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The rising generation of organic waste (OW) can be a concern, representing at the same time a valuable opportunity for the phosphorous (P) recycling; however, yet little is known about plant-available P release from this source. In this work, two anaerobic digestates, from agro- (AWD) and bio-waste (BWD), and their respective composts (AWC and BWC), were selected to assess their P-release via sequential chemical extraction (SCE) and P species via solution 31P-NMR in NaOH+EDTA extracts. These products were also tested for the relative-P efficiency (RPEsoil) in a soil incubation (30 mg P kg−1), in comparison with a chemical-P source and a reference compost. The organic products were also compared for the ryegrass relative-P efficiency (RPEtissue) at the same P-rate (30 mg P kg−1), in a 112-day pot experiment in an Olsen-P poor soil (−1), under a non-limiting N environment. The NaOH+EDTA extractions showed that inorganic P prevailed in all samples as proven by solution 31P-NMR. SCE showed very different labile-P (H2O+NaHCO3) and AW doubling BW products (84 vs. 48%); this was also confirmed by the soil incubation test in which AWD and AWC attained the best RPEsoil. Pot tests generally confirmed laboratory outcomes showing that AWD and AWC attained the best RPEtissue, from 3 to 4-folds of the BWD and BWC performance. The results showed that the feedstock mainly affects plant P availability from recycled OW and that their SCE are very informative in the description of plant-available P from this type of products to be used in rational fertilization plan.

Compost can provide nitrogen (N) and especially phosphorous (P) available for plant growth, thus representing a potential alternative to chemical P-fertilizers a non-renewable resource. However, little is known about their residual capacity to provide plant-available P. In this study four compost: a green waste compost (GWC), one from anaerobically-digested bio-waste (DC), one from sewage sludge (SSC), and one from bio-waste (BWC), were compared (10 and 20 Mg VS ha−1) in a ryegrass pot test (112 days), for their N- and P-relative mineral fertilizer equivalence (MFE; %) vs. a chemical fertilizer (NPK). After the test period, the exploited treatments were tested for their MFE during an additional ryegrass growth cycle (112 days) in an N-rich environment (N+). After 112 days, the pot test showed that DC and SSC produced dry biomass in the same range as did NPK, attaining the best N-MFE (80–100%) and P-MFE (100–125%), whereas GWC and BWC performed poorly (60–80 and 80–90%; N-MFE and P-MFE). At the end of the first growth cycle, DC and SSC still showed relevant Olsen-P (20–30 mg kg−1). This was reflected in the best ryegrass P-MFE in DC and SSC at the end of the second growth cycle (N+), after 224 days (100–110%), whereas BWC and GWC poorly performed (90–95%). DC and SSC may therefore represent valuable sources of N available for plant nutrition in the short term, and also represent medium-term valuable P sources, alternative to rock phosphate P fertilizers. This promising approach need further field-scale investigation to confirm the medium-long term capacity of composts to be alternative to rock phosphate P fertilizers.

International audience; In recent years, anaerobic digestion of organic waste (OW) is rapidly appearing as a winning waste management strategy by producing energy and anaerobic digestates that can be used as fertilizers in agricultural soils. In this context, the management of the OW treatment process to maximize agro-system sustainability satisfying the crop nutrient demands represents the main goal. To investigate these traits, two protocols to assess the plant availability of digestate nitrogen (N) and phosphorus (P) were evaluated. With this aim, the N and P availability was determined on 8 digestates and 2 types of digestate-based compost from different OW via sequential chemical extractions (SCE). In addition, the digestates were tested in soil incubations and in plant pot tests with Italian ryegrass and compared with chemical fertilizer and a non-amended control soil. The N extracted from digestates via SCE was related to soil N mineralization and plant N recovery. The C: N ratio had negative impact on mineralized N and its recovery in shoots (ShootsN = −0.0085.(C/N)+0.172, r2 = 0.67), whereas water extractable mineral N was positevely related to the root N apparent recovery fraction (N-ARF) with (RootsN = 5E−5.Nsolublemin+0.0138, r2 = 0.53). The shoot P-ARF was positively correlated with the inorganic water extractable fraction of P (ShootsP =0.1153.H2O-Pi−0.2777.H2O-Po+0.0249, r2 = 0.71) whereas the root P-ARF was positively correlated with the less accessible fractions (RootsP = (b) 0.0955.NaHCO3-Po+0.0955.NaOH-Po-0.0584NaHCO3-Pi+0.0128, r2 = 0.8641). Feedstock digestate typology impacted the N and P recovery results leading to a better description of the typology properties and a first nutrients ARF prediction.

