EA037925B1 - Biogas production method - Google Patents

Abstract

The disclosed method is realized using organic wastes, activated sludge and residual duckweed biomass. The method is characterized in that residual biomass of duckweed is added to organic wastes in ratio 42.5:42.5:15 and active sludge (3% solution). To increase output of biogas with maximum content of methane anaerobic fermentation is carried out at a temperature of 401°C.

Description

The invention relates to methods for processing organic waste using the residual biomass of duckweed in biotechnological processes in order to obtain biogas with an increased content of methane.

Anaerobic digestion for biogas production is a cheap and affordable way to generate energy, as well as utilization of biogenic waste. This prevents methane and carbon dioxide from entering the atmosphere. Currently, a fairly large number of biogas production technologies have been developed and are being applied, based on the use of various options for temperature conditions, humidity, concentration of microbial mass, duration of the reaction, etc. However, today the question of finding the most effective, cheap and affordable ways to intensify the process of obtaining biogas remains relevant.

There is a method for producing biogas (patent No. RU 2458868), the authors of which propose to obtain biogas from organic waste with the addition of crimson amaranth phytomass and with the addition of activated sludge 1: 1 at the rate of 2-3 wt.%, Followed by ultrasound treatment with a frequency of 22 kHz and an intensity 6-8 W / cm for 4-8 minutes. The above method allows you to increase the biogas yield up to 30.23%. The multistage process complicates and increases the cost of biogas production.

A known method for producing biogas, which uses aquatic plant materials. Duckweed, an aquatic plant, is a source of energy and nutrients when feeding farm animals. Duckweed contains volatile substances, has a moisture content, ash content and contains carbon, hydrogen and nitrogen. It is assumed that the enrichment of duckweed with iron increases the yield of biogas. Clark, P. B. and Hillman, P. F. (1996) Enhancement of anaerobic digestion using duckweed (Lemna minor) enriched with iron, Water and Environment Journal, vol. 10, no. 2, pp. 92-95 iron concentration ranged from 0 to 400 mg. The highest biogas yield was obtained with the addition of duckweed, enriched with 400 mg of iron, and corresponds to 1050 ml of biogas. When growing duckweed in wastewater, the iron content in plants should be controlled at a certain level necessary to intensify the biogas production process.

In the way (Dipti Yadava, Lepakshi Barboraa, Deep Boraa, Sudip Mitrab, Latha Rangana, Pinakeswar Mahanta An assessment of duckweed as a potential lignocellulosic feedstock for biogas production // International Biodeterioration & Biodegradation September 2016 1-7 DOI: 10.1016 / j.ibiod .2016.09.007), which is selected as a prototype, it is proposed to use the joint use of cattle manure and duckweed. A preliminary analysis of the properties of duckweed was carried out, which showed that volatile substances are 84.24 ± 0.2% with a lignin content of 12.2%, which is very favorable for biogas production.

Fermentation was carried out together with manure and duckweed at a temperature of 37 ° C for 55 hours.The total production of biogas for the ratios: 100, (90:10), (75:25) and (50:50) is 11620, 305, 11695 and 12070 ml biogas, which indicates that duckweed can be a potential lignocellulosic raw material when co-digested with cattle manure in an optimal ratio of 1: 1. The methane content in biogas during the joint fermentation of raw materials is comparable to biogas from one cattle manure. The disadvantage of this method is the use of duckweed containing valuable components as a raw material.

The technical problem to be solved by the present invention is to create a method for producing biogas from organic waste with an increased content of methane in biogas.

The technical result is achieved by a method for producing biogas from organic waste, in which a 3% solution of activated sludge and residual duckweed biomass are added to organic waste at a component ratio of 42.5: 42.5: 15.

In the proposed method, the process is carried out at a temperature of 40.0 ± 1 ° C.

In our case, we use the residual duckweed biomass after the extraction of valuable components, which significantly reduces the cost of biogas production and solves the issue of waste disposal.

The experiment was carried out on laboratory biogas installations (digesters) with a capacity of 3 L glass vessels, equipped with a thermostatting system, temperature sensors, stirring devices, a pH meter, a feed system, a system for removing fermented residue, a gas discharge system and a tank for biogas accumulation. To create anaerobic conditions, the reactor was purged with nitrogen before loading. Throughout the entire period of fermentation, the temperature in the digesters was maintained at the level of 36.5 ± 1; 40.0 ± 1 and 55 ± 1 ° C. The initial pH was 7.6 ± 2. The experiment lasted 30 days. Organic waste was used as a co-substrate, activated sludge was used as an inoculant, and the residual duckweed biomass was used as a raw material for anaerobic digestion. Residual biomass consists of cellulose (35-50%), lignin (14-20%), proteins (28-38%) and hemicellulose (23-35%), which increases the amount of biogas produced.

