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The increasing population creates excess pressure on the plantation and production of fruits and vegetables across the world. Consumption demand during the whole year has made production compulsory in the covered production system (greenhouse). Production, harvesting, processing, transporting, and distribution chains of fruit and vegetables have resulted in a huge amount of wastes as an alternative source to produce biofuels. In this study, optimization of two pretreatment processes (NaOH and HCl assisted thermal) was investigated to enhance methane production from fruit and vegetable harvesting wastes (FVHW) that originate from greenhouses. NaOH concentration (0&ndash, 6.5%), HCl concentration (0&ndash, 5%), reaction temperature (60&ndash, 100 &deg, C), solid content (1&ndash, 5%), time of reaction (1&ndash, 5 h), and mixing speed (0&ndash, 500 rpm) were chosen in a wide range of levels to optimize the process in a broad design boundary and to evaluate the positive and negative impacts of independent variables along with their ranges. Increasing NaOH and HCl concentrations resulted in higher COD solubilization but decreased the concentration of soluble sugars that can be converted directly into methane. Thus, the increasing concentrations of NaOH and HCl in the pretreatments have resulted in low methane production. The most important independent variables impacting COD and sugar solubilization were found to be chemical concentration (as NaOH and HCl), solid content and reaction temperature for the optimization of pretreatment processes. The high amount of methane productions in the range of 222&ndash, 365 mL CH4 gVS&minus, 1 was obtained by the simple thermal application without using chemical agents as NaOH or HCl. Maximum enhancement of methane production was 47&ndash, 68% compared to raw FVHW when 5% solid content, 1-hour reaction time and 60&ndash, C reaction temperature were applied in pretreatments.

The aim of this study was to investigate thermophilic (55 °C) aerobic digestion (TAD) as pre- and inter-stage treatment of sludge anaerobic digestion and to analyse the change in organic matter accessibility and complexity. Pre-treatment decreased methane yield (up to −70%), due to oxidation losses whereas inter-stage treatment slightly improved overall methane yield (+2.6%) and total COD removal (+5%) compared to control. Anaerobic degradability and COD removal in the second anaerobic stage significantly increased, by 13–40%. Organic matter fractionation showed that TAD led to an increase in sludge organic matter accessibility in all cases. Organic matter complexity, measured by fluorimetry, increased after TAD pre-treatment whereas it remained constant after inter-stage treatment. TAD was shown to be more efficient if applied to a more recalcitrant substrate and should thus be used as inter-stage treatment to avoid decreasing methane production.

By incorporating the dynamical aspects of the respiration chamber data, the model allows further information on an individual animal’s rumen microbiome to be extracted. This represents a potential stepping stone to relating rumen microbial genes to parameters controlling the dynamics of rumen fermentation and hence methane production.

Our objective was to evaluate the effects of Acacia mearnsii bark extract (PAB) on methane (CH4) production in sheep infected with Trichostrongylus colubriformis and Haemonchus contortus. Twenty 10 month-old Santa Inês lambs were used in a 50-day trial. Four treatment groups were formed: two control groups uninfected, one without PAB (C-) (n=4) and one with PAB (C+) (n=4); and two infected groups, one without PAB (I-) (n=6) and another receiving PAB (I+) (n= 6). Animals were kept in individual pens for 40 days, and received ad libitum chopped tifton 85 hay (Cynodon spp.) and 210 g/animal/day of concentrate (PAB supplementation: 15 g/animal/day – in concentrate). Animals were reared indoors to avoid helminthic infections (faecal egg count (FEC) was monthly controlled). At day 0, infected groups were artificially infected with L3 larvae of T. colubriformis (7500)and H. contortus (5000). After 28 days post- infection, establishment of infections was confirmed by FEC: I-: 1150 + 530.1 and I+: 567 + 544.6 eggs/gram of feces. After 40 days of trial (during which other parameters were evaluated - data not shown), CH4 emissions in chambers were measured and variance analysis (proc GLM, SAS®) showed no PAB effects on methanogenesis (p > 0.05), however, both infected groups had higher CH4 emissions than the control groups: C-: 16.7 + 10.91; C+:23.7 + 12.88; I-: 43.1 + 6.37; I+: 40.6 + 6.02 (g CH4/kg dry matter intake) (p < 0.05). The methanogenic effect of parasitc infections should be explored in studies addressing sustainability of animal production.

