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Metal-contaminated plants after phytoremediation provide organic matter and trace metals for anaerobic fermentation. In this study, alfalfa straw harvested from an abandoned iron mine was used for anaerobic fermentation. The variation of metal speciation during the anaerobic fermentation process and the influences on fermentation parameters were investigated. The results showed that the group adding alfalfa increased the peak daily biogas yield by 33.40 % compared to the group with cow dung only. Fe in the fermenter was predominated by the soluble and the residual fraction. Cu was transformed from soluble Cu to residual Cu with the fermentation progressed. On the 13th day of fermentation, the percentage of soluble Fe decreased while the percentage of soluble Cu, Ni and Zn increased which induced the daily biogas yields peak. Metal speciation was correlated to the fermentation parameters. Daily biogas yields were negatively correlated to the acid-extractable fraction of Ni and Zn (p

Purpose: The soil elementome has been recently proposed as a promising novel approach for describing the response of soil bioelemental composition to tree species. Using bioelement stoichiometry, we explored the effects of soil biogeochemical processes and tree species coexistence on soil elementome.Methods: Soil bioelements were analyzed at three soil layers (A, B and C horizons) in four forests (Picea asperata (PA), Larix principis-rupprechtii (LP), Betula Platyphylla (BP), and Betula Platyphylla - Larix principis-rupprechtii (L-B) mixed forest) in Chongli District, Zhangjiakou City, Hebei Province, China., The soil elementomes of 11 bioelements (C, N, P, O, S, K, Ca, Na, Mg, Mn and Cr) were analyzed by principal component analysis (PCA) based on soil C:N:P stoichiometry. We calculated elementome distance (ED) to examine differences between soil horizons and forests.Results: We found that soil elementomes in the soil layers decreased with depth and that ED between the B and C horizons was larger than that between A and B horizons. Moreover, differences in soil elementomes were smaller for tree species that often coexist compared to those that rarely live together.Conclusions: Our results suggest that tree species coexistence promotes similarity in soil elementomes probably due to creation of similar soil conditions. The findings of this research provide a new understanding about the relationship between tree species coexistence and soil bioelemental composition or stoichiometry.

In this work, phosphorus fractionations (PFs) in the surface, overlying and interstitial water, sediments and two macrophytes (reed and cattail) were investigated in a near-nature constructed wetland. The mechanism of vertical migration and transformation, diffusion flux of sediment and overlying water and the risk of phosphorus release from sediments were studied. The results showed that the occurrence of macrophytes influenced the horizontal and vertical distributions of phosphorus. Reed community area resulted in different orders of TP, TDP and SRP concentrations in the surface, overlying and interstitial water as well as higher removal efficiencies than open water area and cattail community area. Phosphorus distributions in reed community area were closely correlated to the environmental factors and phosphorus in the overlying water were significantly correlated to the biomass and morphological characteristics of reeds (p

The mechanism supporting the stability of complex food webs is an important, yet still controversial issue in ecology. Integrating the bioenergetic model with a natural plankton food web with empirical organism body mass distribution, we studied the effects of taxa diversity, nutrient enrichment simulation and connectance on the stability of plankton, and the underlying mechanisms. The behavior and functions of plankton with different body masses in the system were also explored. The results showed that genus richness promoted the temporal stability of community but reduced that of population. Meanwhile, the effects of taxon extinction on community biomass and temporal stability depended on the body masses of those lost taxa. Enrichment decreased phytoplankton and zooplankton community stability directly by increasing the temporal variability of biomass and indirectly by reducing taxa diversity. Enrichment preferentially caused phytoplankton taxa with the highest individual biomass to go extinct and the ones with smaller to increase in biomass. The effects, as well as the underlying mechanisms of connectance on phytoplankton and zooplankton stability were different. High connectance promoted the persistence and biomasses of both zooplankton and small-bodied phytoplankton but reduced those of larger-bodied phytoplankton. The results and methodology in this research will be helpful in understanding and analyzing the stability of plankton communities.

