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A study was undertaken to compare the rumen microbial community composition, methane yield, rumen fermentation, and CAZyme profiles between cattle and buffaloes. The primary aim of this study was to ascertain the impact of the host species on the above when diet and environmental factors are fixed. A total of 43 phyla, 200 orders, 458 families, and 1722 microbial genera were identified in the study. Bacteroidetes was the most prominent bacterial phylum and constituted >1/3rd of the ruminal microbiota; however, their abundances were comparable between cattle and buffaloes. Firmicutes were the second most abundant bacteria, found to be negatively correlated with the Bacteroidetes. The abundances of Firmicutes as well as the F/B ratio were not different between the two host species. In this study, archaea affiliated with the nine phyla were identified, with Euryarchaeota being the most prominent. Like bacterial phyla, the abundances of Euryarchaeota methanogens were also similar between the cattle and buffaloes. At the order level, Methanobacteriales dominated the archaea. Methanogens from the Methanosarcinales , Methanococcales , Methanomicrobiales , and Methanomassiliicoccales groups were also identified, but at a lower frequency. Methanobrevibacter was the most prevalent genus of methanogens, accounting for approximately three percent of the rumen metagenome. However, their distribution was not different between the two host species. CAZymes affiliated with five classes, namely CBM, CE, GH, GT, and PL, were identified in the metagenome, where the GH class was the most abundant and constituted ~70% of the total CAZymes. The protozoal numbers, including Entodiniomorphs and Holotrichs , were also comparable between the cattle and buffaloes. Results from the study did not reveal any significant difference in feed intake, nutrient digestibility, and rumen fermentation between cattle and buffaloes fed on the same diet. As methane yield due to the similar diet composition, feed ingredients, rumen fermentation, and microbiota composition did not vary, these results indicate that the microbiota community structure and methane emissions are under the direct influence of the diet and environment, and the host species may play only a minor role until the productivity does not vary. More studies are warranted to investigate the effect of different diets and environments on microbiota composition and methane yield. Further, the impact of variable productivity on both the cattle and buffaloes when the diet and environmental factors are fixed needs to be ascertained.

In this study, semi-continuous anaerobic digestion of lignin-rich steam-exploded Ludwigia grandiflora (Lignin = 25.22% ± 4.6% total solids) was performed to understand better the effect of steam explosion on the substrate solubilisation and inhibitors formation during the process. Steam explosion pretreatment was performed at 180 °C for 30 min at a severity factor of 3.8 to enhance the biogas yield of the lignocellulosic biomass. The semi-continuous anaerobic digestion was performed in a continuously stirred tank reactor for 98 days at an initial hydraulic retention time of 30 days and an organic loading rate of 0.9 g-VS L−1 day−1. The performed steam explosion pretreatment caused biomass solubilisation, resulting in enhanced biogas production during the process. During the anaerobic digestion process, the average biogas yield was 265 mL g-VS−1, and the pH throughout the operation was in the optimum range of 6.5–8.2. Due to fluctuations in the biogas yield, the hydraulic retention time and organic loading rate were changed on day 42 (50 days and 0.5 g-VS L−1 day−1) and on day 49 (40 days and 0.7 g-VS L−1 day−1), and 1 M of NaOH was added to the liquid fraction of the steam-exploded L. grandiflora during the latter part of the operation to maintain the stability in the reactor. Therefore, the steam explosion pretreatment helped in the degradation of L. grandiflora by breaking the lignocellulose structure. In addition, changes in the operating conditions of the anaerobic digestion led to an increase in the biogas production towards the end of the process, leading to the stability in the CSTR.

The aim of this study was to measure methane emissions (CH4) and herbage intake, and, on the basis of these results, obtain the methane yield (MY, methane yield as g CH4/kg dry matter intake (DMI) and Ym, methane yield as a percentage of Gross Energy intake), from beef cows grazing on native grasslands. We used forty pregnant heifers, with two treatments of herbage allowance (HA) adjusted seasonally (8 and 5 kg dry matter (DM)/kg cattle live weight (LW), on average), during autumn, winter and spring. Methane emissions (207 g CH4/d), organic matter intake (OMI, 7.7 kg organic matter (OM)/d), MY (23.6 g CH4/kg DMI) and Ym (7.4%), were similar between treatments. On the other hand, all variables had a marked increase in spring (10.8 kg OM/d and 312 g CH4/d), except for Ym. The methane emission factor from Intergovernmental Panel on Climate Change (IPCC) Tier 2 estimated with these results was 78 kg CH4/head/year. The results show that methane emissions and intake were influenced by the season, but not by the HA analyzed in this study. This information for cow–calf systems in native grasslands in Uruguay can be used in National greenhouse gases (GHG) inventories, representing a relevant contribution to global GHG inventories.

Increasing total solids in anaerobic digestion can reduce the methane yield by highly complex bio-physical–chemical mechanisms. Therefore, understanding those mechanisms and their main drivers becomes crucial to optimize this waste treatment biotechnology. In this study, seven batch experiments were conducted to investigate the effects of increasing the initial total solids in high-solids anaerobic digestion of the organic fraction of municipal solid waste. With inoculum-to-substrate ratio = 1.5 g VS/g VS and maximum total solids ≤ 19.6%, mono-digestion of the organic fraction of municipal solid waste showed a methane yield = 174–236 NmL CH4/g VS. With inoculum-to-substrate ratio ≤ 1.0 g VS/g VS and maximum total solids ≥ 24.0%, mono-digestion experiments acidified. Co-digestion of the organic fraction of municipal solid waste and beech sawdust permitted to reduce the inoculum-to-substrate ratio to 0.16 g VS/g VS while increasing total solids up to 30.2%, though achieving a lower methane yield (117–156 NmL CH4/g VS). At each inoculum-to-substrate ratio, higher total solids corresponded to higher ammonia and volatile fatty acid accumulation. Thus, a 40% lower methane yield for mono-digestion was observed at a NH3 concentration ≥ 2.3 g N–NH3/kg reactor content and total solids = 15.0%. Meanwhile, co-digestion lowered the nitrogen content, being the risk of acidification exacerbated only at total solids ≥ 20.0%. Therefore, the biodegradability of the substrate, as well as the operational total solids and inoculum-to-substrate ratio, are closely interrelated parameters determining the success of methanogenesis, but also the risk of ammonia inhibition in high-solids anaerobic digestion. [ABSTRACT FROM AUTHOR]

This paper focuses on the properties and mechanism of dissolved gases permeate membrane and energy recovery efficiency in the anaerobic forward osmosis membrane bioreactor under different membranes types (CTA-ES and CTA-NW), membrane orientations, temperatures (25 °C and 35 °C) and influent COD concentrations (3000 mg/L,6000 mg/L and 9000 mg/L). CTA membrane allowed the permeation of dissolved H 2 , and the concentration of dissolved H 2 in the draw side (between 2.4 mg/L and 4.2 mg/L) was higher than the feed side (between 1 mg/L and 3.4 mg/L). This was beneficial to the anaerobic digestion because the partial pressure of H 2 in the reactor was reduced. A small amount of dissolved CO 2 (around 7 mg/L in draw side while between 56 mg/L and 256 mg/L in feed side) was allowed to pass through the CTA membrane. CTA membrane nearly 100% blocks the permeation of dissolved CH 4 at different operation conditions in this paper. The highest methane yield was 0.256 L CH 4 /g COD at 35 °C with the influent COD was 6000 mg/L. This showed that AnOMBR could solve the problem of effluent containing dissolved methane in conventional anaerobic treatment, and had great potential in energy recovery. Image 1 [ABSTRACT FROM AUTHOR]

