While bioplastics are gaining wide interest in replacing conventional plastics, it is necessary to understand whether the treatment of the organic fraction of municipal solid waste (OFMSW) as an end-of-life option is compatible with their biodegradation and their possible role in shaping the microbial communities involved in the processes. In the present work, we assessed the microbiological impact of rigid polylactic acid (PLA) and starch-based bioplastics (SBB) spoons on the thermophilic anaerobic digestion and the aerobic composting of OFMSW under real plant conditions. In order to thoroughly evaluate the effect of PLA and SBB on the bacterial, archaeal, and fungal communities during the process, high-throughput sequencing (HTS) technology was carried out. The results suggest that bioplastics shape the communities’ structure, especially in the aerobic phase. Distinctive bacterial and fungal sequences were found for SBB compared to the positive control, which showed a more limited diversity. Mucor racemosus was especially abundant in composts from bioplastics’ treatment, whereas Penicillium roqueforti was found only in compost from PLA and Thermomyces lanuginosus in that from SBB. This work shed a light on the microbial communities involved in the OFMSW treatment with and without the presence of bioplastics, using a new approach to evaluate this end-of-life option.

Bioplastics may be collected in the bio-waste treatment, which is often composed of anaerobic digestion and subsequent aerobic composting of the digestates. The aim of this study was to evaluate the degradability of polylactic acid (PLA) and starch-based bioplastics (SBB) spoons under industrial conditions. Biomethane potential (BMP) was measured and biogas production was monitored, while the quality of composts was assessed by phytotoxicity and ecotoxicity tests. The bioplastics disintegration resulted in 65.1 +/- 4.6 % for PLA and <= 65.0 +/- 7.4 % for SBB, not achieving the target set by UNI EN 13,432 standard, and several residues were found in compost. Phytotoxicity tests on seeds reported the lowest Germination Index for PLA elutriate, whereas a potential negative effect of SBB on soil fauna was detected. Further investigation is needed to assess the fate of these ever-growing materials under industrial conditions, and also evaluate the effects of residues in compost.

Biogasdoneright™ is an innovative agricultural model aimed at achieving a sustainable agricultural intensification. The microfiltration of the by-product from biogas production, the digestate, is among technology innovations supporting the implementation of best practices in the Biogasdoneright™ system. Digestate microfiltration tests were carried out under different operating conditions, to fine tune the best working conditions of the equipment. Then it was possible to distribute the microfiltered digestate in fertigation on growing maize through drip lines without causing blockage. Microfiltered digestate to fertigation has proven to be a best practice to improve nutrients, water and energy efficiency in the context of Biogasdoneright™.

In this study, biogas and biomethane production during mesophilic anaerobic digestion of wheat substrates coming from national crops and naturally contaminated with deoxynivalenol (DON) and/or T-2/HT-2 toxins was investigated. Biochemical methane potential (BMP) tests of both wholewheat flour and of the main milling fractions were carried out to assess the effect on the concentration of mycotoxins on the anaerobic biological process and their residual presence in the final digestate. The good methane average production achieved (337.0 ± 24.5 NL CH4/kg VS) was substantially comparable with the yields gained from similar biomasses at mesophilic conditions. Moreover, an effective reduction (60.7–100%) of DON concentration was obtained in all the tested substrates (range of contamination in the samples, 368–12,916 μg/kg) whereas the sum of T-2 and HT-2 toxin levels in digestates was always <LOQ in all substrates analyzed (range of contamination in the samples, 5–65 μg/kg). The results supported an alternative exploitation of “non-compliant” lots of cereals destined for human consumption and/or animal feed which could represent a concrete benefit for agricultural producers. Anaerobic digestion could be employed as an effective tool to recover large amounts of trichothecene-contaminated cereals in an environmentally and economically sustainable way.

In this study, the possibility to manage maize contaminated with aflatoxins and fumonisins for the production of biogas was considered. This is a priority in the climate change scenario that is expected to increase the occurrence of aflatoxins in maize. The results clearly underline how the anaerobic digestion process used in biogas plants is able to reduce aflatoxin contamination, mainly when highly contaminated maize is used for feeding the biodigestors without affecting the efficiency of methane production. In particular, the higher aflatoxin contamination is, the higher is mycotoxin reduction during biodigestion, with reductions up to 95% in digestate. The co-occurring mycotoxins, fumonisins, were also reduced by around 15%. The vitality of mycotoxin producing fungi was also significantly reduced. Biogas production is therefore suggested as a good alternative use for uncompliant maize.

