Co-Digestion with Complete Biogas Processing ZEMKA

Type of Services Provided:

• Development of the tender documents (turnkey construction)
• Tender strategy and negotiations support
• Construction supervision
• Plant commissioning, operational start-up inspections and support
• Revision of basic design and cost-optimisation

Detailed Description of Project:

The Salzburg Plc for Energy, Transport and Telecommunication and the ZEMKA Central Waste Sludge Recycling Facilities Co Ltd have decided to build an organic waste and sewage sludge treatment plant with biogas generation and supporting facilities in Zell at the Lake Side, Austria, for sanitation services within the province.
The designed capacity is for a total of 18,000 t/a organic waste, of them:

• 8,000 t/a organic waste from house collection (biowaste),
• 2,500 t/a kitchen waste and food waste,
• 2,000 t/a grease separator contents,
• 4,500 t/a sewage sludge and
• 1,000 t/a other liquid, organic waste.

In the co-digestion facility, biogas will be produced from the delivered substrates, to be fed as partially pre-treated fuel into a combined heat and power plant, in order to supply a wellness bath with gas, power and district heating. Or, as preferential solution, it shall be fed into the natural gas net of the Salzburg Plc after treatment in a gas complete processing plant.

The Prof. Dr. Dr. K. U. Rudolph Co Ltd was assigned to revise the process engineering (pre-design) and to structurise and steer a two-stage tender process, with pre-qualification and post-negotiations among preferred bidders for turnkey-plant construction of the biogas facility and full gas purification. The subsequent permission to build and operate these facilities shall be awarded in compliance with standards and procedures according to the Austrian waste economy law AWG 2002 (IPPC), comparable to the German BImSchG.

Organic waste from different sources are collected separately and delivered separately to the plant. As far as necessary, an additional separation of harmful particles and minerals (sand) is realised in a mechanical stage for pre-treatment. The pre-treated material is suspended, mixed and buffered in a storage tank to realise a continuous inflow into the fermenter (biological reactor). The effluent of the fermenter is discharged into a substrate storage tank for post-fermentation. This tank is a multi-purpose unit serving additionally as gas storage tank. The residuals from the fermentation process are dewatered and dried, or they are composted together with organic waste from households in the existing composting building, and finally the organic residuals are incinerated.

Regarding the heat energy, the facility can be optimised among others by the use of the waste heat from the existing composting building, the solar heat for the drying of the fermentation residuals, solar panels to be mounted (optionally) on the roof of the neighbouring composting building, as well as by utilisation of the low concentrated gas produced during the methane-enrichment process.