There are few studies on the use of wheat husk for anaerobic digestion until now. In this study, the BMP (biochemical methane potential) of wheat husk without pretreatment and with liquid digestate (LD) soaking pretreatment was investigated. It was demonstrated that wheat husk could be potentially used as a single feeding substrate for anaerobic digestion with a methane yield of 68 mL/g VS and this yield could be enhanced to a maximum of 130.0 mL/g VS using LD soaking pretreatment, which increased the methane production by 91%. Although the particle size (8, 5, 2 mm) and soaking pretreatment time (1, 3, 5 d) affected the biogas production, the influence of particle size was negligible when the pretreatment time was 5 days. Further analysis of the microbial community showed that the LD soaking pretreatment did not change the predominant microbial communities in the digestion. Therefore, LD pretreatment was effective in enhancing the performance of wheat husk anaerobic digestion. • Biochemical methane potential of wheat husk was studied for the first time. • Liquid digestate was used for the wheat husk pretreatment. • Influence of particle size was negligible when pretreatment time increased. • Microbial community during the anaerobic digestion was studied. [ABSTRACT FROM AUTHOR]

The sugar cane bagasse constitutes an abundant lignocellulosic agro-industrial residue in Cuban sugar industry. However, its complex structure partially limits biodegradation, for that reason it is necessary to apply a pretreatment, being the alkaline the most effective for biomasses with a high lignin content. This work objective is to evaluate the effect of alkaline pretreatment in cane bagasse delignification, and its anaerobic biodegradability with respect to without pretreatment bagasse. Two alkalis (NaOH and KOH) with two concentration levels (0.5 and 1% w/v), and two contact times (1 and 3 h), were studied at room temperature. Results were evaluated in terms of % delignification, methane yield and process kinetics according to a first order model. Maximum lignin reduction (36.5%) and methane yield (192 mLCH4/g VS) were obtained with NaOH (0.5% -3h), achieving a 94.6% increase in methane yield respect to without pretreating bagasse. Kinetic study confirmed that kinetic parameters are improved compared to without pretreatment bagasse, with this variant. [ABSTRACT FROM AUTHOR]

• Mono-anaerobic digestion of pig manure in leach bed reactors is performed. • Biogas slurry inoculation occurs during the pig manure digestion in a leach bed. • Reflux significantly improves the efficiency of manure anaerobic digestion. • Inorganic filtration medium is used for the mono-anaerobic digestion of pig manure. • The emission of odour and yield of biogas slurry are significantly reduced. The effect of reflux ratio on the anaerobic mono-digestion of pig manure (PM) in leach beds coupled with continuous stirred tank reactors (CSTRs) has been studied in this work, and contents of volatile fatty acids (VFAs) and biogas yields were determined for three groups of leach bed reactor (LBR) – CSTR systems. The obtained results indicated that the reflux of biogas slurry increased both the pH of the acid-producing phase and acetic acid yield and repeatedly degraded the refractory organic matter in the biogas slurry. The larger reflux ratio increased the inoculation volume and substantially enhanced the mass transfer process. The maximum values of the biogas and methane yields equal to 259.49 and 167.44 mL/g volatile solids, respectively, were achieved at a reflux ratio of 100%. Moreover, the weight of the PM leachate residue was reduced by 94.14%, and the total nutrient content (N + P 2 O 5 + K 2 O) was relatively high (1.48%), which was suitable for vegetable seedling substrates. In conclusion, during the treatment of PM in LBR–CSTRs, the solid phase remains on the leach bed, and the leachate is supplied to a biogas tank, which effectively increases its stability of operation. [ABSTRACT FROM AUTHOR]

Agricultural wastes have severely polluted the environment and obstruct the sustainable development of modern agriculture due to a lack of effective disposal methods. The present study conducted batch experiments in which rice straw (RS) and pig manure (PM) mixtures were pretreated with a previously developed cellulolytic microflora prior to their mesophilic anaerobic co-digestion. Optimal anaerobic digestion (AD) performance of RS and PM could be achieved after biological pretreatment with this specific cellulolytic microflora for 30 h. Under this condition, the filter paper cellulase (FPase) and carboxymethyl cellulase (CMCase) activities in RS and PM degradation broths reached maxima of 2.25 and 2.58 IU/mL, respectively, and the weight loss ratio reached 39.4%. After the subsequent AD process, the methane yield of RS and PM mixtures reached 263.69 mL/g-VS, which was 47.6% higher than that of the control group (CK) without biological pretreatment (178.66 mL/g-VS). In addition, the daily methane production peak duration (3 day) of the anaerobic co-digestion of RS and PM after 30 h of biological pretreatment with this microflora was longer than that of CK (1 day). The above results further indicated that pretreatment of RS and PM mixtures with microflora greatly enhanced the methane yield and prolonged the peak period of methane production in the subsequent anaerobic co-digestion. [ABSTRACT FROM AUTHOR]

The study evaluated the residual effect of the known enteric methane inhibitor 3-nitrooxypropanol (3NOP) on anaerobic digestion of cattle feces (feces) in a CH4 potential batch test and two consecutive runs of an anaerobic leach bed reactor at a solids retention time of 40 days. The feces used in this study were collected from beef cattle fed forage- (backgrounding) or grain- (finishing) based diets supplemented with 3NOP in feedlot and metabolism studies. The results showed that CH4 yields were not significantly different from treatments using control feces and feces collected from cattle fed a diet supplemented with 3NOP in both CH4 potential and leach bed studies. Spiking feces with 200 mg 3NOP kg-1 dry matter decreased CH4 production rate by 8.0-18.1% estimated from the Gompertz equation, increased the lag phase time (0.4-3.4 d) in all the treatments, while there was no significant difference in the overall CH4 yield. Results from this study showed that 3NOP can be used as an effective enteric CH4 inhibitor with no residual effect on anaerobic digestion. [ABSTRACT FROM AUTHOR]

The biogas production potential of different mixtures of cow manure (CM) and three-phase olive mill solid waste (3POMSW) at 37°C was evaluated. Results showed that 3POMSW produced more methane yield than CM. In the anaerobic co-digestion (AcoD) methane yield increased with increasing of 3POMSW content, the maximum methane yield was observed at 3POMSW:CM ratio of 3:1. Addition of an enzyme mixture (Celluclast, Pulpzyme HC, Sherazyme, Novozym 342, and Resinase A 2X) to the 1:1 mixture increased the quantity and quality of biogas production and reduced the retention time required to achieve a high rate of biodegradation. Therefore, AcoD with enzymes was an effective way to improve the methane yield of 3POMSW and CM. [ABSTRACT FROM AUTHOR]

Copyright of Algerian Journal of Environmental Science & Technology is the property of Algerian Journal of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Energy from biomass is essential for sustainable agricultural development. The generation of biogas and bio-fertilizer from the anaerobic co-digestion is fundamental in mitigating environmental problems and in the local generation of electricity. In this context, this study examines the technical and economic feasibility of the effects of co-digestion of sweet potato with dairy cattle manure on energy and nutrient recovery using semi-continuous digesters. The use of sweet potato in co-digestion is characterized as an innovation in the technological process of anaerobic digestion, the application of which on small and medium-sized farms is still a challenge in emerging economies. The assay was conducted using different proportions of sweet potato mixed with dairy cattle manure, which produced a linear increase in methane yield with concentrations of 63–65.5% and biogas capable of generating 2376.44 kWh d−1. In addition to the generation of cleaner electrical energy, the co-digestion process produces a bio-fertilizer with a potential production of 26.53 tons/year of N, 20.45 ton/year of P and 23.6 tons/year of K. These results are superior to the mono-digestion process. Regarding the necessity of using sweet potato, this new system of production was evaluated for a model medium-size farm dedicated to dairy production in the countryside of the state of São Paulo in Brazil. The results demonstrate the economic feasibility of the investment in the five analysed scenarios, as the internal rate of return varied between 46.8% and 57% and the payback was achieved in 2–3 years. This research demonstrates that the innovation of using sweet potato as an additional input to the digestion process can increase the sustainability of small and medium-sized dairy farms in a manner consistent with a circular economy. Image 1 • The sweet potato increases the production of biogas in digesters. • Co-digestion from sweet potato produces bio-fertilizer with quality nutrient. • Digesters are economically viable for clean energy generation from biomass. • Using a sweet potato to anaerobic co-digestion increases sustainability of farms. [ABSTRACT FROM AUTHOR]