Gli ammendanti compostati (compost) possono rappresentare una fonte di fosforo (P) alternativa a quello minerale, risorsa non rinnovabile, tuttavia poco si conosce sulla loro capacità di fornire P disponibile per la nutrizione vegetale. In questo lavoro quattro compost (ACV; ACM 1; ACM2; ACF), sono stati testati per la loro capacità di fornire P nel corso di due cicli di coltivazione di loietto in vaso: senza / con ausilio di fertilizzazione azotata (N-;N+; 112+112 gg). In N- solo ACM1 e ACF presentavano asportazioni di P maggiori rispetto al fertilizzante chimico N-P-K (+5%). In N+ tutti i compost presentavano asportazioni di P superiori a N-P-K (+7%), a parte ACV (-5%). I compost possono rappresentare una fonte di P disponibile alla nutrizione vegetale nel medio-lungo periodo, lasciando nel suolo dotazioni interessanti di P potenzialmente disponibile ad un successivo ciclo colturale, al contrario di quanto evidenziato con la fertilizzazione fosfatica chimica. Summary Compost may represent a source of phosphorus (P) alternative to the mineral one, a non-renewable resource, but little is known about their capacity to provide plant-available P. In this article four compost (ACV, ACM 1 , ACM 2 , ACF), have been tested in two cultivation cycles for their capacity to furnish P on ryegrass grown in pot, without and with mineral nitrogen supply (N-; N +; 112+112 days). In N-ACM 1 and ACF showed higher P (+5%) uptake compared to the chemical fertilizer (N-P-K). In N+ all compost showed higher P uptake in comparison to N-P-K (+7%), apart from ACV (-5%). Some compost may therefore represent a valuable source of P for plant nutrition in the medium-long term, leaving also appreciable level of potentially available-P in soil, oppositely to what showed following a phosphate chemical fertilization.

Wet and dry-batch anaerobic digestion, and composting are common technologies in food waste (FW) management, resulting in different outputs. However, the effects of composting on carbon dioxide (CO

In this work mild-alkaline semi-solid state pretreatments (NaOH: 2; 4; 6 %, at 25 °C, TS 10 %) were applied to Arundo donax, Sorghum bicolour L. and wheat straw (Triticum aestivum, L.) to test their efficiency on anaerobic biodegradability. The simple sugars (glucose, xylose, arabinose) from structural carbohydrate and the lignin content were analyzed in raw treated samples. Besides to this their structural variation were assessed by means of FT-IR and thermal analysis. The recovery of glucose (1–2 %), xylose (0.4–2.5 %), and arabinose (0.1–8.7 %) in the alkaline eluate showed the treatment produced moderate hydrolysis of the structural components. This was confirmed by the moderate variation of glucose, xylose, arabinose and lignin content determined in the solid residue. On the contrary the FT-IR analysis showed the solid fraction of samples had intense variations in the cellulose and hemicellulose structure (mainly saponification of ester bounds), also confirmed by thermal analysis. The maximum degradation rate (−dx/dtmax; s−1) of cellulose and hemicellulose increased in both Arundo and Sorghum, indicating a structural cleavage. Straw showed moderately increased resilience of hemicellulose by small temperature shifts. A general decrease of the apparent activation energy (E a ) was found in all samples as an indication of decreased structural order favourable to enzymatic hydrolysis and the additional anaerobic biodegradability, as proved by the anaerobic tests in which A. donax showed the highest increase of biodegradability at NaOH 6 % (+30 %) > wheat straw (+22 %) > Sorghum (11 %).

A compost (CHW) from the residue of the dry-batch digestion of household waste and one (CSD) from the solid fraction of anaerobically digested maize were tested for their phosphorus (P) release by means of sequential extraction. The products were then compared in a soil incubation (30 mg P kg−1) for their capacity to supply potentially available P (Olsen-P), and in a pot trial to test plant-available P on Italian ryegrass over 112 days. A municipal solid waste compost (MSWC) and an inorganic P source (P-chem) were added as reference in addition to a not-fertilized control (control). Sequential extraction showed that CSD had the greatest labile P (NaHCO3 30 % > H2O 29 % > HCl 23 % > NaOH 10 %). On the contrary, CHW showed the greatest recalcitrant P (HCl 44 % > NaHCO3 10 % > H2O 11 % > NaOH 8 %), being similar to MSWC (HCl 65 % > NaOH 13 % NaHCO3 12 % > H2O 5 %). This was in agreement with the different amorphous or crystalline degree of the sample as determined by XRD. Also in soil, CSD showed the highest level of Olsen-P at the beginning of incubation (28.5 mg kg−1), while CHW and MSWC had the lowest level of Olsen-P throughout incubation (4.6 and 6.0 mg kg−1 on average), very close to the Control (3.0 mg kg−1). Plant test showed that CSD also had the greatest available P (ARF: 12.5 %), followed by P-chem (5.6 %) > MSWC (4.2 %) > CHW (2.5 %). From sequential extraction and physical analysis, it therefore appears that the presence of significant amounts of Ca, such as in CHW and MSWC, shifted P toward low soluble Ca-P compounds, thus reducing the P available for plant nutrition.

