Anaerobic Digestion Of Residues Research Articles

Evaluation of in vitro digestibility of Aspergillus oryzae fungal biomass grown on organic residue derived-VFAs as a promising ruminant feed supplement

BackgroundAs demand for high quality animal feed continues to raise, it becomes increasingly important to minimize the environmental impact of feed production. An appealing sustainable approach to provide feed fractions is to use organic residues from agro-food industry. In this regard, volatile fatty acids (VFAs) such as acetic, propionic and butyric acids, derived from bioconversion of organic residues can be used as precursors for production of microbial protein with ruminant feed inclusion potential. This study aims to investigate the in vitro digestibility of the Aspergillus oryzae edible fungal biomass cultivated on VFAs-derived from anaerobic digestion of residues. The produced fungal protein biomass, along with hay clover silage and rapeseed meal were subjected to various in vitro assays using two-stage Tilley and Terry (TT), gas, and bag methods to evaluate and compare its digestibility for application in ruminant feed.ResultsThe produced fungal biomass contained a higher crude protein (CP) (41%–49%) and rather similar neutral detergent fiber (NDF) (41%–56%) compared to rapeseed meal. The rumen in vitro dry matter digestibility (IVDMD) of the fungal biomass in the TT method ranged from 82% to 88% (statistically similar to that of the gas method (72% to 85%)). The IVDMD of fungal biomass were up to 26% and 40% greater than that of hay clover silage and rapeseed meal, respectively. The type of substrate and bag method had pronounced effect on the fermentation products (ammonium-N (NH4+-N), total gas and VFAs). Fungal biomass digestion resulted in the highest release of NH4+-N (340–540 mg/L) and the ratio of acetate to propionate ratio (3.5) among subjected substrates.ConclusionThe results indicate that gas method can be used as a reliable predictor for IVDMD as well as fermentation products. Furthermore, the high IVDMD and fermentation product observed for Aspergillus oryzae fungal biomass digestion, suggest that the supplementation of fungal biomass will contribute to improving the rumen digestion by providing necessary nitrogen and energy to the ruminant and microbiota.

Sustainable bioconversion of potato peel wastes into ethanol and biogas using organosolv pretreatment

Potato processing industries generate considerable amounts of residues, i.e., potato peel wastes (PPW). Valorization of PPW for bioethanol and biogas production via a biorefining process was investigated in this study. Organosolv pretreatment was performed on the PPW using 50–75% (v/v) ethanol solution at 120–180 °C with/without the presence of 1% (w/w) H2SO4 (as a catalyst). After the pretreatment, the solvent, i.e., ethanol, was recovered by distillation. Catalyzed organosolv pretreatment using 50% (v/v) ethanol at 120 °C followed by enzymatic hydrolysis resulted in a high hydrolysate yield of 539.8 g glucose/kg dry PPW that was successfully fermented to 224.2 g ethanol/kg dry PPW. To recover more energy, the liquid fraction of the pretreatment remained after solvent recovery and the unhydrolyzed solids that remained from the enzymatic hydrolysis were anaerobically digested. From each kg of dry PPW, the anaerobic digestion produced 57.9 L biomethane. Thus, the biorefinery comprising ethanolic organosolv pretreatment, solvent recovery, enzymatic hydrolysis, ethanolic fermentation, and anaerobic digestion of residues was produced 8112 kJ energy per kg of dry PPW.

Hydrothermal pretreatment: An efficient process for improvement of biobutanol, biohydrogen, and biogas production from orange waste via a biorefinery approach

Orange waste (OW), an abundant and severe globally environmental treat, was used for biobutanol and biohydrogen production emploing acetone-butanol-ethanol (ABE) fermentation through a biorefinery process. The solvent yield from untreated OW was insufficient; thus, the substrate was subjected to hydrothermal pretreatment before hydrolysis. The pretreatment at 140 ℃ for 30 min resulted in the solid with the highest yield of hydrolysis and fermentation. Moreover, the anaerobic digestion of hydrolysis residue produced appreciable amounts of biomethane. However, the pretreatment liquor was not fermentable; thus, it was detoxified by overliming for 24 h at 30 ℃ and then fermented. Overall, this sustainable biorefinery, based on pretreatment without any additional chemical agent, hydrolysis of pretreated solids, detoxification of pretreatment liquor, ABE fermentation, and anaerobic digestion of residues, produced 42.3 g biobutanol, 33.1 g acetone, 13.4 g ethanol, 104.5 L biohydrogen, and 28.3 L biomethane per kg of OW that contained 4560 kJ energy.

