The Bio-Energy Center (BEZ) of infra fürth gmbh

Author: Tobias Beck - Rudolf Hofmann, infra fürth GmbH (as of May 2015)

1. General information

The infra fürth gmbh sees itself as an innovative and environmentally friendly company and attaches very great importance to a sustainable concept for regenerative energy supply. Therefore, infra has already started in 2006 by a feasibility analysis with the preliminary planning of a biogas plant and decided in October 2010 with the groundbreaking ceremony the implementation. Already in December 2011, the first gas was produced and the BEZ could thus officially start operation. With this project, infra intends to replace a part (approx. 4 to 6%) of the natural gas volume required annually with the bio natural gas produced in the biogas plant. This reduces the dependence on natural gas imports and shifts the added value to the region. For nature and the environment, the construction of the BEZ means a saving in primary energy use and thus a reduction in CO2 emissions. According to calculations, this will save approx. 17,400 t of CO2. As a result, infra can offer a wider range of products, e.g. 100% green gas (biogas), and the purchase of substrates from the region is carried out according to the motto "from the region for the region".

In addition to technical and economic feasibility, the dimensioning of the plant was of course also adapted to the local conditions at the site. In this context, particular attention was paid to ensuring a high level of compatibility with the plant's surroundings, especially with regard to substrate supply. For examination purposes, expert opinions for noise, odor and transport emissions have been obtained as part of the approval procedures.

2. Plant concept and operating principle

The BEZ has been built on a total area of approximately 72,000 m². The area provides space for the two-line plant and for the storage of substrates directly on site. The biogas is produced by a highly efficient wet fermentation process in several steps and is upgraded to natural gas quality in the subsequent gas treatment plant. The fermented substrates are first deposited in the digestate storage facilities. These so-called fermentation residues are rich in nutrients and are used as high-quality fertilizer. The fermentation residues are collected by farmers and spread on the fields again.

In the supply contract, BMLG undertakes not to supply or process any plants or plant parts that have been genetically modified. The catchment area for the substrates extends to approx. 15 km around the plant for ecological as well as economic reasons. Depending on availability, the raw material supply will be supplemented with other substrates, such as flowering plant mixtures, flowering silphia, millet and giant wheat grasses.

3. Plant size data (planning data)

The amount of gas extracted corresponds to e.g. when used in CHPs, an amount of electricity for about 6,300 households and an amount of heat for up to 2,000 households.

4. Overall energy balance and environmental sustainability

In order to evaluate the environmental effects, a consideration of CO2- emissions was performed. The calculations result in a positive overall balance of the Bio-Energy Center. In the German electricity and heat mix, the production of the same amount of electricity and heat that the Bio-Energie-Zentrum also produces in the equivalent results in a total of approx. 22,000 t CO2 (electricity 13,000 t CO2/ heat 9,000 t CO2). The total CO2 emissions of the Bio-Energy Center, from the sowing of the plants to the spreading of the fermentation residues (incl. transport), amount to only approx. 4,600 t CO2. This corresponds to a CO2 saving of about 17,400 t CO2 or about 80% compared to conventional production.

5. Challenges Bio-Energy

The challenges of bio-energy projects are multifaceted and range from initial considerations, project planning, implementation and subsequent operation of the plants. These begin with the search for suitable locations, as attention must be paid to different boundary conditions, such as the development with gas and electricity.  Also adjacent residential developments or the binding to public traffic routes are usually important decision criteria.

In the planning phase further challenges must be mastered then, which are very far-reaching particularly with the planning of a biological gas facility. Apart from a suitable property with sufficient surface, a traffic-favorable binding and the development with river, water and gas numerous appraisals and statements for the permission documents are to be caught up. These reach from appraisals over the future traffic load, over smell appraisals to the dispersion of the smell of the cut surface of the driving silos up to appraisals over the cavity content of the asphalt surfaces of the driving silo plant and the  durably tight connections to the driving silo walls.

Parallel to the permission for immission control (BImSchG) and water right also the production of the development plan with the definition of the editions and the necessary compensation areas takes place. Calculations are made for sealed areas and the impact on nature is evaluated. Based on these results, it is determined which compensatory measures are required, such as ecological upgrading of areas or even paying into eco-accounts.

When planning the Bio-Energy Center, it was also necessary to plan the drainage of the accumulating rainwater into a nearby stream, as a sewer was not available for discharge.

One of the most important points in the preliminary planning, however, is the conclusion of supply contracts with the farmers or with the association of a supply community, such as the BMLG biomass supply company at infra fürth. The biomass supply company is made up of equal shares of shareholders from two machinery and farm support associations and one shareholder from the producer association for quality grain. It takes over the raw material acquisition, organizes the harvests and the fermentation residue collection and takes over the transport and the Einilierung of the raw materials on the plant.

Further challenges arise also in the building phase and/or after the completion. The biogas plant is accepted by various authorities and experts. For biogas plants that can store more than 10,000 kg of biogas at the plant and feed the upgraded bio natural gas into a natural gas network, there are additional obligations and requirements.