I rifiuti organici sottoposti a trattamento biologico possono rappresentare una fonte di fosforo (P) per le colture. Il trattamento integrato anaerobico-aerobico della FORSU è un’importante realtà in Italia, tuttavia la sua influenza sulla disponibilità potenziale del P è poco conosciuta. Nel presente articolo, due digestati anaerobici (DA) ed i rispettivi compost (ACM) sono stati analizzati per la stabilità biologica (OUR) e sottoposti a frazionamento del P-inorganico (Pi) tramite estrazione sequenziale (SCE), inoltre la disponibilità potenziale di P (P-Olsen) è stata valutata mediante incubazione in suolo. I risultati evidenziano che il compostaggio incrementa la stabilità biologica dei DA, necessaria per il corretto impiego in campo, e che poco influenza il frazionamento del P, che è risultato determinato principalmente dalle caratteristiche dei DA. Il frazionamento del Pi fornisce utili indicazioni relative alla potenziale disponibilità dell’elemento nel suolo.

This paper addresses the anaerobic digestion (AD) of seven biomass crops: three multi-annual species, Arundo donax (Arundo), Panicum virgatum (Switchgrass) and Sorghum Silk; three sorghum hybrids (B133, Sucros 506 and Trudan Headless); one Maize hybrid as reference crop for AD. Dry biomass yield (DBY) was assessed in a field plot experiment in Northern Italy, and biomass samples were subjected to chemical analysis (volatile solids (VS), raw proteins and lipids, soluble sugars, starch, structural carbohydrates and lignin). Thereafter, an AD assay was carried out in batch mode with 4 g VS l−1 at 35 °C for 58 days, during which time potential methane yield (ml CH4 g−1 VS) was determined. Gross energy yield (GE = DBY × VS × potential CH4 yield × methane lower heating value) and cumulative energy demand (CED) led to net energy yield (NE = GE − CED) and energy efficiency (EE = GE/CED) as indicators of crop suitability for AD. Arundo, B 133 and Sucros 506 achieved ±10% DBY compared to Maize (this latter, 27.8 Mg ha−1). Conversely, Maize prevailed in terms of potential methane yield (316 ml CH4 g−1 VS). Among the six alternative crops, Arundo and Switchgrass exhibited the lowest values (average, 216 ml CH4 g−1 VS), associated with low kinetics of degradation. This is consistent with the two crops’ characteristics: low easily degradable fractions as lipids, soluble sugars and starch; high structural carbohydrates and lignin. Maize achieved a top level also in GE (286 GJ ha−1, corresponding to ca. 8400 Nm3 CH4 ha−1) and NE (248 GJ ha−1). B 133 and Sucros 506 were undifferentiated from Maize in NE (their average, 215 GJ ha−1), whereas Trudan Headless and the three multi-annual species were out-performed (average NE, 149 GJ ha−1). Conversely, Maize ranked worst in EE (7.4 GJ GJ−1) while sorghumB 133 and Arundo attained top levels (average, 12.1 GJ GJ−1), thanks to a good GE associated with a modest CED in B 133; to a very low CED in Arundo. It is concluded that alternative crops to maize deserve attention in view of a low need of external inputs but necessitate improvements in biodegradability (harvest stage and biomass pre-treatments) to bridge the gap in the amount of net energy produced.

In this work a residue of dry-batch anaerobic digestion (DB) from the organic fraction of municipal solid waste, its composted homologous (CDB), and a municipal solid waste compost (MSWC) were characterized for their main physico-chemical traits and biological stability [oxygen uptake rate (OUR)]. These were then compared in soil incubations at 200 mg N kg-1, to assess carbon (C) and nitrogen (N) mineralization. The products’ nitrogen apparent recovery fraction (ARF) was assessed in a pot trial on Italian ryegrass. DB showed the highest OUR, followed by CDB and the more stable MSWC: 161.7; 20.7 and 5.7 mmol O2 kg-1 VS h-1, partially in agreement with the potentially mineralizable C pools in soil: 58.4; 16.6 and 19.5 % and their kinetics (k, 0.1906; 0.1405 and 0.1377 day-1). Composting greatly reduced the total carbon dioxide (CO2) emissions from 7,950 to 3,449 mg kg-1 in DB and CDB, even higher than MSWC (1,936 mg kg-1). After intense N-immobilization in soil (-22.3 %), DB finally reduced the gap (-6.9 %), also having a positive ARF (5.0 %), while CDB had greater N-immobilization (-12.9 %) and a negative ARF (-3.4 %). MSWC showed 3.8 % N-mineralization, and an intermediate ARF (2.7 %). The management of DB for plant nutrition therefore seems difficult since DB can furnish nitrogen not easily synchronizable with plant growth due to its release pattern characterized by initial immobilization. Composting increased stability but amplified N-immobilization due to the high C:N ratio of the bulking agent. A prolonged and more balanced composting process can reduce this restriction, aligning CDB with MSWC.

