The correct management of livestock manure represents one of the major challenge for the agricultural sector development, as it may ensure environmental and economic sustainability of livestock ...farming. In this work, a new treatment process called N-Free®, was monitored on two plants treating digested cattle manure (DCM) and digested swine manure (DSM). The process is characterized by sequential integration of solid/liquid separations, ultrafiltration, reverse osmosis and cold ammonia stripping. Solid and liquid streams were characterized regarding TS, TKN, N–NH4+, P and K content allowing to draw a complete mass balance. The main results were a substantial reduction of initial digestate volume (38 and 51% in DCM and DSM respectively) as clean water and a high N–NH4+ removal percentage (47 and 71% in DCM and DSM respectively), through cold ammonia stripping, allowing the production of up to 1.8 m3 concentrated ammonium sulfate, every 100 m3 of treated digestate. The concentrated streams, rich in either organic or mineral N, P and K, can be efficiently used for land application. The N-Free® technology demonstrated to be a valuable candidate for the path toward nutrient and water recycle, in a new sustainable agriculture and farming concept.
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•A new process for digestate treatment to recover N and reduce volume is proposed.•The process was studied and complete mass balance performed.•A maximum reduction of 45% of TKN and of 51% of volume was achieved on digested pig slurry.•Process efficiency seems to be correlated with TS content and N–NH4+/TKN ratio.
•Two-stage anaerobic digestion should be more productive than traditional process.•Energy recoveries (H2+CH4vs CH4) were compared through a new method.•Four different substrates at nine different ...experimental conditions were tested.•Two-stage recovered 8%–43% more energy than one-stage and never significantly less.•Deeper research should be addressed to prove the convenience of two-stage approach.
The supremacy of two-stage on traditional one-stage anaerobic digestion (AD), in terms of overall energy recovery (ER) from biomass has often been proved. However, the process conditions ensuring this result, as well as the reasons for higher efficiency, have always been unclear. In this work, a new standardized approach is proposed: optimization at lab-scale of both hydrogen and methane generation processes allowed comparing the maximum potential ER of both two-stage (as H2+CH4) and one-stage AD (as CH4). Relatively high bio-hydrogen yields were obtained testing four different organic substrates (ER of 1–1.6MJkg−1VS-added). Biomethane generation resulted in ER in the range of 9–19MJkg−1VS-added., similarly for two-stage and one-stage systems. The overall ER resulted in significantly higher (8%–43%) for the two-stage in the large majority of experimental conditions and never significantly lower. These preliminary results should drive further research to better understand the conditions that can drive the two-stage AD to higher performance.
Anaerobic digestion produces a biologically stable and high-value fertilizer product, the digestate, which can be used as an alternative to mineral fertilizers on crops. However, misuse of digestate ...can lead to annoyance for the public (odours) and to environmental problems such as nitrate leaching and ammonia emissions into the air. Full field experimental data are needed to support the use of digestate in agriculture, promoting its correct management. In this work, short-term experiments were performed to substitute mineral N fertilizers (urea) with digestate and products derived from it to the crop silage maize. Digestate and the liquid fraction of digestate were applied to soil at pre-sowing and as topdressing fertilizers in comparison with urea, both by surface application and subsurface injection during the cropping seasons 2012 and 2013. After each fertilizer application, both odours and ammonia emissions were measured, giving data about digestate and derived products' impacts.
The AD products could substitute for urea without reducing crop yields, apart from the surface application of AD-derived fertilizers. Digestate and derived products, because of high biological stability acquired during the AD, had greatly reduced olfactometry impact, above all when they were injected into soils (82–88% less odours than the untreated biomass, i.e. cattle slurry). Ammonia emission data indicated, as expected, that the correct use of digestate and derived products required their injection into the soil avoiding, ammonia volatilization into the air and preserving fertilizer value. Sub-surface injection allowed ammonia emissions to be reduced by 69% and 77% compared with surface application during the 2012 and 2013 campaigns.
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•Anaerobic digestion produced useful fertilizers, i.e. the digestate.•Digestate misuses led to odours and ammonia impacts.•Pre-sowing and topdressing use of digestate substituted completely N-fertilizers.•Subsurface injection of digestate reduced greatly odour and NH3 emissions.•Digestate use allowed producing maize silage as well as using urea.
► We aimed to describe the effect of lignin S/G ratio of eucalyptus on wood saccharification. ► S/G ratio modify 3D cell wall structure and so cellulose availability to enzymatic attack. ► Cellulose, ...hemicelluloses and lignin formed a sheath protecting cellulose from the enzymatic attack. ► Ionic liquid were used to destroy 3D structure to improve cellulose availability.