The implementation of hydrodynamic cavitation (HC) pretreatment for enhancing the methane potential from agricultural biomasses was evaluated in a full scale agricultural biogas plant, with molasses and corn meal as a supplementary energy source. HC batch tests were run to investigate the influence on methane production, particle size and viscosity of specific energy input. 470 kJ/kgTS was chosen for the full-scale implementation. Nearly 6-months of operational data showed that the HC pretreatment maximized the specific methane production of about 10%, allowing the biogas plant to get out of the fluctuating markets of supplementary energy sources and to reduce the methane emissions. HC influenced viscosity and particle size of digestate, contributing to reduce the energy demand for mixing, heating and pumping. In the light of the obtained results the HC process appears to be an attractive and energetically promising alternative to other pretreatments for the degradation of biomasses in biogas plant.

Trace metals play a very important role on the performance and stability of agricultural biogas digesters. The purpose of this study was to develop a methodological approach to quickly detect limiting conditions due to Trace Elements (TE) concentration in full-scale biogas plants. The work was based on long-term process monitoring in two full-scale agricultural biogas plants and on the correlation between their performance and TE concentration in the digesters. Monitoring and analysis of data from two different case studies allowed to understand the effect of the TE added on biogas plant performance. Furthermore, over-dosage has been avoided, minimizing the risk of biological inhibition and excess of heavy metal concentration in the effluent digestate according to regulation for land fertilization. TE supplementation has been successfully applied to optimize the biogas production, when a slight volatile organic acid accumulation has been detected (from about 3515 mg CH3COOHeq L-1 to 4530 mg CH3COOHeq L-1), and to recover the biogas production after a strong organic acid accumulation (up to 7779 mgCH(3)COOH(eq) L-1)(.) Molybdenum, nickel, cobalt, and selenium concentrations above the stimulatory level identified in this study showed similar effects in both case studies: a temporary increase of the methane content in the biogas by 15 - 20% and a provisional improvement of the specific methane production. This allowed to decrease the organic loading rate by 10 - 20%, due to rapid degradation of accumulated volatile organic acids. Further, the residual methane potential of the biogas plant in TE limiting conditions reached values up to 4.8% in comparison to the 1.3% residual methane potential achieved when TE concentration was not a limiting factor, proving that a proper use of IT could help in reducing greenhouse gases emission.

Volatile fatty acids (VFAs) are among the most important parameters in process monitoring of anaerobic digestion plants for biogas production. The concentration of single VFA species is typically determined by direct injection of the acidified aqueous phase of digestate samples into GC-FID. Analysis of dimethyl carbonate extracts was investigated as an alternative method consisting of a simple and rapid in-vial procedure of acidification and solvent extraction of the sample, followed by centrifugation and GC-MS analysis. The principal figures of merit resulting from internal standard calibration were comparable to those proposed for the direct analysis of aqueous digestate, while the analysis of real samples did not provide statistically significant differences between the two methods according to parametric and non-parametric tests. Procedural aspects including sample amount and solid removal improved with dimethyl carbonate, while GC contamination was reduced. The method was applied to seventeen samples from fully operating anaerobic digesters fed with various feedstocks and enabled the individuation of high probability of system stress through the values of total VFA, propanoic acid, longer chained VFA concentrations and the ratio between acetic and propanoic acid concentrations. The use of dimethyl carbonate allowed the detection of alicyclic and aromatic acids that could represent new molecular markers in assessing the origin of feed and process conditions.

The separate collection of recyclable waste in Italian municipalities (including biowaste, packaging waste, WEEEs and others) has reached a quota of 45.2% of all MSW managed in Italy in 2014 (29.66Mtons/yr), with a rather stable total production of waste (CIC, 2016). Anaerobic digestion (AD) is a feasible biological process to transform biowaste into biogas, a valuable biofuel. The biological process allows material to stabilize before composting, producing less gas emissions and odours, allows an energy and therefore economic value, thanks to the biogas produced.

In this study, eight different manure treatment plants were monitored. The plants were four on-farm and four centralized treatment plants, all of them at full-scale level. Assessment includes a total of seven pre-treatment and process units as follows: mechanical separation, with and without coagulant and flocculant addition, pasteurization, nitrification-denitrification, anaerobic digestion, and composting. The plants are located in nutrient surplus areas of three European Member States (Spain, Italy and Denmark), the majority of these areas being Nitrate Vulnerable Zones (NVZ). Results presented herein are data collected over a six-month period and comprise performance data of the treatment plants, pathogen indicators (E. coli and Salmonella) and greenhouse gas (GHG) emissions data under two scenarios: 1) the baseline scenario and 2) the treatment plant scenario. The assessment includes GHG emissions of the storage facilities, transportation, and subsequent intermediate storage, electric consumption, electric production, composting, and land application. All treatment plants studied generated a significant reduction in GHG emissions (between 53 and 90 %) in comparison to the baseline scenario. Organic matter and total solids (TS) content in manure were also greatly reduced, with values ranging between 35-53 % of chemical oxygen demand (COD) and, 24-61 % of TS for anaerobic digestion (AD) treatment plants, 77-93 % COD and 70 % TS in the case of AD combined with nitrogen (N)-removal unit plants. Nitrogen concentrations were also greatly reduced (between 65-85 %) total Kjeldahl nitrogen (TKN) and 68-83 % ammonium (NH4+-N)) in plants with N-removal units.