Composting is considered a suitable process for organic waste management, providing stable products that can be safely utilized as fertilizers, but little is still known about the variation of phosphorous (P) extractability during the stabilization process. In this work, sequential chemical extraction (SCE) with increasing strength extractants (H2O; 0.5M NaHCO3 pH 8.5; 0.1M NaOH, 1M HCl) was applied for P speciation over 56days of composting of either agro-industrial or urban wastewater sludge with green waste treated (AICFe+; SSCFe+) or not (AICFe-; SSCFe-) with FeSO4 (2%v/v). Composting strongly reduced the H2O-P, promoting the organic-P (Po) mineralization from the labile fraction (H2O+NaHCO3 40%), in addition to the increases of NaHCO3- and HCl-extractable inorganic-P (Pi) in both AICFe- and SSCFe- (+20% on average). The FeSO4 treatment did not negatively affect the process, reducing the Po mineralization during composting by increasing the NaOH-P, also protecting this fraction from fixation in the sparingly soluble fraction. The final P fractionation (%) was in AICFe-: NaOH (41)=NaHCO3 (38)>HCl (18)>H2O (3); in AICFe+: NaOH (53)>NaHCO3 (24)=HCl (22)>H2O (2); in SSCFe-: NaOH (46)>NaHCO3 (29)>HCl (21)>H2O (4) and in SSCFe+: NaOH (66)>NaHCO3 (13)>HCl (20)>H2O (1). Composting reduced the more easily leachable fraction (labile-Po), reducing the risk of P loss by increasing the long-term available P fraction (NaOH-P). This was enhanced by the FeSO4 addition. Further investigation into soil behaviour and plant availability of P from this source is needed.

In this work four stable bio-waste composts (C1, C2, C3, C4) were selected on the basis of their increasing water soluble P (H2O-P). The P speciation was assessed via sequential chemical extraction (SCE) on the same products. Moreover, the plant-available P was assessed via apparent recovery fraction approach (ARF) in a pot test on ryegrass over 21 weeks at 15 mg P kg−1 of soil. An inorganic P source (P-chem) was added as a reference at the same P rate in addition to a non-fertilized control (Control). SCE showed that the sparingly soluble P (HCl-P) was the most important fraction in all composts: C1 (HCl 65% > NaHCO3 17% = NaOH 17% > H2O 1%); C2: (HCl 51% > NaOH 23% > NaHCO3 18% > H2O 7%); C3: (HCl 58% > NaOH 21% > NaHCO3 12% > H2O 9%); C4: (HCl 39% > NaOH 23% > NaHCO3 22% > H2O 16%). The plant test showed that the different treatments had a different ARF (%) at the first harvest: P-chem (14.7)> C4 (14.4)> C3 (14.1)> C2 (3.4)>C1 (3.1), compared to the cumulated ARF (%) of the six harvests: C4 (50.1)> C3 (35.0)> C1 (21.1)> C2 (18.3)> P-chem (17.4). Data showed a good correlation of H2O-P vs. plant ARF at the first harvest and a good correlation of labile P (H2O-P + NaHCO3-P) vs. total plant ARF over 21 weeks. The free and labile P forms from SCE can be a valuable tool in the assessment of fast and middle term plant-available P from stable bio-waste composts in calcareous soils.

Organic acids are envisaged as alternative catalysts to strong mineral acids, in pre-treatment of ligno-cellulosic biomass for anaerobic digestion (AD). To evaluate this hypothesis, an untreated control and four pre-treatments (25 °C for 24 h) involving two levels of maleic acid (34.8 and 69.6 kg m−3), alone and combined with sulphuric acid (4 kg m−3), were studied in three agricultural substrates: Arundo (aka giant reed), Barley straw and B133 fibre sorghum. Methane production was assessed in a batch AD assay (35 °C for 51 days) with 4 g L−1 of volatile solid (VS) load. Fibre composition and structure were investigated through chemical analysis and Fourier transform infrared (FTIR) spectrometry. Arundo and B133 that were the most and least recalcitrant substrate, respectively, staged the highest and lowest increase in methane with high maleic acid: +62% over 218 cm3 g−1 of VS in untreated Arundo; +36% over 284 cm3 g−1 of VS in untreated B133. Barley straw showed an intermediate behaviour (+41% over 269 cm3 g−1 of VS). H2SO4 addition to maleic acid did not improve CH4 output. The large increase in methane yield determined by pre-treatments was reflected in the concurrent decrease of fibre (between 14 and 39% depending on fibrous component). Based on FTIR spectra, bands assigned to hemicellulose and cellulose displayed lower absorbance after pre-treatment, supporting the hypothesis of solubilisation of structural carbohydrates and change in fibre structure. Hence, maleic acid was shown a suitable catalyst to improve biodegradability of ligno-cellulosic biomass, especially in recalcitrant substrates as Arundo.

