Which biogas projects are the most promising in Ukraine?

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The platform GetMarket together with the Ecodevelop company, which sells turnkey biogas systems for the utilization of organic waste with the conversion of biogas into electricity and heat, as well as organic fertilizers, begins a series of publications on Ukrainian bioenergy, prospects and issues, which today prevent Ukraine from using full  biogas potential.

In the first article technical experts of Ecodevelop answer the questions on criteria for viable biogas projects in Ukraine.

First of all, we need to understand that this issue is quite complex and multifaceted. Consider the three most important, according to Ecodevelop, criteria for the viability of the biogas project: the potential of biogas output from 1 ton of substrate, the availability and accessibility of the substrate, and the technological ease of obtaining biogas (low construction cost).

Biogas yield potential from 1 ton of substrate

It is well known that biogas yield depends on the composition of the substrate, its bioavailability and production technology. 

Every provider of technological solutions sets its own biogas yield, but we will not dwell on this. However, it is worth considering the potential of biogas output from each individual substrate, namely the amount of biogas that can be obtained under conditions of almost infinite fermentation of the substrate under stable conditions. Of course, in real conditions this figure is very rarely achieved (or almost never) due to the economic inexpediency of such a long process, but the figure of 60-95% is achievable and economically justified. 

The table below lists potential substrates for biogas production.

Potential substrates for biogas production

Substrate

Dry matter (SR),%

Dry organic matter (COP),% CF

Specific yield of biogas, m3/ t COP

Specific yield of biogas, m3/ t

Industrial waste

Beer shot

25.0

70.0

450 0

78.8

Brewer's yeast

20.0

75.0

400.0

60.0

Grainbard

6.0

83.0

430.0

21.4

Potato bard

6.0

85.0

400.0

20.4

peel potatoes

20 0

95.0

600.0

114.0

Potato juice

3.7

70.0

940.0

24.3

Starch

83.6

95.0

700.0

555.9

Mezga

13.0

90.0

650.0

76, 1

Pressed

22.0

95.0

250.0

52.3

Molasses

80.0

85.0

360.0

cake244.8

Apple bard

25.0

85.0

660.0

140.3

Whey curd

8.0

92.0

700, 0

51,5

Fuz oil

30,0

95,0

900,0

256,5

Waste from sewage treatment plants, MSW

Sediment of primary settlers

3,5

70,0

450,0

11,0

Sediment of secondary settlers

3,5

70,0

200,0

4.9

Aerobic excess sludge

3.5

80.0

300.0

8.4

Flotation sludge

3.5

80.0

900.0

25.2

Fat from grease traps

25.0

95.0

1000.0

237.5

Solid household waste (organic component)

20.0

90.0

700.0 Edible

126.0

fat

42.0

99.0

900.0

374.2

Waste fe Farms

Pig manure

3.0

85.0

425.0

10.8

Cattle manure

25.0

80.0

350.0

70.0

Chicken manure

24.0

85.0

425.0

86.7

Agricultural substrates

Maize silage

32 0

95.0

700.0

212.8

Straw

30.0

90.0

600.0

162.0

Silo herbal

30.0

89.0

550.0

146.9

Sugar

23.0

90.0

800.0

165 , 6

Fodder beet

12.0

75.0

620.0

55.8

Pulp

28.0

94.0

680.0

179.0

It should be clearly understood that biogas can be produced exclusively from dry organic matter (COP) and not from water. Also, the potential of biogas output per ton of COP is different for each of the substrates, because they differ in the percentage of proteins, fats and fiber, which are the source of biogas.

Returning to the output of biogas from the crude substrate (ie natural moisture), the following can be noted: starch (556 m3/ t), edible fat (374 m3/ t) and oil fuz (257 m3/ t). However, any of them has a number of disadvantages. The first is not a waste, so it is difficult to imagine large enough volumes to use it as a substrate for the biogas complex. While the latter two are available in Ukraine in large quantities, their use is complex in terms of technology and, consequently, more expensive. This is due to the need to maintain higher fermentation temperatures and pre-treatment. 

On the other hand, the least attractive in this case are the various wastes of municipal treatment plants (sedimentation tanks, excess sludge from the aeration tank) only because of their significant degree of dilution (sometimes up to 99%). But this problem is easily solved by concentrating the sludge to a level of at least 5% dry matter, and sometimes up to 25%. However, in this case, the cost of the project is higher than usual. 

Nevertheless, such projects are quite promising, as they address the issue of liquid waste disposal. Today, they are extremely relevant and in line with the European trend of environmental safety of production. These projects often receive government support and funding, despite these shortcomings.

Thus, the attractiveness of the substrate does not always mean economic feasibility. Now let us consider other criteria.

Availability of substrate

An extremely important factor is the availability of raw materials. 

Based on the considerable experience of Ecodevelop, it can be argued that only projects with their own source of raw materials can claim profitability and stability in the Ukrainian reality. 

The biogas complex cannot be suspended for a while. It is a whole biological process that requires constant monitoring. Starting from a stable and uniform load on the organic and ending with the planned periodic unloading of the fermented substrate from the storage tanks, because they also have a limited volume and can not take the substrate indefinitely. 

Any fluctuations in the composition of the substrate lead to inhibition of the process of methanogenesis - a decrease in the specific yield of biogas. Sharp fluctuations, even in the qualitatively better direction in terms of organic composition can lead to a complete shutdown of the station. 

In the case of using a non-native substrate, it is extremely difficult to control its composition and ensure the absence of impurities that can critically affect the activity of anaerobic bacteria that produce biogas.

Another important problem is the delivery of the substrate. Leverage of more than 30 km leads to a significant reduction in the profitability of the biogas complex. 

Technological simplicity of biogas production (low construction cost)

The last important criterion is technological simplicity of execution. Most substrates include impurities that require additional effects. 

For example, when using too dry substrates, such as straw, without prior hydrolysis, there is a high risk of crusting on the surface of the substrate in the reactor, which in turn leads to a rapid release of biogas after reaching a critical pressure. This is a potential emergency. Other substrates require additional measures to reduce the concentration of hydrogen sulfide in biogas. While the high hydrogen sulfide content is critical for the operation of cogenerators or biogas combustion boilers. All these factors lead to an increase in capital and operating costs.

From the experience of Ecodevelop specialists, the most technologically simple projects are biogas projects based on the use of silage, which has a high yield of biogas and does not require additional processing at all stages of fermentation. 

Moreover, such projects are especially successful if the construction of a biogas complex on the basis of an agricultural holding, which has the ability to grow silage and use the fermented substrate (digestate) as an organic fertilizer. Such projects pay for themselves in 3-5 years and are very profitable.

Summarizing all the above arguments, the uniquely correct solution simply does not exist. And therefore, each biogas project should be considered individually.