The gross value of the agricultural goods in 2014 amounted up to 370 billion Euros. Almost 50% of all agricultural production is provided by livestock farming.

CRPA Lab has conducted anaerobic digestion tests in the experimental continuous pilot plants, of two agro-industrial by-products, olive pomace and citrus pulp. They were co-digested in mixtures with cattle manure and maize silage. Four mixtures were tested; the process was conducted in mesophilic conditions. Olive pomace and citrus pulp represented from 35 to 50% of volatile solids fed daily in reactors ( corresponding to about 30% by weight). Results of the tests showed that all mixture generated biogas in significant quantities, of which 57-58% is methane; the mixtures with citrus pulp has provided the best performance. However, during the test, appropriate attention to the evolution of the main parameters for the monitoring process were required.

CRPA has identified, in Emilia Romagna Region, five agricultural biogas plants, to monitor the main parameters related to energy efficiency, operational reliability and have a realistic picture of the biogas yields. This work was part of the SEBE Project, co-financed by Central Europe Programme. The choice of plants, made by five different firms, was made on the basis of the type of biomasses fed, the size and the technology adopted. Four plants had an installed electrical power of less than 1 MW (size that allowed access to the all-inclusive feed-in tariff of 280 (sic)/MWhe injected into the grid) and one with an installed power of more than 1 MW (tariff system of green certificates). Substrates processed into the biogas plants were characterized, process parameters were detected, were characterized the digestate produced and monitored the specific production parameters such as the volumetric organic load, the hydraulic retention time, the electric energy produced and consumed in, the characteristics of the biogas, the biogas per m(3) of reactor, the biogas and methane yield per kg of organic substance introduced, the electrical yield per kg of organic matter introduced. Anaerobic digestion was confirmed as an energy conversion technology very versatile and it can use biomasses that other technologies can not used, such as vegetable and animal organic biomasses, raw products, with a total solids content with very different content of TS.

The anaerobic digestion process consists, as is known, in the first place in the degradation of the organic substance into simple compounds and subsequently in converting these into biogas. Each stage of the process is influenced by many chemical and physical parameters, as well as complex microbiological balance. Depending on organic matrices, loaded into the digesters, the process can be more or less fast, and this depends essentially on the complexity of the molecules constituting the organic matrix used: simple compounds such as organic acids and simple sugars degrade very rapidly, more compounds complex such as amino acids, lipids and fibrous fractions, require longer times. Degradation rate is one of the most important parameters in the dimensioning of the volume of the digester and / or in the choice of plant technologies. In general terms, the approach normally used to exploit the energy potential of biomass is to dimension the digesters in such a way as to ensure an hydraulic retention time sufficient for the bacteria to degrade the organic molecules: in case of pig manure, for example, digesters are sized with retention times of 20-25 days; in case of cattle manure, 35-40 days; in case of dedicated biomass, at least 50-70 days.

Two horizontal sub-surface flow constructed wetlands (h-SSF CW) were set-up and controlled to determine their efficiency in reducing the polluting load of wastewater from Parmigiano-Reggiano and Grana Padano cheese production. Besides, comparisons were made of biomass production and nutrient uptake of cattail (Typha latifolia) reaped at different stages. The average concentrations of the influent waters were about 250-320 mg/l TSS, 940-1060 mgO(2)/l COD, 600-700 mgO(2)/l BOD5, 35 mg/l TKN, 8-13 mg/l total P, 60-170 mg/l animal and vegetable fats and oils. The removal of COD, BOD5 and animal/vegetable fats and oils were above 95%, while resulted 60-65% for nitrogen and very different for phosphorus, varying from 75% in one CW to 20% in the other. Results demonstrated that h-SSF CW could help to solve the problem of the cost-effective disposal of cheese dairy wastewater, being a suitable treatment for reducing pollutants to values in conformance with Italian standards for discharge to a watercourse. Typha latifolia showed considerable biomass yield, though the N and P uptake was quite low if compared with nutrients inputs in CW (about 10%). There is the possibility to maximise biomass yield and nutrient uptake reaping cattail twice a year instead of only one time.