The liquid (LS) and solid fraction (SS) of a biogas slurry from dedicated crops, the composted solid fraction (CSS) and a municipal solid waste compost (MSWC) were compared in a soil incubation at 200 mg N kg −1 , to assess CO 2 emissions and potential C and N mineralization. Products were also compared for nitrogen apparent recovery fraction (ARF) in a pot trial with Italian ryegrass. LS showed the highest C mineralization (63.6%), soil mineral N (>100 mg kg −1 ), and ARF (50.3%). SS showed 21.6% C mineralization, slight N immobilization (23.6 mg kg −1 ) and 7.3% ARF. In CSS, a 5.1% C mineralization in soil added to 26.3% C loss during composting, resulting in 31.4% overall C loss. Moreover, composting SS to CSS curbed the emission from 4210 to 1100 mg CO 2 kg −1 soil, still double than the reference MSWC (507 mg CO 2 kg −1 soil). Despite high mineralization of supplied carbon, LS emitted less CO 2 than SS: 936 mg CO 2 kg −1 soil. It appears, therefore, that LS acts as a source of easily available nitrogen, while SS plays the role of an amendment with some limitations due to soil N immobilization. CSS mitigates N immobilization, but the composting process determines relevant CO 2 losses to the atmosphere.

In the near future, composted bio-solids are expected to play a major role in agriculture. In order to evaluate their contribution to plant growth and nutrition, a mixed sorghum–poultry manure compost was prepared using 15N-labeled materials. Four treatments were compared in a pot trial: fertilized with compost vs. unfertilized, both of them combined with (cultivated) and without (bare) plants of fibre sorghum (Sorghum bicolor [L.] Moench.). Soil mineral nitrogen (N-min), plant growth, and N uptake were monitored over a whole growing season (167 d after fertilizer treatment; DAT). Apparent soil mineralization (ASM) and apparent recovery fraction of nitrogen by the plant (ARF) were assessed, as well as the 15N recovery fraction by the plant (15NRF). Compost enhanced sorghum biomass at mid growth (+ 200% of dry weight compared to the unfertilized). However, the difference between the control and the fertilized plants progressively decreased towards the end of the season (+ 70%). Fertilized and unfertilized plants followed different growth patterns over time, although of the same sigmoid type. Conversely, N concentration in plant tissues followed a common dilution curve, indicating that fertilized sorghum efficiently used the supplied N, avoiding luxury consumption. Apparent soil mineralization approximately reached 45% of compost total N in pots without plants. Apparent recovery fraction attained 100% at about two third of the growing season (DAT 111), then declined to about 50% because of root and leaf decline. Compared to it, 15NRF only reached ≈ 20% at mid growth (DAT 83), then declined to 12%. Despite the large difference in absolute values, ARF and 15NRF exhibited a significant correlation, indicating a common trend in time. In contrast to 15NRF, the amount of nutrient derived from fertilizer (Ndff) taken up by the plant decreased over the growth season, proving that compost contributed more to plant nutrition in the early (Ndff ≈ 50%) than in the late growing season (Ndff ≈ 25%). The large difference between ARF and 15NRF suggests that sorghum exerted a strong nutrient demand on the soil and on the fertilizer. Both 15NRF and ARF are considered valuable traits: the former better describes fertilizer behavior and actual supply of N, while the latter outlines the overall effect of fertilizer application on crop nutrition.

The assessment of soil respiration and nitrogen (N) mineralization under the addition of organic fertilizers is a matter of ever increasing interest. Aiming at a deeper insight into the subject, an aerobic liquid-based incubation was set up for the coupled respiration and N-mineralization over 360 h in a closed system, comparing one compost and one vinasse at rates of 300 and 600 mg N/kg soil, plus an unfertilized control. The system allowed the manometric measurement of themicrobial activity, and the N-mineralization in the suspension via solely NH4-N determination. A set of substrate-induced respiration (SIR) tests was run to investigate the effects of nutrients and nutrients glucose addition on the soil respiration and N-mineralization of the five fertilizer treatments, in comparison with basal respiration in water. In water, compost showed a total net N-mineralization of +0.7 and -6.3% at the low (C1) and high (C2) dose respectively, whereas vinasse nominally reached 100% for both doses (V1 and V2). Soil respiration ranged between 3,269 and 18,389mg O2/kg dry soil of the unfertilized and V2. SIR tests showed that the respiration of compost-treated soil was boosted by nutrients in C2 more than in C1. Conversely, C1 was boosted by nutrients+glucose more than C2, indicating a combined of a nutrient- and carbon dose-dependent mechanism. These findings were confirmed by the N-mineralization, because C2 consumed almost threefold the NH4-N added to the system compared to C1. Vinasse-fertilized soil received a similar benefit from nutrients and nutrients+glucose. The additions of inducing substrates showed how compost and vinasse respiration are dose dependent: the lower the dose, the higher the respiration relative to the amount of added carbon in a carbon starved system. The incubation method adopted here appears to be a valid and rapid tool in the study of the effects of energy and nutrient constraints on respiration and N-mineralization dynamics in soils amended with biosolids.