The present paper deals with the mono-digestion of coffee husk during the operation of batch reactors and semi-continuous stirred tank reactor (S-CSTR) using both pre-treated residual at 3% Ca(OH)2 and without pre-treatment. The semi-continuous operation was carried out in 4 stages at different organic loading rate (OLR, [gVS L-1 d-1]) and hydraulic retention time (HRT, [d]) (OLR:HRT) ratios (0.1:90, 0.2:90, 0.2:45 and 0.2:30). As a result of the pre-treatment, up to 223% of the organic matter solubilisation was obtained. However, pre-treatment did not provide better results in biodegradability, observing a negative trend in methane yield when operating in S-CSTR, due to the accumulation of compounds from the fractionation of the lignin as is the case of polyphenols. The operation was further developed using the residual without pre-treatment. The highest methane yield was obtained at 45:0.2 when using the residual without pre-treatment being with 277 mLCH4 gVS-1, for a methane productivity of 1.1 L L-1 d-1. When implementing the 30:0.2 ratio, a biomass washout was observed in the system, so it is recommended to operate at low OLR and high HRT when treating solid coffee wastes. [ABSTRACT FROM AUTHOR]

• The stimulating effect of antibiotics was stronger under low inoculation ratios. • Modified Gompertz model fit best for HSAD under different inoculation ratios. • Day 5 was the key time point for the stimulating effect occurring. • Methanosarcina growth was key reason for the stimulating effect of antibiotics. To comprehensively understand how antibiotics affect anaerobic digestion, their stimulating effects on methane production cannot be ignored; however, few studies have evaluated these effects. This study investigated the stimulating effects of three typical antibiotics (oxytetracycline, sulfadimethoxine, and norfloxacin) on high solid anaerobic digestion. The results showed that 100 mg/L antibiotics exhibited a strong stimulating effect on CH 4 yield; while other external carbon sources had no obvious effects. The stimulating effect was more obvious under low inoculation ratios, which could improve the system processing capacity of feed sludge. Lower lag phases were given by the modified Gompertz model when stimulating effects occurred. The variations of physicochemical parameters and microbial Venn maps both showed that day 5 was a critical point for digestion time. The relative abundance of Methanosarcina was enhanced when the stimulating effect occurred, whereas Methanoculleus decreased. Different microbial characteristics were obtained for different samples from the heat maps. [ABSTRACT FROM AUTHOR]

Wastewater management is the biggest challenge in recent years concerning ecological considerations. The increasing quantity of organic wastes and waste waters produced from plants and manufacturing processes has caused the designing and buildings of numerous bioreactors and digester to yield biogas. Anaerobic digestion is a method that alters organic matter into gassy mix mostly composed of methane and carbon dioxide through an intensive act of an adjacent group of microbes. The biodegradability of the waste (with its moisture and volatile solids content), the presence of toxins, the presence of nutrients, the presence of fibre contents, as well as the variability and particle size of the feedstock are some of the characteristics that may exhibit a profound effect. This Study has verified that different types of substrate used in the batch reactor are capable of good methane generation by using a suitable organic loading rate. This study recommends the procedure of kinetics in combination with the investigation statistics, e.g., Hydraulic Retention Time (HRT), Organic Loading Rate (OLR), methane yield, etc. when testing and comparing substrate. Here substrates used are food waste and rice. The food waste selected as a heterogeneous substrate. Also, the cooked rice was selected as a standard substrate due to its homogeneity as well as uniform particle size. The study undertaken involves characterization of wastewater, a study of different OLRs in batch reactors to analyse methane generation. It also checks the effect of substrate heterogeneity and particle size to produce the methane in a batch reactor. The findings in this section not only highlight the possibility of varied tolerance to substrate loading and their effect on methane yield for both substrates. Here the food waste had a methane generation of 0.190 L CH4 g-1 VS in average and for rice 0.210 L CH4 g-1 VS in average, both at 75 % OLR maximum loading. The results showed that rice gave no more methane reproducible result than food waste. [ABSTRACT FROM AUTHOR]

In this study a fractionation procedure was developed and applied to evaluate the potential of some organic wastes (two cattle manures and two catch crops, fresh and after ensiling) for anaerobic digestion. This procedure was based on water extraction of the raw sample, which enabled the evaluation of the contributions of water-soluble and particulate phases to the investigated properties. Biomethane potential (BMP) and chemical oxygen demand (COD) were determined and used to assess the anaerobic biodegradability of raw materials. Analysis of structural carbohydrates, total Kjeldahl nitrogen, water-soluble carbohydrates, volatile fatty acids and pH were also included to explain the main phenomena involved in methane production from the tested biomass. Results show that the origin and the preparation mode had a significant impact on BMP distribution. Based on a COD balance, the biodegradability of the various feedstocks ranged from 45% to 75%. Biodegradability of fresh materials was negatively correlated with the sum of structural carbohydrates and lignin content. Among the feedstock used, the water-soluble phase represented 8–69% of the total COD and 7–46% to the total BMP. Solubilization of organic matter during ensiling was due to the production and accumulation of organic acids from particulate carbohydrates and organic nitrogen. This procedure detects kinetic and biodegradability differences among biomass and thus it can be useful for the design of anaerobic digestion plants. Furthermore, it can be applied to evaluate the efficiency of biomass pretreatments. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Anaerobic co-digestion has been extensively applied in treating residual sludge (RS) and kitchen waste (KW). However, some problems still occur in co-digestive system. This study tries to add green waste (GW) as co-substrate into RS/KW co-digestive system to improve methane production and system stability. The results showed that K4 group (RS:KW:GW = 2:1:0.5, based on VS addition, similarly hereinafter) presented the highest specific methane yield (SMY) of 303.4 mL/g VS, as well as the highest acetic acid (HAc) concentration at the primary stage. An appropriate amount of GW addition into co-substrate mixture was conducive to guaranty continuous degradation and conversion of the organics, and it could also improve the stability of the digestive system and optimize volatile fatty acids (VFAs) composition structure. Buswell formula was used and showed that the highest biodegradability index (BI) was obtained in K4 (97.0%) and K5 (98.2%). Besides, the fitting results of kinetic models were used to analyze methane production and hydrolytic process. The enzymes activity and microbial diversity results of K4 group can also verify the results above. Unlabelled Image • Methane yields were enhanced by adding GW in anaerobic digesters. • Hydrolytic rate of substrates decreased with the addition of GW in system. • Addition of GW was conductive to maintain systems stability. • Moderate GW addition was beneficial to increase the biodegradability index of AD. • GW addition was helpful to balance the activities of acidogens and methanogens. [ABSTRACT FROM AUTHOR]

Abstract The anaerobic co-digestion of spent coffee grounds (SCG) and Ulva biomass, which are problematic wastes and unsuitable for mono-digestion, with food waste (FW) was investigated to widen the scope of feedstocks for biogas production. The effect of the feedstock mixing ratio on the methane yield and synergistic effect of co-digestion was analyzed by response surface analysis. The models for the methane yield and synergistic effect indicated different response patterns and predicted the maximum responses at different mixing ratios. As maximizing the conversion of individual feedstocks to methane is the primary focus in this study, the mixing ratio required for maximizing the synergy index is perceived to be more desirable than that for maximizing methane yield of the mixture. The experimental and modeling results demonstrated that FW, SCG, and Ulva biomass can be effectively co-digested with little antagonistic effect, regardless of their mixing ratio, and a synergistic effect in most cases. It is expected that co-digestion could be flexibly applied when managing the waste feedstocks to enhance their energy recovery potential. The findings of this study can help promote the valorization of underused waste feedstocks through co-digestion and increase the deployment of renewable energy. Highlights • Anaerobic co-digestion of FW, SCG, and Ulva at different mixing ratios was studied. • Co-digestion effect on biogas production was assessed by response surface analysis. • Effects on the methane yield and synergistic effect of co-digestion were analyzed. • Co-digestion exerts additive/synergistic effects regardless of the mixing ratio. • Synergy in co-digestion of waste feedstocks was modeled by RSA for the first time. [ABSTRACT FROM AUTHOR]

