Автор - | 03.02.2019

Humanity is constantly working to create alternative energy, which will reduce dependence on non-renewable resources and reduce the negative impact on the environment. However, even today more than 90% of the world’s energy consumption is tied to the use of coal, oil, and traditional gas.

One of the promising areas is the production of biogas from renewable sources. It will provide humanity with alternative energy, which in the future will reduce the cost of producing one or another product. One of the most promising, rational methods for producing this type of fuel is a process called methane fermentation.

He is described in detail in his work “The stimulating effect of Amaranth Amaranth Cruentus dry phytomass on biomethanogenesis in difficult-to-fermentable substrates”, worked on by A.Z. Mindubaev, S.T. Minzanova, E.V. Skvortsov, V.F. Mironov, V. V. Zobov, F. Yu. Akhmadullina, L. G. Mironova, D. E. Belostotsky, A. I. Konovalov. The researchers are employees of the Institute of Organic and Physical Chemistry named after A.E. Arbuzov Kazan Scientific Center of the Russian Academy of Sciences.

We present excerpts from this work, which will make it possible to understand how amaranth is a versatile, useful culture. After all, previously we have repeatedly written about the fact that the plant has a large number of nutrients, vitamins and trace elements, so that amaranth is used in the production of:

  • food products;
  • pharmacological products;
  • cosmetic products.

However, new studies allow the use of plant phytomass for biogas synthesis – an alternative source of energy.

Briefly about biogas and how to obtain it
It has been established that in nature an independent synthesis of biogas takes place – with the decomposition of organic elements:

  • at the bottom of reservoirs;
  • in the ground;
  • in the digestive tract of animals.

Scientists say that the production of biogas from various wastes will not only provide an alternative source of fuel, but also solve a number of environmental problems. In particular, it is quite possible to adjust the synthesis of biogas from:

  • food industry waste;
  • agricultural waste;
  • garbage;
  • drains

That is, it is not only about obtaining ecological fuel, but also the preservation of the environment, which will suffer less from the accumulation of debris, waste, wastewater.

Modern biogas production technologies
At the moment, the production of biogas is only considered as a promising direction, but it is still a complex process that requires substantial financial costs.

If you look at the dynamics of the development of the direction, then in Sweden back in 1991 at the governmental level over 100 million kroons were allocated for conducting case studies, the production of gas for vehicles. It is clear that not all countries have sufficient resources to conduct such research.

However, the possibility of using plant biomass to produce gas is increasingly being considered – this is due to the fact that such a mass is relatively inexpensive. Therefore, the final costs (respectively, the cost of biogas) will be minimal. It is for this reason that the creation of technologies involving the use of such green additives, is attracting increasing interest from scientists. The authors decided to explore the possibility of using phytomass amaranth crimson.

Researchers first analyzed the effect of amaranth on methanogenesis – that is, on the formation of biogas.

It is noted that amaranth is a really promising crop, which allows to receive up to 600 centners of green mass from each hectare of the sown area. And it is even in difficult climatic conditions. And on good soils and under favorable weather conditions, it is possible to obtain up to 2000 centners of green mass from each hectare of the sown area.

Researchers note that it is prohibited to feed cattle with pure amaranth. Because it stimulates the activity of the methanogenic microflora of the rumen. Due to this effect, the content in the amaranth of a large amount of vegetable protein.

However, given this fact, the scientists were the first to decide to use amaranth to increase the efficiency of biogas production by stimulating methanogenic microflora. For this purpose, processes occurring in the rumen of ruminant animals were modeled in the laboratory.

How the research was conducted, what results were obtained and what conclusions they allow to make
During the research, scientists performed several experiments that allowed to compare these or other processes and their results.

In particular, during the first experiment, a brewer’s grain was used as a substrate to start the process of methanogenesis. It is one of the most common waste of the food industry. In the course of the experiment, two reactors were simultaneously operated simultaneously. The volume of brewers in both cases differed (as their characteristics differed), but the gas yield in both cases was extremely low.

In particular, in the control reactor were used:

  • 30 grams of brewer’s grains (moisture content 72%);
  • 10 g of scar content;
  • 60.0 ml of tap water.

In a pilot experiment, the mixture was incubated:

  • 15 grams of beer grains;
  • 4.6 g dry phytomass of A. cruentus (initial moisture content not more than 10%);
  • 10 g of scar content;
  • 70.4 ml of tap water.

The substrate with amaranth allocated 44 ml of gas, and without amaranth – 26 ml. The absolute content of methane in both cases is also unacceptably low – at the level of 0.5-2%.

However, scientists note that in general, the content of amaranth allowed to significantly increase the amount of methane – for example, on day 16 its volume was 1.6%, while in the reactor without amaranth it was only 0.2%.

In addition, comparative experiments were conducted using sugar beet pulp. In the first embodiment, the following were placed in the reactor:

  • 25 g sugar beet pulp (humidity 81%);
  • 50 g of fresh content;
  • 75 ml of tap water.