Compost (CP) made from 70% ligno-cellulosic compounds and 30% sewage sludge was studied as a component of growing media in a 6-month Philodendron cultivation. CP's agronomic viability was evaluated via four plant-growth media containing 25–50–75–100% CP and white sphagnum peat (WP) in comparison to a commercial substrate with white and black peat. Plant nutrition conditions were investigated by determining macro- (TKN, P, K, Ca, Mg and micronutrients (Mn, Fe, Cu, Zn, Na) and heavy metals (Ni, Cd, Cr, Pb) in roots and shoot tissues. Data were compared by vector analysis against control. Even if no leaf injuries were visible after 6-months’ growth, a CP ratio of up to 50% caused growth depression of canopy tissues, as attested by the 37 and 36% reduction in total leaf dry weight and leaf area, respectively. Root growth decline was also notable at 25% CP, where 38% root dry weight reduction implied a significant increase (46%) in shoot–root dry weight ratio. The investigation on nutrient tissue content showed high accumulation of Ni, Fe, Cr, Zn, Cd, Mn, Mg and P in roots; Mg appeared related to K deficiency. Above-ground nutritional status showed a severe lack of P, Mg and Mn. Vector analysis suggests the sewage sludge CP in Philodendron pot cultivation produces many such effects like direct toxic action and antagonistic action, resulting in a general nutrient imbalance in plants.

Twelve hydrothermal pre-treatment combinations of temperature (150 and 180 °C), time (10 and 20 min) and acid catalyst (no catalyst; H2SO4 at 2% w/w immediately before steam cooking or in 24-h pre-soaking) were tested to assess their effects on methane yield of Giant reed biomass vs. untreated control. A batch anaerobic digestion was conducted with 4 g VS l−1 at 53 °C for 39 days. Untreated biomass exhibited a potential CH4 yield of 273 ml g−1 VS; the four pre-treatments without acid catalyst achieved a 10%, 7%, 23% and 4% yield gain in the respective temperature/time combinations 150 °C/10 min, 150 °C/20 min, 180 °C/10 min and 180 °C/20 min. Conversely, the eight pre-treatments with H2SO4 catalyst incurred a methanogenic inhibition in association with high SO 4 2 - concentration in the hydrolysate, known to enhance sulphate reducing bacteria. Furfurals were also detected in the hydrolysate of five strong pre-treatments with H2SO4 catalyst.

Seven composts were used as growing media for lettuce mixed with peat at 25 and 50% (v/v). On the unblended composts and the resulting 14 mixes were determined the main physical-chemical characteristics and the stability by means of a respirometric test in a liquid environment. The potential nitrogen (N)-mineralization capacity of the mixes was measured during the respirometric test solely by the ammonium (NH+ 4-N) determination. The lettuce pot-growing test was performed with and without fertilization; plant biomass and total Kjeldahl nitrogen (TKN) tissue content were measured after cultivation for two months. Compost origin, rate in substrates and fertilization affected plant growth and nitrogen uptake. Multiple regression analysis showed that the stability, proved to be a good predictor for plant growth inhibition. Moreover N-mineralization capacity showed a good fitting with plant uptake. The coupled stability and nitrogen mineralization test gives reliable information about the potential constraints in compost-based growing media.

Three blends formed by: (i) food processing waste (CP(FP)), (ii) waste water sewage sludge (CP(WW)), and (iii) their mixture (CP(FP+WW)), blended with tree pruning as bulking agent, were composted over 3 months. During composting the blends were monitored for the main physical-chemical characteristics: temperature, oxygen saturation level (O(2)%), pH, total and volatile solids, total organic carbon, and organic nitrogen (N(org)). In addition to the main parameters, the dissolved organic carbon (DOC), the inorganic nitrogen and the Oxygen Uptake Rate (OUR) were monitored. All the mixtures easily reached a peak temperature around 70°C, related to the lowest O(2)%. After 90 d, CP(FP), CP(FP+WW), and CP(WW) showed an organic matter mineralization of 43%, 35% and 33%, respectively; CP(FP) fitted an exponential model while both CP(FP+WW), and CP(WW) fitted a logistic model. During composting an OUR reduction of 79%, 78% and 73% was registered in CP(FP), CP(FP+WW), and CP(WW), respectively; the OUR successfully fitted the adopted exponential model and well reflected the stabilization process in time. The N(org) recovery at the end of the process was positive only in CP(WW) (11.6%). The DOC significantly decreased during the composting process but did not successfully fit any model. The mineral nitrogen did not follow the typical pattern with NH(4)(+) disappearance and NO(3)(-) accumulation. Strong NO(3)(-) losses were evident in all blends, while NH(4)(+) accumulations were detectable only in CP(FP), and CP(FP+WW). The NH(4)(+)/NO(3)(-) ratio did not satisfactorily reflect the composting process over time. The comparison of the first order (exponential) and logistic (sigmoidal) models applied to the OUR and OM course highlights the role of mineral nitrogen as limiting factor during composting of the more stabilized sludge.

International audience; Humic-like acids (HLA0, HLA70, HLA130, HLA730) were extracted from composts obtained from sewage sludges and trimmings after 0, 70, 130 and 730 days of composting, respectively. In addition, HLA130 was fractionated using SEC-PAGE set-up. Fluorescence spectroscopy revealed that HLA0 was the only sample to contain emission bands characteristic of protein-like compounds (Λexc/Λem: 280/350) and chlorophyll (Λexc/Λem: 420/660). Emission intensities above 400 nm and HIX both varied in the order : HLA70 > HLA130 > HLA730 > HLA0 and increased as the fraction molecular size decreased. Thus, the formation of long wavelength emitting fluorophores during composting is connected to the humification process. These fluorophores are mainly concentrated in the low molecular size fraction obtained by SEC-PAGE fractionation of composts.