Highlights • Four sorghum cultivars × five harvest times studied for CH 4 production in Pakistan. • Late harvest, 48% increase in biomass yield and 17% decrease in specific CH 4 yield. • Cultivar differences in morphology, yield and composition reflecting on CH 4 yield. • Cultivar behaviour across harvests fitted through functions describing time trends. • Favourable prospects for sorghum as bio-methane feedstock in warm dry world areas. Abstract Methane from agricultural biomass contributes to achieving self-reliance and sustainability in alternative energy sources. In this framework, a two-year experiment was set up in Punjab, Pakistan, combining four cultivars (CV) of biomass sorghum with five harvest times (HT) (from 60 to 120 days after sowing) (DAS). HT and CV, both alone and together strongly influenced morphological, compositional and yield traits. Dual purpose (grain and biomass) CV (Jawar-2011 and JS-263) attained higher dry biomass yield (DBY) than fibre CV (Hagari and JS-2002) (+22%), possibly due to a stronger sink for assimilates at late growth stages. Delayed harvest (120 vs. 60 DAS) determined the largest differences in all traits: increase in DBY (+48% DBY), hemi-cellulose (+80%), cellulose (+85%) and lignin (+41%), and concurrent decrease in protein (−22%) and ash (−28%). These compositional changes indicate a strengthening in plant structure with advancing maturity that negatively reflected on specific methane yield (SMY) (−17%). However, average SMY obtained with sorghum in the warm dry conditions of Pakistan (290 l N kg−1 VS) is consistent with data observed at higher latitudes under temperate climate. The significant HT × CV interactions for DBY, SMY and their product, methane yield per hectare, were fitted by means of functions describing CV trends in time. Based on this, suitable combinations of HT and CV can be envisaged to balance methane yield and bio-degradability over a reasonable harvest window. On concluding, data obtained in this experiment disclose favourable prospects for sorghum as bio-methane feedstock in warm dry areas of the world. [ABSTRACT FROM AUTHOR]

Hydraulic retention time (HRT) determination in the anaerobic digestion process is an important factor for reactor design. This study aims to investigate the optimal HRT determination method for beef manure and sawdust mixture in the anaerobic digestion (AD). The Piecewise linear regression (PLR) analysis method was applied to compare the HRT with MGTP95 determined by the Modified Gompertz model analysis, cumulative methane yield (Cum.CH4), cumulative biomass removal (Cum.BMR) and biodegraded volatile solids (PLTBVS). Lab-scale (6 cases of lab-scale in the anaerobic digestion) experiments were performed and analyzed by Modified Gompertz model and Piecewise linear regression analysis. The parameters selected for Piecewise linear regression analysis: Cumulative methane yield (PLTCUM.CH4), cumulative biomass removal (PLTCUM.BMR), biodegradable volatile solids (PLTBVS) and time to produce 95% of methane yield potential from Modified Gompertz model (MGTP95). The HRT determined from PLTCum.CH4 varied in between 26.4~34.9 days, and which were 0.4~3.9 days, 8.3~16.0 days, and 9.4~22.2 days shorter than PLTCum.BMR, MGTP95,  and PLTBVS, respectively. The daily maximum methane yield rate in the HRT from PLTCum.CH4 showing the highest daily methane yields rate which was less than 2.1%. Therefore, reactor utilization rate and organic loading rate for PLTCum. BMR, MGTP95, and PLTBVS were 94.4~99.4%, 78.0~84.4%, and 70.9~83.9%, respectively, lower than PLTCum.CH4. Conclusively, the HRT from PLTCum.CH4 is the most appropriate method to maximize the organic loading rate relative to other determination methods. [ABSTRACT FROM AUTHOR]

Currently, South Africa is experiencing electricity blackouts as result of an energy shortage. Biogas can be a solution to South Africa's energy needs, especially in the rural areas of the Eastern Cape province that have plenty of biogas substrates from cattle, donkeys, goats, sheep and chicken. The purpose of this paper is to design and construct a 1 m3 family biogas digester and model its performance using donkey dung as a biogas substrate. The installation of this type digester in rural communities of South Africa has economic, social and environmental advantages. The digestate from the digester is a valuable soil fertilizer, rich in nitrogen, phosphorus, potassium and micronutrients, which can be applied on soils. The mathematical model equation developed is highly beneficial in the rural areas of the Eastern Cape province of South Africa where many donkeys are kept. Currently, no mathematical models have been developed for optimum methane yield from the named substrate. [ABSTRACT FROM AUTHOR]

Highlights • Addition of ethanol stimulated methane release from the San Juan basin coal. • Ethanol inhibited methane production from the Powder River basin coal. • Addition of BES led to increased content of total organic carbon. • Fatty acids and aromatic acids were the dominant coal degradation products. Abstract To enhance methane release from bituminous coal in the Illinois basin, a nutrient recipe, an adapted microbial community, and optimal biogasification condition leading to maximum methane release have been developed. To evaluate whether the developed strategy is applicable to coals from other geological settings, coal samples from the San Juan (SJ) basin and Powder River (PR) basin were investigated. This study showed that without the addition of ethanol, more methane was released from PR coal than from SJ coal. Ethanol increased and inhibited methane production from SJ and PR coal, respectively. The dominant degradation products in all microcosms were similar even though the concentrations of identified compounds were dependent on the coal samples used. The addition of 2-bromoethanesulfonate completely arrested methanogenesis and resulted in higher content of total organic carbon in fermentation broth than those without. Comparing the coals before and after biotreatment, the elemental compositions did not change much even though significant mass losses were found for both coals. This study demonstrated that a given microbial community can be used for different ranks of coals. To maximize methane release, nutrient recipes may be shared for coals with the same rank, but not for coals having different compositions. [ABSTRACT FROM AUTHOR]

Abstract Biomethane Potential (BMP) test continues to be a useful and inexpensive assay to estimate the digestibility and maximum methane production of various organic substrates in anaerobic digestion or co-digestion processes. Despite its usefulness and several published efforts toward standardizing it, the BMP test still do not follow a universally accepted standard protocol. This makes the comparison of results among studies quite challenging. In this context, this paper analyzes 78 peer-reviewed BMP studies published between 2007 and 2018 that used the BMP test primarily to assess methane potential of commonly digested substrates, such as food waste, wastewater sludge and manure. We focused on the similarities and differences in the methodologies used and, where possible, the results obtained from these studies were compared and discussed. It was observed that many studies do not provide adequate information on salient aspects of the BMP methodology, and results are sometimes reported in different units of measurements. The inoculum to substrate ratio (ISR), substrate concentration and/or load should be clearly indicated in future studies, and positive controls should be included to validate BMP results. It is recommended that more studies assess the impact of nutrient addition, potential effects of continuous and intermittent mixing and mixing intensities and the influence of reactor size and headspace volume on BMP results. Graphical abstract Unlabelled Image Highlights • 78 BMP studies of commonly digested substrates published between 2007 and 2018 were reviewed. • Similarities and differences in methods were assessed, and where possible, results were compared. • Many studies do not provide adequate information on salient aspects of the BMP methodology. • ISR and substrate load should be indicated in all studies, and positive controls should be included. • Future studies should assess the impact of nutrient addition, mixing and reactor size on BMP results. [ABSTRACT FROM AUTHOR]

The increase was predicted of the methane (CH4) yield between untreated and pretreated weeds prior to co-digestion with cow dung. The mixed substrate slurry of weed was prepared using a ratio of weed to cow dung to water of 10:10:80, respectively. The total volatile solids (TVS) and total solids (TS) of the mixed substrate slurry of the untreated weeds were the two parameters input in the developed equation. Four types of weeds were used in the test: French weed, para grass, water lettuce, and sedge. The results showed that the % increase in CH4 yield depended on the ratio of TVS/TS of the mixed substrate slurry of the untreated weeds. The proposed developed equation was Y = 221.05X - 152.46, where X is the initial ratio of TVS/TS of mixed substrate slurry of untreated weed and cow dung, and Y is the % increase in CH4 yield obtained when the weed is pretreated using 1% sodium hydroxide for 24 hr prior to co-digestion. Water hyacinth was used as the substrate to verify the equation, and the results indicated that the equation performed well. Verification confirmed that the proposed equation successfully provided an accurate (within 10%) prediction of the % increase in CH4 yield. The equation could be useful in developing pretreatment options for weed co-digestion and environmental management. [ABSTRACT FROM AUTHOR]