The kinetic evaluation of the biogas potential from heavy metal stressed anaerobic fermentation process was performed using modified sigmoidal bacterial growth curve equations (modified Gompertz and Logistic) in order to investigate their suitability to describe the degradation patterns associated with varied heavy metal species and concentration. The anaerobic co-fermentation experiments were performed at mesophilic conditions with mixed cow dung and Phragmites straw as feedstocks. The results show that appropriate concentration of heavy metals brought forward the biogas peaks, shorten the lag-phase (λ) and promoted the efficiency of co-fermentation. In this way, the cumulative biogas yields expressed the one-phase process and fitted the sigmoidal bacterial growth curve equations better. Both the modified Gompertz model and Logistic model were able to represent the experimental data in the presence of heavy metals as shown by the no significant different correlation coefficients (R2). However, the discrepancies between the experimental and fitting results of the modified Gompertz model were smaller than the Logistic model which suggested that the earlier was more suitable for describing the degradation patterns under heavy metal stress. The results of this research are expected to provide theoretical guidance for studying the impact of heavy metals and modelling research of anaerobic fermentation process.

The impact of chronic photoinhibition of photosystem II (PSII) on the productivity of plants remains unknown. The present study investigated the influences of persistent decline in the PSII yield on morphology and productivity of Arabidopsis plants that were exposed to lincomycin at two different developmental stages (seedling and rosette stage). The results indicated that, although retarded, the lincomycin treated plants were able to accomplish the entire growth period with only 50% of the maximum quantum yield of primary photochemistry (Fv/Fm) of the control plants. The decline in quantum yield limited the electron transport rate (ETR). The impact of lincomycin on NPQ was not significant in seedlings, but was pronounced in mature plants. The treated plants produced an above ground biomass of 50% compared to control plants. Moreover, a linear relationship was found between the above ground biomass and total rosette leaf area, and the slope was decreased due to photoinhibition. The starch accumulation was highly inhibited by lincomycin treatment. Lincomycin induced a significant decrease in seed yield with plants treated from the rosette state showing higher yield than those treated from the seedling stage. Our data suggest that the sustained decline of PSII efficiency decreases plant productivity by constraining the ETR, leaf development and starch production.

The effect of two widely distributed macrophytes, reed and cattail, on phosphorus fractionations (PFs) of surface sediments distributions from a near-nature constructed wetland were studied in both autumn and spring. The results showed that the average values of PFs in the sediments were ranked in the order of Ca-P > Org-P > Al-P ≈ Fe-P > Ex-P > O-P. The mobile PFs, such as Al-P, Fe-P, Ex-P and Org-P influenced the TP concentrations in macrophytes free area. Only Ca-P was related with TP in macrophytes covered area, indicating the P stability of reed community sediment (RCS) and cattail community sediment (CCS). The other compositions of sediments, i.e. organic matter (OM), alkaline phosphatase activity (APA), and active-Fe were greatly decreased in the presence of macrophytes, while active-Al were slightly increased. OM and active-Al were found to be more significant related with PFs in OWS and RCS, while APA and active-Fe were related with PFs in the macrophytes covered sediments. Therefore, macrophytes induced the variation of sediment compositions and further influenced the distributions and stabilization of PFs. Moreover, cattail community performed better in declining the sediment compositions, P accumulation and its release.

The effects of Cd, Cd + Fe, and Cd + Ni on the thermophilic anaerobic fermentation of corn stover and cow manure were studied in pilot experiments by investigating the biogas properties, process stability, substrate biodegradation, and microbial properties. The results showed that the addition of Fe and Ni into the Cd-containing fermentation system induced higher cumulative biogas yields and NH4+&ndash, N concentrations compared with the only Cd-added group. Ni together with Cd improved and brought forward the peak daily biogas yields, and increased the CH4 contents to 80.76%. Taking the whole fermentation process into consideration, the promoting impact of the Cd + Ni group was mainly attributed to better process stability, a higher average NH4+&ndash, N concentration, and increased utilization of acetate. Adding Fe into the Cd-containing fermentation system increased the absolute abundance of Methanobrevibacter on the 13th day, and Methanobrevibacter and Methanobacterium were found to be positively correlated with the daily biogas yield. This research was expected to provide a basis for the reuse of biological wastes contaminated by heavy metals and a reference for further studies on the influence of compound heavy metals on anaerobic fermentation.