Humic-like acids (HLA) were extracted from compost at the beginning and after 70, 130 and 730 days of maturation in order to be investigated for their ability to induce the transformation of 2,4,6-trimethylphenol under irradiation at 365 nm. The rate of 2,4,6-trimethylphenol phototransformation in the presence of HLA (25 mg l(-1)) varied within HLA 0HLA70 approximately HLA 130 approximately HLA 730. The changes of photoinductive capacity paralleled the changes of HLAs absorptivity indicating that the formation of photoinductive constituents is related to that of the colored moieties. The polyacrylamide gel electrophoresis analysis showed that intensity of all humic electrophoretic fractions significantly increased during the first 70 days of maturation but did not undergo significant changes for longer composting times. These data confirm the changes of HLS during composting.

A new method was developed for the simultaneous determination of the intrinsic carbon and nitrogen mineralization capacity of organic matter (OM) sources by means of an aerobic incubation in suspension. The proposed method is based on determination of the oxygen consumption, monitored indirectly via pressure measurement, and on determination of nitrogen mineralization, through the periodical measurement of NH 4 + -N, in a liquid suspension of the samples. The suspension is standardized in terms of nutrient composition and pH, and well-controlled incubation conditions that can be enforced as desired. This method rules out the effect of soil conditions and thus reflects the intrinsic properties of the OM. The method is faster and more reproducible than soil incubation tests that are currently used. In such a system, it is important that nitrification is inhibited to avoid oxygen consumption by nitrifiers and prevent the production of gaseous nitrogen compounds. Two nitrification inhibitors, N -allylthiourea and 2-ethynylpyridine, were tested at different concentrations for three reference samples, soil, bark and manure. Both inhibitors completely suppress NO 3 − formation without suppressing the heterotrophic microbial activity, thus allowing the correct determination of the oxygen uptake rate (OUR). When nitrification inhibitors were added, nitrous oxide could not be detected anymore in the gas phase of the system, which confirms that nitrification was inhibited and indicates that denitrification and nitrifier denitrification activity was negligible. N mineralization rates were determined by frequent sampling from the liquid phase of the system without disturbing the pressure measurement during the incubation and subsequent determination of NH 4 + -N. The method presented allows for the reliable and relatively easy and cheap, simultaneous determination of carbon and nitrogen mineralization rates for a wide range of OM sources.

The agronomic performance and the mineral composition and trace element content in Begonia semperflorens “Bellavista F1”, Mimulus “Magic × hybridus”, Salvia splendens “maestro”, and Tagete patula × erecta “Zenith Lemon Yellow”, were tested by growing the plants on substrates of white peat and 25–50–75–100% green waste and sewage sludge (80% + 20% v/v) compost (CP). A commercial peat medium of black and white peat (2:1 v/v) was used as control. At flowering, the agronomic parameters were compared by ANOVA and plant nutritional status was compared by vector analysis. Substrate-species interactions (P < 0.001) were evident for all measured parameters. In the 25% CP medium all the species showed an increase or preservation of the studied agronomic parameters. Begonia grown in 25% CP, showed the highest dry weight (DW) and number of flowers. Other treatments were comparable to the control. Mimulus and Salvia showed the highest DW in the 25–50% CP. Mimulus, after a DW increase up to 50% CP, showed the steepest reduction as the CP increased further. Tagete showed no differences in DW up to 50% CP, or in flower number up to 25% CP, compared to the control. The additional increases of CP in the medium showed a DW decrease similar to that of Salvia. Vector analysis showed the use of compost mainly induced a decrease of P concentration in tissues, except for Begonia which remained unchanged. Plant tissues showed a general P reduction due to a dilution effect in the low compost mixtures (25–50%) and a deficiency in the higher CP mixtures. In contrast, an increase of Mg in the aboveground tissues of all species was detectable as compost usage increased, with the exception of Salvia which suffered a Mg deficiency. Vector analysis also highlighted a Ni and partial Fe deficiency in Tagete and Salvia.

Humic acids (HA)-like extracted from compost at the beginning (t(0)) and after 130 days of composting (t(130)) were fractionated by coupling size exclusion chromatography to polyacrylamide gel electrophoresis (SEC-PAGE). HA-like fractions with the same molecular size (MS) and electrophoretic mobility were pooled and further characterised by analytical polyacrylamide gel electrofocusing (EF) and compared with HA separated from a Typic Chernozem soil. During the composting process all fractions were subjected to quantitative and qualitative modifications: the high MS fraction was degraded, the mid MS fractions were qualitatively changed, the content of low MS fractions increased and changed qualitatively. The main changes in EF pattern of the non fractionated HA-like t(130) were associated to low MS fractions. Such data seem to be reliable for explanation what mechanisms and monitoring of the evolution of the compost organic matter for their agricultural uses.

