Co-digestion Of Grass Research Articles

Anaerobic co-digestion of grass, alfalfa, and red clover for methane production and the kinetic analysis

The residual of perennials in landscape trimming and agricultural interval planting are produced massively, and they can provide an innovative way to increase anaerobic digestion efficiency via co-digestion process. In this study, the bio-methane potential (BMP) of different perennial crops (grass, alfalfa, and red clover) in various feedstock concentrations based on volatile solid (VS) and the kinetic analysis of the co-digestion process were investigated. The results showed that grass and legumes reached the highest methane yield at 5 VS/L and 20 VS/L, respectively. Co-digestion of grass and perennials had better methane production of 338 mL/g VS, which is 9.1% higher than mono-digestion. Further analysis demonstrated that VS removal efficiency of mono-legumes digestion was below 60%, while co-digestion of grass and legumes can improve VS removal efficiency dramatically. Volatile fatty acids (VFAs) and ammonia in the digestate accumulated at 40 VSadded/L. Additionally, kinetic analysis was employed to predict and evaluate the performance of anaerobic digestion, with the Cone model showing the best fitting curve.

Co-Digestion of Kitchen Waste with Grass and Leaves after Hyperthermophilic Pretreatment for Methane and Hydrogen Production

The study investigated co-digestion batch experiments using kitchen waste (KW) and garden waste (GW) collected from individual households. Grass and leaves were first subjected to a 3-day hyperthermophilic pretreatment at 70 °C and 80 °C and then co-digested with kitchen waste at 35 °C and 55 °C. The hyperthermophilic pretreatment resulted in the solubilization of organic material with the release of fatty acids, whereas the biogas yield was negligible. In the second stage, the greatest methane yield of 387 NmL/gVS was achieved for the mono-digestion of leaves, whereas the co-digestion of grass with 50% KW gave the highest hydrogen production of 88 NmL/gVS. Considering the overall process performance, the best operating conditions were established using a 3-day hyperthermophilic pretreatment at 70 °C, followed by co-digestion at 55 °C in the second stage for the mixture of 25% garden waste with 75% KW.

Biogas Production from Co-Digestion of Grass with Food Waste

Management of grasslands in Ghana has become so poor that most rural communities result in bushfires that cause a lot of environmental challenges. Grass could be used for biogas generation. This study investigated the effect of grass and food waste co-digestion on the biogas yield and clarified how the addition of grass enhances the AD performance. Grass (GR) mixed with the co-substrate food waste (FW) was then evaluated under anaerobic conditions for the production of biogas (methane). Five laboratory-scale reactors, R1 (100% FW, 0% GR), R2 (75% FW, 25% GR), R3 (50% FW, 50% GR), R4 (25% FW, 75% GR) and R5 (0% FW, 100% GR) were set up with different proportions of grass and food waste which had 8% total solid concentration. Digestion was carried out for twenty (20) days at room temperature, 35&#176C ± 2&#176C. The biogas yield in the R1, R2, R3, R4, R5 was 805, 840, 485, 243 and 418 mL respectively. Food waste only produced 805 mL and grass only produced 418 mL of biogas. Food waste only produced 50% more biogas than grass. However, co-digestion at 75% FW, 25% resulted in 6% more biogas than food waste only.

Co-Digestion of Napier Grass and Its Silage with Cow Dung for Bio-Hydrogen and Methane Production by Two-Stage Anaerobic Digestion Process