Anaerobic fermentation is a cost-effective biowaste disposal approach. During fermentation, microorganisms require a trace amount of metals for optimal growth and performance. This study investigated the effects of metal mixtures on biogas properties, process stability, substrate degradation, enzyme activity, and microbial communities during anaerobic fermentation. The addition of iron (Fe), nickel (Ni), and zinc (Zn) into a copper (Cu)-stressed fermentation system resulted in higher cumulative biogas yields, ammonia nitrogen (NH4+-N) concentrations and coenzyme F420 activities. Ni and Zn addition enhanced process stability and acetate utilization. The addition of these metals also improved and brought forward the peak daily biogas yields as well as increased CH4 content to 88.94 and 86.58%, respectively. Adding Zn into the Cu-stressed system improved the abundance of Defluviitoga, Fibrobacter and Methanothermobacter, the degradation of cellulose, and the transformation of CO2 to CH4. The bacterial and archaeal communities were responsible for the degradation of lignocelluloses and CH4 production during the fermentation process. This study supports the reutilization of heavy metal-contaminated biowaste and provides references for further research on heavy metals impacted anaerobic fermentation.

The kinetics of biogas production on anaerobic fermentation with anionic surfactants added was evaluated using the sigmoidal models (the modified Gompertz and Logistic). The mesophilic anaerobic co-fermentation experiments under different anionic surfactants concentrations were conducted with mixed cow dung and corn straw as feedstocks. The results showed that the anionic surfactants in appropriate concentrations on anaerobic fermentation increased the cumulative biogas yields while prolonged the lag phase time. The modified Logistic model performed better than modified Gompertz model in fitting the experimental results of anaerobic co-fermentation with anionic surfactants added. The results of this study were expected to provide theoretical guidance for studying the impact of anionic surfactants and modelling the kinetic process of anaerobic co-fermentation.

The importance of nickel (added as NiCl2) on mesophilic anaerobic fermentation of Phragmites australis straw and cow dung was demonstrated by investigating the biogas properties, pH values, organic matter degradation [chemical oxygen demand (COD)] and enzyme activities (cellulase, protease and dehydrogenase) during the fermentation process. The results showed that Ni2+ addition increased the cumulative biogas yields by >18 % by improving the efficiency of first peak stage and bringing forward the second peak stage. The pH values were not significantly influenced by Ni2+ addition (p > 0.05). Biogas yields were associated with variations in COD concentrations rather than momentary concentrations. At the start-up stage of fermentation (4th day), the biogas yields increased gradually together with the increase of dehydrogenase activities at elevated Ni2+ concentrations when cellulase and protease activities were similar in all test groups. It is suggested that Ni2+ addition was mainly dependent on the methanogenic stage. After the start-up stage, the impact of Ni2+ addition on biogas production was mainly dependent on its effect on cellulase activities, rather than protease or dehydrogenase activities.

In the past decades, a novel strategy has arisen, as required by time, to get a rational production of biogas from contaminated biomass, which may be, on purpose, harvested from contaminated soil phytoremediation process. The present review focuses on the possibility and potential of utilizing the agricultural residues generated during phytoremediation for production of biogas. As a general result of the studies compiled in this review, the harvested biomass can subsequently be utilized for the winning of biogas, and it provides a solution of waste disposal for phytoremediation technology. According to the analysis of previous results, not more than 1 mg/L of cadmium in fermenters shows promoting or at least no inhibitory effect on cumulative biogas yields. This strategy is promising for dealing with both environmental and energy problems in spite of many challenges in the coming future.