Three blends formed by: agro-industrial waste, wastewater sewage sludge, and their mixture, blended with tree pruning as bulking agent, were composted over a 3-month period. During the composting process the blends were monitored for the main physical and chemical characteristics. Electrofocusing (EF) was carried out on the extracted organic matter. The EF profiles were analyzed by principal component analysis (PCA) in order to assess the suitability of EF to evaluate the stabilisation level during the composting process. Throughout the process, the blends showed a general shifting of focused bands, from low to high pH, even though the compost origin affected the EF profiles. If the EF profile is analyzed by dividing it into pH regions, the interpretation of the results can be affected by the origin of compost. A good clustering of compost samples depending on the process time was obtained by analyzing the whole profile by PCA. Analysis of EF results with PCA represents a useful analytical technique to study the evolution and the stabilisation of composted organic matter.

To use compost appropriately in agriculture it is extremely important to estimate the stabilization level of the organic matter. In this work, two different piles of compost were studied by means of (i) humification parameters (degree of humification––DH, humification rate––HR, humification index––HI) prior to and after enzymatic hydrolysis of the extracted organic carbon, (ii) watersoluble organic carbon (WSOC) and (iii) water-soluble nitrogen. A significant relationship between composting time, WSOC and humification parameters after enzymatic hydrolysis (DHenz ;H R enz ;H I enz) was found. � 2003 Elsevier Ltd. All rights reserved.

In questo lavoro è stata valutata la produzione potenziale di metano (CH4) di due colture poliennali (Arundo e Switchgrass) e di tre ibridi di sorgo annuale (Trudan H., B 133 e S 506), coltivati presso l’azienda agraria dell’Università di Bologna. Sulle biomasse sono stati determinati i principali zuccheri solubili (glucosio, fruttosio), carboidrati strutturali (cellulosa, emicellulosa) e lignina, nonché la produzione specifica di CH4 attraverso un saggio di incubazione anaerobica (58 gg, 4 g SV l-1). Le colture annuali presentavano una maggiore biodegradabilità (66-70%) rispetto alle poliennali (56-58%), con conseguenti maggiori rese di CH4 (263 vs. 222 ml g-1 SV). La biodegradabilità di queste biomasse appare influenzata positivamente dal contenuto in carboidrati solubili, mentre quelli strutturali e la lignina presentano correlazioni negative. Le colture in esame, potenzialmente alternative al mais, meritano attenzione per i bassi input colturali, ma richiedono azioni di miglioramento della biodegradabilità, come un anticipo dell’epoca di raccolta e i pretrattamenti della biomassa, ai fini di una maggior resa specifica di CH4.

Pre-trattamenti alcalini a moderata aggressività sono stati applicati su tre substrati quali Arundo (specie poliennale da biomassa), B 133 (ibrido di sorgo annuale da biomassa) e paglia di orzo (sottoprodotto agricolo) per migliorare la produzione specifica di CH4. I pre-trattamenti sono stati condotti a 25 °C per 24 h, con NaOH a tre differenti concentrazioni (0,05; 0,10; 0,15 N), oltre a un testimone non trattato. L’incubazione anaerobica è stata condotta con un carico organico di 4 g SV l-1 a 35 °C per 58 gg. In tutti i pretrattamenti testati è stato osservato un incremento nella produzione specifica di CH4, rispetto al substrato non trattato. Il maggior incremento (30%) è stato ottenuto con NaOH 0,15 N in Arundo. Tali risultati appaiono particolarmente interessanti, dimostrando come un modesto impiego di energia termica per il pre-trattamento si accompagni a significativi incrementi di CH4 prodotto. I pretrattamenti a base di soda non dovrebbero essere, inoltre, difficilmente implementabili nei moderni impianti di biogas.

In this study municipal organic waste (MOW), barley straw (BS) and fibre sorghum (Sorghum bicolor (L.) Moench) B133 hybrid were compared as sources for bioethanol production, through simultaneous saccharification and fermentation (SSF) process. Kluyveromyces marxianus DSM 4906 and Saccharomyces cerevisiae DSM 70449 were employed for fermentation at 45 °C and 37 °C, respectively. Experiments were conducted for 96 hours in 500 mL flasks with a total solid load of 50 g L-1, in anaerobic condition and constant orbital shaking (120 rpm). The analysis of variance of ethanol production showed significant differences among sources, and MOW resulted the most productive one (12.2 g L-1) compared to B133 (5.8 g L-1) and BS (2.5 g L-1). Also the efficiency in the conversion of cellulose to ethanol (CCE) was only significantly influenced by biomass source. BS exhibited the lowest CCE (32.2 %), compared to BS, B133 (67.4%) and MOW (84.3%). The difference in CCE observed for B133 and BS, suggests that the spatial disposition of structural components (cellulose, hemicellulose and lignin), and perhaps also soluble glucose, are major factors in second generation ethanol production.