The objective of this study was to efficiently utilize the napier grass and its silage to produce bio-hydrogen and methane by a two-stage process in batch mode. First, the production of hydrogen from a co-digestion of grass with cow dung and silage with cow dung by Clostridium butyricum Thailand Institute of Scientific and Technological Research (TISTR) 1032 was conducted. The results indicated that bio-hydrogen production by C. butyricum TISTR 1032 gave a higher hydrogen yield (HY) than without C. butyricum addition. The HY of 6.98 and 27.71 mL H2/g-Volatile solidadded (VSadded), were obtained from a co-digestion of grass with cow dung and silage with cow dung by C. butyricum, respectively. The hydrogenic effluent and solid residue left over after hydrogen fermentation were further used as substrates for methane production (Batch I). Methane yield (MY) from hydrogenic effluent of grass with cow dung and silage with cow dung were 169.87 and 141.33 mL CH4/g-CODadded (COD: chemical oxygen demand), respectively. The maximum MY of 210.10 and 177.79 mL CH4/g-VSadded, respectively, were attained from solid residues left over after bio-hydrogen production pretreated by enzyme (cellulase cocktail) and alkali (NaOH). Afterward, solid residue left over after methane production (Batch I) was used as the substrate for methane production (Batch II). A maximum MY of 370.39 and 370.99 mL CH4/g-VSadded were achieved from solid residue repeatedly pretreated by alkaline plus enzyme, respectively. The overall energy yield in the two-stage bio-hydrogen and methane production process was derived from a bio-hydrogen production, a methane production from hydrogenic effluent, methane production of pretreated solid residue (Batch I) and methane production of repeatedly pretreated solid residue (Batch II), which yielded 480.27 and 204.70 MJ/g-VSadded, respectively.

Co-Digestion of Napier Grass and Its Silage with Cow Dung for Methane Production

Methane production from co-digestion of grass with cow dung and silage with cow dung was conducted by a bioaugmentation technique. For self-fermentation, maximum methane yield (MY) of 176.66 and 184.94 mL CH4/g-VSadded were achieved at a ratio of grass to cow dung and silage to cow dung of 1:1, respectively. A higher maximum MY of 179.59 and 208.11 mL CH4/g-VSadded was obtained from co-digestion of grass with cow dung and silage with cow dung bioaugmented with anaerobic sludge at a ratio of 3:1. The solid residue left over after co-digestion at a ratio of 3:1 was pretreated by alkaline plus enzyme before used to produce methane and a maximum MY of 333.63 and 301.38 mL CH4/g-VSadded, respectively, was achieved. Overall power generated from co-digestion of grass with cow dung plus pretreated solid residues and co-digestion of silage with cow dung plus pretreated solid residues were 0.0397 and 0.007 watt, respectively.

Cattle feed or bioenergy? Consequential life cycle assessment of biogas feedstock options on dairy farms

AbstractOn‐farm anaerobic digestion (AD) of wastes and crops can potentially avoid greenhouse gas (GHG) emissions, but incurs extensive environmental effects via carbon and nitrogen cycles and substitution of multiple processes within and outside farm system boundaries. Farm models were combined with consequential life cycle assessment (CLCA) to assess plausible biogas and miscanthus heating pellet scenarios on dairy farms. On the large dairy farm, the introduction of slurry‐only AD led to reductions in global warming potential (GWP) and resource depletion burdens of 14% and 67%, respectively, but eutrophication and acidification burden increases of 9% and 10%, respectively, assuming open tank digestate storage. Marginal GWP burdens per Mg dry matter (DM) feedstock codigested with slurry ranged from –637 kg CO2e for food waste to +509 kg CO2e for maize. Codigestion of grass and maize led to increased imports of concentrate feed to the farm, negating the GWP benefits of grid electricity substitution. Attributing grass‐to‐arable land use change (LUC) to marginal wheat feed production led to net GWP burdens exceeding 900 kg CO2e Mg−1 maize DM codigested. Converting the medium‐sized dairy farm to a beef‐plus‐AD farm led to a minor reduction in GWP when grass‐to‐arable LUC was excluded, but a 38% GWP increase when such LUC was attributed to marginal maize and wheat feed required for intensive compensatory milk production. If marginal animal feed is derived from soybeans cultivated on recently converted cropland in South America, the net GWP burden increases to 4099 kg CO2e Mg−1 maize DM codigested – equivalent to 55 Mg CO2e yr−1 per hectare used for AD‐maize cultivation. We conclude that AD of slurry and food waste on dairy farms is an effective GHG mitigation option, but that the quantity of codigested crops should be strictly limited to avoid potentially large international carbon leakage via animal feed displacement.