Anaerobic fermentation is considered as a cost-effective way of biomass waste disposal. Chromium (Cr) is one of the heavy metals that often been blamed for unsatisfactory operation or failure of anaerobic fermentation. The impact of Cr (added as K2Cr2O7) on mesophilic anaerobic fermentation of Phragmites australis straw and cow dung was demonstrated by investigating the biogas properties, process stability, substrate degradation and enzyme activities during the fermentation process. The results showed that 30, 100 and 500 mg/L Cr6+ addition increased the cumulative biogas yields by up to 19.00%, 14.85% and 7.68% respectively, and brought forward the daily biogas yield peak. Meanwhile, the methane (CH4) content in the 30 (52.47%) and 100 (40.57%) mg/L Cr6+-added groups were generally higher than the control group (37.70%). Higher pH values (close to pH 7) and lower oxidation-reduction potential (ORP) values in the Cr6+-added groups after the 15th day indicated the better process stability compared to the control group. Taking the whole fermentation process into account, the promoting effect of Cr6+ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, the higher coenzyme F420 activities and the efficient generation of CH4. These results demonstrate that an appropriate addition of Cr6+ could enhance the anaerobic fermentation which support the regulations utilizing of the Cr6+ contaminated biowaste.

This study was performed to assess morphological responses, biomass yield and bioenergy potential during the entire growth period (167 days) of sweet sorghum with different Cd stress, i.e. 0, 1, 5, 10, 30, 50, and 100 mg/kg in pot experiments. The results showed that the morphological characteristics of sweet sorghum, i.e. shoot length, leaf length and leaf numbers were not significantly changed with the Cd concentration ≤ 5 mg/kg in the soil. The aerial biomass of sweet sorghum treated by 10 mg/kg Cd was 82.71% of the control test, and was reduced to 70.67% when the Cd concentration in the soil was increased to 30 mg/kg. The root was the main location site of Cd in the sweet sorghum, thus the reutilization of the aerial biomass would not be seriously influenced. The predicted ethanol yields was 3.65, 3.05, 3.14, 2.69, 1.15, and 0.41 t/y/hm2 for 1, 5, 10, 30, 50, and 100 mg/kg Cd concentration, respectively. Due to its high biomass production and Cd accumulation capacity, sweet sorghum is a good candidate...

Arabidopsis plants acclimated to chronic periodic high light stress attained reproductive phase earlier and showed higher productivity than plants grown under low light., This work examined the long-term effects of periodic high light stress on photosynthesis, morphology, and productivity of low-light-acclimated Arabidopsis plants. Significant photoinhibition of Arabidopsis seedlings grown under low light (100 μmol photons m−2 s−1) was observed at the beginning of the high light treatment (three times a day for 30 min at 1800 μmol photons m−2 s−1). However, after 2 weeks of treatment, similar photosynthesis yields (Fv/Fm) to those of control plants were attained. The daily levels of photochemical quenching measured in the dark (qPd) indicated that the plants recovered from photoinhibition within several hours once transferred back to low light conditions, with complete recovery being achieved overnight. Acclimation to high light stress resulted in the modification of the number, structure, and position of chloroplasts, and an increase in the average chlorophyll a/b ratio. During ontogenesis, high-light-exposed plants had lower total leaf areas but higher above-ground biomass. This was attributed to the consumption of starch for stem and seed production. Moreover, periodic high light exposure brought forward the reproductive phase and resulted in higher seed yields compared with control plants grown under low light. The responses to periodic high light exposure of mature Arabidopsis plants were similar to those of seedlings but had higher light tolerance.