Duckweed samples weighing 15-16 g each were placed in laboratory biogas plants (digesters), then 2 liters of inoculum and organic waste were added in different proportions.

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To check the quality of the inoculum, reference samples were prepared; for this, 0.64 g of microcrystalline cellulose (C6H10O5) was added to glass bottles, into which 200 ml of inoculum were previously poured.

To determine the amount of methane (%) in the biogas, the collected gas was analyzed on a gas chromatograph (HP 6890 GC System) with a cathetometer as a thermal conductivity detector.

Table 1

The results of the study with the content of the mixture (residual biomass of duckweed, organic waste) at a temperature of 36.5 ± 1 ° C (the yield of biogas and pure methane was recalculated to normal conditions ___________________ T = 273.15 K, P = 1013 hPa) ___________________

Composition of the mixture for anaerobic digestion Biogas yield, ml per 1 g of mixture Methane concentration,% Yield of PURE methane, ml per 1 g of mixture Residual biomass of duckweed,% Organic waste,% 3% aqueous solution of activated sludge,% 85 0 fifteen 640 fifty 320 67.5 17.5 fifteen 670 52 335 42.5 42.5 fifteen 700 58 350 17.5 67.5 fifteen 684 55 342 0 85 fifteen 640 fifty 320

The optimal ratio of the residual biomass of duckweed, organic waste, activated sludge (3%) 42.5: 42.5: 15 makes it possible to obtain 700 ml of biogas and 350 ml of methane at a temperature of 36.5 ± 1 ° C.

table 2

The results of the study with different ratios of the residual biomass of duckweed and organic waste at a temperature of 40.0 ± 1 ° C (the yield of biogas and pure methane was recalculated to normal conditions _____________________ T = 273.15 K, P = 1013hPa) ____________________

The composition of the mixture for anaerobic Biogas output, Concentration Outlet clean fermentation ml per 1 g of mixture 730 methane,% 52 methane, ml per 1 g of mixture 380 Residual biomass of duckweed,% 85 Organic waste,% 0 3% aqueous solution of activated sludge,% fifteen 67.5 17.5 fifteen 750 54 405 42.5 42.5 fifteen 800 61 488 17.5 67.5 fifteen 780 59 460 0 85 fifteen 710 53 376

The optimal ratio of the residual biomass of duckweed, organic waste and activated sludge (3%) 42.5: 42.5: 15 makes it possible to obtain 800 ml of biogas and 488 ml of methane at a temperature of 40.0 ± 1 ° C.

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Table 3

The results of the study with different ratios of the residual biomass of duckweed and organic waste at a temperature of 55.0 ± 1 (the yield of biogas and pure methane was recalculated to normal conditions _________________________ T = 273.15 K, P = 1013 hPa) ____________________

Composition of the mixture for anaerobic digestion Biogas yield, ml per 1 g of mixture Methane concentration,% Pure methane yield, ml per 1 g mixture Residual biomass of duckweed,% Organic waste,% 3% aqueous solution of activated sludge,% 85 0 fifteen 740 51 377 67.5 17.5 fifteen 760 55 418 42.5 42.5 fifteen 810 60 486 17.5 67.5 fifteen 790 57 450 0 85 fifteen 745 51 378

The optimal ratio of the residual biomass of duckweed, organic waste and activated sludge (3%) 42.5: 42.5: 15 makes it possible to obtain 810 ml of biogas and 486 ml of methane at a temperature of 55.0 ± 1 ° C.

Table 4

Influence of temperature on the yield of biogas and methane during anaerobic digestion of the residual biomass of duckweed, organic waste and activated sludge (3%) in the ratio 42.5: 42.5: 15

Т, ° C Biogas yield, ml per 1 g of mixture Methane concentration,% Pure methane yield, ml per 1 g of mixture 36.5 ± 1 700 58 350 40.0 ± 1 800 61 488 55.0 ± 1 810 60 486

From table. 4 it can be seen that as the temperature rises, the quantity and quality of biogas increases, and the hygienization of organic waste is also achieved. In addition, the kinetics of the process is improved, i.e. the stable methanogenic phase is reached on average 2-3 days earlier. However, the subsequent increase in temperature from 40 ± 1 to 55 ± 1 ° C insignificantly affects the amount and composition of biogas and, thus, is economically unfeasible. Therefore, we choose the optimal temperature of 40 ± 1 ° C.

Claims (2)

CLAIM 1. A method for producing biogas from organic waste, characterized in that a 3% solution of activated sludge and residual duckweed biomass are added to organic waste at a ratio of components 42.5: 42; 5: 15. 2. The method according to claim 1, characterized in that the process is carried out at a temperature of 40.0 ± 1 ° C.