Enhanced biogas production from anaerobic co-digestion of pig slurry and horse manure with mechanical pre-treatment. In this study, co-digestion of horse manure and pig slurry was investigated in a continuously stirred tank reactor, with a mechanical pre-treatment. Experiments were conducted at 37°C, with hydraulic retention times of 23 days and increasing shares of horse manure, corresponding to different horse manure to pig slurry ratios (HM:PS) equal to 0:100, 10:90, 13:87 and 20:80, in terms of percentage of inlet volatile solids (%VS inlet). The results show that the best synergetic effect between the microbial consortia of pig slurry and the high Carbon to Nitrogen ratio (C/N) of horse manure is obtained for the mixture of 20:80%VS inlet, yielding the highest specific methane production (SMP = 142.6 L kgTCOD−1) and the highest soluble chemical oxygen demand (SCOD) reduction (68.5%), due to the high volatile dissolved solids content and soluble chemical oxygen demand to total chemical oxygen demand ratio (SCOD/TCOD). Thus, co-digestion of horse manure and pig slurry is shown to be a promising approach for biogas production and as a waste treatment solution. Furthermore, the analysis provides a methodology for the pre-treatment of these substrates and to investigate into the best combination for improved biogas production. [ABSTRACT FROM AUTHOR]

Abstract A huge quantity of crop residues and animal dung as organic matter is produced in Pakistan and is a potential substrate for producing renewable energy in the form of methane. It is well established that nanoparticles are nutrient's source for the microorganism. The present study evaluated the effect of magnetite nanoparticles (Fe 3 O 4 NPs) on co-digestion of canola straw with buffalo dung (CS: BD) and banana waste plant with buffalo dung (BPW: BD). Before adding the dosage of Fe 3 O 4 , the nanoparticles (NPs) was synthesized and characterized. Five different dosages (0.4, 0.5, 0.81, 1.22, and 1.63) mg were implemented in two ratios of CS: BD (40:60) and BPW: BD (60:40), based on 5 g of volatile solids (VS). The experimental results showed that all doses effective stimulated microbial activities in the co-digestion and enhanced methane production. Maximum methane yield of 256.0 mLCH 4 /gVS and 202.3 mLCH 4 /gVS was obtained at a dosage of 0.81 mg and 0.5 mg for CS and BPW respectively compared with control. Additionally, cumulative methane yields were statistically analyzed (p < 0.05). However, compared with the optimized dose of Fe 3 O 4 , CS produces the higher volume of CH 4 than to BPW due to oilseed crop and carbon content. Graphical abstract Image Highlights • Fe 3 O 4 nanoparticles as be used in the co-digestion. • Methane increased by 39.4% of canola straw to buffalo dung at a dosage of 0.81 mg. • Methane increased by 33% of banana plant wastes to buffalo dung at a dosage of 0.5 mg. • Optimization and efficiency comparison of methane yield. [ABSTRACT FROM AUTHOR]

Abstract Batch assays were performed under a stressed condition during the anaerobic digestion process to assess the effect of component proportions on the quantity and pattern of biochemical methane yield of two sets of mixtures, consisting of poultry droppings (PD) with sugarcane bagasse (SB) and press mud (PM) for set A and PD with sugar beet roots and tops (SBRT) and PM for set B. Augmented simplex centroid design was used to design the mixture composition for the anaerobic co digestion. The reactor performances were assessed under identical conditions using cumulative methane yield (CMY) and percentage volatile solids destruction (PVSD) as the criteria. The maximum volume of methane were obtained 48.5 NL CH 4 kg−1 VS at mixture proportion of 66.67% of PM, 16.665% of PD and 16.665% of SB for set A and 44 NL CH 4 kg−1 VS at mixture proportion of 50% of PM and 50% of PD for set B. Synergistic effect were observed by adding a greater proportion of PM for both the sets of A and B. Antagonistic effect were obtained by adding a greater proportion of SB for set A and a higher proportion of SBRT for set B. Response surface methods and modeling were used to find out optimum mixture combinations for maximizing the methane production. From the optimization plots, the use of PD having the antagonistic effect was found for both the sets of A and set B. Graphical abstract Image 1 Highlights • Batch assays using mixture design were conducted under stressed conditions. • Study was performed to assess the effect of component proportions on methane yield. • The highest (48.5 NL) CH 4 kg−1 VS was found at 67% (PM) + 17% (PD) + 16% (SB) -(set A). • The highest (44 NL) CH 4 kg−1 VS was found at 50% (PM) and 50% (PD) -(set B). • Synergistic effect was observed by adding a greater portion of PM for both the sets. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Methane yield in HSAD system was stimulated significantly by 100 mg/L antibiotics. • Modified Gompertz model was best for HSAD system under different antibiotic loads. • Antibiotics enriched Methanosarcina but stressed Methanosaeta and Methanoculleus. • VFAs, SCOD and other organic matters were affected differently by antibiotics. • Negative verification test was conducted to confirm the stimulating effects. Abstract High-solid anaerobic digestion (HSAD) is a promising method to centralizedly dispose dewatered sludge from municipal wastewater treatment plants. Until now, few studies have focused on determining the different effects of antibiotic residues on methane yield and microbial communities over a wide range of antibiotic loads in HSAD system. This study investigated the effects of seven typical antibiotics (oxytetracycline, sulfadimethoxine, sulfamethoxazole, enrofloxacin, ciprofloxacin, ofloxacin and norfloxacin) on HSAD over a wide range of loads (0–500 mg/L). The results showed that 10 mg/L of antibiotics had no obvious effect on CH 4 yield. Interestingly, 100 mg/L of antibiotics exhibited a strong stimulating effect on CH 4 yield. Antibiotics at a concentration of 500 mg/L generally suppressed CH 4 yield at the initial stage of anaerobic digestion, and some systems recovered at the late stage of the process with a much higher daily CH 4 yield than other systems. Among the three kinetics models, the modified Gompertz model showed the best fit to the experimental data (R2: 0.9772–0.9997). Antibiotic residues did not have strong effects on the bacterial community, but did affect the archaeal community. The relative abundance of Methanosarcina increased while that of Methanosaeta and Methanoculleus decreased with the antibiotic concentrations increasing. The heat map showed that the archaeal community in the system with 500 mg/L was characterized by Methanobacteriales and Halobacteriales. This study provides a new insight into the different effects of antibiotics on HSAD. [ABSTRACT FROM AUTHOR]

Published studies have shown that methane yield (g CH4/kg dry matter) from sheep is positively correlated with the size (volume and surface area) of the reticulo-rumen (RR) and the weight of its contents. However, the relationship between CH4 yield and RR shape has not been investigated. In this work, shape analysis has been performed on a data set of computerised tomography (CT) scans of the RR from sheep having high and low CH4 yields (n =20 and n =17, respectively). The three-dimensional geometries of the RRs were reconstructed from segmented scan data and split into three anatomical regions. An iterative fitting technique combining radial basis functions and principal component (PC) fitting was used to create a set of consistent landmarks which were then used as variables in a PC analysis to identify shape variation within the data. Significant size differences were detected for regions corresponding to the dorsal and ventral compartments between sheep with high and low CH4 yields. When the analysis was repeated after scaling the geometries to remove the effect of size, there was no significant shape variation correlating with CH4 yield. The results have demonstrated the feasibility of CT-based computational shape determination for studying the morphological characteristics of the RR and indicate that size, but not shape correlates with CH4 yield in sheep. [ABSTRACT FROM AUTHOR]