The effect of copper (added as CuCl2) on the anaerobic co-digestion of Phragmites straw and cow dung was studied in pilot experiments by investigating the biogas properties, process stability, substrate degradation and enzyme activities at different stages of mesophilic fermentation. The results showed that 30 and 100 mg/L Cu2+ addition increased the cumulative biogas yields by up to 43.62 and 20.77% respectively, and brought forward the daily biogas yield peak, while 500 mg/L Cu2+ addition inhibited biogas production. Meanwhile, the CH4 content in the 30 and 100 mg/L Cu2+-added groups was higher than that in the control group. Higher pH values (close to pH 7) and lower oxidation–reduction potential (ORP) values in the Cu2+-added groups after the 8th day indicated better process stability compared to the control group. In the presence of Cu2+, the degradation of volatile fatty acids (VFAs) and other organic molecules (represented by chemical oxygen demand, COD) generated from hydrolysis was enhanced, and the ammonia nitrogen (NH4 +-N) concentrations were more stable than in the control group. The contents of lignin and hemicellulose in the substrate declined in the Cu2+-added groups while the cellulose contents did not. Neither the cellulase nor the coenzyme F420 activities could determine the biogas producing efficiency. Taking the whole fermentation process into account, the promoting effect of Cu2+ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, and the generation of CH4 from VFA.

Acid-activated sintering process red mud (ASRM) was investigated as an adsorbent for removal of two cationic dyes, malachite green (MG) and crystal violet (CV), from aqueous solution. The adsorption behaviors of dyes were studied in batch experiments as a function of contact time, pH value, initial dye concentration and temperature. The solution with pH higher than 3.2 was favorable for the adsorption of MG and CV on the ASRM. Adsorption data fitted better using the Langmuir isotherm, and the calculated maximum adsorption capacities were 336.4 mg/g and 60.5 mg/g for MG and CV at 25 °C, respectively. The analysis of the thermodynamic parameter, Δ H , indicated that the adsorption process of MG was endothermic, whereas that of CV was exothermic. The kinetic data were better described by pseudo-second order kinetic model. These results indicated that ASRM exhibited good adsorption ability and can be used as an attractive adsorbent for the removal of cationic dyes, especially MG.

Anaerobic fermentation is considered as a cost-effective way of biomass waste disposal. However, the compound heavy metals contained in the biomass may induce complex effects on anaerobic fermentation, which limit the utilization of metal-contaminated biowaste. In this study, the impacts of Cd and Zn addition on biogas properties, process stability, substrate biodegradation, enzyme activity, and microbial properties were studied. The results showed that the addition of Cd together with Zn (Cd+Zn) increased the maximum daily and cumulative biogas yields, and brought forward the gas production peak compared with the Cd-added group. Taking the whole fermentation process into account, the promotion effects of adding Zn into the Cd-containing fermentation system on biogas yields were mainly attributable to better process stability, higher average NH4+-N concentration in the later stage of fermentation, reduced COD (p &lt, 0.05), and increased biodegradability of lignocelluloses (p &lt, 0.01), especially cellulose (p &lt, 0.05) and lignin (p &lt, 0.01). Meanwhile, the addition of Zn promoted the coenzyme M activity (p &lt, 0.05), and increased the absolute abundance of Methanothermobacter. The bacteria communities during the fermentation process were responsible for the degradation of lignocelluloses. The results demonstrated that the addition of appropriate Zn into the Cd-containing fermentation system enhanced the efficiency of anaerobic fermentation and utilization of biowaste.

The effect of nickel ions on the anaerobic digestion ofphragmites australisand cow dung were investigated in batch experiments. Five levels of nickel ions were set as 0, 0.2, 0.8, 1.4 and 2.0 mg Ni/L. The results indicated that anaerobic digestion started on about 3rdday 26 days of anaerobic digestion, the highest cumulative biogas was 32.70 mL/g·TS-1when nickel concentration was 0.8 mg Ni/L. The nickel ions in certain concentration range significantly affected biogas production rate, and effectively shorten reactor startup period. Biogas which was produced fromphragmitescombined with cow dung provided a new insight for bioenergy production whose? process can be promoted by nickel ions addition.