There are several approaches being investigated to improve the efficiency of biomass conversion into fermentable sugars, including those that engineer the feedstocks to enhance digestibility. In this study it was evaluated the impact of genotype modifications of three mutants of Eucalyptus globulus L., and of the corresponding wild type on cellulose hydrolyzability before and after ionic liquid (IL) pretreatment. Both untreated and IL-treated samples were chemically characterized and tested for cellulose hydrolizability. Results obtained indicate that genetic modifications altered wood lignin-S/G ratio. This alteration resulted in a different hydrolyzability of cellulose for untreated samples, i.e. high lignin-S/G ratio produced low glucose yield (r=−0.97; P<0.03; n=4), but did not affect glucose yield after IL pretreatment. IL pretreated samples had increased glucose yields compared to that of untreated samples due to the modification of microcrystalline cellulose I to mixtures of more hydrolysable cellulose II and amorphous cellulose, and to the partial removal of the steric impediment, or removal of the lignin “sheath” protecting cellulose, to enzymes. The efficiency of the IL pretreatment used in this study does not appear to be affected by the S/G content of the E. globulus.
► Biodrying process reduces waste water content increasing net heating value. ► Biodried waste can be used to produce SRF to be burned in incinerator. ► Low water content of the biodried waste ...reduce, also, waste impacts. ► Low waste impacts suggest biodried-waste landfilling. ► Biodried-waste in landfill can be used to produce energy
via biogas production.
In this paper, the effect of biodrying process on municipal solid waste (MSW) properties was studied. The results obtained indicated that after 14
d, biodrying reduced the water content of waste, allowing the production of biodried waste with a net heating value (NHV) of 16,779
±
2,074
kJ
kg
−1 wet weight, i.e. 41% higher than that of untreated waste. The low moisture content of the biodried material reduced, also, the potential impacts of the waste, i.e. potential self-ignition and potential odors production. Low waste impacts suggest to landfill the biodried material obtaining energy
via biogas production by waste re-moistening, i.e. bioreactor. Nevertheless, results of this work indicate that biodrying process because of the partial degradation of the organic fraction contained in the waste (losses of 290
g
kg
−1 VS), reduced of about 28% the total producible biogas.
Odours (OUE) and volatile organic compounds (VOC) emission during biological process used to treat MSW were studied under standardized conditions in order to detect potential risk for workers and ...population. Results obtained indicated that odours and VOCs emitted depend on the biological stability of waste measured by the dynamic respiration index (DRI) and a very good correlation were found between these parameters (OUE vs. DRI, r=0.96, p<0.001, n=6; VOC vs. DRI, r=0.97, p<0.001, n=6).
GC–MS study of the VOCs indicated the presence of a group of molecules that were degraded during the process. On the other hand, a second group of molecules, i.e. aromatic and halogenated compounds, and furan persisted in the waste sample, although molecule concentrations were always lower than Threshold Limit Value–Time Weighted Average (TLV–TWA).
•Products from (stripping-)scrubbing manure based flows are defined as animal manure.•Nitrogen (N) in recovered (stripping-)scrubbing products is present in mineral form.•Recovered N products ...performed similar as synthetic N fertilizer in crop trials.•Legal acceptance of recovered products as fertilizers would foster manure recycling.
Development and optimization of nutrient recovery technologies for agricultural waste is on the rise. The full scale adoption of these technologies is however hindered by complex legal aspects that result from lack of science-based knowledge on characterization and fertilizer performance of recovered end-products. Ammonium sulfate (AS) and ammonium nitrate (AN), end-products of (stripping-)scrubbing technology, are currently listed by the European Commission as high priority products with the potential of replacing synthetic N fertilizers. The legal acceptance of AS and AN will be highly dependent on critical mass of scientific evidence.
This study describes four different (stripping-)scrubbing pathways to recover ammonia with an aim to (i) assess product characteristics of ammonium nitrate (AN) and ammonium sulfate (AS) produced from different installations, (ii) evaluate fertilizer performance of recovered end-products in greenhouse (Lactuca sativa L.) and full field (Zea mays L.) scale settings and (iii) compare the observed performances with other published studies. Results have indicated that the recovered products might have a different legal status, as either mineral N fertilizer or yet as animal manure, depending on the used (stripping-)scrubbing process pathway. Nevertheless, no significant differences in respect to product characterization and fertilizer performance of AN and AS have been identified in this study as compared to the conventional use of synthetic N fertilizers. This indicates that recovered AS and AN are valuable N sources and therefore might be used as N fertilizers in crop cultivation.
This work aimed to measure the odour impact of untreated cow and pig slurries and treated (digestate and liquid fraction of digestate) manures when they were used on soil at a field scale, while also ...testing different spreading methods, i.e. surface vs. injection. Five experiments were performed in 2012–2016 on different farms. Odours were quantitatively (specific odour emission rate – SOER) (OUEm−2h−1) measured by using dynamic olfactometry and qualitatively, i.e. to obtain an “odour fingerprint”, by using an electronic nose (EN).
Anaerobic digestion was effective in allowing the reduction of potential odour emission from digestates, so that when they were dosed on soil, odours emitted were much lower than those from soils on which untreated slurries were used. Slurries/digestate injection reduced much more odour emitted by soils so that SOER tended to become more similar to that of the control (untreated soil) although the odours were slightly greater.