Abstract Searching for available biomasses is a key factor to promote renewable energy, especially biogas. This paper examines the biogas potential of biomass from Danish buffer strips with different types of natural vegetation and the possibility of using the functional trait composition of the vegetation and the nutrient composition of the biomass as indicators for the quantity of the biomass and its biogas potential. Biomass was harvested from 73 plots in 2014 and 2015 and biomass yield, nutrient content (CNP) and methane yields were determined. Prior to harvesting, the plant communities were characterised in terms of species composition, and a cluster analysis was performed to identify species assemblages in terms of vegetation clusters. Four ecologically meaningful clusters were obtained: a tall herb fringe community, a tall grass community, a low herb and grass community and a rich fen/wet meadow community. The biomass yield was numerically higher in the tall herb fringe and the tall grass communities, while the specific methane yield was higher in the tall grass and low herb and grass communities. When all samples were analysed together, the biomass yield was positively correlated with some of the vegetation traits (Ellenberg value soil reaction and leaf dry matter content) and negatively with nitrogen and phosphorus contents in the biomass. In addition, a negative correlation was observed between the biomass yield and the specific methane yield. In contrast, the biomass yield was positively correlated with the methane yield per ha, indicating that even small differences in biomass yield can be more relevant for the methane yield per ha than differences in specific methane yields in natural vegetation. Biomass from tall herb fringe, tall grass and low herb and grass communities is suitable to be incorporated into the anaerobic digestion supply chain; and in these communities it could be possible to predict methane yield per ha, especially in tall grass community, using vegetation traits (Ellenberg values and Grimes life strategy) and phosphorus content in the biomass. [ABSTRACT FROM AUTHOR]

The goal of this study was to develop an operational steam explosion pretreatment for effective modification of rice straw chemical structure in order to improve its biodegradability and methane yield. The parameters of pressure (5 bar to 15 bar), moisture (0% to 70%), and time (1 min to 15 min) were studied in steam explosion pretreatment. The steam explosion efficiency was investigated according to the changes in crystallinity structure and chemical composition on rice straw, as well as the methane yield from straw. Steam explosion changed the structure linkages between the lignin and carbohydrate, which was indicated by a reduction in the peak intensities in the bonds from 1648 cm-1 to 1516 cm-1. After pretreatment, the crystallinity index of the rice straw in the 10 bar-10 min cycle with no moisture and 15 bar-10 min cycle with 70% moisture increased from 22.9% to 28.3% and 28.6%, respectively. Steam explosion efficiently decreased the lignin. The highest reduction in the amount of lignin was observed with the 10 bar-10 min cycle, which reached from 18.6% to 13.0%. The methane yield increased with the cycles 10 bar-10 min and 15 bar-15 min with 35% moisture, and 15 bar-10 min with 70% moisture by 113%, 104%, and 147% compared to that of the untreated straw, respectively. Moreover, the highest biodegradation percent of the rice straw was obtained in these cycles. [ABSTRACT FROM AUTHOR]

While anaerobic digestion is a reliable method that treats the waste and produces renewable biomethane fuel, the necessary sludge in liquid form is difficult to handle due to the constant biogas generation. Therefore, this study investigates the possibility of convective air drying, namely heat pump and hot air circulation oven as preservation methods for anaerobic microbial sludge. Drying was conducted at various temperatures, ranging from 22 to 70°C. The study found that heat pump drying at 22°C resulted in highest chemical oxygen demand removal of 55.3% as well as the least log reduction in methanogens and anaerobes at 1.4 and 2.4, respectively. [ABSTRACT FROM AUTHOR]

Abstract Microbial electrochemical system (MES) was integrated into anaerobic digestion (AD) to improve the overall process efficiency by enhancing methane (CH 4) production. CH 4 fermentation at various glucose concentrations (2, 4, 8 and 10 g/l) was evaluated along with corresponding control (without electrodes) operations. The maximum CH 4 yield of 0.34 l- CH 4 /g COD was obtained with both 2 and 4 g/l glucose concentrations (MES), which was about 1.4 and 2.4 times, respectively, higher than the values obtained with corresponding control operations. However, at 10 g/l, similar performance (∼0.07 l- CH 4 /g COD) was observed with both control and MES operations, which might be due to pH drop occurred by volatile fatty acids (VFAs) buildup in the process. Substrate removal was amplified in the presence of MES with faster degradation of VFAs at all substrate concentrations except 10 g/l. This enhanced utilization of VFAs in the MES process is an important aspect to recover from initial pH drops, especially at higher substrate concentration to maintain the optimum pH for methane fermentation. The current generation and cyclic voltammetric profiles suggest that the enhanced CH 4 production in MES was attributed to the bioelectrochemical reactions on the electrodes. Graphical abstract Image 1 Highlights • Enhancement of overall performance was achieved in MES integration with AD. • The COD loading up to 8 g/l showed enhanced methane generation compared to control. • Maximum enhancement of CH 4 production was observed at 4 g/l glucose concentration. • MES delayed VFAs accumulation and facilitated optimum pH and redox microenvironment. [ABSTRACT FROM AUTHOR]

Highlights • Anaerobic co-digestion of pretreated sugarcane residues with manure was investigated. • AFEX pretreatment caused key structural modifications and enhanced nitrogen content. • AFEX treated biomass achieved high methane yields regardless of manure co-digestion. • Steam exploded biomass required co-digestion with manure to maximize methane yields. • Nutrient content of solid digestates suitable for soil amendment or fertilizer use. Abstract The co-digestion of pretreated sugarcane lignocelluloses with dairy cow manure (DCM) as a bioenergy production and waste management strategy, for intensive livestock farms located in sugarcane regions, was investigated. Ammonia fiber expansion (AFEX) increased the nitrogen content and accelerated the biodegradability of sugarcane bagasse (SCB) and cane leaf matter (CLM) through the cleavage of lignin carbohydrate crosslinks, resulting in the highest specific methane yields (292–299 L CH 4 /kg VSadded), biogas methane content (57–59% v/v) and biodegradation rates, with or without co-digestion with DCM. To obtain comparable methane yields, untreated and steam exploded (StEx) SCB and CLM had to be co-digested with DCM, at mass ratios providing initial C/N ratios in the range of 18 to 35. Co-digestion with DCM improved the nutrient content of the solid digestates, providing digestates that could be used as biofertilizer to replace CLM that is removed from sugarcane fields during green harvesting. [ABSTRACT FROM AUTHOR]

The suitability of miscanthus biomass for anaerobic digestion has already been confirmed by several studies. However, it is rarely used as feedstock in biogas plants, mainly due to uncertainty about the optimal harvest regime with regard to the long‐term methane hectare yield and resilience of the crop to green cutting. The recommended green‐cut date for the only commercially available genotype Miscanthus × giganteus (M×g) ranges from September to November. This timeframe is too broad for agricultural practice and needs to be both narrowed down and further specified for different genotypes. The aim of this study was to identify the most suitable harvest window for an autumn green cut of miscanthus, which delivers both a high dry matter and methane yield while securing the long‐term productivity of the crop. A further objective was to quantify the effect of genotypic differences, such as leaf to stem ratio, on the substrate‐specific biogas and methane yield. For these purposes, a field trial with four genotypes (M×g, GNT1, GNT3, Sin55) was conducted over 2 years (2016/2017) and harvested at 2‐week intervals on three dates between mid‐September to mid‐October. Methane hectare yield ranged from 3,183 m³ CH4 ha−1 a−1 (Sin55) to 5,265 m³ CH4 ha−1 a−1 (M×g), which is mainly influenced by dry matter yield. The substrate‐specific methane yield was higher for the leaf (311.0 ml CH4 (g oDM)‐1) than the stem fraction (285.1 ml CH4 (g oDM)‐1) in all genotypes due to lower lignin content of leaves. Of all genotypes, M×g showed the highest and Sin55 the lowest nutrient use efficiency. We conclude that miscanthus in Germany should be harvested in October to maximize methane yields and nutrient recycling and minimize yield reduction. Additionally, to increase methane hectare yields even further, future miscanthus breeding should focus on a higher leaf proportion. The aim of this study was to identify the most suitable harvest window for an autumn green cut of miscanthus, which delivers both a high dry matter and methane yield while securing the long‐term productivity of the crop. Additionally, we wanted to quantify the effect of genotypic differences (leaf to stem ratio) on the substrate‐specific biogas and methane yield. For these purposes, a field trial with four genotypes was conducted over 2 years and harvested on three dates between mid‐September and mid‐October. We conclude that miscanthus in Germany should be harvested in October to maximize methane yields and nutrient recycling and minimize yield reduction. [ABSTRACT FROM AUTHOR]