The adsorption behaviors of ammonium from aqueous solutions were investigated for three solid coal wastes, slag, honeycomb-cinder and coal gangue. The ammonium sorption processes were well modeled by the pseudo second-order model (R 2 > 0.99). The experimental data were fitted to both the Langmuir model and the Freundlich model, with the Langmuir model better representing the data. The maximum ammonium sorption capacities calculated from the Langmuir model were 3.1, 5.0 and 6.0 mg/g for the slag, honeycomb-cinder and coal gangue samples, respectively. The pH value of the solution affected the ammonium removal, and the higher uptakes found in either neutral or alkaline conditions for the three materials. The thermodynamic parameters, ΔH, were calculated to be 29.75, 25.21 and 17.91 kJ/mol for the SL, HC and CG samples, respectively, with the positive values indicating that the ammonium sorption processes were endothermic. Based on the results, it can be concluded that coal gangue may have more potential for being used as a sorbent for the ammonium removal from wastewater among the three coal by-products.

The adsorption behavior of methylene blue (MB) dye from aqueous solutions onto sintering process red mud (SRM) and its hydrochloric acid-activated product (ASRM) was investigated in a batch system. The results showed that equilibrium was reached after a contact time of 60 min for both adsorbents. The optimum pH for MB adsorption was 10.0 for SRM and 9.0 for ASRM. The removal of the dye increased with increasing initial dye concentration and adsorbent amount, whereas it decreased with increasing ionic strength. The effect of temperature on adsorption was also investigated; the adsorption of MB on SRM and ASRM samples was spontaneous and followed an endothermic process, based on the analysis of thermodynamic parameters, including enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) changes. The adsorption of MB followed pseudo-second-order kinetics, with a coefficient of correlation ⩾ 0.9999. The adsorption process was better described by the Langmuir isotherm model than Freundlich model, with a maxim...

The cadmium (Cd) stress to xylophyta Vitex negundo var. heterophylla including growth responses and Cd accumulation in plant was investigated in pot experiment with different Cd concentrations. The result indicated that the shoot length, shoot diameter and root diameter as well as the biomass of organs were obviously decreased when Cd was 50 mg/kg. 100 mg/kg Cd caused the chlorosis of the leaf. The accumulated ability of Cd in Vitex negundo var. heterophylla in turn was root > leaf > shoot. This plant presented efficient ability in removing the Cd from the contaminated soil when initial Cd in the soil was 20 mg/kg.

In this study, the morphological responses of wheat to Cd during the whole growth stage were investigated in pot experiment with substrates containing 0, 1, 5, 10, 50 and 100 mg Cd/kg soil. The results showed that wheat was moderately tolerant to Cd stress, and the most sensitive endpoint to Cd toxicity was tiller number. The seed germination was not effected by Cd at all concentrations. The No Observed Adverse Effect Concentration (NOAEC) was 10 mg Cd/kg, and the Low Observed Adverse Effect Concentration (LOAEC) was 50 mg Cd/kg for the wheat.

Cadmium’s (Cd) impact on the photosynthetic activities of energy plant maize was investigated in pot experiments containing different Cd contaminated levels during the whole growth period. The results showed that the ability of photosynthesis was not obviously inhibited by elevated Cd stress. Net photosynthetic rate (NPR) was decreased with the growth of maize, while transpiration rate (TR), stomatal conductance (gs>) and intercellular CO2 concentration (Ci) were enhanced in heading period, then decreased in maturity period. The change of fluorescence quenching and photosystem II (PSII) efficiency was consistent with NPR. Thus, the influence of photosynthesis under Cd stress mainly depended on the response of PSII reaction centre.

