinery located at a Dutch dairy cattle production farm. The nutritional value of duckweed obtained in a biorefinery was assessed as well. Duckweed (Lemna minuta) was cultured on a growth medium with various concentrations of effluent from a biorefinery (EFL) and digested slurry (DS) not subjected to the nutrient recovery process. The study’s results showed that duckweed culture on the media with high contents of DS or EFL was impossible because they both inhibited its growth. After 15 days of culture, the highest duckweed yield was obtained from the ponds with DS or EFL contents in the medium reaching 0.39% (37.8 g fresh matter (FM) and 16.8 g FM per 8500 mL of the growth medium, respectively). The recovery of N by duckweed was approximately 75% and 81%, whereas that of P was approximately 45% and 55% of the growth media with EFL_0.39% and DS_0.39%, respectively. Duckweed obtained from the biorefinery proved to be a valuable high-protein feedstuff with high contents of α-tocopherol and carotenoids. With a protein content in duckweed approximating 35.4–36.1%, it is possible to obtain 2–4 t of protein per 1 ha from EFL_0.39% and DS_0.39% ponds, respectively. Full article