Agricultural production plays an integral role in the regional economy, under the conditions of climate change with uneven distribution of rainfall and extreme heat, expansion of areas with degraded soils, affecting agricultural productivity. The identification of alternative crops that need less water and produce increased yield of organic matter per unit of water is important for agricultural sustainability. Adequate animal nutrition is one of the vital prerequisites to enhance the productivity and the performance of ruminants in terms of milk and meat production. Silage is one of the key components of the feed for herbivorous domestic animals. Sorghum species have recently gained popularity due to their numerous advantages, such as heat and drought tolerance and resistance to specific diseases and pests. Besides, they are well adapted to a wide range of soil types and recover easily after grazing or multiple harvests. The aim of this study was to determine the green mass yield, the silage quality, the nutrient content and the fodder value of the nonnative, perennial, rhizomatous grass - Sorghum almum, grown in an experimental field of the National Botanical Garden (Institute), Chişinău. In the third growing season, the perennial sorghum was characterized by high growth rate and regenerative capacity after being cut. The annual productivity, from three harvests, was 6.1 kg/m² green mass or 1.4 kg/m² dry matter, surpassing the productivity of maize by 35%. It was determined that the quality of the silage varied depending on the harvest time: pH 3.8-4.5, lactic acid 24.7-45.5 g/kg, acetic acid 6.3-9.1 g/kg, butyric acid 0.2g/kg, organic matter 892.4-922.8 g/kg, crude protein 50.7-95.2 g/kg, crude fats 20.6-36.8 g/kg, crude cellulose 402- 428.9 g/kg, nitrogen free extract 330.5-407.2 g/kg, carotene 15.67-47.17 mg/kg, calcium 3.7-5.5 g/kg and phosphorus 1.8-2.7 g/kg. The fodder value of the prepared silage was 0.14-0.18 nutritive units/kg and 1.47-1.82 MJ/kg metabolizable energy. The potential methane yield of Sorghum almum silage substrates varied from 233 to 242 l/kg. The silage obtained from Sorghum almum, according to organoleptic characteristics (smell, colour and consistency) and biochemical indices (pH, content of organic acids and their correlation, chemical composition), largely meets the standards and can be used as alternative feedstuff. [ABSTRACT FROM AUTHOR]

The purpose of this work was to assess the enhancement of the anaerobic digestion process of sewage sludge by the addition of orange peel as co-substrate. In this experimental study, an evaluation of the co-digestion process in a semi-continuous stirred tank reactor was carried out under mesophilic conditions (37 ± 0.2 °C) during an operation time up to 315 days. All trials were performed at a hydraulic retention time of 15 days and the AD reactor was fed daily with a mixture of sewage sludge and orange peel pulp, previously prepared. The organic loading rate was kept at 1.80 ± 0.31 g VS L−1 day−1 in all trials. A reference scenario (T0), mono-digestion, was performed using sewage sludge as substrate (primary sludge and activated sludge, 40:60, v/v). Thereafter, two different anaerobic co-digestion trials were carried out, one with pre-treated orange peel (T1) and the other with reduced D-limonene content (T2). Trials with pre-treated orange peel (T1 and T2) led to two- and threefold improvements in biogas and methane yields, compared with the reference scenario (T0). Furthermore, the reduction of D-Limonene content (T2) increased the methane yield by around 70% compared with T1. Therefore, it was proved that the sieving pre-treatment is effective to avoid the inhibitory effect of D-limonene. [ABSTRACT FROM AUTHOR]

Methane yield values (MY; g methane/kg dry-matter intake) in beef cattle reported in the global literature (expanded MitiGate database of methane-mitigation studies) were analysed by cluster and meta-analyses. The Ward and k means cluster analyses included accounting for the categorical effects of methane measurement method, cattle breed type, country or region of study, age and sex of cattle, and proportion of grain in the diet and the standardised continuous variables of number of animals, liveweight and MY. After removal of data from outlier studies, meta-analyses were conducted on subsets of data to produce prediction equations for MY. Removing outliers with absolute studentised residual values of >1, followed by meta-analysis of data accounting for categorical effects, is recommended as a method for predicting MY. The large differences among some countries in MY values were significant but difficult to interpret. On the basis of the datasets available, a single, global MY or percentage of gross energy in feed converted to methane (Y m) value is not appropriate for use in Intergovernmental Panel on Climate Change (IPCC) greenhouse accounting methods around the world. Therefore, ideally country-specific MY values should be used in each country's accounts (i.e. an IPCC Tier 2 or 3 approach) from data generated within that country. Greenhouse accounting methods contain assumed methane yield values (MY) to calculate total methane emissions from national beef herds. All reported beef cattle MY values were analysed (accounting for country or region of study, measurement method, cattle breed type, age and sex and diet type) and large MY differences were found among some countries. Therefore, country-specific MY values should be used in each country's accounts (i.e. an IPCC Tier 2 or 3 approach) from data generated within that country. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cow manure (1/3) functioned as a stimulant during oat straw anaerobic digestion. • Addition of cow manure affected methane yield more than the total solids content. • C/N ratio = 27 was suitable for anaerobic digestion of oat straw waste and cow manure. • Higher methane yields were due to the increasing degradation of cellulose. • Clustering analysis provided significant guidance for demonstrating project process. Abstract Impacts of adding different amounts of cow manure (CM) on the anaerobic digestion (AD) of oat straw (OS) with total solids content (TS) values of 4%, 6%, 8% and 10% was assessed over 50 days using batch experiments. A modified Gompertz model was introduced to predict the methane yield and determine the kinetic parameters. The optimum addition was a 1:2 ratio of CM to the OS added, which resulted in a suitable C/N ratio of 27 and a higher degradation rate of lignocellulose. The best cumulative methane yield of 841.77 mL/g volatile solids added (VS added) was 26.64% greater than that of digesting OS alone. In addition, the amount of CM added produced larger effects than that of changes in the TS. However, higher CM concentrations were found to be inhibitory. Clustering analysis could provide significant guidance for demonstrating project process and combining farming and animal husbandry. [ABSTRACT FROM AUTHOR]

Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years ago to measure methane production from grazing and non-housed animals, no studies have specifically investigated whether ambient wind speed, temperature, relative humidity and rainfall influence the accuracy of the method. The aim of this research was to investigate how these weather factors influence the measurement of enteric methane production by the SF6 technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Methane production from individual cows was measured daily over the last 5 days of each 32-day period. An automated weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily wind speed, average daily temperature, average daily relative humidity and total daily rainfall measurements to dry matter intake, average daily methane production and methane yield of each cohort of cows. It was concluded that the modified SF6 technique can be used outdoors during a range of wind speeds, ambient temperatures, relative humidities and rainfall conditions without causing a significant effect on the measurement of methane production or methane yield of dairy cows.

Nutritional strategies can be employed to mitigate greenhouse emissions from ruminants. This article investigates the effects of polyphenols extracted from the involucres of Castanea mollissima Blume (PICB) on in vitro rumen fermentation. Three healthy Angus bulls (350 ± 50 kg), with permanent rumen fistula, were used as the donors of rumen fluids. A basic diet was supplemented with five doses of PICB (0%–0.5% dry matter (DM)), replicated thrice for each dose. Volatile fatty acids (VFAs), ammonia nitrogen concentration (NH3-N), and methane (CH4) yield were measured after 24 h of in vitro fermentation, and gas production was monitored for 96 h. The trial was carried out over three runs. The results showed that the addition of PICB significantly reduced NH3-N (p < 0.05) compared to control. The 0.1%–0.4% PICB significantly decreased acetic acid content (p < 0.05). Addition of 0.2% and 0.3% PICB significantly increased the propionic acid content (p < 0.05) and reduced the acetic acid/propionic acid ratio, CH4 content, and yield (p < 0.05). A highly significant quadratic response was shown, with increasing PICB levels for all the parameters abovementioned (p < 0.01). The increases in PICB concentration resulted in a highly significant linear and quadratic response by 96-h dynamic fermentation parameters (p < 0.01). Our results indicate that 0.2% PICB had the best effect on in-vitro rumen fermentation efficiency and reduced greenhouse gas production.

