Biogas plant feasibility study
Bad Honnef AG (BHAG) is an energy supply company with electricity, natural gas and water divisions. BHAG was considering building a biogas plant in a recently built business park within its supply area and commissioned the bifa environmental institute to carry out a feasibility study.
The objective was to work up the principles for Bad Honnef AG, on the basis of which decisions could be made in the relevant committees as to whether to build a biogas plant or not.
In particular, the following aspects were examined
- Location suitability,
- Substrate procurement,
- Plant size and technology, including gas conditioning and feed-in,
- Basic legal conditions and
- Economic efficiency
The infrastructure at the location would in principle have been suitable for the erection and operation of a biogas plant. This includes a favourable transport position for the supply of the plant with substrates as well as the immediate proximity of a natural gas pipe.
From an approval legislation point of view the proximity of the plant to residential developments was classified as being problematic and from an economic point of view, the difficulty in identifying suitable heat purchasers in the area surrounding the planned plant. In addition, competitive disadvantages could result due to the relatively high investment requirement for purchase of the necessary land compared to privileged agricultural biogas plants, which are erected on low-price land.
With regard to the choice of substrates, research also showed that the procurement of relevant substrate quantities – not only biowaste but also NaWaRo (renewable resources) – would have been difficult. Reliable statements on the yield of biowastes and on possible cooperation with the waste management representatives were not possible.
Equally, it was found that relevant quantities of residual production materials from industry and trade or agriculture and forestry are not available. Farmers in the region showed interest, however, they pointed out that the substrate prices offered to them must be based on market demand. The plant size was dimensioned according to the available substrate quantities in conjunction with threshold values in the immission control legislation.
Three process options were examined
- Dry fermentation of biowastes in the box method
- Dry fermentation of NaWaRo in the box method
- Wet fermentation of NaWaRo in the plug flow process
The economic results are highly dependent on the actual biogas formation potential of the substrates used or rather their quality. These fluctuate naturally in the case biowaste substrates more than with agriculturally produced products such as maize or grass silage. Possible fluctuations were therefore taken into account in the evaluation of the economic results. Based on bifa's own experience, before starting possible approval procedures, a great deal of attention should be placed on trust-building PR work.
This not only applies to the construction of a NaWaRo plant but also to a biowaste fermentation plant.Therefore, before further specific planning steps are taken, contractual or rather binding securing of noteworthy substrate quantities over several years was recommended. In addition, parallel options for the sale of relevant heat quantities should be examined.
If the efforts to secure substrates and the search for heat sinks should prove to be unsuccessful, the advice would be not to build a biogas plant in the business park for economic reasons.