High safety requirements for biogas plants

Generally, all biogas plants must have a fire protection concept or fire plan and an explosion protection document that considers the potential hazards at the plant. Furthermore, such plants have to be approved by an expert for water law or VAwS (Ordinance on Substances Hazardous to Water) according to the Ordinance on Industrial Safety and Health (BetrSichV) as well as by the responsible approval authority. Infra also proved to the Fürth District Office as the approval authority that the asphalt used in the driving silos was made with acid-resistant aggregates and that the maximum void content does not exceed 3% in the installed state. This is due to the fact that the leachate is classified as hazardous to water (WGK 1, weakly hazardous to water) and thus the tightness of the driving silos is urgently required. Likewise also the tightness of the connection of the transition of the asphalt of the driving silo plant on the concrete walls was accomplished in a complex procedure and proved to the district administration office in form of an expert opinion.

For biogas plants, which fall under the accident regulation (> 10,000 kg biogas storage capacity) must be provided additionally a concept for the prevention of accidents inclusive a safety management. Here, the hazard potentials of the substances used are discussed and a plant-specific risk analysis with measures for the prevention of incidents is drawn up. In a further step still the plant and safety management are described.

If the utilization of the biogas does not take place, as with most plants, over a Blockheizkraftwerk (BHKW), but over a gas processing, with which the biogas is prepared on natural gas quality, then the plant must be accepted additionally still in accordance with energy industry law (EnWG).

In the last phase of the project, thus in the enterprise of the plant, all acceptances, editions and provided documents are taken up again. Depending on the type of approval, recurring inspections must be carried out. As an example, the explosion protection document, the incident concept and also the fire department plan must be checked annually to ensure that they are up to date. The recurring test in accordance with operational safety, on the other hand, must be carried out every 3 years by an expert.

The generation of electricity, heat and gas from renewable sources is subject to strong seasonal fluctuations. In particular, electricity generation from the sun and wind is very dependent on the current weather and very difficult to forecast.

In contrast, the generation of electricity or gas from renewable raw materials, such as corn, grass and whole plant silage (GPS), can be produced continuously or regulated. However, the growth of the raw materials or the harvests are very dependent on the prevailing weather and accordingly fluctuate greatly each year.

These fluctuations and imponderables must already be taken into account in the preliminary planning and preparation of the profitability analysis and be supplemented with a certain safety margin.

6. Value chain

Although there are a number of challenges and constraints in the planning, construction and operation of bio-energy plants, infra sees the investment in bio-energy as an investment for the future and an improvement for the region.

Specially in the field of bio-energy in the form of biogas, the value chain extends from agriculture to the sale of the produced bio-natural gas, green electricity and renewable district heating in the urban area and district of Fürth to the image gain for all involved.

For agriculture, the supply of a biogas plant with raw materials means another mainstay for the marketing of crops in the region at an  economic price with long-term security. Thus, the operation of a biogas plant can strengthen local agriculture and forestry. In addition, short nutrient cycles are established at infra fürth through the return transport of the fermentation residue to the arable land, which means that industrially produced fertilizer can largely be dispensed with and thus the added value also remains in the region. Other diverse points are also agreed in the raw material supply contracts, such as crop rotation with a maximum of 1/3 corn cultivation and the renunciation of genetically modified seeds. This ensures sustainability and good agricultural practice.

In addition to the biogas upgrading and feed-in plant, infra also operates the raw biogas generation plant. Thus the entire handling from the supply of the raw materials up to the marketing of the prepared bio natural gas remains in the enterprise, which is not only positive for the creation of value chain, but besides also during the building and enterprise of the plant possible interfaces reduces and thus again time and risk saves. The processed bio natural gas is then used to generate electricity in infra's own combined heat and power plants with complete heat extraction, among other things. In addition to the electricity generated, which is constantly remunerated over 20 years in accordance with the Renewable Energy Sources Act (EEG), the heat produced is also fully utilized and sold as district heating. This also offers district heating customers an advantage, as the use of renewable sources reduces the primary energy factor, which in turn means cost savings in upcoming renovations.

Further bio natural gas volumes will be added to the portfolio and brokered to customers who also operate combined heat and power plants, or want to generate heat from renewable sources.

7. Additional value creation

Since April 1, 2015, EEG plants in the market premium model must demonstrate remote controllability by third parties in order to receive the market premium from the grid operator. The amount of the management premium for remotely controllable plants in 2015 is 0.40 ct/kWh for electricity generated from wind energy and solar radiation energy, and 0.20 ct/ kWh for electricity generated from hydropower, landfill gas, sewage gas, mine gas, biomass, and geothermal energy.

For controllable electricity generation plants, there is the option to participate in the balancing energy market. For a stable grid, it is important that the amount of electricity provided corresponds to the amount of electricity consumed. If the transmission system operator detects deviations, it orders negative or positive control or balancing energy from the participants in the control energy market accordingly. Prequalification is required for participation in the balancing energy market. Primary and secondary control power as well as minute reserve can be offered. If the bid is accepted, the provision of the control energy tendered for this purpose is remunerated accordingly.