[Display omitted] • At high OLR, COD removal efficiency of ASDS-UASB and ASSW-UASB were highest. • Average methane yield of ASSW-UASB is 15.3% higher than that of ASDS-UASB. • Excess sludge produced by ASSW-UASB of was 73.0% lower than that of ASDS-UASB. • ASDS-UASB reduced pathogenic bacteria by 88%, while ASSW-UASB maintained a low level. The effects of heterogenous (anaerobic sludge from treating distillery sewage, ASDS) and homologous (anaerobic sludge from treating swine wastewater, ASSW) inocula on anaerobic digestion and the microbial community in an up-flow anaerobic sludge blanket treating swine wastewater were compared. The highest chemical oxygen demand removal efficiencies with ASDS (84.8%) and ASSW (83.1%) were obtained with an organic loading rate of 15 kg COD/m3/d. For ASSW compared with ASDS, methane production efficiency was 15.3% higher and excess sludge production was 73.0% lower. The abundance of the cellulose hydrolyzing bacterium Clostridium sensu stricto_1 with ASDS (36.1%) was 1.5 times that with ASSW, while that of Methanosarcina with ASSW (22.9%) was > 100 times that with ASDS. ASDS reduced the content of pathogenic bacteria by 88.0%, while ASSW maintained a low level of pathogenic bacteria. ASSW greatly improved the methane production efficiency of wastewater and is more suitable for treating swine wastewater. [ABSTRACT FROM AUTHOR]

• The interval temperature digester exhibited the highest methane yield. • The decomposition rate of organic matter increases with increasing temperature. • Methanogenesis, rather than hydrolysis, is limited at the thermophilic temperature because of the loss of Methanosarcina. • Efficient methanogenesis occurs under the balance between hydrolysis and methanogenesis at interval temperature. • Our findings may provide insight into the temperature control in AD systems. Anaerobic digestion (AD) at mesophilic and thermophilic interval temperatures has received increasing attention due to an unexpectedly higher methane yield. However, there is no general consensus and the mechanisms of microbial regulation under interval temperature remain unclear. Therefore, this study evaluated the effect of conventional and interval temperatures on methanogenesis performance and microbial regulation in continuous AD of wilted corn straw. The results demonstrated that the hydrolysis rate increased with increasing temperatures, probably due to the predominant Firmicutes and Proteobacteria, whose abundance in D55 was more than 72% and 19%, respectively. However, in the stable period (31–55 d) experiments, digesters D35, D45, and D55 achieved an average methane yield of 224 ± 34, 311 ± 55, and 261 ± 49 N mL/g VS/d, respectively. Interval temperature substantially enhanced methane yield by 39.4% and 19.0% compared to that from mesophilic and thermophilic digesters, respectively. A higher proportion of Methanosarcina (94.42–94.73%) promoted the acetoclastic methanogenesis at interval temperature, implying that methanogenesis, rather than hydrolysis, is limited at the thermophilic temperatures because of the loss of Methanosarcina. Furthermore, a high abundance of essential genes involved in methane metabolism was found to stimulate methane production in the interval temperature digester. These findings revealed that the interval temperatures may be a balanced zone between hydrolysis and methanogenesis for achieving higher methane yield and provided a new perspective strategy for AD. [ABSTRACT FROM AUTHOR]

Ensiling is a widely used method for preserving crop stalks as biogas feedstock. However, secondary fermentation of silage is an inevitable problem that causes significant mass and energy losses. In this study, the effect of different lactic acid bacteria (LAB) inoculants on the fermentation pattern, aerobic stability, and methane production of maize stover was investigated. Maize stover was ensiled for 50 days with or without different LAB inoculants, followed by 10 days of air exposure. Methane production from the stover after the two processes was determined through batch anaerobic digestion (AD) tests. Lactiplantibacillus plantarum enhanced the homo-fermentation and reduced the pH of silage. Lentilactobacillus buchneri improved the hetero-fermentation of hexose, while causing higher dry matter loss (DML) than other inoculants. Limosilactobacillus fermentum enhanced pentose hetero-fermentation and increased both lactic acid and acetic acid production with minor DML. All the tested inoculants reduced the DML, improved the aerobic stability, and increased the methane yield of maize stover after ensiling (by up to 18.8%) and after air exposure (by up to 41.0%), with Limosilactobacillus fermentum exhibiting superior performance. The Limosilactobacillus fermentum treatment showed smaller variations in the bacterial community in AD than other treatments during air exposure. Ruminococcaceae , SHA-31 , SB-1 , Lachnospiraceae , Marinilabiaceae, and Erysipelotrichaceae showed positive correlations with water-soluble components, whereas Anaerolinaceae was positively correlated with cellulose or hemicellulose. [Display omitted] • Maize stover was ensiled with different lactic acid bacteria for methane production. • All the inoculants improved the aerobic stability and reduced dry matter loss. • The inoculants led to up to 41% higher methane yield after air exposure. • Limosilactobacillus fermentum enhanced pentose hetero-fermentation into acetic acid. • Limosilactobacillus fermentum showed superior performance in methane preservation. [ABSTRACT FROM AUTHOR]

[Display omitted] • AD performance with biochar or iron addition was evaluated at different ISR. • Hydrolysis and acidification are dependent on ISR. • Methane production and yield rate relied on the ISR rather than CMs. • Bacterial community shaped by ISR while Fe up-regulated Methanobacterium. The contribution of inoculum-to-substrate ratios (ISRs) and conductive materials (CMs) on the productivity of anaerobic digestion (AD) remains unclear, particularly for protein-rich organic waste. This study investigated whether the addition of CMs, i.e., biochar and iron powder, can overcome the limitations imposed by varying ISRs for the AD of protein as the sole substrate. Results indicate the ISR plays a decisive role in hydrolysis, acidification, and methanogenesis for protein conversion, irrespective of CMs addition. Methane production increased stepwise as the ISR escalated to 3:1. The addition of CMs provided limited improvement, and iron powder even inhibited methanogenesis at a low ISR. Bacterial community variations were contingent on the ISR, while iron powder supplementation significantly elevates the proportion of hydrogenotrophic methanogen. This study demonstrates that the addition of CMs could affect methanogenic efficiency but can not overcome the limitation of ISRs for the AD of protein. [ABSTRACT FROM AUTHOR]

The impact of semi-continuous and alternating microbial feeding patterns on methane yield from UASB reactors. [Display omitted] • The UASB reactor operation failed during the long-term semi-continuous feeding. • An alternate feeding pattern is preferred when reactor feeding cannot be equalized. • Methanosaeta shifted to Methanosarcina in semi-continuous feeding reactors. • The syntrophic relationship was enhanced with the enrichment of Actinobacteria. Feeding strategy represents one of the most important bioreactor operation parameters, however, how different feeding patterns impact reactor microbiome development and treatment performance in up-flow anaerobic sludge blanket (UASB) reactors has not been systematically investigated. In the present study, three feeding strategies, including continuous feeding, semi-continuous feeding (with starvation-feast cycles), and alternate feeding (with high loading-low loading cycles) were assessed and compared using three laboratory-scale UASB reactors. It was observed that both long and short starvation-feast cycles provided by a semi-continuous feeding strategy failed to sustain stable anaerobic digestion under the conditions examined in the present study, while alternate feeding with high and low loading cycles supported microbial development. This feeding pattern resulted in an average methane yield of 74 ± 8.5% and an effluent COD removal efficiency of 89 ± 2.8%, which is comparable to the reactor operated under a continuous feeding pattern (Methane yield of 72 ± 2.4% and a COD removal efficiency of 87 ± 7.7%). Interestingly, as compared to continuous operation, reactors experienced starvation/feast stress (i.e., semi-continuous feeding) developed significantly higher methanogenic activities once continuous feeding was presumed, with dominant methanogens shifted from Methanosaeta in continuous feeding UASB to Methanosarcina in reactors undergone semi-continuous feeding. It was concluded that reactor feeding strategies can significantly impact microbiome communities in UASB, and an alternate feeding pattern is preferred, as compared to semi-continuous operation when reactor feeding cannot be continuously supplied. [ABSTRACT FROM AUTHOR]