A quantitative structure activity relationship (QSAR) between relative abundance values and digester methane production rate was developed. For this, 50 triplicate anaerobic digester sets (150 total digesters) were each seeded with different methanogenic biomass samples obtained from full-scale, engineered methanogenic systems. Although all digesters were operated identically for at least 5 solids retention times (SRTs), their quasi steady-state function varied significantly, with average daily methane production rates ranging from 0.09 ± 0.004 to 1 ± 0.05 L-CH4/LR-day (LR = Liter of reactor volume) (average ± standard deviation). Digester microbial community structure was analyzed using more than 4.1 million partial 16S rRNA gene sequences of Archaea and Bacteria. At the genus level, 1300 operational taxonomic units (OTUs) were observed across all digesters, whereas each digester contained 158 ± 27 OTUs. Digester function did not correlate with typical biomass descriptors such as volatile suspended solids (VSS) concentration, microbial richness, diversity or evenness indices. However, methane production rate did correlate notably with relative abundances of one Archaeal and nine Bacterial OTUs. These relative abundances were used as descriptors to develop a multiple linear regression (MLR) QSAR equation to predict methane production rates solely based on microbial community data. The model explained over 66% of the variance in the experimental data set based on 149 anaerobic digesters with a standard error of 0.12 L-CH4/LR-day. This study provides a framework to relate engineered process function and microbial community composition which can be further expanded to include different feed stocks and digester operating conditions in order to develop a more robust QSAR model.

International audience; Substrates for anaerobic digestion are composed of heterogeneous and complex organic matter. General parameters of the organic matter can be used to describe its composition such as sugar, protein and lipid contents, Chemical Oxygen Demand (COD), Biochemical Methane Potential (BMP) and kinetic of methane production. These parameters are required for the monitoring of digesters but their characterization are time consuming and expensive; thus, these parameters are rarely assessed all together. We investigated the existing correlations between COD, methane yield, biodegradability, kinetic of methane production and sugar, protein and lipid contents on 222 samples using principal component analysis and Pearson’s correlation coefficient. Our work aims at providing a support to operators when only a partial characterization of the substrates is available. Positive correlation between methane yield and methane production kinetic but also unexpected independence of COD and BMP are shown. Sugars, proteins and lipids modulated differently the anaerobic digestion performances. Sugars are correlated with readily biodegradable organic matter while proteins are slightly anti-correlated with biodegradability. Lipids were correlated with high methane yield but slow methane productions. Finally, partial least square regression points towards more descriptive organic matter characterization that could be used to predict the kinetic of methane production.

Nowadays, about 1.3 billion tons of food is wasted every year. This number, which is expected to increase greatly in the next decades, evidences the urgent need of improving the efficiency of the current food processing systems, supply chains, prevention policies and food waste (FW) disposal alternatives. Indeed, new FW treatment methods must be developed. At present, most of the FW is disposed in landfills or incinerated, whereas these organic matters could participate further in the recycling of resources. Anaerobic processes appear as a wellstablished alternative that allows, not only an effective waste treatment, but also its valorization by the generation of different added value products (i.e. methane, hydrogen, volatile fatty acids, lactic acid, ethanol, soil improver…). Due to the high total solids (TS) content of FW (around 20 %), it is possible to treat it by dry anaerobic digestion (AD) (>20 % TS), a process with advantages when compared to traditional wet digestion (i.e. lower water requirement, lower digestate production and smaller reactor volume) (Karthikeyan and Visvanathan, 2013). In this study, the influence of the initial FW charge on the performance of a batch dry anaerobic codigestion system using FW and cardboard (CB) as substrates was evaluated. To do that, the FW charge was modified by varying three independent parameters: the initial TS content (20-35 %), the substrate to inoculum ratio (S/X) (0.25-4 g VS·g VS-1) and the FW:CB proportion in the substrate (50:50-80:20 g TS·g TS-1). The experiments were carried out under mesophilic conditions (35 °C) and 13 different conditions were defined. The biogas production and composition were analyzed throughout an experimental period of 98 days and the concentrations of soluble metabolites and main ions were measured when the operation finished. The obtained results showed that the S/X ratio is a crucial parameter, determining the working pH of the system and therefore the final products. In fact, only the reactors working at an S/X ratio of 0.25 (lowest FW charges) produced methane. The other conditions lead to accumulation of metabolites (volatile fatty acids-VFAs, lactate…) and hydrogen production. In addition, greater substrate conversions were achieved at low initial charges of FW. Moreover, the hydrogen yields were found to decrease when increasing the initial charge. This occurred because at high loadings, the acidification effect was more intense, inducing the accumulation of VFAs and lactic acid. This affected significantly the pH, decreasing the hydrogen and VFAs yields. This research suggested that dry anaerobic treatment of FW & CB could be an interesting technology for the production of different added value compounds, such as methane, hydrogen, VFAs and lactic acid. The generation of one product or another was found to be dependent of the initial charge of substrate. While low charged conditions lead to methane production and an efficient waste stabilization, high charged reactors produced hydrogen, VFAs and lactate. In those last cases, the waste stabilization was incomplete, with more than the 50% of the input COD remaining in the digestate. However, the high yields of products suggested that this option could be interesting for a first reactor in a potential 2-stage system with a final stage for waste stabilization by methane production.

