Biogas plant calculator for biofuels & profitability - Calculate Now

Efficient calculation in biogas plant construction

1) Basics (principle, composition, origin, use, occurrence, industry, fermenter)

Biogas plants are plants which serve the production of biomass. In addition to the end product of biogas, fertilizer is produced as a by-product in these plants. The biomass is produced in such a biogas plant through the fermentation of various organic substances. The gas that is produced can be used in many ways. It is used, for example, to generate electricity and heat or as a fuel.

It can also be used as fuel for vehicles. A biogas plant is composed of different parts. These include the fermenter (=bioreactor), the slurry store and the gas store. In the fermenter, the raw materials are converted into the end product biogas through fermentation and putrefaction processes. Biogas consists of about 40-75% methane, 25-55% carbon dioxide and 10% water vapor. In addition, biogas contains small amounts of nitrogen, hydrogen, oxygen, hydrogen sulfide and ammonia.

2) Biogas plant costs & economics (by capacity)

Accordingly, the investment costs increase depending on the size of the power, i.e., the height of the KW. However, the electricity that is fed into the power grid is remunerated and pays for itself with the investment costs.
over a period of several years. In addition to the costs of purchasing and building a plant, there are also the costs for the input materials, which also increase with the amount of KW. However, free raw materials such as liquid manure, dung or slurry can also be used as feedstock. Thus the economic efficiency is increased by a lot. As a rule, however, the costs for a plant are recovered by the product within 5 years.

One of the economic aspects of a biogas plant is the utilization of previously unused plant parts such as catch crops or even clover grass. The production of biogas can also be controlled according to demand.

3) Biogas plant investment (biogas funds) & financing (subsidies)

Biogas plants usually have the disadvantage of being very cost-intensive. For private operators it is worthwhile to finance the plants on an application. This is usually approved if certain conditions are met or if the company funding the construction also generates income with the biogas plant.

4) Biogas plants and cogeneration plants (with CHP)

At the moment, biogas is mainly used to generate heat and electricity in so-called cogeneration plants. Here, the waste heat from electricity generation is used directly where it is generated. The basic idea of a CHP is to use heat and electricity directly on site, while the electricity that is not needed is fed into the public power grid.

5) Biofuel (biogas as fuel, biodiesel, gas stations)

Biofuels can be divided into different substances. These include bioethanol, biodiesel, biogas, biomethanol, biodimehylether, biohydrogen, synthetic biofuels, vegetable oil or biobutanol. All of these fuels are derived from biomass. The use of biofuel to power vehicles is intended to contribute to climate protection, as it can significantly reduce dependence on petroleum.

A great advantage of the products of a biogas plant is that the methane (if purified) can be used as fuel for vehicles. In this case, no conversion of the vehicles is necessary (except for vegetable oil fuel, since it is very viscous), since the biodiesel can be added up to 6% to the conventional diesel, as well as the bioethanol up to 6% to the conventional gasoline.

6) Biogas as fuel for the heating system

Fuels combine with oxygen in the air through heat and light emission. Fuels are usually used in conjunction with a fuel cell. A fuel cell converts chemical energy into electrical energy under constant supply of a fuel and an oxidant. Accordingly, the fuel cell is an energy converter and not an energy storage device.

It makes sense to use biogas as a fuel, because the products of biogas plants cannot always be used on site due to the poor location of biogas plants. If the biogas is appropriately upgraded, it can be used as a fuel. Various fuel cells, such as molten carbonate fuel cells, enable high electrical efficiency with very low emissions.

The actual fuel used here is the hydrogen filtered out of the methane gas. The process of extracting the hydrogen from the methane gas takes place at very high temperatures inside these fuel cells. Due to the high temperatures, fuel cells offer the possibility to use the waste heat sensibly at the same time.

7) Feeding into the natural gas grid

The feeding of electricity into the power grid as well as the feeding of gas into the natural gas grid are regulated in Germany by certain laws (EEG Renewable Energies Act). However, the operator of a biogas plant only receives remuneration if electrical power is fed into the power grid. As soon as the product is only used thermally or is fed into the natural gas grid after purification and compression, the operator does not receive any remuneration.

8) Storage of biogas

Biogas is stored directly in the biogas plant in a designated gas storage facility. It is very important that the gas storage is hermetically sealed and that no gas can escape. Gas storage tanks are often made of plastic-coated and flexible fabrics, as the gas can expand with temperature fluctuations. This material is also very tear resistant.

9) Biogas Potential & Future Prospects

Biogas plants are very environmentally friendly (as long as they are gas-tight, since methane gas is more harmful to the environment than CO2), and the products of a biogas plant can be used in many ways (fuel, fuel for vehicles, electricity generation, heat generation). Accordingly, biomass plays a major role in sustainable energy supply.

10) Construction of a biogas plant

Many companies have specialized in the construction of biogas plants. The construction of a biogas plant can be divided into four areas:

1. the idea,
2. the legal basis and planning
3. the procedures for approval and finally
4. the commissioning of the biogas plant.

When building a biogas plant, some aspects have to be considered, which are listed in point 12. In addition, (taking into account the safety precautions mentioned in point 12) a simplified construction of the biogas plant can significantly reduce the purchase value of the plant. Care should be taken to ensure that sufficient land is available to build a biogas plant.

11) Different types of plants (according to raw materials)

Biogas plants can be distinguished by the use of different raw materials, in addition to their size and capacity. As a rule, only renewable raw materials (so-called NaWaRo) are used for biogas plants. These raw materials can be used as products from agriculture, biowaste or also liquid manure.

As already mentioned in point 2 (biogas plant costs & profitability), previously unused parts of plants can also be used as raw materials. Raw materials such as liquid manure, dung or slurry usually cost nothing and are freely available (however, they are only profitable in very large quantities). The quantities of biogas vary with the raw material used. Accordingly, the largest amount of biogas can be produced from dough and bakery industry waste.

Another very productive raw material is waste oils and fats. Other raw materials (listed in order of yield) are waste bread, molasses, vegetable fats, chicken droppings, kitchen waste, wax waste, grass silage, maize silage, green maize cuttings, bräu waste, meadow grass, beet clippings, sillage from sugar beets, whole beets, waste from potatoes, rinse waste from dairy farms, swine manure, squeezed waste from starch factory, and cow manure.

12) Errors in the design and construction of a biogas plant

To avoid mistakes in the construction of a biogas plant, some aspects should be considered.
The above-ground parts of a biogas plant must be easily accessible and extremely stable. The plant parts, which are electrically conductive, must be connected to each other, to the protective conductor and to the ground conductor, so that a potential equalization takes place.

The parts containing gas must be sufficiently protected against damage and chemical influences. The digester must also be equipped with safety devices that may change the internal pressure. Filling openings must be secured against falling in. Most importantly, all hazardous areas must be clearly marked with warning signs to reduce hazards and prevent accidents.