Beyond ruminants: discussing opportunities for alternative pasture uses in New Zealand

The New Zealand government has set ambitious goals for primary sector growth and of zero net carbon emissions by 2050. This presents an opportunity and obligation to develop new ideas for grassland production systems to increase export value and generate new job opportunities, while reducing environmental impacts. The aim of this paper is to draw on recent research in Europe to investigate some of the alternative and complementary uses for pasture as a feedstock for a green biorefinery. A biorefinery is a facility, or a series of processes, that convert biomass into a spectrum of value-added products. For example, protein can be extracted mechanically from green biomass once harvested. The residual fibre fraction could be used as a low-nitrogen feed for ruminants to reduce urinary nitrogen, while the liquid protein fraction could be processed to make it suitable for mono-gastric or human consumption. Enzymes can promote protein extraction and controlled conversion of insoluble plant fibres and oligosaccharides to foster gut-health promoting prebiotic food ingredients. Anaerobic digestion of residues can then be used to create energy and soil-improving products. Research and demonstration of these approaches in practice, along with the results of feasibility studies, will be required to see which of these opportunities is a good fit for New Zealand pasture systems.

Bioremediation of chromium complex dyes and treatment of sludge generated during the process

Bioremediation of chromium complex dyes in synthetic solutions and actual effluent was performed using growing Aspergillus tamarii in batch and continuous bioreactors. Maximum removal of color (90.00 ± 0.20 and 74.00 ± 0.10%) and chromium (94.00 ± 0.10 and 77.50 ± 0.10%) was obtained from synthetic solutions (100 mg/L) of acid brown 45 and acid blue 158 dyes, respectively in batch mode. Optimization of process parameters such as initial concentration of dye, pH and time was performed using response surface methodology (RSM). Biosorption, bioaccumulation and biodegradation of the dyes during bioremediation were supported by TEM and GC-MS analyses. Maximum removal of color (64.50 ± 0.10 and 45.00 ± 0.10%) and chromium (67.00 ± 0.10 and 49.00 ± 0.10%) was obtained at 220 h HRT using solutions (100 mg/L) of acid brown 45 and acid blue 158 dyes, respectively in continuous mode. The removal of color (86.00 ± 0.10 and 65.00 ± 0.20%) and chromium (100.00 ± 0.10 and 81.00 ± 0.10%) was observed in batch and continuous modes, respectively using actual effluent. The lower removal values were obtained using desorbed and dead biomass as compared to actively growing biomass. Phytotoxicity test was conducted using seeds of Cicer arietinum to examine the toxic effect of dye solution before and after bioremediation. Anaerobic digestion of residues (after bioremediation of dyes) indicated maximum methane production of 41.00 ± 0.20% on 16th day of operation.

What is the resource of second generation gaseous transport biofuels based on pig slurries in Spain?

Biomethane produced through anaerobic digestion of residues is classified as a second generation gaseous biofuel. A technique employed in Spain to deal with pig slurry is drying, using the heat from natural gas combined heat and power (CHP) systems. This paper examines production of biomethane from pig slurry. Two scenarios are investigated: co-digestion of pig slurry with glycerine (a by-product of biodiesel production) and co-digestion of pig slurry with the organic fraction of municipal solid waste (OFMSW). Both scenarios include for ca. 10Mt of pig slurry each year. A combination of the two scenarios is sufficient to provide for 1.4% of energy in transport by 2020. The EU Renewable Energy Directive allows a double weighting to biofuels produced from residues when assessing renewable energy supply in transport (RES-T) targets for 2020. Thus the scenarios allow for 2.8% RES-T. The biomethane is sufficient to run 15,300 city buses or substitute for natural gas in 632,000 houses (8.7% of houses connected to the gas grid). The proposed biomethane industry would generate a fuel of similar sale price as diesel, allow for savings in the range 1046–1272kt CO2eq in transport fuel emissions and create more than 6000 jobs.