The presence of heavy metals influences the efficiency of anaerobic fermentation and results in the variations of the relationships among the fermentation parameters. In this study, the impacts of elevated Cu2+ concentrations on relationships among biogas properties, process stability, substrate biodegradation, and enzyme activity were analysed by Pearson correlation analysis based on the experimental data of a mesophilic anaerobic co-fermentation with mixed acid pretreated Phragmites australis straw and raw cow dung as feedstocks. The results showed that in the absence of Cu2+, the cumulative biogas yields were positively related to pH values (0.780, p

The effect of ferrous (added as FeCl2) on the anaerobic co-digestion of Phragmites straw and cow dung was studied by investigating the biogas properties, pH values, organic matter degradation (COD) and enzyme activities (cellulase, protease and dehydrogenase) at different stages of mesophilic fermentation. The results showed that Fe(2+) addition increased the cumulative biogas yields by 18.1 % by extending the peak period with high daily biogas yields. Meanwhile, the methane (CH4) contents in the Fe(2+) added groups were generally higher than the control group before the 15th day. The pH values were not significantly impacted by Fe(2+) concentrations during the fermentation process. The COD concentrations, cellulase, protease and dehydrogenase activities varied with the added Fe(2+) concentrations and the stages of the fermentation process. At the beginning stage of fermentation (4th day), Fe(2+) addition increased the biogas production by improving the cellulase and dehydrogenase activities which caused a decline in COD. At the peak stage of fermentation (8th day), Fe(2+) addition enhanced the cellulase and protease activities, and resulted in lower COD contents than the control group. When the biogas yields decreased again (13th day), the COD contents varied similar with the protease and dehydrogenase activities, whilst cellulase activities were not sensitive to Fe(2+) concentrations. At the end of fermentation (26th day), Fe(2+) addition decreased the cellulase activities, led to lower COD contents and finally resulted the lower biogas yields than the control group. Taking the whole fermentation process into account, the promoting effect of Fe(2+) addition on biogas yields was mainly attributed to the extension of the gas production peak stage and the improvement of cellulase activities.

The present study proposes a novel strategy to get a rational production of biogas of the biomass residues from phytoremediation. This study investigates physiological responses, cadmium (Cd) accumulation and biogas production from canola, oat and wheat in pot and batch experiments. The results indicate that (1) aerial biomasses for canola, oat and wheat were enhanced by 5 mg Cd/kg soil by 19.41%, 8.78% and 3.38%, and the upper limit of Cd concentration that canola, oat and wheat can tolerate for aerial biomass production were 50, 10 and 10 mg Cd/kg soil; (2) canola accumulates more Cd than oat and wheat in its aerial parts; (3) cumulative biogas yields were 159.37%, 179.23% and 111.34% of the control when Cd in the shoot were 2.00 ± 0.44, 39.80 ± 1.25 and 6.37 ± 0.15 mg Cd/kg biomass for canola, oat and wheat. Phytoremediation in cooperation with bioenergy production provide new insights for both soil remediation and energy research.

The utilization of lignocelluloses for biogas production is limited for several aspects, and an efficient pre-treatment is essential to increase the enzyme accessibility of cellulose. This research focused on the mechanism of biogas production and biodegradation properties under the treatments with different acid agents, including sulfuric acid (H2SO4), acetic acid (CH3COOH), and phosphoric acid (H3PO4). The H3PO4 pretreated corn stover was then co-digested with cow dung in a pilot test to investigate the performance of acid pretreatment in practice. The results showed that the main compositions of corn stover were cellulose, hemicellulose, and lignin, and their proportions in the corn stovers were increased after the acid pretreatments. This hence increased the final biogas yields (up to 40.75%), methane content, and promoted the biodegradation process. More significantly, the acid pretreatments delayed the appearance of the peak value of the biogas yield for 3 to 8 days depending on the acid concentrations. This study proposed that the dilute weak acid pretreatment, especially H3PO4 pretreatment, efficiently enhanced the biogas production by increasing the degradation of hemicellulose. Further on, the H3PO4 pretreatment also improved the stability of fermentation, which would benefit the biogas generation in practice. This research contributes to a better understanding of the mechanism of acid influence on enhancing the biogas generation and substrate biodegradation, and provides pratically sound guidance for reclamation of lignocellulosic materials.