In the second reactor:

  • 12.5 g beet pulp;
  • 2.75 g dry phytomass amaranth crimson;
  • 50 g of scar content;
  • 85 ml of tap water.

In general, the final biogas yield was not too large. Rather, even small. However, on the 22nd day the volume of methane in the second sample was 9.9%, and in the first (without amaranth) it was only 0.6%. On the 58th day, these figures were 4.5% (the first reactor, without amaranth) and 15.7% (the second reactor, with amaranth).

From which we can make a logical conclusion that sugar beet pulp is a more suitable food resource for methanogenic microflora in comparison with brewer’s grain, and amaranth crimson activates methane formation.

The effect of amaranth on hardly fermentable substrates
The scientists also investigated the effect of amaranth on biogas production, if traditional raw materials are used, which is ordinary manure. For this, two reactors were also used.

In a half liter vessel placed a mixture of the following ingredients:

  • 50 grams of manure;
  • 275 ml of rumen contents;
  • and as much water.

For 11 days, 30 grams of manure and the same amount of water were added to the vessel every day. As a result of the experiment, it was found that the gas yield and the total methane content during the first days were constantly decreasing. This is due to the fact that the microflora was forced to adapt to new conditions.

Up to 15 days, the gas yield and the methane content in the mixture gradually decreased. But after the 15th day, the figures began to increase. 51 days after the start of fermentation, the mixture released 150 ml of gas, which contained 60% methane. With 52 days of research, gas production productivity increased. On the 60th day, the gas output reached 550 ml per day, after which it began to decrease gradually.

The second prototype contained 96 grams of crushed dry amaranth. On the first day of the experiment, gas formation was really explosive in nature: the intense evolution of gas led to the release of the substrate from the reactor.

On the 3rd day, the gas output was 470 ml in 8 hours. After that, the gas formation began to fade out smoothly.

At the same time, the volume of methane in the gas for the phase of maximum reactor activity turned out to be rather low: on the fourth day it reached a figure of 13.5%. On the 12th day, the methane content reached 47% with a gas output of 550 ml per day. The maximum methane content (55.2%) with a gas outlet of 120 ml per day was observed on the 44th day of the experiment, after which it began to slowly decrease.

Such indicators have confirmed the rule revealed in the course of these studies. The total amount of methane in the gas grew against the general background of a decrease in the formation of gas. Moreover, it was possible to reveal that the addition of amaranth crimson in animal dung does not lead to an increase in the amount of methane, but reduces the so-called lag-phase to complete disappearance.

How does amaranth phytomass affect methanogenesis
Researchers have tried to understand exactly how phytomass amaranth crimson affects the formation of methane. To this end, they conducted a number of experiments, including the use of raw brewer’s grains, as well as sulfuric acid. And, of course, phytomass amaranth crimson.

It was found that the presence of amaranth in the substrate leads to an increase in the output of CO2. Thus, scientists were able to prove that amaranth has a stimulating effect on the acidogenic stage of methanogenesis. That is, we can conclude that amaranth is an activator of fermentation. And not only methane, but also acetate and alcohol.

Conclusion: what exactly the researchers have established
Studies have established that phytomass amaranth purple has a stimulating effect on the formation of methane. What is incredibly important when it comes to such difficultly fermentable substrates, such as brewer’s grains and beet pulp.

In addition, the presence of amaranth can significantly increase the amount of methane in biogas. When it comes to nutrient substrates, such as manure, the presence of amaranth accelerates the formation of gas. The large amount of organic nitrogen that the phytomass of amaranth contributes to the substrate does not suppress the vital activity of the methanogens.

Conducting research allowed to create a laboratory method of anaerobic processing of raw materials used for the production of biogas. Scientists have found that the best of all the studied types of raw materials for this purpose is manure to which amaranth is added.

But the growth of methanogenic microflora on more difficultly fermentable substrates – beet pulp and brewer’s grain – is at the limit of tolerance.

Final conclusions
The optimal raw material for biogas production (from the samples under study) is a mixture of manure and waste from the meat industry (cattle scar), then sugar beet pulp, and the top three – beer pellets.

However, we are interested in the effect of amaranth on biogas production. In the course of research, it was found that Amaranth purple (Amaranthus cruentus) phytomass is a stimulator of methanogenesis in difficultly fermentable substrates. Which include beer pellet and sugar beet pulp. The presence of amaranth can increase the methane content several times. If we talk about the presence of amaranth in manure, the plant stimulates the acceleration of the process of gas formation.

It has also been established that the maximum methane yield was recorded at the stages of gas generation attenuation. As scientists admit, this is most likely due to certain environmental characteristics of methanogenic bacteria.

So, the conducted studies make it clear that the use of phytomass of amaranth in biogas production is a promising direction, although it requires further research to determine the most rational method for the production of alternative fuels.

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