An economic, sustainability, and energetic model of biodiesel production from microalgae

A new process evaluation methodology of microalgae biodiesel has been developed. Based on four evaluation criteria, i.e. the net energy ratio (NER), biodiesel production costs, greenhouse gases (GHG) emission rate and water footprint, the model compares various technologies for each step of the process, from cultivation to oil upgrading. An innovative pathway (hybrid raceway/PBR cultivation system, belt filter press for dewatering, wet lipid extraction, oil hydrotreating and anaerobic digestion of residues) shows good results in comparison to a reference pathway (doubled NER, lower GHG emission rate and water footprint). The production costs are still unfavourable (between 1.94 and 3.35€/L of biodiesel). The most influential parameters have been targeted through a global sensitivity analysis and classified: (i) lipid productivity, (ii) the cultivation step, and (iii) the downstream processes. The use of low-carbon energy sources is required to achieve significant reductions of the biodiesel GHG emission rate compared to petroleum diesel.

Anaerobic digestion of residues from production and refining of vegetable oils as an alternative to conventional solutions

The purpose of this work was to study the anaerobic digestion of by-products generated during the production and refining of oil with the objective of proposing an alternative solution (methanisation) to the conventional solutions while reducing the energy consumption of fossil origin on refinery sites. The production of sunflower oil was taken as example. Glycerine from the production of biodiesel was also included in this study. The results show that glycerine has a high potential for methanisation because of its high methane potential (465 ml CH4/g VS) and high metabolization rates (0.42 g VS/g VSS.d). The use of oil cake as substrate for anaerobic digestion is not interesting because it has a low methane potential of 215 ml CH4/g VS only and because it is easily recovered in animal feed. Six residues have quite a high methane potential (465 to 850 ml CH4/g VS) indicating a good potential for anaerobic digestion. However, they contain a mixture of rapidly and slowly biodegradable organic matter and the loading rates must remain quite low (0.03 to 0.09 g VS/g VSS.d) to prevent any accumulation of slowly biodegradable solids in the digesters.

Anaerobic Digestion and Methane Generation Potential of Rose Residue in Batch Reactors

In the study, anaerobic digestion of residues from rose oil industry was investigated by using a laboratory scale completely mixed batch reactor in volume of 10 L and 4 small reactors in volume of 400 mL. Ten liters reactor isolated with a water jacket and 0.4 L reactors settled into a water bath were operated at 35 ± 1°C. The study supplies biochemical methane potential of hydrolyzed and original residues. Experimental results showed that hydrolyzed rose residue produced a bit more methane than original residue. Methane production results were analyzed with first-order and Chen&Hashimoto's models, and Chen&-Hashimoto's model was found to be more suitable than first-order kinetic model.

Fuel gas production from animal residue part II. an economic assessment

A mathematical model description of anaerobic digestion of animal residues was developed, taking into account material and energy balances, kinetics, and economics of the process. The model had the flexibility to be applicable to residues from any size or type of animal husbandry operation. A computer program was written for this model incorporating a procedure for process optimization, based on minimum unit gas cost, with the optimization variables being digester temperature, retention time, and influent volatile solids concentration. The computer program was used to determine the optimum baseline process conditions and economics for the fuel gas production via anaerobic digestion of residues from a 10,000 head environmental beef feedlot. This feedlot - at the conditions for minimum unit gas cost - was calculated to produce 8500 m 3 (300 MCF)/day of methane at a cost of $4.90/GJ or $0.183/m' ($5.17/MCF [CH 4]), with a total capital requirement of $1,165,000, a total capital investment of $694,000, and an annual average net operating cost of $370,000. No credit for possible refeed of digester effluent was included but a cost of $2.78/Mg ($2.50/ton) for the raw manure was incorporated. The major contributions to this unit gas cost were due to labor (37%), raw manure (11%), power for gas compression (10%), and digester cost (13%). A sensitivity analysis of the unit gas cost to changes in the major contributions to unit gas cost was performed, and the results of this analysis indicated areas in the anaerobic digestion system design where reasonable improvements may be expected so as to produce gas at a more economically feasible cost. This sensitivity analysis included the effects on unit gas cost of feedlot size and type, digester type, digester operating conditions, and economic input data. For example, a 40,000 head environmental feedlot was computed to produce methane for $1.42/GJ or $0.050/m 3 ($1.50/MCF), using a continuously stirred tank reactor digester and taking a credit for the digester effluent as refeed.