Odour fingerprint data indicated that there was a direct correlation between SOER and odour fingerprints. This was due to the ability of EN to detect ammonia, S-compounds and methane that were (the first two mainly), also, responsible for odours. Very good regression was found for Log SOER and EN by using a Partial Least Square (PLS) approach (R2=0.73; R2cv=0.66; P<0.01) for matrices used to fertilize soils in lab tests. Unfortunately, regression was not so good when odour data from field experiments on soil were used, so that EN cannot be proposed to replace olfactometry. EN fingerprints for control (Blank) and injected organic matrices were virtually identical, due to the creation of cavities in the soil during the injection that decreased the treated surface. Anaerobic digestion and subsequent digestate injection allowed us to reduce odour impact, avoiding annoyance to local inhabitants.
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•Anaerobic digestion reduces odours impact because of degradation of organic matter.•Anaerobic digestion (AD) coupled with manure injection reduced odour emissions.•Specific Odour Emission Rate (SOER) well correlated with electronic nose fingerprint•Electronic nose can replace SOER in measuring odour impact.
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•The storage facilities for animal manure determine ammonia and odour emissions.•These emissions cause environmental problems and annoyance to inhabitants.•The determination of ...emission rates is useful to quantify these problems.•Ammonia and odours have been detected studying four storage facilities during two years.•Both ammonia and odour emitted depended upon slurries’ characteristics and environmental parameters.
Ammonia and odour emissions from one lagoon (Lagoon 1: pig slurry) and three tanks (Tank 2: cow slurry; Tank 3: digestate from pig slurry and energy crops; Tank 4: digestate from pig and cow slurries plus energy crop) used for slurry storage were sampled for two years (2015–2017) in livestock farms that differed for animal breeding and manure management (anaerobic digestion).
On average, the ammonia emission rate (AER) was higher for Tank 3 (AER of 30.68 ± 28.1 g N-NH3 m−2 d−1) than for Lagoon 1 and Tank 2 and 4, i.e. 9.29 ± 14.89 gN-NH3 m−2 d−1, 9.38 ± 13.75 g N-NH3 m−2 d−1, 15.74 ± 21.91 g N-NH3 m−2 d−1, respectively. PLS regression analysis (R2 = 0.544; R2Adj. = 0.484) indicated that temperature was the main predictor of ammonia emitted, followed by concentration in the slurry of total ammonia and the relative percentage of volatile solids (VS).
On the other hand, PLS analysis (R2 = 0.529, R2adj. = 0.417) indicated that odour emissions from animal slurry storages depended similarly upon total solids and VS (both referred to fresh weight) slurry contents, TAN/TKN ratio and degrees of biological stability (measured by anaerobic biogas potential – ABP), resulting in the Specific Odours Emission Rates (SOER) of 12,124 ± 7,914 and 35,207 ± 41,706 OUE m−2 h−1, 65,430 ± 45,360 and 43,971 ± 53,350 OUE m−2 h−1, for Lagoon 1 and Tanks 2, 3 and 4. These results suggest covering the tanks to limit both ammonia and odour emissions.
Anaerobic digestion of nitrogen (N) rich substrates might be hindered when ammonia (NH3) formation reaches toxic levels for methanogenic microorganisms. One possible strategy to avoid inhibiting ...conditions is the removal of NH3 from digestate by stripping and scrubbing technology and by recirculating N depleted digestate back to the digester. This study aimed to i) monitor the performance (mass and energy balances) of a full scale digestate processing cascade that includes an innovative vacuum side stream NH3stripping and scrubbing system, ii) assess the production cost of ammonium sulphate (AS) solution and iii) evaluate its fertiliser quality. The use of gypsum to recover NH3 in the scrubbing unit, instead of the more common sulphuric acid, results in the generation of AS and a fertilising liming substrate. Mass and nutrient balances indicated that 57% and 7.5% of ammonium N contained in digestate was recovered in the form of a 22% AS and liming substrate, respectively. The energy balance showed that about 3.8 kWhel and 59 kWhth were necessary to recover 1 kg of N in the form of AS. Furthermore, the production cost of AS, including both capital and operational costs, resulted to be 5.8 € t−1 of digestate processed. According to the fertiliser quality assessment, this technology allows for the recovery of NH3in the form of salt solutions that can be utilised as a substitute for synthetic mineral nitrogen fertilisers.
•A novel ammonia stripping process was monitored at a fullscale digestate processing facility.•57% of ammonium nitrogen contained in digestate was recovered as ammonium sulphate (22%).•Nitrogen in recovered ammonium sulphate is present entirely in mineral form.•The cost for the nitrogen recovery system amounts to 5.8 € per tonne of digestate processed.•Biobased ammonium sulphate represents an interesting alternative to synthetic nitrogen fertilisers.
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