Biogas

GAS YIELD INCREASE

The biogas yield will increase with Biocept.

Biogas production with bioCEPT

The figures and percentages used in the following examples are hypothetical, and are only meant to explain the logic behind the yield improvements achieved by introducing CEPT® treatment to a conventional biogas production process. In order to measure the improvement in gas exchange when using CEPT® treatment for a given substrate, the data for the gas exchange must first be measured without CEPT® treatment. The following figures are hypothetical examples showing the benefits of using CEPT® treatment in the biogas production process. If all organic material in a substrate is converted into biogas, then this would be stated as “100%” in the image below. The actual yield of a given substrate depends on many factors. Reactor temperature and hold times are important factors.

60% av det totala organiska materialet omvandlas till biogas. 33% ökning med CEPT®. 20% återstår. �

60% of the total organic material are converted into biogas. A 33% increase using CEPT®. 20% remain.

This figure shows an example of a hypothetical substrate in which 60% of the organic matter are converted into biogas in a conventional biogas process. This is, in other words, a substrate that is difficult to rot. By processing the substrate with CEPT®, the amount of organic material converted into biogas has increased to 80%, equaling a 33% increase when compared with the conventional process. This can be compared with the next example as represented in the figure below.

80% av det totala organiska materialet omvandlas till biogas CEPT® Återstår

80% of the total organic material are converted into biogas. CEPT® 10%. 10% remain.

In this figure, the substrate is significantly easier to convert into biogas; 80% of the organic matter is converted into biogas in the conventional biogas process. By introducing CEPT ® treatment, the conversion is increased to 90%, equalling an increase of 12.5%.

In summation, the process efficiency of a CEPT® treatment is strongly related to the substrate used for biogas production. If the material is hard to digest, the potential of the CEPT ® treatment will increase. If the material is easily digestible (in cases where 80%-90% are converted using the conventional process), there will be less room for improvement through CEPT® usage.

By this logic, a CEPT® treatment is best suited for processes that use substrates that are naturally difficult to digest for the fermentative bacteria. These substances include most fibrous plant tissues, some types of animal tissues and in cases where the substrate contains a microorganism mass binding a lot of water and nutrients which, without a CEPT® treatment, would have passed through the digestion process unscathed.

SHORTER REACTOR HOLD TIMES

Methane production speed

CEPT ® treatment improves the biogas production process in yet another way! As presented above, it increases the total methane yield, however a CEPT ® treatment can also improve the production speed.

Another example will be used to explain why this improvement differs from the increased gas yield.

A typical methane production rate over time is shown in the below graph. The curve in the figure represents a conventional production, where the initial gas exchange is very high. Speed flattens out then the fermentative bacteria can no longer find any organic material to convert into biogas. When this happens, the substrate should be replaced in the biogas reactor, because the production speed is too low to be profitable, however there is still a considerable amount of organic material in the substrate.

Figur 1. Underlaget omvandlas till metan över 60 dagar. Efter 30 dagar materialet ersätts i biogasreaktorn, eftersom metanproduktionstakten är för låg för att vara lönsam.

Figure 1. The material is converted into methane during the course of 60 days. After 30 days, the material in the biogas reactor is replaced due to the methane production rate being too low to be profitable.

Gas production speed will increase by introducing CEPT® treatment at the facility. This is because the nutrients released from within the cells would be difficult to break down without the CEPT® treatment. Thus, the production curve will change as shown in the figure below. The initial gas production is greatly increased and a larger part of the total organic material is converted quicker compared with conventional biogas production.

Figur 2. Den initiala gasproduktion ökas genom att introducera en CEPT® behandling till processen. Området A är den volym gas som produceras som en ökning mot konventionell biogasproduktion. Denna volym är exakt densamma som den som representeras av B, eftersom inget organiskt materia tillsättes i CEPT® processen.

Figure 2. The initial gas production is increased by introducing a CEPT® treatment into the process. Area A equals the gas volume increase produced in comparison to using conventional biogas production.

The time interval for when gas production has been reduced to the point where the substrate should be replaced in the biogas reactor, comes much earlier with CEPT® treatment. An increase in the production of methane at the beginning of the process allows for a shorter hold time in the reactor, where the much larger volume of gas produced improves both the yield and production speed. The hold time reduction from 30 days to 25 allows for an estimated 15% increase of the amount of substrate a biogas plant can process.

NEW SUBSTRATES

CEPT substrate composition

The materials suitable for CEPT® treatment equal the traditionally hard-to-rot substrates (substrates with long hold times in the reactor). These include plant material that contain a lot of fiber and other indigestible structures. Materials with very high nutritional value embedded inside the cells and cells which have a microbiologically stable outer shell are all excellent for CEPT® treatment. The following table summarizes the various examples of materials and the potential increase using CEPT ® treatment.

Tabell 1. beräknad ökning av biogasproduktion efter förbehandling med CEPT®. Dessa siffror är prognoser baserade på tidigare erfarenheter och värderingar från litteraturen.

Table 1. Estimated increase in biogas production after a pretreatment using CEPT ®. These figures are projections based on past experiences and literature values.

Table 1. Estimated increase in biogas production after a pretreatment using CEPT ®. These figures are projections based on past experiences and literature values.

The substrate composition is crucial for the effectiveness of a CEPT® treatment. There are no concrete results or data for different types of material, however there is a set of guidelines regarding the substrates most suitable for CEPT ® treatment.

1. Cell size: The most dominant factor in the assessment of treatment effectiveness is cell size; this is the most important factor when setting treatment parameters. The threshold voltage to achieve a rupture in the cell is about 1V. Smaller cells (bacteria) require increased voltage in order to achieve the burst, and larger cells (plant) require less. The voltage can be adjusted to get the best possible cell bursting for the cell sizes most common in the current substrate.

2. Cell type: regarding the distinction between plant, animal and bacterial cells, the most important characteristic is the size of the cell. Generally, plant cells are larger than animal cells, which in turn are larger than germ cells. Different types of cells have different sizes; the rupture of plant cells generally requires lower voltage than animal cells. Germ cells require the highest voltage. Cells with a cell wall keep its morphological form, whereas in cells without a cell wall, the cell membrane collapses completely.

3. Tissue structure: Substrates containing large amounts of tissue normally difficult to degenerate, i.e. cellulose-rich materials or other tissues in which cells are embedded deep within the tissue, can be broken down when treated with CEPT®. The fermentative bacteria can not only attack the cells from within, but also begin the degradation of the cells which would otherwise be embedded deep within the tissue.

4. Cell contents: cells that contain a lot of sugar and other high energy and easily digested compounds, are released into the surrounding medium when treated with CEPT®, helping to greatly speed up the fermentation. The scope for improvement is very small when the substrate already has excellent methane producing potential, such as substrates consisting of lots of fat and oil. Cells with little or no intracellular nutrition would not speed up the rot process significantly.

PROFITABLITY INCREASE!

After an evaluation of the pilot study, bioCEPT has demonstrated a significant impact on profitability. The pilot study of the technology has provided us with the results listed below.

Savings and profit Energy gain Financials
Gas yield increase 2.1 – 2.4 GWh SEK 1-1.2 Million
Continuous process – capacity usage improvement 3.15 – 3.6 GWh SEK 1,5 – 1,8 Million
Faster rot 3.15 – 3.6 GWh SEK 1,5 – 1,8 Million
Potential total 9.5-10.7 GWh SEK 4.55 – 5.35 Million

 

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