Nine anaerobic digesters, each seeded with biomass from a different source, were operated identically and their quasi steady state function was compared. Subsequently, digesters were bioaugmented with a methanogenic culture previously shown to increase specific methanogenic activity. Before bioaugmentation, different seed biomass resulted in different quasi steady state function, with digesters clustering into three groups distinguished by methane (CH4) production. Digesters with similar functional performance contained similar archaeal communities based on clustering of Illumina sequence data of the V4V5 region of the 16S rRNA gene. High CH4 production correlated with neutral pH and high Methanosarcina abundance, whereas low CH4 production correlated to low pH as well as high Methanobacterium and DHVEG 6 family abundance. After bioaugmentation, CH4 production from the high CH4-producing digesters transiently increased by 11 ± 3% relative to non-bioaugmented controls (p

A meta-analysis was conducted to compare effects of C4 and C3 grasses as well as warm and cold climate legumes on CH 4 production of ruminants. For this purpose, a database was built using 22 in vivo studies containing 112 observations with 58 C3 grasses, 28 C4 grasses, 26 cold legumes and 12 warm legumes. Neutral detergent fibre (NDF), crude protein (CP) and total tract organic matter (OM) digestibility ranged from 415 to 753 g/kg DM versus 361 to 754 g/kg DM, from 24 to 254 g/kg DM versus 44 to 314 g/kg DM and from 0.51 to 0.71 versus 0.56 to 0.83 for C4 and C3 grasses, respectively. The NDF, CP and total tract OM digestibility ranged from 441 to 690 g/kg DM versus 252 to 684 g/kg DM, from 93 to 236 g/kg DM versus 141 to 269 g/kg DM and from 0.42 to 0.57 versus 0.38 to 0.79 for warm and cold legumes, respectively. Relationships between CH 4 production and forage characteristics were analysed by analysis of covariance. For grasses, the main factors tested as fixed effects were NDF and CP content of the diet, total tract OM digestibility, intake, animal species, forage family and random trial effect. For legumes, tannin level was included in the model. Results indicate that ruminants fed C4 grass produced 17% more CH 4 as L/kg OM intake (P 4 (P 4 production between C3 grasses and cold legumes. Use of some legumes in warm climates could be a strategy to reduce CH 4 emissions by ruminants. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Urban sludge produced on wastewater treatment plants are often contaminated by organic pollutants such as polycyclic aromatic hydrocarbons (PAH). Their removal under methanogenic conditions was already reported, but the factors influencing this removal remain unclear. Here, we determined the influence of microbial communities on PAH removal under controlled physico-chemical conditions. Twelve mesophilic anaerobic digesters were inoculated with three microbial communities extracted from ecosystems with contrasting pollution histories: a PAH contaminated soil, a PCB contaminated sediment and a low contaminated anaerobic sludge. These anaerobic digesters were operated during 100 days in continuous mode. A sterilised activated sludge, spiked with 13 PAH at concentrations usually encountered in full-scale wastewater treatment plants, was used as substrate. The dry matter and volatile solid degradation, the biogas production rate and composition, the volatile fatty acids (VFA) production and the PAH removals were monitored. Bacterial and archaeal communities were compared in abundance (qPCR), in community structure (SSCP fingerprinting) and in dominant microbial species (454-pyrosequencing). The bioreactors inoculated with the community extracted from low contaminated anaerobic sludge showed the greater methane production. The PAH removals ranged from 10 % to 30 %, respectively, for high and low molecular weight PAH, whatever the inoculums tested, and were highly correlated with the dry matter and volatile solid removals. The microbial community structure and diversity differed with the inoculum source; this difference was maintained after the 100 days of digestion. However, the PAH removal was not correlated to these diverse structures and diversities. We hence obtained three functional stable consortia with two contrasted metabolic activities, and three different pictures of microbial diversity, but similar PAH and matter removals. These results confirm that PAH removal depends on the molecule type and on the solid matter removal. But, as PAH elimination is similar whether the solid substrate is degraded into VFA or into methane, it seems that the fermentative communities are responsible for their elimination.

