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Assessing archeal indicators of performance by RT-qPCR methods during anaerobic co-digestion of organic wastes.

Questions: Can shrubs (Cytisus multiflorus) and large herbivore exclusion (fence) facilitate seedling survival and growth of marcescent and sclerophyllous oaks (Quercus pyrenaica vs Q. ilex subsp. ballota) under a bioclimatic limit in Mediterranean grazed areas?Location: Open oak woodlands, central-western Spain. Methods:A 2-yr field experiment was conducted by planting 200 seedlings of each Quercus species under four different treatments combining the influence of nurse shrubs and fencing on Quercus seedling survival and growth.Results: Cytisus multiflorus enhanced poor Quercus seedling survival found in the study area, at least during the first 2 yr after planting and particularly during the first dry season. The improvement in soil organic matter under the shrub canopy may have contributed to this positive effect, which was more pronounced on Q. pyrenaica seedlings. Seedling herbivory did not seem to be a limitation to survival. Increased seedling growth in both species was also very low, and no growth was recorded 2 yr after planting without shrubs. The positive shrub effect on seedling growth, especially marked in fenced areas, was more important in Q. pyrenaica in the first growing period and in Q. ilex in the second; 2 yr after planting no difference in shrub effect on growth was found in either Quercus species. Seedling herbivory was a limitation to seedling growth in areas without shrubs, mainly in the case of Q. pyrenaica. Conclusions:In Mediterranean grazed areas with important summer drought and very sandy soil, shrubby C. multiflorus plants have a clear facilitative effect on seedlings of ecologically contrasted Quercus species. The facilitative effect was found in both marcescent and sclerophyllous oak seedlings, but to a different degree depending on the species considered and the variable measured (survival or growth). In terms of survival, the marcescent species was more favoured by shrub cover than the sclerophyllous one, and this effect was accentuated through time. However, in terms of growth, although Q. pyrenaica was initially more favoured by shrubs, differences between the two species were attenuated after 2 yr. Therefore, C. multiflorus can have a key role in restoration of these oak degraded environments.

Methanogen populations and their domains are poorly understood; however, in recent years, research on this topic has emerged. The relevance of this field has also been enhanced by the growing economic interest in methanogen skills, particularly the production of methane from organic substrates. Management attention turned to anaerobic wastes digestion because the volume and environmental impact reductions. Methanogenesis is the biochemically limiting step of the process and the industrially interesting phase because it connects to the amount of biogas production. For this reason, several studies have evaluated the structure of methanogen communities during this process. Currently, it is clear that the methanogen load and diversity depend on the feeding characteristics and the process conditions, but not much data is available. In this study, we apply a Real-Time Polymerase Chain Reaction (RT-PCR) method based on mcrA target to evaluate, by specific probes, some subgroups of methanogens during the mesophilic anaerobic digestion process fed wastewater sludge and organic fraction of the municipal solid waste with two different pre-treatments. The obtained data showed the prevalence of Methanomicrobiales and significantly positive correlation between Methanosarcina and Methanosaetae and the biogas production rate (0.744 p < 0.01 and 0.641 p < 0.05). Methanosarcina detected levels are different during the process after the two pre-treatment of the input materials (T-test p < 0.05). Moreover, a role as diagnostic tool could be suggested in digestion optimisation.

Environmental advances due to the integration of food industries and anaerobic digestion for biogas production: the perspectives in the Italian milk and dairy product branch.