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International audience

The purpose of this work was to investigate the effects of the addition of by-products from the refining of vegetable oil on the behavior of co-digestion reactors treating a mixture of grass, cow dung and fruit and vegetable wastes. Three by-products were used: one soapstocks, one used winterisation earth and one skimming of aeroflotation of the effluents. Three 15-L reactors were run in parallel and fed 5 times a week. In a first phase of 4 weeks, the three reactors were fed with the co-digestion substrates alone (grass, cow dung and fruit and vegetable wastes) at an OLR of 1.5 g VS/kg.d. Then, one of the three by-products from the refining of oil was added to the feed of each reactor generating a 33% increase in the OLR (2 gVS/kg.d). The results show that the addition of by-products from the refining of oil is an efficient way to increase the methane production of co-digestion reactors thanks to their high methane yield (0.77 – 0.80 l CH4/gVS). Indeed, in this work, it was possible to increase by 60 to 65 % the methane production of the reactors by a 33% increase in the OLR thanks to the addition of the by-products.

The conversion of sunflower stalks into biomethane by batch mesophilic anaerobic digestion was investigated in this work. Methane potential of sunflower stalks (192 ± 2 mLCH4/g VS) was increased by several thermo-chemical pretreatments: NaOH, H2O2, Ca(OH)2, HCl and FeCl3. The highest production (259 ± 6mLCH4/ g VS) corresponding to a 31.4% increase was reached for the treatment at 55°C with 4% NaOH during 24h. More than 90 % of hemicelluloses were removed by applying acidic pretreatment (10% FeCl3 or 4% HCl) at 170 °C. Oxidative and alkaline pretreatment (4% NaOH, 4% H2O2, 4% Ca(OH)2) at 55°C were found to be more efficient to dissolve lignin than acidic pretreatment with a lignin removal around 22%.A negative linear correlation (R2 = 0.895) was found between the lignin content of raw and pretreated sunflower stalks and the methane potential.

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International audience; This experiment studied the effect of 3 different physical forms of linseed fatty acids (FA) on cow dairy performance, milk FA secretion and composition, and their relationship with methane output. Eight multiparous, lactating Holstein cows were assigned to 1 of 4 dietary treatments in a replicated 4 x 4 Latin square design: a control diet (C) based on corn silage (59%) and concentrate (35%), and the same diet supplemented with whole crude linseed (CLS), extruded linseed (ELS), or linseed oil (LSO) at the same FA level (5% of dietary dry matter). Each experimental period lasted 4 wk. Dry matter intake was not modified with CLS but was lowered with both ELS and LSO (-3.1 and -5.1 kg/d, respectively) compared with C. Milk yield and milk fat content were similar for LSO and ELS but lower than for C and CLS (19.9 vs. 22.3 kg/d and 33.8 vs. 43.2 g/kg, on average, respectively). Compared with diet C, CLS changed the concentrations of a small number of FA; the main effects were decreases in 8:0 to 16:0 and increases in 18:0 and cis-9 18:1. Compared with diet C (and CLS in most cases), LSO appreciably changed the concentrations of almost all the FA measured; the main effects were decreases in FA from 4:0 to 16:0 and increases in 18:0, trans-11 16:1, all cis and trans 18:1 (except trans-11 18:1), and nonconjugated trans 18:2 isomers. The effect of ELS was either intermediate between those of CLS and LSO or similar to LSO with a few significant exceptions: increases in 17:0 iso; 18:3n-3; trans-11 18:1; cis-9, trans-11 conjugated linoleic acid; and trans-11, trans-13 conjugated linoleic acid and a smaller increase in cis-9 18:1. The most positive correlations (r = 0.87 to 0.91) between milk FA concentrations and methane output were observed for saturated FA from 6:0 to 16:0 and for 10:1, and the most negative correlations (r = -0.86 to -0.90) were observed for trans-16+cis-14 18:1; cis-9, trans-13 18:2; trans-11 16:1; and trans-12 18:1. Thus, milk FA profile can be considered a potential indicator of in vivo methane output in ruminants.

Session 6: Feed conversion efficiency towards productivity and reduction of excreta; Multiplatform milk metabolomics highlights potential biomarkers related to methane emissions in dairy cows. 10. International Symposium on the Nutrition of Herbivores (ISNH10)